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Microwaves, Antennas & Propagation, IET

Issue 10 • Date July 17 2012

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Displaying Results 1 - 14 of 14
  • Frequency reconfigurable multiple-input multiple-output antenna with high isolation

    Publication Year: 2012 , Page(s): 1095 - 1101
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (772 KB)  

    A frequency reconfigurable multiple-input multiple-output (MIMO) antenna is presented. The proposed MIMO antenna consists of two reconfigurable printed monopole antennas with coupled conductors and an isolation improvement structure located between the two antennas. In order to change the operating frequency, PIN-diodes are embedded in the antennas. According to the on/off state of the PIN-diode, the resonant frequency is changed between the WLAN band (2400-2483 and 5150-5350-MHz) and the m-WiMAX band (3400-3600-MHz). The proposed isolation technique produces an S21 of less than -20-dB for both service bands. Simulation and measurement results confirm the antenna performance. Peak gains of 3.81-dBi at 2.4-GHz, 1.87-dBi at 5.2-GHz and 5.15-dBi at 3.5-GHz are found. Radiation efficiencies are greater than 58.85- over all of the operating frequency bands. The measured envelope correlation coefficient (ECC) and the mean effective gain (MEG) are suitable for use in MIMO antenna systems. View full abstract»

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  • Nested U-ring resonators: a novel multi-band metamaterial design in microwave region

    Publication Year: 2012 , Page(s): 1102 - 1108
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (793 KB)  

    In this study, a novel metamaterial topology, called M-band nested U-ring resonator (M-NURR), is proposed to provide multiple band operation with an electrically small and geometrically simple unit cell design. The M-NURR unit cell has M-nested and unconnected U-shaped metal rings printed on a dielectric substrate where each ring is primarily associated with a distinct LC type resonance frequency where L and C stand for inductance and capacitance, respectively. Therefore this M-NURR topology has the novel property that each of these resonance frequencies can be controlled almost independently by adjusting the arm length of the associated U-ring. In this study, three different M-NURR structures (for M=1, 2, 3) are designed, fabricated and characterised both numerically and experimentally with very good agreement. The suggested sub-wavelength M-NURR metamaterial topology is anticipated to be useful in the design of miniaturised multi-band mobile communication devices as it makes the fine tuning of operation frequencies possible by a simple parametric adjustment. View full abstract»

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  • Dual-band loop-loaded printed dipole array with a corporate balun/feed structure

    Publication Year: 2012 , Page(s): 1109 - 1116
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (908 KB)  

    A novel loop-loaded printed dipole (LLPD) antenna array is introduced for a dual-band operation at 3.0/5.5 GHz bands. As the loop elements placed on the dipole aperture provide the dual-band operation, a new corporate balun/feed structure is employed to achieve balanced and matched excitation for the array. The simulation and measurement results for 1 × 1, 2 × 2 and 4 × 4 LLPD array designs are presented, demonstrating quite well agreement. In particular, the 4 × 4 design offers better than 17% impedance bandwidth and a realised gain of at least 15 dBi with tolerable side-lobe levels at the designated frequency bands. View full abstract»

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  • Periodicity of the input impedance of log-periodic array antennas

    Publication Year: 2012 , Page(s): 1117 - 1122
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (514 KB)  

    One way for an antenna to achieve an ultra-wideband (UWB) performance is to employ a log-periodic array (LPA), which usually involves many scaled elements cascaded one after another. If an LPA is infinite at both ends (infinitely small at one end and extended to infinitely large at the other end), it is obvious that the input impedance of the array is periodical over frequencies. However, for practical antennas, infinite LPAs have to be truncated. The purely periodical performance will not hold anymore. On the other hand, UWB LPA antennas are often very large in terms of the wavelength at the highest operating frequency, which makes numerical simulation very time consuming. The author presents a theoretical analysis of the periodicity of the input impedance of a general finite LPA. New periodicity formulas are verified by examples of the Eleven antenna - a folded dipole LPA, with simulated and measured data. By using the new periodicity formula, the input impedance of a large LPA antenna at higher frequencies can be predicted by its values at lower frequencies, which leads to an efficient calculation when a numerical simulation is employed, and helps to have an efficient design of large LPA antennas. View full abstract»

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  • Patch microstrip antenna with improving radiation performance for 2.4-GHz WLAN access point

    Publication Year: 2012 , Page(s): 1123 - 1127
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (510 KB)  

