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Microwaves, Antennas & Propagation, IET

Issue 1 • Date January 12 2011

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Displaying Results 1 - 13 of 13
  • Miniaturisation and electronic tuning techniques for microstrip spurline filters

    Page(s): 1 - 9
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    A new technique for the miniaturisation and electronic tuning of microstrip spurline filters is presented. The technique is based on connecting a reactive component across the end of the coupling gap of the spurline. The circuit is analysed by using a general coupled-line model, leading to the conclusion that, if a capacitance is used, the filter can be miniaturised or electronically tuned. The analysis leads to a set of simple design equations for these applications and a range of simulations are used to investigate the technique further. The validity of the techniques is demonstrated with three different practical circuits. For a miniaturised spurline filter operating at 1.8 GHz, 50 length reduction is achieved. Two varactor-tuned designs are described: a single-section and a cascaded spurline filter. The single-section spurline can be tuned across almost one octave bandwidth, from 580 MHz to 1.06 GHz whereas the cascaded design achieves tuning range of 320-723 MHz. View full abstract»

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  • Miniaturisation of Ε-negative transmission line based zeroth-order resonator antenna

    Page(s): 10 - 16
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (726 KB)  

    A previously presented ε-negative transmission line-based zeroth-order resonator antenna structure rescaled to operate at the 2.45 GHz ISM band. The antenna structure is investigated and its feeding network is minimised by using a properly located coaxial. Additionally, a design parameter capable of influencing the radiation pattern is explored. Moreover, this parameter can also reduce the size of the structure. The final antenna structure appears to be better or at least competitive to the best metamaterial-based antennas in terms of size-bandwidth performance. View full abstract»

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  • Rectangular microstrip antenna with uniaxial bi-anisotropic chiral substrate-superstrate

    Page(s): 17 - 29
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1600 KB)  

    The effects of the uniaxial anisotropy and chirality of the superstrate on the resonant frequency and bandwidth of rectangular microstrip patch in a substrate-superstrate configuration are investigated. The theoretical study is rigorously formulated via the integral equation and solved using Galerkin-s moment method. The complex resonant frequency for the TM01 mode is studied using sinusoidal basis functions. The effects of the uniaxial anisotropic permittivity on the resonant frequency of a monolayer have been studied by many authors. Recently the same resonator antenna with a uniaxial permeability and chiral substrate has been studied by the authors, and it was found that these elements enhance the antenna characteristics. Some researchers have suggested the use of an anisotropic superstrate to improve the characteristics of the antenna. Therefore the aim of this work is focused on the effects of a superstrate having uniaxial electric, uniaxial magnetic anisotropies, and chirality elements on the resonant frequency and the bandwidth of the rectangular microstrip antenna. View full abstract»

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  • High-efficiency Ka band microwave monolithic integrated circuit frequency tripler using lumped-element balun

    Page(s): 30 - 37
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (730 KB)  

    This work describes a lumped-element balun for use in a miniature, coplanar waveguide frequency tripler pseudomorphic high electron mobility transistor microwave monolithic integrated circuit. The measurement results of the balun show a 1-dB gain balance and a 10 degrees phase balance from 11.6 to 13 GHz. It was used in the design of a 36-GHz monolithic tripler at the input port. A resonant inductor and capacitor (LC) filter was used to eliminate the fundamental frequency and a phase delay line was employed to enhance the third harmonic in the tripler. At 36 GHz, the tripler achieved as minimum conversion loss of 6.7 dB at an input power of 13 dBm; the suppressions of the fundamental and second harmonic frequencies were 24 and 27 dB, respectively. View full abstract»

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  • Closely spaced array of cavity backed slot antennas with pin curtains walls

    Page(s): 38 - 47
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (928 KB)  

    An array of two cavity backed slot antennas with pin curtain walls is described. The use of pin curtains is shown to result in greatly reduced fabrication errors and improved repeatability. The effects of the pin curtain parameters on coupling between the array elements are investigated in order to establish design guidelines for achieving a mutual coupling performance which is as good as when using solid copper walls. It is found that these are not as strict as the general guidelines for pin curtains found in the literature. By means of extensive Finite Difference Time Domain simulations and measurements, the antenna performance characterised by impedance matching, radiation patterns and efficiency is shown to be unaffected when these pin curtains are used in place of solid copper walls. From this, a practical design has been arrived at. View full abstract»

