True measurement of RF signal power

A high frequency, wideband RMS power detector from Linear Technology has a high dynamic range. According to the company, the LTC5596 provides accurate, true power measurement of RF and microwave signals independent of modulation and waveforms.

Modern 4G and 5G broadband communications systems employ high order, multi-tone OFDM to support higher data rates. Traditionally, microwave Schottky diodes are used as the detector element in these systems, but have shortcomings when rectifying RF or microwave signals – because the only measure the peak of the waveform, the real power of the signal is misrepresented.

Linear says that, in contrast, RMS detectors perform an analogue root-mean-square computation of the waveform, then average the result to derive a true power representation of the input signal, regardless of its modulation, number of carriers and varying amplitudes.

With an accuracy said to be better than ±1dB over frequencies ranging from 200MHz to 30GHz, the device can also be used from 100MHz to 40GHz, but with slightly reduced accuracy at the frequency extremes.

Its RF input is internally 50Ω matched from 100MHz to 40GHz, making the device very easy to use at any band within its useful frequency range.

The LTC5596 operates from a 3.3V supply, drawing a nominal current of 30mA. With improved ESD protection, all pins are said to be capable of withstanding up to 3500V discharge, human body model. Two temperature grades are available: -40 to 105°C case and -40 to 125°C case. Both versions come in a 2 x 2mm 8lead plastic DFN package.

Graham Pitcher

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