A compact wideband bandpass filter (BPF) based on half-mode substrate integrated waveguide (HMSIW) is proposed in this paper. The proposed BPF is achieved by etching a couple of S-shaped complementary spiral resonators (S-CSRs) on the top layer of HMSIW cavity to achieve a wide passband as well as generate two transmission zeros in the vicinity of the passband respectively to improve the selectivity. In addition, compared with a conventional CSRs-loaded HMSIW structure, the proposed S-CSRs-loaded HMSIW makes the overall size of the filter largely reduced with the same electrical length. Among the HMSIW structures ever reported, the proposed S-CSRs are the first time to be introduced into HMSIW. To validate its practicability, a compact wideband HMSIW BPF loaded with S-SCRs has been designed and implemented through the PCB process. The measured and simulated S-parameters of the filter are presented to show the proposed filter's predicted performance, and good agreements is obtained between them. This result demonstrates that the newly proposed HMSIW structure loaded with S-CSRs is an excellent candidate for compact filters.

A simplified design of substrate integrated waveguide (SIW) is proposed here. The requirement of side walls using via which is quite cumbersome in the manufacturing process is eliminated in this structure. The design is based on producing an imaginary electric boundary by exciting the SIW using differential feed. It behaves as a pair of half mode substrate integrated waveguides (HMSIWs) sharing a common electric boundary. The new structure gives similar characteristics of the conventional SIW in terms of cutoff frequency, stopband rejection and operating bandwidth.

When a narrow straight slot is etched obliquely in the upper metallic strip of a microstrip line, a bandstop response can be observed from the terminations of the microstrip line. The whole circuit behaves as a single-stage bandstop filter, of which the center operation frequency and the fractional bandwidth can be adjusted by changing the length and the inclined angle of the slot, almost independently. Parametric studies are made to demonstrate the filtering performance, via numerical simulations. An LC equivalent circuit model is given to explain the bandstop behavior, shows its potential use in high order filter design. Samples are designed, fabricated and measured for verification, the experiment results show that the filters have good bandstop performance. It can be used as an alternative or complementary candidate for the traditional spur-line bandstop filter.

In this work, we report a novel phase change material: Hf-doped VO2(M1) with negligible thermal hysteresis width for low-power silicon photonic reconfigurable device applications. As dopant concentration rises from 0% to 3%, the material maintains the metal-insulator transition (MIT) property of VO2(M1) thin films, and the thermal hysteresis width significantly narrows from 7 ºC to <1 ºC, leading to a good control of material electrical and optical constants as a function of temperature. A ring resonator with Hf-doped VO2(M1) material partly deposited on the ring has been fabricated. Temperature dependent transmission spectrum of the device has been tested, which shows resonant peak shift due to the phase transition of Hf doped VO2(M1). Doping Hf makes this material become a promising candidate for a variety of silicon integrated reconfigurable photonic devices.

Traditionally, the direction of arrival (DOA) estimation usually employs homogeneous antenna arrays consisting of many identical antennas. This paper proposes a new technique of DOA estimation by using a heterogeneous array which has many elements with each element pointing to a different direction from others. A general expression of the manifold for planar heterogeneous array is derived. Then, a polarized MUSIC (Pol-MUSIC) method for unknown polarizations is proposed. One advantage of this Pol-MUSIC method is that it can obtain the DOA of signals with any unknown polarizations while no search of the polarizations is required. The proposed method is verified by simulation, and its performance is analyzed. The heterogeneous array is a polarization-sensitive array though it has one channel at each point of spatial sampling. This provides favorable conditions for simplifying the systems.

