Xi-Cheng Zhu

Design of a Bandwidth-Enhanced Polarization Rotating Frequency Selective Surface

An approach for the bandwidth enhancement of a polarization rotating frequency selective surface (FSS) based on the substrate integrated waveguide (SIW) technology is proposed in this communication. Compared with the previously reported polarization rotating FSS, the passband bandwidth of the proposed FSS is enhanced from 4.6% to 7.2% by introducing a triple-mode SIW cavity resonator as the periodic element. Meanwhile, better frequency response selectivity of filtering performance is achieved. The proposed FSS is made up of a periodic array of the novel triple-mode SIW cavity resonators with two orthogonal slots on the front and back surfaces for polarization rotation. The triple-mode SIW cavity resonator is achieved by placing a metallic via at the center of a dual-mode SIW cavity resonator. Bandwidth enhancement of the FSS is achieved by simultaneously exciting and properly merging together these three modes in the SIW cavity resonator. A prototype designed at Ka-band was fabricated and measured. Good agreement between the measurement and simulation results has been achieved.

A Planar Bandpass Filter Implemented With a Hybrid Structure of Substrate Integrated Waveguide and Coplanar Waveguide

In this paper, a novel planar bandpass filter is proposed, designed, and implemented with a hybrid structure of substrate integrated waveguide (SIW) and coplanar waveguide (CPW), which has the advantages of good passband and stopband performance inherited from SIW and miniaturized size accompanying with the CPW. Additional design flexibility is introduced by the hybrid structure for efficiently controlling the mixed electric and magnetic coupling, and then planar bandpass filters with controllable transmission zeros and quasi-elliptic response can be achieved. Several prototypes with single and dual SIW cavities are fabricated. The measured results verified the performance of the proposed planar bandpass filters, such as low passband insertion loss, sharp roll-off characteristics at transition band, etc.

A Novel Reflective Surface With Polarization Rotation Characteristic

A reflective surface with polarization rotation property is proposed in this letter. The primary function of the surface is to reflect the linearly polarized incident wave with 90° polarization rotation. The fractional bandwidth reaches up to 9.5%, with copolarization reflection coefficient better than -10 dB at normal incidence. Stable frequency responses in the passband have been obtained with oblique incidence for TE polarization. The periodic element of the proposed surface consists of a dual-mode substrate integrated waveguide (SIW) cavity resonator with horizontal and vertical slots on the same side. A parametric study of its frequency responses has been done with full-wave simulation. To verify the design method, a prototype designed at 35 GHz is fabricated and measured. The measured results are in good agreement with the numerical simulations.

Accurate Characterization of Attenuation Constants of Substrate Integrated Waveguide Using Resonator Method

A novel resonator method is presented to extract the attenuation constants of the substrate integrated waveguide (SIW) transmission lines, providing an alternative way to investigate the propagation properties of SIW. The losses of SIW transmission line and cavity resonator have been investigated with theoretical analysis. Then a formula is derived for establishing the relationship between the attenuation constant of the SIW transmission line and the unloaded Q-factor of SIW cavity resonator at its resonant frequency. Thus, the attenuation constant of SIW transmission line can be extracted using SIW cavity resonator. Good agreement between the resonator method and Thru-Line (TL) method has been achieved in both full-wave simulation and experimental results. Besides, good robustness of the resonator method has been demonstrated, suggesting it is a promising technique for investigation of the propagation properties of SIW.

Extraction of Dielectric and Rough Conductor Loss of Printed Circuit Board Using Differential Method at Microwave Frequencies

A differential measurement technique for extracting the complex permittivity of substrate material and the effective conductivity of rough conductor surface is proposed in this paper. In this method, substrate integrated waveguide (SIW) cavity resonators having the same footprints and varied thicknesses are utilized to separate the conductor loss of the top and bottom surfaces of SIW cavity resonators. The extraction of effective conductivity from the surfaces of SIW cavities is done through examining the difference of unloaded Q-factors between the SIW cavity resonators with varied thicknesses. In advance of getting knowledge of the dielectric loss of substrate material, the conductor loss contributed by the metallic via array must be characterized. The separation between the conductor loss of metallic via array and dielectric loss of substrate material is done through the analysis and comparison of unloaded Q-factors between the SIW cavity resonators with the same length but different widths. In order to verify the proposed method, complex permittivity of a commercial substrate is measured with this method at microwave frequencies. The extracted dielectric properties of substrate material are generally consistent with that provided by the manufacturer.

