frequencymultiplier

A frequency multiplier, sometimes written as frequencymultiplier, is a circuit or device that generates an output signal at a frequency that is an integer multiple of the input frequency. The technique relies on the nonlinearity of a device to produce harmonics of the input signal, from which a desired multiple is selected by filtering.

Most implementations use nonlinear elements such as diodes or transistors to create a spectrum containing the fundamental and many harmonics. A nonlinear network drives a filter that isolates the targeted harmonic, yielding an output at n times the input frequency. Efficiency, spectral purity, and noise performance depend on the order of the multiplier, drive level, and the quality of impedance matching and filtering. Higher multiples are typically less efficient and generate more phase noise and spurious content.

Common types include passive frequency multipliers, such as diode-based doublers and triplers, and active multipliers that exploit transistor nonlinearities. Some designs use cascaded stages to achieve higher multiples, sometimes paired with amplification between stages to maintain output level.

Applications of frequency multipliers are prominent in radio frequency and microwave engineering. They are used in local oscillators and frequency synthesizers, radar and microwave communications systems, and instrumentation where stable, tunable high-frequency signals are required. In synthesizer architectures, multipliers are often combined with phase-locked loops to achieve precise, low-noise output across a wide frequency range.

Key considerations in design include conversion loss, harmonic suppression, phase noise, and power handling, as well as careful impedance matching and filter design to minimize unwanted spurs and distortion. See also frequency synthesizer and phase-locked loop.