ANGELS Communications by Kurt Zeller

ANGELS
Aitken Network for Geologic Extraction of Lunar Samples
LANDER VEHICLE
CALIFORNIA POLYTECHNIC STATE UNIVERSITY
SAN LUIS OBISPO
2015-2016 Spacecraft Design

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Contents
1.0 Communications Subsystem........................................................................ 2
1.1 Frequency Trade Study - Kurt Zeller....................................................... 2
1.2 Communications Satellite Disposal - Kurt Zeller......................................... 7
1.3 Seismometer Data Transfer - Kurt Zeller.................................................. 9
1.4 High Gain Antenna Design - Kurt Zeller ..................................................16
1.5 Ka Band System - Kurt Zeller...............................................................30
1.6 Appendix ......................................................................................38

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1.0 COMMUNICATIONS SUBSYSTEM
1.1 FREQUENCY TRADE STUDY - KURT ZELLER
(11/20/15, updated 5/26/16)
Several frequency bands were considered to transmit the high data rate video for
the ANGELS mission. During the second quarter the data rate was reduced due to
allowed compression down to 1.6 Gbps which was kept for the remaining mission
design. It was decided that a Ka Band system would be used to transmit video,
LIDAR as well as seismometer data due to component availability, reliability, as
well as power required. An X band system was decided upon for TT&C due to its
heritage, availability, as well as power required. Although an optical
communication system appears viable near the beginning of the design process,
component availability and pointing requirements led to the decision to use a
more common RF system.
Final System Requirements
The system shall transmit:
 a minimum of 5 kbps of TT&C data for the entire mission, excluding seismometer
operations
 4.5 Mbps (LIDAR Data) during the last 2 km of descent
 1.6 Gbps during lunar operations and during ascent vehicle take-off
 seismometer data at least once per month
Introduction
Four frequency bands have been deemed feasible to communicate the required 4.5
Gbps for the Aiken Basin Mission: X, Ka, V, and optical bands. These four were selected due
to several factors including ground station availability, the 2014-2015 spacecraft design
analyses, as well as the bands used by previous lunar missions.
Although RF is the traditional method of data transfer, an optical communications link
may be beneficial in order to save power and mass on the spacecraft. Several
demonstrations have taken place indicating a high data rate transfer at very low powers.
Weather is the predominant limitation of optical communications which can be minimized by
a diversity of ground stations. Current technology requires an optical beacon as a pointing
acquisition and tracking (PAT) aid, however beaconless PAT may be feasible in the future. 1
Previous Lunar Missions with High Data Rate RF
K Band Transmitter on board the LRO
The Lunar Reconnaissance Orbiter achieved a 100 Mbps data rate using a 40 W K band
transmitter. According to a Q&A found online the X band is not permitted to be used from
the moon, however this statement was unable to backed up from further searches.2
Furthermore, the FCC allocates several X band frequency ranges to Deep Space Research
Space-to-Earth.

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Previous Optical Communication Demonstrations
LLCD on board the LADEE Spacecraft, NASA 2013
The Lunar Laser Communications Demonstration downlinked 622 Mbps using an
infrared laser from Lunar orbit. An optical uplink was also utilized which transmitted 20
Mbps from a ground station located in White Sands, NM. The Optical Link Study Group
indicated several scenarios in which the payload could operate using a 0.5 Watt laser: at
1300 km, the study indicates a data rate of 10 Gbps, however from Lunar orbit the data rate
is reduced to 622 Mbps.2
OPALS link with the ISS, JPL 2014
The Optical Payload for Lasercom Science on board the ISS successfully demonstrated
a laser communications link with the Optical Communications Telescope Laboratory (OCTL)
as well as other ground stations around the world in May of 2014. A downlink rate of 50 Mbps
was achieved with a 2.5 Watt laser as well as a laser beacon uplink in order to provide
closed-loop tracking to maintain the link.3
Optical Ground Stations
Wrightwood, CA
The optical ground station maintained by JPL in Wrightwood, CA was used for the
OPALS link with the ISS in 2014. "It utilizes OCTL's 1-meter primary telescope aperture to
receive the downlink signal and transmit the reference beacon. The received optical signal
is acquired and focused onto a photodetector, which converts the optical signal to baseband
electrical current. After necessary digitization, synchronization, error-correction and post-
processing, the video file is displayed on a monitor. The OCTL telescope relies on orbital
predictions built from ISS GPS state vectors to follow the ISS as it traverses its path across
the sky." 4
Mount Teide, Tenerife in the Canary Islands
The optical ground station on Mount Teide constructed by ESA is equipped with a 1
meter aperture and 25 W ion Argon laser. It has been utilized for optical communications
testing since 2001.5
White Sands, NM
The Lunar Lasercom Ground Terminal (LLGT) was developed by MIT for the LADEE
mission. The LLGT consists of an array of four 15 cm transceiver telescopes and four 40 cm
receiver telescopes and a control room. 6
RF Ground Stations
Although many RF terminals exist that have the potential to accept the X and Ka
bands, the Deep Space Network (DSN) has unparalleled gain and availability for the Aiken
Basin Mission. The DSN has 34 meter antennas located at 120 degrees apart from each other

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in Canberra AU, Madrid SP, and Goldstone CA. The locations of these stations results in a
potential of 100% availability at altitudes past GEO.
Trade Study
The four frequencies selected were compared against the following discriminators:
1. Power required for data transfer
The power required significantly decreases for higher frequencies. For a given
distance of 465,000 km (Earth to L2), the power required holding other parameters
constant is estimated in table 1. Note these estimates account for extra channels
required using lower frequencies to obtain the required data
X band Ka Band V Band Optical
Power Required (W)
1500 100 30 5
Due to the lack of familiarity with an optical link budget, 5 W is an order of
magnitude estimate for an optical power required based on the powers and data
rates achieved by the aforementioned missions.
2. Volume required for subsystem
Because the achievable data rates are not constant across frequency bands, the
number of channels and thus the number of components will increase with a lower
frequency. In addition, the diameter of the antenna required to compensate for
power will contribute to a significant increase in communication subsystem volume.
3. Flight heritage
The flight heritage discriminator indicates how many missions have utilized said
frequency band. This will greatly determine the amount of resources available for
designing the required communication subsystem. Because the X and Ka bands are
commonly used for downlink, they require only an extension of power and bandwidth
to achieve the required data transfer.
4. Tracking rate required to maintain link
The tracking rate is primarily a function of beam width which decreases dramatically
for a laser communication system. However the tracking rate does not significantly
change across RF bands.
5. Ground station requirements
The ground station requirement applies only to the link between L2 and Earth and
indicates the estimated price of ground station operations and required installations.
Because there are very few optical ground stations in existence, it may be necessary
to install optical capabilities at an existing ground station (This would be desired due
to the infrastructure in place3
). Although no commercial ground stations appear to
utilize the V band, it may be feasible to install the necessary demodulator on an
existing ground station.
Each band was ranked for communications between the Moon and L2 as well as L2 to
Earth, resulting in the following trade matrices:

