Digital intermediate frequency conversion method and system used in repeater

Abstract

The invention discloses a frequency changing method of digital middle-frequency signals used in a repeater station system, which comprises two steps of an up frequency changing process and a down frequency changing process: in the down frequency changing process, the middle-frequency signals after digital analog conversion are processed by digital wave filtering processes such as an extraction process, a bandpass compensation, a signal shaping process, etc. after a digital frequency mixing process, the middle-frequency signals can be moved to a zero middle-frequency, a digital signal with the high speed rate can extracted as two-channel quadrature digital baseband I, Q signal with a low speed rate; in the up frequency changing process, the digital baseband I, Q signals acquired from the down frequency changing process are processed by an interpolation filtering process, then processed by I, Q modulation process and a secondary frequency mixing process, and the signals can be processed by a gain adjustment and control, finally high speed digital middle-frequency signals are outputted. Correspondingly, the invention also discloses a frequency changing system thereof. The invention can be achieved by using PLC units such as FPGA, CPLD, EPLD and DSP, etc., which can improve the integration degree of repeater station equipment; meanwhile, an ASIC chip is removed to decrease heating capacity and to improve the reliability.

Description

【Technical field】 [0001] The invention relates to a digital signal method in mobile communication, in particular to a frequency conversion method and a frequency conversion system for a digital intermediate frequency signal applied in a repeater. 【Background technique】 [0002] At present, in the analog repeaters and carrier pool systems of GSM, CDMA, WCDMA and other communication systems, the intermediate frequency demodulation adopts the method of analog complex demodulation. The basic principle is to use a voltage-controlled oscillator and a phase-locked loop to generate two positive The intersecting intermediate frequency carrier signal, the input intermediate frequency signal is multiplied by the two orthogonal intermediate frequency carrier signals through the analog multiplier to realize the transfer of the input signal in the frequency domain, and then the I and Q two basebands are obtained through the analog low-pass filter Signal, so as to realize the down-conversi...

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Problems solved by technology

However, this solution also has some shortcomings, specifically: the communication between digital chips, timing control and interface control are complicated, which greatly increases the complexity of the monitoring subsystem, and the risk of system unreliability increases; the number of developed carriers is controlled by the chip The number of channels that can be processed is determined by the number of carriers in the system. The system carrier number cannot be expanded at will, and the system scalability is poor; the use of a large number of digital chips increases the difficulty of PCB layout and the complexity of hardware debugging; the power consumption of digital chips is large, resulting in The heat generation of the system is large, and the reliability of the product is poor

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