Electronic – Measuring the phase difference between two signals

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I'm looking for an analog method of measuring the phase difference between two signals operating at frequencies in the range from (0 – 20 MHz). I'm wondering if there's an IC that does that or a specific circuit that converts the phase difference into a voltage signal.

Thank you very much

Best Answer

With more specifics on input and output Voltage range, a better answer can be provided.

To measure phase, as Steven says assuming they are equal amplitude and linearity you can subtract but this is a time-variant signal not DC phase output, so one might use a Peak Detector to rectify that signal to mix the result to generate a DC voltage for Phase difference.

The amplitude needs to be normalized (the same) so linear slicers or limiters are used as well as XOR gates ( which is a logic gate that also works here as a mixer/phase detector for logic level signals.

THere are many other ways too such as edge detect, S&H sawtooth clock and Time Interval counters.

.. A better way that I suggest is the 4046 PLL chip.

Do you want 0~180 deg = 0 to Vdd? then use TYPE I "XOR gate" chip or 0~360 deg then use the Type II edge detect phase detector.

CMOS 4046 PLL chip is very easy to use, and has been around since mid 70's, when I first used it.

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Electronic – Detecting phase between square wave and sine wave signals

Phase detection is the easiest for digital signals; it's basically an XOR gate. I would convert the sine to a square wave. Feed a comparator with the sine on one input and the averaged sine (LPF) on the other, so that the comparator gives a 50 % duty cycle square wave. Then use a digital phase detector.

Electronic – How to calculate phase shift between two sine wavefroms

You need to use Olin's idea of determining the zero crossings of the signals to get the time delay. Then plug the time delay into Scott's equation to get the phase delay.

The following is pseudo-code. I'll leave it up to you to implement each function since they should either be trivial to implement or you should already have something similar written.

reset_timer();    //reset timer to zero

while(get_amplitude(INPUT_CHANNEL) > 0.0)
{
    //do nothing until input channel crosses zero
}

start_timer();    //start timer counting

while(get_amplitude(OUTPUT_CHANNEL) > 0.0)
{
    //do nothing until output channel crosses zero
}

stop_timer();    //stop timer counting

time_delay_ticks = get_timer_ticks();    //get the number of timer ticks between zero crossings 
time_delay = ticks_to_time(time_delay_ticks);    //need to get timer ticks into time domain

period = 1 / frequency;    //get the period from the known frequency

phase_delay = (time_delay / period) * 360;    //calculate phase delay

It's important to read the documentation on the timer you will be using so that you know how to convert from timer ticks into time.

Best Answer

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Electronic – Detecting phase between square wave and sine wave signals

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