Lin-Sheng Wu

A Miniaturized Dual-Band Frequency Selective Surface (FSS) With Closed Loop and Its Complementary Pattern

A single-layer substrate frequency selective surface (FSS) made of miniaturized elements is proposed, with two controllable passbands obtained. Each FSS element consists of a loop wire on the top metal layer and its complementary pattern etched at the bottom one, which provides two transmission poles separated by a transmission zero. An equivalent circuit model is given for predicting the characteristics of the designed FSS, and a good agreement between the simulated and measured transmission coefficients is obtained. Furthermore, the cases of oblique wave incidence and cascading FSSs are also measured and examined.

Evanescent-Mode Substrate Integrated Waveguide (SIW) Filters Implemented with Complementary Split Ring Resonators

A new type of evanescent-mode substrate integrated waveguide (SIW) bandpass fllter is presented in this paper, with complementary split ring resonators (CSRRs) introduced on the top or bottom metal planes of the waveguide. Both positive and negative couplings are obtained between the CSRRs by changing their locations and orientations. In comparison with conventional SIW fllters, the proposed fllters are compact since their passbands are below the cutofi frequency of SIW. A third- and a fourth-order cross-coupled fllter prototypes were designed using standard PCB technology. They operate at the same central frequency of 3.8GHz, with their fractional bandwidths of 15% and 20%. The proposed fllters have a wide upper stopband as the cutofi frequency of TE10-mode in the SIW is much higher than the central frequency. Their good performance is demonstrated by both the simulated and measured S-parameters.

A New Balanced-to-Balanced Power Divider/Combiner

In this paper, a new balanced-to-balanced power divider/combiner is proposed. By using matrix transformation, two three-port networks for the odd- and even-mode circuit models are deduced, based on the constraint rules of the mixed-mode S -parameters. In order to satisfy the two required scattering matrices simultaneously, the resistances of lumped elements, the characteristic impedances and electrical length of transmission lines are selected appropriately. Then, a planar microstrip structure is designed to realize the proposed balanced-to-balanced power divider/combiner with equal power division. The theoretical, simulated and measured results all show a good mixed-mode performance. In the measurement, the maximum differential-mode transmission coefficient is -3.2 dB, the best differential-mode isolation is 47.2 dB, and the fractional bandwidth of its operating band is approximately 20.8%.

Design of a Beam Reconfigurable THz Antenna With Graphene-Based Switchable High-Impedance Surface

In this paper, a new beam reconfigurable antenna is proposed for THz application, which is based on a switchable high-impedance surface (HIS) using a single-layer graphene. The effects of impurity density and gate voltage on the conductivity of graphene are utilized, and the switchable reflection characteristic of the graphene-based HIS is observed. Then the THz antenna is designed over this switchable HIS. By applying different voltages for different rows of HIS units, the antenna beam can be reconfigurable. The performance of the antenna is analyzed with its reflection coefficient, radiation pattern, and input impedance. The radiation beam of the antenna can vary in a range of ±30° as demonstrated by the simulated results.

Novel Substrate Integrated Waveguide Filters With Mixed Cross Coupling (MCC)

A new type of substrate integrated waveguide filter with mixed cross coupling (MCC) is proposed, with its mechanism of generating extra transmission zeros using MCC investigated. Less mixed coupling is needed to obtain the same number of transmission zeros in comparison with inline filters, with good agreements obtained between the measured and the simulated S-parameters of the developed filters.

Compact Substrate Integrated Waveguide (SIW) Bandpass Filter With Complementary Split-Ring Resonators (CSRRs)

A novel cross-coupled bandpass filter using new substrate integrated waveguide (SIW) resonators is presented. The resonator is built up by a SIW cavity loaded with a complementary split-ring resonator (CSRR) on its top metal plane. The resonant modes of the proposed resonator are analyzed, with the Q-factor of the dominant mode also extracted. It is shown that our proposed compact filter operates below the cutoff frequency of conventional SIWs. No spurious responses, corresponding to the higher-order resonant modes of the resonator, appear within an octave band of the central frequency. Its attractive performance is validated numerically and experimentally.

