Receiver subsystem

Linear Technology has introduced the LTM9002, a dual IF/baseband receiver subsystem that includes a dual 14-bit analog-to-digital converter sampling up to 125 MSps, anti-aliasing filters, fixed gain differential ADC drivers and 12-bit, trim digital to analog converters.

The integrated receiver reduces the board space and development time for wireless base stations implementing I/Q receivers, direct conversion receivers or multi-channel configurations including diversity receivers.

The device provides optimal connection between the RF and digital domains and achieves 90 dB isolation at 140 MHz input frequency. The overall gain is typically 26 dB and varies less than 0.1 dB between the two channels. A dual 12-bit auxiliary DAC offers the flexibility to adjust the span and balance the two channels using an SPI-compatible serial port.

The receiver is supplied in an 11.25 x 15 mm LGA package, using a multi-layer substrate that shields sensitive analog lines from the digital traces to minimise digital feedback. Supply and reference bypass capacitance is placed inside the module tightly coupled to the die. With no external capacitance required, it consumes about ¼ the space of the discrete implementation.

Features include: integrated dual 14-bit, high-speed ADCs, passive filter and fixed gain, differential amplifiers; up to 300 MHz IF range - low-pass and band-pass filter versions; integrated low distortion amplifiers - fixed gain: 8, 14, 20 or 26 dB, 50, 200 or 400 Ω input resistance; 66 dB SNR up to 70 MHz input; 76 dB SFDR up to 140 MHz input; auxiliary 12-bit DACs for full-scale adjustment; clock duty cycle stabiliser; single 3 to 3.3 V supply; low power: 1.3 W (665 mW/ch); shutdown and nap modes.