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Conformal antenna arrays often have many elements with different radiation patterns and much cross-polarisation. Those factors make synthesising radiation patterns a difficult problem. In this study, the authors propose a balanced dynamic differential evolution (BDDE) algorithm to suppress the cross-polarisation in conformal arrays. To increase the probability of the inferior group participating in the mutant, a suboptimal individual is adopted in the mutant operation. Parameters are dynamically updated to accelerate the convergence speed. We adjust the cross-rate to its maximal value every few generations to increase the diversity in the population. Two conformal arrays are modelled to verify the ability of BDDE to synthesise the radiation pattern and polarisation simultaneously. To avoid increasing the number of unknowns caused by dual-feed antennas, circular polarised patch antennas with one feed are used to compose the conformal arrays. Embedded element patterns are used in the synthesis to take into account the influence of mutual coupling between the elements and their environment. We compare BDDE with other popular DE algorithms, and simulation results show that the proposed algorithm achieves lower sidelobe levels and cross-polarisation reliably and efficiently. [ABSTRACT FROM AUTHOR]

The design of multi-band bandpass filters (BPFs) employing stub loaded stepped-impedance resonator with defected microstrip structure (SL-SIR-DMS) is presented in this study for the first time. The proposed SL-SIR-DMS is created by embedding DMS on the low-impedance line of the SL-SIR. It is found that different defected structures can lead to different frequency responses. In addition, by using DMS, tri-band and even quad-band responses can be easily achieved without increasing the resonator size. As verification, one tri-band SL-SIR-DMS and one quad-band SL-SIR-DMS are designed and analysed using even/odd-mode method. Subsequently, one tri-band BPF and one quad-band BPF have been developed with pseudo-interdigital coupling to realise good out-of-band performance. The predicted results are compared with measured ones and good agreement is achieved. Compared with BPFs using only SL-SIR, the proposed filters with DMS are more compact due to the slow-wave characteristic. Compared with the BPFs using defected ground structure to improve the stopband performance, the proposed ones can realise comparable wide stopbands but maintaining the signal integrity on the ground plane for packaging purpose. [ABSTRACT FROM AUTHOR]

This study investigates the synthesis of multiple-pattern periodic phase-only control planar arrays. A hybrid generalised iterative Fourier technique is proposed to iteratively derive the array element excitations efficiently from the prescribed array factor, in which the two-dimensional Woodward-Lawson method is employed in order to generate good initial values. During the synthesis process, the phase-only control reconfigurable array is obtained by changing the corresponding phase for different array patterns while keeping the excitation amplitude constant. The robustness of the proposed algorithm has been testified by investigating the sensitivity of the radiation pattern affected by the amplitude and phase errors. Furthermore, three totally different types of reconfigurable numerical examples are discussed to validate the proposed method. Simulation results reveal the superior performance, the efficiency and the robustness of the proposed algorithm in dealing with multiple-pattern arrays. [ABSTRACT FROM AUTHOR]

A compact tri-band monopole antenna with coplanar waveguide (CPW)-fed structure is presented for applications in PCS and 2.4/5 GHz WLAN systems. By using a spiral strip and a meandered strip closed to an inverted-L ground strip, the proposed antenna with a compact size of 30 × 30 × 1.6 mm3 including the ground can not only meet the impedance bandwidth requirements for PCS band (1.85–1.99 GHz) and WLAN bands (2.4–2.484 GHz and 5.15–5.825 GHz), but also can provides good radiation characteristics and antenna gains for the operating bands, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2495–2498, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24593 [ABSTRACT FROM AUTHOR]

A novel compact microstrip low-pass filter (LPF) is proposed in this article. The proposed LPF is composed of semicircle-defected ground structures (S-DGS) and semicircle stepped-impedance shunt stubs (S-SISS). An equivalent lumped L-C circuit model is also presented. With the S-DGS and S-SISS, better band-stop performance and much smaller size can be obtained. Finally, theoretical and simulated results are presented, which are in good agreement with the measured results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3157–3160, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23938 [ABSTRACT FROM AUTHOR]

A novel planar three-way triple-band power divider is proposed in this article. The circuit is composed of three sections of three transmission lines and planar isolation resistors, which can provide high isolation and good amplitude balance simultaneously at three arbitrary frequencies. The structure of the power divider and the formulas used to determine the design parameters has been given. To verify the validity, a proposed power divider was fabricated and measured at 900, 1800, and 2400 MHz. Both theoretical and simulated results are presented, which are in good agreement with the measured results. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 182–184, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24858 [ABSTRACT FROM AUTHOR]

This article presents a compact branch-line coupler (BLC) for balanced-type circuit application. It was designed by utilizing cascading multisection and capacitance-loading technique for bandwidth increase and size reduction individually. The proposed BLC was simulated and fabricated. Its physical length reduces by 28.7%, while it performs as good as the conventional one. The simulated and the measured results have a good agreement. The method is valid for compact and good performance BLC design. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 198–200, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23992 [ABSTRACT FROM AUTHOR]

A compact and simple differential ultra wideband (UWB) equal power divider (PD) with one narrow notch-band is presented. The proposed PD is based on slotline resonators and balanced stepped-impedance microstrip-to-slotline transition structures. A wide differential-mode (DM) impedance bandwidth covering from 1.8 to 11.5 GHz can be achieved. Besides, independent common-mode (CM) responses with a larger bandwidth and higher suppression can be obtained. It is noted that the DM passbands are independent from the CM responses, which significantly simplify the design procedure. In addition, a narrow and sharp DM notched band from 5.8 to 5.9 GHz is generated by adding one pair of quarter-wavelength short-circuited stubs next to the microstrip line symmetrically. In order to illustrate the effectiveness of the design, a prototype is fabricated and measured. A good agreement between the simulated and measured results is observed. To the best of authors' knowledge, the proposed balanced UWB PD is the first ever reported. [ABSTRACT FROM AUTHOR]

A compact ultra-wideband (UWB) bandpass filter (BPF) with a notch band based on a slow-wave half-mode substrate-integrated waveguide (SW-HMSIW) is proposed. The proposed SW-HMSIW is believed to be the first ever reported. Similar to the slow-wave substrate-integrated waveguide (SW-SIW), SW-HMSIWs can achieve highpass characteristics, while the lateral width is reduced by about 50%. To obtain the UWB response, three spiral compact microstrip resonant cells are etched on the SW-HMSIW as a lowpass filter. Moreover, a shortcircuited quarter wavelength L-type resonator is used to achieve a notch band. To validate the design theory, a compact UWB BPF is designed and fabricated. The simulated results are compared with the measured results, and good agreement is reported. [ABSTRACT FROM AUTHOR]

A novel and compact tri-band microstrip-fed monopole antenna with dual-polarisation characteristics for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications is proposed. The antenna is composed of a partial ground and a Y-shaped radiating patch that consists of two unequal monopole arms and a modified circle monopole. The antenna is able to generate three separate impedance bandwidths to cover the frequency bands of the WLAN (2.4-2.484 and 5.8 GHz) and the WiMAX (3.4-3.7 GHz). In addition, the antenna is circularly polarised in both the WLAN bands. Furthermore, the antenna structure is extremely simple, durable and occupies small space, making it suitable for practical applications. [ABSTRACT FROM AUTHOR]