This document provides an overview of RF control products, specifically RF switches and RF attenuators. It begins with an introduction to RF control products and their applications. It then discusses RF switches in more detail, covering naming conventions, technologies, characteristics like isolation and power handling, and application considerations. RF attenuators are also discussed, including fixed attenuators, digitally-controlled attenuators, and analog attenuators. Example applications of RF switches and attenuators in signal routing and level control are provided. New RF switch and attenuator products are highlighted at the end.

1. MARKET TRAINING MODULE
RF Control Products

2. List of Content
► Introduction
► RF Switches
► RF Attenuators
2

3. Introduction
► Control Products are defined as impacting the signal chain performance
 By configuring the Chain
 By adjusting the signal level
 NOT amplifying or converting the signal (i.e. ideally linear and passive)
 Operating Frequency above 1GHz to close to 100GHz
► RF Switches (SPST, SPDT, SP3T, SP4T, etc.)
► RF Attenuators (Digital, i.e. DAT, Analog)
► TX/RX Switches
3
15dB
24dB9dB
1.9-
2.34GHz
1.25-
1.8GHz
1.8-
2.5GHz
870-
1250MHz
2.5-
3.4GHz
600-
870MHz
450-
600MHz
3.4-
5GHz
10-
450MHz
176
8
250
0
125
0
353
6
88
4
625a
500
0
625
b

4. Application and Marketing Considerations
►ALL RF Systems/PCB include RF Switches and often RF
Attenuators
 Some systems (PCB) have 30 to 50 RF switches and few attenuators
 Examples:
 Inserting a calibration signal in the Signal Chain
 Bypassing fixed-gain amplifiers
 Routing a signal to different (frequencies) downconversion chains
 Routing an LO signal thru alternative frequency selective gains, before the
mixer
 Optimizing the RF signal level for best noise performance, after a fixed gain
stage (LNA) or between fixed gain stages
4

5. RF Control Product: Common Basic Knowledge
► RF Devices, packaged for PCB usage
► RF “Connectorized” Components, to be used as stand alone
► Passive, i.e. always have a transfer attenuation
► RF Switches key function is to route Signals to different Signal Chains
► RF Attenuators key function is to maintain the RF Signal Levels to the
planned ranges for best system performance
► Controlled Signals are
 Information signal (receive, transmit)
 Clocks, Local Oscillators
5

6. RF Switches

7. RF Switches: Naming
► Single Pole Single Throw (SPST)
► Single Pole Dual Throw (SPDT)
► Single Pole “X” Throw (SPXT)
► Notes
 Double Pole (e.g. in a DPDT) normally called “Differential”
 RF circuits are normally single ended
7
(Ex: SP8T)

8. RF Switches: Grouping
► Electromechanical (EM) switches
 Lower Reliability and Life Time
 High Electrical Performance (after switching transitions)
► Solid State (SS) switches
 High Reliability and Life Time
 Good Electrical and Switching Performances
► Micro-Electro Mechanical switches (MEMS)
 Promising both EM and SS like characteristics
 Lower Operating frequencies than SS
 Part of ADI IP
8

9. RF Solid State Switches: technological options
► FET-based switches
 GaAs – Fast, High Frequency capability (100Hz), less robust (ESD)
 Silicon – getting faster, good settling time, med Frequency (20-40GHz), robust
► Pin Diode switches
 High frequency (100GHz), robust, difficult to drive/control
► Hybrid (FET and Pin Diode)
 Combination of both the above
 May not allow a monolithic solution
9

10. RF Switches: System Level Characteristics 1 of 2
► Architecture
 Absorptive – includes a matched impedance (Typically 50 Ohms) on
the input when the switch is open, so the circuit driving the input will
see a matched impedance at all times (across the operating
frequency range)
 Reflective – has no matched impedance when open, so the driving
circuit needs to be able to handle the reflected waves and power
► Control Signals (FET)
 Direct Control and low power control signals
 May suffer from RC delay
 May require negative voltage control signals to operate the switch
► Power Supplies
 Need most often to have both polarities supply voltage
 The negative supply voltage can be internally generate, at the
expense of a higher system noise, from the integrated charge pump
10

