Digital predistortion receiver simplifies base station design

Digital predistortion receiver simplifies base station design

The LTM9003 RF-to-digital receiver subsystem with digital predistortion (DPD) includes a 12-bit, 250-Msample/s A/D converter, a bandpass filter, IF amplifier, and an RF downconverting mixer — all in an 11.25 x 15-mm uModule package. The company claims that this integrated receiver significantly reduces board space and development time for wireless base stations implementing PA linearization with DPD. A single PA without DPD may run at less than 10% efficiency, meaning greater than 200 W of power consumption.

The part includes a 125-MHz bandpass filter that exhibits less than 0.5-dB passband ripple across the entire band. The noise floor of the receiver chain from the RF input to the LVDS digital output is just –147.3 dBm/Hz, which is well below that of the PA.

Since DPD is a feedback loop, the receiver (also called a transmit observation path receiver) benefits from low latency; a faster loop leads to better efficiency in the PA and therefore even lower power consumption. The ADC in the LTM9003 has just five clock cycles of latency and the absolute delay through the filter is only 2.7 ns.

Supply and reference bypass capacitance is placed inside the uModule. With no external capacitance required, the LTM9003 consumes approximately one-fourth the space of discrete implementations. ($45 ea/1,000 — available now.)

Linear Technology , Milpitas , CA
Literature 800-4-LINEAR
http://www.linear.com