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RF power detector operates over wide frequency range

Posted: 22 May 2008 ?? ?Print Version ?Bookmark and Share

Keywords:power detectors? WiMAX? femtocells?

A new monolithic broadband, high performance logarithmic RF power detector from Linear Technology Corp. promises accurate RF power measurement over a wide frequency range covering the 800-900MHz and 1.7-2.2GHz cellular bands, as well as the 2.6GHz and 3.5GHz WiMAX bands.

The LT5538 RF power detector provides a DC output voltage that is log-linearly proportional to its input power level. Within its measurement dynamic range, the detector exhibits best-in-class accuracy and linearity of 0.8dB over its rated operating temperature range of -40C to 85C.

Moreover, the LT5538 has outstanding sensitivity, capable of detecting signals as small as -75dBm to as large as +10dBm at 2.14GHz. The device operates with a single-ended RF input. It requires no external RF transformer, thus simplifying design while reducing costs.

The LT5538's dynamic range performance is suitable for RF power amplifier power control and monitoring for a wide range of wireless systems, as well as receiver Automatic Gain Control (AGC) and Receive Signal Strength Indicator (RSSI) functions. These are required functions for cellular base stations of all types, including large cells, microcells, picocells and femtocells, wireless repeaters, WiMAX base stations, broadband wireless access points, broadband cable networks, military and commercial long-range radios, as well as test and measurement instrumentation. The LT5538's accuracy performance helps to minimize equipment calibration requirements, resulting in stable system performance and reduced operating costs.

The LT5538 uses Linear Tech's high-speed bipolar process, enabling wide bandwidth and dynamic range performance. The fast output response of 100ns rise time and 200ns fall time to rapidly changing RF input signal levels make it suitable for rapid measurement of RF signal power in Time Division Duplexing (TDD) switching wireless operating environments, including WiMAX, TD-SCDMA and other applications.

The LT5538 operates over a wide supply voltage range of 3V to 5.25V, drawing a low quiescent supply current of 29mA compared to other similar class detectors. A shutdown feature is provided. When the chip is disabled with a logic LOW applied to its ENABLE input pin, the chip draws a typical shutdown current of 1?A and a maximum of 100?A.

The device comes in a tiny 8-lead, 3mm x 3mm DFN surface mount package. Pricing starts at $4.50 each in 1,000-piece quantities. The LT5538 is available immediately from stock.

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