11. RF Switches: System Level Characteristics 2 of 2
► DC coupling
 ALL Traditional RF switches do not like DC signal through them
 DC decoupling caps are needed, unless a 0Vdc can be guaranteed
 Decoupling Caps will impact the low frequency performance
 New Technology in development with DC handling capability
► Power consumption
 Low static power consumption (100-300uA)
► Reliability (SS)
 Highest among available technologies
 GaAs switches have low ESD threshold, requiring specific care
11

12. RF Switches: Electrical Characteristics
► Frequency Range (from 1-2GHz to 80GHz+)
► Insertion Loss (normally lower than 0.5dB, or max 1dB)
► Return Loss (normally higher than 10-15dB)
► Power Handling (the higher the better, now around 30dBm, moving to
40dBm+)
► Isolation (normally in the 25-50dB, frequency dependent)
► Distortion/Linearity (normally high, above 50dBm)
► Switching Speed (from 10ns to 1us depending on used processed, GaAs
is faster, Si is slower)
► Settling Time (from 100ns to 5us depending on the fabrication process
used, Si is slower, but has a shorter settling time)
► Noise (Leakage, switching)
12

13. Operating Frequency Range – Insertion Loss (IL), Return
Loss (RL)
► Frequency Range is commonly the FIRST selection criteria for
switches
► Insertion Loss is mostly impacted by
 The switch’s direct intrinsic resistance
 Reflected Loss as of the switch resistance
 Leakage paths, which reduce the useful signal power to the load
 IL must be compensated for by other circuits or taken into account
when performing level planning (as it impacts noise performance)
► Frequency dependent IL
 Low Frequency IL is affected by
 Any decoupling Cap at the In/Out leads
 Power handling (see later) capability
 High Frequency IL is affected by
 Intrinsic parasitic capacitances
 In band IL variation is affected by
 Return Loss, caused by impedance mismatching
► Return Loss (RL)
 Indicates the amount of power not transferred over the switch (but
reflected back)
 Depends on the impedance matching (50OHM) of the switch with
the externally connected devices
13
Return Loss
Insertion Loss

14. Signal Power Handling and Distortion
► Switch capability to handle high power signals
 Allows to deploy switches closer to the system RF
connectors
 Decreases at lower frequencies, as limited by process
technology and switch architecture
 Defined while the switch is static or switching (Hot
switching power)
 Described by P1dB (or PSAT)
► Distortion
 Measured by IP3
 Related with Power handling
 Approaching P1dB non linearity increases (IP3 decreases)
 Normally the Switch is not the critical Signal Chain block
on distortion
14
Power De-rating compared to the
required nominal power
the switch can operate at
IP3
Decrease at low frequencies

15. Switching Speed & Settling Time
► Switching Speed (or Time) – Time from 50%
of switching control Input to 90% of the RF
signal out.
► Settling Time – Referred to the time the RF
signal has set to 0.05dB or 0.01dB from its final
time
 Settling Time is a particular challenge for GaAs
switches
15
Switching
Time

16. Isolation
► Signal going through the switch when it is OFF
 From the common I/O to any other port
 Between two different ports
► Normally NOT the coupled noise from the control
ports (see later)
► FET switches have very high low frequency
isolation
 Drain-Source Cap is limiting high frequency
isolation
 This can be improved by shunting the input port to
ground when the switch is open (implemented
inside the switch itself)
► Pin Diode Switches have good high-frequency
isolation (and poor isolation at low frequencies)
16
RF1
RF2
RFC

17. Other Noise and Sources of Interference
► Video leakage or feedthrough
 Describes the noise from the control ports to the
RF ports
 Normally measured when no RF is present
(reported in mV)
 Lower in FET switches
 Critical is some applications (for example when a
high gain AGC amplifier follows the switch)
► Power Supply Noise
 From external supplies – to be managed by proper
filtering
 From internal bias voltages (normally negative)
generated by an integrated charge pump
 Typically avoided by high end applications (T&M)
17

18. RF Switches - Application Topics
► RF Ports Coupling - Traditional RF switches are not taking any DC signal
 Requiring DC decoupling at the ports.
 Impacting the IL at low frequencies. Proper selections of the Caps would depended on the
desired low frequency performances.
 Decoupling Caps can be avoided if the operating signals have no DC component (this is
mentioned often in datasheets as “not needing any decoupling Cap”!!!)
► Power Supplies
 Switches can operate from single supply or from dual supplies
 A competitor has integrated the Vneg supply, with the related system noise drawback
► Power Handling
 A critical system parameter, in many application, as the switch might need to be protected,
especially at low frequencies (below 10-100MHz)
 Improved handling is achieve with Si based switches
► Control Signals – voltage ranges, drive
 Control voltage polarity depends on the switch supplies, and can be also negative voltages
 Latest switches operate with positive voltages (compatible with standard logic levels), and have
bipolar supplies
 Solid state switches are easy to drive (unlike some PIN Diode based switches)
18