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Conclusion
The results of the trade study indicate that it may be desirable to implement an
optical communication link between the Lunar surface and L2, and a Ka band link between
L2 and Earth.
The benefits of having an optical subsystem onboard the lander are numerous
including a dramatic reduction in power in mass. However, this subsystem must be capable
of tracking a spacecraft at an altitude of 80,000 km. Although this particular configuration,
a laser communication uplink from lunar surface to lunar orbiter, has not been attempted
before, it removes the major drawbacks of atmospheric losses and ground station availability.
Future considerations should be taken for maintaining the link during landing; the optical
link will require much more stability but pointing a high gain antenna may also present
challenges.
For the link between L2 and Earth, the Ka band appears to be the optimal choice
mainly due to the ground station availability. Utilizing the DSN yields the added benefits of
100% availability as well as extremely high gain.
Conclusion Update 5/26/16
Because of the initial RFP-given requirement of transmitting video in real time during
Lander descent, optical was ruled out due to the stringent pointing requirements. In
addition, optical communication components are not readily available because the
technology is relatively new. However, in the last month of the mission design the data rate
during descent was negotiated down from 1.6 Gbps to 4.5 Mbps. If this had been done at the

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beginning of the mission analysis an optical communication system would have likely been
used to transmit video data, however this change was introduced too late to allow enough
time for proper analyses and changes to be made. Therefore a Ka Band system was used to
transmit video, LIDAR as well as seismometer data due to component availability, reliability,
as well as power required. An X band system was decided upon for TT&C due to its heritage,
availability, as well as power required.
Sources
1
Optical Link Study Group Final Report, June 2012
2
Q&A (with LRO team?)
https://wiki.umn.edu/pub/ShackeltonCraterProject/LinksAndInfo/2-25-08_questions.docx
2
Lunar Laser Communication Demonstration NASA’s First Space Laser Communication System
Demonstration, https://www.nasa.gov/sites/default/files/llcdfactsheet.final_.web_.pdf
3
OPALS: Mission System Operations Architecture for an Optical Communications
Demonstration on the ISS, http://arc.aiaa.org/doi/abs/10.2514/6.2014-1627
4
JPL Optical Ground Station in Wrightwood, CA,
Californiahttp://phaeton.jpl.nasa.gov/external/projects/optical.cfm
5
Optical Ground Station on Mount Teide, Canary Islands,
http://www.iac.es/eno.php?op1=3&op2=6&lang=en&id=7
6
White Sands Optical Ground Station, http://esc.gsfc.nasa.gov/267/271/Ground-
Segment.html

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1.2 COMMUNICATIONS SATELLITE DISPOSAL - KURT ZELLER
(11/20/15)
This analysis was performed in order to provide justification of the L2 halo
orbit. Although the orbits team further analyzed this trade in much more
detail, this paper proved that Relay Satellite disposal from an L2 halo orbit
was entirely possible and that this orbit is still a viable solution.
Introduction
End-of-life disposal of the communications satellite is a requirement regardless of its
location. Two scenarios are considered which have varying degrees of complexity, delta V
required, and safety. Some added benefits of certain disposal methods will also be discussed.
Lunar Impact
The first scenario considered for end-of-life disposal is a lunar impact. The V
required to put the satellite on a crash course with the moon from L2 is approximately 200
m/s.1
This change in velocity must be provided in a precisely controlled manner in order to
place the satellite in a trajectory with an approved impact location. This predetermined
location must be compliant with all mitigations and treaties associated with the lunar
environment.2
A potential scientific benefit could come if the impact is located on the
Earth-facing side of the moon: laser spectrometry could be used to determine the
composition of the dust cloud created by the impact.
The largest benefit of the Lunar impact scenario is that it certainly provides "end-of-
life" without the possibility of return. The largest drawbacks of this scenario are the extra
fuel needed and the added complexity associated with determining a crash site.
Heliocentric Graveyard Orbit
Many spacecraft on the outer edge of Earth's sphere of influence have been disposed
of in a heliocentric graveyard orbit. This orbit is relatively easy to achieve from the Earth-
Moon L2 and only requires approximately 20 m/s change in velocity.1
Unfortunately this
orbit does not guarantee that the spacecraft will not return to the Earth system.
The largest benefit of the graveyard orbit is that it requires the least amount of fuel,
however the largest drawback is that it may come back as a large piece of debris in the
future
Trade Study
The following discriminators were chosen to rank the aforementioned options:
1. V Required
2. Complexity
3. Safety
4. Added Benefits
After ranking the options based on the previous discriminators, a trade matrix resulted:

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Conclusion
After analyzing the potential disposal options, it is still unclear which option will be
the best for the Aiken Basin Mission. The two options ranked very closely together, and until
a final communications satellite mass has been determined it cannot be ascertained which
option should be chosen.
Sources
1
Code written by Taylor Young
2
Disposal Stategies,
http://www.researchgate.net/profile/Roberto_Armellin2/publication/261437751_DISPOSAL_
STRATEGIES_FOR_SPACECRAFT_IN_LAGRANGIAN_POINT_ORBITS/links/0c960534445586bd4800
0000.pdf

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1.3 SEISMOMETER DATA TRANSFER - KURT ZELLER
2/9/16, updated 5/25/16
This paper first analyzes the possible configurations that could be used to
transfer seismometer data over the required 3 years. The magnitudes of
distance and velocity across the L2 Halo orbit were used to determine the
time of contact for a stationary antenna with a fixed half power beamwidth
(HPBW). Three situations were analyzed: (1) Using only an omnidirectional
antenna, (2) using a horn, and (3) modifying the high gain dish. The first
analysis showed that the 2 meter dish has enough contact time to transmit
32 days of data with < 1 W of RF with any of the chosen frequency bands.
The accuracy of the orbit should be further analyzed to determine if
maintaining the trajectory to this degree will require excessive delta V.
This first analysis was used to justify a no gimbal requirement on the
seismometer transmission operations which dramatically improved
reliability and power. Later in the design many changes had been made due
to other considerations and the seismometer data transfer operation was
adapted to accordingly. The horn antenna will be the primary means of data
transfer at least once per 20.8 days. This antenna will have three chances
to transmit data, but if two chances happen during lunar day, the 2 meter
dish will be used to compensate during lunar night.
Introduction
The current baseline leaves the seismometer on surface of the moon with the Ka band
high gain antenna (2 meter dish). This dish will be gimbaled so that it can track the Comm Sat
during drilling operations, however, for the three year seismometer operations the antenna
should remain stationary. Not only does the gimbal require 5-10 W, it is a failure point that
should be avoided if possible.
Furthermore, the high data rate communication system is overpowered to transmit the
relatively small amount seismometer data and would require a large amount of power to
remain in standby mode. Attempting to turn these amplifiers on and off is generally not a
common practice due to the internal components of the amplifier.
Note that if the high data rate system had a “low power mode” in which the
transmitter signal were rerouted around the TWTA we could use the high data rate
transmitter while minimizing the standby power and maximizing reliability. This would also
maximize the antenna gain by not having an X or S band feed included.
Final Requirements:
 Seismometer data shall be downlinked to the Relay Sat a minimum of once per
20.8 days for the duration of the three year mission (shorter than the RFP
required "once per month" due to Relay Sat halo orbit)
 Antenna gimbals shall be locked in place for the duration of the mission
 Transmission shall only happen during lunar night (for thermal balance)

