This document discusses various factors that can affect LTE transmitter performance metrics like output power, EVM, and ACLR. It provides details on LTE and WCDMA output power specifications, key modulation schemes, and how higher order modulations can increase PAR and require more power back-off. It also examines how the feedback receiver (FBRX) method impacts output power control in LTE systems and provides lessons learned from various power issues encountered. Regarding EVM, it analyzes the effects of local oscillator phase noise, crystal oscillators, VCO pulling, and OFDM sensitivity to phase errors. Shielding and isolation techniques are also discussed.
Sensitivity or selectivity - How does eLNA impact the receriver performancecriterion123
it describes
1. Why need external LNA ?
2. Why does poor linearity lead to poor sensitivity ?
3. For the eLNA gain, the more the better ?
4. Why can SAW filter improve linearity ?
System(board level) noise figure analysis and optimizationcriterion123
For sensitivity, what a system (board level) RF engineer can improve is only noise figure. This document describes that the noise figure concept you should know, and how to optimize it to improve sensitivity.
Sensitivity or selectivity - How does eLNA impact the receriver performancecriterion123
it describes
1. Why need external LNA ?
2. Why does poor linearity lead to poor sensitivity ?
3. For the eLNA gain, the more the better ?
4. Why can SAW filter improve linearity ?
System(board level) noise figure analysis and optimizationcriterion123
For sensitivity, what a system (board level) RF engineer can improve is only noise figure. This document describes that the noise figure concept you should know, and how to optimize it to improve sensitivity.
Why to do single-tone desense test ?
What is cross modulation ?
what's the difference between cross modulation and intermodulation ?
what is triple beat ?
desence,sensitivity calculation with and without external LNA, Noise figure calculation with and without external LNA and IIP3 calculation with and without external LNA
Introduction to differential signal -For RF and EMC engineercriterion123
It describes :
1. What is the advantages of differential signal
2. What should you pay attention to differential signal
3. What should you pay attention to the bend of differential
signal
4. What should you pay attention to the EMI filter
5. What should you pay attention to ground plane
6. What should you pay attention to loop area
Why to do single-tone desense test ?
What is cross modulation ?
what's the difference between cross modulation and intermodulation ?
what is triple beat ?
desence,sensitivity calculation with and without external LNA, Noise figure calculation with and without external LNA and IIP3 calculation with and without external LNA
Introduction to differential signal -For RF and EMC engineercriterion123
It describes :
1. What is the advantages of differential signal
2. What should you pay attention to differential signal
3. What should you pay attention to the bend of differential
signal
4. What should you pay attention to the EMI filter
5. What should you pay attention to ground plane
6. What should you pay attention to loop area
Review on Design and Performance Analysis of Low Power Transceiver Circuit in...iosrjce
IOSR Journal of Electronics and Communication Engineering(IOSR-JECE) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of electronics and communication engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in electronics and communication engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Mixed Linearity Improvement Techniques for Ultra-wideband Low Noise Amplifier IJECEIAES
We present the linearization of an ultra-wideband low noise amplifier (UWB-LNA) operating from 2GHz to 11GHz through combining two linearization methods. The used linearization techniques are the combination of post-distortion cancellation and derivative-superposition linearization methods. The linearized UWB-LNA shows an improved linearity (IIP3) of +12dBm, a minimum noise figure (NF ) of 3.6dB, input and output insertion losses (S 11 and S 22 min. ) below -9dB over the entire working bandwidth, midband gain of 6dB at 5.8GHz, and overall circuit power consumption of 24mW supplied from a 1.5V voltage source. Both UWB-LNA and linearized UWB-LNA designs are verified and simulated with ADS2016.01 software using BSIM3v3 TSMC 180nm CMOS model files. In addition, the linearized UWB-LNA performance is compared with other recent state-of-the-art LNAs.
Design of 10 to 12 GHz Low Noise Amplifier for Ultrawideband (UWB) SystemIJECEIAES
Balanced amplifier is the structure proposed in this article, it provides better performance. In fact, the single amplifier meets the specification for noise figure and gain but fails to meet the return loss specification due to the large mis-matches on the input & outputs. To overcome this problem one solution is to use balanced amplifier topography. In this paper, a wide-band and highgain microwave balanced amplifier constituted with branch line coupler circuit is proposed. The amplifier is unconditionally stable in the band [9-13] GHz where the gain is about 20dB. The input reflection (S11) and output return loss (S22) at 11 GHz are -33.4dB and -33.5dB respectively.
CDMA 1x Introduction to Power Control Issue2.1Tempus Telcosys
One of the aims of the CDMA1X system is to maximize the number of its users. If each mobile station (MS) adjusts its transmitter power to minimize the signal noise received by the base transceiver station (BTS), the capacity of the system is maximized. Higher power brings higher interference and results in more capacity loss. Power control can adjust the transmission power of the MS and BTS, aiming to minimize the interference
After learning this course, you will learn the following:
The importance of the power control of the CDMA system
Categories and calculating theories of the power control
Data configuration of the power control
Chapter 1 Goals and Principles of Power Control
Chapter 2 Categories and Arithmetic of Power Control
Chapter 3 Data Configuration of Power Control
Each couple of customers is in a same room.
Each couple of customers speaks a language different from that spoken by other couples.
If the noise becomes louder, all the customers will raise their voices.
If the noise is too louder, the customers may go to other rooms.
The customer who speaks too loudly will affect the communication of others.
