- May 10, 2017 -
Walkie - talkie
Walkie - talkie It is a two-way mobile communication tool, without any network support in the case, you can call, no calls generated for relatively fixed and frequent calls occasions. There are three major categories of walkie-talkie: analog walkie-talkie, digital walkie-talkie, IP radio.
Walkie - talkie working principle
The working principle of the walkie-talkie is as follows:
1, Walkie - talkie the launch part:
The phase-locked loop and the VCO generate the radio frequency carrier signal, which is buffered to amplify, amplify the amplifier, generate the rated RF power, pass the antenna low-pass filter, suppress the harmonic component, and then emit it through the antenna The
2, Walkie - talkie the receiving part:
The receiving section mixes the amplified signal from the radio frequency with the first local oscillator signal from the phase locked loop frequency synthesizer circuit at the first mixer and generates a first intermediate frequency signal. The first intermediate frequency signal further eliminates the adjacent channel clutter signal through the crystal filter. The filtered first intermediate frequency signal enters the intermediate frequency processing chip, and then mixes with the second localized signal to generate the second intermediate frequency signal. The second intermediate frequency signal is filtered out by a ceramic filter to filter the unwanted spurious signal, Generate an audio signal. Audio signal through the amplification, band-pass filter, to increase the circuit, into the volume control circuit and power amplifier to enlarge, drive the speaker, get the information people need.
3, Walkie - talkie modulation signal and modulation circuit:
The voice of a person is converted into audio by a microphone
4, Walkie - talkie signaling processing:
CPU generated CTCSS / CDCSS signal through the amplification adjustment, into the voltage-controlled oscillator for modulation. Receive the frequency spectrum obtained after receiving the frequency, part of the amplified and sub-audio band-pass filter to filter shaping, into the CPU, compared with the default value, the results control the audio amplifier and speaker output. That is, if the same as the preset value, then open the speaker, if different, then turn off the speaker.