Dual-channel detector stands test of comparison

A novel power detector IC measures two complex input signals simultaneously, enabling basestation system designers to solve one of their biggest challenges - the accurate measurement of RF signals.

Analog Devices has released the industry's first dual-channel radio frequency RMS power detector for precision measurement of transmit and receive signals up to 2.7GHz.

The AD8364 is the industry's only power detector that measures two complex input signals simultaneously, enabling cellular basestation system designers to solve one of their biggest challenges - the accurate measurement of RF signals.

The AD8364 is ideally suited for next-generation cellular infrastructure equipment using complex signals with constantly varying peak-to-average ratios, such as cdma2000, W-CDMA and TD-SCDMA.

Specific applications include PA (power amplifier) control and linearisation, antenna VSWR (voltage standing wave ratio) monitoring, transmitter power control, and automatic gain control circuits.

Better control over the power and gain within a basestation power amplifier allows designers to significantly reduce cost and improve operating efficiency.

"A critical component for maintaining output power efficiency and spectral purity, the AD8364 performs a precise RMS power level measurement for each channel, providing the user with two calibrated linear-in-decibels output voltages", said Jay Cormier, Product Line Director for Advanced Linear Products, Analog Devices.

"The integration of the two channels and an accurate temperature sensor reduces our customers' bill of materials, board area and design time".

"The AD8364 is effectively a complete single-chip measurement subsystem".

The AD8364 is the newest member of Analog Devices' TruPwr family of detectors, which are designed to measure complex waveforms at RF frequencies and deliver an accurately scaled DC voltage that is the RMS equivalent of the input waveform.

Drawing on the functionality of Analog Devices' award-winning AD8362 TruPwr detector - introduced in 2002 - the AD8364 integrates two matched AD8362 channels on a single chip.

Additional enhancements include improved temperature performance and reduced log-conformance ripple within the detector cores.

With two matched detectors, the precise matching of both channels reduces temperature and part-to-part variations in comparison with discrete designs.

The AD8364 provides the following output measurements: two accurately scaled independent outputs for each RF measurement; a difference output measured across the two channel inputs; and a temperature output measured by the on-chip temperature sensor.

The difference output enables users to accurately measure the difference between the two channels that can have varying input frequencies and power levels, thus allowing precise control of gain across RF/IF signal paths.

By adding a temperature sensor to the three TruPwr outputs, the AD8364 allows designers to calibrate temperature drift and/or monitor temperature variations within the system.

When compared with conventional or discrete implementations, the AD8364 offers considerable savings in board area, component count and solution cost, as it combines the functionality of four integrated circuits into one device.

The AD8364 operates on a single 5V supply, is fully specified for operation from -40 to +85C and is packaged in a space-saving 5mm LFCSP (lead frame chip-scale package).

The AD8364 is available in preproduction quantities, with volume production scheduled for March 2005.

The device is priced at $7.85 per unit in 1000-piece quantities.

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