CLC5902

The CLC5902 Dual Digital Tuner/AGC IC is a two channel digital downconverter (DDC) with integrated automatic gain control (AGC). The CLC5902 is a key component in the Diversity Receiver Chipset (DRCS) which includes one CLC5902 Dual Digital Tuner/AGC, two CLC5956 12-bit analog-to-digital converters (ADCs), and two CLC5526 digitally controlled variable gain amplifiers (DVGAs). A block diagram for a Diversity Receiver Chipset based narrowband communications system is shown in Figure 1. This system allows direct IF sampling of signals up to 300MHz for enhanced receiver performance and reduced system costs.

The CLC5902 offers high dynamic range digital tuning and filtering based on hard-wired digital signal processing (DSP) technology. Each channel has independent tuning, phase offset, and gain settings. Channel filtering is performed by a series of three filters. The first is a 4-stage Cascaded Integrator Comb (CIC) filter with a programmable decimation ratio from 8 to 2048. Next there are two symmetric FIR filters, a 21-tap and a 63-tap, both with programmable coefficients. The first FIR filter decimates the data by 2, the second FIR decimates by either 2 or 4. Channel filter bandwidth at 52MSPS ranges from ±650kHz down to ±1.3kHz.

The CLC5902's AGC controller monitors the ADC output and controls the ADC input signal level by adjusting the DVGA setting. AGC threshold, deadband+hysteresis, and the loop time constant are user defined. Total dynamic range of greater than 120dB fullscale signal to noise can be achieved with the Diversity Receiver Chipset.