# Frequency multiplier @ class C

• skoomafiend
In summary, a tank circuit at the output of a class C can be tuned to different harmonics of the input signal by adjusting the capacitance in the tank. This allows the circuit to generate harmonics at a desired frequency. However, trying to generate harmonics by driving the circuit with a lower frequency does not work as tuned circuits behave more like filters.
skoomafiend
This my basic understanding of it. I would appreciate if someone can correct me if I am wrong.

When a tank circuit at the output of a class C is tuned to the input signal, it energizes the tank signal on every cycle of the tank voltage. When you set it to a 2nd harmonic for example it energizes the tank signal on every other cycle.

OK, so in order to set it to a higher harmonic, you have to tune the tank. Which means you have to reduce the capacitance in the tank, so the resonant frequency increases to the next harmonic. So that would mean the capacitor would hold a smaller charge (reduced capacitance in the tank) and discharge faster? Pretty much fast enough to discharge and recharge twice (two cycles) before being re energized by the next input signal pulse?

Thanks!

When the signal passes through the frequency multiplier, it is deliberately distorted to generate harmonics.

Hopefully, one of these will have the frequency you want as output.

You then tune the output to this frequency and the other harmonics are largely rejected and the output is some multiple of the input frequency.

Driving a tuned circuit with a lower frequency to try to generate harmonics doesn't work. Tuned circuits behave more like filters than you may expect and less like, say, a pendulum or a tuning fork.

## 1. What is a frequency multiplier at class C?

A frequency multiplier at class C is a circuit that takes an input signal and produces an output signal with a higher frequency. It operates in class C mode, which means that it uses a nonlinear device, such as a transistor, to amplify the input signal.

## 2. How does a frequency multiplier at class C work?

A frequency multiplier at class C works by using a nonlinear device, typically a transistor, to amplify the input signal. This amplification process creates harmonic frequencies of the input signal, which are then filtered and combined to produce the output signal with a higher frequency.

## 3. What are the advantages of using a frequency multiplier at class C?

There are several advantages to using a frequency multiplier at class C. It is a simple and cost-effective way to generate high-frequency signals, it has high efficiency, and it can produce output signals with very low distortion.

## 4. What are some common applications of frequency multipliers at class C?

Frequency multipliers at class C are commonly used in radio frequency (RF) and microwave applications, such as in communication systems, radar systems, and satellite communication. They can also be used in scientific research, medical equipment, and test and measurement instruments.

## 5. Are there any limitations to using a frequency multiplier at class C?

While frequency multipliers at class C can be useful in many applications, they do have some limitations. They are typically only suitable for low-power applications, and they may introduce some level of phase noise and spurious signals into the output signal. In addition, they may require careful tuning and matching of components to achieve the desired output frequency.

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