John Miles wrote: > Hmm, I didn't know that. Wouldn't that effect have suppressed the 2nd lobe > almost entirely on the baseband measurement, though, rather than making it > appear 6 dB too high? I should probably repeat that measurement to make > sure of what I'm doing. > > Much appreciate the advice, by the way! > > -- john, KE5FX > > John
In a linear system the corresponding USB and LSB sideband component amplitudes are identical so that on translation to baseband by the phase detector all the even harmonics cancel and the odd harmonics add. However in a non linear system the USB and LSB components will not have equal amplitudes. Assymmetric filter passband response will also attenuate one sideband with respect to the other. If the phase detector LO phase shift isnt exactly 90 degrees wrt to the carrier the even harmonics no longer cancel exactly. In an I + Q demodulator FM USB and LSB components have the following characteristics: I channel: for odd harmonics (of the modulation frequency) USB and LSB components add for even harmonics (of the modulation frequency) USB and LSB components cancel. Q channel: for odd harmonics (of the modulation frequency) USB and LSB components cancel for even harmonics (of the modulation frequency) USB and LSB components add. Bruce _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
