This paper presents a novel breast model system based on a UWB antenna for locating a tumor cancer. The antenna with overall size of 35 mm×20 mm×1.6 mm is characterized with an ultra-wideband of 120% and frequency range of 3 GHz-12 GHz for the FCC band. The proposed antenna exhibits good impedance matching, high gain and omnidirectional radiation patterns. The measurment results are presented to illustrate the performances of the proposed antenna. This antenna has been implemented in a designed system model with dielectric properties of a human breast capable to detect strange objects. The size and localization coordinates of the tumor are studied in detail for better tumor detection. The coordinates of the corresponding maximum value of SAR are identified in order to accurately detect different locations of tumor inside the breast. The results show that the localization of the tumor can be detected with high precision which demonstrates the performance of the proposed antenna and the entire system. The proposed breast model system was developed using the commercial CST Microwave studio simulator.

In this paper, a low-profile wide bandwidth circularly polarized microstrip antenna is proposed as element for a C-band airborne circularly polarized synthetic aperture radar sensor. Several bandwidth improvement techniques were proposed and implemented. In order to increase impedance bandwidth, the antenna is constructed using double-stacked substrate with low dielectric constant, modified radiating shape for multi-resonant frequency, and a circle-slotted parasitic patch. Generation of the circularly polarized wave employs a simple square patch with curve corner-truncation as radiating element. The asymmetric position of the feeding is attempted to improve the axial-ratio bandwidth. To avoid a complicated feed network, the antenna is fed by single-feed proximity-coupled microstrip line. The effect of copper-covering on the upper layer for decrease undesired radiation wave emitted by the feeding is also studied and presented. Measurement results show that the impedance bandwidth and axial ratio bandwidth are 20.9% (1,100 MHz) and 4.7% (250 MHz), respectively. Meanwhile the measured gain is 7 dBic at the frequency of 5.3 GHz.

A compact size and wide stopband microstrip quadruplexer with a common crossed resonator is proposed in this paper. The resonator mentioned is theoretically analyzed and proved to be able to resonance at three different frequencies, which can be easily modified by changing the length of the corresponding stub of the resonator. This tri-mode resonator is proved to have the capacity of being shared by three different bandpass filters in a quadruplexer in this paper. Then an additional channel is designed to be coupled to the other side of the feed line of the common input port. Compared to conventional ones, the proposed quadruplexer has a more compact structure, cause no extra matching network is needed, and the number of resonators is reduced effectively. Moreover, a wide stopband is obtained by making the resonators work at the same fundamental frequencies but different higher order frequencies. Besides, open circuit stubs are also used to suppress the harmonic frequencies. To demonstrate the design procedure, a quadruplexer with a third order Chebyshev response in each channel is fabricated and measured. The measured result is in good agreement with the simulated one, showing an attenuation of 20 dB up to 10.16 times of the first channel frequency.

A new super compact ultra-wideband (UWB) bandpass filter (BPF) with triple-notched bands is presented in this paper. Firstly, a new square ring quad-mode resonator (SRQMR) is employed to obtain the initial UWB BPF. Then, a triple-mode stepped impedance resonator (SIR) is inserted into the initial UWB BPF to achieve three desired notched bands. The proposed triple-mode SIR is found to have the advantages of introducing triple-notched bands and provide a higher degree of freedom to adjust the resonant frequencies. To validate the design concept, a new super compact UWB BPF with triple-notched bands respectively centered at frequencies of 3.7 GHz, 5.2 GHz and 7.8 GHz is designed and measured. The predicted results are compared with measured data, and good agreement is reported.

This paper presents a study and analysis of a high performance microstrip branch-line 3dB hybrid coupler (BLHC) operating at 2.2 GHz for Long Term Evolution (LTE) application. High and low impedance meander lines are used to miniaturize the conventional Branch Line Hybrid Coupler. A prototype of the proposed coupler is fabricated and tested using a Rohde and Schwarz ZVB 20 vector network analyzer. The measured results agree well with the simulated ones.

