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Whole phase FFT based universal demodulation method

A demodulation method and full-phase technology, applied in the field of demodulation, can solve the problems of consuming large system resources and estimator affecting system performance, and achieve the effect of simplifying the demodulation circuit

Inactive Publication Date: 2008-03-05
TIANJIN UNIV
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Problems solved by technology

[0019] (3) One of the shortcomings of the OFDM system: accurate channel estimation is required
Therefore, channel estimation will consume a lot of system resources, and the estimation bias of the estimator will also affect the performance of the system.

Method used

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Examples

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Embodiment Construction

[0084] The following is a concrete example of demodulating 64QAM to illustrate the demodulation process of all-phase FFT used in this paper.

[0085] It is assumed that the parameters of the 64QAM modulated signal are: symbol rate fb=10kbit / s, carrier frequency fc=500kHz.

[0086] The demodulation block diagram based on all-phase FFT is shown in Figure 10, and the process is as follows:

[0087] 1. Selection of A / D conversion sampling frequency.

[0088] The choice of sampling frequency should meet two conditions:

[0089] A sampling theorem (fs≥2*fc)

[0090] B To obtain an accurate frequency estimate, select the number of points N of the all-phase FFT to be equal to 512. The input sampling points required for all-phase FFT and all-phase time-shift phase difference method correction are 3N, so the sampling frequency is required to be fs≥3×N×fb= 15.36MHz.

[0091] Here fs=20MHz is chosen.

[0092] 2. Selection of all-phase FFT and spectrum correction input sequences

[0...

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Abstract

The general demodulation (DEMOD) method includes steps: under precondition of accorded with sample theorem, full phases FFT, and required corrected sampling points to select A / D conversion for the sampling frequency (FR); selecting sequence needed by full phases from the sampling sequences, and then based on FR spectrum correction (FSC) technique to select the correction sequence; carrying out FFT in full phases for the selected sequence, and meanwhile based on the selected FSC technique to carry out FSC so as to accomplish demodulation (MOD); using planisphere-mapping to accomplish decoding. Since DEMOD is based on full phases FFT, the algorithm for correcting and accurate estimating FR, phase, and amplitude is simple so as to simplify DEMOD circuit. Features are high resolution for estimating FR and phase, and low error rate. The invention is suitable to multiple MOD modes including different distributions of planisphere so as to be in favor of generalization of demodulator.

Description

technical field [0001] The invention belongs to the demodulation technology in the digital communication system, and further relates to a general demodulation method based on all-phase FFT. Background technique [0002] Modulation technology is one of the essential key technologies in communication systems. With the rapid development of communication technology today, it is not limited to using a single modulation method in the same system, but according to different channels and transmission requirements, QoS Wait to flexibly choose a variety of modulation methods, which is called adaptive modulation technology. The demodulation technology is the process of recovering the eigenvalues ​​of the modulated signal and reconstructing the modulated signal by using the process opposite to the modulation. For different modulation techniques, corresponding demodulation techniques are adopted. [0003] Digital modulation and demodulation technology (digital modulation and demodulati...

Claims

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Application Information

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IPC IPC(8): H04L27/26
Inventor 侯春萍丁丽娅王兆华侯永宏孙山林
Owner TIANJIN UNIV
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