Linear Technology Corp. introduced two new direct conversion quadrature demodulators that promise to simplify radio design for cellular basestations and microwave and satellite links.

The LT5515 and LT5516 direct conversion quadrature demodulators deliver high linearity, providing more flexible system design and wide spur-free dynamic range, the company says. On a single chip, the devices integrate the functionality of a signal splitter, two high linearity down-converting mixers, a precision local oscillator quadrature generator (0 degrees/90 degrees), and 260 MHz bandwidth output buffers with single-pole, low pass filters on each of the outputs.

The LT5515 and LT5516 have applications in cellular infrastructure and in microwave and satellite links, where they directly convert an RF signal to baseband in-phase (I) and quadrature-phase (Q) components. The devices' matched I and Q channels ensure precise gain and phase matching, so that significantly less calibration is required, the company says. The direct conversion receiver ICs also eliminate the need for additional intermediate frequency (IF) stages, local oscillators, and associated filtering.

The devices address two different and adjacent frequency bands. The LT5515 operates over an input frequency range of 1.5 GHz to 2.5 GHz, and the LT5516 operates with RF input from 0.8 GHz to 1.5 GHz. Both devices are designed for high linearity applications, including wireless infrastructure of all types, such as basestations for GSM, CDMA, WCDMA and fixed wireless communications, as well as for satellite and microwave receivers, high-performance radios, and instrumentation.

The high linearity of the LT5515 and LT5516 provides excellent spur-free dynamic range, for example in a RF receiver, even with fixed gain front-end amplification. These direct conversion receivers can eliminate the need for intermediate frequency (IF) signal processing, as well as the corresponding requirements for image filtering and IF filtering. Channel filtering can be performed directly at the outputs of the I and Q channels. These outputs can interface directly to LPFs or to a baseband amplifier.

The LT5515 and LT5516 are offered in 4 mm × 4 mm QFN packages. Pricing starts at $6.75 each for the LT5515 and $7.40 each for the LT5516 in 1,000 piece quantities.
Linear Technology Corp.
www.linear.com