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 TWTA's shall not be used to transmit seismometer data (due to power and
reliability)
Some of the assumptions used in this analysis are as follows:
 Half power beamwidth = HPBW = 70*c/(freq*diameter)
 Conical horn gain = 10log10( (pi*lambda/d)^2 *eta)
 Conical horn beamwidth = 51*lamda/d
 5 kbps of seismometer data generated [research by Brian Kraft in Payload
subsystem]
Figure 1. Position and velocity of the Comm Sat from the Moon as determined by Joe Gagliano
[See Appendix]
1. Using an omnidirectional antenna
The power required to transmit all seismometer data through an omnidirectional antenna was
calculated and the results can be seen in the following table: [Note that the result is
independent of frequency due 0 gain on the transmitter side and free space canceling
receiver gain]

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Receiver Diameter (m) 5.5
Assumed Noise Temperature (K) 800
Distance (km) 45000
Eb/N0 (dB) 10
Data Transfer Time (hr) 48
Data Rate (kbps) 80
Link Margin (dB) 3
RF Power Req (W) 131.1
Conclusion
Seismometer data transfer through an omnidirectional is probably not feasible and would
require far too much power.
2) Using a horn or 3) using the high gain antenna
(either modifying the high gain to accept S or X, or using Ka.)
● The following plot was created using Joe’s position and velocity of the Comm Sat over
the course of its orbit.
● The half power beamwidth was used to determine a footprint at a given distance
● This footprint diameter was divided by the velocity magnitude to determine a “time of
contact”
● antenna is left stationary
● Comm Sat must maintain its trajectory

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The distance chosen for all of these analyses was 70,000 km which corresponds to the the 6th
and 11th day in orbit. This was chosen to provide
S Band X Band Ka Band
Half Power Beamwidth (deg) for 2 m 4.375 1.30 .33
Est Time of contact (hr) 15 4 1
Data Rate Required (kbps) 256 960 3840
RF Power Required (W) .37 .13 .031
Half Power Beamwidth (deg) for 1 m 8.75 2.59 .65
Est Time of contact (hr) 35 10 2.5
Data Rate Required (kbps) 109.7 384 1536
RF Power Required (W) .63 .2 .06
Half power beamwidth of horn (deg) 32.9 18 9
Horn gain (dB) 11.2 16.4 22.4
Est Time of Contact (hr) 120 62 30
Data Rate Required (kbps) 32.0 61.9 128.0
RF Power Required (W) 9.7 5.6 2.9
To find the power required all of these assumptions were kept constant:
● 5.5 meter receiver, 55% efficiency
● Noise temperature 700 K
● Distance of 50,000 km
● Eb/N0 of 10 dB
● Link margin of 3 dB
● Polarization losses of 3 dB
● Pointing losses of 3 dB
● Line losses of .4 dB
First Analysis Conclusion
It appears as though reusing the high gain antenna would be the most optimal choice.
Adding an S band feed to this dish would not make sense due to the large size of the
waveguide and horn required. An X band feed could probably be adapted to fit the high gain
system at the expense of some loss in gain during high data rate transfer.
Optimally we should reroute the Ka band transmitter to a low power amplifier that
requires little standby power. If this low power amplifier is capable of >1 W RF, we should be

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able to achieve data rates on the order of 80 Mbps which equates to transmission times (for
32 days of data) of around 5 minutes.
Further Considerations
Later in the design process several mistakes were discovered and changes were made
including, but not limited to:
 6 meter parabolic receiver, 55% efficiency
 Eb/N0 required: 8.8 dB using 16-QAM
 Assumed FEC coding gain using FEC 7/8 Turbo: 5.2 dB for a BER of 10^-6 (this was
assumed for ALL links using the Lander Ka Band system)
 Line losses were more accurately determined after layout completion: Horn 2.0 dB and
Dish 4.5 dB.
 Distance was increased to 80,000 km for maximum contact time
 Receiver noise temperature decreased to 554 K
 Link margin was calculated to satisfy power limit on the transmitter
At Boeing we were told that a bandwidth of 1 GHz is too wide to expect consistent
performance across the spectrum. Therefore we decided to change modulation scheme from
QPSK to 16-QAM which reduced the bandwidth to 480 MHz for video data. Unfortunately this
caused the seismometer link margin for the horn transmission to decrease to 0.6 dB, too low
by most standards. If we were able to switch modulation schemes during the mission from 16-
QAM for video and LIDAR to QPSK for seismometer, we could have had a link margin above 4
dB, however we were unsure whether this was advisable or even possible.
The following plot shows the contact time for the quarter power beamwidth of the 2
meter dish for each distance from the moon [See Appendix]. Each contact time was
determined by assuming the Relay Sat passes across the diameter of the footprint at the same
speed as the magnitude of the velocity.

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The next plot shows the contact time for the same orbit for the horn HPBW. Note that
the horn footprint was assumed to be circular with a radius equal to the sum of the squares of
the E plane and H plane directions.
These plots allowed were used to determine the maximum data rate achievable with
each antenna keeping the power output of the transmitter at a constant 2 dBW (quoted from
the uKaTx data sheet). The following tables describe the parameters for each case: (note that

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the link budget and block diagrams have a more detailed description of all parameters and
components)
It was clear that the gain of the 2 meter dish allows a much higher data rate but also
significantly less contact time.
Final Conclusions
After extensive pointing analysis done by Hunter O'Brien (see gimbal requirements), it
was determined that the horn antenna will be the primary transmitter of seismometer data
due to its larger contact window. This antenna will have three opportunities to relay the
data, one of which will always happen at night. In this case, the dish will be used to
compensate for these two missed transmissions during a different night period.
All requirements are thus met but future considerations should be made to improving
the horn system such that a larger link margin is acquired. This could be done by changing the
modulation scheme mid-mission as previously discussed. Finally, it was discovered that the Ka
Band block diagram would not allow seismometer data to be transmitted through the dish
which is further discussed in the block diagram analysis.

