http://www.hindawi.comThe latest articles from Hindawi Publishing Corporation© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/562193A novel two-layer highly efficient directive E-shaped patch radiator is described. By modifying the geometry of a rectangular patch and by introducing two slits, the size of the original rectangular patch is reduced. Further reduction in the size is achieved by stacking E-shaped patches. Both gain and efficiency of this modified antenna is increased by 16%. It is also observed that by introducing EBG structure, the bandwidth of the antenna is increased by 10.5% approximately.N. S. Raghava and Asok De© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/538216This paper presents an implementation of an iterative method based on the wave's concept, for analysing a ring resonator. This method includes a two-dimensional fourier modal transformation (2D-FMT) in a wave guide environment. The method has the advantage of simplicity in that it does not involve basis functions and inversion of matrices, as used in other calculation methods. Therefore, it is capable of analyzing larger bodies than other classical techniques. An implementation of the iterative calculation is shown for the extraction of S parameters of microwave components. The good agreement between simulation results and experimental published data justifies the design procedure and validates the present analysis approach.M. Yeddes, A. Gharsallah, A. Gharbi, and H. Baudrand© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2008/869720A method is proposed to synthesize optimally inhomogeneous planar layers (IPLs) as impedance matchers between two mediums. First, the electric permittivity function of the IPL 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 method is verified using some examples.Mohammad Khalaj-Amirhosseini© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/85181A general method is introduced to obtain the propagation constants of the inhomogeneous dielectric waveguide. The periodic Fourier transform is applied to the normalized Maxwell's equations and makes the field components periodic. Then they are expanded in Fourier series. Finally, the trapezoidal rule is applied to approximate the convolution integral which leads to a set of coupled second-order differential equations that can be solved as an eigenvalue-eigenvector problem. The normalized propagation constant can be obtained as the square roots of the eigenvalues of the coefficient matrices. The proposed method is applied to the dielectric waveguide with a two-layered dielectric profile in the transverse direction, and the first four-confined TE modes are obtained. The propagation constants for the mentioned dielectric waveguide are also derived analytically and are then compared with those derived by the proposed method. Comparison of results shows the efficacy of the proposed method.M. Moradian and M. Khalaj-Amirhosseini© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/41951We propose new empirical expressions for the characteristic impedance of a microstrip-like interconnect line in presence of ground plane aperture. The existing characteristic impedance expressions are modified so as to include the effect of the ground plane aperture. The variation in the characteristic impedance vis-à-vis the aperture size is established. The proposed expressions are general and valid for a range of dielectric materials concerning MICs, RFICs, and PCBs. The results are validated by measurements performed on a vector network analyzer.Rohit Sharma, T. Chakravarty, Sunil Bhooshan, and A. B. Bhattacharyya© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/75320The investigations on rectangular-slot-loaded and V-slot-loaded proximity-coupled microstrip antennas are reported. The performances of two antennas are investigated for the application in wireless local area network 2 (HIPERLAN/2) using IE3D software and the computed results are verified by measurement. Results show that the antennas have wide bandwidth and moderate gain and may be used as small, compact antennas for HIPERLAN/2 communication.Jibendu Sekhar Roy and Milind Thomas© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/47927This paper presents a 5 GHz wideband I/Q modulator/demodulator for 650 MHz OFDM signal bandwidth, which is integrated with a 5 GHz phase locked loop for I/Q generation. The quadrature signals are derived from a 10 GHz CMOS VCO followed by a bipolar frequency divider. The phase noise at 1 MHz offset is −112 dBc/Hz for the modulator as well as for the demodulator. The chips were produced in a 0.25 μm SiGe BiCMOS technology. The signal-to-noise ratio (SNR) of transmitted/received OFDM signal and the corresponding I/Q mismatch versus baseband frequency are given. The modulator achieves an SNR of 22–23 dB, and the demodulator realizes an SNR up to 22 dB. The modulator reaches a data rate of 2.16 Gbit/s using 64 QAM OFDM, and the demodulator realizes 1.92 Gbits/s.Klaus Schmalz, Eckard Grass, Frank Herzel, and Maxim Piz© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/10672A novel evolutionary computing algorithm, namely, jumping genes evolutionary algorithm (JGEA) is used for the optimization of antenna designs. This scheme incorporates with a multiobjective strategy that enables the gene mobility within the same chromosome, or even to a different chromosome. This type of horizontal gene movement causes the genes to find the suitable locations to achieve the necessary building blocks in such a way that the quality of nondominated solutions and/or the Pareto-optimal solutions can be enhanced. This new scheme is robust and provides outputs in speed and accuracy. It also generates a range of widespread extreme solutions. The design of an E-shaped patch antenna was adopted for the purpose of design demonstration. An antenna structure with 91% impedance bandwidth for a frequency range of 3.6–9.6 GHz was selected amongst the nondominated solutions set for the hardware fabrication. Its measured performances both for impedance bandwidth and frequency range were in good agreement with the simulated solution. The cross-polarized field was found to be small in comparison, and the copolarized field can sustain the broadside radiation pattern over the frequency band. This methodology of optimization can be of an alternative approach for antenna design.S. H. Yeung and K. F. Man© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/46350Novel topologies of rectangular microstrip patches providing broadside radiated one point fed radiators with enhanced gain are compared. The principle of the gain enhancement is based on an extension of a source area. Dominant in-phase current distribution on the patch is maintained by using higher order mode and geometrical modification of the patch topology. That is achieved by introducing suitable perturbation elements in the shape of slots and notches. Two principal patch topologies operating on TM21 and TM03 modes are described. A comparison of simulated and measured properties of realized prototypes at 10 GHz band are presented. The results show that gain 12.3 dBi of single patch can be reached.Milan Polivka and Alois Holub© 2008, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/86583As RF mixed-signal and patch-antenna-equipped SOC devices are becoming the dominant products worldwide, concerns over the large real-estate consumption by the spiral inductors (including those for microstrip antennas and impedance-matching inductances), as well as their generally Q-low (quality factor) performance, are now being discussed more than ever. Liao et al. have recently addressed the Q-low issue via using location-selective proton beam bombardment, whereby Q-improvements of 100%–300% were evidenced. That success, nevertheless, is at times tarnished by some undesirable features, that is, the explosive rises of inductances near certain frequencies, which practically cut short the Q-enhancement and were identified to be due to resonant interactions between the inductor-propagating EM wave and the proton-caused defect dipoles. In this paper, however, the authors attempt to turn this resonance-caused undesirability to favor by proposing a new way to greatly shrink down the needed inductor size through dipoles engineering.Chungpin Liao, Hsien-Ming Chang, and Jeng-Shin Hsu© 2008, Hindawi Publishing Corporation. All rights reserved.