摘要：Due to the low dynamic range of the analog front end, low respond speed, bad flatness of the Amplitude-frequency characteristics and the poor noise suppression capability of the signal conditioning in the analog signal chain of the traditional digital down converter (DDC) system, an improved analog signal chain scheme used in high data rate receiver (HDR) of the satellite communication system has been put forward. This scheme has 55dB dynamic range, high respond speed and good noise suppression capability. Moreover, it has been realized on the platform of the ground terminal HDR for demodulator system. 720MHz and 1.2GHz intermediate frequency conversion is an important component of the satellite ground monitoring X-band data channel receiver system. The scheme consists of a band-pass filter module, a digital control variable gain amplifier (VGA), a low noise amplifier (LNA), a radio or intermediate frequency gain block and an ADC which has 1.7GHz input bandwidth. It realizes sampling and conditioning of the 720MHz and 1.2GHz intermediate frequency signal and automatic gain control (AGC). Experimental results show that the scheme has the characteristics: automatic and fast gain control, wide dynamic range and good amplitude-frequency characteristics of the gain points in the pass-band, low power consumption and good noise suppression capability.
关键词：down conversion system;digital down converter;analog signal conditioning;automatic gain control;high speed ADC sampling
