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Microwaves, Antennas & Propagation, IET

Issue 7 • Date May 13 2011

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Displaying Results 1 - 16 of 16
  • Highly efficient heterogeneous modal superposition method for the full-wave analysis of arbitrarily shaped H-plane structures fed through rectangular waveguides

    Publication Year: 2011 , Page(s): 747 - 755
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (418 KB)  

    A new fully modal characterisation procedure is proposed to reduce the number of unknowns needed to characterise the ports of an arbitrary H-plane device in rectangular waveguide, so that no equivalent currents will be involved in the characterisation of the ports. Moreover, since no currents are needed to characterise the ports, the weights of the scattered modes can be unknowns of the resulting system of equations. This is an important fact, since, to find the wanted modal weights, a subsequent projection step is not necessary anymore. The new method is then advantageous when compared to other hybrid alternatives in the literature, not only because the ports are solved using fewer unknowns, which is the main advantage of the proposal, but also because the scattering parameters can be computed directly, once the system of equations is posed. View full abstract»

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  • Design and preliminary evaluation of a compact four-element terminal multiple-input multiple-output antenna for receiving antenna selection

    Publication Year: 2011 , Page(s): 756 - 763
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (821 KB)  

    A compact four-element multiple-input multiple-output (MIMO) antenna for receiving antenna selection at 2.3 GHz is designed and evaluated. Comparisons of MIMO systems employing antennas with different antenna selection schemes are presented. The system performances are evaluated and discussed in terms of channel capacity, average received signal-to-noise ratio and correlation coefficient between elements at the receiver. The impact of antenna orientations is also investigated. Based on the measured results, several subset antenna selection schemes are recommended in indoor application scenarios, which will contribute to compact terminal MIMO antenna design and optimisation complexity reduction. View full abstract»

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  • Ultra-wideband bandpass filters using broadside-coupled microstrip-coplanar waveguide

    Publication Year: 2011 , Page(s): 764 - 770
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (430 KB)  

    Bandpass filters that cover the ultra-wideband (UWB) frequency range (3.1-10.6-GHz) are presented. The filters utilise broadside-coupled microstrip-coplanar waveguide making them suitable for printed circuit board technology. To achieve a wide upper stopband, radial slots and stepped impedance resonators are employed either to suppress or to relocate the harmonic responses outside the band of interest. The presented design procedure relies on a quasi-static analysis and conformal mapping. The simulated and measured results of the proposed filters prove their suitability for UWB. Furthermore, the presented filters have a wide upper stopband that extends above 20-GHz, a compact size and less than 0.12-ns peak-to-peak variation in the group delay across the passband. View full abstract»

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  • High-performance low-pass filter using complementary square split ring resonators defected ground structure

    Publication Year: 2011 , Page(s): 771 - 775
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    In this study, a complementary square split ring resonator (CSSRR) using defected ground structure in microstrip line form is introduced. The CSSRR unit has interesting filtering characteristics, such as a very high attenuation rate, couple of the dimension-dependent finite attenuation poles and a very low-passband ripple level. Cascading CSSRR units with different dimensions has been used to design a high-performance low-pass filter (LPF) with a cutoff frequency (fc) of 1.80 GHz through a simple, straightforward design procedure. The designed LPF exhibits an attenuation rate of 300 dB/GHz and passband ripples of less than 0.30 dB. Moreover, it has a wide 20-dB stopband at up to 4.5 times fc with an attenuation of more than 30 dB in most of the stopband. To the authors knowledge, the overall performance of the LPF, particularly the attenuation rate, is the best among published reports to date. The designed filter has been fabricated and validated by measurements. View full abstract»

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  • Tunable microwave filters based on discrete ferroelectric and semiconductor varactors

    Publication Year: 2011 , Page(s): 776 - 782
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (381 KB)  

    This study presents a direct comparison between semiconductor and barium strontium titanate (BST) tuning technologies. Tapped line combline two-pole and four-pole bandpass filters were designed in a coplanar waveguide configuration. Discrete BST interdigital capacitors were fabricated and integrated into the filter circuits in a hybrid manner. The BST varactors performed as tuning elements in the filters. The same filter was also made using gallium arsenide (GaAs) varactors and the tuning and loss performance were compared with the BST filters. The centre frequency of the two-pole BST filter tuned 30.3% from 1.55 to 2.02%GHz with insertion loss ranging from 3.7 to 1.1%dB, at an electric field of 6.5%V/%m. This filter has a figure of merit of 0.87%dB-1. The two-pole GaAs filter showed a wide tuning range from 0.94 to 2.44 GHz at 14 V with insertion loss ranging from 4.2 to 0.8 dB. The results are discussed in detail, as it is important to clarify the comparison with relation to the quality of the materials, as well as the particular filter designs and centre frequencies involved. View full abstract»

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  • Design and realisation of an electrically small Huygens source for circular polarisation

    Publication Year: 2011 , Page(s): 783 - 789
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (547 KB)  

