Frequency offset following search method

Abstract

The invention discloses a frequency-offset-following channel search method. A judgment is made by using a coherent detection means, and namely whether a frequency offset obtained through demodulation has the following characteristic. The frequency-offset-following channel search method comprises the following steps that after a signal passes through a low-pass channel selective filter with the bandwidth not smaller than 180 KHz, whether a search frequency point is an effective radio station is judged primarily according to comparison between an in-band RSSI result and a set threshold value, and the step size in search is selected; station search is conducted according to the time frequency offset characteristic of the step size in search; if three frequency offsets which correspond to three adjacent effective frequency points and are found from small to large are judged as effective radio station conditions, standard quantization is conducted according to FM frequency points, and actual frequency points are obtained; according to the found frequency points of two stations, the step size in search is adjusted. As a result, the purpose that the stations are accurately identified is achieved.

Description

technical field [0001] The invention relates to the field of frequency modulation of radio stations, in particular to a method for searching stations following frequency deviation. Background technique [0002] At present, the FM frequency range in Russia is: 64~108MHz, and the frequency between stations is an integer multiple of 30KHz; other FM systems are 76~108MHz, except that the frequency between stations in Southeast Asia is an integer multiple of 50KHz, and most of them are integer times of 100KHz. . Usually, only one of the methods is used in a region. Of course, special multiples may appear, such as the border between China and Russia, and 30KHz step and 50KHz step may appear at the same time. [0003] The mainstream channel search strategy is a combination of the following two aspects: [0004] According to the received signal strength indicator RSSI result is compared with a threshold to determine whether it is a station, the disadvantage of this scheme is that,...

AI Technical Summary

Problems solved by technology

[0005] (1) Since FM itself is not a completely bandwidth-limited system, it is likely that weak stations near strong stations will be covered

[0006] (2) Since the RSSI method is a non-coherent detection method, if there is non-FM interference in the FM frequency band, if the detected RSSI exceeds the threshold, it will be judged as a station, and the fact is noise, resulting in misjudgment