A substrate integrated waveguide (SIW)-fed circularly polarized (CP) antenna array with a broad bandwidth of axial ratio (AR) is presented for 60-GHz wireless personal area networks (WPAN) applications. The widened AR bandwidth of an antenna element is achieved by positioning a slot-coupled rotated strip above a slot cut onto the broadwall of an SIW. A 4 × 4 antenna array is designed and fabricated using low temperature cofired ceramic (LTCC) technology. A metal-topped via fence is introduced around the strip to reduce the mutual coupling between the elements of the array. The measured results show that the AR bandwidth is more than 7 GHz. A stable boresight gain is greater than 12.5 dBic across the desired bandwidth of 57-64 GHz.

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Axial Ratio Bandwidth Enhancement of 60-GHz Substrate Integrated Waveguide-Fed Circularly Polarized LTCC Antenna Array

Anisotropic impedance surfaces are employed as low-profile and broadband reflectors that convert orthogonal linear to right- and left-handed circular polarization respectively. By virtue of anisotropy, it is possible to independently control the reflection characteristics of two orthogonal linearly polarized incident plane waves and therefore achieve linear to circular polarization conversion. Equivalent circuits for anisotropic impedance surfaces with arbitrarily shaped elements are employed to demonstrate the operating principle and a design procedure is proposed. The proposed design procedure is demonstrated by means of an example involving a dipole array. A prototype is designed and its performance characteristics are evaluated. The 3-dB relative axial ratio bandwidth exceeds 60%, while low loss and angular stability are also reported. Numerical and experimental results on a fabricated prototype are presented to validate the synthesis and the performance.

Anisotropic Impedance Surfaces for Linear to Circular Polarization Conversion

A novel single-fed low-cost wideband and high-gain slotted cavity antenna based on substrate integrated waveguide (SIW) technology using high-order cavity modes is demonstrated in this paper. High-order resonant modes ( ${\text T}{{\text E}_{{130}}}$ , ${\text T}{{\text E}_{{310}}}$ , ${\text T}{{\text E}_{{330}}}$ ) inside the cavity are simply excited by a coaxial probe which is located at the center of the antenna. Energy is coupled out of the cavity by a $3 \times 3$ slot array etched on the top surface of the cavity. Two antennas with different polarizations are designed and tested. Measured results show that the linearly polarized prototype achieves an impedance bandwidth $\left(\vert{{\text S}_{{\text 11}}}\vert of $> {26}\% $ (28 to 36.6 GHz), and a 1-dB gain bandwidth of 14.1% (30.3 to 34.9 GHz). In addition, a measured maximum gain of 13.8 dBi and radiation efficiency of 92% are obtained. To generate circularly polarized radiation, a rotated dipole array is placed in front of the proposed linearly polarized antenna. Measured results show that the circularly polarized antenna exhibits a common bandwidth (10-dB return loss bandwidth, 3-dB axial ratio bandwidth, and 1-dB gain bandwidth) of 11%.

Low-Cost Wideband and High-Gain Slotted Cavity Antenna Using High-Order Modes for Millimeter-Wave Application

A 95-GHz printed low-loss linear-to-circular polarizer is designed as a component of an active direct-detection millimeter-wave imaging system. The periodic printed grid structure presents different reactances to the TE and TM polarizations, resulting in equal amplitude and phase quadrature upon transmission through four parallel grids. The polarizer is measured in both a Gaussian beam system and a plane wave system, and demonstrates an axial ratio of 0.23 dB, polarization isolation of 38 dB, and transmission loss of 0.3 dB for normal incidence. The quarter-wave plate is characterized up to plusmn35deg off the optical axis, and exhibits an axial ratio better than 1 dB up to plusmn17deg off the optical axis.

A W -Band Polarization Converter and Isolator

A high-gain low-profile circularly polarized substrate integrated waveguide cavity antenna is proposed using TE 440 high-order mode. This antenna is simply excited by a coaxial probe. A linear-to-circular convertor is used in order to achieve circular polarization (CP). The low-profile, lightweight antenna offers both left- and right-hand CP. The implemented antenna exhibits a measured gain of almost 16 dBi and simulated radiation efficiency of about 96% with good measured return loss. Measured axial ratio is almost less than 1.6 dB. Furthermore, the antenna shows a good performance radiation pattern. Measured and simulated results show a good agreement. This antenna is considered as an appropriate candidate for use in future fifth-generation wireless systems.

High-Gain Low-Profile Circularly Polarized Slotted SIW Cavity Antenna for MMW Applications

A single-layer linear-to-circular polarisation converter is proposed for an application to a slotted waveguide planar array. It consists of dipoles which closely couple to slot arrays. The method of moments clarifies the mutual coupling between the dipoles and the slots on the waveguide. Numerical results promise the use of a uniform and parallel dipole array as a single-layer linear-to-circular polarisation converter for an existing linearly polarised slotted waveguide array. The measurements using a linearly polarised slotted waveguide array in 22.0 GHz band confirm the prediction; the axial ratio less than 1 dB and a negligible insertion loss is realised.

M. Ando

Papers

Single-layer dipole array for linear-to-circular polarisation conversion of slotted waveguide array