    A patch microstrip antenna with an inverted-V ground plane capable of improving radiation performance for a wireless local area network (WLAN) access point in the 2.4-GHz band is presented. By using a feeding structure composed of a step-shaped feeding strip in the air substrate and a coplanar strip in the narrow radiating patch, the proposed antenna can reduce cross-polarisation radiation (less than -20-dB) for frequencies across the 2.4-GHz WLAN band. The inverted-V ground plane comprises a narrow central ground portion for setting the 50 subminiature version (SMA) connector for the patch antenna and two bent ground portions to control the broadening of the antenna s horizontal radiation pattern. By selecting the proper dimensions, the proposed antenna can have a wide horizontal radiation pattern of about 152 (3 dB beamwidth) with vertical polarisation, which is very suitable for WLAN access-point applications where uniform radiation in one direction or one half-space is required. Experimental results of a constructed prototype suitable for application in the 2.4 GHz WLAN access point are presented and discussed. View full abstract»

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  • Suppression of spurious responses in microstrip filters using a reduced number of resistors

    Publication Year: 2012 , Page(s): 1128 - 1135
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (555 KB)  

    The stop band of a microstrip filter was extended by suppressing its harmonics, using additional stubs together with a smaller number of resistors than in the previous work. The possibility of suppressing the second to the fifth harmonics with one resistor per resonator is investigated in a simulation. Equations for initial estimates for losses and required coupling coefficients for the new stub design are given. In a simulation of a fourth-order filter, a total of only two resistors were required to suppress the second, third and fourth harmonics to -35-dB; -29-dB was achieved in a fabricated filter. The pass band loss was only increased by 0.2-dB. View full abstract»

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  • Electronically controlled asymmetric microstrip line coupler underpinned by an hybrid right-/left-handed line

    Publication Year: 2012 , Page(s): 1136 - 1141
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    This work presents a microstrip coupler based on an hybrid right-/left-handed (RH/LH) line whose coupling ratio is electronically controlled. After some considerations on the LH line theory, the asymmetric RH/LH coupler is presented focusing on the parameters yielding the coupling ratio and the frequency range. The dependence of the coupling ratio on the number of cells constituting the coupler is highlighted. From these results, a prototype of a coupler with an electronically switched ratio has been developed. The variable coupling ratio is obtained by switching ON or OFF some cells in the structure of the coupler. The isolation of the OFF mode of the electronic switch implemented is carefully studied. Measurements and calculus are presented in order to estimate the isolation factor required to obtain a significant variation of the coupling ratio as well as to illustrate the original behaviour of such couplers. A functional electronically controlled coupler with one switch implemented is finally characterised and its performances are discussed. View full abstract»

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  • Micro-coaxial V-/W-band filters and contiguous diplexers

    Publication Year: 2012 , Page(s): 1142 - 1148
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (551 KB)  

    A millimetre-wave diplexer is demonstrated using two singly terminated bandpass filters fabricated using surface micromachined rectangular-coaxial transmission lines. Modified seventh order Chebyshev bandpass filters with 0.1 dB passband ripple are designed to operate from 50 to 75 GHz and from 75 to 110 GHz. These two filters are simply combined using a common junction to form a contiguous 50-75 GHz and 75-110 GHz diplexer. The singly terminated filter values are adjusted by use of a common factor that modifies the admittance properties of the filter to facilitate their parallel combination. The two filters and their diplexer combination are fabricated and the measurements are compared favourably to the theoretical models. View full abstract»

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  • Indoor guidance system for the blind and the visually impaired

    Publication Year: 2012 , Page(s): 1149 - 1157
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (625 KB)  

    The authors describe the design of a suitable antenna and receiver for navigation between doors in order to help the blind or the visually impaired moving inside buildings. The proposed antenna must have an extremely narrow radiation pattern. The reason behind this specification is related to the way the receiver would let the user know that a door entrance is approaching; in other words, the identification of a door is made through the search of the maximum of the radiation pattern. Once the maximum value of power is found, the person knows that he or she is correctly positioned to enter or exit the room with the help of an adequate receiver to process the signal. View full abstract»

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  • High-power, high-efficiency CMOS millimetre-wave oscillators

    Publication Year: 2012 , Page(s): 1158 - 1163
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (659 KB)  

