Quadrature modulators are a special case of phase-shift keying, and occur in many applications, including any application where it is necessary to transmit two or more sets of information using only one carrier frequency. Simulation results are presented for the time domain, with extensive Fourier analyses to show the frequency domain views of the simulations. Any configuration parameters necessary to tune the output of the FFT to produce optimum results are discussed.
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Article Modelling Quadrature and PSK Modulators in SPICE
Dear Mark,
welcome,
I went through your paper and found that you used to carrier sources for the I and the Q components. Normally one uses one source say the sine and derive from it the cosine by +90 degrees phase shift. This is the socalled quadrature oscillator.
This is to grantee the synchronization of the two sources.
One other important point that one can use four quadrant multiplies to implement the modulation process where one converts the I data in TTL logic into bipoloar nonreturn zero format and multiply it by the carrier. One gets the PSK waveform.
When you get the I and the Q-modulated waveform you have to add them together and then a dd a band limiting filter.
These are my major comments on your paper.
Best wishes
Thanks, Abdelhalim, for your kind comments.
(The only reason I used two sources was for computational efficiency, since SPICE can evaluate a source faster than it can a resistor+capacitor).
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