Detailed analysis of the 8 core parameters of antennas

2021-11-26 www.whwireless.com

Estimated 6 minutes to finish reading

Antennas have always been the key focus of attention in the field of connectivity products, we have previously carried out a preliminary introduction and analysis according to the type of antenna, but in this large segment of the antenna, it is necessary to know further its key parameters in order to understand more deeply the advantages and use of each type of antenna. The following parameters are divided into two main parts: radiation parameters and circuit parameters, which we will analyse precisely and quickly introduce the meaning of them.

Front-to-back ratio

The antenna's front-to-back ratio is the ratio of the power flux density in the maximum radiation direction of the main flap (specified as 0°) to the maximum power flux density near the opposite direction (specified as within 180°±30°) F/B=10log(front-to-back power/backward power).

Electric down tilt angle

The electric down tilt angle is the maximum radiation pointing on the vertical radiation surface of the communication antenna and the angle of the antenna normal.

Communication antenna is divided into fixed down tilt antenna and electric tilt antenna according to whether it supports electric down tilt adjustment: fixed down tilt antenna refers to the fixed down tilt antenna generated by the amplitude and phase assignment of the antenna radiation unit array according to the wireless coveragedemand; and electric tilt antenna refers to the phase difference of different radiation units in the array through phase shifting unit to produce different radiation main flap down tilt state, usually the down tilt state of electric tilt antenna Only within a certain adjustable angle range.

Wave speed width

In the direction of the diagram usually have two flaps or more flaps, which is the largest flap called the main flap, the rest of the flap called the secondary flap. The angle between the two half-power points of the main flap is defined as the width of the flap of the antenna directional diagram. Called half power (angle) flap width. The narrower the main flap flap width, the better the direction, the stronger the anti-interference ability. Generally speaking, the narrower the main flap beam width of the antenna, the higher the antenna gain.

Antenna gain

Gain and antenna size and beam width of the relationship.

The flatter the "tyre", the more concentrated the signal, the higher the gain, the larger the antenna size, the narrower the beamwidth.

→ 3 important points to pay attention to in particular

1. Antennas are passive devices and do not generate energy. Antenna gain is only the ability to focus energy effectively in a particular direction to radiate or receive electromagnetic waves.

2, the gain of the antenna is generated by the superposition of oscillators. The higher the gain, the longer the length of the antenna. Gain increase 3dB, double the volume.

3, the higher the gain of the antenna, the better the directionality, the more concentrated the energy, the narrower the wave flap.

Antenna circuit parameters

Voltage VSWR

Antenna voltage standing wave ratio is the antenna as a non-consumptive transmission line load, along the transmission line voltage standing wave generated on the graph, the maximum value and the minimum value of the ratio.

VSWR, is due to the incident wave energy transmission to the antenna input is not all absorbed (radiation) generated by the reflected wave iteration and formed. the larger the VSWR, the greater the reflection, the worse the match. In the mobile communication system, the general requirement of VSWR is less than 1.5.

Input Impedance

Antenna input signal voltage and signal current ratio, known as the antenna input impedance. General mobile communication antenna input impedance of 50Ω.

Input impedance and antenna structure, size and wavelength, in the required working frequency range, so that the input impedance of the imaginary part is very small and the real part is quite close to 50Ω, which is the antenna and feed line in a good impedance matching must be.

Third-order intermodulation

Intermodulation phenomenon is by the frequency band outside the two or more carrier frequencies mixed in the band after the new frequency component, causing the system performance decline phenomenon. Higher power transmit signals are usually mixed to produce an intermodulation signal that ends up in the receive band, where the signal received by the base station antenna is usually of lower power. If the intermodulation signal has a similar or higher power than the actual received signal, the system can mistake the intermodulation signal for the real signal.

Isolation

Isolation represents the proportion of the signal fed to one port (one polarisation) of a dual polarisation antennathat appears in the other port (the other polarisation).

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