An antenna is virtually a conductor exposed in space. The electrical energy input to the antenna is radiated in the form of electromagnetic radiation of those frequencies to free space, that bridges the wireless device and its remote counter parties. The antenna is one of the most important components for the RF transmitter and receiver modules. An antenna of good performance is able to greatly improve the transmission range and signal strength from the wireless module. Hence it is very important to choose a suitable antenna for the wireless modules.
There are some key factors when it comes to choosing optimal antennas for the wireless application to develop:
1. The Bands, Frequencies:
Every wireless module has its own working frequencies, such as 433MHz, 700MHz, 868MHz, 1900MHz, 2100MHz, 3500MHz, 5200MHz etc.; The antenna features working bands, too. The frequency band of the antenna must be compatible with the bands of the wireless module. Otherwise, the overall transmission and/or the receiving efficiency of the wireless module will be very poor. The difference of frequency band cause smaller radiation range of the antenna and accordingly it leads to a short transmission distance. Santa Fe offers whole-series antennas for matching those modules from Sierra Wireless, Mediatek, Telit, Huawei, Gemalto, uBlox, and ZTE for 5G, LTE, ISM, Wi-Fi bands.
2. Radiation efficiency:
Radiation efficiency is an important parameter to describe how efficiently an antenna transmits and receives RF signals, which is defined as the ratio of the total power radiated by an antenna to the total input power received from the generator. An antenna with high radiation efficiency efficiently radiates the input power to free space. In the case of low radiation efficiency, the input power is mostly dissipated because of the internal losses such as metal conduction, dielectric and magnetic losses within the antenna. A radiation efficiency of 100 percent indicates that all non-reflected power is radiated to free space.
3. Radiation pattern:
Radiation pattern indicates the directional property of radiation, which directions radiate more while others do less. This information helps to orient the antenna properly in a field application. A wire antenna is the best in RF performance, typically performs good antenna efficiency and quality directivity compared to other antennas. Directional antennas are widely applied by most of the telecom cellular base stations or local network signal amplifiers.
4. Gain value:
The gain value is a very important parameter of the antenna. The unit is dBi and the gain value is positive. The higher the gain value, the higher the gain effect on the
5. VSWR(Voltage Standing Wave Ratio):
VSWR is the ratio of the amplitude of the standing wave and the voltage of the valley, which is also called the standing wave coefficient and the standing wave ratio. It is mainly used to describe the matching of the antenna. When the VSWR is equal to 1, it means that the impedance of the feeder and the antenna are completely matched, which is the most ideal case. When the VSWR is higher than 1, it means that some electric waves will be reflected back and become heat, hence the feeder is warmed up. Nowadays scanning the efficiency of an antenna is more convenient and less costly in an anechoic chamber. Antenna efficiency becomes an more important indicator than simply VSWR comparison.
6. Working environment:
Each application has its unique working environment or installation restrictions, so the antennas used will vary accordingly. If the environment is in harsh and many sources of interference, the performance of the wireless device will be negatively affected. High-gain external antenna, such as rod antenna, sucker antenna and Yagi antenna are recommended for those environments. The high-gain antenna can increase the anti-interference ability. If external antennas are not acceptable, embedded antenna of PCB(FR4) or flexible PCB(FPC) would be applicable choices. The “clearer” the position of the antenna, the better the signal transmission and the longer the transmission range is expected. It should be kept open and far away, “keep out”, from metals, buildings and other interference sources.
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