National Semiconductor Launches Chip Sets for Base Station Receivers
Santa Clara, CA-based National Semiconductor has developed a multi-carrier receiver chipset consisting of the CLC5902 two-channel digital downconverter (DDC) and the CLC5958 14-b, 52 MSamples/s A/D converter. This chipset will allow wireless designers to reduce the cost and size of a base station receiver, while maintaining or improving the quality of service for many systems, including GSM-1800, PCS, wideband CDMA (W-CDMA), wireless local loop (WLL), and smart antenna products.
The CLC5902 is a two-channel digital downconverter with 100 dB dynamic range. It provides programmable digital tuning, filtering, and decimation based on hard-wired digital signal processing (DSP) technology. In addition, the chip outputs digital in-phase/quadrature (I/Q) signals in a range of formats compatible with popular programmable DSP chips.
Each CLC5902 mixes, filters, and processes two of the individual RF channels in the receiver chain prior to the DSP. The receiver can be easily expanded to handle more channels with the addition of more CLC5902s.
The signal is digitized by the CLC5958 A/D. This converter offers a spurious-free dynamic range (SFDR) of 90 dB and a signal-to-noise ratio (SNR) of 71 dB at 20 MHz input frequency. These capabilities give the A/D converter sufficient dynamic range to enable multi-carrier receivers that have large and small signals present at the same time.
The CLC5902 is offered in a 128-lead QFP package and is priced at $22.50 each in quantities of 1,000. The CLC5958 is supplied in a 48-lead chip-scale package (CSP) and is available for at $35 in quantities of 1,000.
Receiver chip set
In a related release, National Semiconductor has announced a chip set that is designed to improve cellular base station receiver performance.
The Diversity receiver chip set is composed of two CLC5526 digital variable gain amplifiers (DVGAs), two CLC5956 12-b/65 MSample/s analog-to-digital (A/D) converters (A/Ds), and the CLC5902 digital downconverter with integrated automatic gain control (AGC). In combination, these devices support two independent channels, performing A/D conversion, digital downconversion, and processing of baseband signals in the digital domain.
The Diversity chip set eliminates the need for multiple stages of analog frequency downconversion hardware, including expensive mixers, filters, and amplifiers, by allowing digitization of the signal at the first IF after it has been mixed and filtered only once. The chip set features a total dynamic range of 120 dBFS, making it a good solution for GSM-900 and GSM-1800 systems. The solution can be used in PCS, AMPS, and Personal HandyPhone System (PHS) applications.
Diversity chip set evaluation boards are available to help facilitate quick bench trials and simplify final system designs. The chip set is priced at $49.80 in 1,000 unit quantities.