Showing papers in "Electronics Letters in 2004"
TL;DR: In this paper, a direct, point-by-point inscription of fibre Bragg gratings by infrared femtosecond laser is reported for the first time, in a non-photosensitised, standard telecommunication fibre and dispersion shifted fibre.
Abstract: Direct, point-by-point inscription of fibre Bragg gratings by infrared femtosecond laser is reported for the first time. Gratings of first to third order have been produced in non-photosensitised, standard telecommunication fibre and dispersion shifted fibre.
419 citations
TL;DR: In this paper, a printed circular disc monopole antenna for ultra-wideband applications is presented, and the parameters which affect the performance of the antenna are investigated. Good agreement is achieved between simulation and experiment.
Abstract: A novel and simple design of a printed circular disc monopole antenna for ultra-wideband applications is presented. The parameters which affect the performance of the antenna are investigated. Good agreement is achieved between simulation and experiment.
314 citations
TL;DR: In this paper, a CPW-fed planar ultra-wideband antenna with hexagonal radiating elements is presented, where the antenna also has a frequency band notch characteristic.
Abstract: A CPW-fed planar ultra-wideband antenna with hexagonal radiating elements is presented. The antenna also has a frequency band notch characteristic. By inserting a V-shaped thin slot on the hexagonal radiating element, the narrow frequency band notch has been created very close to the desired frequency.
299 citations
TL;DR: In this paper, a channel model for a wireless body area network at 400 MHz, 900 MHz and 2.4 GHz was derived and the electromagnetic wave propagation around the body was simulated with a finite-difference time-domain simulator.
Abstract: A channel model for a wireless body area network at 400 MHz, 900 MHz and 2.4 GHz is derived. The electromagnetic wave propagation around the body is simulated with a finite-difference time-domain simulator. Creeping waves were identified as the propagation path around the body. Its impact on the delay spread in an indoor environment is discussed.
269 citations
TL;DR: A small and low-cost antenna solution for radio frequency identification (RFID) tags is presented that is applicable in many different environments because the impedance of the antenna is immune to the platform.
Abstract: A small and low-cost antenna solution for radio frequency identification (RFID) tags is presented. The impedance of the antenna is designed to match directly to the impedance of the RFID microchip. Also, the impedance of the antenna is immune to the platform. Thus, the antenna is applicable in many different environments. The design and measurement results are reported and discussed.
238 citations
TL;DR: The filter has a new dual-band feature of two tunable passbands at desired frequencies and high out-of-band suppression, generated by incorporating step-impedance resonators in a comb-filter topology.
Abstract: A step-impedance bandpass filter is presented for multimode wireless LANs. The filter has a new dual-band feature of two tunable passbands at desired frequencies and high out-of-band suppression, generated by incorporating step-impedance resonators in a comb-filter topology. It saves more than half the circuit size compared with the switch-type dual-band topology. The simulation and measurement results show the dual-band feature of two passbands at 2.45 and 5.75 GHz with 85 dB suppression at 3.5 GHz.
217 citations
TL;DR: Experimental results show that an adaptive Butterworth highpass filter presented to detect a small target under a sea-sky complex background is a robust small target detection method.
Abstract: An adaptive Butterworth highpass filter is presented to detect a small target under a sea-sky complex background. By calculating the weighted information entropy of different infrared images, the cutoff frequency of the filter can be changed adaptively. Experimental results show that it is a robust small target detection method.
200 citations
TL;DR: In this paper, a quantum key agreement protocol for quantum teleportation is presented. But the key bits are determined only by random measurement outcomes and are independent of the states transmitted over the channel.
Abstract: By replacing a classical channel with a quantum one during quantum teleportation, a quantum key agreement protocol is presented. The key bits are determined only by the random measurement outcomes and are independent of the states transmitted over the channel.
191 citations
TL;DR: In this article, an all-digital CMOS ultra wideband (UWB) pulse generator which complies with FCC regulations is presented, and the proposed pulse generator generates a single UWB pulse satisfying FCC regulations without any filtering.