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1.4 HIGH GAIN ANTENNA DESIGN - KURT ZELLER
3/30/16 - 5/23/16
This paper describes the design of the high gain antenna required on each
Lander vehicle used on the ANGELS Mission. Several design iterations were
made over the course of two months using various tools such as MATLAB,
GRASP, and CREO. A rigid center-fed symmetric Cassegrain antenna was
chosen due to its high gain, reliability, and simple layout constraints which
results in a half-power beamwidth (HPBW) of 0.3° and a gain of 52 dB. The
pointing variability was analyzed and assumed to be 0.05° in the ADCS
analysis. A plate structure was designed to accommodate a 10,000 lbf
preloaded separation nut to remove the 40 g's of vibrational loading from
the gimbals. Finally, the torque on the gimbal caused by the ascent vehicle
plume was analyzed and was determined to be within the gimbal holding
torque capabilities.
Antenna Requirements
Preliminary designs focused on a Cassegrain design due to the performance
requirements set by the mission architecture which are as follows:
 Shall be able to gimbal in two axes
 Shall have the ability to rotate a minimum of ±40° about the elevation angle and
between 0° and 50° about the azimuth angle.
 Shall provide a minimum of 52 dB of gain at ±0.15 degrees
 Shall provide a minimum of 35 dB of gain at ±0.35 degrees in order to point during
descent (This requirement was intended to allow pointing the dish during descent
and was later removed when a horn antenna was introduced)
 Shall be able to withstand the ascent vehicle take-off while maintaining pointing
 Shall allow for No single point failures except in structural considerations (gimbals
included as structure)
[1] Antenna Basics

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Early designs
The first design investigated was based off of a classic Cassegrain 2 axis gimbaled antenna
patent [2].
Unfortunately due to layout constraints this design was temporarily abandoned.
Before presenting at Lockheed Martin, a deployable antenna was designed based on designs
created at Cal Tech for a Ka Band 0.5 meter CubeSat antenna [3].

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Although this design was less massive and significantly less volume when stowed, an
electrical systems engineer at Lockheed Martin suggested that the design seemed too flimsy,
especially considering that it is required to transmit during ascent vehicle lift-off. In addition,
the Ka Band design created by Cal Tech was only intended to be used with a 0.5 m to 0.75 m
parabolic dish whereas we wanted to extend it to a 2 m dish. Furthermore this design does
not utilize an off-the-shelf (OTS) gimbal which is highly desirable for the Communications
team to improve reliability and to meet the TRL 7 requirement.
Rigid Reflector Design
In order to regress back to the initial designs, some sort of deployable arm would be
necessary in order to stow a hard shelled Cassegrain antenna. This arm would ideally have an
OTS gimbal that meets the motion requirements previously stated.
Extensive research was done into Cassegrain design and dimensioning and a MATLAB
code [See Appendix] was developed to determine dimensions. Seen in the following figure,
one design was plotted with its corresponding features:

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However, when performance was considered, it was deemed necessary to utilize
GRASP instead which conveniently computes dimensions of dual reflector antennas rendering
the MATLAB efforts fairly useless. Many iterations of f/D were attempted to determine the
minimum focal distance which met the performance requirements. This minimum focal length
was desirable because of layout and deployment concerns.

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It was decided that an f/D of 0.35 would be the ideal option because it met the gain
requirement of 35 dB at ±0.35 deg and had a relatively short focal length. Smaller focal
lengths were considered however performance concerns caused the team to maintain a
minimum f/D of 0.35.
The GRASP Dual Reflector Wizard drew the ideal Cassegrain dish seen in the following
figure:

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Dimensions were taken from this figure and a CREO model was developed seen in the
following figure:
Upon further consideration, it was determined that the subreflector size and
eccentricity would yield an edge illumination that wouldn't efficiently use the entire dish.
Therefore the following final dimensions were used in GRASP:

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These dimensions yielded the following gain:

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The beam deviation was calculated using the following equation:
D_theta = D_vertex - D_focalpoint*(1-K)/F where K = RF deviation factor and F = focal length.
The following plot was created and it was assumed that a beam deviation of 0.04 degrees
would be achievable. [See Appendix]

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Dish Mount and Launch Lock
An antenna structure was created by Brian Kraft (Payload subsystem) based on picture
of other satellite antennas. The following figures detail his initial antenna structure design:

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Unfortunately this structure provided insufficient support of the dish during launch as
well as during landing. According to Dave Esposto, the dish will experience about 40 g's of
vibrational loading during launch which must be supported before the gimbals due to their
sensitive bearings. This launch lock would ideally be held by a separation nut that would be
electrically redundant thus satisfying the "no single point failure" requirement. The final
design iteration seen below incorporates a plate on the dish mount between the vertical
gimbal and the parabolic dish:

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A plate size of 8 in by 8 in was chosen due to concerns of available separation nut
strength. However, upon later consideration the plate size could have been reduced which
would further reduce the moment arm and cause significant downsizing.[4] However this
analysis succeeded as a conceptual verification that this size dish could be supported within
the given layout constraints.
In the current configuration, the separation nut would be preloaded to 10,000 pound
force to compensate for the forces and moments experienced during launch and landing. This
separation nut would be placed through the center hole in the plate and provide 2,500 pound
force to each supported corner. The following image shows that the entire assembly barely
fits within the fairing envelope. However due to mission level pointing constraints, it would
be infeasible to bring the dish much closer to the Lander body because doing so would further
limit its horizontal and vertical range due to interference with other vehicle parts.

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Ascent Vehicle Take-Off
Lastly, an analysis was performed in order to determine whether the gimbal would be
able to provide enough holding torque to maintain pointing during ascent vehicle lift off. The
holding torque of the OTS gimbal chosen is 1300 in-lb. The following plot indicates the
stagnation pressure of the plume from one ascent stage nozzle directly downstream [5]:

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Given that the minimum distance from the center of the thruster to the back of the
dish is about 20 inches, the maximum stagnation pressure it could experience is about 0.007
psi. The gimbal holding torque required was plotted against impingement area in the
following figure. [See Appendix] Note that the entire are of the back of the dish is about
4,500 in^2, and the ascent vehicle plume could only possibly push against the top half of it.
It is clear that the maximum gimbal holding torque available is well above the
expected torques experienced. However this analysis restricted the antenna between 0 and
30°vertical angle to ensure that the inside of the dish would not be contaminated. Luckily
this falls within the allocated pointed schedule create by Hunter O'Brien. [6]
References

