How to Detect peak value and phase information

[jitun2]

I have two question.

1.How can we design a circuit(analog circuit) that will give the peak value of a sine wave.that is it will take a sine wave of unknown amplitude(but i know the frequency) and output the peak value of the sine wave as voltage(preferably) or current

2.I have a reference sine wave of known frequency(actually i have all the knowledge about it even including from where it came from).Now i have a unknown sine wave.This unknown sine wave has the frequency same as that of the reference sine wave.But it is either "in phase" or "out of phase" with that known reference sine wave.How to find out which one(i.e. whether it is "in phase" or "out of phase")

 

[audioguru]

I have two questions:

1.How can we design a circuit(analog circuit) that will give the peak value of a sine wave?

Simply make a standard half-wave or a full-wave precision peak detector circuit.

2.I have a reference sine wave of known frequency. Now i have a unknown sine wave.This unknown sine wave has the frequency same as that of the reference sine wave.But it is either "in phase" or "out of phase" with that known reference sine wave.How to find out which one(i.e. whether it is "in phase" or "out of phase")

Simply use a standard phase detector from a phase-locked-loop IC.
You could also make their levels the same then add them. If the output is double then they are in-phase. If the output is zero or very low then they are out-of-phase.

 

[jitun2]

This is what u r trying to say about the second question's answer.

 

[audioguru]

This is what u r trying to say about the second question's answer.

No. An old LM567 has a low output if the signal is within its frequency bandpass, with any phase.
You need a phase-detector like one of the ones in a CD4046 PLL IC.

Or you could make their levels the same with an AGC circuit then add them in an opamp summing circuit. The output will be double if they are in-phase and will be very low if they are out-of-phase.

 

[jitun2]

Thanks audioguru.Can u please make the circuit diagram using CD4046.I mean the phase detector part.Please

 

[audioguru]

Can u please make the circuit diagram using CD4046.I mean the phase detector part.

The CD4046 has two phase detectors. The 74HC4046 has three.
Use the Phase Detector I from the CD4046 as shown in its datasheet. Its output is low when the signals are in-phase, high when they are out-of-phase and in between if the phase is in between.

 

[Roff]

The CD4046 has two phase detectors. The 74HC4046 has three.
Use the Phase Detector I from the CD4046 as shown in its datasheet. Its output is low when the signals are in-phase, high when they are out-of-phase and in between if the phase is in between.

The phase detector outputs are digital signals that switch between the supply rails. The average voltage is proportional to the phase difference between 0 and 180 degrees on the type I detector. You need a lowpass filter on the output of the phase detector.
Jitun2, what is the frequency and amplitude of your sine wave?

 

[audioguru]

You need a lowpass filter on the output of the phase detector.

Normally yes. But in this case of in phase or out-of-phase maybe the filter isn't needed.
I don't like the stuttering and jittering Phase-Comparator II (sample-and-hold) and didn't want to discuss it.

 

[Roff]

Normally yes. But in this case of in phase or out-of-phase maybe the filter isn't needed.
I don't like the stuttering and jittering Phase-Comparator II (sample-and-hold) and didn't want to discuss it.

Yeah, I was just trying to clarify the "in-between" case. Our OP would probably see little spikes at worst.
I agree with your assessment of the type two detector. It is great in a closed-loop application with a high SNR input, such as a digital clock frequency multiplier, where there are no missing or extra transitions. For an open loop application such as this one, I would avoid it.

 

[jitun2]

Frequency= 2.3KHz
Amplitude=13.84V (As seen on an Oscilloscope)

 

[Roff]

Frequency= 2.3KHz
Amplitude=13.84V (As seen on an Oscilloscope)

Both signals have the same amplitude?
What voltage levels do you need from your detector?

 

[jitun2]

The reference signal has that amplitude 13.84V but the signal to be compared with it have the same frequency but of different amplitude.

See the attached images.The wave in green is the reference wave and the one in yellow is the sine wave under question.Now my question is i need a way to know the amplitude of that sine wave(yellow one) and whether it is in phase or out of phase with the reference sine wave(green one)

 

[Roff]

What is the range of amplitudes of the SWUQ (sine wave under question)?

 

[jitun2]

It can maximum go up to the amplitude equal to that of the reference sine wave.it will never be greater than that.i.e. from 0(well cant be zero) to 13.8

 

[Roff]

You will lose the ability to determine phase and amplitude as the amplitude approaches zero. How low do you need to go?

 

[jitun2]

well i know that it will be very very difficult to measure the phase and amplitude as the amplitude of the wave approaches towards zero.actually the range of the sine wave under question has a lower limit of around 2 volts.(actually 1.96v)

So the practical range is 2v to 13.7v

 

[Roff]

I could design a synchronous peak detector that would output the peak as a positive voltage if the signal is in phase, or as a negative voltage if it were out of phase. Would that be better than separate amplitude and phase info, or worse?

 

[Hero999]

It always seems to be me that asks this question but why?

Is this college work? If so do it yourself.

Does this have a specific application? Or is it just for fun?

 

[Roff]

It always seems to be me that asks this question but why?

Is this college work? If so do it yourself.

Does this have a specific application? Or is it just for fun?

Why didn't I think of that? I usually do. Of course, he/she could always lie.