Advanced Designs
To overcome obstacles such as image response, multiple IF stages are used, and in some cases multiple stages with two IFs of different values are used. For example, the front end might be sensitive to 1–30 MHz, the first half of the radio to 5 MHz, and the last half to 50 kHz. Two frequency converters would be used, and the radio would be a double conversion superheterodyne; a common example is a television receiver where the audio information is obtained from a second stage of intermediate-frequency conversion. Receivers which are tunable over a wide bandwidth (e.g. scanners) may use an intermediate frequency higher than the signal to improve image rejection.
Read more about this topic: Superheterodyne Receiver
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