    The authors study the possibilities of realising circularly polarised Huygens source antennas combining electric and magnetic dipoles. The required combinations of dipoles are first studied analytically. Radiating elements comprising both electric and magnetic dipoles in a single element, namely, chiral particles, are then chosen as a way to realise the required dipole radiators. The use of elements that have equally strong electric and magnetic dipoles in a single element greatly simplifies the realisation and feeding of these antennas. The designed antennas are studied numerically and finally the radiation properties of the antennas are verified with measurements. The numerical and experimental results confirm that the antennas have radiation characteristics similar to a Huygens source. View full abstract»

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  • Fade and interfade duration statistics on an Earth-space link at 50 GHz

    Publication Year: 2011 , Page(s): 790 - 794
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (446 KB)  

    Statistics of fade and interfade duration have been derived from 1 year of slant path attenuation measurements at 50 GHz. It is shown that the normalised number of fades is almost independent of the attenuation threshold, while the opposite is observed for interfades. Fades and interfades of short duration, mainly because of scintillation, can be well represented by power-law distributions. Medium and long events, which are related to precipitation and clouds, follow log-normal distributions. The ITU-R model for fade duration performs reasonably well when compared with the experimental data. View full abstract»

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  • Design model for fully integrated high-performance linear CMOS power amplifiers

    Publication Year: 2011 , Page(s): 795 - 803
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (721 KB)  

    A model for fully integrated CMOS linear power amplifiers (PAs) is presented. The model predicts the performance of the CMOS PA in terms of power-added efficiency (PAE) and output power (POUT) with respect to the main design parameters, such as supply voltage, current consumption, gain and inductor quality factors (Qs). In order to demonstrate the usefulness of the model, several studies showing the impact of these design parameters on the PA performance are presented. Finally, a 0.18 m fully integrated CMOS PA has been fabricated and compared with the model, showing good agreement. The fabricated PA presents 23 dBm of 1 dB compression point (P1 dB) and 27 dBm of saturated power (PSAT) at 4.2 GHz with high maximum PAE of 32%. View full abstract»

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  • Design method for a lumped-element bandpass filter with two resonators and its application to multiplexers

    Publication Year: 2011 , Page(s): 804 - 810
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (479 KB)  

    A design method for a lumped-element bandpass filter is presented that simplifies construction of a multiplexer. Each filter consists of a series resonator and a shunt resonator. The input impedance of each filter designed in this study is near open-circuited at the resonance frequencies of the other channels. Owing to this property, all the filters can be connected together at a common port in parallel without any additional peripheral circuitry to build a multiplexer. This property is because of the combination of a series resonance circuit and a shunt resonance circuit of the filter. To verify the design method, a multiplexer with three channels is fabricated with lumped elements together with distributed elements. Measured results are in good agreement with prediction. The measured insertion loss is less than 0.5 dB at each channel, whereas return loss at each port is better than 15 dB and suppression of other channel signals is better than 20 dB. The isolation between channels is better than 20 dB. View full abstract»

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  • Ultra-efficient microwave harvesting system for battery-less micropower microcontroller platform

    Publication Year: 2011 , Page(s): 811 - 817
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    The experimental results of a micro-powered 2.45 GHz voltage multiplier with and without the charge-pump integrated circuit (IC) driving a microcontroller on FR-4 are presented. Five different rectifier designs are built and compared under different input power levels. Results show that a multi-stage voltage multiplier delivers higher voltage levels to the microcontroller without the need for the charge-pump IC. However, a single-diode design performs best when the charge-pump IC is present. The measurement results show that the energy harvesting system can provide 2 V to turn on the microcontroller with only 15.6 dBm (27.5 W) radio frequency input power and that the battery-less microcontroller can be wirelessly powered when located up to a distance of 57 cm from a transmitter supplying a total of just 100 mW of microwave power. View full abstract»

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  • Quality factor of E-plane periodically loaded waveguide resonators and filter applications

    Publication Year: 2011 , Page(s): 818 - 822
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (343 KB)  

    The quality factor of microwave resonators miniaturised by virtue of periodic loading is assessed. Five X-band resonators in E-plane technology with different miniaturisation factors have been designed to resonate at approximately the same frequency. The loaded quality factor is extracted from the fractional bandwidth and subsequently employed to estimate the unloaded quality factor. The study reveals that the unloaded quality factor drops approximately linearly with the miniaturisation. Subsequently design guidelines for E-plane filters with periodically loaded resonators are provided by means of an example involving a fifth-order filter. Full-wave simulated and experimental results are presented to validate the study. View full abstract»

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  • Band selection filter for ultra-wideband/Ku dual-band low-noise amplifier in the CMOS process

    Publication Year: 2011 , Page(s): 823 - 830
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (725 KB)  

