Microwave Journal

70 GHz Linear-in-dB RMS Power Detector

October 14, 2020
Figure 1

The LTC®5597 is a high accuracy RMS power detector that provides a very wide RF input bandwidth, from 100 MHz up to 70 GHz. This makes the device suitable for a wide range of RF and microwave applications, such as point-to-point microwave links, SATCOM, instrumentation, military radio, Wi-Fi, LTE/5G and power control applications.

The DC output voltage of the detector is an accurate representation of the average signal power applied to the RF input, independent of input waveforms with different crest factors such as CW, WCDMA and OFDM (LTE and Wi-Fi) signals. The response is linear-in-dB with 28.5 mV/dB logarithmic slope over a 35 dB dynamic range with typically better than ±1 dB accuracy.

The LTC5597 can measure signals down to -37 dBm, about 10 dB better than any Schottky device which can save the expense of an amplifier in the signal path. It has ±2 dB flat frequency response up to 60 GHz, enables accurate measurement of very broadband signals and minimizes need for calibration (single frequency may be sufficient). The LTC5597 evaluation board uses a 5 mils thick layer of Rogers RO3003 material for the top substrate to achieve low dielectric losses up to 7 GHz.

The detector is well suited for measurement of waveforms with crest factor as high as 12 dB and waveforms that exhibit a significant variation of the crest factor during measurement. To achieve higher accuracy and lower output ripple, the averaging bandwidth can be externally adjusted by a capacitor connected between the FLTR and OUT pins. The enable interface switches the device between active measurement mode and a low power shutdown mode.

The LTC5597 is a unique RMS detector operating above 40 GHz, enabling accurate power measurement in Q- and V-Band SATCOM, point-to-point links and a range of instrumentation and ATE equipment. It is a much more compact, higher performance solution than alternative discretely built and tuned Schottky detectors and other competing solutions.

Analog Devices
Norwood, Mass.