In this paper, we study in detail both the trapped surface wave and lateral wave excited by a dipole antenna parallel to the plane boundaries of a three-layered region in spherical coordinate. An approximate formula is obtained for the solution of the electrictype pole equation when a condition is satisfied by √k²₁-k²₀l≤0.6. Similarly, an approximate formula is obtained for the solution of the magnetic-type pole equation when a condition is satisfied by √ k²₁-k²₀l-π/2≤1. Furthermore, because of its useful applications in microstrip antenna, the radiation patterns of a patch antenna with specific current distributions are treated specifically. Analysis and computations are carried out in several typical cases. It is seen that, for the component E_0Θ, the total field is determined primarily by the trapped surface wave of electric type, and, for the component E_0Φ, the total field is determined primarily by the trapped surface wave of magnetic type.

A microstrip circular patch antenna with two shorting pins is proposed as an antenna with reduced surface wave and lateral wave excitation. Theoretical analysis of the cavity modes of the patch lead to a design procedure for the antenna. Simulation results using the IE3DZeland software support the theory and verify the reduced surface wave capability. By using four shorting pins instead of two, we demonstrate the possibility of achieving circular polarization with high polarization purity in addition to the reduced surface wave. It is demonstrated that a discrimination against the lateral wave of 30dB or more is achievable. Applications include design of large patch arrays with reduced coupling and GPS receiving antennas that reduce low angle interfering signals.

This paper presents the design and construction of a complete near real-time scatterometer system for in-situ measurement. The full polarimetric system is comprised of inexpensive Frequency Modulated Continuous Wave (FMCW) radar that is efficiently constructed from a combination of commercially available components and in-house fabricated circuitry. An automated advanced antenna positioning system (AAPS) is included in the development of the system, giving rise for a more practical measurement. The backscattering matrices of a 4'' × 8'' dihedral corner reflector are rotated and measured at different angles to provide different sets of polarimetric data. The backscattering matrices of 8'' sphere, 12'' sphere and 16.5'' trihedral are also measured and the results are presented in this paper. In order to verify the effectiveness of the calibration technique, the results are compared with the theoretical values. Consideration on the challenges of measurement in outdoor environment is countered with external and internal calibration. As a result, the proposed scatterometer system has shown good correlation between measurement and theoretical results.

An improved E-plane power divider for compact waveguide triplexers with large separation between channels is presented. The configuration of the divider aims to exploit the different behavior of the device for frequency bands with large separation, leading to a very asymmetric E-plane junction. H-plane filters with inductive windows are used for each channel, in order to obtain reduced insertion losses and lower sensitivity than in metal-insert E-plane filters. The resultant triplexer configuration is very compact, and its design is analyzed and optimized by Mode-Matching. The experimental results of a full Ku-band prototype for communications satellite systems show a very good agreement with the expected simulated response.

A novel blind Direction of arrival (DOA) and polarization estimation method for polarization-sensitive uniform circular array is investigated in this paper. An analysis of the received signal of the polarization-sensitive uniform circular array shows that the received signal has trilinear model characteristics, and hence trilinear decomposition-based blind DOA and polarization estimation for polarization sensitive uniform circular array is proposed in this paper. Our proposed algorithm has better DOA and polarization estimation performance. Our proposed algorithm can be thought of as a generalization of ESPRIT, and has wider application than ESPRIT method. The useful behavior of the proposed algorithm is verified by simulations.

In this paper we develop a new impulse-radio-based RF front-end module for ultrawideband communications. The proposed transceiving module is designed based a novel compact microwave sampler. The microwave sampler consists of a multilayered magic-T and a balanced sampling bridge. By utilizing a wideband microstripto-slotline Marchand balun, the newly proposed magic-T features an improved bandwidth of 94.2%. The design concept, circuit topology, and experimental results of the magic-T and microwave sampler are investigated in the first half of this paper. By utilizing the equivalent time sampling theory, in the second half of this paper we investigate an impulse-radio-based ultrawideband transceiving front-end module. Two transmission data rates, 90 and 270 Kbps, are demonstrated with various bit patterns. The experimental results reveal that the transceiving module has a coverage range up to 4.5 m. The circuit configuration, modulation scheme, and system performance of the front-end module are discussed thoroughly. The tradeoff for increasing the data rate is discussed at the end of this paper as well.

