Editing Superheterodyne receiver (section)

===Demodulator===
The received signal is now processed by the [[demodulator]] stage where the audio signal (or other [[baseband]] signal) is recovered and then further amplified. AM demodulation requires [[envelope detector|envelope detection]], which can be achieved by means of [[rectification (electricity)|rectification]] and a [[low-pass filter]] (which can be as simple as an [[RC circuit]]) to remove remnants of the intermediate frequency.<ref name="AMDEM"/> FM signals may be detected using a discriminator, [[Detector (radio)#Ratio detector|ratio detector]], or [[phase-locked loop]]. [[Continuous wave]] and [[single sideband]] signals require a [[product detector]] using a so-called [[beat frequency oscillator]], and there are other techniques used for different types of [[modulation]].<ref name="TSCM"/> The resulting audio signal (for instance) is then amplified and drives a loudspeaker.

When so-called '''high-side injection''' has been used, where the local oscillator is at a ''higher'' frequency than the received signal (as is common), then the frequency spectrum of the original signal will be reversed. This must be taken into account by the demodulator (and in the IF filtering) in the case of certain types of modulation such as [[single sideband]].