Kai Da Xu

Two Memristor SPICE Models and Their Applications in Microwave Devices

This paper presents two simple SPICE circuit models of the memristor using two different kinds of integrators. These models expand and simplify the previous methods of solving the memristors modeling equations presented by Hewlett-Packard Lab. The behaviors of the two memristor models are investigated when they are excited by a sinusoidal voltage source. Both models satisfy the general features of memristive systems such as having a zero-crossing property in the form of an i-v Lissajous figure. In order to explore the unique characteristics and applications of the memristor in microwave devices, first we incorporate the memristor in a microstrip transmission line as a load. We do the analysis using a finite-difference time-domain simulator integrated with a nonlinear SPICE circuit solver. Furthermore, we design a reconfigurable microstrip bandpass filter based on a memristor-loaded resonator, and utilize a memristor as a carrier-wave modulator connecting the microstrip patch antenna to the ground.

Design of a Stub-Loaded Ring-Resonator Slot for Antenna Applications

A T-shaped stub-loaded ring-resonator (SLRR) slot etched on the ground plane or on the radiating patch has been designed and analyzed for antenna applications. Compared with the conventional ring slot, the two resonant frequencies of the proposed SLRR-slot can be lowered, and can also be tunable by varying the parameters of the four T-shaped stubs. To validate the design concept, a tri-band printed antenna and a dual band-notched ultra-wideband (UWB) antenna using the SLRR-slot on the ground plane and radiating patch, respectively, are presented. For the tri-band antenna, a simple U-shaped slot etched on the microstrip feeding line is used to excite a third upper-frequency band independently without increasing the overall size of the antenna and without affecting the lower two bands. The proposed tri-band antenna has three frequency bands of 2.4, 3.5, and 5.8 GHz, and the dual band-notched UWB antenna can guarantee a very wide bandwidth from 3.0 to 12.0 GHz with dual undesired bands successfully. The experimental results including radiation patterns, peak gains and efficiencies of both antennas are presented.

Miniaturized Quint-Band Bandpass Filter Based on Multi-Mode Resonator and

Based on multi-mode resonator (MMR) and λ/4 resonators, a miniaturized microstrip quint-band bandpass filter (BPF) with mixed electric and magnetic coupling (MEMC) has been presented. The proposed MMR is employed to generate the 1st, 2nd, and 5th passbands, while the 3rd and 4th ones of close band proximity are achieved by using four coupled λ/4 uniform impedance resonators (UIRs). Due to MEMC cancelling effect, virtual grounds in feed lines, and source-load cross coupling, multiple transmission zeros (TZs) can be yielded to obtain sharp passband roll-off skirts. To verify the validity of the design approach, a quint-band BPF centering at 2.1, 3.0, 4.0, 4.7, and 7.2 GHz (denoted as f1, f2, f3, f4, and f5) with respective 3 dB fractional bandwidths of 13.7%, 5.6%, 10.5%, 5.1%, and 2.9% has been designed and fabricated, whose measured results show good consistence with the predicted frequency responses.

\lambda/4

A novel compact dual-band cavity-backed substrate integrated waveguide (SIW) array antenna using high-order radiation modes has been proposed in this paper. The first high-order hybrid mode (superposition of TM310 and TM130) and the second high-order mode (TM320) of K-band in the SIW cavity are excited by an inductive window for dual-band application. The operation mechanism of high-order modes is analyzed and then verified through simulations by inserting metallic vias in different positions of the resonant SIW cavity. The designed subarray antenna has the advantages of high gain, high front-to-back ratio, and low cross-polarization level. To further validate the design idea, a dual-frequency band

Resonators With Mixed Electric and Magnetic Coupling

2 \times 2

Substrate Integrated Waveguide Cavity-Backed Slot Array Antenna Using High-Order Radiation Modes for Dual-Band Applications in

array antenna has been fabricated and measured including reflection coefficients, realized gains, and radiation patterns. The measured results show that the 10-dB impedance bandwidths at resonant frequencies of 21 and 26 GHz are 800 MHz (3.7%) and 700 MHz (2.6%), and the realized gains at boresight direction are around 16 and 17.4 dBi, respectively. Moreover, the proposed array antenna also possesses both advantages of metallic cavity-backed antennas and planar patch antennas, such as low cost, easy fabrication with the printed circuit board technology, and integration with other planar circuits.

K

Based on the coupled-line stub-loaded shorted stepped-impedance resonator (CLSLSSIR), a compact microstrip tri-band band-stop filter (TB-BSF) with controllable frequencies, stopband attenuations (SAs), and sharp transition band roll-off skirts has been presented. The proposed CLSLSSIR exhibits multimode resonant behavior and is employed to achieve tri-stopband application by applying the virtual ground effect at the attaching position. Due to the infinite input impedance effect of CLSLSSIR, as well as the resonance of

-Band

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Miniaturized Frequency Controllable Band-Stop Filter Using Coupled-Line Stub-Loaded Shorted SIR for Tri-Band Application

-type network combined with two loaded CLSLSSIRs and transmission line, multiple transmission poles can be yielded to obtain high selectivity of transition band. Finally, an example TB-BSF operating at 1.57, 2.4, and 3.5 GHz with respective SAs of 18, 26.5, and 33.2 dB has been designed and fabricated.

Pattern Synthesis of Unequally Spaced Linear Arrays Including Mutual Coupling Using Iterative FFT via Virtual Active Element Pattern Expansion

A virtual active element pattern (AEP) expansion method is presented in which each AEP in an unequally spaced array is considered to be the pattern radiated by a subarray of some equally spaced virtual elements. With the help of this method, the pattern of an unequally spaced array including mutual coupling can be efficiently evaluated by fast Fourier transform (FFT). By incorporating this idea into the iterative Fourier transform procedure, we develop a novel iterative synthesis method, which can apply the iterative FFT to efficiently synthesize unequally spaced arrays including mutual coupling. Different excitation constraints, such as phase-only control and amplitude-phase optimization with a prescribed dynamic range ratio, can be easily added into the proposed synthesis procedure. A set of synthesis examples for different antenna arrays with pencil and shaped beam patterns are provided to validate the effectiveness and advantages of the proposed method.