This paper investigates the channel characterization of Rayleigh fading channel using K-band frequency-modulated continuous wave (FMCW) radar system. An IF (intermediate frequency) signal of K-band FMCW radar can be treated as time and frequency domain signals due to a unique property of linear frequency modulation (LFM). First, channel sounder FMCW radar stability has been confirmed by measuring power flatness of transmitted radio frequency signal and estimated range in anechoic chamber before conducting the experiment for channel characterization of Rayleigh fading channel. Next, the measurement setup has been conducted in reverberation chamber which emulates multipath fading phenomena. In reverberation chamber, four different cases have been examined by changing the boundary conditions inside it with and without flat microwave absorbers. This investigation leads to obtained scattered plots, normalized propagation delay profiles (PDPs), mean excess delay, root-mean-square (RMS) delay spread and envelope distribution of Rayleigh fading channel at about 24.591 GHz.

The cardinalized probability hypothesis density (CPHD) filter is a powerful tool for multitarget tracking (MTT). However, conventional CPHD filter discriminates targets from clutter only via the motion information, which is not reasonable in the situation of dense clutter. In the tracking, the amplitude of target returns is usually stronger than those coming from clutter, so the amplitude information can be used to enhance the discrimination between targets and clutter. Based on this idea, this paper proposes an amplitude-aided CPHD filter for the MTT in distant infrared (IR) surveillance. First, we model the amplitude of targets and clutter in IR scenarios respectively. For distant IR scenarios, the point spread function (PSF) is used to model the imaging of the point target. The center intensity of the PSF is unknown in practice, and the maximum likelihood estimation (MLE) method is adopted to estimate the target center intensity via the intensities of the latest target detections. Then a likelihood function for MTT is established, and using this likelihood function, a new CPHD recursion is derived, which can distinguish different targets and clutter by the correspondence weight. In the implementation, we adopt the Gaussian mixture (GM) approach to implement the amplitude-aided CPHD filter to achieve efficient performance. In numerical experiments, the results show that the proposed method attains a significant improvement in performance over that only using location measurements.

In this letter, a novel broadband single-layer reflectarray element composed of a circular patch and double circular ring is presented. The element in the reflectarray provides a nearly 360° linear phase range and has rebirth capability. The broadband characteristic of this reflectarray is obtained due to the sub-wavelength of the element space and the combination of two resonators of complementary size on a single layer. Then, a prime-focus 225-element microstrip reflectarray with this phoenix cell has been designed and implemented. The measured gain is 22 dBi with 1 dB drop within 29% bandwidth at the center frequency of 10 GHz.

In this paper, a compact asymmetric coplanar strip (ACS)-fed printed monopole dual-band antenna for 2.4 GHz bluetooth, 5.2/5.8 GHz wireless local area network (WLAN) and 3.5/5.5 GHz worldwide interoperability for microwave access (WiMAX) applications is presented and investigated experimentally. The proposed antenna is composed of a ACS-fed monopole, an arc-shaped strip and an omega-shaped strip, which occupies a compact size of 18 x 22 mm² including the ground plane. By properly selecting the positions and lengths of these strips, dual frequency operation with wide impedance bandwidth characterstics can be achieved. The proposed antenna has been validated experimentally and found to have nearly onmidirectional raiation patterns in the H-plane, nearly bi-directional behaviour in the E-plane and accepatable peak gain across operating bands.

Original resonant structures for improving efficiency of wireless charging system with the possibility of data exchange are presented. Characteristics of two different dual-mode spiral resonators were obtained by electromagnetic and circuit simulations. Based on these results, an optimum design for highly efficient data and energy transfer was suggested.

This paper presents a new hybridization between MoM-GEC and some asymptotic methods. In fact, a new hybrid current test function based on Physical Optic (PO) and a modal method is developed. The approach consists in approximating the total current on an invariant metallic pattern on two parts. The inside of metal is governed by PO method; however, the edges are modeled by infinite cylinders and described by Hankel functions (modal method). The considered single test function is required then by MoM method to replace a lot of sinusoidal or triangular test functions, in order to get a rapid convergence and less computational time. For validation purposes, the new developed hybrid approach is applied to compute scattering in different structures. The obtained input impedances, currents and fields distributions are in agreement with those obtained by MoM method. Considerable gain in computational time and memory resources is achieved.

A multiband four-antenna system with high isolation for the mobile phone applications is presented in this paper. The four antennas consisting of a main antenna and three auxiliary antennas are located on a 135×65×0.8 mm³ FR4 epoxy board. The main antenna is an improved monopole antenna which can cover LTE700/2300/2500, GSM850/900/1800/1900/UMTS, and 2.4-GHz WLAN bands. Three identical auxiliary antennas with a size of 40×6×0.8 mm³ are located vertically in the sides and bottom of the circuit board, respectively. By adopting three slots in each radiating patch of the auxiliary antennas, they can successfully cover 704-746 MHz and 1880-2690 MHz band with S₁₁ less than -6 dB. The isolation among the four antennas is better than 13 dB. The measured efficiency of the main antenna in the operation band can reach 40%, and the efficiency of auxiliary antennas can reach 25% at upper frequency band and about 10%-20% at 704-746 MHz band.

