Ultra-low bit rate PSK demodulator for satellite communication system

Abstract

The invention relates to an ultra-low bit rate PSK demodulator for satellite communication system, which consists of a front end A / D conversion module, a digital down converter module, a carrier wave synchronous module and a bit synchronization module; wherein the front end A / D conversion module is made of ready-made product, and the digital down converter module, the carrier wave synchronous module and the bit synchronization module are realized in an FPGA; the connection relationship is that an output of the front end A / D conversion module is connected with the digital down converter module, an output of the digital down converter module is connected with the carrier wave synchronous module, and an output of the carrier wave synchronous module is connected with the bit synchronization module; the moving direction is that an input signal is regulated and then enters into the front end A / D conversion module; after sampling by the front end A / D conversion module, the signal enters intothe digital down converter module to be treated; after that, the signal enters into the carrier wave synchronous module for carrier wave synchronous treatment; then, the signal enters into the bit synchronization module for bit synchronization treatment; finally, the output signal is the output of the demodulator. Therefore, the ultra-low bit rate PSK demodulator has practical value and application prospect.

Description

(1) Technical field [0001] The present invention relates to a demodulator, in particular to an ultra-low code rate phase-shift keying ("phase shift keying" hereinafter referred to as "PSK") demodulator for satellite communication systems, that is, an ultra-low code rate PSK demodulator. Tuner, the invention belongs to the technical field of satellite communication. (2) Background technology [0002] With the development of aerospace technology, my country's deep space exploration strategy has been officially launched, and preliminary results have been achieved. In October 2007, the Chang'e-1 lunar exploration satellite was successfully launched and sent back a large amount of lunar telemetry data. Space, the use of space has taken the first step. At the same time, the success of lunar exploration will lay a technical foundation for our country to carry out deep space exploration. [0003] In the field of deep space communication, for remote control data with small data volum...

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Problems solved by technology

[0004] (1) The spectral line of the data signal overlaps with the phase noise of the root of the carrier, and even submerges the signal spectral line and cannot be demodulated;

[0005] (2) The negative feedback effect of the demodulation phase-locked loop will offset the low-end spectrum of a part of the data signal, thereby reducing the signal-to-noise ratio of the data signal and generating waveform distortion, resulting in an increase in the bit error rate;

[0006] (3) When the code rate is low, the contradiction between acquisition time and carrier loop margin is more serious;

[0007] (4) When the code rate is extremely low, there are only a few bits per second, the bandwidth is extremely narrow, and the front-end filter design is difficult. It is impossible to match the bandwidth design of the front-end filter with the code rate bandwidth. Design a narrowband filter for such a narrow signal Unrealistic, so the actual front-end filter bandwidth will be much larger than the signal bandwidth, and there will be more out-of-band noise entering the demodulator. When the signal-to-noise ratio is low, the total power of the signal remains unchanged, but the signal The effective power will become very small, so the dynamic range of the signal will be large when demodulating

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