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Digital predistortion module receiver saves power, simplifies basestation design

Linear Technology has introduced the LTM9003, a wideband RF-to-digital receiver subsystem that includes a high performance 12-bit, 250 Msps analog-to-digital converter (ADC), a bandpass filter, intermediate frequency (IF) amplifier and a high linearity RF downconverting mixer.

The LTM9003 integrated uModule receiver reduces board space and development time for wireless basestations implementing PA linearization with digital predistortion (DPD). The LTM9003 harnesses years of signal chain design experience and offers it in an easy-to-use 11.25 mm x 15 mm uModule package.

DPD addresses the most significant source of power consumption in a basestation: the PA. Powerful digital algorithms correct for nonlinearity in the power amplifier, allowing it to operate at a higher average power level without generating excessive distortion. A single 20 W PA without DPD may run at less than 10 percent efficiency, meaning greater than 200 W of power consumption. Due to the number of power amplifiers in a basestation, the savings are significant to the operating expense (OPEX) of the service provider. Digitizing the fifth or even seventh order harmonics requires a wide bandwidth, low noise receiver with a flat passband. The LTM9003 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 -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 5 clock cycles of latency and the absolute delay through the filter is 2.7 ns.

The LTM9003 is packaged in a space-saving 11.25 mm x 15 mm LGA package, utilizing a multilayer substrate that shields sensitive analog lines from the digital traces to minimize digital feedback. Supply and reference bypass capacitance is placed inside the uModule, tightly coupled to the die, providing a space, cost and performance advantage over traditional packaging. With no external capacitance required, the LTM9003 consumes approximately one-fourth the space of discrete implementations.

Availabilty

The LTM9003 is priced at $45.00 each in 1,000 piece quantities. Demo boards, samples and more information are available.

Datasheet for: LTM9003

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