Encoding a large number of bits within a narrow band is an important factor in the development of chipless RFID tags. A novel 8 bit chipless RFID tag with a limited bandwidth of 650 MHz is proposed here. The proposed tag comprises a multi-resonating circuit with eight E-shaped microstrip resonators in the frequency band of 3.12 to 3.77 GHz and two cross-polarized transmitting and receiving monopole antennas. The unique feature of the proposed tag is that a different set of frequencies can be derived by changing a single parameter of the structure. The prototype of the tag is fabricated on a substrate C-MET LK4.3 of dielectric constant 4.3 and loss tangent 0.0018. Different tag combinations are designed and tested using bistatic measurement setup. Measurement results on realized prototypes are provided to ensure the reliability of the proposed design.

This letter presents a compact triple-band passband filter with high frequency selectivity. The first and second passbands are formed by a multi-stub loaded resonator. The width of the second passband can be independently adjusted by tuning the coupling strength between the two loaded open stubs. The third passband is implemented using two asymmetrical stepped impedance resonators (SIRs) with a tapped line structure as external coupling form. The asymmetrical SIRs also serve as one part of the external coupling structure of the multi-stub resonator so as to achieve a compact circuit size. Additionally, a source-load coupling is introduced, thus, multiple transmission zeros are generated to improve the frequency selectivity. After a detailed introduction of the operation principle, a triple-band passband filter with centre passband frequencies of 1.5, 2.6 and 3.6 GHz is designed and fabricated. The measured results verify the effectiveness of the proposed filter.

In this paper, a penta-band antenna design using matching network for mobile phone application is proposed. This design is composed of a planar inverted-F antenna (PIFA) and a LC-tank-stacked network. The LC-tank-stacked network consists of two pairs of stacked chip-LC tank, which is parallel with the microstrip line feeding to the antenna. The PIFA works for generating dual bands, and each pair of chip-LC tanks can effectively enhance the lower band and upper band, respectively. According to measured results, the bandwidth can cover 824-960 MHz/1710-2170 MHz band for WWAN application for VSWR = 3:1. The peak antenna gain is better than 0.5 dBi and 3.4 dBi for lower and higher operation band, respectively. And the measured radiation efficiency is about 40-60% and 40-70% lower and higher operation band, respectively.

In this paper, a novel compact tri-band bandpass filter (BPF) with compact circuit size and high passband selectivity has been presented and implemented using multipath-embedded resonator (MER). This filter includes two multipath-embedded stepped impedance resonators (SIRs), connected with stub-coupling at the symmetric plane. By tuning admittance ratio and length ratio of the multipath-embedded resonator, it can be designed at 1.84, 2.45, 3.05 GHz. Through internal edge-coupling and extemal zero-degree feed lines, a tri-band BPF can be achieved with compact circuit size, high passband selectivity and low insertion loss. The measured results validate the full-wave EM simulated results with good agreement.

A hybrid optimization method that synthesizes coupling matrices for cross-coupled microwave filters is presented. This method consists of a general solvopt algorithm and fmincon algorithm, respectively. To avoid divergence from the coupling matrix, two cost functions are built, where the first one is constructed from the eigenvalues of the coupling matrix and its principal sub-matrices, while another one is dependent on the determinant of the coupling matrix and one of its cofactors. The values of non-zero elements of the coupling matrix serve as the independent variables to minimize the cost functions by using solvopt and fmincon. Although the stochastic initial values are not sufficiently close to the global optimum, the hybrid optimization procedure is still robust to find multiple coupling matrices to overcome the initial problem. It is significant that the suitable coupling matrix can be chosen from the multiple solutions to meet the given requirements in practice. For demonstrating the proposed hybrid optimization algorithm, some extraordinary prototype topologies are provided which validate the efficiency of the proposed synthesis procedure.

In this paper, we propose to realize ultra-wide-band absorber (UWBA) based on anomalous refraction/reflection of phase gradient metasurfaces(PGM). To achieve high absorption and meanwhile keep small thickness at low frequencies, PGM is incorporated into conventional magnetic materials (MM). The absorptivity is increased due to prolonged propagation length in the MM, which is produced via anomalous refraction/reflection mediated by the PGM. Three typical composite configurations of PGM-based absorbers are investigated and an UWBA design method is finally formulated. Due to small thickness and ultra-wide bandwidth, such absorbers possess great application potentials in EM protection, RCS reduction, etc.

