A new compensation method for the mutual coupling of adaptive antenna arrays composed of wire elements is introduced. For the antenna array composed of wire elements, the new compensation method can decouple the terminal voltages with high accuracy for both the 1-D incident signals and 2-D incident signals. The new compensation method is based on the mutual coupling grid and the transient mutual coupling coefficient proposed in this paper. By contrast with the CMIM and RMIM, the new compensation method can provide better compensation for the DOA estimations. Even for the ultra compact antenna array and the incident signals inclined with respect to the azimuth the new compensation method can work well. The numerical results verify the validity and the effectiveness of the new compensation method.

A novel compact ultrawideband (UWB) CPW-fed antenna with triple lower pass bands and dual notched bands for wireless applications is presented. The low-profile antenna comprises of an approximate hexagonal-shaped radiator for covering the UWB band (3.1~10.8 GHz). Triple lower pass bands, the 1.5G band, 1.8 GHz GSM band and 2.4 GHz Bluetooth band, can be realized by adding three handstand semielliptical-shaped stubs bilaterally at the upper part of antenna ground. A notched band of 3.3~3.7 GHz for rejection of WIMAX radio signals can also be obtained by adjusting the geometry of the three stubs. In addition, an U-shaped slot on the radiating patch generates a notched band in 5.15~5.825 GHz for rejection of WLAN radio signals. The proposed antenna is designed and built on a FR-4 substrate, with overall size of 25 mm×24 mm. The simulated and measured results are presented and show that the proposed compact antenna has a stable and omnidirectional radiation patterns across all the relevant bands.

Geosynchronous synthetic aperture radar (GEO SAR) has the characteristics of long aperture time and large imaging area. Therefore, the conventional imaging algorithm in Low Earth Orbit (LEO) SAR loses effect. In this paper, based on curved trajectory model under an ideal acquisition and not considering some acquisition perturbations (atmosphere, orbital deviations), an accurate two-dimensional frequency spectrum is analytically obtained via series reversion principle and high order Taylor expansion. Then, an improved Nonlinear Chirp Scaling (NCS) algorithm is proposed in GEO SAR, which includes novel range migration correction factor, coupling phase compensation factor, NCS factor and azimuth compression function. Finally, the correctness of the proposed NCS algorithm is verified via imaging results of point array targets and area targets.

An original target identification method using Wave-Coefficients (WCs) as feature vector is proposed. The scattering fields of arbitrary shaped targets are expressed as a sum of spherical waves and the distinctive coefficients are exploited as the target feature. Decision rule based on correlation coefficient is established, and some analyses on the properties of the WCs are conducted. Numerical simulations of four targets are carried out and the recognition performances without and with noise are provided and discussed.

This paper proposes a microwave filter post-production tuning based on an optimization process which finds the vector of deviations of tuning elements that should be applied to tune the filter. To build the system, the coarse set of scattering parameters is collected in such a way that every tuning element is detuned while other elements remain in their proper positions. In the concept, it is assumed that the relation between the positions of tuning elements and filter scattering characteristics can be modelled by the sum of one argument polynomial functions. Each polynomial function depends on the value of only one tuning element. Therefore, the measured filter characteristics can be linearly decomposed to characteristics from the collected coarse set and corresponding tuning element deviations can be found. This is done by way of optimization process. The presented numerical and physical experiments on the 7th order cross-coupled, bandpass filter have verified our approach.

Two new compact planar triple-mode resonators embedded with inductive or capacitive cross coupling are proposed for bandpass filter design. Both resonators consist of a shorted half-wave ring. In the first resonator, two shorted half-wave sections with inductive coupling are connected to the shorted via of the ring. In the second, two quarter-wave sections with capacitive coupling are connected. The inductive coupling is realized by a short grounded high-impedance segment, and the capacitive coupling is implemented by an interdigital capacitor. When both the inductive and capacitive coupling coefficients are properly realized, a transmission zero can be created at designated position in either upper or lower stopband. The shorted ring is accommodated inside the area of the other two resonance sections so that a compact area can be achieved. As compared with a conventional dual-mode ring resonator filter, the proposed resonators use only 46.7% and 22.5% in area. Two triple-mode resonator bandpass filters are fabricated and measured to validate the ideas. Measurement results have good agreement with the simulation responses.