A low-profile triple-band, dual-mode and dual-polarization antenna is proposed in this paper. An annular interdigital slot etched on the top conductor layer of the antenna is employed as a radiator. Through adjusting the location of coaxial probe, three operating modes TM₁₁, TM₀₂, and TM₁₂ of the antenna are excited simultaneously. Two patch-like radiation patterns and one monopolar radiation pattern at three different frequencies are obtained. In addition, circularly polarized (CP) property for TM₁₁ and TM₁₂ modes is achieved by employing a 45° inclined rectangular slot at the center of the antenna. To validate the properties, a prototype is fabricated and measured. The results illustrate that this antenna is attractive in wireless communication systems for its simple structure and multifunction.

In this paper, the effects of magnetization patterns on the performance of series hybrid excitation synchronous machines (SHESMs) are investigated. SHESMs have three magnetic field sources: armature winding currents, permanent magnets and auxiliary winding current. To initiate the investigation, the magnetic field distributions produced by these three sources are obtained. Using the magnetic field distributions, the machine is analyzed under no-load and on-load conditions. Furthermore, the operational indices, such as inductance, torque, and unbalance magnetic force, are calculated. Various magnetization patterns are considered to investigate their influences on the performance of the machine.

A high return loss (-30 dB), small size (100 mm²) and broad bandwidth (1.5 GHz) microwave bandpass filter has been designed using finite element modelling and developed using the superconducting YBa₂Cu₃O₇-δ (YBCO) thin films deposited on a (10 × 10 mm²) LaAlO₃ substrate by spin coating. The thin films have been prepared by electrospinning and solid-state techniques. The microwave properties of filter circuits were experimentally determined using the vector network analyser (VNA) at room temperature (300 K) and in the presence of liquid nitrogen (77 K). The solid-state filter showed high return loss (i.e. -22 dB) at operating frequency of 9.7 GHz and broad bandwidth of 1.5 GHz, which is consistent with the simulation results. The insertion losses for YBCO filters are ~-2, ~-1.5 and ~-3 dB for the normal, nanoparticle and nanorod respectively. However, the electrospun filters exhibited lower performance due to the nano-structural properties of YBCO samples at nanoscale which make these sample have a large band gap compared to solid-state sample. The results indicate that the filter design and simulation result are reliable. Hence, HTS YBCO could be a potential microwave bandpass filter in industry.

This paper proposes a novel planar direction-of-arrival (DOA) estimation antenna. The estimation capability of phase monopulse DOA estimation antennas is enhanced by integrating an RF multiplier that detects the phase relation between the sum and difference of the two received signals. So the proposed antenna provides a wide range of estimation whereas the conventional monopulse DOA estimation antennas determine the angles of half space. A prototype antenna has been fabricated, and the proposed concept was successfully confirmed.

Resonance frequency of a Circular Microstrip Antenna (CMSA) depends on its diameter. Hence when CMSA is truncated or sectored into smaller elements, keeping the diameter same, it resonates at almost the same frequency. An analysis of the new antenna arrays designed using these truncated non-identical CMSA elements, to realize an amplitude distribution over pedestals leading to a desired first side lobe level (FSLL) has been presented. Truncated elements are designed as non-identical elements based on their gain variation with respect to the standard normalized aperture distribution coefficients. Experimental verification to validate the proposed concept and simulated results has been carried out using an antenna array with eight non-identical elements. There is good agreement between simulated and measured results at 1.76 GHz.

Antenna miniaturization, which is a requirement of modern wireless communication systems, is usually concomitant with the reduction of impedance bandwidth. On the other hand, small antennas should also possess stable radiation patterns across a broad frequency band, such as in UWB systems. In this paper, we propose a UWB antenna structure with a novel feeding system composed of an open cavity resonator. It has a wide relative bandwidth (of about 120%) particularly at the lower frequency limits. The variation of radiation pattern across its operating bandwidth is also negligible. The proposed antenna with the novel feed system is smaller and has a wider frequency bandwidth than other available UWB antennas in the literature. Furthermore, another antenna is proposed, which has a feeding system composed of a surface integrated resonator cavity, fabricated on a two-layer microstrip structure. It has achieved better miniaturization and bandwidth, albeit somewhat lower gain. Three prototype models of the proposed antennas are fabricated and measured, of which the frequency response is in excellent agreement with computer simulation results.