The transmission power of the control BTS and MS must ensure that the signal sent to the receiver through the complicated radio space can meet the threshold of correct demodulation.
When the first principle is satisfied, the transmission power of the BTS and MS is required to be lowered as much as possible to decrease the interference between users and best optimize the network performance.
The transmission power of the MS near the BTS is lower than that of the MS far from the BTS and of the MS in the fading areas.
3 g interview question & answer by telsol360Tel sol
3G (WCDMA) Interview Question and answer asked by Top recruiters like NSN global and Ericsson global.
Prepare yourself for the Interview by the help this Documents specially designed by Telsol360 technical team .
DESIGN AND ANALYSIS OF 2 GHz 130nm CMOS CASCODE LOW NOISE AMPLIFIER WITH INTE...csijjournal
This work, illustrates the development of 2 GHz Low Noise Amplifier (LNA) interfaced with square truncated edge-fed right circularly polarized patch antenna. The LNA is simulated on Agilent ADS platform with TSMC 130nm RF CMOS process. The development of cascode amplifier and its optimization has been further exemplified. The developed LNA is tuned for 2 GHz and the performance is tuned for high stability factor of 4, Gain of 19 dB which is essential for any mobile device, Noise Figure (NF) of 1.15 dB with a P1dB point at -9 dBm. Further a truncated patch antenna with right circular polarization has been simulated on EMpro. The antenna has a gain of 6.1 dB in the azimuth plane. The simulated system can be further integrated to form the RF front end of TDD2000 LTE standard mobile device.
A 28 GHz 0.18-μm CMOS cascade power amplifier with reverse body bias techniqueTELKOMNIKA JOURNAL
A 28 GHz power amplifier (PA) using CMOS 0.18 μm Silterra process technology is reported. The cascade configuration has been adopted to obtain high Power Added Efficiency (PAE). To achieve low power consumption, the input stage adopts reverse body bias technique. The simulation results show that the proposed PA consumes 32.03mW and power gain (S21) of 9.51 dB is achieved at 28 GHz. The PA achieves saturated power (Psat) of 11.10 dBm and maximum PAE of 16.55% with output 1-dB compression point (OP1dB) 8.44 dBm. These results demonstrate the proposed power amplifier architecture is suitable for 5G applications.
Similar to Performance requirement and lessons learnt of LTE terminal---transmitter part (20)
NO1 Uk best vashikaran specialist in delhi vashikaran baba near me online vas...Amil Baba Dawood bangali
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CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
4. By Criterion 4
Specification
The LTE specified maximum output power:23 dBm with a
tolerance of ± 2 dB [1,6]. Nevertheless, the WCDMA specified
24 dBm with a tolerance of +1/−3 dB [1].
5. By Criterion 5
key parameters
The overall LTE key parameters are shown below [2]:
6. By Criterion
bits per symbol
LTE uses QPSK, 16 QAM, and 64 QAM for uplink
transmission, whereas WCDMA makes use of BPSK for
uplink transmission. The overall bits per symbol table for
these modulation types is summarized as below [3]:
8. By Criterion
PAR (Peak -to-Average-Ratio)
Higher order modulation achieves higher data rate at the
expense of higher PAR (Peak -to-Average-Ratio), which
requires more back-off to retain linearity [1,5].
9. By Criterion
PAR (Peak -to-Average-Ratio)
Hence, there are average power and peak power on the
display simultaneously.
10. By Criterion
PAR (Peak -to-Average-Ratio)
SC-FDMA is used for LTE uplink transmission to reduce PAR
[5]. Nevertheless, LTE still has higher PAR in uplink
modulation than WCDMA[1]. Thus, that’s why maximum
output power of LTE is 23 dBm, but 24 dBm of WCDMA.
11. By Criterion
MPR (Maximum Power Reduction)
Furthermore, MPR (Maximum Power Reduction) has been
introduced in LTE to take account of the higher PAR of 16-
QAM modulation and RB (Resource Block) allocation [1,6].
That’s why the output power is lower under full RBs.
12. By Criterion
Headroom
LTE power control ranges from -40 dBm to 23 dBm. [1]
Take SKYWORKS SKY77645-11 for example, its maximum
power in LTE B7 is 28.5 dBm, which indicates the MMPA post-
loss should be less than 5.5 dB.
Of course, the post-loss is the smaller the better since more
headroom leads to better linearity.
13. By Criterion
Headroom
Moreover, the output power is relevant for temperature and
voltage, so the compensation should be done to ensure
consistent output power under various conditions.
The worst case is (low temperature + high voltage), which
makes output power rise dramatically, thereby aggravating
TX performance.
14. By Criterion
Headroom
As shown below, the saturated power for low gain mode is
26.9 dBm, and which for high gain mode is 29 dBm. In other
words, both low gain mode and high gain mode can achieve
23 dBm. Nevertheless, high gain mode has more headroom
(29 dBm – 23 dBm = 6 dB) than low gain mode (26.9 dBm – 23
dBm = 3.9 dB). So incorrect gain mode also causes linearity
issues, such as EVM.
15. By Criterion
FBRX
As for power control, Qualcomm makes use of FBRX
(Feedback Receiver) method:
16. By Criterion
FBRX
The output power is usually coupled back to transceiver by
means of the coupler integrated in ASM (Antenna Switch
Module). Take SKYWORKS SKY77912-11 for example [9]
Thus, the overall process is closed loop, thereby adjusting
output power by the feedback power to retain accuracy.
