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# HMC984 As Stand Alone Phase Detector?

• The goal: Measure the phase difference between two sine waves from 50kHz up to 70MHz for an impedance measurement device
• The sine waves will have consistent amplitude and will be the same frequency. The amplitude of one of the two sine waves will be attenuated by at most 6dB in reference to the other sine wave. I can choose the magnitude of the sine waves.
• I need to be able to tell the difference between positive and negative phase
• I need to be able to accurately measure phase difference through the entire range of -180° to +180°

Could you please help me decide if the HMC984 could be used as a phase detector? If not, are there any other suggestions? I cannot use the AD8302 because of the inability to measure phase near 180 degrees and also near zero degrees. I also do not think I can use the AD9901 because of the limited range of 270° at 70MHz.

Thank you,

Ryan

• Do you require having the phase detector output be analog?  If not, have you seen the solution that uses an IQ Demodulator + ADC?  There was an Analog Dialogue article written a few years back that shows how to implement this:

• The phase detector can be analog or digital. I will be using a XILINX ZYNQ 7000 series system on a chip as a part of this system, which has the capability to do both. I saw that article, but the only problem is that the ADL5380 frequency range is from 400MHz-6GHz, which is above the frequency range I would like to measure.

Plus, I am already planning on using two AD8361s for the impedance magnitude measurement, but I need a solution for phase.

• The HMC984 would work but there are a couple of considerations.  The datasheet specifies PFD operation down to dc but doesn't mention this assumes square wave inputs.   You would need a comparator circuit to perform the sine wave conversion.  It gets a bit tricky because the HMC984 VCOp/n input was designed to mate with our companion HMC983 divider output:

• Vcm_max = 3.6V
• single ended input [625, 875] mVpp

The PFD charge pump output must be converted to a voltage for the Zynq A/D converter.

• Thank you very much. I will order an HMC984 and a LTC6752-4 comparator to evaluate this solution.

• This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

Thank you,