Requirements for QPSK Transmission

Discussion in 'Wireless & RF Design' started by geschema, Oct 18, 2009.

  1. geschema

    Thread Starter New Member

    Oct 18, 2009
    I need to check if the transmitter module of an existing FM system could be used to transmit a multi-channel (D)QPSK signal. Since I'm no expert on this subject, I'd love to hear additional opinions about this. The transmitter module consists of an AGC circuit (which adjusts the input signal's amplitude to a target value) followed by a power amplifier.

    So far, I have measured the magnitude and phase responses over the band of interest. The magnitude response is almost flat, the phase response is linear. I think this is OK, although I'm not sure about the exact requirements on the phase response.

    The peak-to-average ratio of QPSK seems to be an issue. I've found 5 dB of PAR for QPSK in the litterature, so I guess that the AGC circuit's target value should be reduced by 5 dB, right? But what if I have 8 channels? Do the PARs add-up, so that I have to account for 8 x 5dB = 40 dB of PAR?

    Any other issues I need to consider?

    Many thanks in advance,