In order to effectively improve the communication quality in the extremely-low frequency (ELF) communication, an integrated model of the analog circuit combined with the multi-channel array algorithm is constructed, and a highly sensitive magnetic sensor is designed. An array algorithm based on generalized singular value decomposition is proposed to find the optimal filter coefficient, and then to achieve the purpose of suppressing interference in ELF communication. In the manufacture of magnetic antenna, the method of partitioned windings divided by acrylic effectively reduces the distributed capacitance of the magnetic antenna, and the rational design of the amplification filter circuit lays the foundation for the interference suppression in the next step. Specific process of the proposed algorithm is deduced. The corresponding evaluation indices are given, and the correlation among evaluation indice is expounded. The simulated and experimental results are discussed respectively. The experimental setups are designed and presented. The results show that no matter which the simulated signal or the experimental data is, the proposed algorithm can effectively suppress the interference, and the output signal to interference ratio is increased by 30 dB.

A new microstrip ultra-wideband (UWB) bandpass filter (BPF) with quad notched bands using quad-mode stepped impedance resonator (QMSIR) is investigated in this paper. The resonance properties of the QMSIR are studied. Then, quad notched bands inside the UWB passband are implemented by coupling the proposed QMSIR to the main transmission line of a basic microstrip UWB BPF. The quad notched bands can be easily generated and set at any desired frequencies by varying the design parameters of QMSIR. For verification, a new microstrip UWB BPF with quad notched bands respectively centered at frequencies of 5.2 GHz, 5.8 GHz, 6.8 GHz and 8.0 GHz is designed and fabricated. Both simulated and experimental results are provided with good agreement.

In this study, a varactor-loaded slotted ground structure is investigated and utilized to construct a new tunable common-mode (CM) suppression filter for differential signals. A four-port distributed equivalent circuit model is developed for interpreting the working mechanism of CM signal suppression. It is found that the proposed simple structure is capable of tunable CM suppression with a wide frequency tuning range. The parameter selection and design principle are also given. Finally, the design theory is well vindicated by a common-mode filter using three periodic varactorloaded slots. Simulated and measured results, showing good agreement, exhibit a tuning range from 0.80 to 2.10 GHz, corresponding to the fractional tuning range of 89.7% and more than 30 dB CM rejection level.

A wideband circularly polarized antenna with wide half power beamwidth (HPBW) and 3 dB axial-ratio beamwidth (ARBW) is proposed in this paper. The circularly polarized (CP) radiation is realized by feeding two crossed printed dipoles through a wideband feeding network with broadband 90º phase shift. By adding a thick substrate layer and a notched-corner metal cavity around the antenna, the impedance bandwidth (VSWR < 2) is greatly enhanced. The HPBW of the proposed antenna are greater than 110º while the ARBW are greater than 130º in the operating band, simultaneously. The overall dimension of the antenna is only 70×70×36 mm³. The measured results show that the impedance bandwidth of the proposed antenna reaches 54.7% (1.06 GHz-1.86 GHz) while the AR bandwidth (AR<3 dB) is 48.6% (1.08 GHz-1.78 GHz). As such, the proposed antenna can be widely used in various global navigation satellite system (GNSS) applications.

General design guidelines for unidirectional electrically small parasitic array has been proposed by several researchers; however, the input resistance of these antennas is normally very low. In order to practically ``transfer'' this high directivity into realized gain, an appropriate matching mechanism is necessary. This paper gives a simple matching method by adding an inductive stub close to the antenna feed, which can effectively increase the antenna input impedance to 50 Ω and keep the gain almost invariant. Besides, it could make the resonant frequency very close to the frequency where maximum gain occurs, thus a high realized gain can be achieved. Computed and measured examples are given to validate this method.

This paper presents a narrow-band bandpass filter (NBBPF) using three cylindrical dielectric resonators (CDRs) placed on three rectangular metallic cavities (RMCs). Two U-shaped planar resonators located between RMCs are used to realize narrow-band response effectively. The 3 dB fractional bandwidth (FBW) of the proposed filter is 0.275%. The filter is designed for X-band (9.85 GHz), with 20 MHz bandwidth for radar, satellite, and medical accelerators applications. High Q-factor (Q-factor = 400) and low fabrication cost are other advantages of the proposed design. The proposed NBBPF was fabricated, and its performance was measured to verify the design. Good agreement between the measured and simulated data is obtained.