Abstract: An all-digital CMOS ultra-wideband (UWB) pulse generator which complies with FCC regulations is presented. The proposed pulse generator generates a single UWB pulse satisfying FCC regulations without any filtering. The average power consumption of the whole circuit is 15.4 mW and 675 /spl mu/W at the pulse repetition frequency of 500 and 1 MHz, respectively.
168 citations
TL;DR: In this paper, it was demonstrated that the resonant frequency of split ring resonators (SRRs) can be tuned using varactor diodes and the resulting particle, which is called a varactor-loaded split-ring resonator (VLSRR), is applied to the design of a tunable notch filter at S-band.
Abstract: It is demonstrated that the resonant frequency of split ring resonators (SRRs) can be tuned using varactor diodes. The resulting particle, which is called a varactor-loaded split ring resonator (VLSRR), is applied to the design of a tunable notch filter at S-band. The device consists on a microstrip transmission line with VLSRRs placed at both sides of the conductor strip. Owing to the proximity of the particles to the line the rings are excited and a transmission notch arises. It is shown that simply using two VLSRRs pairs, rejection levels above 20 dB are achieved in a 0.5 GHz tuning interval centred at 2.85 GHz. The proposed device is the first tunable notch filter based on SRRs.
160 citations
TL;DR: In this paper, a modified printed Yagi antenna with a simplified feed mechanism is proposed, where the driver dipole is fed by a transmission line formed by two parallel strips printed on opposite sides of the dielectric substrate.
Abstract: A modified printed Yagi antenna with a simplified feed mechanism is proposed. In the new design, the driver dipole is fed by a transmission line formed by two parallel strips printed on opposite sides of the dielectric substrate. This simplified feed structure results in the reduction of the transmission line length, and, consequently, the radiation losses. The analysis of the modified Yagi antenna is performed numerically using Ansoft high frequency structure simulator and is experimentally validated.
TL;DR: In this paper, a ytterbium-doped fiber laser with up to 1 kW of continuous-wave output power at 1.09 /spl mu/m with a slope efficiency of 80% and a good beam quality (M/sup 2/=3.4) is reported.
Abstract: A ytterbium-doped fibre laser with up to 1 kW of continuous-wave output power at 1.09 /spl mu/m with a slope efficiency of 80% and a good beam quality (M/sup 2/=3.4) is reported. The fibre was pumped by two diode-stack sources launched through opposite ends. No undesirable roll-over was observed in output power with increasing pump power.
TL;DR: In this paper, an internal planar inverted-F antenna (PIFA) is presented for the GSM, DCS, PCS, UMTS, HIPERLAN/2 and IEEE 802.11a bands within 2.5:1 voltage standing wave ratio.
Abstract: A novel internal planar inverted-F antenna (PIFA) suitable for handset terminals is presented. The structure combines shorted parasitic patches, capacitive loads and slots to achieve multiband operation. This compact antenna operates in the GSM, DCS, PCS, UMTS, HIPERLAN/2 and IEEE 802.11a bands within 2.5:1 voltage standing wave ratio (VSWR) and with good efficiency.
TL;DR: In this article, a high growth temperature step was used for the GaAs spacer layer, which significantly improved the performance of 1.3 /spl mu/m multilayer InAs/GaAs quantum-dot lasers.
Abstract: A high growth temperature step used for the GaAs spacer layer is shown to significantly improve the performance of 1.3 /spl mu/m multilayer InAs/GaAs quantum-dot lasers. Extremely low room-temperature continuous-wave threshold current densities of 32.5 and 17 A/cm/sup 2/ are achieved for a three-layer device with as-cleaved facets and high-reflectivity coated facets, respectively.
TL;DR: In this paper, a dual broadband rectangular slot antenna for 2.4 and 5 GHz wireless local area network (WLAN) is proposed, which uses a U-shaped strip inset at the center of the rectangular antenna.
Abstract: A novel dual broadband rectangular slot antenna for 2.4 and 5 GHz wireless local area network (WLAN) is proposed. With the use of a U-shaped strip inset at the centre of the rectangular slot antenna, the obtained impedance bandwidths for two operating bands can reach about 10.6% for the 2.4 GHz band and 33.8% for the 5 GHz band, which cover the required bandwidths of IEEE 802.11b/g (2.4-2.484 GHz) and IEEE 802.11a (5.150-5.950 GHz). Details of the antenna design and experimental results are presented and discussed.