In this paper, an efficient mode reduction technique for eigenmode expansion method is developed to analyze 2-D waveguide grating structures which are a special class of piecewise uniform waveguides. To take advantage of the periodicity property of the structure, the eigenmode expansion method (EEM) is used with the scattering matrix method and a recursive-doubling procedure. In this situation, our proposed mode reduction technique achieves a significant speedup for gratings with large number of periods. Comprehensive numerical examples on the waveguide gratings are studied to validate the efficiency of our proposed mode reduction technique.

This paper introduces a new method for the design and realization of two monopulse antennas with circular polarization and unique phase center for two different frequency bands. The design uses compact sequential-rotation serially fed 2×2 patch array for each section of the monopulse antenna for X band at 8.2 GHz and a patch for S band at 2.25 GHz. The patches are placed on one layer, and the monopulse network and feeds are placed on different layers. The antennas use sequential rotation serial feeds with four and three probes for X band and S band, respectively. Also, the packaging and coupling effects are considered and compensated for this design. Finally, the antenna with a compact multi-layer structure is fabricated, and the simulation results are validated. The bandwidth of X band monopulse antenna system is at least 12.7% in simulation and 10% in fabrication, and it is about 10.2% and 10.3% for S band in simulation and fabrication, respectively. While the phase centers of both frequency bands are approximately at one point, the antenna system can be employed as a feed for reflectors.

This paper describes a monopole antenna with dual-band switchable circular polarization (CP) sense in WLAN and WiMAX bands. The proposed antenna consists of a rectangular patch fed by a microstrip line and a ground plane embedded with a T-shaped slot integrated with PIN diodes. The slotted ground is capable of exciting CP sense around 2.45 GHz for WLAN and around 3.4 GHz for WiMAX, respectively. Two triangular strips are added to improve impedance matching. The CP sense of the proposed antenna can be reconfigured between the right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP) by switching the states of PIN diodes in the slot. The lower band 3-dB axial ratio (AR) bandwidth is 8.6%, and the upper band 3-dB AR bandwidth is 20.8%, in which the return loss is less than -10-dB. Simulated analysis and measured results are carried out and good agreement is achieved.

A novel broadband circularly polarized slot antenna with a rotated slot for bandwidth enhancement is proposed. The antenna has a simple structure, consisting of a microstrip feed line, a substrate, and a rotated rectangular slot with two branches etched on the plane. By appropriately adding the rotated rectangular slot and two branches on the ground-plane, the impedance bandwidth of the antenna is enlarged, and its wide axial-ratio (AR) bandwidth is achieved. Experimental results show the proposed antenna has good right-hand circular polarization (RHCP) characteristics. The measured -10-dB return loss impedance bandwidth and 3 dB axial-ratio bandwidth are 38.8% (1.5 GHz~2.2 GHz) and 25.6% (1.56 GHz~2.02 GHz) at the center frequency of 1.8 GHz.

This work presents experimental investigations of three-dimensional (3-D) far-field holographic microwave imaging (HMI) method for diagnosing inclusions within dielectric objects, and in particular, it relates to electromagnetic imaging to reconstruct dielectric properties of inhomogeneous, lossy bodies with arbitrary shape. The apparatus is designed for operation at a single frequency of 12.6 GHz. 16 antennas are located on a 2-D array plane which is placed under the object in the far-field region, with air in the space between the antenna array and the object. Experimental results indicate that the 3-D HMI system has the ability to produce a 3-D image of multimedia dielectric object and detect small inclusions embedded within an object. The invention has potential application to tissue imaging.

The aim of this work is to miniaturize a microstrip patch antenna resonating at 3 GHz. For this purpose, defected ground structure (DGS) has been employed to shift the resonance frequency of an initial microstrip antenna from 5.7 GHz to 3 GHz by disturbing the antenna's current distribution. The proposed DGS is incorporated in the ground plane under the patch antenna to improve its performances. Finally, a miniaturization up to 50%, with respect to the conventional microstrip antenna, is successfully accomplished. A prototype of the antenna was fabricated with the FR4 substrate and tested. The measurements results were in good agreement with simulation results.

A 12-element triangular-grid rectangular radial line helical array antenna is proposed and investigated. The major characteristic of this antenna is that its radiation elements are arranged in triangular-grid, which is helpful to reducing the number of elements demanded for a certain antenna aperture and grating lobe suppression capacity. The radiation element is optimized to facilitate the manufacture. The feed system with six different groups of output ports is designed to obtain equal-amplitude output using three kinds of probes. An antenna prototype with the center frequency of 2.856 GHz is simulated and measured. In the range of 2.75-2.95 GHz, the experimental result shows an antenna VSWR below 1.2, an antenna gain over 16.3 dB, and an aperture efficiency more than 80%. The field distributions of this antenna are analyzed through simulation, which prove its advantage of high power-handling capacity. Its ability to be used as a sub-array is also demonstrated by forming a 48-element array antenna.