Showing papers by "Yi Wang published in 2015"

Multimode Resonator-Fed Dual-Polarized Antenna Array With Enhanced Bandwidth and Selectivity

Abstract: A novel design concept of multimode filtering antenna, which is realized by integrating a multimode resonator and an antenna, has been applied to the design of dual-polarized antenna arrays for achieving a compact size and high performance in terms of broad bandwidth, high-frequency selectivity and out-of-band rejection. To verify the concept, a $2 \times 2$ array at C-band is designed and fabricated. The stub-loaded resonator (SLR) is employed as the feed of the antenna. The resonant characteristics of SLR and patch as well as the coupling between them are presented. The method of designing the integrated resonator-patch module is explained. This integrated design not only removes the need for separated filters and traditional ${50}{\text - }{\Omega }$ interfaces but also improves the frequency response of the module. A comparison with the traditional patch array has been made, showing that the proposed design has a more compact size, wider bandwidth, better frequency selectivity, and out-of-band rejection. Such low-profile light weight broadband dual-polarized arrays are useful for space-borne synthetic aperture radar (SAR) and wireless communication applications. The simulated and measured results agree well, demonstrating a good performance in terms of impedance bandwidth, frequency selectivity, isolation, radiation pattern, and antenna gain.

Integrated filtering-antenna with controllable frequency bandwidth

Abstract: An integrated design of a band-pass filter and a patch antenna is proposed in this paper by using an aperture coupled structure. Traditionally, the microwave filter and antenna are designed separately using 50 Ohm interface and then connected by transmission lines, which lead to a large size and more loss. Here, the antenna and microwave filter are directly integrated without a 50 Ohm interface between them. Compared with the traditional cascade designing, the co-design of filter and antenna has a more compact size, simpler configuration, improved frequency selectivity and higher system efficiency. The frequency bandwidth also can be controlled by adjusting the dimension of the coupling aperture in the ground. The measured results agree very well with the simulations, showing the filtering-antenna has good performance in impedance matching, radiation pattern and antenna gain.

Investigation of SU8 as a structural material for fabricating passive millimeter-wave and terahertz components

Abstract: This paper provides a systematic review of the technical issues of SU8 fabrication for millimeter-wave and terahertz components based on research carried out at the University of Birmingham in the past decade. A design-for-manufacturability approach is followed. The flexibility of the SU8 process enables many device structures. Challenges and problems during fabrication will be discussed and demonstrated with examples. The measurement of the devices is also a significant challenge when the critical dimensions of the device shrink and special testing fixtures are needed in some cases. Finally, a brief overview of the issues discussed above is given for future guidance.

Four-way waveguide power dividers with integrated filtering function

Abstract: A novel power divider with filtering function has been proposed in this work. A coupled-resonator structure is utilized to realise the dual functions. This eliminates the need for conventional transmission-line based splitting networks. The corresponding coupling matrix has been synthesised. A four-way filtering power divider was designed with an equal power division at X-band using rectangular waveguide cavities. A return loss of 20 dB and a bandwidth of 500 MHz with a fourth-order Chebyshev filtering response were demonstrated. The design has been verified by measurements, which show good agreements with simulations.

Bandpass Filters with Mixed Hairpin and Patch Resonators

Abstract: This paper presents a new implementation technique of transmission zeros in an in-line coupled filter. Neither cross couplings between non-adjacent resonators nor separate side-line resonators have been used. Instead a mixture of single-mode hairpin resonators and dual-mode patch resonators have been adopted in a bandpass filter with one asymmetric transmission zero. The introduction of the patch led to an improved frequency selectivity through an independently controllable transmission zero. This approach has been verified by a three-pole filter at 2.6 GHz with 8% bandwidth and a transmission zero at 2.4 GHz. Good agreement has been shown between the measurements and the simulation.

Micromachined 3D millimeter-wave and terahertz devices

Abstract: Micromachining is a very promising technology to manufacture miniature three-dimensional (3D) devices at millimeter-wave (mm-wave) and terahertz (THz) frequencies. After a decade's development, this technology has begun to demonstrate its viability and capability. It has delivered devices with competitive performance to traditional metal machining or electroforming, for coaxial and waveguide structures with sub-millimeter dimensions. This paper will discuss three strands of work that tackle three main challenges — fabrications, designs and measurements — in this technology. Several passive devices will be presented to illustrate the progress made on the multilayered SU8 techniques. These include guided transmission structures and devices based on rectangular coaxial lines, waveguides and free-space frequency selective surfaces. The concerned frequency covers from 30 GHz to 1 THz.

Enhancing the selectivity of frequency selective surfaces for terahertz sensing applications

Abstract: This paper introduces a new technique for enhancing the selectivity (or the quality factor, Q-factor) of frequency selective surfaces (FSS) for sensing applications. The proposed FSS functions as a free-space bandpass resonator, designed to sense the changing dielectric properties of minute amount of materials loaded on the FSS. The Q-enhancement technique is mainly based on two concepts; enhancing the field concentration in a given area and introducing transmission zeros in the FSS response. Two designs based on a modified complementary split-ring resonator (CSRR) at 300 GHz have been proposed. The first one is composed of complementary triple-split ring resonators. The splits divided the structure into arcs of different lengths. As a result, the transmission zero is obtained in the passband due to a destructive coupling. This produces a resonance Q-factor of 41. By controlling the orientation of the three splits, higher Q-factor of 84 is attainable. The second structure is designed using concentric triple-split rings. The added electromagnetic coupling between the concentric rings makes the transmission response steeper as compared with the single triple-split ring, and the quality factor increases from 41 to 90. By reducing the interspacing distance by three times, the Q-factor can be further increased to 256. The parameter studies of the FSS structures based on full-wave simulations have been presented.