Carrier wave catching system and method based on multimode operation

Abstract

A novel carrier capture and tacking method synchronously a pilot frequency and PN sequence based on multi-state control to achieve synchronous larger carrier deviation capture scope, higher carrier capture precision and more robust carrier capture reliability. In detail, it is necessary to adopt a plurality of carrier capture methods at the same time, dynamically judge estimated state of the carrier and select a suitable carrier capture method and a corresponding hardware realization structure based on varied states. In addition, the present invention provides a novel PN carrier capture methodand a device.

Description

technical field [0001] The present invention relates to digital signal transmission, especially relates to the initial capture process of carrier in the digital TV terrestrial single-carrier broadcasting transmission system. The carrier can be captured reliably and quickly by using the spread spectrum gain of PN sequence in the frame structure. Background technique [0002] In the wireless digital communication system, the carrier recovery module in the receiver is the most basic module. Especially in the digital TV terrestrial transmission system, due to the instability of the carrier frequency of the output intermediate frequency signal of the tuner (tuner) and the possible Doppler frequency difference, the received RF signal will have relatively large Severe carrier deviation. The existence of carrier deviation will cause the phase of the received signal to be ambiguous, and the correct transmitted signal cannot be demodulated, and it will also cause timing synchronizati...

AI Technical Summary

Problems solved by technology

[0008] The disadvantage of the traditional carrier recovery algorithm using pilots is that due to the existence of multipath channels, the wireless signal is subject to frequency selective fading, and the pilots may be faded, so that the input signal-to-noise ratio of the recovery carrier loop is too low, and the The contradiction between the capture range and the locking accuracy of any phase-locked loop is more prominent, and what is worse is that when the pilot frequency is completely eliminated, the phase detection output makes the carrier frequency stable but the residual actual frequency deviation is large, that is, It is the so-called carrier false lock. At this time, the carrier loop system is stable, but the system performance is poor due to the large residual frequency deviation.

Therefore, the algorithm of using the pilot to capture the carrier is greatly affected by the channel, and the contradiction between the locking accuracy and the capture range is more prominent, which will in turn affect the compensation process of the equalizer to the channel

[0017] The disadvantages of the carrier estimation algorithm obtained by using known data or cyclic characteristic data for correlation matching are: because the existence of known data will affect the spectrum efficiency, the proportion of known data is always small, and due to the use of a known The data can only get a valid estimate of the carrier offset once, and the update rate of the estimate or the loop will be very small, which will cause the recovery time of the carrier to be lengthened

In this way, only the carrier deviation is considered at the receiving end, and the two signals are no longer equal, and there is 2πΔfT between them 1 The initial phase deviation, if 2πΔfT 1 ≤2π, the phase can be extracted after the correlation of two pieces of data to get the estimation of Δf, but if 2πΔfT 1 >2π, 2πΔfT cannot be extracted 1 The exact value (2π ambiguity) makes the estimation of Δf wrong

This requires T 1 It should be designed as a smaller value, but this will require known data segments to be inserted more frequently, which will affect the data spectrum efficiency

[0018] To sum up, the carrier acquisition method using the pilot has a fast update rate and will not reduce the spectrum efficiency, but it is greatly affected by the channel, the acquisition accuracy is poor, and there is a carrier false lock; the carrier acquisition algorithm using known data correlation The accuracy can be higher, but the update rate is slow, the carrier capture range is limited, and the spectral efficiency is reduced.

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