TL;DR: In this article, the first demonstration has been made of the transmission of an audio signal via a THz communication channel using a recently developed room temperature semiconductor THz modulator which is based on the depletion of a two-dimensional electron gas.
Abstract: The first demonstration has been made of the transmission of an audio signal via a THz communication channel using a recently developed room temperature semiconductor THz modulator which is based on the depletion of a two-dimensional electron gas. A standard THz time-domain spectroscopy setup is modified to transmit signals up to 25 kHz over a 75 MHz train of broadband THz pulses.
TL;DR: In this paper, the dichotomous co-ordinate descent algorithm is proposed to solve the linear least-squares problem in real-time, which guarantees convergence to the true solution under realistic assumptions.
Abstract: Many iterative techniques are available to solve normal equations appearing in the linear least-squares (LS) problem However, because of multiplications and divisions they cannot be effectively implemented in real time A novel multiplication-free and division-free iterative technique, the dichotomous co-ordinate descent algorithm, which guarantees convergence to the true solution under realistic assumptions, is proposed
TL;DR: In this article, a field-plated AlGaN/GaN HEMTs on a sapphire substrate have been used to achieve record power performance at 4 GHz.
Abstract: Record power performance at 4 GHz has been obtained using field-plated AlGaN/GaN HEMTs on sapphire substrate. High power density (12 W/mm) as well as high efficiency (58%) have been measured. A comparison between devices with and without field plate on the same sample showed a significant reduction in knee-voltage walk-out for the field-plated device, thus enabling high power and efficiency operation.
TL;DR: In this paper, a coplanar waveguide-fed capacitive folded-slot antenna is proposed for the radio frequency identification (RFID) application at 5.8 GHz, where the antenna is fabricated on a 30×30 mm substrate.
Abstract: A coplanar waveguide (CPW)-fed capacitive folded-slot antenna is proposed for the radio frequency identification (RFID) application at 5.8 GHz. The antenna is fabricated on a 30×30 mm substrate. The measured bandwidth and antenna gain are 7.5% and 4.2 dBi, respectively. Radiation patterns are almost omnidirectional in the H-plane. These properties and the compact and uniplanar structure make the antennas suitable for use as RFID tags.
TL;DR: In this article, a high-speed coherent radar for dynamic testing of civil engineering structures is proposed, which operates a continuous-wave (CW) step-frequency in Ku-band, and the base-band signal is generated by direct digital synthesis.
Abstract: A high-speed coherent radar for dynamic testing of civil engineering structures is proposed. The radar operates a continuous-wave (CW) step-frequency in Ku-band, and the base-band signal is generated by direct digital synthesis. Vibration measurements carried out on a 200 m-long bridge forced by vehicular traffic are reported.
TL;DR: In this paper, a matching network is introduced to minimize the signal envelope correlation between two identical antennas spaced close to each other, and the optimisation criteria are derived from the expression of the correlation as a function of the scattering parameters.
Abstract: A matching network is introduced to minimise the signal envelope correlation between two identical antennas spaced close to each other. The optimisation criteria are derived from the expression of the correlation as a function of the scattering parameters.
TL;DR: In this paper, a 1.16 W continuous-wave front facet output optical power and 74% wallplug efficiency were achieved in 100 µm-aperture 1.06 µm-emitting laser diodes with 2-3 µmm cavity length.
Abstract: 16 W continuous-wave room temperature front facet output optical power and 74% wallplug efficiency were attained in 100 µm-aperture 1.06 µm-emitting laser diodes with 2–3 mm cavity length. The lasers are based on AlGaAs/GaAs/InGaAs quantum well asymmetric heterostructures with 1.7 µm-thick waveguide having 0.34 cm−1 internal optical loss.
TL;DR: An adaptive mode decision algorithm is presented, with rate-distortion optimisation that reduces complexity of the H.264 encoder without loss of image quality and compression ratio.