A Substrate-Integrated Evanescent-Mode Waveguide Filter With Nonresonating Node in Low-Temperature Co-Fired Ceramic

A cross-coupled substrate-integrated evanescent-mode waveguide filter is proposed with a quasi-elliptic frequency response. It is realized with a coplanar waveguide as a nonresonating node to provide an equivalent negative coupling coefficient. The filter prototype is developed with folded and ridge substrate-integrated waveguides (SIWs) in low-temperature co-fired ceramic. Since evanescent-mode and cross-coupling techniques are used in the design of filters, about 90% area reduction and more than 60% volume reduction are achieved, in comparison with conventional planar cavity-coupled SIW filters. Their unloaded Q factor is also improved. In particular, the spurious suppression characteristic of the direct-coupled evanescent-mode waveguide filter is kept by the cross-coupled filter with the nonresonating node structure. All these merits are demonstrated numerically, as well as experimentally, with good agreement obtained between the measured and simulated S-parameters.

A New Type of Periodically Loaded Half-Mode Substrate Integrated Waveguide and Its Applications

A new type of half-mode substrate integrated waveguide (SIW) periodically loaded with different lumped elements and structures is proposed in this paper. The propagation constants, Bloch impedances, and voltage distributions of the Floquet TE-modes are all characterized by solving the eigenvalues of the generalized transmission matrix of a single period. Several typical capacitor-loaded, inductor-loaded, corrugated, and electromagnetic-bandgap (EBG)-loaded half-mode SIWs were fabricated to demonstrate their modal dispersion behavior. The measured and simulated S -parameters, group delays, and simulated electric field distributions in these novel structures are presented, with good agreements obtained for all samples. In particular, their unique controllable cutoff frequencies, multiple bandgaps, and separated monomode regions are also illuminated numerically and experimentally. To further show their applications, a tunable phase shifter is developed using a varactor-loaded structure, with its 3-dB bandwidth of 50% and a maximal tunable range of 88°. In addition, a bandpass filter based on EBG-loaded half-mode SIW is also realized and presented with its special characteristics. It demonstrates that the filter has a sharp upper slope side and a good performance of spurious suppression.

An Extended Doublet Substrate Integrated Waveguide (SIW) Bandpass Filter With a Complementary Split Ring Resonator (CSRR)

An ldquoextended doubletrdquo bandpass filter (BPF) is proposed using a substrate integrated waveguide (SIW) cavity with a complementary split ring resonator (CSRR) etched on its top metal plane. Thus, a single-layer BPF with two transmission zeros is realized successfully, with no additional area or layers occupied. The measured and simulated S-parameters of the filter are presented to show its predicted performance, with good agreements obtained between them.

Balanced-to-Balanced Gysel Power Divider With Bandpass Filtering Response

In this paper, the balanced-to-balanced Gysel power divider is proposed with bandpass filtering response for the first time. The component is based on a ring structure and designed with an extended coupled-resonator circuit model. The characteristic impedances, electrical lengths, and isolation resistance are calculated analytically by our derived equations, according to the design specifications of the filtering power divider. The achievable bandwidth is from about 3% to 12%. As an example, a fabricated prototype occupies an area of 0.97 × 0.87 λg2, whose bandwidth is 8.4%. It has low differential-mode in-band insertion loss, good magnitude, and phase balances between two output ports, good isolation, and good suppression of common-mode noises and mode conventions. Based on stub-loaded sections, another prototype is realized for miniaturization, whose occupied area is reduced to 0.67 × 0.63 λg2. In comparison with the original prototype, the central insertion loss is increased by 0.13 dB, and the rejection band of common-mode and mode-conversion noises is narrowed by 21%.