Best way to generate 4th power for signal ?

Someone else will step in and do all this with A/D and D/A converters and a tiny microcontroller :-).

If the input is only ever positive in the scale you choose it can be done a little simpler. A logarithm circuit followed by a scale-by-4 circuit followed by an antilog will be much easier. Scale by 4 can be just the feedback network around the individual log or antilog. See

Tim.

You need to provide the type of signal you are dealing with?

Digital pulse ?

Analog Sine wave?

what frequency you are working with ?

etc.

There are answers, how ever, with out more details, I don't think you'll like the pile of them coming at you.

For example, If I was to deal with something in the R.F. range, I could create a band pass amp designed for the 4th tone and force a harmonic of that signal to be created and amplified..

But you don't supply the freq and it's range nor, the type of signal.

You also have PLL (Phase Lock Loop) options.. etc.

Jamie

Fourth power anything would tend to have dynamic range limitations.

I'm guessing by 4th power he means 4th harmonic? Here's a circuit for odd harmonics. Can someone give me a simple explanation why you can't get even harmonics from it.

Ahh.. Fourier of squarewave only has odd harmonics. Hmm any way you can create sawtooth to do this. Mikek

It seems to be a square wave generator ( a diode clipper) feeding a filter. Square waves are composed of odd harmonics.

"In contrast to the sawtooth wave, which contains all integer harmonics, the square wave contains only odd integer harmonics."

-- Les Cargill

Ok, since we're on this subject..

use two of those as a passive circuit with enough signal level, and you have your x4 signal.. no harmonics to deal with.. Well, not directly any how :)

Jamie

Well, Tim S. mentioned digital and log-antilog. There are analog multipliers, it'd be nice if you gave some frequency range. above or below 10MHz. say? Do you need amplifiers after your first pair of mixers? (I've never used mixers as squarers, only as frequency 'shifters'.)

Can you tell us why you want to measure the fourth power of something?

George H.

Don't you mean two mixers in series? Gilbert cell mixers are good multipliers for a limited dynamic range (5 mV to 100 mV). Logarithm converters are better for dynamic range, IF your signal doesn't get near zero (the logarithm converter has a deficiency when it renders negative infinity, the logarithm of zero).

Costas loop.

Yes, or full-wave rectify, filter at 2 fc, rectify again, and finally filter at 4 fc.

But a Costas loop works better.

Jeroen Belleman

What input voltage do jou have? If it is max 5 volt, the output will be 625 volts. If the input is 0.5 volt, the output voltage willbe 0.0625 volt.

Probably homework.

Cheers! Rich

Not relevant. This guy wants to understand how to demodulate a QPSK signal.

Jeroen Belleman