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[1] Antenna Basics: http://my.ece.ucsb.edu/York/Bobsclass/201C/Handouts/Chap3.pdf
[2] Cassegrain antenna patent: http://www.google.com/patents/US6285338
[3] Cal Tech CubeSat Antenna:
https://icubesat.files.wordpress.com/2014/06/icubesat-org_2014_b-1-4-
kupda_sauder_20140617.pdf
[4] High Shear Separation Nut Data Sheet: www.hstc.com/Download.aspx?ResourceId=50125
[5] Code by Daniel Johnson, Propulsions Subsystem
[6] Pointing schedule

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1.5 KA BAND SYSTEM - KURT ZELLER
5/29/16
This paper describes the design and analysis of the Ka band system
responsible for transmitting LIDAR, video and seismometer data from the
Lander to the Relay Satellite. First a block diagram was developed using off-
the-shelf (OTS) components. Next each link was analyzed block-by-block to
determine equivalent noise temperatures, net insertion losses, and
resulting TWTA output power required. The transmitter noise temperature
was determined to be essentially negligible due to free space loss. The
receiver noise temperature was calculated to be 554.4 K resulting in a
required TWTA output power of 93 W RF.
Finally each component was modeled in CREO. A box (38" x 25" x 8.3") was
given to house all ka band components and mount the horn antenna. The
exact line losses were determined to be 4.5 dB for the dish, 2.6 dB for the
horn (LIDAR) and 2.0 dB for the horn (seismometer). A horn antenna was
designed to have a gain of 30 dB in order to transmit LIDAR and
seismometer data which resulted in aperture dimensions of 4.5" x 3.5". The
horn length was estimated to be 9" based on OTS horns available, however
no analysis was performed on the radiation pattern available due to lack of
resources.
System Requirements
The Ka Band System shall:
• Transmit 1.6 Gbps of video data during Lunar operations (drilling, sampling,
etc) to the Relay Satellite in real time
• Transmit LIDAR data during the last 2 km of descent to the Relay Satellite in
real time
• Transmit seismometer data at least once per month to the Relay Satellite for
three years after the last lander departs the moon
• Consist entirely of TRL 7 components and have no single point failures
Block Diagram Design
Many iterations were made to the block diagram which resulted in the
following schematic:

~ 31 ~
This quick summary was presented on the poster:
• Seismometer data does not use TWTA’s
• TT&C data will be sent on same line as seismometer during seismometer
operations
• The transmitter and TWTA’s are cold redundant
• The receiver and gimbal controller are internally redundant
• WR28 waveguide rotary joints are used inside each gimbal
• Step tracking is used to point each antenna to the Relay Satellite
Transmitter
The video/LIDAR/seismometer data is first relayed to the uKatx Ka band
transmitter. Note that this transmitter does NOT have the capability to transmit at
31.8±.45 GHz but it was assumed that this specification could be requested from the
manufacturer. This transmitter was chosen primarily due to its data rate capabilities,
relatively high output power, and relatively small size. This transmitter is assumed to
have a 16-QAM encoder, oscillator, filter(s), and some sort of throttlable solid state
amplifier to reach a maximum output power of 2 dBW. This component was not
specified to be internally redundant therefore a cold redundant transmitter was
included to meet the no single point failure requirement.

~ 32 ~
TWTA Bypass for Seismometer Data
The transmitter outputs an RF signal through an ultra low loss coaxial cable
into a coax-to-waveguide end launch transition. This was done because the switches
used are all WR 28 waveguide latching switches (33C98100) thus we must convert from
a coax cable to a waveguide, and an end launch made sense for layout. Next this
switch either sends the signal to the TWTA operating at 93 W RF or into the
seismometer line bypassing the amplifier. It is worth noting that it was unknown
whether a TWTA could be built with an internal bypass, however due to the extra
components in the high power line the insertion losses would have been too great to
maintain the seismometer data rate required.
A week after the Symposium presentation it was discovered that the
seismometer line does not have the ability to transmit though the dish (whoops!). This
could have been done by rearranging the switches and combiners before the
circulators. Luckily no one noticed this mistake.
Isolator and Combiner
After each TWTA is a high power isolator that is required to ensure that any
temporary impedance match that resulted in excessive reflected power (during
integration and test (I&T)) would not result in a destroyed amplifier. These lines are
both fed into a two-to-one waveguide combiner. Note that there was some concern
from Dave Bernstein of SSL as to whether this component could operate as shown
without sending power back up the cold line. However Bradley from Boeing who works
on communication payload schematics did not indicate any issues with this
configuration two weeks prior.
Switching between Antennas and the Test Couplers
After the high power combiner there are two identical waveguide latching
switches: both are initially set to send power towards the horn. If the first switch were
to fail to send power to the dish, the second switch would be able to correct for this
single point failure. Note that if the first switch were to fail later in the mission when
switching from the dish back to the horn for seismometer data, there would be a
mission failure. This single point failure was not discovered until a week after
symposium and should have been addressed.
Before each antenna a broad wall test coupler was placed so that during I&T
the lines could be tested without powering the antenna. This is performed by
replacing a waveguide with a high power termination and attaching a spectrum
analyzer to the test coupler. This allows verification that data can be sent across the
line before performing near field and far field ranging, a much more extensive process
that happens much later in the I&T process.
Gimbals
Finally both lines are fed through the center of two OTS gimbals through a WR
28 waveguide rotary joints to minimize losses. These gimbals are controlled by an

~ 33 ~
antenna pointing mechanism that uses step tracking to follow the relay satellite. This
method of tracking essentially steps the antenna in a small spiral pattern and detects
the orientation of maximum power received.
Layout Design
All components were designed and assembled using CREO 3.0. Note that the
interfaces between the on-board computer and the switches, transmitters, and
receiver are missing. The interfaces between the batteries and the transmitter,
receiver, gimbal controller, and TWTA power supply are also missing. This entire panel
weighs approximates 50 kg and contains all the components necessary for the Ka band
system except the high gain parabolic dish. The yellow waveguide seen feeds the horn
mounted on the opposite side of the panel. The open orange waveguide seen in the
top left feeds into a series of waveguides that lead to the high gain dish. The black
waveguides are OTS WR 28 flex waveguides which will allow each component to be
bolted to the panel before all waveguides are attached without concern for small
tolerances on the order of 0.05". Although these waveguides are quoted to have
slightly higher losses, they were assumed to be equivalent to a rigid waveguide
because they were all used in straight sections.

~ 34 ~
The next image of the opposite side of the panel shows the horn antenna with
a dielectric cover also known as a radome. This cover prevents any debris from
getting in the horn during and preventing transmission.

~ 35 ~
This final layout image shows the TT&C system located on the ascent vehicle
which will be discussed in its respective section.