In this paper, a novel broadband circular polarized (CP) antenna for mobile communication is proposed. The antenna is constructed as a square ring with a gap and coplanar waveguide (CPW) feed. To achieve a broadband CP wave, a cross patch is embedded at the center of the slotted square ring to excite two orthogonal resonant modes with equal amplitude and 90° phase difference for CP radiation. Furthermore, on one side of ground a stub is embedded to match impedance bandwidth that can cover the whole CP bandwidth completely. Loading the AMC (Artificial magnetic conductor) structure on the back of the antenna achieves unidirectional radiation of circular polarized waves. An antenna was fabricated based on simulation and optimization. The simulated and measured results show that the bandwidth with S₁₁<-10 dB is 66.9% from 1.82 GHz to 3.65 GHz, and the 3 dB axial ratio bandwidth is 52.8% from 1.95 GHz~3.35 GHz.

The electromagnetic characteristics of a high speed IC power distribution network (PDN) are of vital important with the rapid increasing of operation speed and scale down CMOS manufacturing size, in particular, the fundamental electromagnetic theory including impedance and loop inductance of various designed IC power-plane structures. In addition, the area occupancy ratio of slot (AOROS) of irregular parallel-plane structures with multi-slots plays a key role in PDN impedance and loop inductance, where the influence of AOROS on impedance and loop inductance is investigated for various structures. Moreover, experimental work is carried out to validate the influence of AOROS on impedance and loop inductance of the PDN. The simulation and measurement of impedance are performed up to 10 GHz, and a good agreement is obtained between the simulation and experiment.

This paper proposes a novel clip-shaped meander-line resonator (CSMLR) to realize miniaturized ultra-narrowband (UNB) bandpass filter design. The main advantage is that it can achieve very weak coupling between adjacent resonators with keeping them very close and introduce transmission zeros (TZs). To further demonstrate the feasibility of using this configuration, a six-pole UNB filter with a fractional bandwidth (FWB) of 0.20% at the center frequency of 1915 MHz was designed on double-sided YBCO high temperature superconducting (HTS) thin films with a thickness of 0.5 mm and dielectric constant of 9.8 by using CSMLR. The measured responses agree rather well with the simulated ones. The measured results show a maximum insertion loss of 0.31 dB and return loss of 15.5 dB in the passband. Two transmission zeroes (TZs) are generated to improve the passband selectivity, which causes the band-edge steepness better than 50 dB/MHz in both transition bands.

Developed initially for military applications, radar technology is rapidly spreading to areas as diverse as natural resource monitoring, civil infrastructure assessment, and homeland security. Waveform design is a critical component to extract maximum information about the targets or features being probed. Waveforms derived from noiselets, one of the family functions of wavelets, can be advantageous in certain applications owing to their random and uncorrelated properties. In this work, radio frequency (RF) noiselet waveforms are introduced and their performance related to detection of arbitrary target interfaces using the cross-correlation method, a form of matched filtering, is assessed. The application of the RF noiselet waveform for nondestructive testing (NDT) of the multilayered dielectric structures is discussed. The application of wideband noiselet waveforms for multiresolution analysis (MRA) is demonstrated.

In this paper design of a stacked circular patch antenna is presented for high gain and wideband applications. The main radiator of this design is a circular patch antenna, which is fed by using a coupling mechanism. Wide impedance bandwidth of 40% and linear polarization of gain 9.5 dBi at the center frequency of 2.4 GHz is measured. The antenna gain is further increased by using regular period of N circular patch directors on top of the main radiator. The first director is placed in a distance of about one half of the wavelength and the next directors are placed with regular distances of about a quarter of the wavelength. The antenna gain is tuned and increased with the number of the directors in the range of 9.5-16.5 dBi with N up to seventeen. The antenna impedance change due to the added directors is adjusted by using two parasitic circular patches between the main radiator and the first director. A prototype antenna is designed, manufactured and measured. The antenna operation can be further extended using dual feed geometry in which we can obtain two orthogonal radiation patterns or circular polarizations.

