The radiometer is equipped with an on-chip square-law detector and with an input Dicke switch for the receiver calibration.
It consists of a square-law detector preceded by a low-noise amplifier and followed by a low-frequency integrator.
The response to large abrupt increases in input amplitude can be even more striking, however, because the square-law detector characteristic exaggerates the effect of the input increase.
This detector comprises a square-law detector followed by a low pass filter followed by a square-root function.
In common with the square-law detector, the true-RMS detector will make the AGC loop's equilibrium point independent of the RF signal waveform.
Two straightforward detector types can be made, using microwave semiconductor diodes: the linear detector and the square-law detector.
The output of the square-law detector is multiplied by +1 or -1, depending on the position of the Dicke switch, before integration.
Each filter output from each square-law detector
is integrated in time, producing a DC voltage proportional to the integrated power density of the input RF signal over the bandpass of the filter.
This six-port junction linearly combines the two input signals and, because of the square-law detectors
on its four outputs, it delivers four DC voltages.