An intermediate frequency demodulation device applied to walkie-talkies

Abstract

The invention discloses an intermediate frequency demodulating device applied to an interphone. The intermediate frequency demodulating device applied to the interphone is formed by connecting a radio frequency module, a data acquisition module, a digital down-conversion module and a demodulation module in sequence. The intermediate frequency demodulating device applied to the interphone mainly solves the demodulating problem of the digital interphone, a two-time frequency conversion radio frequency reception channel of an original simulating interphone is applied, a 4-level frequency shift keying (FSK) signal is demodulated by utilizing a low intermediate frequency signal output by a radio frequency channel, so that the purposes of good demodulation property and production consistency are achieved.

Description

technical field [0001] The invention belongs to the field of digital walkie-talkies, and in particular relates to a device for digitally demodulating and restoring original transmission signals by using low-intermediate frequency signals of traditional analog walkie-talkies. Background technique [0002] With the increasing shortage of spectrum resources, in order to improve spectrum utilization, my country has entered the stage of shifting from analog walkie-talkies to digital walkie-talkies. At present, several mainstream standards of digital walkie-talkies, such as the DMR and DPMR standards of the European Telecommunications Standards Association and the PDT standard independently formulated by my country, all adopt the 4-level FSK debugging method. The modulation method is constant envelope modulation, and two-point modulation is generally used for transmission, which is consistent with the transmission scheme of traditional analog walkie-talkies. For the receiving end...

AI Technical Summary

Problems solved by technology

Among the above two methods, the first method is different from the radio frequency circuit of the traditional analog walkie-talkie, and the cost is higher than that of the original analog walkie-talkie receiving radio frequency.

The second method uses the signal after phase discrimination to make a judgment. In the actual production process, the amplitude of the signal will inevitably have a certain amount of jitter, so using the chip for demodulation and judgment will result in a difference in performance, resulting in Production Consistency Issues

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