What performance tests do antennas in wireless communication need to undergo?

As an important device for radiating and receiving wireless signals, antenna plays an irreplaceable role.

After the design of an antenna is completed, it needs to be tested to determine whether its performance meets the design requirements. So what performance tests are needed for antenna performance?

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Antenna testing requires the use of professional test equipment, such as antenna test system, RF test cable, etc. Take the Ai-WB2-12F module as an example to see how to test the performance of a PCB antenna.

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Ai-WB2-12F Wi-Fi&BT module developed by Ai-Thinker, the module is equipped with BL602 chip as the core processor, supporting Wi-Fi 802.11b/g/n protocol and BLE 5.0 protocol. BL602 chip built-in low-power 32-bit RISC CPU, 276KB RAM and a wealth of peripheral interfaces, including SDIO, SPI, UART, I2C, IR remote, PWM, ADC, DAC, PIR and GPIO. It can be widely used in the IoT, mobile devices, wearable electronic devices, smart home and other fields.

Test preparation

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(RFI-LAB) is a CNAS accredited professional RF laboratory, a strategic partner of Bluetest IoT OTA testing and certification, and continues to provide in-depth technical services in the RF industry segment.

In addition to RF testing, the service also covers Debug, enterprise standards development, solution recommendation, and so on. Cooperation customers include MI, 360, Hisense, Skyworth, Oakes, ASR and other more than 200 well-known enterprises.

Antenna test prototype schematic

Antenna S parameter

The S parameter is Scatter parameter, which describes the characteristics of the transmission channel.

When dealing with high frequency networks, the equivalent voltage and current and the related impedance and admittance parameters become more abstract. More consistent with the concept of direct measurement of incident, reflected and transmitted waves is the scattering parameter, and S-parameter matrix is more suitable for distributed parameter circuits. S parameter is a network parameter based on the relationship between incident wave and reflected wave, which is suitable for microwave circuit analysis. The circuit network is described by the reflected signal of the device port and the signal transmitted from the port to another port.

Celestial gain

Antenna gain refers to the square ratio of the field intensity generated by the actual antenna and the ideal radiation unit at the same point in space under the condition of equal input power, that is, the power ratio, which quantitatively describes the degree to which an antenna concentrates the input power.

The gain of the antenna compared to the symmetric oscillator is denoted by "dBd". The gain of the antenna compared to the isotropic radiator is denoted by "dBi" (3dBd = 5.17dBi).

The higher the antenna gain, the better the directivity, the more concentrated the energy, and the narrower the lobe. The higher the gain, the longer the antenna length.

Antenna field pattern diagram

At a certain distance from the antenna, the relative field strength of the radiation field, that is, the normalized field strength, changes with the direction of the curve. Generally, it is a three-dimensional stereogram. However, under normal circumstances, they are represented by two perpendicular planes in the maximum radiation direction of the antenna, the so-called "main plane".

Rf OTA data

OTA test, through the "over the air" way to achieve the connection with the test instrument, in addition to the need for the test instrument, but also need to have the OTA chamber, as well as the realization of control DUT and test instrument OTA system software.

Rf OTA (Over The Air) test simulates the transmission scenario of the wireless signal of the product in the air. It is a comprehensive test method to verify the air interface performance of wireless products in free space, which is very close to the actual use scenario of the product.

RF OTA test can completely verify the influence of various factors on the performance of the whole machine, and provide a basis for verifying whether the product meets the relevant certification requirements and the enterprise standard requirements of some manufacturers.

Ai-Thinker Ai-WB2 series product highlights

1. Actual measurement is 400-500 meters (seaside open environment)

2. Compatible with 200+ common routers

3. General AT instruction, easy to develop

4. Continuation of 10 classic hardware packages, fast switching

5.WPA3+ technology support, protect the core firmware

6. Multiple authoritative certifications BQB/FCC/CE/TELEC/SRRC

7. Support the Matter Agreement

8. Support AWS, Alibaba Cloud, Tencent Cloud and other mainstream cloud platforms

9. Widely used, can land photovoltaic, large and small home appliances, electrical lighting, intelligent security, outdoor charging pile, industrial control, smart agriculture and other fields.