A Frequency Modulation System Realizing Wide Range Modulation Depth Compensation

Abstract

The invention discloses a frequency modulation system for realizing wide-range modulation depth compensation, which includes a frequency synthesizer (100) and an analog modulation voltage generation module (200) with built-in depth modulation compensation; the frequency synthesizer can set programmable decimal points through channel selection The frequency converter (6) generates the carrier signal of the corresponding frequency, and then the configurable loop filter (3) can be programmed to realize loop disconnection; the analog modulation voltage generation module sets the quantization voltage range of the digital-to-analog converter through channel selection, and the digital-to-analog The converter (8) converts the digital modulation signal into an analog voltage signal and filters it through a low-pass filter (7), then the modulation capacitor realizes the conversion from voltage characteristics to capacitance characteristics, and finally the LC oscillator (4) realizes the frequency modulation function. The invention has a built-in wide-range modulation depth compensation function, realizes multi-code rate, multi-channel single modulation depth communication, and the loop is disconnected during modulation to reduce carrier noise and signal distortion.

Description

technical field [0001] The invention mainly relates to the field of frequency modulation design, in particular to a frequency modulation system structure using a frequency synthesizer for frequency modulation to realize multiple code rates, multiple channels and single frequency modulation depth. Background technique [0002] With the increasing development of wireless communication technology, the frequency range of radio frequency system communication continues to expand, and the number of communication channels continues to increase. As a result, how to achieve consistent frequency modulation depth under the same code rate and the same communication protocol has become the main problem in the design of the transceiver system. The problem. [0003] The traditional frequency modulation function is mainly realized by PLL structure. First, the frequency of the carrier signal is determined according to the channel selection signal, and a high-frequency carrier signal of the c...

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Problems solved by technology

[0007] With the continuous increase of communication channels, the carrier frequency continues to increase, making the effective capacitance C corresponding to the carrier frequency 0 also gradually decreases, but the modulation capacity △C for frequency modulation remains unchanged. According to the formula (1), it can be seen that the modulation depth will become larger and larger, resulting in an increase in the working bandwidth of the digital processing module and an increase in design difficulty.

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