Читать книгу Handbook of Microwave Component Measurements - Joel P. Dunsmore - Страница 80

While not a measurement instrument in their own right, signal sources or signal synthesizers, or simply sources, are used as accessory equipment in a variety of measurement tasks. They can provide CW signals in place of a mixer LO or provide an input signal to an amplifier or filter. These are typically called analog sources, and their key attributes are frequency range, output power range (minimum and maximum), phase noise and spectral purity, and frequency switching speed.

While the first two attributes are obvious, the phase noise and spectral purity are key attributes when making measurements close to the carrier such as IMD measurements or when making other distortion measurements such as harmonics.

Switching speed becomes important in automated test systems (ATSs) when using the source as a swept frequency stimulus. Commonly, stand‐alone signal sources make a trade‐off between lower‐phase noise and slower switching speeds.