基于FPGA的恒包络波形数字AGC算法

Research and Implementation of Digital AGC Algorithm for Constant Envelope Waveform Based on FPGA

在现代通信中,通信距离变化较大,接收电台需实时根据天线场强做自动增益控制(Automatic Gain Control,AGC)。基于连续相位调制(Continuous Phase Modulation,CPM)调制和频率调制(Frequency Modulation,FM)等恒包络波形提出新型数字AGC算法。相比传统的数字AGC,新算法不依赖波形结构不用AGC起始计时,具有较强的算法通用性。新算法基本计算单元为有限长单位冲激响应(Finite Impulse Response,FIR)滤波器输出的采样点,对于存在多级FIR滤波器波形,可放在任意一级FIR滤波器处,应用简便。通过实验测试,新算法可将采用AD9434的中频板动态范围拓展到98 dB,较好地解决了电台全幅值段稳定接收问题。

In modern communication, the communication distance varies greatly, and the receiving station needs to make AGC(Automatic Gain Control) according to the antenna field strength in real time. Based on constant envelope waveforms such as CPM(Continuous Phase Modulation) modulation and FM(Frequency Modulation) modulation, a novel digital AGC algorithm is proposed. Compared with traditional digital AGC,the proposed algorithm does not rely on the waveform structure and does not use the AGC start timing, and has a strong algorithm versatility. The basic calculation unit of this algorithm is the output sampling point of the FIR(Finite Impulse Response) filter, and the waveform of the multi-stage FIR filter can be placed at any stage of the FIR filter, which is easy to apply. The experimental tests indicate that the proposed algorithm can expand the dynamic range of the IF board using AD9434 to 98 dB, which better solves the problem of stable reception in the full-amplitude range of the radio station.