A research of W band microstrip integrated high order frequency multiplier based on avalanche diode is presented. The associated nonlinear model of avalanche diode driven by external RF signals for high order frequency multiplication is presented and analyzed according to the physical property of avalanche diode. Subsequently the circuit of microstrip integrated high order multiplier is analyzed. In experiment, maximum output power of 6.5 mW with the efficiency of about 0.62% is obtained at output frequency of 94.5 GHz with 15th multiplication order. The phase noise of output 94.5 GHz signal is about −90.83 dBc/Hz and −95.67 dBc/Hz at 10 KHz and 100 KHz offset.

In this paper, Wave Concept Iterative Procedure (WCIP) is used to investigate scattering by multilayered cylindrical structures in free space and to calculate the diffracted far field by adopting a cylindrical coordinate formulation. The WCIP principle consists of alternating waves between the modal and space domains. Its iterative resolution process is always convergent in lossless media case. The proposed technique used for determining the electric far field diffracted by a multilayered cylindrical structure is validated and confronted to literature results.

In this paper, we propose a new way to compact the transmission lines, which has a general application to miniaturization of RF and microwave circuits. In this way, we use Nonuniform Transmission Lines (NTLs) instead of Uniform Transmission Lines (UTLs). To synthesize the desired Compact Length Transmission Lines (CLTLs), the characteristic impedance function of the NTLs is expanded in a truncated Fourier series. Then, the optimum values of the coefficients of the series are obtained through an optimization approach. The usefulness of the proposed structures is verified using some examples.

In this paper, a new method is proposed to avoid crowding phenomenon in extracting the permittivity of ferroelectric thin films. Polynomial curve fitting technique is used to determine the filling factor while the thickness of the thin film is very small. Conformal mapping (CM) combining with partial capacitance approach (PTA) is used to obtain the relationshipb etween the effective permittivity of multiplayer coplanar waveguide (CPW) and the permittivity of each layer. A CPW with a thin film layer is simulated and the permittivity of thin film is extracted, the results show that, by using the proposed method, the crowding phenomenon can be avoided successfully and the permittivity of thin films can be extracted accurately.

A TE/TM wave splitter composed of a gyrotropic slab is proposed. We demonstrate theoretically that, when the working frequency is chosen to be within one of the two ranges, total reflection occurs at the boundary of a slab of gyrotropic medium for either TE or TM component of the incident waves. Tuning can be done by choosing the working frequency band or adjusting the applied magnetic field. Furthermore, within the TE-stop or TM-stop frequency region, if the incident angle is selected appropriately, the other polarized component of the wave is totally transmitted. And we also show that when the slab is thicker, there are more possibilities to satisfy the full-pass condition. Finite-element method simulations verified the theoretical results.

Fractional solutions of a parallel plate waveguide originally with impedance walls have been derived and fractional impedance of the guiding walls have been investigated. Two distinct ranges ofw all impedance have been found in which fractional impedance behaves in opposite ways. For 0 < α < 1, the fractional impedance is inductive in range 1 and is capacitive in range 2, where α is fractional parameter. For 1 < α < 2, the fractional impedance is capacitive in range 1 and is inductive in range 2. At the boundary ofthe two ranges, the fractional impedance is independent of α and is resistive. This behavior is periodic with period α = 2.

With the global search method of adaptive genetic algorithm (GA), an improved methodology is proposed to identify the equivalent radiating dipoles of real sources on substrates such as printed circuit boards (PCB) and then to regenerate the radiating far field. This methodology is based on a set of elemental electric- and magnetic dipoles which model the real sources. The numbers, positions and orientations as well as the elevations of each dipole are positioned by adaptive GA based on the comparison between the simulated and measured magnetic field. The methodology provides a possible way to identify the radiating source of planar circuits with ground plane.

A new non-air conduct speech detecting method is introduced in this paper by means of millimeter wave (MMW) radar. Due to its special attribute, this method may provide some exciting possibility of wide applications. However, the resulting speech is of less intelligible and poor audibility since the present of the combined and colored additive noise. This paper, therefore, investigates the problem of the MMW radar speech enhancement by taking into account the frequency-domain masking properties of the human auditory system and reduces the perceptual effect of the residual noise. Considering the particular characteristics of MMW speech, the perceptual weighting technique is developed and incorporated into the traditional spectral subtraction algorithm to shape the residual noise and make it inaudible. The results from both acoustic and listening evaluation suggest that the background noise can be reduced efficiently while the distortion of MMW radar speech remains acceptable, the enhanced speech also sounds more pleasant to human listeners, suggesting that the proposed algorithm achieved a better performances of noise reduction over other subtractive-type algorithms.

