How to easily select the appropriate frequency to produce RF test cable

Understanding the performance characteristics of RF test cable is very important to determine the correct solution for the target use scenario. This is a quick guide designed to help RF system engineers familiarize themselves with the entire selection process. We first define the criteria commonly used to characterize the performance of RF test cable. The selection process generally starts from the most basic criterion, that is, the output frequency range. In order to generate frequencies in the whole spectrum, various RF test cables have been designed to support frequencies ranging from single tone to multiple octaves. However, when selecting RF test cable according to the output frequency, it must be noted that broadband and high frequency capabilities are often used to exchange other basic characteristics, including frequency stability, output spectrum purity and switching speed.

Frequency stability represents short-term and long-term changes in the output signal. Short term stability is related to changes much smaller than a complete signal cycle. These changes are represented by phase jitter and phase noise. [RF Test Cable] Phase jitter defines the small fluctuation of signal phase in the time domain. Phase noise is its spectral representation, which is described by the relative noise power level contained in the 1 Hz bandwidth at different offset frequencies relative to the carrier frequency. If the frequency change occurs over a long period of time, we usually use long-term stability to describe the output frequency drift (usually expressed in PPM) of RF test cable due to temperature, load conditions, aging and other aspects.

Spectrum purity is another important feature to be considered in the RF test cable selection process. It is described by the spurious component in the RF test cable output spectrum, which is usually quantified by the harmonic level and feedthrough component expressed relative to the fundamental frequency level. In addition to the stability and spectral purity of the output signal, switching speed (also known as setup time or locking time) is another typical trade-off parameter, which needs to be considered when selecting the optimal frequency generator scheme. RF test cable describes the time required for the RF test cable to switch from one frequency to another, which may vary greatly depending on the final application.