Square-law detector explained

Square-law detector should not be confused with inverse-square law.

In electronic signal processing, a square law detector is a device that produces an output proportional to the square of some input.^[1] For example, in demodulating radio signals, a semiconductor diode can be used as a square law detector, providing an output current proportional to the square of the amplitude of the input voltage over some range of input amplitudes.^[2] A square law detector provides an output directly proportional to the power of the input electrical signal.

References

1. IEEE Std. 100 Authoritative Dictionary of Standards Terms Seventh Edition, IEEE, 2000,,Square law detection
2. https://archive.org/details/in.ernet.dli.2015.13257/page/n19/mode/2up H. C. Torrey, C. A. Whitmer, Crystal Rectifiers, New York: McGraw-Hill, 1948, pp. 3 - 4