Adding Harmonics: Doubling Frequency of Alternating Signals

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Discussion Overview

The discussion revolves around methods for doubling the frequency of alternating signals, including both sinusoidal and non-sinusoidal waveforms. Participants explore various techniques and components that can be employed in this process, addressing both theoretical and practical aspects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about starting points for doubling the frequency of an alternating signal.
  • Another suggests using a frequency doubler, mentioning a non-linear component like a biased diode, but notes that this process can be inefficient.
  • A participant argues that frequency doublers are most effective with sinusoidal signals and proposes using an analog multiplier or a phase lock loop as alternative methods for sinusoidal signals.
  • For non-sinusoidal signals, additional methods are proposed, including using an ADC to store values and read them out at double the rate, or performing a Fourier Transform followed by frequency multiplication and an inverse transform.
  • Another participant mentions that frequency doublers can be efficient and suggests using a class C amplifier or a bridge rectifier with a bandpass filter as other schemes for frequency doubling.
  • One participant proposes generating the second harmonic by pumping a nonlinear device with a sinusoidal signal and asks for clarification on the specific frequency to be doubled.

Areas of Agreement / Disagreement

Participants express differing views on the efficiency and applicability of frequency doublers, particularly regarding their effectiveness with sinusoidal versus non-sinusoidal signals. The discussion remains unresolved with multiple competing methods and opinions presented.

Contextual Notes

Limitations include assumptions about the types of signals being discussed and the efficiency of various methods, which may depend on specific conditions or definitions not fully explored in the conversation.

Who May Find This Useful

Individuals interested in signal processing, electronics, and those looking to understand methods for manipulating alternating signals may find this discussion relevant.

chaoseverlasting
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This is something I wanted to do, but I don't know where to start. Given an alternating signal (not necessarily sinusoidal) if you wanted to double the frequency of the signal, where would you start?
 
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A frequency doubler?
All you need is a non-linear component of some sort, e.g. a biased diode.
However, this is usually a pretty inefficent process.
 
A frequency doubler works best with a sinusoidal signal. I wouldn't want to try it with a non-sinusoidal signal.

There are a couple of other ways to do it with a sinusoidal signal.
You could use an analog multiplier and multiply the sine wave by itself to square it.
You could use a phase lock loop with a divide by 2 prescaler.

For non-sinusoidal signals I can think of 2 more but neither is real time.
Use an ADC and store the values in memory. Read the memory out at double the ADC rate.
Convert to digital with an ADC and do a Fourier Transform. Then multiply the frequencies by two and do an inverse transform back to time domain.
 
Usually frequency doublers are reasonably efficient. Just run a class C amplifier at half of the design frequency. There are other schemes to double frequencies with discreet components. One that comes to mind is to use a bridge rectifier and then bandpass filter the output.
 
Just pump a nonlinear device with a sinusoidal signal to generate the second harmonic.

What frequency do you want do double?
 

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