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  • Bandwidth enhancement and decreasing ultra-wideband pulse response distortion of penta-gasket-koch monopole antennas using compact-grounded co-planar wave guides

    Page(s): 48 - 56
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (912 KB)  

    The concept is to use a grounded co-planar waveguide (GCPW) to enhance useful characteristics of a fractal antenna. In this case 9.54 dB return loss and input impedance bandwidths are increased. The specific candidate antennas are printed fractal monopoles such as the Penta-Gasket-Koch (PGK) antenna. These topical antennas are used to compare a coaxial fed system with GCPW-fed system. A PGK is applied for two bands germane to ultra-wideband (UWB). These are 5.35-7.35 GHz and 10.07 to 11 GHz (refer to VSWR <; 2). A modified PGK is presented with a wideband input match from 4.25 to 11 GHz (refer to VSWR <; 2). Results suggest that these antennas are possible candidates for Federal Communications Commission (FCC) UWB radio short fat pipe systems with time-domain analysis indicating reduced ringing for impulse excitation over the proposed FCC bandwidth. In addition, the correlation between the time-domain transmitting antenna's input signal and the receiving conventional PGK antenna output signal is obtained which demonstrates approximately 89% antipodal resemblance. The modified PGK antenna improves the antipodal resemblance up to 95% View full abstract»

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  • Analytical approach to optimise the efficiency of switching mode power amplifiers loaded with distributed matching networks

    Page(s): 57 - 67
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (631 KB)  

    This study describes the design methodology of optimising the power-added efficiency (PAE) of switching mode power amplifiers (SMPAs). To maximise efficiency, design optimisation of the harmonic loading networks using an analytical analysis approach is proposed. Indeed, by carefully designing a distributed harmonic control network at the output of the SMPA, the insertion loss through the load network can be minimised. To validate the PAE optimisation approach, two 10 W inverse class F power amplifiers (PAs) were designed, manufactured and tested at a frequency of 2.45 GHz using a GaN HEMT transistor. The first PA prototype was matched with a standard distributed harmonic loading network and the second with the proposed distributed harmonic loading network. The measured PAE and gain for the second prototype were improved by 3 and 0.17 dB to reach 73 and 14 dB, respectively. View full abstract»

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  • Effects of interface conditions and long-term stability of passive intermodulation response in printed lines

    Page(s): 68 - 76
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (718 KB)  

    An experimental investigation of the effect of conductor-to-substrate interface on distributed passive intermodulation (PIM) generation in printed microstrip lines has been undertaken using the custom-designed microwave laminates with removed surface bonding layers and with the commercial adhesion promotion applied to the conductor underside. The study of long-term stability of PIM performance of the printed circuits is reported for the first time. The comprehensive measurement results, observations of the self-improvement of the PIM performance and the effect of panel bending on PIM generation in printed boards with different finishing are presented. A consistent physical interpretation of the observed phenomena is proposed. The results of this study provide new important considerations for the design and characterisation of low-PIM printed circuits. View full abstract»

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  • Measurement-based methodology to design harmonic-loaded oscillators using real-time active load pull

    Page(s): 77 - 83
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (675 KB)  

    This study presents a measurement-based methodology to efficiently design a harmonic-loaded oscillator at a targeted frequency using the novel multi-harmonic real-time active load-pull (RT-ALP) technique. Owing to the speed of the RT-ALP technique the design procedure is quasi-interactive. Simulations were first used to design a stable negative resistance around 2.5 GHz using series feedback with a variable tapped capacitor to tune the negative resistance in the desired frequency band. The device lines were then measured for characterising the negative-resistance device versus input power at 2.5 GHz. Using RT-ALP the optimal second- and third-harmonic load impedances that provide the maximum output power were then determined. Two different load circuits were then designed and implemented to approach the optimal multi-harmonic load impedances and realise a stand-alone oscillator. In accordance with the Kurokawa theory, a reasonable agreement is obtained in terms of output power and frequency of oscillation between the stand-alone oscillator built and the multi-harmonic load-pull measurements demonstrating the viability of the proposed method. To our knowledge, this is the first fabricated oscillator designed with experimental active load-pull to consider third-harmonic tuning. View full abstract»

