Linear Technology LTC5583 RMS power detector

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Linear Technology has introduced the LTC5583, a 40 MHz to 6 GHz dual channel, matched RMS power detector, offering over 55 dB isolation at 2.14 GHz. In RF power amplifier (PA) applications, the device provides a simple solution for accurately measuring forward power, reverse power and voltage standing wave ratio (VSWR).

The device comprises a pair of 60 dB dynamic range RMS detectors that are matched to 1.25 dB. This provides accurate RF power measurement of high crest-factor signals such as those used in LTE, WiMAX, W-CDMA, TD-SCDMA and CDMA2000 3G or 4G basestations and other high-performance radios employing complex modulation waveforms.

Each channel can detect signals accurately from -58 to 2 dBm, in a log-linear response with a typical linearity of better than ±0.5 dB covering all cellular frequency bands.

At higher frequencies, the device can provide 47 dB of useful dynamic range up to 6 GHz. Unique to it, each detector simultaneously tracks the envelope of the modulated input waveform, providing on-chip capability to measure both peak and average signal power.

The detector has best-in-class channel-to-channel isolation of over 55 dB at 2.14 GHz, when driven differentially. It can operate single-ended for RF input frequencies up to 2.14 GHz, requiring no external balun transformers. This configuration greatly reduces costs without trading off dynamic range and provides isolation better than 40 dB.

An integrated amplifier measures the difference between the two detector outputs. For applications where one RF input is measuring the forward power and the other the reflected power, the difference output provides real-time VSWR results.

The two matched detectors are also useful in applications such as monitoring and controlling RF amplifier stage gain. The matching and isolation performance minimise calibration requirements, thus simplifying designs and reducing costs.