In this paper, the analysis and design of a compact Multiple Split Ring Resonator (MSRR) inspired microstrip rectangular patch antenna is presented. The MSRR is used with four rings. The size of the antenna is 25 × 31 × 1.6 mm³ realized on a low cost FR4 substrate. The proposed rectangular microstrip patch antenna operates at the resonant frequency of 5.88 GHz prior to MSRR inclusion. The antenna characteristics are studied before and after inclusion of metamaterial. After including MSRRs at appropriate places, the proposed MSRR antenna induces a new resonant frequency of 2.78 GHz. In addition to rectangular patch's fundamental resonance, the additional resonance is obtained at 2.78 GHz, thus, exhibits dual bands. Hence, MSRR loading antenna attains a bandwidth of 197 MHz at 2.78 GHz and 703 MHz at 5.88 GHz. The prototype of the proposed antenna is fabricated and measured. Simulated results are verified with the measured ones. This proposed antenna can be effectively utilized for WLAN and RF-ID applications. Parametric studies are illustrated to yield the desired frequency bands. Equivalent circuit model analysis of the MSRR loading is determined. Band characteristics of split ring structure are used to determine the negative permeability characteristics.

The frequency response characteristics of a basic microstrip lowpass filter improved using H-shaped defected ground structures are presented. The proposed defected ground structures behave as a resonant element at high frequency and thus eliminate the stopband frequencies to achieve wide stopband rejection. The 3 dB cutoff frequency of the filter is 1.935 GHz. Due to the defects etched in the ground plane of the basic structure, the harmonic rejection is improved from 5th to 10th order along with low insertion loss and voltage standing wave ratio together with good selectivity. The compact filter has a size of 0.0338λ_g², with λ_g = 85.18 mm being the guided wavelength at cutoff frequency. The characteristics of the lowpass filter are verified through simulation and measurement. Consistent and stable results are obtained.

Studies have been reported in the literature on High Frequency (HF) radio channels in mid-latitude areas more frequently than in low-latitude areas. Ionosphere as a reflector of HF radio waves in low-latitude areas might behave differently from that in mid-latitude. This paper reports a statistical model of sky wave HF channel complex impulse response and its parameters, such as channel gain, path gain, phase shift, and delay spread statistics, derived from both simulation and measurement of a 3044 km link in Indonesia. From the evaluations it can be concluded that the multipaths observed with respect to their propagation delays form multiple clusters corresponding to their propagation modes. The channel gain is found to follow Rayleigh distribution, whereas the rms and maximum delay spread exhibit Rayleigh and Gaussian distributions, respectively. This model can be used in performance evaluation of digital communication schemes in low-latitude HF channels.

In this paper a miniaturized dual wideband bandpass filter is designed by the modified extended composite right/left-handed transmission line (ECRLH-TL) under balanced conditions in each right/left-hand passbands. A novel equivalent circuit is proposed to provide the design and an implementation of ECRLH unit-cell by means of the complementary, split ring resonator (CSRR) on the ground plane. Since CSRR is utilized as an alternative to implementing one of the resonators of ECRLH unit-cell, the size and complexity of the structure can be consequently reduced. An example of a dual band pass filter with 3 dB frequency bands from 3.2 to 4.8 GHz and from 6 to 7 GHz is investigated. There is a good agreement among circuit, electromagnetic simulations and measured results in both passbands. The measured insertion loss is better than 0.5 and 1 dB in first and second bands central frequency, respectively. The group delay which is an important factor in wideband communications is about 0.62 ns and 0.71 ns, respectively, in the first and second band central frequencies. The final dimensions of the miniaturized filter are reduced to 8.88 mm X 8.18 mm.