19. RF Attenuators

20. RF Attenuator Typicales
► Fixed Attenuators (“Pads”)
► Digitally-Controlled Attenuators (DAT)
 Serial or parallel Control
 Series of switched-in/out fixed attenuators
 Resolution from 1bit to 7bit
► Analog (Voltage) Controlled Attenuators (VVA)
 More complex control architecture
 Preferred when in AGC loops or for high signal
level accuracy
20

21. RF Attenuators: WHY?
► Key justification for Attenuators
 Achieve a more optimized signal level plan (for noise and distortion)
 RF amplifiers have commonly fixed gain
 RF amplifiers may not like high power input signals
21
G G
A A
Input range Pin:
From Pout-G+A
To Pout-G
Desired Output
Range: Pout
Signal Chain SNR
Improved by G-NF-IL
Max PinMax Pin=Pin+A

22. RF Attenuators: Main and Common to the RF switches
Electrical Characteristics
► Frequency Range: Operating Frequency Range
► Attenuation Range: discrete or continuous
► Attenuation Resolution (DAT): minimum nominal attenuation step, in dB. Related to the bit count and
Attenuation Range
 E.G., 32dB range, 6 control bits (64 levels) gives 0.5dB resolution, to a max attenuation of 31.5dB (0dB attenuation
included)
► Attenuation Accuracy: nominal accuracy. Normally reported across frequency and attenuation range
► Insertion Loss: Attenuation across the device, when 0dB is selected (ideally no attenuation applied)
► Return Loss: reflected Power at the Input/Output ports, related to the device impedance matching
► Power Handling (P1dB, P0.1dB): maximum input signal power, the device can handle and keep operating
linearly. Normally reported across the frequency range.
► Distortion/Linearity (IIP3): see RF Switch description, normally reported across the attenuation range
► Switching Speed: see RF Switch description
► Settling Time: see RF Switch description, normally reported across the attenuation range
► Overshoot Free DAT: the Attenuator output presents no overshooting voltage, when switching between any
attenuation steps, as a consequence of how the internal attenuation switches are operated
► Power Supplies, Control Voltages: see RF Switch description
22

23. RF Attenuators: State Error
Absolute Attenuation Error at each attenuation level, across the frequency
and attenuation range
23

24. RF Attenuators: Step Error
Relative Attenuation Error at each attenuation level, across the frequency
and attenuation range
24

25. RF Attenuators: Phase Variation
Relative Phase variation from the output to the input signal, as it goes
through the different internal attenuation steps
 Normally reported as max value, across the frequency and attenuation range
 Also reported as graph
25

26. Analog Attenuators (VVA)
• Similar Function as with VGA, but
implemented with an Attenuator (as
“programmable wideband RF Amplifiers
are rare”).
• Key technical challenges
• Maintain Insertion Loss and Return Loss
performances in the attenuation range, across
frequency range
• Linear relationship with the control voltages
• Simplify control circuitry
26
Reference Attenuator Circuit
Discrete Control CircuitPlease see Ref.4 from the Reference List

27. Application Examples
27

28. 28
LO Generation
LPF
LPF
LPF
SP3T
Test In
LO
Fout
SP4T
• Remove Spurious and Harmonics
• High Insertion loss (6dB+)
• Could be Band Pass on selected Paths
Brings LO level to Max allowed
And desired by the follow-on
Circuit (eg mixer)
• Amplifies Fout
• Isolates Fout from downchain
• May be omitted, with certain Fout
Critical Parameters
• Low insertion Loss
• High Return Loss
• High Linearity
End Application Dependent
• Low video Leakage
• Fast Switching/Settling
• Power Handling
Non Critical Parameters
• Isolation

29. 29
RF Input Stage
DAT
G1
G2
LNA
IL, RL impacts SNR Sets the signal level
IP3 impacts
System linearity
Input Protections
Required for high Pin
IN
Test in
Or TX
OUT
SW1
SW2
SW3 SW4 SW5

