Analog Devices (ADI) has extended its portfolio of RF ICs with a family of five pin-compatible quadrature modulators that together cover the 250 MHz to 4 GHz frequency range, enabling wireless system engineers to standardize board designs across multiple operating bands and cellular standards. Each of the five quadrature modulators is optimized for a specific frequency band, reducing the performance degradation that occurs when a single modulator is specified to handle the entire frequency bandwidth.

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The ADL537x family of quadrature modulators can be used as direct-to-RF modulators in digital communication systems, including GSM, CDMA, TDS-CDMA, WCDMA and CDMA2000 base stations and QPSK or QAM broadband wireless access transmitters. With input bandwidth of 700 MHz, the ADL537x family simplifies the design of broadband digital pre-distortion transmitters used for the correction of multicarrier power amplifier distortion products.

To improve system performance and speed time to market, the ADL537x quadrature modulators are designed to seamlessly interface to ADI’s TxDAC+ transmit DACs. The ADL537x family offers high linearity (+ 12 dBm P1dB and +26 dBm IP3 at 2140 MHz) and low noise (–158 dBm/Hz). The family also features a buffered single-ended local oscillator (LO) drive and operates from a singly supply voltage of 4.75 V to 5.5 V.

Designed to convert complex modulation information from the baseband to the final RF output frequency, ADI’s new quadrature modulators generate highly linear modulated RF signals at higher output levels. This eliminates the intermediate frequency stages in the transmit signal chain, improving transmission quality and lowering system cost. To further reduce cost and simplify system design, the devices feature a direct interface to ADI’s TxDAC+ transmit DACs.

In addition to the ADL537x family, ADI is introducing two highly linear, fixed-gain RF amplifiers that integrate input and output matching networks on a single 3 mm × 3 mm chip. Integrating both input and output matches eliminates up to six external components typically required by competing devices. The ADL5322 is tuned to support 700 MHz to 1 GHz operation and the ADL5323 is tuned to support 1.7 GHz to 2.4 GHz.

The 0.5 W (28 dBm at P1 dB) output power pre-drivers provide a highly linear output of 42 dBm IP3 and excellent gain stability of ± 0.25 dB. With a fixed gain of 20 dB, both amplifiers are ideally suited for use at the output of the ADL537x modulator family. Combining the ADL537x with the ADL532x produces a fully characterized, highly linear signal chain with exceptional output power stability reducing the need for gain and power temperature correction circuitry.

The ADL537x quadrature modulators are sampling now, with release scheduled for December 2006. The devices are available in 4 mm × 4 mm lead frame chip scale packages (LFCSP) and are priced at $4.98 per unit in 1000-piece quantities. Evaluation boards combining the quadrature modulators with the TxDAC+ transmit DACs are available. The ADL5322 and ADL5323 pre-drivers are sampling now, with release scheduled for July 2006, and are priced at $3.48 per unit in 1000-piece quantities.