Frequency conversion is the primary function of superheterodyne communication and radar circuits as well as many other useful RF/microwave devices. For these nonlinear devices, especially in the role of mixers, frequency multipliers and frequency dividers, and how to select the best device for an application, this is often confusing. This paper aims to briefly describe the similarities and differences between the above various devices, and to explain the device selection criteria. What is a mixer? A mixer is a non-linear three-terminal device that typically consists of a diode or transistor that operates in a non-linear region. The mixer adds and subtracts two input signals and outputs their sum and difference. Depending on the configuration, this function can be used for upconversion, downconversion, IQ mixers, or different performance parameters. Mixers are commonly used in demodulation circuits, upconverters and downconverters to perform frequency conversion before or after transmission. What is a frequency multiplier? A frequency multiplier is a nonlinear device that generates higher frequency harmonics based on the performance of the input signal. For example, a double frequency multiplier is a frequency multiplier that produces strong second harmonics. Inevitably, the input signal, higher harmonics, and noise/interference will also leak and mix into the output signal. Frequency multipliers are commonly used in demodulation circuits to increase the frequency of the oscillator or signal generation source. What is a crossover? The frequency divider is similar to the frequency multiplier, except that the input signal frequency is an integer multiple of the output frequency. The divider is the same as the multiplier. What should I pay attention to when selecting a multiplier or crossover? Frequency multipliers and frequency dividers are versatile, and for some applications, isolation, harmonic rejection, and phase noise characteristics are important considerations when selecting a frequency multiplier or divider. Isolation indicates the ability of the multiplier or divider to prevent the input signal from leaking to the output, while harmonic rejection is the ability of the frequency multiplier or divider to prevent harmonics of the input signal from appearing at the output. These two factors have a direct impact on the usability of the frequency multiplier or crossover and are therefore important. For signal generation and modulation circuits that have limitations on noise, phase noise, or interference, the additive phase noise and noise performance of the frequency multiplier or divider is important because these parameters can be added to the output signal when it is generated. Input signal. In addition to the above, since some frequency multipliers and frequency dividers require a large input power, the amount of signal power required to drive the frequency multiplier or frequency divider or the signal input power required for normal operation sometimes becomes one. The factors that need to be considered. Many test and measurement grade precision and arbitrary waveform generators do not produce the signal strength required to drive a multiplier or divider. In this case, it may also be necessary to use an amplifier with its own distortion, noise, and phase noise characteristics. Dongguan Yijia Optoelectronics Co., Ltd. , https://www.everbestlcdlcms.com