A Retrodirective Antenna Array With Polarization Rotation Property

A planar passive retrodirective antenna (RDA) array with polarization rotation property is proposed in this paper using the substrate integrated waveguide (SIW) technology, which can be used in monostatic radar applications. The proposed RDA array adopts planar bandwidth-enhanced SIW cavity-backed wide slot antennas as the radiation elements. The polarization rotation property can be achieved by using radiation elements in two different configurations. A W-band prototype RDA array with 16 radiation elements is designed and fabricated using the single-layer printed circuit board (PCB) process at 79 GHz for automotive short-range radar applications. The measurement setup for monostatic and bistatic radar cross section (RCS) responses as well as the calibration process are presented. The retrodirective property and the polarization rotation property are realized by the proposed RDA array. The simulated and measured results of monostatic and bistatic RCS responses are in good agreement, which can cover an incident angle of ±17° from bore-sight with its normalized monostatic RCS response dropped by about 3 dB.

Characterization of substrate material using complementary split ring resonators at terahertz frequencies

This paper presents an approach of characterization of substrate material using complementary split ring resonator (CSRR). Frequency selective surfaces made from CSRR are excited with free space radiation. The dielectric properties of substrate material can be extracted from resonant frequencies and transmission loss at resonant frequencies. In order to verify the proposed method, the complex permittivity of Silicon substrate is measured from 110GHz to 180GHz by using backward-wave oscillator (BWO) spectrometers. And the measurement results show that the dielectric properties of Silicon substrate remain almost the same as that provided by semiconductor foundry at microwave frequencies.

Characterization of substrate anisotropy using substrate integrated waveguide technology

This paper presents an analysis of characterization of substrate material using substrate integrated waveguide (SIW) technology. The advantage of characterization of dielectric anisotropy using SIW technology is that the electric field of SIW exists only along the vertical direction (normal to the substrate surface). Then the permittivity measurement sensitivity of substrate material of SIW methods are compared with other planar-circuit methods, i.e., the stripline and coplanar waveguide (CPW) methods.

Efficient two dimensional direction finding via auxiliary-variable manifold separation technique for arbitrary array structure

A polynomial rooting Direction of Arrival (DOA) algorithm for multiple plane waves incident on an arbitrary array structure that combines the multipolynomial resultants and matrix computations is presented in this paper. Firstly, a new auxiliary-variable manifold separation technique (AV-MST) is proposed to modal the steering vector of arbitrary array structure as the product of a sampling matrix (dependent only on the array structure) and two Vandermonde-structured wavefield coefficient vectors (dependent on the wavefield). Then the propagator operator is calculated and used to form a system of bivariate polynomial equations. Finally, the automatically paired azimuth and elevation estimates are derived by polynomial rooting. The presented algorithm employs the concept of auxiliary-variable manifold separation technique which requires no sector by sector array interpolation and thus does not suffer from any mapping errors. In addition, the new algorithm does not need any eigenvalue decomposition of the covariance matrix and exhausted search over the two dimensional parameter space. Moreover, the algorithm gives automatically paired estimates, thus avoiding the complex pairing procedure. Therefore, the proposed algorithm shows low computational complexity and high robustness performance. Simulation results are shown to validate the effectiveness of the proposed method.

Efficient Two-Dimensional Direction Finding via Auxiliary-Variable Manifold Separation Technique for Arbitrary Array Structure

A polynomial rooting Direction of Arrival (DOA) algorithm for multiple plane waves incident on an arbitrary array structure that combines the multipolynomial resultants and matrix computations is presented in this paper. Firstly, a new auxiliary-variable manifold separation technique (AV-MST) is proposed to modal the steering vector of arbitrary array structure as the product of a sampling matrix (dependent only on the array structure) and two Vandermonde-structured wavefield coefficient vectors (dependent on the wavefield). Then the propagator operator is calculated and used to form a system of bivariate polynomial equations. Finally, the automatically paired azimuth and elevation estimates are derived by polynomial rooting. The presented algorithm employs the concept of auxiliary-variable manifold separation technique which requires no sector by sector array interpolation and thus does not suffer from any mapping errors. In addition, the new algorithm does not need any eigenvalue decomposition of the covariance matrix and exhausted search over the two dimensional parameter space. Moreover, the algorithm gives automatically paired estimates, thus avoiding the complex pairing procedure. Therefore, the proposed algorithm shows low computational complexity and high robustness performance. Simulation results are shown to validate the effectiveness of the proposed method.