Xidong Wu

Air-Filled Parallel-Plate Cylindrical Modified Luneberg Lens Antenna for Multiple-Beam Scanning at Millimeter-Wave Frequencies

This paper presents a novel design of cylindrical modified Luneberg lens antenna at millimeter-wave (mm-wave) frequencies in which no dielectric is needed as lens material. The cylindrical modified Luneberg lens consists of two air-filled, almost-parallel plates whose spacing continuously varies with the radius to simulate the general Lunebergs Law. A planar antipodal linearly-tapered slot antenna (ALTSA) is placed between the parallel plates at the focal position of the lens as a feed antenna. A combined ray-optics/diffraction method and CST-MWS are used to analyze and design this lens antenna. Measured results of a fabricated cylindrical modified Luneberg lens with a diameter of 100 mm show good agreement with theoretical predictions. At the design frequency of 30 GHz, the measured 3-dB E- and H-plane beamwidths are 8.6° and 68°, respectively. The first sidelobe level in the E-plane is -20 dB, and the cross-polarization is -28 dB below peak. The measured aperture efficiency is 68% at 30 GHz, and varies between 50% and 71% over the tested frequency band of 29-32 GHz. Due to its rotational symmetry, this lens can be used to launch multiple beams by implementing an arc array of planar ALTSA elements at the periphery of the lens. A 21-element antenna array with a -3-D dB beam crossover and a scan angle of 180° is demonstrated. The measured overall scan coverage is up to ±80° with gain drop less than -3 dB.

Millimeter-Wave Fan-Beam Antenna Based on Step-Index Cylindrical Homogeneous Lens

A novel step-index cylindrical homogeneous lens at millimeter-wave (MMW) frequencies is designed by using the technique of parallel plates propagating the TE1 mode. The cylindrical homogeneous lens, which is sandwiched between two parallel conducting plates, has an H-shaped cross section to give the desired step-index of refraction. For a given aperture size, the focal length of the cylindrical homogeneous lens can be adjusted by changing the cross-section structural parameters rather than the dielectric material itself, which should be highlighted for cylindrical homogeneous lens for the first time. A planar linearly tapered slot antenna (LTSA) is chosen to feed the cylindrical homogeneous lens. The ray-tracing and transverse resonance methods are used to analyze and design this lens antenna at 30 GHz. Measured results of the fabricated lens antenna show good agreement with simulations. At 30 GHz, the measured 3-dB E- and H-plane beamwidths are 6.1° and 50.2°, respectively, and the first sidelobe level in the E-plane is -16.3 dB. The measured gain is 17.9 dB, corresponding to a radiation efficiency of 67.2%.

Closed-Form Design of Wilkinson Power Divider with Broadband Harmonic Suppression and Size Reduction

This paper presents a novel design concept of power divider, capable of broadband harmonic suppression and realized by replacing the branch lines of the modified Wilkinson power divider with wideband open-stub bandstop filters. For verification, a power divider operating at 1 GHz is designed, fabricated and tested. The realized power divider occupies a core size of only 26.3 mm × 18.1 mm, or 0.15λg × 0.10λg. Measurements show that broadband harmonic suppression is achieved from 1.95 GHz to 6.00 GHz with spurious attenuation better than 30 dB.

A dual-band Wilkinson power divider with 6:1 power dividing ratio using coupled lines

The Wilkinson power divider is a fundamental component in microwave systems such as the feeding network for an antenna array. It is usually operated at a single frequency band by employing quarter-wavelength transmission lines [1]. Recently, several structures of dual-band Wilkinson power divider have been proposed for equal power dividing [2]-[3] and for 2:1 unequal power dividing [4]. However, there is no report on dual-band Wilkinson power divider with power dividing ratio higher than 4:1.

A Cavity-Backed Aperture-Coupled Microstrip Patch Antenna Array with Sum/Difference Beams

Abstract This paper presents a new cavity-backed aperture-coupled microstrip patch antenna (ACMPA) array with sum/difference beams. It is composed of a feed network and two aperture-coupled elliptical patch antennas. A metallic cavity is used at the back of the antenna array to minimize the back radiation. The feed network is realized by a planar magic-T, which consists of microstrip and slotline T-junctions coupled by microstrip-slotline transitions. The antenna is designed, manufactured and tested at 35 GHz. Measurements show clean and symmetrical patterns are realized for both the sum and difference beams. The measured −3-dB E- and H-plane beamwidths of the sum pattern are 55.8◦ and 77.6◦, respectively. A deep null of −32.4 dB is achieved for the difference pattern. Meanwhile, the measured return losses for both the sum and difference ports are less than 10 dB from 34.2–36.6 GHz corresponding to a bandwidth of 6.8%. Within this bandwidth, the isolation between the sum and the difference ports is better than 38 dB.

