【摘要】 在射频接收系统中,可变增益控制电路能够有效地改善接收机的动态范围。设计了一种基于ADL5330芯片下的多模式可变增益控制电路,采用"VGA芯片+耦合器+窄带滤波+检波器"的负反馈方式实现自动增益控制功能,采用"DA芯片+继电器+VGA芯片"的方式实现手动增益控制电路。经过实际测试,该电路在AGC模式下实现了60 dB且精度保证在0.2 dB以内的大动态范围;在MGC模式下,利用单片机的D/A功能发出相应大小的电压,从而控制ADL5330(VGA芯片)产生的相应增益,其增益控制精度可达到0.3 dB;并对两种模式下公共的压控增益传输线进行隔离保护,保证二种模式下的电压不会相互干扰。由此可见,该电路结构既保证了两种模式的高性能运行又防止了两种模式下的相互干扰。更多还原

【Abstract】 In the RF receiving system, variable gain control circuit can effectively improve the dynamic range of the receiver. In this paper, a multi-mode variable gain control circuit based on ADL5330 chip is designed. The automatic gain control function is realized by negative feedback mode of "VGA chip + coupler + narrowband filter + detector", and the manual gain control circuit is realized by means of "DA chip + relay + VGA chip". Through the practical test, in the AGC mode of this circuit, the large dynamic range of 60 dB with precision of 0.2 dB can be achieved. And in the MGC mode of this circuit, the gain control accuracy of 0.3 dB can be realized. And the common control gain voltage lines in the two modes are isolated to keep the voltages in the two modes from interference with each other. It shows that the structure of the circuit can not only ensure two modes of high performance operation but also prevent interference between the two modes.更多还原