sweep generator[′swēp ‚jen·ə‚rād·ər]
a measuring generator at whose output the frequency of the electric oscillations automatically changes in accordance with a given law. For example, a sinusoidal or sawtooth wave form may be produced. Such generators are usually employed in measuring apparatus used to record the amplitude-frequency and phase-frequency characteristics of components of microwave equipment and to measure such quantities as the standing wave ratio and impedance as functions of frequency. When used in conjunction with an oscilloscope, a sweep generator permits visual observation of the characteristics of the objects being studied.
The components of a sweep generator include a driving oscillator, a frequency modulator, an automatic system for controlling the output voltage or power, and a resonance frequency meter (or a crystal calibrator), which provides frequency marker pips on the screen of the oscilloscope. Sweep generators permit the obtaining of frequency swings in various regions of the electromagnetic spectrum from several megahertz to hundreds of gigahertz. The relative frequency instability during a measurement time of 1–2 min is 10-5-10-4. The sweep width can be as large as an octave. For microwave frequencies, the sweep width is not less than the passband of a standard wave guide. The time required for frequency retuning is 0.02–40 sec; at the lowest frequencies this time can reach several tens of minutes. The output power of a sweep generator is 1–10 milliwatts.
REFERENCESValitov, R. A., and V. N. Sretenskii. Radiotekhnicheskie izmereniia. Moscow, 1970.
Kushnir, F. V., V. G. Savenko, and S. M. Vernik. Izmereniia v tekhnike sviazi. Moscow, 1970.