A broadband end-fire antenna loaded with magneto-electro-dielectric metamaterial (MED-MTM) is presented in this paper. Based on a planar printed structure, many periodic structures are investigated in antenna design. The metal patch is embedded with a C-shaped complementary split-ring resonator (CSRR) array, and many cross slots are etched on the ground plane. The zeroth-order resonance (ZOR) and first-order resonance (FOR) can be excited. As a result of electromagnetic coupling effect, the C-shaped patch and ground plane compose metamaterial transmission line (MTL). For potential applications, the broadband and end-fire antenna can work with a 53.5% (3.81-6.59 GHz) impedance bandwidth. The proposed antenna achieves size reduction, gain improvement and bandwidth enhancement.

In this study, the scattering map of the breast is reconstructed by applying the matching-pursuit algorithm (MPA) to the simulation data obtained by the monostatic inverse synthetic aperture radar (ISAR) principle, and the locations of the tumors are determined by considering the peaks on the scattering map. The MPA iteratively searches the true solution by assuming every discrete point in the solution space to be a scattering center by dividing the imaging region onto a discrete grid. In order to obtain images with better resolution, the fine granularity of the grid for accurate solutions is provided at the expense of increased processing times. First, our approach based on MPA is tested on simulated data generated by MATLAB for breast tumor detection and imaging. Perfect reconstruction for the locations of the hypothetical breast tumor points is attained. Then, a full-wave electromagnetic simulation software named CST Microwave Studio (CST MWS) is used to generate backscattered electric field data from a constructed scenario in which a tumor is located in a breast model. Next, we use the collected data from the defined scenarios as an input to our algorithm. Resultant images provide successful detection and imaging of the tumor region within the breast model. The accuracy of the MATLAB and the CST MWS simulation results demonstrate the availability of our MPA-based focusing algorithm to be used effectively in medical imaging.

A passband filter where the central frequency can be one of seven selectable frequencies is presented. Its operation region ranges from 325 to 455 MHz, and each bandwidth is about 20 MHz. The filter is based on a highly miniaturized ring resonator with a size reduction from about 77% to 83% compared to a conventional closed ring. The reconfiguration of its resonant frequency is implemented by shifting a short location, thus changing its effective inductance. This is opposed to the conventional capacitance change of other reconfigurable filters. Simulated and experimental results are in good agreement. Reflections are below -10 dB at central bandpass frequencies for all selectable bands.

In this paper, a multi-carrier nonlinear frequency modulation system based on pseudo-random frequency offset is designed. The reduction of the main lobe 3\,dB width and the side-lobe peaks cannot be realized simultaneously in conventional beamforming schemes, especially when the number of array elements remains unchanged. The proposed system can reduce the main-lobe 3 dB width and suppressing the side-lobe peaks simultaneously. This is done by adjusting the number of sub-signals, frequency offset coefficient and the inter-element spacing. Then, through time slot processing, signal power is focused on different targets. Numerical simulation experiments are implemented to validate the theoretical analysis of the proposed methodology, and comparisons with other techniques are made.

In this paper, a CPW-fed compact metamaterial-inspired monopole antenna is proposed for Industrial, Scientific and Medical radio band (ISM, 2.4-2.483 GHz). The proposed antenna consists of a T-shaped patch and a set of split ring resonators (SRRs). The miniaturization is attained after loading SRRs in proximity to the T-shaped radiator, which makes the antenna structure electrically small. The measured fractional bandwidth of the antenna is 4% (2.42-2.52 GHz), and its size is 0.22λ_o× 0.098λ_o×0.013λ_o. In addition, the electrically equivalent circuit of the proposed antenna is modeled, and the resonant frequency is calculated by using an analytical approach. Also, the permeability plot of SRRs is extracted using Nicolson Ross weir method. The measured peak gain and radiation efficiency of the antenna are obtained as 1.76 dBi and 78.5%. The simulated results and measured results are found in a good agreement.