The insertion of vertical slabs in a metallic rectangular waveguide distorts the power distribution of the waveguide, producing new modes and modifying the existing ones. The resulting waveguide, known as E-plane loaded rectangular waveguide, is studied in this paper, focusing the attention on the TE-type modes in a symmetrical case. A quasi-TE₁₀ is found which may confine the energy in the central air region by suitably choosing the dielectric slabs' dimensions. An algorithm to optimize these dimensions is proposed in order to maximize the confinement of power in the air region and minimize the attenuation of the mode. This minimization is specially important at high frequencies, where the ohmic losses and the dielectric absorption become extremely high. This paper includes an example at THz frequencies and presents the design of several devices using the E-plane loaded rectangular waveguide.

The Wave Iterative Process is applied and validated for the study of the scattering of a plane wave by a multiple metallic dipole diffraction structure. The case of a single metallic dipole is treated, at first in normal incidence, than arbitrarily placed with respect to the incident wave. A double dipole scattering structure is studied, mutual influence being taken into account. The diffraction system is further enlarged to 5 randomly placed dipoles, the results issued from the WIP study being compared with those given by the Moments Method. Finally, the possibility of taking into account a very large number of dipoles is examined, by introducing an equivalent dipole distribution. The influence of this approximation on the WIP precision is presented.

A simple and effective double-thresholding strategy based on energy estimation is proposed to choose the optimal boundary between the signal subspace and noise subspace in TR-MUSIC algorithm for microwave imaging of extended targets. Simulations and imaging results are given to demonstrate its strong noise rejection and super-resolution capability. In the new method, the shape details of extended targets can be obtained from single frequency or multi-frequency scattering data.

This paper presents a novel design of stacked dual layer strip lines fed patch antenna. The wideband characteristics can be achieved by employing approximate L-probes coupling feeding schemes. Dual layer strip lines which are composed of one broadband 180° hybrid and two wideband 90° hybrids are introduced as feeding network in this design. As a result, the designed antenna has a 59.4% 10-dB input reflection coefficient bandwidth and 48.3% 3-dB axial ratio (AR) bandwidth relative to the center frequency respectively. The designed antenna occupies a compact size of 80 mm×80 mm×32 mm. The final antenna provides a very good circularly polarized radiation for Global Navigation Satellite System applications including GPS, GLONASS, Galileo and Compass.

In this paper, a novel interactive multiple model particle filter (IMMPF) is developed after a Bayesian estimator for maneuvering target tracking in clutter is derived theoretically. In this new algorithm, base state estimation and modal state estimation are completely separated to control the number of particles in each maneuvering mode. Only continuous-valued particles are used to numerically implement the procedure of Bayesian base state estimation, whereas modal state is estimated analytically without dependence on the number of particles. Density mixing is performed by aggregation of the total particles and mixing associated weights. To prevent the exponentially growing number of particles with the time, a resampling step is included following the interaction step. Through MC simulations, the new IMMPF has been tested and shown to provide reliable performance improvements with different sample sizes and under various clutter conditions.

Concrete walls reinforced with rebars have poor shielding effectiveness for telecommunication frequencies (frequencies above 0.5 GHz). An effective method to increase the shielding effectiveness of the walls is to increase the complex permittivity of the concrete. This can be done by mixing in thin filaments of a material with high conductivity. One such material is carbon. In this paper the Maxwell Garnett mixing rule is used to model a concrete material with carbon filaments. The shielding effectiveness computed with the mixing rule is found to agree with previously published measurement results.

We describe the implementations of Drude-critical point model for describing dispersive media into finite difference time domain algorithm using piecewise-linear recursive-convolution and auxiliary differential equation methods. The advantages, accuracy and stability of both implementations are analyzed in detail. Both implementations were applied in studying the transmittance and reflectance of thin metal films, and excellent agreement is observed between analytical and numerical results.

A transformer that uses bonder-wires and printed circuit board (PCB) patterns is proposed for RF circuit applications. The proposed transformer can be constructed without any additional processes. The PCB patterns are implemented using a typical FR4 substrate and gold bonder wires are used. The self-inductance of the transformer can be controlled according to the number of unit-transformers. Although the size of the transformer is larger than that of a fully-integrated transformer, the maximum available gain (MAG) is almost identical to that of other-types of transformers, which require additional cost or bulky size to obtain sufficient inductance. Additionally, we proposed a method to design the transformer with a symmetric structure for differential RF CMOS circuit applications. The transformer can applied to GHz-order RF CMOS circuits as an input and output matching component with low loss characteristics.