~ 36 ~
Line Losses
The following table depicts the assumed insertion loss for each type of line. Note that
the TWTA gain was held constant for the high power lines meaning that the input power was
adjusted within the transmitters capabilities. This meant that the only line losses that needed
to be considered were after the TWTA.
However for the seismometer line, the transmitter power was held at maximum (2
dBW) and each line after it was included. The seismometer lines were somewhat shorter
leading to slightly smaller losses. These losses were accounted for in the block diagram
analyses.
Block Diagram Analyses
In order to determine the output RF power required from the TWTA each component's
figure of noise was considered. This analysis consumed a large portion of our design process
during Winter Quarter due to confusion between different information sources as well as lack
of guidance. Thus, our resulting methodology is presented for your convenience.
Starting with the receiver, the cascaded noise temperature was calculated using the
conventional methodology present in many communications text books. The receiver block
was assumed to contain an LNA, filter(s) and demodulator and was found as a self contained
OTS unit. This equivalent noise temperature was added to the noise temperature seen by the
receiving antenna which was used to calculate the noise power received by the demodulator.
Next, the SNR required was calculated using the equation from SMAD: SNR (dB) = Eb/N0 (dB) +
10Log10(Data Rate (bps)) - 10Log10(Bandwidth (Hz))
This SNR was then added to the noise power received at the demodulator found
previously from the cascaded noise temperature which results in the signal power required at
the demodulator. This signal power was then propagated upstream using the losses and gains
from the link budget and through each component on the transmitting end until the output RF
power was found. All of the numbers associated with this analysis can be found in the
Appendix.

~ 37 ~
Conclusion
After extensive analysis and design of the Ka band system several issues were never
completely solved including switching between antennas during seismometer operations as
well as the link margin of less than 3 dB for seismometer data transfer from the horn.
Nevertheless, a block diagram analysis was developed to accurately determine the output RF
from the TWTA's. OTS components were chosen, designed in CREO and a laid out onto a single
fully integrated panel that could easily be constructed and tested before integration with the
rest of the vehicle. Line losses were determined using quoted numbers from online sources
and length measurements from the CREO layout. Further work would need to be performed to
ensure this system would meet all of the given requirements.

~ 38 ~
1.6 APPENDIX
SNR Calculations

~ 41 ~
Antenna Torque - Kurt Zeller
clc; clear; close all
A = linspace(200,4585,1000); %in^2
L = 21; %in
P = linspace(.002,.007,6) ; %psi
color = 'brgcmk';
figure(1)
for i=1:length(P)
T(:,i) = A.*L*P(i);
plot(A,T(:,i),color(i),'linewidth',2)
hold on
xlabel('')
ylabel('')
end
% plot(A,500,'ok')
grid on
set(gca,'FontSize',14)
tlhand = get(gca,'title');
xlhand = get(gca,'xlabel');
ylhand = get(gca,'ylabel');
set(tlhand,'string','Gimbal Torque During Ascent','fontsize',16)
set(xlhand,'string','Impingement Area (in^2)','fontsize',16)
set(ylhand,'string','Torque (in-lb)','fontsize',16)
h = legend(num2str(P(:)),'location','eastoutside');
v = get(h,'title');
set(v,'string','Stagnation Pressure (psi)','fontsize',14);
Dish Launch Lock - Kurt Zeller
m_dish = 20*2.2; %#
Launch = 40; %gs
M = linspace(8,20,100); %inches
V_load = m_dish*Launch; %max vert load (#s)
plate = [4 6 8 10 ];
color = 'brgkm';
figure(1)
for j=1:length(plate)
for i =1:length(M)
F(i,j) = V_load/4 + V_load*M(i)/2/plate(j);
end
plot(M,4*F(:,j),color(j))
hold on
end
title('Total Separation Nut Preloading Required')
xlabel('Moment Arm between Dish CG and Sep Nut (inches)')
ylabel('Preload Force Require (lb_f)')

~ 42 ~
h = legend(num2str(plate(:)),'location','eastoutside');
v = get(h,'title');
set(v,'string','Plate Contact Point Spacing (in)');
Beam Deviation - Kurt Zeller
clc
clear
clear all
f_D = .35; %focal length/diameter
k = .35; %Between .3 and .7, larger for high tapering
K = (1+k*f_D^2)/(1+f_D^2); %RF beam deviation factor
F = 51.18; %focal length (in)
color = 'brgmky';
d_v = linspace(.001,.1,5); %deviation of vertex (in)
d_fp = linspace(.001,.1,100); %delta focal point (in)
figure(1)
for i=1:length(d_v)
for j=1:length(d_fp)
d_theta(i,j) = d_v(i) - d_fp(j)*(1+K)/F;
end
plot(d_fp,d_theta(i,:),color(i))
hold on
end
title('Beam Deviation assuming RF Deviation Factor of .35')
xlabel('Focal Point Deviation (in)')
ylabel('Pointing Angle Deviation (deg)')
h = legend(num2str(d_v(:)),'location','eastoutside');
v = get(h,'title');
set(v,'string','Vertex Deviation (in)');

~ 43 ~
Cassegrain Dish Dimensions - Kurt Zeller
ep0 = 8.85*10^-12; %permit free space
mu0 = 4*pi*10^-7; %permeab free space
c = 1/sqrt(ep0*mu0); %Speed of light (m/s)
freq = .5*(31.3+32.3)*10^9; %Chosen Center Freq (GHz)
lamda = c/freq; %Wavelength (m)
f_D = .65; %chosen focal length/diameter ratio for high cross pol performace
Dm = 2; %chosen diameter (m)
F = f_D*Dm;%focal length (m)
dF = .8; %Distance between Foci (m)
e = 1.3;
thetaE = 5.744; %Half Angle subtended by subreflector @ feed (deg)
H0 = Dm^2/(16*F); %depth of dish (m)
Df = .14; % feed diameter (m) (from GRASP)
f = F-dF; %Subreflector Focal length
a = e/f;
Ds = F*Df/(2*f);
% thetaE = atan2( (8*F*Dm*Ds) , (32*F*f*Dm - Ds*(16*F^2 - Dm^2)));
Ls = (-2*Dm*f)/(-Dm - 4*F*tan(thetaE/2));
Lm = F- 2*f;
TR = 15; %Taper ratio in dB (ASSUMED)
E = 10^(TR/10);
ata = (1 + log(sqrt(E))/(1-sqrt(E))*(1+ 4*sqrt(1-Ds/Dm)*(Ds/Dm)^2))^2;
Gain = 10*log10(ata*pi^2*(Dm^2-Ds^2)/lamda^2 );
color = 'brgkm';
N = 50;
r = linspace(0,Dm,N);
rs = linspace(0,Ds,N);
rf = linspace(0,Df,N);
Phi = linspace(0,2*pi,N);
for i=1:length(r)
for j=1:length(Phi)
%Main Dish
xm(i,j) = r(i)*cos(Phi(j));
ym(i,j) = r(i)*sin(Phi(j));
%Sub Reflector
xs(i,j) = rs(i)*cos(Phi(j));
ys(i,j) = rs(i)*sin(Phi(j));
end
end
%Feed Aperture
xf = Df*cos(Phi);
yf = Df*sin(Phi);
zf = -2*f*ones(1,length(xf)); %Height of Feed
%Dish Rim
xD = Dm*cos(Phi);