17. By Criterion
Lesson learnt_1: B28 Minimum power issue
While doing minimum power measurement, B27 can achieve
the power level less than -30 dBm, but B28 can NOT.
B27/B28 share the identical transmitting path. In other words,
the issue is not due to hardware issue since B27 is normal.
18. By Criterion
Lesson learnt_1: B28 Minimum power issue
While doing calibration, with the identical RGI (RF Gain
Index), there is approximately 10 dB gap between B27 and
B28, as shown below [10]:
19. By Criterion
Lesson learnt_1: B28 Minimum power issue
Nevertheless, with the same RGI, there is no difference
between B27 and B28 output power at transceiver output port.
This indicates that the issue is not related to transceiver.
20. By Criterion
Lesson learnt_1: B28 Minimum power issue
As shown below, B27 and B28 should be configured LB and
VLB respectively. Otherwise, there may be something wrong
in transmitting performance, such as minimum power. So the
root cause is incorrect configuration for B28.
21. By Criterion
Lesson learnt_2: Band 2 low channel Max power
As shown below, while doing B2 maximum power
measurement, it’s too high in low channel, but normal in mid
and high channels.
From calibration log, it is apparent that the low channels
have lower HDET (High Power Detector) value than mid and
high ones.
22. By Criterion
Lesson learnt_2: Band 2 low channel Max power
As shown below, the measured maximum power at connector
should be 23 dBm. We assume the loss of duplexer is
approximately 3 dB, so the output power at MMPA is 26 dBm.
Because the coupler is integrated into MMPA and the
coupling factor is 23 dB, the feedback power is 3 dBm, which
is higher than the handling capacity of feedback LNA
23. By Criterion
Lesson learnt_2: Band 2 low channel Max power
As shown below, with a strong input signal, the gain of LNA
reduces [11]. That’s why the low channels have lower HDET
value than mid and high ones.
24. By Criterion
Lesson learnt_2: Band 2 low channel Max power
As for mid and high channels, perhaps the frequency
response of FBRX path is as shown below:
Thus, thanks to higher path loss, the feedback power doesn’t
make feedback LNA saturate in mid and high channels. This
explains why HDET value increases as channel number
increases reasonably.
25. By Criterion
Lesson learnt_2: Band 2 low channel Max power
Thanks to lower HDET value in low channels, the baseband
block misunderstands that the output power is too low,
thereby increasing RGI and resulting in too high output
power in low channels. Therefore. In modern LTE terminal
design, the coupler is integrated into ASM, instead of MMPA.
So the root cause is too high feedback power in low channel.
26. By Criterion
Lesson learnt_3: All bands too high maximum power
During factory manufacturing phase, one board failed thanks
to too large power. Compared to good board, the value of
stored NV item (FBRX_Gain_Value) is larger than good board.
27. By Criterion
Lesson learnt_3: All bands too high maximum power
Since there is soldering issue in DC block, thereby resulting
in large loss in FBRX path. With weak input signal, the LNA
switches to high gain mode to lower the overall noise figure
to achieve acceptable BER. Additionally, the baseband block
misunderstands that the output power is too low, thereby
increasing RGI and resulting in too high output power.
So the root cause is too low feedback power
in all channels.
28. By Criterion
Lesson learnt_4: Band 38 too high maximum power
As shown below, B38 and B41 share the same transmitting
path, but the maximum output power of B38 is higher than
B41 approximately 2 dB.
29. By Criterion
Lesson learnt_4: Band 38 too high maximum power
From calibration log, B38 has lower calibration power than
B41. Thus, this issue is related to FBRX.
30. By Criterion
Lesson learnt_4: Band 38 too high maximum power
Check the coupler configuration, B38 is configured LB
instead of HB. As shown below, the coupler has larger
coupling factor in LB (27 dB) than in HB (22 dB).
31. By Criterion
Lesson learnt_4: Band 38 too high maximum power
It means that B38 has larger loss in FBRX path than B41.
With weak input signal, the baseband block misunderstands
that the output power is too low, thereby increasing RGI and
resulting in too high output power in B38.
32. By Criterion
Lesson learnt_4: Band 38 too high maximum power
Similarly, if B5 is configured HB, as shown below:
Since the coupling factor of HB is less than LB approximately
5 dB, the B5 feedback power will be higher than expectation,
thereby making feed-back LNA saturate. With low output
power level from feed-back LNA(due to gain reduction), the
baseband block may misunderstand the output power is too
low, thereby increasing RGI and resulting in too high output
power.
34. By Criterion
Lesson learnt_5: Band 7 too high maximum power
The impedance may alter while the shielding cover is on the
co-planar ground since the medium is already NOT air.
35. By Criterion
Lesson learnt_5: Band 7 too high maximum power
B7 is high band, which is more sensitive to impedance
variation than mid- and low bands. Thus, the impedance
mismatch in FBRX path results in high mismatch loss,
thereby leading to too high power due to compensation
mechanism.
Because FBRX affects numerous bands, please lay the trace
in inner layer to obtain better protection. Otherwise, output
power, EVM, and ILPC (Inner Loop Power Control) may fail.
36. By Criterion
Lesson learnt_6: LTE B40 high channel too low max power
As mentioned earlier, for the output power, the compensation
should be done to ensure consistent output power under
various temperature and frequency. Similarly, compensation
should also be done properly for FBRX because this affects
output power.
