Muaad Hussein

A Miniaturized Low-Profile Multilayer Frequency-Selective Surface Insensitive to Surrounding Dielectric Materials

In most applications, a frequency-selective surface (FSS) needs to be attached to a wide variety of dielectric materials. The performance of a traditional FSS is greatly influenced by the dielectric material to which it is attached. In this paper, a novel multilayer structure is proposed to construct an FSS. The performance of the proposed structure is shown to be very stable when it is attached directly to a wide variety of dielectric materials of arbitrary thickness. Both single- and dual-polarized structures are designed. The shape of the FSS element is designed by using stepped-impedance transmission lines. A new methodology is proposed to design the FSS by maximizing the value of the capacitance between adjacent layers. The proposed structure offers three distinctive advantages. First, the strong cross-layer capacitance makes the FSS element very compact. The dimensions of the miniaturized element are as small as

Frequency Selective Surface Structure Miniaturization Using Interconnected Array Elements on Orthogonal Layers

0.012 \lambda \times 0.012 \lambda

A Low-profile Miniaturized Second-Order Bandpass Frequency Selective Surface

. Second, for the proposed structure, the lower the profile, the stronger the cross-layer capacitance, and the lower the resonant frequency. This is unique to the proposed structure since the resonant frequency is usually higher for a lower profile for traditional structures. Third and most importantly, any external dielectric material attached to the FSS will not significantly affect the performance of the FSS due to this strong cross-layer capacitance. Through examples of a single-polarized bandpass FSS at 1 GHz and a dual-polarized bandpass FSS at 1.96 GHz, it is demonstrated that a stable resonant frequency under various incident angles up to 75° can be achieved.

Label-type 3D RFID tag mountable on metallic and non-metallic objects

Traditionally, the element of a frequency selective surface (FSS) is rotationally symmetrical and the element arrays in a multilayer FSS are aligned with each other. A new approach to miniaturize the size of the FSS array element is proposed in this paper by interconnecting the array elements only in one direction in a two-layer FSS structure. One layer acts as an enhanced inductor while the other layer provides capacitance. The interconnection between the adjacent array elements changes the equivalent circuit and produces a strong cross-layer capacitance, which lowers the resonant frequency significantly. The dimensions of the miniaturized FSS element are much smaller than the wavelength at the resonant frequency (periodicity

A miniaturized frequency selective surface by using vias to connect spiral lines and square patches

\ll \lambda )

A multi-band high selectivity frequency selective surface for ka-band applications

. The element can also have a low profile since the cross-layer capacitance is stronger with a thinner substrate. The sensitivity to the incident angle of the proposed structure is comparable with traditional ones. A theoretical equivalent circuit model is developed to characterize the structure, based on the analysis of the geometrical configuration of the FSS structure and the electric field distribution on it. The theory was verified by the experimental results.

Low-profile second-order terahertz bandpass frequency selective surface with sharp transitions

High-order bandpass frequency selective surfaces (FSSs) (N ≥ 1) can achieve high performance with a flat in-band frequency response and fast roll-off. One particular practical issue of designing bandpass FSSs using resonant surfaces is that the thickness of the substrate would be around a quarter of a wavelength. On the other hand, the size of a nonresonant FSS array element is usually large. A new miniaturized FSS capable of exhibiting a second-order bandpass response is proposed in this letter. Two miniaturized resonant surfaces coupled by a nonresonant inductive layer are used to build the proposed FSSs. An FSS operating at around 3.8 GHz is designed to verify the method. The element size is smaller than

Millimeter wave cross-coupled bandpass filter based on groove gap waveguide technology

0.076\lambda\,\times \,0.076\lambda

A UHF RFID Tag With Improved Performance on Liquid Bottles

for the proposed structure. This is significantly smaller than the element size of second-order FSSs designed using conventional approaches. The overall thickness is less than λ/24, where λ is the free-space wavelength at the resonant frequency. The method could be particularly useful for the design of FSSs at lower frequencies with longer wavelengths.

Feasibility Study of Using the Housing Cases of Implantable Devices as Antennas

A study for reducing the sensitivity of label-type UHF RFID tags to background materials is done in this paper. It is found that the capacitance in parallel to the feeding point of the tag is the most sensitive element in the circuit. The capacitance of the antenna body is also found to be an important element. The bigger antenna capacitance leads to less sensitive tag designs. Based on these findings a low profile and low cost label-type tag design is proposed. The feeding point is protected by a bottom conducting layer in a 3D design and the dipole antenna is loaded with large capacitive patches at both tips. The tag not only shows acceptable reading range on various dielectric materials but also is capable of working on challenging materials like liquid bottles and metallic objects.