Quad demodulators

Two direct conversion quadrature demodulators from Linear Technology simplify radio design for mobile base stations and microwave and satellite links.

The devices reduce costs compared with discrete solutions by integrating on a single chip the functionality of a signal splitter, two high linearity down-converting mixers, a precision local oscillator quadrature generator and 260 MHz bandwidth output buffers with single-pole, low pass filters on each of the outputs.

The devices' matched I and Q channels ensure precise gain and phase matching, so that less calibration is required.

These direct conversion receiver ICs eliminate the need for additional intermediate frequency stages, local oscillators and associated filtering.

The LT5515 operates over an input frequency range of 1.5 to 2.5 GHz, and the LT5516 operates with RF input from 0.8 to 1.5 GHz.

Both devices are designed for high linearity applications. These include wireless infrastructure of all types, such as base stations for GSM, CDMA, W-CDMA and fixed wireless communications, as well as for satellite and microwave receivers, high-performance radios, and instrumentation.

Their features include: 1.5-2.5 GHz (LT5515); 800 MHz-1.5 GHz (LT5516); high input IIP3 - >20 dBm; high input IIP2 - >50 dBm; DC-coupled baseband outputs; I/O output gain mismatch - <0.3 dB; I/Q output phase mismatch - typical 1°; LO drive level - 5 dBm; 4.5 to 5.25 V supply range with shutdown mode 2 µa.