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Sinusoidal Phase Shift

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meastwood98

New Member
Hi,

I am trying to phase shift a sinusoidal signal by a small amount (a degree or two), I am aware I could do this with some ADC and microprocessor. However I would like to do it with some simpler analogue electronics, I have been looking at an "all-pass filter", however my signal will have a varying frequency and therfore this will not work as an "all-pass filter" will only work for a certain frequency. Any ideas?

Any help would be much appriciated?

Thanks,
Mark
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi,

I am trying to phase shift a sinusoidal signal by a small amount (a degree or two), I am aware I could do this with some ADC and microprocessor. However I would like to do it with some simpler analogue electronics, I have been looking at an "all-pass filter", however my signal will have a varying frequency and therfore this will not work as an "all-pass filter" will only work for a certain frequency. Any ideas?

Any help would be much appriciated?

Thanks,
Mark
hi Mark,:)
What are the frequency limits, min/max and how 'accurate'.??
 

meastwood98

New Member
Minimum frequency = 1Hz
Maximum frequency = 100Hz

I would estimate an accuracy of half a degree would be sufficient however i could probably work with a value worse than this.

If you need any more info, let me know.

Thanks,
Mark
 

ericgibbs

Well-Known Member
Most Helpful Member
hi,
This very simple circuit accepts a 0.5Vpk sinewave signal and shifts it a few degrees.

Over the range of 100Hz thru 1KHz the phase shift does vary a little.

Do you use the LTspice simulator.?
 

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ericgibbs

Well-Known Member
Most Helpful Member
No, i use NI multisim to simulate circuits. Would it be possible to modify the circuit to run it from a 5v supply?
It should be OK at +5V, the output swing will be reduced.

Give it a try,,, the value of the 820R changes the amount of shift, try a few different values.

Lets know how it goes.:)
 

meastwood98

New Member
Sorry, I fogot to mention my signal is a sinusoid that has an offset, its magnitude is 1.2v pk-pk and is offset 2.5v. That circuit works fine for a signal with no offset, can it be modified to work with my signal?

Thanks,
Mark
 

ericgibbs

Well-Known Member
Most Helpful Member
Sorry, I fogot to mention my signal is a sinusoid that has an offset, its magnitude is 1.2v pk-pk and is offset 2.5v. That circuit works fine for a signal with no offset, can it be modified to work with my signal?

Thanks,
Mark
hi Mark,
Is that a 'dc' offset of 2.5V.? , ie: its a 1.2Vppk superimposed on +2.5Vdc level.?

Can you post your Sim circuit.?
 

meastwood98

New Member
Yes so the peak value is 3.1v and the trough is 1.9v, I dont have a sim circuit, I just built up your circuit to test it.
 

ericgibbs

Well-Known Member
Most Helpful Member
hi Mark,
Just sims OK.
The images are for 1KHz, 500Hz and 100Hz[ with the cct].

The 2nd stage is bring the output to the same level as the input, if required.

Note the fairly high output impedance.:)
 

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meastwood98

New Member
From my simulation of the circuit the phase shift is dependant on frequency, are you sure you didnt adjust the value of R when testing it at different frequencies?
 

ericgibbs

Well-Known Member
Most Helpful Member
From my simulation of the circuit the phase shift is dependant on frequency, are you sure you didnt adjust the value of R when testing it at different frequencies?
No I didnt.:)
 

ericgibbs

Well-Known Member
Most Helpful Member
Ok. Any ideas to where im going wrong?
hi,
I have just re-run the sim, this time using a sweep freq, same results as the ones I posted.

Please post the simulation details and circuit that you are using, also with some details of the changes being observed.
 

meastwood98

New Member
My apologies, the circuit does work at 100Hz, 500Hz and 1kHz. However when i reduce the frequency to 10Hz, the phase shift increases. Is this the same with your simulation?

Thanks
 

ericgibbs

Well-Known Member
Most Helpful Member
My apologies, the circuit does work at 100Hz, 500Hz and 1kHz. However when i reduce the frequency to 10Hz, the phase shift increases. Is this the same with your simulation?

Thanks
hi
This was your reply to my post asking for limits.
Minimum frequency = 1Hz
Maximum frequency = 100Hz
I have not tested at 10Hz, your spec was 100Hz thru 1000Hz.:)

EDIT:
I see what I have done wrong, I have misread 1HZ as 1KHZ!!!, what a plonker, very sorry about that.

I will beat my self with a pain stick for 10 minutes.
 
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ericgibbs

Well-Known Member
Most Helpful Member
hi,
See my edit.

I will rework the circuit to suit 1HZ and 100Hz limits, get back to you.:)
 
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ericgibbs

Well-Known Member
Most Helpful Member
hi,
At these low frequencies the size of the capacitors makes this technique not a feasible method.

From about 10Hz thru 100Hz the coupling caps are 1000uF and the phase shift is only just acceptable, less than 10Hz the phase shift is not acceptable.

I'll think of an alternative solution, let you know the outcome.

EDIT:
Can you say what is the application is for this phase shifted signal, ie: whats the end result.?
 
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meastwood98

New Member
We have a linear sensor that gives out two sinusoidal signals 90 degrees apart, these are put through an interpolator (which we cannot play with the electronics inside) and then into a PC for Transmission Error Measurement. The problem we are facing is a large error on the PC, which is caused by the two signals not being exactly 90 degrees apart. There is approximately 2-3 degrees of error.
 
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