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Hello everybody
I'm Taeyeop from Seoul, Korea. I'm sorry to be poor at English.
I have been used TRF3702EVM(I/Q modulator) for WCDMA applications. In datasheet of TRF3702, the best performance of ACLR is 71 dBc using single-carrier WCDMA at -14 dBm channel power. The measurement set-up for this is combination of DAC5686(16 bit resolution) and TRF3702.
By the way, I use 14-bit AWG(Aribtrary waveform generator). Differences are below.
Datasheet : 16-bit DAC, differential input of TRF3702, measurement @ 2.14 GHz, Optimization of measurement circuit.
My case : 14-bit DAC, single-ended input of TRF3702, measurement @ 1.85 GHz, Using TRF3702EVM(Evaluaton board) through 0.5m cables(Both I and Q) from AWG.
These are main 4 items of difference between datasheet and my set-up. Any other set-ups are almost same and I replace proper balun for 1.85 GHz applications. I also replace some resistors with proper value. As a result, ACLR measurement value of my case is 57 dBc by Spectrum Analyzer(LG Innotek SA 930).
The problem is that I cannot retain sufficient ACLR value like datasheet, 71 dBc. If there are no any other difference from datasheet, what can I do for better linearity?
Is it possible for degradation of chip performance cause difference of set-up mentioned above?? If possible, then which part is suspicious ?
This is very important part of my research. Any kind of advises will be helpful for me.
I thank you in advance for your concern.
Hello Taeyeop,
ACLR setups can be tough to setup as the issue could be related to the instruments, the device or some setting. It may help this discussion if you can forward a screen shot of your ACLR signal that may help me understand what you are seeing.
TRF3702 conditions:
Do you have a 3.7V common mode input?
Can you confirm your channel output power is at -14dBm for single carrier WCDM signal?
Spectrum Analyzer:
I’m not familiar with the SA-930. I tried to look up the datasheet on line, but did not have any luck finding one. In my experience the spectrum analyzer selection and settings are the biggest piece to the puzzle of making good SA measurement.
- Have you ever measured 71dBc type ACLR numbers on this SA before?
- Recommended spectrum analyzer adjustements
AWG:
Have you ran the AWG input into your SA to see if your system ACLR is better than 71dBc?
Some AWGs maybe not be capable of that level of performance. I’m not sure what model you have?
Hope this helps some
Chris
Hi Chris
Thank you for your reply. I really thank you.
* TRF3702
I use exact 3.7 V for common mode input. In my set-up, output power of TRF3702EVM is about -13 dBm when ACLR is the best. I think 1 dBm difference is acceptable.
* Spectrum Analyzer
SA-930 is product of LG-Innotek. I think the model is used widely in South Korea. It's not familiar model.
I agree with your opnion. I have never seen ACLR measurement using this model. This is my first experience.
I would better measure ACLR using another spectrum analyzer, Agilent.
I'll check every item you mentiond above about SA.
*AWG
The model is M2i.6034 of SPECTRUM. I think it is one of the best performance AWG among PCI interface.
http://spectrum-instrumentation.com/de/products/da-arbitrary-waveform-generators-pci-pci-x-125-mss
I'll check set-up mainly specturm analyzer. It is more possible than other variable.
Thank you very much again Chris.
Have a nice day.