Abstract: An adaptive mode decision algorithm is presented, with rate-distortion optimisation that reduces complexity of the H.264 encoder without loss of image quality and compression ratio. The proposed algorithm uses the property of an all-zero coefficients block that is produced by quantisation and coefficient thresholding to effectively skip unnecessary modes. Experimental results show that the speed of the adaptive mode decision algorithm is two times faster than the full-mode decision algorithm of the JM72 reference encoder, without any coding loss.
TL;DR: In this paper, a planar inverted-F antenna with a T-shaped ground plane is presented, and the measured results of the proposed antenna show that by using a T shaped ground plane, the bandwidth of a PIFA can be broadened and the operation frequency can be reduced.
Abstract: A planar inverted-F antenna (PIFA) with a T-shaped ground plane is presented. The measured results of the proposed antenna show that by using a T-shaped ground plane, the bandwidth of a PIFA can be broadened and the operation frequency of the PIFA can be reduced. The relative measured bandwidth of the proposed antenna operating at 2.05 GHz band is 16.6%.
TL;DR: In this article, a Nakagami-m approximate distribution to the sum of M non-identical independent independent NN variates is derived, which finds applicability in important communications issues such as equal gain combining, signal detection, linear equalisers, outage probability, intersymbol interference and phase jitter.
Abstract: A Nakagami-m approximate distribution to the sum of M non-identical independent Nakagami-m variates is derived. Comparisons between exact and approximate sum distributions show excellent agreement. This new approach finds applicability in important communications issues such as equal-gain combining, signal detection, linear equalisers, outage probability, intersymbol interference and phase jitter.
TL;DR: In this article, the error performance of collaborative dual-hop wireless transmissions with maximal-ratio combining diversity is presented, using the well-known inequality between geometric and harmonic mean of positive random variables.
Abstract: The error performance of collaborative dual-hop wireless transmissions with maximal-ratio combining diversity is presented. Specifically, using the well-known inequality between geometric and harmonic mean of positive random variables, an upper bound for the end-to-end signal-to-noise-ratio is derived, and it is used to efficiently evaluate the average error probability.
TL;DR: In this paper, a single-feed circularly polarised (CP) microstrip antenna with relaxed manufacturing tolerances is presented, where a cross slot embedded on the radiating patch is used to increase the slot length ratio of the cross slot.
Abstract: A compact design of a single-feed circularly polarised (CP) microstrip antenna with relaxed manufacturing tolerances is presented. The CP operation of the microstrip antenna is achieved using a cross slot embedded on the radiating patch. By cutting an additional cross slot on the ground plane, not only the CP operating frequency can be decreased but also the slot-length ratio of the cross slot on the radiating patch can be considerably increased. In addition, the performance of the proposed design, such as CP bandwidth and peak gain, have no significant reduction.
TL;DR: In this paper, a split-step FDTD method with higher-order spatial accuracy is presented, which is proved to be unconditionally stable, and it is justified that the method achieves improved accuracy compared with lower-order cases and its dispersion error is comparable with the higherorder ADI-FDTD method.
Abstract: A split-step FDTD method with higher-order spatial accuracy is presented, which is proved to be unconditionally stable. From the dispersion analysis, it is justified that the method achieves improved accuracy compared with lower-order cases and its dispersion error is comparable with the higher-order ADI-FDTD method.
TL;DR: In this paper, a coupled-line coupler comprising a microstrip line, edge-coupled to a negative-refractive-index line, exhibits co-directional phase but contradirectional Poynting vectors on the lines, leading to backward coupling.
Abstract: A coupled-line coupler comprising a microstrip line, edge-coupled to a negative-refractive-index line, exhibits co-directional phase but contra-directional Poynting vectors on the lines, leading to backward coupling. A key feature of this coupler is that it can support complex coupled modes. The resulting exponential field decay enables enhanced coupling with moderate line lengths and spacing. An example 3 dB device has been implemented and tested at 3 GHz.
TL;DR: Experimental results show that the proposed method can efficiently save the computation cost for inter mode decision while maintaining the same PSNR and bit rate.
Abstract: A fast inter mode decision approach for H.264 coding standard is presented. The objective is to reduce the number of candidate block types in motion estimation. Experimental results show that the proposed method can efficiently save the computation cost for inter mode decision while maintaining the same PSNR and bit rate.