Carrier frequency recovery and tracking method
A technology of carrier frequency and recovery method, applied in multi-carrier systems, multi-frequency code systems, high-definition television systems, etc., can solve the problems of high overall complexity, meet system performance, reduce hardware costs, and avoid complexity Effect
Active Publication Date: 2011-08-31
MAXSCEND MICROELECTRONICS CO LTD
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[0005] In the commonly used carrier frequency recovery method, the tan is usually used to find -1 Function method to get the frequency error value, that is, to find tan for the phase angle of C -1 , Im(C) and Re(C) respectively represent the imaginary part and real part of C. This method is relatively straightforward, but it needs to be looked up in the hardware implementation, or replaced by other approximate functions, and the overall complexity is high.
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[0023] The carrier recovery of the present invention, that is, the method for correcting the initial carrier frequency also utilizes the characteristics of the CP, and first performs a correlation operation to obtain the vector C, but does not seek tan -1 , but the imaginary part symbol value of the vector C is extracted, because the imaginary part symbol reflects the direction of the current frequency offset, that is, the positive and negative of Δf, knowing the direction of the frequency offset, you can control the NCO (Numerical Controlled Oscillator) The frequency is adjusted in the opposite direction. On the adjusted step size, when the sign of the imaginary part changes, the approach of halving each time from large to small is adopted. In this way, after several symbol adjustments, the final adjustment step size is reduced to a certain range, and it can be considered that the initial carrier frequency correction is completed.
[0024] Such as image 3 As shown, for the...
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The invention discloses a method for recovering and tracking carrier frequency. The recovery of the carrier frequency firstly carries out related calculation to get a vector C, extracts the imaginary part symbol value of the vector C, and controls NCO frequency to adjust frequency offset towards opposite direction. When the imaginary part symbol changes, the adjusting step halves from big to small each time. After multiple symbol adjustments, the final adjusting step reduces to a fixed scope, thus an initial carrier frequency correcting is finished. The carrier frequency tracking: setting a threshold th, finding 128 points satisfying condition |I|+|Q|>th, if there is not enough points satisfying the condition, the tracking adjustment is not carried out; getting an accumulated value ft=sigma128(QSI-ISQ) for the found points; delivering the sign bit h of the accumulated value to a frequency adjusting module. The invention is easy to control, and the cost of the hardware is low. The invention is suitable for but not limited to T-DMB standard digital television broadcast receiving system.
Description
technical field [0001] The invention relates to a carrier frequency recovery and tracking method in a T-DMB (Terrestrial Digital Multimedia Broadcasting, terrestrial digital multimedia broadcasting) standard digital television broadcast receiving system. Background technique [0002] In the process of wireless communication, due to the error between the oscillator frequency of the transmitting end and the receiving end itself, as well as the Doppler effect caused by the relative motion of the transmitting end and the receiving end, the carrier frequency error will occur at both ends of the transmitting and receiving ends. For multi-carrier systems, such as OFDM (Orthogonal Frequency Division Multiplexing, Orthogonal Frequency Division Multiplexing) systems, the impact caused by carrier frequency errors is particularly serious, because the carriers of each sub-channel in a multi-carrier system are orthogonal to each other, once the frequency The offset will destroy this ortho...
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IPC IPC(8): H04L27/38H04L27/26H04N7/015
Inventor 蒋朱成吴涛张卓鹏
Owner MAXSCEND MICROELECTRONICS CO LTD