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High Performance Extended C Band Circular Polarization four port Diplexer Deliveried to Customer.
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Author : Alignsat
Update time : 2021-02-20 17:18:53
Extended C Band Circular Polarization 4 port Diplexer Test Report
- Visual inspection
- Testing purposes
- Performance index test content
RX: 3.4GHz,3.8 GHz, 4.2 GHz
TX: 5.85GHz,6.2875 GHz, 6.725GHz
- Pattern
- Circular polarization axis ratio
- Feed insertion loss.
- VSWR
- Port to port isolation test
- Test environment
- Near field scanning test principle
5.1. Operating principle
The operating principle block diagram of near field measurement system is shown in Fig 2.
The RF signal emitted from the RF source passes through Agilent 87300C directional coupler and one circuit is sent to the transmission antenna as the RF test signal and the other circuit is sent to Agilent 85320B reference mixer as the reference signal of RF.
The RF test signal which is received by the tested antenna is sent to Agilent 85320A test mixer, transformed into intermediate frequency signal and sent to the receiver via amplifier as the test signal of IF.
The RF reference signal from the directional coupler is sent to the reference mixer, transformed into IF signal and is output the other end of the receiver of the amplifier as the reference signal of IF.
The ratio between the test signal of IF to the reference signal amplitude and phase of IF is amplitude and phase of the final tested signal of the system.
5.2 Test block diagram
The near field test block diagram of the antenna is shown in Fig 3.
5.3 System composition
5.3.1 NSI mechanical sub-system
NST inverted T upright 5.4mx5.4m m scanning plane consists of ARC axis controller (axis Y, axis Y, axis Z and polarization axis), step motor and wave guide prober of various frequency bands.
5.3.2 RF sub-system
The RF sub-system consists of two parts, in which the Tx sub-system consists of Agilent E8274C comprehensive source,HP87300C directional coupler and Tx antenna. The Rx sub-system consists of Agilent E8274C signal source, frequency converter, Agilent E8363B vector network analyzer and RX antenna. The frequency converter also contains Agilent 85320A/B mixer module, Agilent 85309C L.O/intermediate frequency distribution unit.
5.3.3 Computer sub-system
It consists of NSI 2000 Windows system software, NSI 2000 DOS system controller and corresponding accessories.
6. Test items
6.1 Test of patterns
a) Replacement of frequency mixer
Select the frequency mixer of corresponding frequency band in accordance with the range of test frequency.
b) Installation of probe
Select appropriate band probe and install it on the scanning plane.
c) Installation of the tested antenna. As shown in Fig 3, install the tested antenna on the appropriate position.
d) Switch on the instrument and enter into the main interface of NSI 2000 test software , move the scanning plane probe and align it to the center of the tested part.
e) Setting of parameters of the tested part
Set the length and width of the tested antenna firstly, then set the scanning range of the probe ,finally input the probe to the distance to the tested antenna.
f) Set the frequency of the tested antenna.
g) Set probe
The polarization mode of the probe is set into horizontal and vertical polarization respectively. Carry out test for two times to obtain the patters of main polarization and cross polarization respectively.
h) Set sampling point numbers.
i) Input the tested items.
j) Start the test
Finally, the far field data is obtained by NSI 2000 software via Fourier Transform calculation in accordance with the result of near field test data.
6.2 Test of cross polarization isolation
6.2.1 Test method
The principle block diagram of cross polarization isolation in the near field test is shown in Fig 3. The patter F(θ)to the main polarization and the patter f(θ) to cross polarization is tested for two times by way of controlling the polarization of the probe antenna at the condition of horizontal and vertical polarization, then the axial cross polarization isolation XPD is obtained by the computer process.
In case of real testing, it is as real as possible to reflect the cross polarization isolation feature of the antenna. Before scanning the cross polarization pattern, the polarization of the antenna is fine tuned by ACU so to make the tested antenna and the probe polarization match. The pattern of main polarization F(0)and of cross polarization is obtained by the test . The cross polarization XPD is obtained by the software calculation, namely:
XPD= F(θ)- (θ) (1)
6.2.2 Test procedure
a) Put the antenna to be tested on the test frame and the test system is shown in Fig 3, apply the power and warm up the instrument and equipment of the test system so to keep them operate normally.
b) Complete main polarization as per item 6.1,keep the condition of the tested antenna unchanged ,keep the probe rotate for 90° and complete the scanning of the cross polarization pattern.
c) Scan the near field pattern of cross polarization of the tested antenna as per the method in item 6.1.
d) Use computer to collect and proceed the tested data and calculate the axial cross polarization isolation of the tested antenna by formula (1).
6.3 Test of axial ratio
6.3.1 Test method
The principle block diagram for near field axial ratio test is shown in Fig 3. The pattern of main polarization F(θ)and of cross polarization f(θ) is obtained by way of controlling the polarization of the tested antenna. Then ,the axial cross polarization isolation XPD is obtained through the computer process.