    This work proposes a band selection filter (BSF) for a fully integrated ultra-wideband (UWB) 3.1-10.6-GHz/Ku band 11.8-14.8-GHz dual-band low-noise amplifier (LNA) in 0.13 μm CMOS technology. Detailed analysis and design criteria of the proposed BSF and wideband LNA are given. The operating frequency band can be selected by the transistor Mn between its off and on states. The BSF is designed, analysed and fabricated in a 0.18 μm CMOS process to verify its feasibility. The BSF has a minimum insertion loss of 0.7/2.9 dB for a low-pass and high-pass filter, and an input-referred IP3 (IIP3) exceeding 20/33 dBm in the off and on states. The measured performance of the switched LNA in UWB band achieves a maximum power gain of 12.3 dB and a 1-dB bandwidth of 2-10.5 GHz, a minimum noise figure (NF) of 4.9 dB and an IIP3 of -16.7 dBm. In Ku band, the measured performance are a maximum power gain of 10.7 dB with a 1-dB bandwidth of 11.5-13.5 GHz, a minimum NF of 5.7 dB and an IIP3 of -16.1 dBm. The dual-band LNA consumes a DC dissipation power of 14.3 mW from a 1.1 V supply voltage. The chip area, excluding pads, is only 0.35 mm2. View full abstract»

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  • Wideband planar printed antenna with end-fire radiation pattern

    Publication Year: 2011 , Page(s): 831 - 836
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (747 KB)  

    A compact printed planar antenna fed asymmetrically by a 50 Ω microstrip line is presented. This novel structural configuration is derived from conventional printed rectangular monopole, by introducing feed-line asymmetry to offer octave band end-fire radiation patterns. A rectangular ground plane of considerably small length and modified in shape with two symmetrical bevel slots on the upper edge, illustrate significant improvement in the input impedance matching of the antenna over the operating bandwidth. The influence of the length of the radiation patch and thickness of the dielectric substrate on the gain of the antenna is explored numerically. By linearly tapering the radiation patch, significant improvement in gain is observed. Both numerical and experimental reflection coefficient results confirm that the proposed antenna presents an impedance bandwidth of 94% for reflection coefficients less than -10 dB. The measured results present an optimum gain of 11.8 dBi and stable unidirectional radiation patterns. This novel antenna has wide impedance bandwidth, compact size and reasonably high gain, suitable for various broadband applications including point-to-point communication. The antenna is simple in structure with very few design parameters. View full abstract»

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  • New hat feed for reflector antennas realised without dielectrics for reducing manufacturing cost and improving reflection coefficient

    Publication Year: 2011 , Page(s): 837 - 843
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (670 KB)  

    This study presents a new hat feed that is made entirely of metal without using dielectric material. Compared to previous hat feeds where a piece of dielectric is used to support the hat on the waveguide, the new feed has lower manufacturing cost and higher reliability. In addition, the new hat feed has low radiation along the feeding waveguide, which makes the vertex plate unnecessary. Therefore the bandwidth over which the reflection coefficient magnitude is below -15 dB has increased. The feed has been optimised using a genetic algorithm. A prototype has been manufactured, and measured results are presented to verify the numerical simulations. View full abstract»

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  • Finite impulse response-filter-based RF-beamforming network for wideband and ultra-wideband antenna arrays

    Publication Year: 2011 , Page(s): 844 - 851
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (466 KB)  

    In this study, a wideband electronic beamforming concept applicable for ultra-wideband short pulse systems is derived and experimentally demonstrated. In particular, a finite impulse response (FIR)-filter-based beamforming network is configured such that an antenna array yields a desired radiation pattern within a predefined frequency range. An experimental verification of a wideband transmission system is presented for the frequency range from 1.5 to 2.0 GHz. The transmit system consists of a wideband power divider feeding a matrix of analogue FIR-filters. These FIR-filters control a circular antenna array of four elements. The receiver consists of a single antenna element. Measurements are performed in frequency domain using a vector network analyser. The results show an almost frequency independent radiation pattern with a half power beamwidth of 72 and a maximum sidelobe level of 10 dB. View full abstract»

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  • Stretchable dipole antenna for body area networks at 2.45 GHz

    Publication Year: 2011 , Page(s): 852 - 859
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1069 KB)  

    A stretchable antenna is proposed for body area networks operating at 2.45 GHz. The topology of the antenna is based on a meandered dipole with a parasitic arm, which has an impedance with a dual-resonance behaviour. The antenna impedance is optimised for the specific radio-frequency integrated circuit where it will be connected to. This topology has been implemented on two stretchable technologies using thermoplastic poly-urethane and silicone as substrates. A simple stretching model has also been proposed for design purposes and it has been validated through measurements. Simulations based on this model and real stretching measurements have shown the potential of the structure for obtaining a wideband match in stretched conditions, with optimised designs achieving a reflection coefficient lower than -10 dB up to 20 stretching. On-body simulations and measurements have also been done, which indicate that practical values of reflection coefficient and radiation efficiency can be achieved with a separation of few millimetres between the antenna and the human body. View full abstract»

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