frequency multipliers are nonlinear devices that produce an output signal with a frequency that is larger than the frequency of a corresponding input signal by a predetermined factor. RF frequency multipliers operate over a specific input frequency range and are able to suppress or reduce unwanted harmonics from the output signal. There are two basic types of devices: active and passive. Active RF multipliers produce an output signal with a power level that is larger than that of the input signal. The power level difference between the output signal and the input signal is called conversion gain, an amount that is measured in decibels (dB) and expressed as a positive number. Passive RF multipliers produce an output signal with a power level that is smaller than that of the input signal. The difference in power levels between the output signal and the input signal is called conversion loss, an amount that is expressed in decibels. Conversion loss is a negative number, but usually specified as an absolute value.
Performance specifications for RF frequency multipliers include multiplying factor, input power, output power and spurious rejection. Frequency doublers, triplers, quadruplers and quintuplers are commonly available. Input power is the amount of RF power that must be applied to a device in order to multiply the frequency of the input signal. It is also the specified power range for the conversion loss. Both output power and input power are expressed in decibels relative to one milliwatt (dBm). Spurious rejection is the difference between the desired output harmonic and any other harmonic as viewed at the RF multiplier’s output. It is usually expressed as a positive ratio in decibels relative to the carrier power (dBc).