The main parameter of antenna performance are antenna gain,side lobe,noise temperature,G/T,VSWR and so on. The quality of main parameters will affect the receiving or transmitting performance of antenna,so before delivery,we have to test the antenna to ensure that all of them meet the requirements.But how to test antenna? Let’s learn together.
1. Antenna gain
For ensuring the accuracy and reliability of the antenna gain measurement data,the beacon tower method is used to measure the antenna pattern and gain.
1)Test method:
First set up signal source, the test distance is ≥2(D)²/λ,and use general 3dB-10dB measurement method to measure antenna gain.
2)Test instrument needed:
The needed test equipment of 3dB-10dB test method to measure antenna gain is shown in the figure below.
2.Test for antenna side lobe performance
1)Test method:
The antenna pattern characteristics will be measured by the beacon tower method.
2) Test instrument needed:
The equipment configuration for testing the antenna pattern using a beacon toweris shown in the figure below:
3.Test for antenna noise temperature
1)Test method:
A.The antenna noise temperature measurement diagram is shown in the figure below, and the antenna noise temperature is measured by the Y factor method.
b. Connect the LNA to the load at room temperature, adjust the working status of the spectrum analyzer, and record the noise power P1 measured by the spectrum analyzer at this time;
c. Under the same test conditions, connect the LNA to the antenna to be tested, and record the noise power P2 measured by the spectrum analyzer at this time;
d. The gained Y factor is as below formula(1):
(1)Y=10（P1-P2）/10
Using the tested Y factor to calculate the noise temperature of antenna feed system as below formula(2)(In the formula:T0 is the environmental temperature,TLNA is the LNA noise temperature) :
(2)
The noise temperature of antenna feed system is as below formula(3)(Feed network export):
(3)
2) Test instrument needed:
The antenna noise temperature measurement generally adopts the Y factor method.
The test equipment configuration is shown as followed.
4.Test for antenna Rx G/T
1) Test method:
By receiving the radio source signal, the Y factor method is used to measure the
antenna receiving G/T
2)Test instrument needed:
The equipment configuration for testing antenna gain by radio source signal
method as followed:
3)The formula to calculate the G/T value :G/T=G-10log(T)
5.Test for antenna circular axis ratio
1) Test diagram:
The test diagram is as followed:
2) Data processing
Use a spectrum analyzer to record the level change trajectory when the transmitting horn rotates, and record the difference between the largest signal and the smallest signal during a cycle, which is the axial ratio of the antenna to be tested expressed in decibels.
From the measured axial ratio of the feed expressed in decibels, the value of thevalue can be calculated by the formula:
In the formula:
The ar is the value of the axial ratio, and AR is the axial ratio expressed in decibels.
6.Test for antenna feed VSWR
1) Test diagram:
The test diagram is as followed:
2)Test method:
Please connect the entire test system according to below diagram;
Ø The system enters a stable state after preheating for 0.5h after booting up;
Ø The output port of the measured microwave feed is connected to the measurement system. If the microwave feed is a multi-port output, the other ports are connected to the load during measurement;
Ø Set the appropriate measurement system status; set the measurement frequency;
Ø Perform open-circuit calibration, short-circuit calibration, and load calibration on the measurement system at the vector network analyzer connection port;
Ø Connect the vector network analyzer to the measured microwave feed source for measurement and record the output;
Ø Change the measurement port, repeat steps from ③～⑥.
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