Radio frequency receivers are electronic devices that use antennas to receive signals and then use a tuning device to select a particular signal. The signal is then sent through demodulators to decode and separate the signal into various formats such as video, data and audio. Radio and radio receivers are generally used specifically for receivers which output consists only of sound. However, various other kinds of receivers such as television receivers are also technically radio receivers.
Localized interference and noise are limited by radio techniques. With direct sequence spread spectrum, the signals are spread out over a large band by multiplexing the signal with a code or signature that modulates each bit. With frequency hopping spread spectrum, signals pass through a narrow set of channels in a sequential, cyclical, and predetermined pattern.
When you are selecting an RF receiver it helps if you have an understanding of modulation methods such as AM and FM. There are several types of RF receivers including: amplitude modulated (AM), frequency modulated (FM), ON/OFF key (OOK), amplitude shift key (ASK), frequency shift key (FSK), and phase shift key (PSK). In AM, the amplitude or the height of the signal is varied, while in FM, the instantaneous frequency of the wave is made to shift from the center frequency. On-off key (OOK) is the most basic type of modulation as it just consists of turning the signal on or off. An amplitude shift key (ASK) transmits the data by varying the amplitude of the transmitted signal. A frequency shift key (FSK) is a digital modulation scheme that uses two or more output frequencies. A phase shift key (PSK) is a digital modulation scheme where the phase of a transmitted signal is varied in accordance with the baseband data signal.
When you are searching for an RF receiver that are a few things you should take into consideration including:
- Sensitivity: this is the smallest signal that can be used to produce an output
- Interface: the devices used to connect the output to computers
- Digital sampling rate: this is the rate used to obtain sample signals to represent a digital signal
- Operating frequency: this is the range of signal frequencies that are received or sent
- Resolution, which is the smallest unit that can be resolved
- Direct Sequence Spread Spectrum
- Frequency Hopping Spread Spectrum that are radio techniques used to reduce local disturbances and noise