# Frequency Multiplier Working

March 19, 2021

A frequency multiplier is an electronic circuit that produces an output signal with a frequency that is a harmonic (multiple) of the input frequency. Frequency multipliers are made up of a nonlinear circuit that distorts the input signal and produces harmonics as a result. Following that, a band pass filter selects the desired harmonic frequency while filtering out the unwanted fundamental and other harmonics. In frequency synthesizer  and communications circuits, frequency multipliers are often used. It could be more cost-effective to create a lower-frequency signal with lower-power and lower-cost equipment, and then use a frequency multiplier chain to produce a microwave or millimeter-wave output frequency. Some modulation schemes, such as frequency modulation, are unaffected by nonlinear distortion (but schemes such as amplitude modulation do not).

Nonlinear optics also uses frequency multiplication. Harmonics of laser light can be produced using nonlinear distortion in crystals. A frequency multiplier can be constructed using a nonlinear electronic component that produces a series of harmonics, followed by a band pass filter that transfers one harmonic to the output while blocking the others.

The nonlinear circuit should maximize the coefficient for the desired harmonic and minimise the others in terms of conversion efficiency. As a result, the transcribing feature is often chosen with care. To generate even harmonics, use an even function, and to generate odd harmonics, use an odd function. See Harmonics Even and Odd Functions for more details. For example, a full wave rectifier can be used to make a doubled. To make a times-3 multiplier, feed the original signal into an overdriven amplifier that produces a nearly square wave. This signal has a lot of 3rd order harmonics and can be filtered to get the x3 result you like.

YIG multipliers frequently use a state full distortion circuit to transform the input sine wave into an estimated impulse train in order to pick an arbitrary harmonic. An infinite number of (weak) harmonics are produced by the ideal (but impractical) impulse train. In reality, a monostable circuit’s impulse train would have a lot of available harmonics. For example, YIG multipliers with phase recovery diodes may take an input frequency of 1 to 2 GHz and produce output frequencies of up to 18 GHz. 1st The width of the impulses can be adjusted by the frequency multiplier circuit to increase conversion efficiency for a given harmonic.

Varactor  with a resistive load. Varactors  that regenerate themselves. Penfield is a town in the state of Pennsylvania.

Frequency multipliers and frequency mixers have a lot in common, and they all use the same nonlinear devices: Class C transistors and diodes. Many of the amplifying devices (vacuum tubes or transistors) in transmitting circuits work nonlinearly and produce harmonics, so an amplification stage can be converted to a multiplier by tuning the tuned circuit at the output to a multiple of the input frequency. Since the power (gain) provided by a nonlinear device drops rapidly at higher harmonics, most frequency multipliers simply double or triple the frequency, with higher factor multiplication achieved by cascading doubler and tripler levels. Circuits tuned to a harmonic of the input frequency are used in frequency multipliers. Non-linear components, such as diodes, can be used to boost harmonic frequency efficiency. Since the power of harmonics decays rapidly, a frequency multiplier is normally tuned to a small multiple of the input frequency (twice, three times, or five times). To ensure sufficient signal level at the final frequency, amplifiers are usually embedded in a chain of frequency multipliers.

Since tuned circuits have a small bandwidth, if the base frequency is modified substantially (by more than 1%), the multiplier stages can need to be adjusted; this may take a long time if there are several stages. A phase-locked loop (PLL) generates a frequency multiple of a reference frequency. A voltage regulated oscillator (VCO) is tuned to the desired frequency multiple’s range at first. The signal from the VCO is split down by the multiplication factor using frequency dividers. A phase comparator receives the divided signal as well as the reference frequency. The phase comparator’s output is a voltage equal to the phase difference. This voltage is fed to the VCO to change the frequency after passing through a low pass filter and being converted to the correct voltage range. As the phase of the VCO’s signal lags that of the reference signal, the frequency is increased, and as the lag decreases, the frequency is decreased (or lead increases). The VCO will stabilise at the frequency multiple you specify. This particular PLL is a frequency synthesiser.

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