Application method for frequency synthesizer in OFDM system

Abstract

This invention relates to the application method of frequency synthesis device in OFDM system, which is applied extensively in OFDM communication system, and it uses DDS combining with phase-locked loop to provide radio-frequency radical frequency for the frequency circuit in OFDM system. The frequency part directly in OFDM communication system adjusts carrier frequency deviation of the sender and collector. The advantage in this invention is that it has higher frequency differential rate, better phase noise character and wider frequency restricted portion and so on; it changes the output frequency rate of the frequency synthesis device to decrease the communication system carrier frequency deviation and lower the complexity of the synchronous algorithm of the base strip portion. The frequency synthesis device's trimming is obtained by changing DDS's frequency control character with microprocessor. This invention also designs elliptic low pass filter and low loop filter with fountain to provide better phase noise and frequency restricted portion character.

Description

technical field [0001] The invention is a frequency synthesizer that can be widely used in OFDM communication systems. The frequency synthesizer has extremely high frequency resolution and good phase noise characteristics, can adjust the carrier frequency deviation in the communication system according to the needs of customers, and reduce the complexity of the synchronization algorithm of the baseband part of the OFDM communication system. Background technique [0002] OFDM (Orthogonal Frequency Division Multiplexing) is a high-speed transmission technology in a wireless environment. As we all know, the frequency response curve of wireless channels is mostly non-flat, and the main purpose of OFDM technology is to divide a given channel into many orthogonal sub-channels in the frequency domain, use a sub-carrier for modulation on each sub-channel, and each sub-carrier is parallel transmission. In this way, although the overall channel is non-flat a...

AI Technical Summary

Problems solved by technology

However, OFDM technology also has defects: it is very sensitive to frequency offset and phase noise; the peak-to-average power ratio is relatively large, and the increase of this ratio will reduce the efficiency of the RF amplifier

The non-ideal characteristics of DAC include: differential, integral non-linearity, peak current during D / A conversion, limited conversion rate, etc.;

[0011] (2) The error caused by the limited word length of ROM storage data

Since the number of bits stored in the ROM is limited to D, quantization errors will occur during the amplitude quantization process;

[0012] (3) Error caused by phase truncation

[0017] The above scheme does not involve the frequency synthesizer of this OFDM system

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