37. By Criterion
Lesson learnt_6: LTE B40 high channel too low max power
As shown below, the FBRX high channel compensation is
exceeding other channels, thereby making baseband block
misunderstand the output power is too high.
Thanks to compensation mechanism,
the RGI will become lower, thereby causing
too low output power.
Similarly, if the compensation is much less
than other channels, the baseband block
may misunderstand the output power is
too low. Thanks to compensation mechanism,
the RGI will become higher, thereby causing
too high output power.
38. By Criterion
How does FBRX affect output power?
Hence, these aforementioned power issues tell us that :
Too much loss in FBRX path => Too high output power
Too high feedback power => Too high output power
Exceeding compensation in FBRX => Too low output power
Insufficient compensation in FBRX => Too high outputpower
In terms of hardware, check FBRX whenever output power is
too high.
42. By Criterion 42
Introduction
EVM is a vector in the I-Q plane between the ideal
constellation point and the practical point received by the
receiver. In other words, it is the difference between actual
received symbols and ideal symbols. EVM is low if the
actual received symbols are very close to ideal symbols,
and vice versa.
In time domain, the timing error in waveform is called “jitter”,
which generates phase error in the modulation constellation,
thereby contributing to EVM [1].
43. By Criterion 43
Phase Noise
Let’s look at the effect of LO phase noise from another point
of view.
According to this relationship [12], it is apparent that the
EVM is inversely proportional to SNR. As shown below, a LO
with high phase noise leads to the reduction in RF signal
SNR, thereby aggravating EVM performance.
44. By Criterion 44
Phase Noise
As shown below, take Qualcomm WTR4905 for example, the
crystal generates a 19.2 MHz sine waveform to produce a
19.2 MHz square-wave XO signal from PMIC to transceiver
[13]. Thus, a crystal with high phase noise contributes to the
phase noise of LO
45. By Criterion 45
Crystal Oscillator
Nevertheless, cellular technology usually shares one
identical crystal with GPS technology. If GPS performance is
acceptable (i.e., CNR = 38 ~ 40 dB), it indicates that the
crystal is innocent since GPS performance is more sensitive
to crystal performance thanks to its extremely weak
received signal. Poor EVM
Poor GPS CNR ?
Check XO
XO is innocent
Yes
No
46. By Criterion 46
Crystal Oscillator
The digital square-wave signals would corrupt analog sine-
wave signal; sufficient isolation is highly recommended [13].
The layout shown below is a bad example since the isolation
is not enough.
47. By Criterion 47
VCO
Furthermore, keep-out areas on PCB top layer is necessary
for transceiver since these areas is related to VCO, which is
sensitive to parasitic effect. Otherwise, the parasitic effect
may aggravate VCO phase noise [13, 30].
48. By Criterion 48
OFDM
LTE makes use of OFDM (Orthogonal Frequency Division
Multiplexing) modulation [5], which is sensitive to phase
error and/or frequency offset [14].
49. By Criterion 49
VCO Pulling
As shown below, in direct-conversion transmitter
architecture, perhaps an appreciable fraction of the PA
output couples to the LO trough substrate, and PCB traces
etc. [16].
50. By Criterion 50
VCO Pulling
With the presence of injection pulling, the LO output
waveform is as shown below [16]:
51. By Criterion 51
VCO Pulling
As mentioned earlier, the timing error in waveform generates
phase error in the modulation constellation, thereby
contributing to EVM, and OFDM modulation is sensitive to
phase error. Thus, for a LTE system, especially direct-
conversion transceiver architecture (since RF frequency
almost equals to LO frequency), oscillator pulling should be
avoided.
52. By Criterion 52
Lesson learnt_7: EVM issue due to shielding can
As shown below, if someone presses the shielding can with
finger, the EVM performance is good, and vice versa.
53. By Criterion 53
Lesson learnt_7: EVM issue due to shielding can
That’s because PA and transceiver blocks are placed in the
identical shielding space. The PA couples its strong RF
energy onto the shielding can. An appreciable fraction of the
PA output couples to the VCO trough shielding can by
means of reflection, thereby making VCO pulling happen
and aggravating EVM performance [13,18].
54. By Criterion 54
Lesson learnt_7: EVM issue due to shielding can
Nevertheless, if someone presses the shielding can, this
action reinforces the grounding of the shielding can, thereby
eliminating reflection and VCO pulling [13].
55. By Criterion 55
Lesson learnt_7: EVM issue due to shielding can
Thus, the PA and transceiver blocks should be placed in
separated shielding areas individually to avoid oscillator
pulling [30].
56. By Criterion 56
Mismatch between transceiver and PA
Moreover, for typical designs, as the PA output exceeds 0
dBm, injection pulling may prove severe [16].
Nevertheless, take Qualcomm SDR660 for example [19], the
output power from transceiver exceeds 0 dBm.
57. By Criterion 57
Mismatch between transceiver and PA
In other words, not only PA output causes injection pulling,
but also transceiver output does. If the impedance between
transceiver and PA is NOT 50 Ohm, the reflection thanks to
mismatch may cause injection pulling [13].
58. By Criterion 58
Lesson learnt_8: B41 EVM issue due to RX path
Modern MMPAs adopt fully programmable MIPI (Mobile
Industry Processor Interface) control, which can easily
enable more than one RF path simultaneously [8,28]. B41 is
TDD, receiver path should be off while transmitter is
operating. Because improper value is written into PA register,
which makes receiver path enable (marked as red circle)
while transmitter is operating.
