Types of signal generator (1)

Sinusoidal signal generator
Sinusoidal signal generator: The sine signal is mainly used to measure the frequency characteristics, nonlinear distortion, gain and sensitivity of circuits and systems. According to the frequency coverage, it is divided into low frequency signal generator, high frequency signal generator and microwave signal generator; according to the adjustable range and stability of output level, it is divided into simple signal generator (ie signal source) and standard signal generator (output The power can be accurately attenuated to below -100 decibel milliwatts) and power signal generator (the output power is more than tens of milliwatts); according to the way of frequency change, it is divided into tuned signal generator, frequency sweep signal generator, and program control Signal generator and frequency synthesis signal generator, etc.

Low frequency signal generator
Includes sine wave generators in the audio (20 to 20,000 Hz) and video (1 to 10 MHz) ranges. The main vibration level generally uses an RC type oscillator, and a difference frequency oscillator can also be used. In order to facilitate testing the frequency characteristics of the system, it is required that the output amplitude-frequency characteristics be flat and the waveform distortion is small.

High frequency signal generator
A high frequency signal generator with a frequency of 100 kHz to 30 MHz and a VHF signal of 30 to 300 MHz. The LC tuned oscillator is generally used, and the frequency can be read from the dial scale of the tuning capacitor. The main purpose is to measure the technical indicators of various receivers. The output signal can be amplitude-modulated or frequency-modulated by an internal or external low-frequency sinusoidal signal, so that the output carrier frequency voltage can be attenuated below 1 microvolt. (Figure 1) The output signal level can be accurately read, and the added amplitude or frequency deviation can also be read with an electric meter. In addition, the instrument has a good shield against signal leakage.

Microwave signal generator
Signal generator from decimeter wave to millimeter wave band. Signals are usually generated by UHF transistors and reflective klystrons with distributed parameter resonators, but they are gradually being replaced by solid-state devices such as microwave transistors, field-effect transistors and Gunn diodes. The instrument generally changes the frequency by mechanically tuning the cavity, and each unit can cover about one octave. The signal power coupled out of the cavity can generally reach more than 10 milliwatts. The simple signal source only needs to add 1000 Hz square wave amplitude modulation, while the standard signal generator can adjust the output reference level to 1 milliwatt, and then read the decibel milliwatt value of the signal level from the following attenuator; it must also There are internal or external rectangular pulse amplitude modulation to test radar and other receivers.