# Adding Harmonics: Doubling Frequency of Alternating Signals

• chaoseverlasting
In summary, the conversation discusses ways to double the frequency of a given signal. It is suggested to use a frequency doubler with a sinusoidal signal, but for non-sinusoidal signals, other methods such as using an analog multiplier or a phase lock loop can be used. However, these methods may not be real-time. Another option is to use an ADC and store the values in memory, or to use a Fourier Transform. Frequency doublers are usually efficient and there are other schemes involving discreet components. One example is using a bridge rectifier and bandpass filtering the output. Ultimately, it is recommended to pump a nonlinear device with a sinusoidal signal to generate the second harmonic.
chaoseverlasting
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?

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?

## Q1: What is the purpose of adding harmonics by doubling the frequency of alternating signals?

The purpose of adding harmonics by doubling the frequency of alternating signals is to create a richer, more complex sound. By doubling the frequency, we are essentially adding a higher-pitched version of the original signal, which can enhance the overall timbre and texture of the sound.

## Q2: How do you add harmonics by doubling the frequency of alternating signals?

To add harmonics by doubling the frequency of alternating signals, we can use a device called a frequency multiplier. This device takes the original signal and creates a copy of it at double the frequency, which can then be combined with the original signal to add harmonics.

## Q3: What types of signals can benefit from adding harmonics by doubling the frequency?

Any alternating signal can benefit from adding harmonics by doubling the frequency. This includes audio signals, such as music and speech, as well as electronic signals used in communication and data transmission.

## Q4: Are there any potential drawbacks to adding harmonics by doubling the frequency?

One potential drawback of adding harmonics by doubling the frequency is the risk of introducing unwanted noise or distortion. This can happen if the frequency multiplier is not properly calibrated or if the original signal is too weak or noisy.

## Q5: Can adding harmonics by doubling the frequency improve the quality of a signal?

Yes, adding harmonics by doubling the frequency can improve the quality of a signal in some cases. It can make the sound more interesting and dynamic, and can also help to clarify and enhance certain frequencies within the signal. However, it is not always necessary or beneficial to add harmonics, as it depends on the specific characteristics of the original signal and the desired outcome.

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