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  • Constitutive parameter extraction and experimental validation of single and double negative metamaterials

    Page(s): 84 - 94
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1345 KB)  

    In this study, two independent methods to extract the constitutive parameters of large-scale (more than a wavelength long) metamaterial (MTM) structures are described. One method is based on fitting the simulated inner electric/magnetic field to the electric/magnetic field computed with an analytical model, whereas the other method is based on the scattering matrix parameters. The extraction methods are tested on three MTM structures [two single negative and one double negative (DNG)] and show results that are in good agreement. The extracted parameters were used to predict a focusing effect in a simulated spherical concave lens made of DNG MTM. The three MTM structures were experimentally measured for insertion loss in an anechoic chamber. For practical reasons, the experimental models were fabricated on Duroid substrates and scaled to operate in X-band. Detailed explanation of the construction of the MTMs and the anechoic chamber measurement setup is given. The transmission characteristics were measured at different frequencies and at different incident angles. The measured and simulated results are found to be in good agreement. In the DNG MTM, a peak transmission of -0.7 dB was measured, which to these authors- knowledge is the highest reported to date for such an MTM structure. Good transmission is maintained for incident angles of up to 45° from boresight. View full abstract»

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  • Polarisation-sensitive geometric modelling of the distribution of direction-of-arrival for uplink multipaths

    Page(s): 95 - 101
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (589 KB)  

    This work extends the `geometric modelling` of channel fading to account for the effects of the polarisation states of the transmitting/receiving antennas, and for the distribution of the direction of arrival of the uplink multipaths. The derived formulas are closed-form functions, explicitly in terms of a few model parameters idealising the spatial geometry among the transmitter, the scatterers and the receiver. These formulas fit the empirical data well. View full abstract»

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  • Calderon multiplicative preconditioner based on curvilinear elements for fast analysis of electromagnetic scattering

    Page(s): 102 - 112
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (713 KB)  

    In this study, an efficient Calderon multiplicative preconditioner (CMP) based on the curvilinear elements is proposed for preconditioning electric field integral equation (EFIE) for three-dimensional electromagnetic problems. The curvilinear CMP are constructed by the curvilinear Buffa-Christinansen (BC) basis functions and curvilinear Rao-Wilton-Glisson (CRWG) basis functions, both of which can be presented as a linear combination of CRWG basis functions acting on barycentrically refined triangular meshes. Therefore the implementation of the curvilinear CMP-preconditioned EFIE allows direct application to the existing method of moments (MoM) code using CRWG basis functions and can be combined with the multilevel fast multipole algorithm (MLFMA) for electrically large problems and low-frequency fast multipole algorithm (LF-FMA) for low-frequency problems. The Caldron identities of the curvilinear CMP can lead to the fast convergence rate of iterative solvers for EFIE solutions, independently of the discretisation density. The numerical results demonstrate that the curvilinear CMP scheme with both MLFMA and LF-FMA lead to significant reduction of both the iteration number and the CPU time of monostatic radar cross-section (RCS) calculation. View full abstract»

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  • Mutual coupling suppression in closely spaced antennas

    Page(s): 113 - 125
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1722 KB)  

    A technique to significantly reduce the mutual coupling between closely spaced antennas operating at the same frequency band is presented. The method comprises the use of two ground-plane side walls that are erected vertically next to adjacent antennas. The side walls are defected with a lattice pattern of slots to form a defected wall structure (DWS). In addition, the adjacent antennas sharing a common ground plane are separated with a pair of slits in the ground plane. This technique implemented on closely packed antenna suppresses surface waves in the antenna's operation band and can provide isolation of 56'dB, which was achieved with a DWS loaded with mushroom-shape slots separating two microstrip patch antennas. In this case, the inter-antenna spacing (centre to centre) is 0.272'o and ground-plane size is 0.606 × 0.370 ×o2. Also investigated is the number of DWS slot loadings on isolation between adjacent antennas. Furthermore, the proposed technique is shown to substantially reduce mutual coupling between planar inverted-F antennas (PIFAs) and monopoles. The measured results validate the proposed technique and vindicate the simulation results. View full abstract»

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