59. By Criterion 59
Lesson learnt_8: B41 EVM issue due to RX path
Thus, a fraction of PA output power leaks to transceiver
through receiver path, thereby causing VCO pulling. Unlike
FDD system, TDD system does NOT have duplexer to
suppress TX leakage. Thus, the VCO pulling proves severe
and causes EVM issue.
60. By Criterion 60
PA Nonlinearity
Additionally, the PA nonlinearity, AM-AM and AM-PM
distortion, causes the amplitude error and phase error on
the output signal and then has a contribution to EVM [1,20-
21].
61. By Criterion 61
PA Nonlinearity
As shown above, the AM-AM and AM-PM distortion
increases as the output power is increased [1]. Especially,
as mentioned earlier, OFDM-based transmitter is sensitive to
phase error [20]. Thus, the saturated output power should
be high enough to posses more headroom, thereby causing
more back-off and better linearity [1]. This is especially
important for TDD (Time Division Duplexing) bands such as
B38/B40/B41 since PA is pulsed on and off during usage.
This kind of dynamic mode has worse linearity performance
than static mode (i.e., FDD bands) [26].
62. By Criterion 62
PA Nonlinearity
The modulation scheme and maximum output power per
band configurations for a MMPA is as shown below [1]:
63. By Criterion 63
DPD
Usually, there are three ways to improve PA linearity. First,
do DPD (Digital Pre-Distortion), which is a method
universally adopted and employed in wireless cellular
industry [1,5, 22].
64. By Criterion 64
Load-pull
Secondly, tune PA output impedance to transform the load
impedance (usually 50 Ohm) into the desired one [1].
Reference
Plane PA Output pin
65. By Criterion 65
Load-pull
As shown below,
the blue contour
represents efficiency (%)
and red contour
represents
saturated power [23].
It is apparently that
there is a trade-off between
efficiency and linearity.
Thus, you need to optimize
saturated power
at the expense of efficiency.
66. By Criterion 66
Envelope Tracking
Third, tune the PA voltage supply [1]. ET (Envelope-tracking)
is a technique for improving the energy efficiency of PA. The
traditional DC-DC converter supplying (usually from PMIC
directly) is replaced by a highly agile ET power supply
modulating the power supply of the PA. It means that the PA
is always operating in a highly efficient compressed state
[24].
67. By Criterion 67
Envelope Tracking
As mentioned earlier, there is a trade-off between linearity
and efficiency. Thus, ET improves efficiency at the expense
of linearity. Conversely, you can also optimize linearity at the
expense of efficiency. That’s why you can tune the PA
voltage supply. Practically, you can tune ICQ (Quiescent
Current) point.
68. By Criterion 68
I/Q Signals
Quadrature imperfections in the up-mixing can cause IQ
imbalance, which distorts constellation symbol location and
aggravates EVM performance [13,17,25].
69. By Criterion 69
I/Q Signals
Excessive DC component in I/Q branches cause high level
of carrier leakage (IQ origin offset), which also distorts
constellation symbol location and aggravates EVM
performance [13].
70. By Criterion 70
I/Q Signals
As shown below, “1” is just RF transmitting signal, “2” is
carrier leakage, and “3” is called “image” thanks to IQ
imbalance [6].
71. By Criterion 71
I/Q Signals
Consequently, calibration is necessary for improving IQ
imbalance and carrier leakage [13].
73. By Criterion 73
I/Q Signals
As mentioned earlier, the XO signal from PMIC to transceiver
is rich in harmonics (i.e., 19.2 MHz*N, N is integer). Thus, IQ
traces should be away from XO signal. Otherwise, those
channels, whose frequencies correspond to 19.2 MHz*N,
may have EVM issue.
74. By Criterion 74
I/Q Signals
Therefore, please reserve LC filter on IQ traces, as shown
below [13]:
75. By Criterion 75
I/Q Signals
Nevertheless, the value of bypass capacitors should NOT be
too large. For example, the 150 pF frequency response is as
shown below:
76. By Criterion 76
I/Q Signals
Since the self-resonant frequency of 150 pF is 847 MHz,
which exhibits LPF characteristic in baseband domain. The
IQ frequency range of various bandwidth is as shown below:
Thus, IQ amplitude of the signal with wider bandwidth may
be attenuated, thereby causing power and EVM issues.
77. By Criterion 77
I/Q Signals
Besides, avoid routing IQ lines near or directly under PMIC
SMPS (Switching Mode Power Supply) PCB areas since the
strong switching noise can couple magnetically and
electrically to IQ lines even though in the presence of GND
plane separation.
78. By Criterion 78
I/Q Signals
As shown below, the case where the IQ traces are separated
from PMIC switching node by multiple ground layers, but it
is not recommended [30].
79. By Criterion 79
I/Q Signals
As shown below, the IQ lines don’t overlap PMIC area, this is
recommended.
80. By Criterion 80
Lesson learnt_9: EVM issue due to cable loss
The transmit EVM specification for LTE is as shown below:
The measurement is as shown below:
It’s over the limit obviously.
81. By Criterion 81
Lesson learnt_9: EVM issue due to cable loss
As mentioned earlier, both too high and too low feed-back
power make the output power too high finally thanks to
compensation mechanism. Moreover, cable loss setting is a
critical factor as well.