Millimeter-wave homogenous cylindrical lens antenna for multiple fan-beam scanning

A multi-beam cylindrical lens antenna operating at mm-wave frequencies has been designed using dielectric-filled parallel plate techniques. The system is composed of a homogeneous cylindrical lens and an arc feed array of planar linearly tapered slot antenna (LTSA). The cylindrical lens is made out of Rexolite (ϵ r = 2.54) and sandwiched between two parallel plates. The LTSA feed array is placed between the parallel plates at the periphery of the cylindrical lens to launch multiple beams. A ray-tracing method and CST-MWS are used to analyze and design this cylindrical lens antenna at 30 GHz. Measured results of a fabricated cylindrical lens, with a diameter of 100 mm, show good agreement with simulations. The measured 3-dB E- and H-plane beamwidths are 6.0° and 52°, respectively, and the sidelobe level in the E-plane is −14.7 dB. An impedance bandwidth of 16.7% is achieved over which the measured aperture efficiencies are better than 61.5%. The measured E-plane patterns of a 25-beam array with a crossover of −3 dB and a scan angle of 150° are also demonstrated, which provide a wide scan angle at mm-wave band.

A millimeter-wave cylindrical modified Luneberg lens antenna

A new cylindrical modified Luneberg lens antenna at millimeter-wave frequencies is designed using parallel plate techniques. The cylindrical modified Luneberg lens consists of two parallel plates which are filled with air. The plates spacing is continuously varied with the normalized radius to achieve a general Lunebergs variation of the effective index of refraction. A planar antipodal linearly-tapered slot antenna (ALTSA) is placed between the parallel plates at the focal position of the lens as a feed antenna. A ray-tracing method and CST-MWS are used to analyze and design this cylindrical lens antenna at 30 GHz. Measurements show good agreement with the simulations.

Circularly Polarized Waveguide Antenna With Dual Pairs of Radiation Slots at Ka-Band

In this letter, a circularly polarized (CP) waveguide antenna with dual pairs of slots is presented for Ka-band applications. Circular polarization is realized by combining two orthogonal linear polarizations, which are generated by two pairs of radiation slots on a cavity surface, respectively. Two approaches of radiation slots, i.e., edge slots and corner slots, are discussed. The corner slots approach is employed to design a CP waveguide antenna at Ka-band. The measured axial ratio (AR) is below 3 dB from 29.69 to 30.06 GHz, or 1.2% relative bandwidth, with a minimal value of 0.4 dB at 29.9 GHz. The measured antenna gain is 9.8 dBi at 30 GHz, and the return loss is below –13 dB within the 3 dB AR bandwidth. The all-metal structure of the proposed antenna is very appropriate for tough environment applications.

Millimeter - Wave Elliptical Lens Antenna for Fan - Beam Monopulse Applications

A novel two-dimensional elliptical lens monopulse antenna at millimeter-wave frequencies is presented using the technique of dielectric-fllled parallel plates where TE10 mode propagates. A cavity-backed aperture-coupled elliptical patch antenna array with sum/difierence ports is located at the back of the elliptical lens as the feed antenna. The lens antenna is designed, fabricated and tested at 35GHz. Measurements show that clean and symmetrical fan-beam patterns are realized for both the sum and the difierence beams. The measured 3-dB E- and H-plane beamwidths of the sum pattern are 5:3 - and 37 - , respectively. A gain of 16.7dBi is realized for the sum beam (86% radiation e-ciency), while a deep null of i32:4dB is achieved for the difierence beam. In addition, a 10-dB impedance bandwidth of 7.1% is measured for both the sum and difierence beams.

Design on elliptical lens monopulse antenna

Monopulse antennas can be used for accurate and rapid angle estimation in radar systems [1]. This paper presents a new kind of monopulse antenna base on two-dimensional elliptical lens. As an example, a patch-fed elliptical lens antenna is designed at 35 GHz. Simulations show the designed lens antenna exhibits clean and symmetrical patterns on both sum and difference ports. A very deep null is achieved in the difference pattern because of the circuit symmetry.