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The working principle of the interphone

Category:Industry dynamic  Date:2013-12-05  Views:1432   [back]
The emission part
Phase locked loop and voltage controlled oscillator (VCO) generates the RF carrier signal is emitted, through the buffer amplifier, excitation amplification, power amplifier, RF power rating, the antenna through the low pass filter, harmonic component, and then through the antenna.
The receiving part
The receiving part two times conversion superheterodyne, signals from the antenna input after receiving conversion circuit and a band-pass filter for RF amplification, after a bandpass filter, into a mixer, amplifier signal from the RF PLL frequency synthesizer circuit from the first local oscillator signal and generate a first intermediate frequency signal in the first the mixer is mixing. The first intermediate frequency signal through the crystal filter to eliminate the clutter signal adjacent channel. The first intermediate frequency signal after filtering into intermediate frequency processing chip, the second intermediate frequency signal and the second local oscillator signal mixing generation again, second intermediate frequency signal through a ceramic filter to remove the unwanted spurious signals, amplified and phase frequency, the audio signal. An audio signal amplification, bandpass filter, de emphasis circuit, entering tone
Volume control circuit and the power amplifier, driving a speaker, get the information which people need.
Signaling processing human voice is converted into electrical signals by a microphone audio, audio signal through the amplifying circuit, the pre emphasis circuit and a band-pass filter into VCO direct modulation.
CPU generates a CTCSS/DTCSS signal after amplification adjustment, into VCO modulation. Low frequency signal is received after the frequency discriminator, a portion of the amplification and sub audio bandpass filter shaping, enter the CPU, compare with the preset value, the result control audio power amplifier and the loudspeaker output. If with the preset values are the same, then open the speaker, if different, closing a speaker.
Both the intercom application security inspections, or when traveling communicate, play seems cannot do without the walkie talkie. But, why can the walkie talkie wireless intercom, its working principle and everyone knows how much? The principle we explain the walkie talkie.
The working principle of walkie talkie:
1, the emission part:
Phase locked loop and voltage controlled oscillator (VCO) generates the RF carrier signal is emitted, through the buffer amplifier, excitation amplification, power amplifier, RF power rating, the antenna through the low pass filter, harmonic component, and then through the antenna.
2, the receiving part:
The receiving part two times conversion superheterodyne, signals from the antenna input after receiving conversion circuit and a band-pass filter for RF amplification, after a bandpass filter, into a mixer, amplifier signal from the RF PLL frequency synthesizer circuit from the first local oscillator signal and generate a first intermediate frequency signal in the first the mixer is mixing. The first intermediate frequency signal through the crystal filter to eliminate the clutter signal adjacent channel. The first intermediate frequency signal after filtering into intermediate frequency processing chip, the second intermediate frequency signal and the second local oscillator signal mixing generation again, second intermediate frequency signal through a ceramic filter to remove the unwanted spurious signals, amplified and phase frequency, the audio signal. An audio signal amplification, bandpass filter, to add into the volume control circuit, amplifier, circuit and power amplifier to drive a loudspeaker, get the information which people need.
3, the modulated signal and the modulation circuit:
The speech is converted to electrical signals by a microphone audio, audio signal through the amplifying circuit, the pre emphasis circuit and a band-pass filter into VCO direct modulation.
4, signaling processing:
CPU generates a CTCSS/CDCSS signal after amplification adjustment, into VCO modulation. Low frequency signal is received after the frequency discriminator, a portion of the amplification and sub audio bandpass filter shaping, enter the CPU, compare with the preset value, the result control audio power amplifier and the loudspeaker output. If with the preset values are the same, then open the speaker, if different, closing a speaker.
Radio frequency limit
In order to ensure that the vast majority of users call is not disturbed and rational use of frequency resources, the division of the use of National Radio Management Committee on the frequency, the frequency range of the corresponding provisions of the use of different industries. When users buy Walkie Talkie Radio Management Committee, to apply for local frequency.
Public interphone refers to: the transmit power is less than 0.5W, the wireless interphone in specified frequency, the radio frequency, power RF technical specifications shall meet the following requirements:
1, the working frequency (.9000; 409 unit: MHz): 409.7500, 409.7625, 409.7750, 409.7875, 409.8000, 409.8125, 409.8250, 409.8375, 409.8500, 409.8625, 409.8750, 409.8875, 4099125, 409.9250, 409.9375, 409.9500, 409.9625, 409.9750, 409.9875;
2, modulation mode: F3E;
3, effective radiated power (EIRP): 0.5W;
4, emission frequency tolerance: <+5ppm;
5, the radiation transmitter spurious: <50uW;
6, the receiver: <20nW stray radiation;
7, the channel spacing: 12.50kHz
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