Abstract
In general there are two types of receivers:
- Synchronous
- Asynchronous And the thing that differentiates them is whether they rely/contain one or more local oscillators:
Asynchronous receivers dont utilise local oscillators, instead relying on techniques such as envelop detection, which is much cheaper, but means that there’s less accuracy in the receiver, which means that the transmitted wave must use a larger bandwidth, spacing the different frequencies used in transmission further. These can however be used without any prior knowledge of the carrier frequency, making them more versatile
Synchronous Receivers use local oscillators that use wave addition to “select” specific frequencies, that get passed into bandpass filters before getting compared.