What receiver circuit/stage actually produces the intermediate frequency (IF)?

The mixer stage is the component responsible for producing the intermediate frequency (IF) in a receiver circuit. In a typical superheterodyne receiver configuration, the mixer takes the incoming radio frequency (RF) signal and combines it with a signal from a local oscillator. This combination results in the generation of new frequencies, specifically the sum and difference frequencies of the two inputs. The difference frequency, which is typically the lower of the two, is selected as the intermediate frequency.

This IF is valuable because it allows for easier processing and amplification of the signal at a fixed frequency, improving selectivity and sensitivity of the receiver. The use of IF enables effective filtering and amplification techniques that would be more challenging to implement directly at the RF range.

Other components mentioned, such as the detector and intermediate frequency amplifier, serve important roles in the overall receiver but do not generate the IF signal. The detector processes the IF signal to recover the original audio or data signal, while the intermediate frequency amplifier amplifies the IF signal to strengthen it for further processing or output. The coherent oscillator is involved in generating a stable reference frequency for mixing, but it is the mixer that directly produces the IF by creating the necessary frequency transformation.