Satellite earth station test method-beacon tower Method

I. Test conditions

The beacon tower method is also known as the conventional far-field method. It is a common method to test the antenna pattern in the conventional field.

This is the simplified frame of the antenna tested by the standard tower method.

In the conventional far-field method test [20], to ensure the test accuracy, the following test requirements should be met:

1) the distance between the receiving and transmitting antennas must meet the far-field test distance conditions, that is:

(2-1)

The distance between the source antenna and the antenna to be tested (); the diameter of the antenna to be tested (); and the working wavelength ().

Using formula 2-1, we can calculate the minimum test distance between the antenna and the antenna in the far-field test. Here, Table 2-1 calculates the minimum test distance of the earth station antenna with common calibers based on several frequency points in common band tests.

From table 2-1, we can see that for Earth Station Antennas with small calibers, the antenna pattern can be tested using the conventional far-field method, that is, the beacon tower method; for Earth Station Antennas with large calibers and sizes, the conventional test field method is difficult to meet the far-field test distance conditions. Therefore, it is suitable for satellite field testing.

Table 2-1 minimum distance for antenna testing

Antenna diameter ()	Minimum test distance ()
	Band antenna receiving frequency ()			Band antenna Emission frequency ()
	12.25	12.5	12.75	14.0	14.25	14.5
1.0	81.7	83.3	85.0	93.3	95.0	96.7
1.2	117.6	120.0	122.4	134.4	136.8	139.2
2.4	470.4	480.0	489.6	537.6	547.2	556.8
3.0	735.0	750.0	765.0	840.0	855.0	870.0
3.7	1118.0	1140.8	1163.7	1277.7	1300.6	1323.4
4.5	1653.8	1687.5	1721.3	1890.0	1923.8	1957.5
5.0	2041.7	2083.3	2125.0	2333.3	2375.0	2416.7

 

2) there must be a high enough beacon tower to ensure the antenna elevation angle to be tested. This can effectively suppress the influence of Ground Reflection on antenna testing.

The above are the basic conditions for the far-field test field. The far-field method is a common site for the test antenna. Its Notable features are that the test control of the entire antenna is convenient and unrestricted. In addition, the output power of the signal source is high, high spectrum analyzer sensitivity, the test system generally does not require high-power amplifier or low-noise amplifier; furthermore, the antenna test frequency and plan can be freely selected according to the test needs.

Ii. Test Procedure

1) Build an antenna and a signal source on the beacon tower according to the frame diagram.

2) Reasonably set the spectrum analyzer's working status based on the antenna testing requirements and antenna rotation speed, such as setting the center frequency, span, resolution bandwidth res BW, video bandwidth video BW, scan time and so on. After setting, the antenna orientation and pitch motor are driven to adjust the orientation and pitch angle so that the antenna can be aligned with the maximum signal of the main wave bundle center.

3) The antenna is aligned with the azimuth (pitch) angle of the maximum signal as the reference angle, and the driving antenna motor causes the antenna to deviate from a certain azimuth (pitch) angle of the maximum signal. The span of the spectrum analyzer is set to 0 to control the antenna rotation orientation (pitch) motor, and the spectrum analyzer scans the signal power levels within the azimuth (pitch) angle range. The spectrum analyzer obtains the power levels of scanning points in a range. The antenna direction test angle of the Frequency Band Satellite Communication Earth Station is usually, and the frequency band is usually enough.

4) The spectrum analyzer draws the antenna pattern and analyzes the antenna pattern to obtain various performance indicators of the antenna.