Xiangqiang Li

A GW Level High-Power Radial Line Helical Array Antenna

High-power radial line helical array antenna is a novel antenna developed to realize directional radiation of high-power microwaves. This antenna directly accepts an azimuthally symmetric output of a high-power microwave source and radiates circularly polarized microwave with a boresight peak. It has a high efficiency, a compact structure, and a notable power-handling capacity. Starting from its fundamental design theory, an antenna prototype consisting of 48 elements is proposed. Numerical simulation and experimental measurement are accomplished for the prototype. In the range of 3.7-4.1 GHz, the experimental result shows an antenna VSWR of below 1.2, an antenna gain of over 23.2 dB, an aperture efficiency of more than 65%, and an antenna axial ratio of below 1.6 dB. In addition, the high-power experiment proves that this antenna has a power-handling capacity of more than 1 GW.

16-Element Single-Layer Rectangular Radial Line Helical Array Antenna for High-Power Applications

A 16-element single-layer rectangular radial line helical array antenna is proposed and investigated. In the single-layer radial line feed system, two new probes are used to satisfy the coupling requirement. The sequential rotation technique is introduced to improve the axial ratio of the antenna. An antenna prototype is designed, simulated, and measured. The results indicate its advantages of high aperture efficiency, low input VSWR, and favorable axial ratio. The field distributions of this antenna are analyzed through simulation, which prove its advantage of high power-handling capacity. This array is also used to form an 8 × 8 array antenna, which demonstrates its ability to be used as a subarray.

A HIGH-POWER LOW-LOSS MULTIPORT RADIAL WAVEGUIDE POWER DIVIDER

A 16-way radial waveguide power divider with the characteristics of low insertion loss and high power handling capacity is investigated. Its design theory and basic structure are proposed at flrst; a power divider with the center frequency of 4.0GHz is designed, fabricated, and measured. Good agreement between the simulated and measured results is found for the proposed power divider. The measured 15-dB return loss bandwidth is demonstrated to be 440MHz and the measured 0.5-dB insertion loss bandwidth is demonstrated to be 540MHz. The power handling capacity of the proposed power divider is analyzed through simulation, and the results prove its usability in high power applications.

High Power 12-Element Triangular-Grid Rectangular Radial Line Helical Array Antenna

A 12-element triangular-grid rectangular radial line helical array antenna is proposed and investigated. The major characteristic of this antenna is that its radiation elements are arranged in triangular-grid, which is helpful to reducing the number of elements demanded for a certain antenna aperture and grating lobe suppression capacity. The radiation element is optimized to facilitate the manufacture. The feed system with six different groups of output ports is designed to obtain equal- amplitude output using three kinds of probes. An antenna prototype with the center frequency of 2.856 GHz is simulated and measured. In the range of 2.75-2.95 GHz, the experimental result shows an antenna VSWR below 1.2, an antenna gain over 16.3 dB, and an aperture efficiency more than 80%. The field distributions of this antenna are analyzed through simulation, which prove its advantage of high power-handling capacity. Its ability to be used as a sub-array is also demonstrated by forming a 48-element array antenna.

Double - Layer Radial Line Helical Array Antenna with Rectangular Aperture

A double-layer radial line helical array antenna with rectangular aperture is proposed. With rectangular aperture, the antenna can be assembled to form high gain antennas. The use of double-layer feed system ensures an equal-amplitude in-phase feed for all elements in an expected frequency band, which can improve antenna gain and aperture e-ciency. This paper presents its design concept, derives pertinent design and performance, and a 16-element array antenna is simulated and measured. The experimental results show that in the range of 3.8GHz to 4.2GHz, the antenna gain is over 17.7dB, aperture e-ciency over 82%, antenna sidelobe level below i12:0dB, antenna axial ratio below 3.2dB, and antenna VSWR below 1.52.

A compact TE11-TM01 mode converter for HPM application

ABSTRACT A mode converter using circular waveguide has been investigated. The conversion is based on the structure of two orthogonal circular waveguide and there is a tuning screw placed at the short-end used to increase conversion efficiency and bandwidth. The results show that the converter is not only compact but also wide-band, which realize a bandwidth of 11∼14 GHz for conversion efficiency over 90%. The simulated power capacity is 798 MW at 12.7 GHz under vacuum condition.

Novel overmode circular waveguide bend for high power tm 01 mode transmission

A novel structure of overmode circular waveguide bend is investigated, which is used to transmitter circular waveguide TM01 mode with high power-handing capacity, high transmission efficiency and small bend radius. Metal plates and metal rod are used to change the type of waveguide. In the bend of the structure, circular waveguide is split into four sector waveguides, and the phase difference between sector waveguide TE11 modes changes from 0 to 2π, that means the phases of sector waveguide TE11 modes are also same after bending. Four sector waveguide TE11 modes with same phase convert to coaxial TEM mode at the end of the metal plates, which finally converts to circular waveguide TM01 mode and is outputted. Microwave propagates with singlemode in the bend of the structure, that can avoid exciting high-order mode. Experimental test results show that VSWR is below 1.3 in the range of 8.25–8.55 GHz and less than 1.07 at 8.4 GHz and the insertion loss is 0.2 dB at 8.4 GHz, which prove the feasibility of the structure of the overmode circular waveguide bend.

HIGH POWER OVER-MODE BENT WAVEGUIDES FOR CIRCULAR TM01 AND COAXIAL TEM MODE TRANSMISSION

Three bent waveguides are proposed and investigated, two for circular waveguide TM01 mode and one for coaxial TEM mode. For high power-handling capacity, all of them are over-mode waveguides. In the bend, circular or coaxial waveguides transmitting only sector waveguide TE11 modes are split into several same sector waveguides by metal plates and metal rod. These sector waveguides are grouped by their lengths. Length differences of sector waveguides lead to phase differences of the sector waveguide TE11 modes after bending. Due to requirements of mode conversion, the phase difference regulated by radii of circular waveguide and metal rod must be 2nπ, n = 0, 1, 2, . . .. Since the phase difference is independent of bend radius, the radius could be as small as possible. One of the prototypes is experimentally verified, and the test results of the VSWR show that simulation has good match to experiment. Insertion loss is 0.2 dB at 8.4 GHz, which proves the feasibility of the prototype.