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Microwaves, Antennas & Propagation, IET

Issue 10 • Date July 16 2013

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Displaying Results 1 - 12 of 12
  • Planar wideband inphase power divider/combiner using modified Gysel structure

    Page(s): 783 - 787
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    The design of a wideband inphase power divider/combiner is presented. It uses a modified Gysel structure for an increased band and a reduced number of isolation resistors to only one. The power divider has a simple structure that does not use any slots in the ground plane, and is thus fully compatible with microstrip circuits. Moreover, the device uses one external isolation resistor, and thus it is suitable for high-power microwave applications because of the easy connection of the isolation resistor to a suitable heat sink. A theoretical analysis is presented to find the values of the design parameters for wideband performance. The simulated and experimental results of the designed divider show 69% fractional bandwidth assuming 15 dB of isolation as a reference. View full abstract»

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  • Bandwidth limitations of ultra high frequency–radio frequency identification tags

    Page(s): 788 - 794
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (342 KB)  

    Fundamental bandwidth limitations on the design of ultra high frequency (UHF) radio frequency identification (RFID) tags are investigated. This study was conducted by considering the optimum equivalent-circuit network necessary for bandwidth broadening in single resonant UHF-RFID tags with conjugate matching. This equivalent-circuit network is simply a parallel combination of an inductor and a resistor cascaded to the UHF-RFID chip. Bandwidth optimisation of the resulting network is validated by means of the Bode criterion. According to this analysis, a broadband UHF-RFID tag prototype able to operate worldwide is designed and fabricated. In order to reduce tag size and cost, the external matching network is omitted in the reported implementation. The measured read ranges are above 5 m within the whole UHF-RFID frequency band (840-960 MHz), with a peak value of 9 m at 870 MHz. View full abstract»

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  • Substrate integrated waveguide filters with broadside-coupled complementary split ring resonators

    Page(s): 795 - 801
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (574 KB)  

    Four designs of substrate integrated waveguide (SIW) filter employing integrated broadside-coupled complementary split-ring resonators are compared. By changing the orientation of the rings, four types of SIW unit cell are proposed and investigated and it is shown that, for one particular topology, two poles and two zeros can be realised with a single unit cell. Bandpass filters based on the proposed resonators coupled by evanescent-mode SIW sections have been fabricated and tested. The proposed filters have the advantages of compact size, high selectivity and ease of integration. View full abstract»

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  • Simple and low-cost tracking generator design in envelope tracking radio frequency power amplifier system for WCDMA applications

    Page(s): 802 - 808
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    A simple analogue technique called auxiliary envelope tracking, or AET, is presented, which is shown to be capable of improving the efficiency of a radio frequency power amplifier (RFPA). This AET signal is an amplified envelope signal that supplies the drain port of the RFPA. The concept of AET is explained and a theoretical background for the technique is presented. The main feature of this technique lies in the separation of the DC and AC components of the tracking signal. This allows for a very simple and low-cost tracking generator design that consists of a simple source follower amplifier and an RF broadband transformer. A practical system has been implemented and the measured results are obtained for WCDMA signals. A measurement on the realised system shows a 50% improvement in the drain efficiency at average output power of 33 dBm of a 25 W GaN. This substantial improvement is achieved at a competitive WCDMA signal with peak-to-average envelope power ratio of 9.17 dB. View full abstract»

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  • Microwave signal conditioning through non-reciprocal phase shifting

    Page(s): 809 - 818
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1199 KB)  

    Two non-reciprocal microwave signal conditioning circuits, a non-reciprocal phase shifter and a quasi-circulator, are proposed as based on the use of active microwave devices. Analytical expressions are derived to demonstrate the principles of operation and prototypes are presented both in hybrid and monolithic form. The hybrid structures operate in the L-band, whereas the monolithic ones are designed for X-band operation, and demonstrate the compactness and performance of the proposed topologies. View full abstract»

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  • Multi-band and multi-polarised reconfigurable antenna for next generation mobile communication base-station applications

    Page(s): 819 - 824
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (841 KB)  

    A novel multi-band reconfigurable antenna for a mobile base-station is proposed. This antenna can be operated in three bands using three radiators, but the radiators are physically combined into one body in consideration of size reduction and optimal performance. Radiator 1 is a square patch structure and is operated in 0.824-0.894 GHz for cellular service. Radiator 2 provides multiple mobile services in 1.75-2.48 GHz for personal communication service (PCS), wideband code division multiple access (WCDMA), world interoperability for microwave access (WiMAX) and WiFi, and thus has a wideband characteristic using a printed dipole structure. Finally, radiator 3 has a stacked structure composed of a radiating and a parasitic patch in 3.3-3.6 GHz for WiMAX2. Radiator 1 has a cylindrical cavity in the centre of the patch, and is designed not to degrade electrical performance, and radiator 3 is embedded in the cavity of radiator 1. Radiator 2 is composed of four printed dipoles and is vertically stacked on radiator 1 around radiator 3 with a rectangular formation. All radiators can provide dual-polarisation using multi-ports controlled by a switching circuit with a control program. In the switching circuit, there are two MEMS switches for band selection. Using the proposed structure, the authors realise a novel multi-functional reconfigurable antenna using three individual radiators. View full abstract»

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  • Single feed circularly polarised omnidirectional bifilar helix antennas with wide axial ratio beamwidth

