Composition of wireless communication system

Author：admin  Clicks：22  Release time：2025-12-25

A wireless communication system generally consists of a transmitter, a receiver, and antennas (including feeders) connected to them.

Transmitter The main function of the transmitter is to first modulate the carrier signal with the signal to be transmitted, forming a modulated carrier. The modulated carrier signal is converted to a radio frequency (RF) carrier signal through frequency conversion (some transmitters do not go through this step) and sent to a power amplifier. After being amplified by the power amplifier, it is sent to the antenna (feeder). A block diagram of a shortwave transmitter is shown in Figure 1-3.

Antenna The antenna is an important part of the wireless communication system. Its main function is to convert RF carrier signals into electromagnetic waves or convert electromagnetic waves into RF carrier signals. According to the normative definition, "an antenna is a transmission mode converter that transforms guided-mode RF current into diffused-mode spatial electromagnetic waves, and vice versa." The main function of the feeder is to efficiently send the RF carrier signal output by the transmitter to the antenna. This requires the feeder to have low attenuation, and its impedance should match the output impedance of the transmitter and the input impedance of the antenna as much as possible.

Receiver The main function of the receiver is to first amplify the RF carrier signal received by the antenna with a low-noise amplifier, and then restore the original signal after frequency conversion (single, double, or even triple frequency conversion), intermediate frequency amplification, and demodulation. Finally, it is amplified by a low-frequency amplifier and output. A block diagram of a shortwave receiver is shown in Figure 1-4.

It should be noted that most practical wireless communication systems currently use duplex mode. Therefore, each communicating party has a transmitter, a receiver, and antennas (and feeders) connected to them. Moreover, the transceivers are integrated together (and equipped with a duplexer).