What is the principle of function signal generator?
The function signal generator can be used to test or repair the frequency characteristics, gain, and passband of low-frequency amplifiers in various electronic instruments and equipment. It can also be used as an external modulation signal source for high-frequency signal generators. As the name implies, it can definitely generate a functional signal source, such as a sine wave of a certain frequency, some of which can output voltage and some of which can output power. Below we use a simple example to illustrate the principle of the function signal generator.
Structural composition:
The signal generator system mainly consists of the following parts: main oscillator stage, main oscillator output adjustment potentiometer, voltage amplifier, and output attenuation. amplifier, power amplifier, impedance converter and indicating voltage
Working mode:
When a small signal sine wave is input to the input end, the signal is transmitted in two ways, one of which The path loop completes the rectification and voltage doubling function and provides working power; the other path is capacitively coupled and enters the input end of an inverter to complete the signal amplification function. The amplified signal is processed by the gate circuit of the subsequent stage, converted into a square wave and then output. The output terminal is an adjustable resistor.
Work flow:
First, the main oscillator stage generates a low-frequency sinusoidal oscillation signal. The signal needs to be amplified by a voltage amplifier. The amplification factor must meet the requirements of the voltage output amplitude. Finally, the signal is attenuated by the output The signal device can directly output the voltage that the signal device can actually output. The size of the output voltage can be specifically adjusted using the main oscillator output adjustment potentiometer.
It is generally managed by a microcontroller, mainly to achieve the following functions:
a) Control the frequency generated by the function generator;
b ) Control the waveform of the output signal;
c) Measure the output frequency or measure the frequency of the external input and display it;
d) Measure the amplitude of the output signal and display it;
e) Control the output of a single pulse.
Principles of signal transmitters and receivers
1. Working principle of signal transmitter:
The signal generator is used to generate sinusoidal signals with a frequency of 20Hz to 200kHz. In addition to voltage output, some also have power output. Therefore, it has a wide range of uses. It can be used to test or repair the frequency characteristics, gain, and passband of low-frequency amplifiers in various electronic instruments and equipment. It can also be used as an external modulation signal source for high-frequency signal generators. The radio frequency part is composed of a signal receiving part and a signal transmitting part.
In addition, it can provide AC signal voltage when calibrating the electronic voltmeter. Principle of low-frequency signal generator: The system includes the main oscillator stage, main oscillator output adjustment potentiometer, voltage amplifier, output attenuator, power amplifier, impedance transformer and indicating voltmeter.
The main oscillator stage generates a low-frequency sinusoidal oscillation signal, which is amplified by the voltage amplifier to meet the voltage output amplitude requirements. The voltage can be directly output through the output attenuator, and the output voltage can be adjusted with the main oscillator output adjustment potentiometer.
2. Receiver principle:
Its function is opposite to that of the transmitter. It mainly receives the signal in the channel and transforms it into the same physical form as when it was sent. The information is then transmitted to the sink, which completes the so-called decoding process. The basic requirement of the receiver is to be able to maximize the extraction of information output from the source from the interfered signal and to reproduce the output of the source as much as possible.
Satellite TV receiver, commonly known as "pot", is a device that can receive satellite TV programs. It consists of a parabolic antenna, feed, tuner, and satellite receiver.
Satellite TV receivers have provided great convenience for some rural areas to understand external information, but they have also caused certain hidden concerns. There are two types of satellite receivers: forward-feed antennas and offset-feed antennas. The forward-feed antenna has a larger reflecting surface area, so it is commonly called a "big pot"; the opposite offset-feed antenna has a smaller reflecting surface area, which is called a "small pot" or "small pot". "Little ears".
Extended information:
Signal transmitter structure:
1. Internally equipped with frequency sweep output function
Refers to the generation of low-frequency signals The device has the function of automatically changing from low frequency to high frequency, that is, it can complete the changing process of all frequencies from low to high or high to low between 100Hz and 20KHZ, and the time of this process is 5 seconds.
2. With external frequency sweep control input interface
It means that the frequency output by the low-frequency signal generator can be controlled externally, and the voltage for external control frequency change is 0-5V , the control current is less than 1mA. When the external control voltage changes between 0-5V, the output of the low-frequency signal generator can change between 100HZ and 20KHZ.
Reference materials: Baidu Encyclopedia - Signal Generator
Baidu Encyclopedia - Receiver
The principle of photoelectric signal generator
Signal The generator is mainly composed of two light-emitting diodes, two photosensitive diodes and electronic circuits. The two light-emitting diodes are facing the photosensitive diodes respectively, and the light-emitting diodes use the photosensitive diodes as the irradiation target.
The signal disk is located between the light-emitting diode and the photosensitive diode. When the signal disk is running, the light hole on the signal disk causes alternating light transmission and light blocking. When the light beam of the light-emitting diode shines on the photosensitive diode, the photosensitive diode is sensitive to light and On; when the light beam of the light-emitting diode is blocked, the photosensitive diode is cut off so that the signal generator can generate a pulse voltage signal, which is then sent to the electronic circuit for amplification and shaping and then output to the control circuit.
Magnetic induction type The signal generator consists of specific bumps on the moving rotor, a fixed induction coil and electronic circuits. When the bumps are close to the induction coil, the magnetic field intensity increases and an induced voltage signal is generated. When the bumps are far away from the induction coil, the magnetic field becomes weaker. , the signal voltage becomes smaller and the pulse signal is then sent to the electronic circuit for amplification and shaping before being output to the control circuit.
The photoelectric signal has good sensitivity, is not easily affected by the performance of the component, and has good working stability. High cost.
Magnetic induction signal has poor sensitivity, low cost and durability
Principle of audio signal generator
Principle of audio signal generator:
The audio signal generator is actually a triode oscillator circuit. It has two principles, one is LC oscillator and the other is RC oscillator.
Take the RC oscillator as an example. The circuit is simple, easy to start and has high efficiency. Circuit principle: BG1 is an NPN low-power high-frequency tube, and BG2 is a PNP low-power low-frequency tube. When the power switch K is just turned on, the two transistors are not yet turned on. The power supply charges the capacitor C through R1, R2, and RL. The voltage across C rises exponentially. When this voltage rises to the threshold voltage for the tube to turn on, BG1BG2 starts to conduct. Then a positive feedback process occurs:
When UC rises, IB1 rises, IC1 rises, UC1 falls, UB2 falls, UC2 rises, UB1 rises, and UC1 falls. This process immediately saturates BG1BG2. Capacitor C then discharges via R2 through the BG1 emitter junction and BG2 collector emitter. As the discharge proceeds, the following positive feedback process occurs:
The decrease in UC causes IB1 to decrease, which causes UC1 to increase, which causes UB2 to increase, which causes UC2 to decrease, which causes UC1 to increase and UB1 to decrease. As a result, BG1BG2 quickly returns to its original cut-off state. By repeating this process over and over again, a rectangular pulse signal is obtained on the load resistor, which can drive a speaker to produce sound. Adjusting the resistor value of R1 can change the frequency of the oscillator.