AN3062| Application Note
Maxim > App Notes > BASESTATIONS / WIRELESS INFRASTRUCTURE WIRELESS, RF, AND CABLE
HIGH-SPEED SIGNAL PROCESSING
Keywords: high-speed ADC, high-speed analog-to-digital converter, high dynamic performance, RF receiver, Rx, transmitter, Tx, base station systems, BTS, AMPS, CDMA, WCDMA, mixer, IF, dynamic range, AGC, VGA, RF, baseband, signal-to-noise ratio, SNR, blocker, c
Feb 23, 2004
APPLICATION NOTE 3062
Dynamic Performance Requirements for High-Performance ADCs and RF Components in Digital Receiver Applications
Abstract: Today's basestation systems (BTS) have to meet a variety of different standards and must fulfill critical specifications in various blocks of the signal chain. The following paper identifies these demands in signal chain components such as high dynamic performance ADCs, variable gain amplifiers, mixers and local oscillators and details their use in a typical BTS application and how they meet the stringent requirements for high dynamic performance, high intercept performance and low noise. Demanding requirements are placed on high-performance analog-to-digital converters (ADCs) and analog components in most digital receivers. In cellular base station digital receivers for example, sufficient dynamic range is needed to handle high-level interferers (or blockers) while properly demodulating the lower level desired signal. Maxim's MAX1418 15-bit 65Msps or MAX1211 12-bit 65Msps ADC, in combination with the MAX9993 2GHz or MAX9982 900MHz integrated mixers, provide exceptional dynamic range for two of the
most critical stages in a receiver line-up. In addition, Maxim's MAX2027 and the MAX2055 IF digital variable gain amplifiers (DVGAs) provide exceptionally high third order output intercept performance (OIP3) with the required gain adjustment range for many applications. A cellular base station (BTS: Base Transceiver Station) consists of many different hardware modules including one that performs the RF receiver (Rx) and transmitter (Tx) functionality - namely a transceiver (TRx). In the older analog AMPS and TACS BTSs, one transceiver handles a duplexed Rx and Tx RF carrier. Many transceivers are needed to provide enough carriers to obtain the required calling coverage. Analog technology is being replaced by CDMA and WCDMA worldwide, and Europe adapted GSM over a decade ago. In CDMA, many callers utilize the same RF frequency, which allows a single transceiver to handle many callers' signals simultaneously. Various CDMA and GSM designs exist today and methods to reduce cost and power are continuously being
sought by BTS manufacturers. Optimizing single-carrier solutions or developing multi-carrier receivers can accomplish this. Figure 1 illustrates the main blocks in a subsampling receiver architecture commonly used in BTS equipment.
Figure 1. Subsampling receiver architecture.
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