Discrete frequency to voltage converter?

BradtheRad · May 21, 2015

neazoi said:
Can you help me design a more sharp (the sharpest the better) tuneable RC HPF fot HF?

Cheers

Another thing to try, is to take advantage of the steep curve of a high Q resonant filter. You can tap to the right or the left of the center frequency.

You would need to adjust the LC frequency so it is a few MHz distant from whatever is your desired frequency.

Another concept. You can make the curve steeper by amplifying the output. For instance, via a transistor amplifier.

Another concept. Put a diode inline, and you subtract 0.6V. Then by amplifying this, you obtain a steeper curve.

neazoi · May 21, 2015

BradtheRad said:
Another concept. You can make the curve steeper by amplifying the output. For instance, via a transistor amplifier.

Another concept. Put a diode inline, and you subtract 0.6V. Then by amplifying this, you obtain a steeper curve.

I would be interested in more information or examples on these please

biff44 · May 22, 2015

a good frequency to voltage converter is to make a PLL, and lock the VCO to your incoming signal. If you measure the VCO tune voltage when the PLL is locked, it is proportional to the incoming frequency.

if it is narrowband tuning range, you can just do a delay line frequency discriminator, or an Armstrong discriminator

BradtheRad · May 23, 2015

neazoi said:
I would be interested in more information or examples on these please

You can run the output into an amplifier, as below. It does not need to be a high-frequency device.

To create a steeper curve, my simulation has an op amp, with a reference voltage at one input. A pot provides variable gain.

If you want simple discrete components then a transistor ought to be able to do a similar job.

Stable voltage regulation is needed in order to make this method work.

You can obtain several volts range from this. Naturally, resolution is less precise when you want to represent a wide frequency range.

neazoi · May 23, 2015

BradtheRad said:
You can run the output into an amplifier, as below. It does not need to be a high-frequency device.

To create a steeper curve, my simulation has an op amp, with a reference voltage at one input. A pot provides variable gain.

If you want simple discrete components then a transistor ought to be able to do a similar job.

Stable voltage regulation is needed in order to make this method work.

You can obtain several volts range from this. Naturally, resolution is less precise when you want to represent a wide frequency range.

Have you attached a schematic? I cannot see it.

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biff44 said:
if it is narrowband tuning range, you can just do a delay line frequency discriminator, or an Armstrong discriminator

Can you display examples of these circuits? I would be interested to know as well.

Discrete frequency to voltage converter?

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Discrete frequency to voltage converter?

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