    Page(s): 825 - 830
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    This study presents design and analysis of single feed omnidirectional circularly polarised resonant side-fed bifilar helix antennas with wide axial ratio (AR) beamwidth that does not require a ground plane. The simulation results show that side-fed helix antennas of various radii give polarisation beamwidth (for AR ≤3 dB) from 170° to 178° in elevation planes at a certain turn angle where area of the loop equals the product of pitch and radianlength of the helix. Circularly polarised helix antennas with smaller radii are of higher turn angle, have lower value of resonant input impedances but AR is less sensitive to inaccuracy in turn angle and vice versa for helix with larger radii. The gain and 3 dB beamwidth of the antennas are 2 dBi and 90°, respectively. The polarisation bandwidth (for AR ≤3 dB) varies from 34 to 65%. The simulated results are verified by experimental measurements. View full abstract»

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  • Ultra-wideband slot antenna with a stop-band notch

    Page(s): 831 - 835
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    In this study, a simple and compact ultra-wideband (UWB) printed slot antenna with band-notch performance is designed and manufactured. To increase the impedance bandwidth of the square slot antenna, the authors use an S-shaped parasitic structure inside the rectangular slot on the feed line. By using this structure UWB frequency range can be achieved. Additionally, by using square-ring stub with two L-shaped protruded strip inside the square-ring stub, a frequency notched band performance has been obtained. The designed antenna has a small size of 20 × 20 mm2, wheeas showing the radiation performance in the frequency band of 3.05 to over 12.76 GHz with a band rejection performance in the frequency band of 5.13 to 6.04 GHz, which has a frequency bandwidth increment of 13% with respect to the previous similar antenna. View full abstract»

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  • Frequency-selectable dual-band Wilkinson divider/combiner

    Page(s): 836 - 842
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (507 KB)  

    A technique for realising a compact frequency-selectable dual-band Wilkinson divider/combiner is presented in this study. To provide a frequency-selection function, the band-pass transmission-line transformer (TLT) in a dual-band device is replaced with a tuneable band-reject TLT. To realise this tuneable device, a variable capacitively loaded spur-line filter is proposed for its compact size. The theory based on an ideal transmission-line circuit is developed to provide a design procedure. The proposed circuits are demonstrated with simulated and measured results of a Wilkinson divider/combiner fabricated on FR4 substrate. View full abstract»

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  • Enhanced and directional transmission through a slit surrounded with grooves in a conducting plane

    Page(s): 843 - 850
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (558 KB)  

    Enhanced and directional transmission through a slit surrounded with grooves in a conducting plane is investigated. A boundary-value problem of electromagnetic wave scattering from a slit surrounded with a finite number of rectangular grooves on both surfaces in a conducting plane is rigorously solved based on the eigenfunction expansion, Fourier transform and mode matching method. The radiated power density and the transmission coefficient are represented in a series. Computation is performed to illustrate the transmission behaviours in terms of the groove geometry. View full abstract»

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  • Uniplanar polarisation diversity antenna for ultrawideband systems

    Page(s): 851 - 857
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1088 KB)  

    A new compact, uniplanar, polarisation-diversity, monopole-like slot antenna for ultra-wideband (UWB) systems is presented. The proposed design effectively integrates orthogonally fed slot antennas, utilising the uniplanar nature of coplanar waveguide without degrading the time-domain characteristics and diversity performance. To achieve high isolation between the ports, a strip is integrated diagonally in the ground plane. Furthermore, by loading arc shaped slot resonators on the feeding structures, the proposed antenna successfully rejects the undesired subband, assigned for IEEE 802.11a and HIPERLAN/2. The measured results demonstrate that the antenna provides a 2:1 voltage standing wave ratio (VSWR) band from 2.76 to 10.75 GHz whereas showing rejection in the frequency band 4.75-6.12 GHz, along with an inter-port isolation better than 15 dB. The proposed radiator displays a nearly omnidirectional radiation pattern, along with a moderate gain and efficiency. The envelope correlation coefficient discloses a good diversity performance across the UWB spectrum. Furthermore, the time-domain analysis shows minimum dispersion to the radiated pulse. In addition, the experimental analysis indicates that the proposed design is less disposed to the housing effects when mounted in metallic casing. All these features make the proposed antenna a viable candidate for UWB dual-polarised multiple-input-multiple-output applications. View full abstract»

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  • Inkjet-printed antennas, sensors and circuits on paper substrate

    Page(s): 858 - 868
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (932 KB)  

    Inkjet-printing is a very promising technology for the development of microwave circuits and components. Inkjet-printing technology of conductive silver nanoparticles on an organic flexible paper substrate is introduced in this study. The paper substrate is characterised using the T-resonator method. A variety of microwave passive and active devices, as well as complete circuits inkjet-printed on paper substrates are introduced. This work includes inkjet-printed artificial magnetic conductor structures, a substrate integrated waveguide, solar-powered beacon oscillator for wireless power transfer and localisation, energy harvesting circuits and nanocarbon-based gas-sensing materials such as carbon nanotubes and graphene. This study presents an overview of recent advances of inkjet-printed electronics on paper substrate. View full abstract»

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IET Microwaves, Antennas & Propagation covers all aspects of microwave and antenna engineering and propagation.

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