Introduction and Application of Antenna Feeder Tester

1. What is an Antenna Feeder?

1.1 What is an Antenna?

An antenna is a converter that converts guided waves propagating on a transmission line into electromagnetic waves propagating in an unbounded medium (usually free space), or vice versa. A component used in radio equipment to transmit or receive electromagnetic waves. Engineering systems such as radio communications, radio, television, radar, navigation, electronic countermeasures, remote sensing, radio astronomy, etc., all use electromagnetic waves to transmit information, all rely on antennas to work. In addition, in transmitting energy using electromagnetic waves, antennas are also required for non-signal energy radiation. Generally, antennas are reversible, that is, the same antenna can be used as both a transmitting antenna and a receiving antenna. The basic characteristic parameters of the same antenna for transmitting or receiving are the same. This is the reciprocity theorem of antennas.

1.2 What is a Feeder?

Feeders, also known as cables, play a role in transmitting signals in many fields including cable TV systems. Through them, the signals received by the antenna are transmitted to the front-end system. The signals output by the front-end are also transmitted to each user's TV by cables. machine. Therefore, the quality and model of the feeder are important factors that directly affect the reception effect and signal transmission quality of the cable TV system.

The feeder is a signal line that connects early TV sets to outdoor antennas. It is usually flat in shape and has a double line. The line body is made of insulating plastic. There is no shielding layer on the outside. Its anti-interference ability is extremely poor. When used outdoors, its performance will be affected by rainy weather. Nowadays, due to the popularity of cable TV, TV signal lines are completely replaced by coaxial cables.

The feeder includes the lower lead of the antenna and the main line, branch line, branch line, subscriber line, etc. of the system. There are three main types of feeders used in cable television systems: flat feeders, coaxial cables and optical cables. The most widely used cable is coaxial cable.

Its main task is to effectively transmit signal energy, transmit the signal power emitted by the transmitter to the input end of the transmitting antenna with minimum loss, or transmit the signal received by the antenna to the input end of the receiver with minimum loss, while itself No stray interference signals are generated, so the transmission line must be shielded. When the physical length of the feeder is equal to or greater than the wavelength of the transmitted signal, the transmission line is also called a long line.

1.3 What is an Antenna Feeder?

The antenna feeder refers to the antenna plus feeder.

The antenna feeder system is one of the important components of microwave relay communications. The antenna plays the role of converting electromagnetic waves transmitted in the feeder into electromagnetic waves propagating in free space, or converting electromagnetic waves propagating in free space into electromagnetic waves transmitted in the feeder. The feeder is the transmission channel for electromagnetic waves. In the microwave relay communication circuit of a multi-channel shared antenna feeder system, the technical performance and quality indicators of the antenna feeder system directly affect the communication quality of each microwave channel of the shared antenna feeder system.

2. What will affect the quality of the antenna and feeder system?

2.1 Cable failure

Cable breakage, bending, broken skin, water seepage, etc.

2.2 Connector failure

Corrosion, poor connection of intermediate conductor, etc.

2.3 Antenna failure

Deviation from design specifications

Damage caused by shipping or severe weather

2.4 Transmission line and installation factors

Certain transmission line characteristics may cause amplitude loss changes in RF or microwave signals, some due to poor construction or installation.

3. What is an Antenna Feeder Tester?

Antenna and feeder tester: A special instrument for testing the standing wave ratio and matching of base station antennas and feeders. It is also called a standing wave ratio tester.

The main function:

Standing wave ratio test;

Fault location;

Cable loss test;

RF power test


The antenna and feeder tester can test the standing wave ratio and matching of base station antennas and feeders, as well as cable loss and long-distance fault location. It can quickly evaluate the status of transmission lines and antenna systems, and speed up the installation and commissioning time required for new base stations.

4. Two major factors affecting the antenna feeder system: standing wave ratio and return loss

4.1 What is standing wave ratio?

The full name of standing wave ratio is voltage standing wave ratio, also known as VSWR and SWR, which is the abbreviation of English Voltage Standing Wave Ratio. It refers to the ratio of the antinode voltage and the trough voltage amplitude of the transmission line, also known as the standing wave coefficient and standing wave ratio. When the standing wave ratio is equal to 1, it means that the impedances of the feeder and the antenna are completely matched. At this time, all high-frequency energy is radiated by the antenna, and there is no energy reflection loss; when the standing wave ratio is infinite, it means total reflection, and no energy is radiated at all.

The standing wave ratio is a numerical value used to indicate whether the antenna and the radio wave transmitting station match. If the value of SWR is equal to 1, it means that the radio waves transmitted to the antenna are transmitted without any reflection, which is the most ideal situation. If the SWR value is greater than 1, it means that part of the radio wave is reflected back and eventually turns into heat, causing the feeder to heat up. The reflected radio waves can also produce a very high voltage at the output port of the transmitter, which may damage the transmitter.

4.2 What is return loss?

Return loss: A parameter indicating the signal reflection performance. Return loss describes the portion of the incident power that is reflected back to the source. For example, if 1mW (0dBm) power is injected into the amplifier and 10% is reflected (bounced) back, the return loss is 10dB.

Return loss, looking at the name, is easily misunderstood as the loss caused by the echo. In fact, it refers to the loss of the echo itself (the loss caused by the echo is called reflection loss, and the smaller the value, the better). The more the echo is lost, the smaller the echo will be. When the return loss is infinite, the echo is completely lost, there is no echo, and the system is well impedance matched. So the bigger the return loss, the better.

5. Testing method of Antenna Feeder

To test the antenna feeder, first determine the frequency band of the antenna feeder under test, and select and set the corresponding frequency band in the instrument. Then perform calibration for this frequency band. After calibration is completed, the antenna feeder under test can be tested, including matching test (return loss) and fault location.

TFN has different kinds of Antanna Feeder Tester and can provide you different solutions. If you are interested in our Antenna Feeder Tester, please contact: 

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WhatsApp: +86-18765219251

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