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A method of gmsk coherent demodulation to overcome doppler frequency shift rapidly

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: 2021-01-29
GUILIN UNIV OF ELECTRONIC TECH
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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-speed relative motion of the GMSK signal in the transmission between the aircraft and the ground receiver, it will cause Doppler The appearance of Le frequency shift, which greatly affects the demodulation effect

Method used

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  • A method of gmsk coherent demodulation to overcome doppler frequency shift rapidly
  • A method of gmsk coherent demodulation to overcome doppler frequency shift rapidly
  • A method of gmsk coherent demodulation to overcome doppler frequency shift rapidly

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Embodiment

[0038] According to the characteristics of MSK modulation, the phase change of each symbol period 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] like figure 1 The input signal shown is squared:

[0045]

[0046] where θ 0 (t)=±πt / 2T b .

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

[0048] like figure 2 In the design of the phase detector shown, ther...

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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 for quickly overcoming 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 frequency band resources are limited. Unlimited increase in the spectrum width of the communication signal will also cause a decrease in the quality of signal transmission. Considering the contradiction between limited communication spectrum resources and people's increasingly large communication capacity, future modulation methods will develop in the direction of having good spectrum characteristics and high bandwidth efficiency. ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
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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