Wideband High Power Horn Array Antenna with High Reliability
Pei Li, Peng Li, Xu Luo, Liming Xu, Zhijie Zhou, Qingtao Duan Science and Technology on Electronic Information Control Laboratory
Chengdu, Sichuan [email protected]
Abstract—A wideband high power horn array antenna with high reliability is presented in this paper. This antenna consists of a modified double ridged horn array composed of 26 elements and a simple cooling system which prolongs the life of radome. Simulations and experiments were conducted to demonstrate the effectiveness of the given antenna. Measured results show that the gain of the array antenna with a ±30°
beam scanning range between 18 and 28dB. The proposed antenna also has high reliability by test and verify.
Keywords—wideband, horn array, high power microwave, double ridged horn, high reliability, cooling system
I. INTRODUCTION
There is an increasing concern on design of antenna in high-power microwave (HPM). Due to the nature of HPM, HPM antennas should meet special requirements, such as a high power handling capacity and compact structure, to ensure favorable radiation transmission and receiving [1].
Many kinds of HPM antennas were given in recent years, such as the HPM radial line helical array antenna [2], mechanically pattern-reconfigurable bended horn antenna for high-power applications [3], high-power dual-branch helical antenna [4] and so on. Horn antenna have been widely studied and applied in the high-power microwave due to the advantages of simple structure, high power capacity and high directivity [5]. However, as the operating band increasing, the double ridged horn loading two ridged structures is becoming a good candidate for the increasing demand due to reduce the cutoff wavelength of ridged waveguide.
Meanwhile, phased array is introduced to get much more high-power in the application. The safety of radome, which can protect antenna from environmental impact should be considered for the reason that radome has been widely applied in many applications.
In this paper, a wideband horn array antenna is proposed.
In order to realize 3:1 bandwidth performance, a modified double ridged horn is designed to the array element. The simulated and measured results indicate that the designed horn array antenna achieves high gain, wide beam scanning range and high reliability.
II. ANTENNA DESIGN
In order to evaluate the power capability of the array, a figure of merit for effective radiated power (ERP) can be defined as
ERP=N2*P0*G0*η (1) Where N means the number of elements, P0 means the power of array element, G0 means the gain of array element, η means the efficiency of array. ERP can be increased by adding the number of elements from (1).
A. Antenna Design
The proposed horn array is constructed using 26 elements of horn which operates at X/Ku-band frequency of 6GHz~18GHz, including 2 virtual elements which promise each operating element the same radiation pattern. Minimum element spacing that is the same distance of width of each horn can be known from the maximum scan angle, due to cancel gating lobes. Minimum element spacing (dmin) can be gotten from equation (2) .
d < (2) Where λ means the wavelength of the highest operating frequency, means maximum scan angle of ±30° The width of each horn is about dmin, which is also small length of about 20% wavelength of lowest operating frequency at the same time. A modified double ridged horn is prepared to solve this problem of each horn with low profile. The configuration of the proposed horn antenna is shown in Fig.
1 (a). The width of ridged structure of the proposed horn compares changed with the ordinary horn shown in Fig. 1 (b).
(a)
(b)
Fig.1. The proposed design and ordinary (a) modified ridged horn (b) ordinary ridged horn
Due to usage of changed width of ridged structure, there exists more available degrees of freedom for optimal design to operate 3:1 bandwidth in modified one compared with the ordinary one.
Fig.2. The proposed antenna array
A schematic configuration of the propose array is shown in Fig.2. It consists of 24 operating elements and 2 virtual element of modified double ridged horn, a metal plate which reflects and shields electromagnetic waves. Each horn is connected to a high-power wideband coaxial-to-waveguide transducer, in order to facilitate testing and verification. The antenna radiating aperture is 40mm away from the metal plate, in order to keep good performance of radiating pattern.
B. Cooling System Design
Radome composed of microwave-transmitting material is necessary for the antenna array in many kinds of HPM applications. Due to the safety of radome, the distance between antenna aperture and radome surface is as far as possible in order to reduce electric field intensity of radome surface. Another way is using the low loss material as radome material, which can reduce material heat due to loss of material. On the basis of the above, a simple cooling system composed of four fans is design to improve the life time of radome. Two fans act as air intakes and two fans act as outlets. This cooling system has good performance of heat dispersion by choosing the optimized location of four fans on the metal plate. The optimized location of four fans on the metal plate shown in Fig. 3.
Fig. 3. The optimized location of four fans III. SIMULATIONANDMEASUREMENTRESULTS The given antenna with cooling system was simulated and certificated by experiments to derive the performance.
A. Antenna
The radiation pattern was calculated by HFSS and measured in anechoic chamber. Fig. 4 shows the simulated and measured radiation patterns of this proposed antenna in E-plane at three different frequencies about 6GHz, 12GHz and 18GHz. The patterns of each frequency include patterns of middle and edge beam to check beam scanning ability. It is seen that the measured patterns agree well with the simulated ones and that the given design can be operated at 3:1 bandwidth. It is also noted that the maximum gain isn’t much difference between middle and edge beam, meanwhile
the gain of this proposed antenna is between 18 and 28dB in
±30° beam scanning range.
(a)
(b)
(c)
Fig. 4. Simulated and measured radiation patterns (a) 6GHz (b) 12GHz (c)18GHz
B. Cooling system
Due to verify the effectiveness of the proposed cooling system, the following experiment is designed. A schematic configuration of the experiment is shown in Fig.5. It consists of a beam network which is used for beam forming to achieve beam scanning, 24 high power amplifiers which are used for supplying total inputting power of 2400W.
air outlet air outlet
air intake antenna array
metal plate
…
…
…
…
Radome
Antenna arra y
Hi gh powe r a mplifier
Beam network
Fig. 5. A schematic configuration of the designed experiment Finally, results of cooling system experiment are summarized in Table I. It is essential to check and measure the radome temperature after each test cycle, which lasts one hour at full power of 2400W. The radome has good look after 8 test cycles and the results shows effectiveness of the cooling system in table I.
TABLE I. RESULTS OF EXPERIMENT
frequency Scanned angle Total power High temperature
12GHz 0º 2400W 40 ºC
12GHz 30º 2400W 45 ºC
18GHz 0º 2400W 35 ºC
18GHz 30º 2400W 39 ºC
The given antenna with cooling system shows good performance of radiation ability and high reliability by
simulated and measured results. More details of design and experiment will be appeared and discussed in the conference.
IV. CONCLUSION
This paper has presented a wideband horn array antenna with a simple cooling system. The designed antenna exhibits
±30° beam scanning range. A fairly good agreement has been observed between simulated and measured results of radiation pattern. It is shown that radome has high reliability by cooling system design and experiment. The described design can be potentially very useful for high power microwave applications.
REFERENCES
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[2] Xiangqiang Li, Qingxiang Liu,etc, “A GW level high-power radial line helical array antenna”, IEEE Trans.Antennas Propag., vol. 56, no.
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[3] Antoine Jouade, Mohamed Himdi, Antoine Chauloux, and Franck Colombel,“Mechanically Pattern-Reconfigurable Bended Horn Antenna for High-Power Applications”, IEEE Antennas and Wireless Propagation Letters, vol. 16, pp. 457-460, Mar. 2017.
[4] Yuan Liang , Jianqiong Zhang , Qingxiang Liu, and Xiangqiang Li,
“High-Power Dual-Branch Helical Antenna”, IEEE Antennas and Wireless Propagation Letters, vol. 17, no. 3, pp.472-475, Mar. 2018 [5] A. D. Olver and J. Xiang. “Design of profiled corrugated horns”,
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