GMSK (Gaussian Filtered Minimum Shift Keying) coherent demodulation method capable of rapidly overcoming Doppler shift

A technology of Doppler frequency shift and coherent demodulation, which is applied in the field of GMSK coherent demodulation that can quickly overcome Doppler frequency shift, can solve the problems of Doppler frequency shift and affect the demodulation effect, and achieve a stable fluctuation range Small, reduce the locking time, improve the effect of locking speed

Active Publication Date: 2018-09-04
GUILIN UNIV OF ELECTRONIC TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] In deep space communication and aerospace measurement and control, the coherent demodulation of Gaussian minimum shift keying (GMSK) modulated signals also faces a problem, that is, due to the high-spee

Method used

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  • GMSK (Gaussian Filtered Minimum Shift Keying) coherent demodulation method capable of rapidly overcoming Doppler shift
  • GMSK (Gaussian Filtered Minimum Shift Keying) coherent demodulation method capable of rapidly overcoming Doppler shift
  • GMSK (Gaussian Filtered Minimum Shift Keying) coherent demodulation method capable of rapidly overcoming Doppler shift

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Embodiment

[0038] According to the characteristics of MSK modulation, the phase change of each symbol cycle is ±πt / 2T b (T b Is the symbol period), then the frequency change of each symbol period in the GMSK signal is:

[0039] f=f c ±t / 4T b (1)

[0040] f L = F c -t / 4T b (2)

[0041] f H = F c +t / 4T b (3)

[0042] Where nT b ≤t≤(n+1)T b , F c Is the carrier frequency.

[0043] Suppose the input signal is: n(t) is noise.

[0044] Such as figure 1 The input signal shown is squared:

[0045]

[0046] Where θ 0 (t)=±πt / 2T b .

[0047] It can be seen from equation (4) that the discrete frequency component of the squared signal is 2f L And 2f H . Such as figure 1 After the square of the input signal shown, the discrete frequency component 2f is obtained by FFT calculation L And 2f H ,Get the carrier f through calculation c The frequency value of is used as the initial value of the VCO in the loop.

[0048] Such as figure 2 The phase detector design shown, there are two numerically controlled oscillat...

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Abstract

The invention discloses a carrier recovery and clock synchronization method of a GMSK (Gaussian Filtered Minimum Shift Keying) signal capable of rapidly overcoming Doppler shift. The method comprisesthe design of a squaring loop as the main structure of a simple receiver. A phase discriminator module, a loop filter module and a digital voltage controlled oscillator module are included. At the same time, in order to increase the locking speed, the carrier frequency of the GMSK signal is estimated to obtain rough carrier frequency, and then a phase-locked loop is used for locking, thereby effectively shortening the locking time and improves the stability of a locked output signal at the same time. Through adoption of the improved squaring loop structure disclosed by the invention, the accuracy of phase error acquisition is increased, and the phase-locked loop works more stably. The method is applied to the fields of spaceflight test control and deep space communication, and can well meet the communication demand standard.

Description

Technical field [0001] The invention relates to the technical field of deep space communication, in particular to a GMSK coherent demodulation method that quickly overcomes Doppler frequency shift. Background technique [0002] In recent years, my country’s aerospace industry has developed by leaps and bounds, and the requirements for aerospace communications have become higher and higher, including the increase in communication data rates and the widening of communication frequency bands. This has also brought about a very significant problem that the frequency band resources are limited. Unrestrictedly increasing the spectrum width of the communication signal will also cause the degradation of signal transmission quality. Taking into account the contradiction between limited communication spectrum resources and people's increasing communication capacity, future modulation methods will develop in the direction of having good spectrum characteristics and higher bandwidth efficienc...

Claims

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Application Information

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IPC IPC(8): H04L27/148H04L27/152H04L27/00H04L7/033H04L7/027
CPCH04L7/0272H04L7/033H04L27/0014H04L27/148H04L27/152H04L2027/0026H04L2027/0053H04L2027/0069
Inventor 唐智灵邹鑫李思敏
Owner GUILIN UNIV OF ELECTRONIC TECH
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