Satellite navigation has been used more and more widely in recent years, which has led to the rapid development of navigation terminal antennas. Currently widely used are the GPS (Global PosiTIon System) system and the GLONASS system. The Galileo system under construction is also a global navigation and positioning system. The frequency bands of these global positioning systems are different. For example, the frequency band of GPS is 1575.42±2.046MHz, 1227.60±2.046MHz; the frequency band of Galileo is 1164~1215MHz, 1260~1300MHz and 1559~1592MHz. Although the frequencies used in these navigation systems are different, the frequency range is between 1164 and 1600 MHz. As long as a broadband antenna can be designed to cover this frequency band, the antenna has good versatility and compatibility and can be applied. Different navigation systems.
Since the signals of multiple navigation satellites need to be received for navigation and positioning, the terminal antenna needs to have a wide beam; and because the navigation satellite transmits a right-circularly-polarized navigation signal, the navigation terminal antenna is required to have a good right-handed circle. Polarization characteristics. The antennas used for navigation terminals are reported in many literatures, but basically they are all aimed at GPS systems. The antennas are usually single-frequency, dual-frequency, and tri-band microstrip antennas; some are four-arm helical antennas that do not have low profile characteristics; The shortcoming of the antenna is that it is difficult to achieve a wide frequency band, and it cannot completely cover the frequency bands of all satellite navigation systems, and the receiving system for navigation of different systems is not compatible.
In this paper, a microstrip antenna is proposed, which uses L-type probe feed to widen the antenna frequency band, adopts four-point feed technology to realize circular polarization, and adopts radome and antenna integrated design to ensure the antenna has good environmental characteristics and Mechanical properties. The test results show that the impedance bandwidth of the antenna reaches 44.3%, which can cover all working frequency bands of the existing main navigation system, and has good wide beam characteristics and circular polarization characteristics, and can be used for airborne, spaceborne and ground applications.
2 antenna structureThe model established by the antenna in HFSS is shown in Figure 1. The metal radiation patch has a diameter D of 56 mm and a thickness of 1 mm. The antenna floor is square and the side length L is 80 mm. The antenna supporting medium is square and the side length L is 80 mm. The thickness H of the medium is 19 mm, and the power saving constant of the medium is 3.15; the antenna and the radome are integrated, the radome and the antenna supporting medium are the same dielectric material, and the radiation patch is embedded in the medium, and the thickness H1 of the radome is 3mm; the distance F of the feeding point of the L-shaped feed probe from the geometric center of the antenna is 32 mm, the height H2 of the L-shaped probe is 12 mm, and the length L1 is 17.4 mm.
Figure 1 Antenna structure
3 antenna test resultsThe antenna physical and feed network photos are shown in Figure 2. The antenna return loss test uses the Agilent 8362B vector network analyzer. The test results are shown in Figure 3. It can be seen that the return loss is less than -10dB in the frequency range of 1.16GHz to 1.82GHz, and the impedance bandwidth is 44.3%. All frequency bands of mainstream global satellite navigation systems have good compatibility and versatility.
The antenna pattern and gain were tested in a microwave darkroom. The E-plane pattern measured by the antenna at 1.227 GHz is shown in Figure 4. It can be seen that the maximum gain of the antenna is 4.0 dBi, the beam width of 3 dB is 72°, and the antenna is ±30°, ±50°, ±70°, The gain of ±80° is 1.04 dBi, -0.79 dBi, -3.72 dBi, -6.51 dBi, respectively. The E-plane pattern measured by the antenna at 1.575 GHz is shown in Figure 5. It can be seen that the maximum gain of the antenna is 4.87 dBi, the beam width of 3 dB is 83°, and the antenna is ±30°, ±50°, ±70°, The gain of ±80° is 3.7 dBi, -0.01 dBi, -3.68 dBi, -5.11 dBi, respectively.
The antenna axis ratio pattern is also tested in a microwave darkroom. The test adopts the rotating line source method, that is, the transmitting line polarized ridge horn antenna rotates according to a certain speed (generally 20 times of the measured antenna rotation speed), and the difference between the upper and lower envelopes of the signal received by the antenna to be tested is the axial ratio of the antenna. . The E-plane-to-axis ratio pattern measured by the antenna at 1.227 GHz is shown in Fig. 6. It can be seen that in the ±10° angular domain AR "3dB, in the ±60° angular domain AR "6dB. The E-axis-to-axis ratio pattern measured by the antenna at 1.575 GHz is shown in Fig. 7. It can be seen that the AR is "3 dB" in the ±50° angular range.
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