A design of a half-mode substrate integrated waveguide (HMSIW) cavity-backed self-diplexing antenna is proposed with a two-layer structure. The top layer comprises two HMSIW based cavities, and radiating patches are etched on the top-cladding of each cavity. The radiating patches are excited by two distinct printed microstrip lines on the backside of the bottom layer by using shorting-pins. The shorting-pin excites the corresponding cavity in its dominant mode, which resonates at two different frequencies in X-band. The simulated results demonstrate that the proposed design resonates at 8.20 GHz and 10.55 GHz with an isolation of higher than -25 dB between two excitations, which helps to introduce the self-diplexing phenomenon. Also, both resonant frequencies can be tuned independently by varying the dimensions of the corresponding cavity. Moreover, HMSIW cavity-backed structure and proposed feeding technique reduce the overall size of the antenna significantly, while it maintains high gain and unidirectional radiation characteristics for both operating frequencies.

The Meissner effect is studied by using an approach based on Newton and Maxwell's equations. The objective is to assess the relevance of London's equation and shed light on the connection between the Meissner and skin effects. The properties of a superconducting cylinder, cooled in a magnetic field, are accounted for within the same framework. The radial Hall effect is predicted. The energy, associated with the Meissner effect, is calculated and compared with the binding energy of the superconducting phase with respect to the normal one.

This paper presents an imaging radar system for structural health monitoring (SHM) of wind turbine blades. The imaging radar system developed here is based on two frequency modulated continuous wave (FMCW) radar sensors with a high output power of 30 dBm. They have been developed for the frequency bands of 24,05 GHz-24,25 GHz and 33.4 GHz-36.0 GHz, respectively. Following the successful proof of damage detection and localization in laboratory conditions, we present here the installation of the sensor system at the tower of a 2 MW wind energy plant at 95 m above ground. The realization of the SHM-system will be introduced including the sensor system, the data acquisition framework and the signal processing procedures. We have achieved an imaging of the rotor blades using inverse synthetic aperture radar techniques under changing environmental and operational condition. On top of that, it was demonstrated that the front wall and back wall radar echo can be extracted from the measured signals demonstrating the full penetration of wind turbine blades during operation.

This work presents an enhanced rectenna with a differential source feeding scheme for radio frequency (RF) energy harvesting at 2.45 GHz frequency. A circularly polarized (CP) microstrip antenna with embedded slots is designed which efficiently attains harmonics suppression. By modifying size and position of two diametrically opposite triangular projections in the top patch, two orthogonal modes that have equal magnitude and are in phase quadrature are excited. The four radial slots embedded in the antenna can block 2nd and 3rd harmonics which is suitable for onboard rectenna design without harmonics filter. A microstrip tapered feed line is used to match antenna element with 50-ohm impedance. The designed antenna is then tested for RF energy harvesting in two ways. One is conventional single source fed rectenna (SSFR), and the other is proposed differential source fed rectenna (DSFR). In the DSFR, the designed antennas are differentially operated by making a difference of λg/2 path length (λg Guided wavelength), and the ports are then connected to a differentially driven optimized rectifier circuit. For comparison, an SSFR and a DSFR are fabricated and tested. The circuit parameters in each case are optimized in Agilent Design System (ADS) 2011 software to maximize RF to direct current (DC) conversion efficiency. The proposed DSFR has a maximum efficiency (RF-DC) of 41.63% at 10 dBm RF input power. In the input power range from -20 dBm to 10 dBm, the DSFR has improved performance and higher efficiency over the SSFR.