In case of real testing, it is as real as possible to reflect the cross polarization isolation feature of the antenna. Before scanning the cross polarization pattern, the polarization of the antenna is fine tuned by ACU so to make the tested antenna and the probe polarization match. The pattern of main polarization F(0)and of cross polarization f(0) is obtained by the test .The cross polarization XPD is obtained by the software calculation, namely formula (1); Then the feed antenna axial ratio is obtained through the software calculation again ,namely formula (2).
AR=20Log((1+10
/(1-10 
(2)6.3.2 Test procedure
It is the same as item 6.1.
6.4 Test of insertion loss
The test block diagram is shown in Fig 4.
Fig 4. The test block diagram
6.4.1
。Since the loss of the tested feed is vary small ,therefore we connect two sets of networks with same structure form and SWR together at the feed network interface ,use vector network analyzer to perform the test at the corresponding port of the two sets of network and the test value is the loss of the two sets of network, then divided by 2 and the loss of one set of network is obtained.
。The set frequency of instrument is the corresponding test frequency and the test response is S12.The test item is Log-Mag( logarithmic amplitude - <dB>);
。Connect the co-axial conversion of two pieces of wave guides and calibrate the test system;
。Connect the co-axial conversion of the wave guide to the corresponding port of the tested feed and read out directly the loss curve of corresponding port of the tested antenna and mark the maximum loss of the corresponding channel of the tested feed (two sets of networks);
。Change the test frequency of the test instrument and the test accessories and test the loss of other channel of feed in accordance with the method mentioned above.
6.5. VSWR test at the antenna port
Such test equipment as vector network analyzer, corresponding wave guide high direction directional coupler (test electric bridge) and short circuit calibration plate are used for the test of SW at the port of antenna. After calibrating the test equipment, connect the tested port directly to the corresponding port of the tested antenna and read out SWR of the port of the tested antenna directly form the instrument. The specific block diagram is shown in Fig 5.
6.5.1 Test method and procedure
。According to the block diagram, connect the instrument and the corresponding wave guide high direction directional coupler (test electric bridge);
。The set frequency of the instrument is the test frequency ,the test response is S12 and the test item is SW;
。Calibrate the complete test system with the short circuit calibration plate;
。Connect the test electric bridge to the corresponding port of the tested antenna, read out directly the SW curve of the tested antenna and mark the maximum SW of the corresponding port of the tested antenna.
。Change the test frequency of the test electric bridge and the instrument and test the SW of all ports of the tested antenna as per the method mentioned above.
6.6 Test of port isolation of antenna
Firstly, connect the instrument and corresponding wave guide co-axial conversion as per the above block diagram.
The set frequency of instrument is the corresponding test frequency and the test response is S12.The test item is Log-Mag( logarithmic amplitude -<dB>);
Connect the co-axial conversion of two pieces of wave guides and calibrate the test system;
Connect the co-axial conversion of the wave guide to the corresponding port of the tested feed and read out directly the isolation curve of corresponding port of the tested antenna and mark the minimum isolation of the corresponding port of the tested antenna;
Change the test frequency of the test instrument and the test accessories and test the isolation between other ports of the tested antenna as per the method mentioned above.
- Test Ruselt
Table 1, result of axial ratio,
| Band | TX/RX(GHz) | TEST FREQUENCY | Axial Ratio Result(dB) |
| C |
RX |
3.4 | 0.15 |
| 3.8 | 0.16 | ||
| 4.2 | 0.18 | ||
| TX |
5.85 | 0.05 | |
| 6.2875 | 0.12 | ||
| 6.725 | 0.16 |
Table 2, result of Feed Insertion loss,
| Band | TX/RX(GHz) | TEST FREQUENCY | Feed Insertion loss(dB) |
| C | RX | 3.4—4.2 | 0.47(2set) |
| TX | 5.85—6.725 | 0.42(2set) |
Table 3, result of VSWR,
| Band | PORT | TEST FREQUENCY | PORT VSWR |
| C |
RX-LHCP | 3.4—4.2 | 1.12 |
| RX-RHCP | 3.4—4.2 | 1.09 | |
| TX-LHCP | 5.85—6.725 | 1.08 | |
| TX-RHCP | 5.85—6.725 | 1.07 |
Table 4,result of Port isolation,
| Band | PORT | TEST FREQUENCY | PORT isolation(dB) |
| C |
RX-LHCP- RX-RHCP | 3.4—4.2 | -19.7 |
| TX-LHCP- TX-RHCP | 5.85—6.725 | -20.3 | |
| TX-LHCP- RX-RHCP | 3.4—4.2 | -98.5 | |
| TX-RHCP- RX-LHCP |
5.85—6.725 | -98.6 |