30. HMC1118LP3DE 9KHz-13GHz SPDT (New Product)
High Isolation Silicon Switch
► Features
 Non-Reflective 50 Ω Topology
 Wideband solution with excellent Isolation 56dB @8GHz
 Fast 0.1dB Settling Time of 7.5us(Critical for T&M apps)
 Optimized for Low Frequency operation down to 9KHz
 No DC Blocking Cap is required on RF pins.
 Flat Insertion Loss across Frequency : Less than 0.2dB
variation up to 9GHz.
 High Input IP3: +62 dBm @ 3.0 GHz
 Optimum for High power apps: High P1dB: >+37dBm
 High Power Handling: +36dBm through, +27dBm
terminated/hot-switching
 Positive Control, 0/+3.3 V
 Excellent ESD Rating: 2 kV HBM
 RoHS Compliant 3x3 mm 16 Lead QFN Package
► Device Pin-out
30
► Electrical Specification
► Availability
 Loose parts abd evaluation boards available, pre-production
 Full production and general availability Q3’2015
Parameter Spec Units
Frequency Range 9 kHz - 13.0 GHz
Insertion Loss @ 0.1 GHz 0.45 dB
Insertion Loss @ 8.0 GHz 0.60 dB
Insertion Loss @ 10.0 GHz 0.90 dB
Isolation @ 0.1 GHz 81 dB
Isolation @ 8.0 GHz 56 dB
Isolation @ 10.0 GHz 35 dB
Input P1dB @ 3.0 GHz +37 dBm
Input IP3 @ 3.0 GHz 62 dBm
Switching Speed 2.7 μs
Settling Time 0.1dB 7.5 μs
Settling Time 0.01dB 12 μs
Bias Voltage VDD +3.3 V
Bias Voltage VSS -2.5 V
ESD Rating Class 2 (2kV) HBM

31. 31
HMC1119LP4E 0.1-6GHz 0.25dB LSB 7-bit (New Product)
Overshoot Free Digital Attenuator
► Features
 7-bit 0.25 dB LSB Steps to 31.75 dB
 High Input IP3: +55 dBm
 Overshoot Free Operation
 Low insertion loss of 1.2dB @2GHz
 Typicalical step error of ±0.2dB
 TTL/CMOS compatible contol interface
 High ESD robustnest of 2KV HBM
 Single +3.3V to +5V supply
 RoHs 4x4mm SMT compliant package
► Device Pin-Out
► Availability
 Loose parts and evaluation boards available. X-Grade production.
 Full production and general availability Q3’15
► Electrical Specification
Parameter Spec Units
Frequency Range 0.1 – 6.0 GHz
Atenuation Resolution (LSB) 0.25 dB
Attenuation Accuracy : ± 0.25 (3%) dB
Insertion Loss @ 0.1 GHz 1 dB
Insertion Loss @ 2 GHz 1.2 dB
Insertion Loss @ 4 GHz 1.7 dB
Phase var. over attenuation range @ 2 GHz 16 deg
P0.1dB @ 0.1 GHz 32 dBm
P0.1dB @ 4 GHz 32 dBm
Input IP3 @ 0.1 GHz 55 dBm
Input IP3 @ 4 GHz 52 dBm
Input Return Loss < 6 GHz 17 dB
Output Return Loss < 6GHz 18 dB
Supply Voltage +3.3 to +5 V
Control Interface Ser./ Par -
Control Voltage 0/3.3 or 0/5 V
Switching Speed
tRise, tFall (10 / 90% RF)
tON , tOFF (50% LE to 10 / 90% RF)
270/190
320/210
ns
ESD Rating Class2 (2kV) HBM

32. Bibliography
1. Agilent Technologies, “Understanding RF/Microwave Solid State
Switches and their Applications”,
http://cp.literature.agilent.com/litweb/pdf/5989-7618EN.pdf
2. D. Fischer, R. Lourens, P. Bacon, “Overview of RF Switch Technology
and Applications”, Microwave Journal, July 2014
3. National Instruments, “Complete Switching Tutorial”,
http://www.ni.com/tutorial/3118/en/
4. “Designing with the HMC346MS8G Voltage Variable Attenuator”, Hittite
Microwave, Product Note
5. Gary Breed, “A Review of RF/Microwave Switching technologies”, High
Frequency Electronics, May 2010, pag.70
32

33. END
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