XR-2120

XR-2120 PSK Modem Filter GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM The X R-2120 is a self-contained bandpass fi Iter set designed for realization of Bell 212A compatible 1200 bits/sec PSK modems. The XR-2120 utilizes CMOS technology and switched capacitor circuit techniques to minimize external components to a single crystal or frequency source. Contained in the device are two complete bandpass filters centered around the Bell standard 1200 Hz and 2400 Hz send and receive frequencies. These filters also provide compromise line equalization. Additional features included are digitally programmable transmit and receive gains as well as input anti-aliasing and complete output smoothing filters. Separate VSS pins for transmit, receive, and digital sections are provided to minimize crosstalk. The XR-2120 features guaranteed filter group delay specifications, within ±1001lS of nominal. The XR-2120C is a relaxed version of the X R-2120 with group delay specified within ±15QIlS. The de...