Four types of signal generators

Signal generator is a common signal source widely used in electronic circuits, automatic control systems and digital experiments. Circuits that can generate various waveforms, such as triangle waves, sawtooth waves, rectangular waves (including square waves), sine waves, etc.

1. Types of signal generators:

Signal generators are generally divided into two categories: dedicated signal sources and general signal sources. General signal generators include: high-frequency signal generators, pulse signal generators, function signal generators and noise signal generators.

2. Functional classification of signal generators

1. Divided by frequency band

Ultra-low frequency (0, 001 ~ 1000Hz) signal generator; low frequency (1Hz ~ 1MHz) signal generator; video (20Hz ~ 10MHz) signal generator; high frequency (0, 1 ~ 30MHz) signal generator; very high frequency ( 30~300MHz) signal generator; ultra-high frequency (300~1000MHz) signal generator; microwave (above 1GHz) signal generator. Although divided into the above types according to frequency bands, many signal generators can operate within an extremely wide frequency range. For signal generators with frequencies ranging from tens of kilohertz to 1GHz or higher, such as HP8642A/B, Fluke's 6071 and other signal generators, it is difficult to classify them as signal generators in that frequency band. Therefore, signal generators are often simply divided into the following types in use: low-frequency signal generators, with frequencies below 1 MHz; radio frequency signal generators, with frequencies from tens of kilohertz to 1 GHz; microwave signal generators, with frequencies above 1 GHz.

AFG3021C arbitrary waveform/function signal generator

2. According to the output waveform

①Sinusoidal signal generator. A signal generator whose output varies with time in a sinusoidal (or cosine) relationship. This type of signal generator is the most widely used, has the largest number, and has the widest frequency range (from very low frequency to microwave frequency band).

②Function generator. A signal generator whose frequency is continuously adjustable within a wide range and can output various waveforms such as square wave, triangle wave, sine wave, sawtooth wave, double pulse wave, trapezoidal wave, etc. Its frequency band is very wide, and it is suitable for automatic control, debugging and maintenance of electronic equipment as well as ultra-low frequency sine wave signal generator.

③Pulse signal generator. Refers to the rectangular pulse generator, the basic output signal is a rectangular pulse. Its main working characteristics are repetition frequency, pulse width, pulse amplitude, rise time and overshoot, etc. The output polarity is often convertible.

④Other types of signal generators, such as the CA102S analog signal generator produced by Shaoxing Zhongyi, can simulate output of 4-20mA, 1~5V, 0~400 ohm resistance, etc.

3. According to performance

(1) Signal generator

Used to provide high frequency energy for measurement and testing of test equipment or other electronic equipment. The output power is large and the performance requirements are average. This type of equipment is a signal generator, or a simple signal generator.

From the user's point of view, this type of signal generator is used to provide a radio signal, the strength of which can be adjusted according to the user's needs without knowing its value precisely. Signal generators used for this type of purpose usually Metrological verification is not necessarily required.

(2)Standard signal generator

For a standard signal generator, the output signal frequency is required to be stable, the level and amplitude are stable, the modulation coefficient is adjustable within a certain range, the reading is accurate, and the shielding is good. The output voltage of a standard signal generator is usually very small, and it can output a precise and small enough voltage (microvolt level) to meet the needs of measurement and testing. As a measuring instrument, this kind of signal generator must know the exact values ​​of each parameter, so it must be calibrated, otherwise the accuracy of the test cannot be guaranteed.

4. According to modulation type

The signal generator used in testing often needs to provide signals with a certain modulation form. Therefore, the signal generator can be divided into amplitude modulation, frequency modulation, pulse modulation and combined modulation according to the modulation type. High frequency signal generators are generally amplitude modulated, VHF signal generators should have amplitude modulation and frequency modulation, and UHF and microwave signal generators should have pulse modulation.

In addition, it can be divided into ordinary signal generators, sweep signal generators and program-controlled signal generators according to the method of generating frequency. The latter two are widely used in automatic or semi-automatic test systems.

Puyuan arbitrary waveform generator DG4202

3. Composition of signal generator

Oscillator: This is the core component of the signal generator, which refers to the different waveforms and signals of different frequencies it generates. Generally speaking, there are huge differences in the principles and structures of oscillators with different waveforms and different frequency band signals.

Converter: This varies according to different use cases and can be a power amplifier, voltage amplifier or shaper. The signal output by the oscillator is usually very weak and needs to be amplified. For example, frequency modulation and amplitude modulation are required to modulate the signal to modulate the carrier frequency. As for the function generator, the output of the oscillator is generally a triangle wave, which requires a shaping circuit to shape it into a sine wave or square wave.

Indicator: This is the function of monitoring the output signal. It can be a power meter, voltmeter, frequency meter, etc. Some pulse signal generators have a simple oscilloscope. The amplitude, frequency and other characteristics of the output signal can be adjusted through the indicator. wait.

Output stage: This is used to adjust the output signal level and output impedance. It can be an attenuator, matching transformer, emitter follower, etc.

Power supply: generally refers to the working power supply voltage provided to various parts of the signal generator.

DG800 function/arbitrary waveform generator

4. The function of signal generator

In actual work, signal generators generally perform the following functions:

1. Detect the parameters of components: such as inductance, capacitance value and quality factor, etc.;

2. Detect the phase frequency/amplitude frequency of the network: change the frequency of the signal source and measure the network response through an oscilloscope, which is a test of sinusoidal steady-state excitation and point frequency;

3. Detect the transient response of the network: use square wave or narrow pulse excitation to detect the time constant and impulse response of the network;

4. Calibrate the instrument: Calibrate the attenuator, gain and scale of the electronic instrument by outputting frequency, amplitude and other signals.