While doing calibration, RGI 51 is expected to generate 22.5
dBm output power. Nevertheless, in the absence of cable
loss setting, RGI 51 generates merely 21.5 dBm output
power. Therefore, in order to achieve expected 22.5 dBm, the
RGI is increased to 52. But, with RGI 52, the actual output
power is 24 dBm in the presence of cable loss setting.
83. By Criterion 83
Lesson learnt_9: EVM issue due to cable loss
Consequently, although the measured output power is 22.5
dBm on the display, the actual output power is larger than
the measured one, maybe 24 dBm. As mentioned earlier, the
AM-AM and AM-PM distortion increases as the output power
is increased, so does EVM. That’s why EVM failed.
84. By Criterion 84
Lesson learnt_9: EVM issue due to cable loss
Usually, there will be some symptoms during calibration if
cable loss is NOT set well.
85. By Criterion 85
Lesson learnt_9: EVM issue due to cable loss
As shown above, HDET value in mid channel is too high.
During calibration, if the received power by CMW500 is
too low, it will force DUT to increase output power to
achieve target power, thereby causing too large output
power and feedback power.
86. By Criterion 86
Lesson learnt_9: EVM issue due to cable loss
Thus, as shown below, if cable loss setting is lower than
actual cable loss, which makes the output power received
by CMW500 lower than expectation. And then, CMW500 will
force DUT to increase its output power
87. By Criterion 87
Lesson learnt_9: EVM issue due to cable loss
Hence, increase additional 0.7 dB cable loss, and the
calibration passes.
88. By Criterion 88
Lesson learnt_9: EVM issue due to cable loss
In short, during calibration
Too high outputpower and feedback power => cable loss
Too low output power and feedback power => cable loss
So that’s why output power in low/high channels decreases
as the cable loss increases. And, of course, so does mid
channel.(So the calibration passes)
89. By Criterion 89
FBRX
Have a look at the definition of EVM again, which includes
magnitude error.
Thus, lay FRBX trace in inner layers for better protection.
Otherwise, magnitude error leads to poor EVM as well.
91. By Criterion 91
FBRX
Due to LNA poor IP2, the IMD2(5380 MHz – 2690 MHz = 2690
MHz) may increase the noise floor, thereby aggravating HB
signal feedback SNR.
94. By Criterion 94
FBRX
Without LPF rejecting WIFI 5 GHz jammer on FBRX path,
LNA poor IP2 leads to high IMD2 product raising noise floor,
thereby aggravating HB signal EVM performance due to
magnitude error.
95. By Criterion 95
FBRX
As shown below, there is NO DC_I/Q calibration data stored
in Gain State 3.
96. By Criterion 96
FBRX
Again, we have to realize that FBRX is a LNA. So incorrect
gain mode leads to low SNR, thereby aggravating EVM
performance.
Of course, DC block is necessary.
99. By Criterion 99
FBRX
Therefore, daisy chaining these couplers for FBRX path is
forbidden due to insufficient SNR. The SNR should be at
least 30 dB, and which can be achieved by SPnT due to its
port-to-port isolation.
100. By Criterion 100
FBRX
With SP4T, the SNR is acceptably 40 dB(> 30 dB).
SP4T port-to-port isolation
101. By Criterion 101
The influence of filter
Filter contributes to EVM as well. As mentioned earlier, DPD
is a method to improve linearity. Nevertheless, during DPD,
the pre-distorted waveform will be truncated if the filter
bandwidth is not wide enough, thereby contributing to EVM
[5].
102. By Criterion 102
The influence of filter
Besides, the deviations in group delay cause signal
distortion [5].
103. By Criterion 103
The influence of filter
Usually, large group delay variation appears near the
transition region in frequency response, leading to distorted
waveform [5].
104. By Criterion 104
The influence of filter
Thus, with large deviations in group delay, the channels
near the transition region suffer from EVM issue more easily.
The total EVM of an LTE signal is as calculated below [5]:
EVMi is the EVM measured across the individual RB. N is the
total number of RBs in the LTE signal.
105. By Criterion 105
The influence of filter
EVMi can be as calculated below:
∆α is the effective magnitude ripple across the individual RB
of the filter’s passband; ∆ø is the effective phase ripple
across the individual RB of the filter’s passband [5].
Thus, both ∆α or ∆ø across the individual RB of the filter’s
passband have impact on the overall EVM performance.
106. By Criterion 106
The influence of filter
In addition to group delay ripple and bandwidth, temperature
stability is a crucial factor contributing to EVM as well. As
shown below, the frequency response may drift towards the
left side under high temperature.
107. By Criterion 107
The influence of filter
Thus, during calibration, perhaps the growing heat in PCB
makes the frequency response drift towards the left side,
thereby reinforcing the loss in high channel and the output
power is not as expected. At this time, as mentioned earlier,
the RGI is increased to compensate for the loss so as to
achieve expected power. This causes too high output power
in high channel under normal temperature, thereby
aggravating EVM [5].
108. By Criterion 108
Lesson learnt_10: EVM issue due to filter
As shown below, by far the worst result was the 15 MHz
bandwidth case due to insufficient filter’s bandwidth (14.6
MHz), thereby truncating the waveform of some channels.
109. By Criterion 109
Lesson learnt_10: EVM issue due to filter
Furthermore, except 15 MHz, it is apparently that narrower
bandwidth results in worse EVM. It is relevant for proportion.
