Linear Technology/Analog Devices DC2932A Demonstration Circuit offers a reference design for the LTC5597 RMS Power Detector.
The circuit has an RMS response measuring RF and microwave signals from 100MHz to 70GHz. The input signal changes to a DC voltage that is logarithmically proportional to the input signal level. The power detector can detect signals as low as -37dBm and provides an input dynamic range up to 35dB, delivering 1dB accuracy, depending on frequency.
The PCB layout of the Demonstration Circuit uses the recommended microstrip transmission line structure, plus the recommended endpoint transitions. Input impedance to the detector is internally matched to 50Ohm. The reference design is ideal for RMS measurements of high crest factor waveforms up to 12dB peak/average ratio. No external coupling capacitor is required if the DC voltage at RFIN pin is kept below 1V.