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TRF370417EVM: TRF370417EVM

Part Number: TRF370417EVM

Hello,

I'm trying to see the output of the TRF370417EVM evaluation module with only LO at the input as a first test. 

The module is biased with 5 V and I and Q ports are biased with 1.7 V and terminated with 50 Ohm. 

The LO frequency is 500 MHz..

What I see at the output is a lot of unwanted tones where tones at 2. 4 .6 GHz are dominating. 

Any idea what I'm doing wrong?

Kind regards,

Dragan

  • Dragon:

    You are likely seeing the harmonics generated by the modulator and your LO source generator. If all the BB input ports are biased to 1.7V and terminated then you should see your LO bleed-through at 500 MHz at about -40 dBm.  You will also see 2nd and 3rd and higher harmonics at similar levels...maybe a bit higher in some cases.  A high 13th harmonic at 6 GHz is unusual which leads me to think that the LO source is generating this.  Look at the harmonic content from your source to see if this is the case or filter the LO before injecting into the modulator.

    --RJH

  • In reply to RJ Hopper:

    Hello,

    You are right, most of these harmonics are very low (approximately -40 dBm). But there is always one ore more harmonics at about -10 dBm and the highest one is always at 4 times LO frequency. I tried to reduce the LO power and 4xLO harmonic does not respond much . I also tried to filter the LO but didn't get any improvement. I tested it at 500 MHz, 1 GHz and 1.5 GHz.

    Kind regards,
    Dragan
  • In reply to Dragan Gecan:

    Dragan:

    You are seeing the normal operation from the device. The LO path, as part of the quadrature generation, uses limiters to fix the amplitude in each path which in turn generate harmonics. I did a quick test and see that indeed the 4th order harmonics are the worst (as are the 8th harmonics). In my testing, the LO bleed-through was around -40 dBm. 2nd and 3rd harmonics were 5-10 dB lower, and the 4th harmonic was at -25 dBm. At a 500 MHz input, the 8th harmonic was also at about -25 dBm. As the LO increases and the 4th harmonic (and higher) exceed the output BW capability of the device, those spurs diminish.

    In your application, I recommend to add a high frequency lower pass filter to eliminate the higher harmonic components that impact your system.