For instance, with 1.4 MHz signal bandwidth, if three RBs are
contaminated by large group delay ripple near transition
region (e.g. low/high channel), it means that 50% RBs (3/6 =
50%) have poor EVM, thereby aggravating the overall EVM.
Conversely, with 10 MHz signal bandwidth, even though 5
RBs are contaminated by large group delay ripple near
transition region, it means that merely 10% RBs (5/50 = 10%)
have poor EVM, which is not severe enough to the overall
EVM [5].
110. By Criterion 110
Lesson learnt_10: EVM issue due to filter
Thus, what matters most is how much the proportion is, not
how many the contaminated RBs are.
111. By Criterion 111
Timing
As mentioned earlier, TDD bands have worse linearity
performance than FDD bands. Additionally, for TDD PA, once
PA is on, amplitude must be flat during entire transmission.
Otherwise, any rise or droop contributes to AM/AM
distortion and degrades EVM [26]. So TX related timing
(PA_ON, ASM, etc.) is crucial [31].
112. By Criterion 112
Power
Furthermore, thanks to dynamic mode operation, once PA is
on, the power supply generates huge transient current,
thereby aggravating voltage ripple[13].
Any imperfection in power supply (e.g. IR drop, ripple, noise)
causes poor transmitter performance.
Thus, for TDD PA, proper decoupling method is necessary.
114. By Criterion 114
Power
As for transceiver, pay attention to not only keep-out areas,
but also power supply. Use star-routing for power supply
pins rather than daisy-chain [30].
Power
Supply
Noisy pin Contaminated pins Noisy pin Clean pins
Power
Supply
115. By Criterion 115
Power
As shown below, there are five power supply sources from
PMIC to transceiver, four of them (as marked green circle)
provide to multiple pins. It is necessary to make use of star-
routing for these pins.
116. By Criterion 116
Power
Branch at capacitor (as marked black circle in previous
photo) only [30].
117. By Criterion 117
Power
As shown below, the isolation effect depends on the branch
point position, which should be as close to power source as
possible to increase the impedance of the coupling path
between noisy pin and other pins, thereby making other pins
as clean as possible.
Noisy pin Clean pins
Power
Supply
Noisy pin Clean pins
Power
Supply
118. By Criterion 118
Lesson learnt_11 EVM issue due to LCM
EVM fails while LCM is on, but passes while LCM is off. As
shown below, since VPH_PWR branches close to backlight
driver IC, thereby causing the impedance of the coupling
path low. Thus, transient current from backlight driver IC
leaks to MMPA easily. That’s why EVM passes while LCM off
due to the absence of transient current [13].
119. By Criterion 119
Lesson learnt_12 EVM issue due to WIFI
EVM fails while LTE and WIFI operate simultaneously. As
shown below, there is no sufficient isolation between
cellular and WIFI XO traces. As mentioned earlier, XO signal
is rich in harmonics, so they interfere with each other in this
case [35].
120. By Criterion 120
Lesson learnt_13 EVM due to incorrect schematics
As shown below, since TX_DAC1 IQ pin is connected to
GND, DC current leaks from GND to IQ pins that practically
function. Hence, carrier leakage causes EVM issue
121. By Criterion 121
Lesson learnt_13 EVM due to incorrect schematics
Those IQ pins that don’t practically function should be
floating instead of shorting to GND. As shown below:
123. By Criterion 123
Introduction
The IMD (Intermodulation) contributes to ACLR. Therefore,
the linearity of transmitter chain, especially PA, determines
the ACLR performance [6,27].
124. By Criterion 124
Introduction
As mentioned earlier, SC-FDMA is used for LTE uplink
transmission to reduce PAR [1,5]. Nevertheless, LTE still has
higher PAR in uplink modulation than WCDMA. Thus, even
though in the presence of smaller output power (LTE:23
dBm, WCDMA:24 dBm), LTE still has worse ACLR
performance due to higher PAR. In other words, the linearity
requirement of LTE is more stringent than WCDMA.
125. By Criterion 125
Lesson learnt_14: WCDMA ACLR issue due to ICQ
With the identical frequency range, LTE B5 and WCDMA B5
share the same transmitter path. Because the linearity
requirement of LTE is more stringent than WCDMA, there is
no need to tune PA output impedance to transform the load
impedance into the desired one. Finally, the issue was
solved by modifying ICQ.
Thus, if LTE/WCDMA/GSM
share the same
TX path, you just need
to test LTE TX
performance during
matching tuning phase.
126. By Criterion 126
Synchronization for ET
For ET, it is crucial that Vcc and the RF input signal are
aligned in time of the PA. Otherwise, there will be time delay
between RF input signal and Vcc, thereby aggravating
transmitter performance, such as ACLR and EVM [29].
Thus, proper time delay adjustment is necessary.
127. By Criterion 127
Lesson learnt_15: ACLR issue due to decoupling capacitor
With ET technique, wider signal bandwidth aggravates ACLR
performance since PA with ET technique always closes to
saturation point, where nonlinearity becomes notable. And
wider LTE signal bandwidth brings more RBs, which lead to
higher PAPR and higher requirement of linearity.
128. By Criterion 128
Lesson learnt_15: ACLR issue due to decoupling capacitor
As shown below, ET DC-DC converter provides power
supply to PA (i.e., Pin29, VSW), and C5513 (as marked blue
rectangle) should be 470 pF.
