This paper introduces a new method of testing antenna noise temperature, and the difference from traditional test methods in that the method can correct the impact of the meter itself on the test results, so it has higher precision.
The noise temperature and noise factor are different parameters describing the same physical properties, both of which correspond to the following:
T = (f-1)? T0
Wherein, f is a noise factor (expressed in a logarithmic form, generally referred to as noise coefficient), T is the equivalent noise temperature, T0 is a constant 290K.
For the test of the noise coefficient of the two port devices, the Y factor method is generally used. The method utilizes the noise source, and the noise power when the two states, determines the Y factor, thereby calculating the noise coefficient. What is the difference between the noise coefficient of antenna and the noise coefficient of the normal device? How to test the noise temperature of the antenna?
Unlike ordinary two-port devices, the noise power output from the antenna port includes not only the noise power introduced by itself, but also contains the received background radiation noise. It is because of this, the pitch angle of the antenna is different, and the background noise power received by the antenna is different, then the noise power of the antenna port output is different, so the equivalent noise temperature of the antenna is different.
Antenna noise temperature characterizes, when a given environment and pitch angle, the antenna port outputs noise power! Therefore, the antenna itself can be used as a noise source, and the noise source is turned on by introducing the field amplifier bulle, and the extrave field amplifier indicates that the noise source is turned off, so that the Y factor method can be used, which is the test method described in this article. Thoughts.
Similar to the Y factor method, the antenna noise test method described in the article is also divided into two steps: 1) calibration of the noise coefficient of the spectrum instrument; 2) Test of the antenna noise temperature. When calibrating and testing, you need to use a matching load and field amplifier, and require accurate known field amplifiers gain and noise coefficients.
(A) Introducing a field amplifier is equivalent to the noise source opening (b) to drop the field amplifier is equivalent to the noise source
Figure 1. Calibration of the noise coefficient of spectrum
1. Spectrometer self-noise coefficient calibration
When the matching load and field amplifier are used as a noise source, when the field amplifier is introduced, it is equivalent to the noise source to open; when the fall amplifier is turned off, it is equivalent to the noise source. The ratio of the noise power output during the two states is defined as the Y factor, and the noise coefficient of the spectrometer itself is calculated, and the connection schematic of the spectral noise coefficient calibration is given.
Due to the gain and noise coefficient of the field amplifier, it is possible to deliver the noise coefficient of the spectrometer using the above equation.
2. Antenna noise temperature test
The test idea is similar to the above calibration process, and the antenna and the field amplifier are used as a noise source, in which the field amplifier is introduced, it is equivalent to the noise source to open; when the fall amplifier is turned off, the noise source is closed, the test connection is shown in Figure 2. Show.
(A) Introducing a field amplifier is equivalent to the noise source opening (b) to drop the field amplifier is equivalent to the noise source
Figure 2. Test of antenna noise temperature
The noise factor of the spectrum meter itself has been obtained by the above calibration, and the noise temperature of the antenna to be tested can be obtained.
The entire test process is described in further detail below by a test example.
A amplifier having a gain of 20 dB and a noise coefficient of 4.5 dB as a field amplifier, and the calibration of the spectrometer itself noise coefficient is based on the connection mode given in FIG. When the equivalent noise source is turned off and opened, the spectrum measured noise power As shown in Figure 3, this is only an antenna noise temperature test at 1 GHz as an example. In order to prevent the test results from the spectrometer itself, the prevention of the spectrometer needs to be opened when the test results are high.
According to the above described above, the equivalent noise temperature of the spectrometer at 1 GHz may be calculated to be 7.34 t0, and the corresponding noise coefficient is 9.2 dB.
The noise temperature test of the antenna is shown in the connection mode shown in Fig. 2, and Fig. 4 shows the noise power measured by the noise source closes and opens the spectrometer, and the noise temperature of the final calculated antenna is 1.57 T0.
It is worth mentioning that this paper focuses on test ideas, the antenna test above is not a large size antenna, but a normal antenna, so comparison FIG. 3 and Figure 4, whether or not the noise power difference between the antenna is connected. Not large. Take this as an example here, the detailed process of testing the antenna noise temperature is described in this method.
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Reprinted from -Wiku Electronic Market Network
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