~ 44 ~
yD = Dm*sin(Phi);
zD = -F*ones(1,length(xD))+H0;
zDs = a*sqrt( 1 + (xs.^2+ys.^2)/(f^2-a^2) ) -f; %Sub Reflector
zDm= (xm.^2 + ym.^2)/(16*F) -F; %Main Dish
Ax = [0 0 0; 0 0 F]; %Axis of Symmetry
LL = [0 0 zf(1); xs(end,1) ys(end,1) zDs(end,1)]; %xf(1) yf(1) zf(1)
LL2 = [xs(end,1) ys(end,1) zDs(end,1); xm(end,1) ym(end,1) zDm(end,1)];
RL = [0 0 zf(1); xs(end,N/2) ys(end,N/2) zDs(end,N/2)];
RL2 = [xs(end,N/2) ys(end,N/2) zDs(end,N/2); xm(end,N/2) ym(end,N/2)
zDm(end,N/2)];
f = figure('Position', [100, 100, 1500, 895]);
plot3(xm,ym,zDm,'k')
hold on
plot3(xs,ys,zDs)
plot3(xf,yf,zf,'linewidth',2)
plot3(xD,yD,zD,'k','linewidth',2)
plot3(LL(:,1),LL(:,2),LL(:,3),'--r','linewidth',1)
plot3(LL2(:,1),LL2(:,2),LL2(:,3),'--r','linewidth',1)
plot3(RL(:,1),RL(:,2),RL(:,3),'--r','linewidth',1)
plot3(RL2(:,1),RL2(:,2),RL2(:,3),'--r','linewidth',1)
% hold on
plot3(0,0,F,'or','linewidth',2)
axis equal
xlabel('meters')
ylabel('meters')
zlabel('meters')
axis equal
title('Cassegrain Dish')
% legend('Main Reflector','Subreflector','Feed Diameter/placement','Axis of
Symmetry','Focal Point')
%Puts paramters into table off to the right
f2 = figure('Position', [100, 100, 1500, 895]);
space = {''};
dat = [freq/10^9; ...
1000*lamda; ...
f_D; ...
Dm; ...
Df; ...
Ds; ...
Lm; ...
F; ...
f; ...
H0; ...
TR; ...
ata; ...
Gain;
];
cnames = {'Value'};
rnames = {...

~ 45 ~
'Frequency (GHz)', ...
'Wavelength (mm)', ...
'f/D ratio' ...
'Main Reflector Diameter (m)', ...
'Feed Aperture Diameter (m)', ...
'Subreflector Diameter (m)', ...
'Feed Length (m)', ...
'Main Reflector Focal Length (m)', ...
'Subreflector Focal Length (m)', ...
'Dish Depth (m)', ...
'Taper Ratio (dB)', ...
'Efficiency', ...
'Gain (dB)'
};
t = uitable('Parent',f2,'Data',dat,'ColumnName',cnames,...
'RowName',rnames','Position',[200 200 600 500]);
hold off
Seismometer Contact Time (1) - Kurt Zeller
clear all; close all; clc
%% Velocities
open('L2Speeds.fig');
h = gcf;
axesObjs = get(h, 'Children');
dataObjs = get(axesObjs, 'Children');
tdata_vel = get(dataObjs, 'XData')/3600/24;
ydata_vel = get(dataObjs, 'YData');
%% Distances
open('L2Distances.fig');
h = gcf;
axesObjs = get(h, 'Children');
dataObjs = get(axesObjs, 'Children');
tdata_dist = get(dataObjs, 'XData')/3600/24;
ydata_dist = get(dataObjs, 'YData');
close all
figure(1)
subplot(2,1,1)
plot(tdata_dist,ydata_dist)
xlabel('Time (days)')
ylabel('Position Magnitude from Moon (km)')
hold on
subplot(2,1,2)
plot(tdata_vel,ydata_vel)
xlabel('Time (days)')
ylabel('Velocity Magnitude (m/s)')
%% Kurt's Problem
beamwidth = [.33 ];

~ 46 ~
% foot = [7628 2262 572 15212 4523 1145];
for j=1:length(beamwidth)
for i=1:length(tdata_dist)-1
foprint(i,j) = 2*ydata_dist(i)*sind(beamwidth(j));
time(j,i) = foprint(i,j)/ydata_vel(i)/3600;
end
end
colorx = linspace(0,1,10);
colory = linspace(1,0,10);
colorz = linspace(0,.8,10);
figure(2)
for i=1:length(beamwidth)
plot(tdata_dist(2:end),time(i,:),'color',[colorx(i),colory(i),colorz(i)])
hold on
xlabel('Period (days)')
ylabel('Time of Contact (hr)')
title('Time of Contact vs Period')
grid on
end
h = legend(num2str(beamwidth(:)),'location','eastoutside');
v = get(h,'title');
set(v,'string','Beamwidth (deg)');
Seismometer Contact Time (2) - Kurt Zeller
A = open('Halo.mat');
r = struct2cell(rmfield(A,'Vrel'));
v = struct2cell(rmfield(A,'Rrel'));
R = r{1};
T = r{2}/3600;
V = v{1};
for i=1:length(R)
R_mag(1,i) = norm(R(:,i));
v_mag(1,i) = norm(V(:,i));
end
vel = diff(R_mag)/diff(T');
figure(2)
subplot(3,1,1)
plot(T,R_mag)
xlabel('Time (hr)')
ylabel('Position Magnitude (km)')
title('Relay Sat Position vs Time')
grid on
subplot(3,1,2)
plot(T,v_mag)
xlabel('Time (hr)')
ylabel('Velocity Magnitude (km/s)')
title('Relay Sat Velocity vs Time')
grid on

