In telecommunications and electronics a transmitter is a small electronic device that generates radio signals by having an antenna connected to it. The transmitter emits a radio wave alternating current, this is then picked up by an instrument in a transmitting station. These transmitters are often called an RF transmitter for short. To receive the signal, a device called the receivers, or simply antenna is required.
In general, these small transmitters are used as a type of sentry, or a sensor. When a transmitter locates itself within a receiving area, it will send a signal back and forth. Most commonly, these devices are used as part of a process instrumentation transmitter. These processes include things like radar, microwave, laser and even cordless phones.
In the case of wireless communications, these small transmitters are also known as wireless handsets. Typically, the transmitter will send a radio wave out and an antenna will pick up and convert it into a usable signal for a particular network. In many cases, it will be up to the users (owners) of the networked devices to pick up the signals and use them. The transmission of radio waves is known as RF technology. There are a number of ways these wireless devices can be operated; they can be operated by one unit as a stand alone piece, or they can be run by a series of units that communicate with each other.
For some systems, multiple transmitters are involved. Usually, the system consists of a transmitter, and then a few receivers. The more transmitters there are, the stronger the signal that are generated, and the longer the distance that the signal travels. The most commonly implemented system would have a transmitter and two or three receivers. In this way, the signal could be exponentially stronger than a single unit transmitting in the form of a circuit.
On the other hand, when using a conventional wired system, the transmitter will receive a radio signal from some sort of antenna and then send it out along a wire. Once the radio wave reaches its destination, any number of different elements can pick up and alter the signal that is being transmitted. One popular type of transmitter is the combined transmitter/receiver. This transmitter/receiver combination is made up of a transmitter that sends a lower frequency radio wave that is combined with a lower powered receiving unit. In addition, most combined transmitters are able to operate on the same carrier wave. This allows for a much larger number of discrete components to participate in the actual transmission process.
Once a transmitter/receiver combination is constructed, the process of modifying signals can begin. The basic modulation schemes that can be used include: QAM, Fast Fourier Transmitment, and Simplex. Some devices also utilize a wide variety of other methods including: QoS (Quality of Service), EoE (effects of errors), PCM (plastic carrier receiver), PCF (phase noise distortion) and RF-IR (remote access). The modulation scheme that a device utilizes is typically chosen depending on the amount of available space and the amount of time that the system can be utilized.
An analog transmitter is often preferred over a digital device for several reasons. First, analog waves are much less likely to become interference than are digital ones. Second, certain analog signal types will not have the phase distortion which is often associated with other signal types. Also, an analog transmitter has the ability to retain the carrier and phase noise of low frequency electrical signals for a longer period of time than can be achieved with a digital transmitter. Lastly, digital waves are more susceptible to external radio transmitter signal interferences, making them less efficient and useful as a means of broadcasting audio and light data.
To receive digital data with an analog transmitter, an analog signal is sent into the transmitter, which then receives the signal. With the use of a digital transmitter the transmitter merely converts the frequency modulation signal to an electrical signal, which can be amplified into audio or light pulses depending upon the needs of the particular situation. Most analog devices utilize a base station, which allows for multiple satellites to link together for broadcasting purposes. The base station sends the signal down through a series of antennae until it reaches a receiver, where it is converted back into a frequency modulation signal.