A novel S-shaped electromagnetic band gap (EBG) middling bandwidth bandpass filter based on substrate integrated waveguide (SIW) was proposed. The filter was designed based on the band-stop characteristics of EBG by etching different dimensional S-shaped on the surface of substrate integrated waveguide. The bandpass filter with a center frequency at 7.765 GHz and relative fractional bandwidth 7.31% shows good bandpass characteristics with frequency band between 7.38~7.94 GHz, while the insertion loss is less than 1.6 dB and achieve middling bandwidth in SIW by EBG and has the advantage of bandpass, low insertion loss, compacted and good selectivity etc. The good agreement between the measured results and the simulated results demonstrates that the design of this proposed filter is effective.

In this paper, a printed slot antenna fed by a co-planar waveguide for ultra wide bandwidth (UWB) with dual notch bands has been presented and discussed. The band notches are realized by etching one C-slot resonator inside a plaque shape exciting stub as well as symmetrically adding a pair of open-circuit stubs at the edge of the slot resulting in dual stop band filtering properties for WiMAX, WLAN application. Surface current distributions are used to analyze the effects of the slot and open circuit stub. The proposed antenna is fabricated and experimental results show that it has an impedance bandwidth of 2.6-14.34 GHz for VSWR ≤ 2, except dual frequency stop-bands of 3.3-3.7, 5.04-6.0 GHz. From the simulation results, it is observed that the radiation patterns are omnidirectional in the H-plane and dipole like nature in the E-plane. The gain varies from 3.7 dB to 5.7 dB over the whole UWB region excluding at notch bands.

A novel slotted helix slow-wave structure (SWS) is proposed to develop high power, wide-bandwidth, high reliability millimeter-wave traveling-wave tube (TWT). This structure, which can improve the heat dissipation capability of the helix SWS, evolves from conventional helix SWS with three parallel rows of rectangular slots made in the outside of the helix. In this paper, thermal stress analysis, the electromagnetic characteristics and the beam-wave interaction of this structure are investigated. The conclusions of this paper will be a great help for the design of millimeter-wave traveling-wave tube.

This work provides the comparison of different methods for the experimental determination of the phase center location of an antenna. The phase center position is determined by means of measured data obtained with a planar scanning system and computed with different methods: a least squares fit method with and without weighting coefficients and a directivity-based plane wave spectrum (PWS) analysis method. A study of the phase center position for different microwave antennas is provided. The results of the different methods are presented and compared, along with the confidence interval of the phase center values due to the uncertainties of the acquisition system.

This work presents an active balanced sub-harmonic mixer (SHM) using InP double heterojunction bipolar transistor technology (DHBT) for Q-band applications. A miniature spiral type Marchand balun with five added capacitances for improved control of amplitude and phase balance is integrated with the SHM. The measured results for the SHM demonstrates a conversion gain of 1.2 dB at an RF frequency of 41 GHz with an associated LO power of 5 dBm. The conversion loss remains better than 3 dB from 38 to 44 GHz. The LO to IF isolation is better than 42 dB within the bandwidth of the mixer and confirms the excellent balance of the integrated spiral type Marchand balun. The DC power consumption of the SHM is only 22.5 mW under normal mixer operation.

This paper presents an implementation of the FDTD-compatible Green's function on a heterogeneous parallel processing system. The developed implementation simultaneously utilizes computational power of the central processing unit (CPU) and the graphics processing unit (GPU) to the computational tasks best suited to each architecture. Recently, closed-form expression for this discrete Green's function (DGF) was derived, which facilitates its applications in the FDTD simulations of radiation and scattering problems. Unfortunately, implementation of the new DGF formula in software requires a multiple precision arithmetic and may cause long runtimes. Therefore, an acceleration of the DGF computations on a CPU-GPU heterogeneous parallel processing system was developed using the multiple precision arithmetic and the OpenMP and CUDA parallel programming interfaces. The method avoids drawbacks of the CPU- and GPU-only accelerated implementations of the DGF, i.e. long runtime on the CPU and significant overhead of the GPU initialization respectively for long and short lengths of the DGF waveform. As a result, the seven-fold speedup was obtained relative to the reference DGF implementation on a multicore CPU thus applicability of the DGF in FDTD simulations was significantly improved.