~ 47 ~
E_plane = 4.22;
H_plane = 5.4;
% E_plane = 60;
% H_plane = 60;
for i=1:length(T)
d1 = 2*R_mag(i)*tand(E_plane/2);
d2 = 2*R_mag(i)*tand(H_plane/2);
f_diam(i) = sqrt(d1^2 + d2^2);
time(i) = f_diam(i)/v_mag(i)/3600;
end
subplot(3,1,3)
plot(T,time)
title(['HPBW of ',num2str(E_plane),' deg by ',num2str(H_plane),' deg'])
xlabel('Time (hr)')
ylabel('Contact time (hour)')
grid on
Lander Link Budget During Landing - Kurt Zeller
%% Case 1: Video Link Lander -> Comms Sat
% Transmitter and receiver diameters varied
freq = 32*10^9; %Frequency (Hz)
Eb_N0 = 12; %Desired Energy per bit to
noise density (dB)
Number_channels = 2;
Data_Rate = (1.6*10^9)/Number_channels; %Bits/sec
Distance = 45000; %km
%Transmitter
trans_diam = linspace(.75,2.5,100); %Transmitter diameter (m)
trans_ata = .55; %Transmitter efficiency
trans_type = 'D'; %Optical transmitter
amp_ata = 1; %Amplifier Efficiency
T_trans = 500; %Temperature the
transmitter sees (K) %(190
K for moon observing)
%NEEDS TO BE CHECKED
time = 1/60; %time of transmission
(hr)
battery_ata = 60; %battery efficiency
(Whr/kg)
%Receiver
reciever_type = 'D'; %Reciever type = D for
diamter or G for Gain/Temp
reciever = [3,4,5,6]; %m
rec_ata = .60; %Receiver efficiency
%Atmospheric Losses
atm_Y_N = 'N'; %Include atmospheric
losses? Y or N

~ 48 ~
L_z = .01; %Ka Band atm attenuation
(dB/km)
elev_ang_deg = 10; %Minimum elevation angle
(deg)
BW = 500*10^6; %Bandwidth (Hz) *Only used
for Max Data Rate*
Link_margin = 9;
color = 'brgmkc';
for i=1:length(reciever)
for j=1:length(trans_diam)
[P_trans_dB(i,j), R_max(i,j), L_atm, FSPL, L_p, LL, L_point, T_G,
R_G,...
Data_loss] = ...
Transmit_Power_Required(freq, Eb_N0, trans_diam(j), trans_ata,...
trans_type, reciever(i), reciever_type, rec_ata, atm_Y_N, L_z, ...
elev_ang_deg, BW, T_trans, Data_Rate, Distance);
P_trans_dB(i,j) = P_trans_dB(i,j)+Link_margin;
Power_Watt(i,j) =
Number_channels*10^(P_trans_dB(i,j)/10)/amp_ata; %50 W per
transmitter added
R_max_Mbps(i,j) = R_max(i,j)/10^6; %Convert to Mbps
end
end
Data_Rate = Data_Rate/(10^9);
f = figure('Position', [100, 100, 1500, 895]);
%Plotting power data
for i=1:length(reciever)
subplot(1,2,1)
plot(trans_diam,Power_Watt(i,:),color(i),'linewidth',2)
hold on
title('Video Link Lander -> Comms Sat')
xlabel('Transmitter Diameter (m)')
ylabel('RF Power Required (W)')
set(gca,'fontsize', 14);
grid on
end
% Legend
h = legend(num2str(reciever(:)),'location','eastoutside');
v = get(h,'title');
set(v,'string','Receiver Diameter (m)');
freq = freq/(10^9);

~ 49 ~
%Puts paramters into table off to the right
space = {''};
dat = [freq; ...
Eb_N0; ...
Number_channels;...
Data_Rate; ...
T_trans; ...
space; ...
L_atm; ...
L_p; ...
LL; ...
L_point; ...
Data_loss; ...
FSPL; ...
Link_margin; ...
];
cnames = {'Value'};
rnames = {...
'Frequency (GHz)', ...
'E_b/N_0 (dB)', ...
'Number of Channels', ...
'Data Rate per Channel (Gbps)', ...
'System Temperature (K)', ...
'LOSSES (dB)', ...
'Atmospheric Losses', ...
'Polarization Losses', ...
'Line Losses', ...
'Pointing Losses', ...
'Data Rate Losses', ...
'Free Space Losses', ...
'Link Margin' ...
};
t = uitable('Parent',f,'Data',dat,'ColumnName',cnames,...
'RowName',rnames,'Position',[800 300 470 330]);
hold off

~ 50 ~
Link Budget Function - Kurt Zeller
function [P_trans,Channel_Cap,L_atm,
FSPL,L_p,LL,L_point,G_trans,G_rec,Data_loss] = ...
Transmit_Power_Required(freq, Eb_N0,...
trans_diam, trans_ata, trans_type, reciever, reciever_type,
rec_ata, atm_Y_N,L_z,...
elev_ang_deg, BW, T_trans, data_rate, Distance)
c = 299792458; %m/s
kb = 1.38 * 10^-23; %J/K
% s/c parabolic antenna gain
if strcmp(trans_type,'O') == 1
G_trans = 5;
else
g_trans = (pi*trans_diam*freq/c)^2 * trans_ata; %W
G_trans = 10*log10(g_trans); %dB
end
% line losses for A120-FP
% VSWR of 1.3 corresponds to .075 dB
IL = .075; %dB
Length = .5; %m
LL = Length*.65 + IL; %dB
ll = 10^(.1*LL); %power in/power out for line
% Reciever parabolic gain
if strcmp(reciever_type,'D') == 1
g_rec = (pi*reciever*freq/c)^2 * rec_ata; %W
G_rec = 10*log10(g_rec); %dB
% Reciever system noise temperature cited as 92K
T0 = 290; %K
Tr = 90; %K
fig = 1+ Tr/T0; %Figure of noise
%System noise temperature use Eq from SMAD pg 558 (13.3)
% Ts = T_trans + (T0*(1-ll)/ll) + (T0*(fig-1)/ll); %K
Ts = T_trans;
else
Ts = 1; %ignores temperature
G_rec = reciever; % Gain/Temp [dB]
end
%atmospheric loss
% (add extra 2 dB for rain)
if strcmp(atm_Y_N,'Y') == 1
%dB/km
%min elevation angle deg
t_trop = 20; %km
L_atm = L_z*cscd(elev_ang_deg)*t_trop + 8; %dB
else
L_atm = 0;
end

~ 51 ~
% overestimate polarization loss ( SMAD says .3)
L_p = 3; %dB
% noise recieved by ground station
T_space = 10; %K
n = kb*T_space*BW; %W
%Assume pointing losses
L_point = 3; %dB
% free space losses by altitude
FSPL = 10*log10(( (4*pi*1000*Distance*freq)/c )^2); %W
Data_loss = 10*log10(data_rate);
P_trans = Eb_N0 + FSPL - G_trans + L_p + L_point - 228.6 ...
- G_rec + 10*log10(Ts) + L_atm + Data_loss; %
C_N = Eb_N0 + 10*log10(data_rate) - 10*log10(BW) ;
Channel_Cap = BW*log2(1 + C_N);
end

ANGELS Communications by Kurt Zeller

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