    High-power, high-efficiency millimetre-wave oscillators were implemented in IBM 45 nm silicon-on-insulator (SOI) complementary metal-oxide semiconductor (CMOS). A voltage-controlled oscillator (VCO) was designed using a class-E power amplifier in a positive feedback configuration and an injection-locked oscillator (ILO) was implemented using a cross-coupled design with fundamental frequency injection at the device drains. The VCO exhibits an output power of 8.2 dBm and a peak efficiency of 15.64 . The tuneable range of the VCO is 45.5 - 47.5 GHz. The measured phase noise is -106.51 dBc/Hz at a 1 MHz offset. This VCO achieves the highest reported efficiency and output power for silicon-based monolithic millimetre-wave oscillators to the best of the authors knowledge. The ILO exhibits a locking range of approximately 3 GHz for a -10 dBm injected signal and an output power of 5.2 dBm for the minimum injected locking power at its centre frequency of 45 GHz, yielding a power-added efficiency of 6.1 . View full abstract»

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  • Generalised single-section broad-band asymmetrical Wilkinson power divider

    Publication Year: 2012 , Page(s): 1164 - 1171
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    This study presents microstrip non-uniform transmission lines (MNTLs) for asymmetrical single-section broad-band Wilkinson power divider design without reactive components. The proposed topology uses an asymmetrical MNTL section and three MNTLs for input/output transformers. The proposed structure demonstrates broad-band performance, low insertion loss and compact size in comparison with other proposed multi-section broad-band Wilkinson power dividers. An MNTL broad-band power divider working from 0.4 to 1.8 GHz is fabricated, and the measured results validate good broad-band performance with more than 127 bandwidth. View full abstract»

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  • Compact dual-band bandpass filter with controllable bandwidths using stub-loaded multiple-mode resonator

    Publication Year: 2012 , Page(s): 1172 - 1178
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (606 KB)  

    A compact microstrip-line dual-band bandpass filter using a stub-loaded multiple-mode resonator is presented. This multiple-mode resonator is formed by loading three stubs (one short-circuited and two open-circuited stubs) in shunt to a simple uniform impedance resonator in the centre and two symmetrical locations, respectively. By properly adjusting the lengths of the three stubs, the first two resonant modes of this multiple-mode resonator can be allocated within the first passband, whereas the third and fourth resonant modes can be allocated within the second passband of the dual-band filter. This results in the formulation of a novel dual-band filter with compact-size and high isolation between passbands by incorporating this multiple-mode resonator with source-load coupling. Two coupling paths are used to control the bandwidth of each passband independently. To illustrate the concept, two dual-band filters of different frequency ratios are designed, fabricated and measured. Simulated and measured results are found to be in good agreement with each other, showing that a rejection level of 15 dB up to more than four times the first passband frequency can be obtained. View full abstract»

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  • Four-port beam reconfigurable antenna array for pattern diversity system

    Publication Year: 2012 , Page(s): 1179 - 1186
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1044 KB)  

    This study investigates a practical design for a switched beam planar antenna that can be implemented as a compact, low-cost switchable and/or reconfigurable beam antenna array. The antenna consists of a four-port antenna array, which is based on L-shaped quarter-wavelength slot antenna elements. This type of antenna array is a planar structure and its maximum directional radiation beam pattern presents in an azimuth plane covering 3600. The antenna array operates based on the `ON' or `OFF' states of PIN diodes in each individual slot antenna element and the combined signals from the four-port output. Therefore by properly controlling the state of the PIN diodes, the antenna exposes its characteristics of switchable/ reconfigurable beam patterns in the Φ-plane. To validate the proposed design, a small smart, switched-beam antenna operating at 2.7 GHz in multiple input-multiple output applications is simulated and fabricated. View full abstract»

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  • Modelling the shape, length and radiation characteristics of bond wire antennas

    Publication Year: 2012 , Page(s): 1187 - 1194
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (764 KB)  

    Novel analytical models for accurately modelling the shape and length of bond wires in dependence on the loop height (Lhmax), distance between the bonding positions (dbp) and the thickness of the metallisation (tmet.) on which the wires are bonded, are derived in this work. These analytical models, which are based on the Gaussian distribution function, are applied to (i) develop realistic three-dimensional electromagnetic models of bond wire antennas and study their radiation characteristics and (ii) study the impact of process tolerances of bond wire parameters on the performance of the antennas. For these studies, a 42 GHz half-loop bond wire antenna is considered as an example. It is designed, fabricated and measured. Our results reveal that dbp has the most significant impact on the antenna performance. For example, -10% fluctuations in dbp causes ~2.5 GHz shift in the resonance frequency and 24% reduction in the maximum realised gain. Since this may completely detune the antenna, it is recommended that fluctuations in dbp should be kept below 10% during the manufacturing process. Good correlation is obtained between measurement and simulation results. View full abstract»

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