129. By Criterion 129
Lesson learnt_15: ACLR issue due to decoupling capacitor
Nevertheless, thanks to incorrect value (470 pF -> 47 nF),
and the signal waveform is as shown below:
130. By Criterion 130
Lesson learnt_15: ACLR issue due to decoupling capacitor
In terms of time domain, high PAPR means high variation in
envelope. Since bandwidth of 20 MHz has higher PAPR than
5 MHz, which means the aforementioned synchronization is
more crucial to 20 MHz than 5 MHz bandwidth.
Hence, too large decoupling capacitor value slows down the
speed of Vcc and reinforces time delay between Vcc and RF
signal, especially in 20 MHz bandwidth, and ACLR fails.
131. By Criterion 131
Lesson learnt_15: ACLR issue due to decoupling capacitor
Definitely, now that the root cause is synchronization. As
long as we use conventional fixed power supply instead of
ET, the issue is gonna be solved as well.
133. By Criterion 133
GSM PA and 3G/4G PA for ET configuration
As shown above, now that path1(red path) supports both
APT/ET, why not make GSM PA using APT and 3G/4G PA
using ET share the same Vcc?
Take Qualcomm QET4100 for example, its load capacitance
should NOT be more than 900 pF.
134. By Criterion 134
GSM PA and 3G/4G PA for ET configuration
In general, the total internal shunt capacitance of Vcc of
3G/4G PA is about 100~300pF.
Thus, even though two or three 3G/4G PAs share the same
Vcc, their total internal shunt capacitance is still less than
ET DC-DC converter load capacitance limit.
135. By Criterion 135
GSM PA and 3G/4G PA for ET configuration
Compared to 3G/4G PA, GSM PA has large total internal
shunt capacitance, even as large as 2 ~ 3 nF.
So making 3G/4G PAs and GSM PA share the same Vcc
makes the total internal shunt capacitance larger than the
limit by a long shot. Doing this brings the aforementioned
synchronization issue definitely.
136. By Criterion 136
Memory Effect
Occasionally, the ACLR is asymmetric, which is related to
memory effects in PA. Memory effects are changes in a PA’s
nonlinearity resulting from the previous history of the input
signal [32]. Self-heating has already been proven to be one
of the key sources to memory effect in PA. In addition, the
memory effect depends on signal bandwidth as well [33].
Therefore, asymmetric ACLR phenomena often occurs in
maximum output power, especially wider bandwidth.
137. By Criterion 137
Memory Effect
The solution to this issue is to tune PA load impedance [34].
138. By Criterion 138
Non 50 Ohm impedance of connector
Tune the impedance from antenna port to duplexer first to
shrink the circle, then tune the impedance from PA to
duplexer to determine the circle location in Smith Chart
139. By Criterion 139
Non 50 Ohm impedance of connector
Nevertheless, in this case, for connector signal pad, to see
L9 as GND proves severe mismatch due to merely 14 Ohm
[13].
140. By Criterion 140
Non 50 Ohm impedance of connector
Therefore, in this case, it is very difficult to pull load
impedance to 50 Ohm for the common path [13]. Thus, for
PA, ASM. and connector etc., metal under their signal pads
should be cut out to retain 50 Ohm, if necessary. In this case,
L9, L8, and L7 should be cut out to retain 50 Ohm (GND is
L6).
141. By Criterion 141
Harmonics of LO
Ideally, the baseband signal is mixed with an up-converter
(LO) to obtain the (LO + BB) component at transceiver
output. Nevertheless, practically, the LO often generates
square-wave signal which is rich in harmonics. Thus, there
will be (LO ± BB) and (3LO ± BB) at mixer output.
142. By Criterion 142
Harmonics of LO
Thus, if not properly filtered before PA, (LO ± BB)
components due to PA nonlinearity appears near RF signal,
thereby aggravating ACLR [31].
143. By Criterion 143
Lesson learnt_16: ACLR issue due to charging
ACLR only fails while charging function enables. For a 5V
DCP (Dedicated Charging Port) plug-in, the charging noise
is set to 600 kHz, which leaks from PMIC through PA DC-DC
converter to PA. Hence, the IMD2 components near RF
signal aggravates ACLR.
144. By Criterion 144
Lesson learnt_16: ACLR issue due to charging
So the filter is necessary on the path between PMIC to ET
DC-DC converter, or the direct path between PMIC and PA.
145. By Criterion 145
Lesson learnt_17: ACLR issue due to shielding can
As shown below, if someone presses the shielding can with
finger, the ACLR performance is good, and vice versa.
146. By Criterion 146
Lesson learnt_17: ACLR issue due to shielding can
As mentioned earlier, the PA couples its strong RF energy
onto the shielding can. An appreciable fraction of the PA
output couples to the PA input by means of reflection,
thereby driving PA to higher output power level (25 dBm)
and aggravating ACLR. To press the shielding can with
finger is able to reinforce the grounding, thereby making all
the fraction of PA output signal flow to main ground directly.
By doing this, no reflection, no issue.
147. By Criterion 147
Lesson learnt_17: ACLR issue due to shielding can
Furthermore, if the reflected TX signal leaks to PA Vcc, as
mentioned earlier, any imperfection in power supply such as
noise, TX performance will become poor.
148. By Criterion 148
PA input matching
Additionally, PA input is the load impedance of DA (Driver
Amplifier) as well. In other words, non-50 Ohm impedance
degrades DA’s linearity and aggravates ACLR at PA input.
Poor ACLR at PA input causes worse ACLR at PA output.