Spectrum is precious and limited. Most networks divide it up into channels and then portion it out to subscribers. The PVG 310 single-chip modem from Provigent, Inc. (Los Altos, CA) offers a more efficient alternative for designers and operators of point-to-point wireless links by allowing them to prioritize and optimize their links according to traffic and link conditions. The chip's Provi-BandTM technology is based on an adaptive code and modulation mechanism that dynamically adjusts links capacity according to link conditions.

The PVG 310 integrates all of the physicallayer (PHY) baseband functionality needed for broadband wireless systems, including a high-performance modulator, demodulator, forward-error correction (FEC), adaptive equalization, concatenated coding, inphase/quadrature (I/Q) imbalance correction, and distortion compensation. The IC's cross-polarization-interfacecancellation (XPIC) technology allows two data streams on two polarizations of a single channel to be transmitted simultaneously, doubling the net channel capacity. The PVG 310 enables transmission rates of 311 Mb/s (OC-6/STM-2) over 28-MHz (STM-1 doubled) channels and as much as 622 Mb/s over 50-to-56-MHz (STM-4) channels.

All modem parameters are programmable, including bandwidth, data rates, and modulation format. It works with full-or half-duplex operation, supporting time-division-duplex (TDD) and frequency-division-duplex (FDD) systems. The PVG 310 provides quadrature phase-shift keying (QPSK) and 16-, 32-, 64-, 128-, and 256-state quadrature amplitude modulation (QAM) in FDD mode. It supports QPSK as well as 16- and 64-state QAM in TDD mode. It offers symbol rates to 47.5 Mbaud in FDD mode and 25 Mbaud in TDD mode, with intermediate-frequency (IF) and baseband sampling modes.

In a typical point-to-point application (see figure), the PVG 310 can perform transmit and receive digital frequency correction. It allows a system designer to add transmitter predistortion to optimize transmit amplifier performance and reduce operating costs. The configurable baud rate allows a single transceiver design to support a family of microwave radios, while the flexible equalization capabilities help minimize RF filter requirements and minimize the effects of multipath on point-to-point link performance.

Provigent, Inc., 171 Main St., No. 258, Los Altos, CA 94022-2912; (650) 962-0183, FAX: (650) 745-7100, e-mail: info@ provigent.com, Internet: www.provigent.com.