Emergency announcement call system based on FM/Chirp modulation
A communication and modulator technology, applied in the field of emergency communication system, can solve the problem that it is difficult to meet the number requirements of communication frequency sweeping rules, and achieve high emergency application value and good application effect
Inactive Publication Date: 2012-10-17
周运伟
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Problems solved by technology
Limited by the physical structure of the Surface Acoustic Wave (SAW) device used for Chirp pulse carrier generation and demodulation, traditional Chirp modulation is difficult to meet the quantity requirements for frequency sweep in communication
Method used
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[0016] This embodiment is used to illustrate the parameter selection and application field of the emergency public broadcast system based on FM / Chirp modulation provided by the present invention, such as figure 1 For the system structure shown, its working process can be seen in the related description in the previous part, and will not be repeated here. A kind of typical operating parameter design of this emergency public broadcasting system is as follows: the baseband signal to be modulated is the analog speech that frequency range is 300-3KHz, and the concrete modulation mode that FM modulation is carried out to Chirp pulse carrier in FM / Chirp modulator (11) is Analog linear FM (16F3), the sweep period of the Chirp pulse carrier used in the FM / Chirp modulator (11) is 80 microseconds (the corresponding sweep rate is 12.5K cycle / second), and the narrowband FM receiving terminal (151- 15N) Adopt the receiving carrier channel bandwidth of 25KHz and carry out frequency demodulat...
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The invention relates to an emergency announcement call system based on FM / Chirp modulation and belongs to the emergency communication field. The emergency announcement call system is formed by a FM / Chirp modulator, a power amplifier, a transmitting antenna, narrowband FM receiving terminals and channels which connect the transmitting antenna with the each narrowband FM receiving terminal. A baseband signal to be modulated is input to the FM / Chirp modulator so as to carry out carrier wave modulation. Power amplification is performed on an obtained FM / Chirp modulated carrier wave by the power amplifier, and then the modulated carrier wave is emitted through the transmitting antenna, passes through channel transmission and is taken as an input signal of the corresponding narrowband FM receiving terminals. The narrowband FM receiving terminals demodulate and recover a reduction sample of the baseband signal to be modulated from the received FM / Chirp modulated carrier wave. By using the emergency announcement call system provided in the invention, announcement call covering to a plurality of narrowband carrier wave channels can be realized only through transmitting one FM / Chirp modulated carrier wave. Current narrowband FM receiving equipment can be still used and a working mode does not need to be converted. It is convenient to use a resonance power amplifier to realize large power transmission and long distance covering.
Description
technical field [0001] The invention relates to an emergency broadcast system based on FM / Chirp modulation, which belongs to the field of emergency communication. Background technique [0002] There are three main types of dedicated mobile communication systems: single-frequency conventional, dual-frequency conventional, and trunking. The main mode of group call is to transmit voice or data for dispatching and commanding. In the single-frequency conventional and dual-frequency conventional systems, the terminals of the same talk group wait on the carrier channel of the same frequency; in the trunking system, each terminal in the same talk group waits on the control channel of the base station it accesses. Usually, different talk groups wait on carrier channels of different frequencies, and intercommunication between the talk groups is not required or allowed. However, in the event of an emergency, due to the need for coordinated dispatching and commanding, it is often neces...
Claims
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IPC IPC(8): H04L27/12H04L27/14
Inventor 周运伟
Owner 周运伟