Various isolation improvement techniques for MIMO WLAN card bus applications consisted of three closely spaced loop antennas are presented and investigated both numerically and experimentally in this paper. The proposed techniques are easily implemented and proven effective to achieve high isolation among the antennas which is a must for MIMO terminals to receive uncorrelated signals with good system throughputs.

A modal-expansion method is proposed for the analysis of a monopole antenna in a vibrating reverberation chamber. Inside the chamber, electromagnetic fields are expanded using modal functions. Mode matching process is applied to enforce the boundary conditions at regional interfaces. Boundary conditions on the four side walls of the chamber are imposed by the point matching method. Combining these two matching processes, a set of matrix equations are obtained and the expansion coefficients can then be determined accordingly. The loss from the chamber walls is accounted for through homogeneous material filling. The input impedance and scattering parameter of a monopole in a reverberation chamber are computed and statistical analysis of the scattering parameter is conducted when one of its walls is vibrating.

This paper explores the feasibility of microwave imaging a buried object by the GA and using the S₁₁ parameter of a radiation antenna rather than data of the scattered electromagnetic field. To improve the efficiency of the GA-based algorithm, a technique of limiting the location of the buried object prior to the implement of the GA is proposed, and the GA is parallelized and executed on a PC cluster. A few numerical examples are presented, in which the dimension and location of a 3-D object buried in the earth are recovered. Results validate the proposed GA-based microwave imaging algorithm.

A new class of microstrip filter structures are designed, optimized, simulated and measured for ultra-narrowband performance essential to the wireless industry applications. More accurate model of the coupling coefficient is outlined and tested for narrowband filter design. Two sample filters are fabricated and measured to verify the simulations and prove the concept. The idea behind the new designs is based on minimizing the parasitic couplings within the resonators and the inter-resonator coupling of adjacent resonators. A reduction of the overall coupling coefficient is achieved even with less resonator separation which is a major issue for compactness of such filters. The best new designs showed a simulated fractional bandwidth (FBW) of 0.05% and 0.02% with separations of S = 0.63 mm and S = 0.45 mm, respectively. The measured filters tend to have even narrower FBW than the simulated, though its insertion loss deteriorates, possibly due to mismatch at the interface with external circuitry and poor shielding effect of the test platform. The investigated 2-pole filters are accommodated on a compact area of a nearly 0.6 cm². An improvement of tens of times of order in narrowband performance is achieved compared to reported similar configuration filters and materials. A sharp selectivity and quasi-elliptic response are also demonstrated with good agreement in both simulations and measurements. In all filters, however, the study shows that the narrower the FBW, the larger the insertion loss (IL) and the worse the return loss (RL). This is confirmed by measurements.

Circular arrays of log-periodic (LP) antennas are designed and their operational properties are investigated in a sophisticated simulation environment that is based on the recent advances in computational electromagnetics. Due to the complicated structures of the trapezoidal-tooth array elements and the overall array configuration, their analytical treatments are prohibitively difficult. Therefore, the simulation results presented in this paper are essential for their analysis and design. We present the design of a threeelement LP array showing broadband characteristics. The directive gain is stabilized in the operation band using optimization by genetic algorithms. We demonstrate that the optimization procedure can also be used to provide beam-steering ability to LP arrays.

This paper presents an ultra-wideband rectangular ring fed by stepped monopole antenna. The initial parameters of rectangular ring are first considered to obtain the bidirectional pattern with the desired resonant frequency. Subsequently, the parameters of stepped monopole for enhancing impedance bandwidth are investigated. To study the impedance and radiation behaviors, the simulations of the proposed antenna have been carried out. It is found that this antenna offers a bidirectional beam with the impedance bandwidth (return loss lower than -10 dB) covered the frequency range from 3.1 to 10.6 GHz. At the desired direction along this frequency band, the gain of 2.33-5.21 dBi is achieved. Furthermore, the prototype antenna was fabricated and measured to verify the simulated results. Obviously, the simulation and measurement are reasonably in good agreement.