Intermediate frequency in the context of RF front end

A low-noise block downconverter (LNB) is the receiving device mounted on satellite dishes used for satellite TV reception, which collects the radio waves from the dish and converts them to a signal which is sent through a cable to the receiver inside the building. Also called a low-noise block, low-noise converter (LNC), or even low-noise downconverter (LND), the device is sometimes inaccurately called a low-noise amplifier (LNA).

The LNB is a combination of low-noise amplifier, frequency mixer, local oscillator and intermediate frequency (IF) amplifier. It serves as the RF front end of the satellite receiver, receiving the microwave signal from the satellite collected by the dish, amplifying it, and downconverting the block of frequencies to a lower block of intermediate frequencies (IF). This downconversion allows the signal to be carried to the indoor satellite TV receiver using relatively cheap coaxial cable; if the signal remained at its original microwave frequency it would require an expensive and impractical waveguide line.

A superheterodyne receiver, often shortened to superhet, is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original carrier frequency. Edwin Howard Armstrong developed the concept, though Lucien Lévy, Walter Schottky, Henry Round, and John Renshaw Carson worked along the same lines. Superheterodyne receiver systems are still a modern feature, and can be used for other modes than AM.

According to Nahin, "Any receiver that shifts the antenna signal frequencies to new locations in the spectrum is a heterodyne receiver." The prefix super is reserved for those receivers that include a tunable antenna filter for image rejection, and intermediate frequency amplification that suppresses adjacent channels. "This sort of receiver circuitry results in an easy-to-use radio that has reliably consistent tuning with a clearly audible audio output. It is the gold standard of modern AM broadcast radio."

In electronics, a mixer or frequency mixer is a circuit that outputs signals with new frequencies from two signals input to it. In its most common application, two signals are input and two signals are output, having frequencies equal to the sum and the difference of the original frequencies. Other frequency components may also be produced in a practical frequency mixer.

Mixers are widely used to shift signals from one frequency range to another, a process known as heterodyning, for convenience in transmission or further signal processing. For example, a key component of a superheterodyne receiver is a mixer used to move received signals to a common intermediate frequency. Frequency mixers are also used to modulate a carrier signal in radio transmitters.