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TRF370315 error vector magnitude with 2.45GHz fLO

Other Parts Discussed in Thread: TRF370315, DAC3283

Hi all,
My customer evaluated the TRF370315 error vector magnitude with 2.45GHz fLO,
and they think the error is big.

Could you advice about the test result?

Conditions;
=========
   1. fLO=(2.45GHz),+2dBm using a signal generator

   2. I and Q voltage; 
        0.2V differential (DC), Vcom = 1.5V

     (1) In:1.4 V , Ip:1.6V  Qn:1.4 V, Qp:1.6 V
     (2) In:1.4 V , Ip:1.6V  Qn:1.6 V, Qp:1.4 V  
     (3) In:1.6 V , Ip:1.4V  Qn:1.6 V, Qp:1.4 V
     (4) In:1.6 V , Ip:1.4V  Qn:1.4 V, Qp:1.6 V

Results;
=======
     (1) +4.30 dBm
     (2) +4.92 dBm
     (3) +4.31 dBm
     (4) +4.83 dBm
   
      Note:  Using spectrum analyzer for this measurement and 
                  there are some spurious signals at 3.262GHz (-26dBm) and 1.639GHz (-32dBm) in any cases.      

    
Regards,
Toshi

  • Toshi:

    I assume that you are operating at Zero-IF. The common mode voltages deltas are way off. The I/Qp/n DC voltages should all be just about identical. This error will result in poor carrier feed-through which will degrade EVM%. The amplitudes of I/Qp/n are also not matching well. The amplitudes of all of these signals should be just about the same. The phase needs to be balanced as well (harder to measure). The amplitude and phase imbalance on the I/Q path results in poor sideband suppression which will severely degrade EVM%.

    Off the cuff I would say that the I/Q source is not performing very well. An alternative is to utilize one of TI's DAC platforms to generate a good quality baseband output. Something like the DAC3283 may be a good platform.

    ---RJH