Honored Contributoris possible whit fpga FFT or similar metod measure a phase difference from 2 PULSED-sinusoidals signals?
the freq of signals is 60MHz but the duration of signals is 0.5uSEC, and the PRF of pulsed signals is 1800Hz. tnx Luca
Honored Contributor1) time domain option is unlikely to have good resolution since 60MHz running at sampling freq of say 240MHz means only 4 samples per cycle.
2) fft option may be better. You can model that in matlab: generate stimulus then apply fft and see phase.Honored ContributorIs there any reason why these two signals are pulsed sinusoids?
If this is a ranging application, then an FM chirp (linear FM pulse) would be more appropriate. Pulse compression of the FM chirp (correlation) then results in delta-function like responses (with a width determined by the pulse bandwidth). The 'time delay' between the delta functions can then be determined. Pseudo-random sequences can also be transmitted and pulse compressed in this manner. What are you trying to do? Cheers, DaveHonored Contributortnx to all!
i must analize 3 (or 4) PULSED-RADAR-signals. The minimum duration of signals is 0,5 uSEC (typ 1 uSEC). i need to measure the amplitude and and the phase of these signals, referenced at 1 CW (continuos sinusoidal wave) generated by 1 reference-local-oscillator (60 MHz). In analogic circuit i have not problem, using AD8302(analog devices chip), but i need do it in digital world whit fpga.. tnx!!Honored ContributorIf you have matlab, you can try this code (not tested):
%assuming Fs = 240Msps %signal 1 offset = 100; x1 = sin(2*pi*(0+offset:200000+offset)*60/240); x1(1000:1000:end) = 0; %switch off %ref xref = sin(2*pi*(0:200000)*60/240); y1 = fft(x1,1024); y2 = fft(xref,1024); A1 = abs(y1); A2 = abs(y2); ph1 = angle(y1); ph2 = angle(y2); you will then check A/ph at relevant binHonored ContributorIn my opinion, FFT is a rather longwinded method to analyze the phase of a known frequency sine signal. Quadrature demodulation would allow an accurate amplitude and phase measurement.
Honored ContributorThat is a good point. You mean demodulate signal to its two I/Q components and demodulate reference similarly then check phase/amplitude.
It eventually depends on application resolution and noise level. Demodulation may need filtering the sideband.Honored Contributorbut do i need a IQ anoligic demodulator?
Honored Contributoryou can do digital one if you afford the speed
Honored ContributorI/Q demodulation is done my multiplying the input signal with 0° and 90° reference sine. If you manage to sample the input at fs = 240 MHz, the operation simplifies to processing the odd and even samples. Gating according to the signal enevlope would be necessary in any case.
Honored Contributorat 240MSPS and 60MHz I/Q reference signal, can i measure phase veriation of 1 degree and amplitude variation of 1 db?
