A basic construction of a typical radio system consist of filters, mixers amplifiers and antennas.
Filter: removes all unwanted signals from a Radio frequency signal. It either allows the signal to pass through or blocks the signal based on it frequency configuration.
There are 3 types of RF filters
- Low-pass: a max frequency is set and all signals below that are allowed to pass through
- Bandpass: has a minimum and a maximum threshold range signals that fall within the threshold are allowed through
- And high pass: sets a minimum frequency threshold, all signals above the minimum threshold are allowed to pass through.
Filters are also found in transmitters, where they are used to eliminate unwanted frequencies called harmonic oscillations, which result from the process of modulating the signal before transmission.
Mixers: combine two inputs and create one output. The single output of a mixer is in the range of the highest sum and the lowest difference of the two frequencies. The sum and the difference are know as sidebands of the frequency carrier because the fall above and below the centre frequency of the carrier signal.
Mixers are used to convert an input frequency to a specific desired output frequency.
Amplifier: An amplifier is used to increase amplitude of an RF signal. A Amplifier is the last stage in a radio circuit and its function is to boost the power of the signal received from the last filter stage before it is transmitted.
Antennas: for a RF signals to be transmitted and received, the transmitter or receiver must be connected to an antenna.(refer to blog on Antenna types)
J. L. Olenewa (2014). Guide to Wireless Communications, ( Third Edition). Boston:CENGAGE Learning