Design of sharp-rejection, compact, wideband bandstop filters

A general procedure is described to design a sharp-rejection wideband bandstop filter by using interference of the signals propagating through two parallel transmission line segments having different electrical lengths and characteristic impedances. Bandwidth and rejection level of the filters can be controlled by changing the impedances of the lines. A simple transmission line model is used for filter analysis. Design graphs are presented. Theoretical prediction is verified by fabricating two filters in microstrip technology. Good agreements is obtained among theoretical prediction, full-wave simulation and measurements.     

Wavelet-based ultra wideband pulse generator circuits

Aiming to generate ultra wideband (UWB) pulses based on wavelet packets, four different circuits are proposed. It has been shown that the wavelet packets are quasi-orthogonal and have almost identical time duration, and therefore appear to be valuable candidates for UWB pulse shape modulation systems. However, as with any technology, circuitry is an important challenge to solve before a theoretical application can live up to its full potential. The four proposed circuits are based on different interpretations of the equation defining the wavelet packets and their performance is investigated by computer simulation. The research also illustrates the characteristics and the consequent implementation advantages or issues afferent to each circuit.     

Left-handed L-band notch bandstop filter with significantly reduced size

An innovative compact microstrip line left-handed (LH) L-band notch bandstop filter is presented, validated by full-wave simulations and demonstrated by experiments, showing that the size of the filter can be significantly reduced by employing the LH transmission line (TL) metamaterials. The proposed notch bandstop filter was constructed using coupled line coupler loaded with 90deg LH TL. The size of the fabricated LH filter is 4.4 times smaller than that of the filter loaded with -270deg conventional TL and nearly two times smaller than that of the filter loaded with -270deg meandered TL. The filter has a centre frequency of 1.164 GHz and a fractional bandwidth of 0.51%. The loaded quality factor of the filter is 197, indicating 64 and 97% increases in comparison with the conventional and meandered TL filters, respectively     

Tunable slotted ground structured bandstop filter with BST varactors

This paper presents an investigation of a tunable bandstop filter (BSF) using slotted ground structure. A kind of open loop slot resonator is used for the bandstop response and its characteristics according to various dimensions are considered to decide a proper shape for the final design. A barium-strontium-titanate (BST) varactor chip is deployed to tune each resonator and its location is determined by electromagnetic simulation for an optimum frequency tuning. A three-pole tunable BSF of this type is measured at the centre frequency from 4.5 to 5.5 GHz and its rejection is more than 20 dB at the stop band while the insertion loss at the pass band is less than 1.5 dB.     

Directional modelling of ultra wideband communication channels

Ultra wideband (UWB) propagation is antenna-dependent, and multipath components experiencing specular diffraction or arriving at different angles have different shapes. To utilise the diversity of the multipath components, this study proposes a statistical model which incorporates directional parameters, such as elevation and azimuth angles by extending the IEEE802.15.3a model. Based on this model, a UWB directional simulator is developed. A novel multi-template subtractive deconvolution is applied to an extensive measurement campaign and simulated profiles. The use of multi-templates makes possible the directional estimation of the multipath components with a single receive antenna, and the use of subtractive deconvolution allows for the resolution of overlapping components and higher energy capture. Directional characterisation of UWB channels facilitates performance evaluation studies and achieves more accurate positioning, imaging and Rake receiver design.     

SIW窄带带阻滤波器的设计和仿真研究

基片集成波导(Substrate Integrated Waveguide—SIW)是一种新型的高品质因数、低损耗集成波导结构,易于设计和加工,可以广泛应用于微波毫米波集成电路中。由于和传统矩形波导的相似性,很多设计概念可以借用,比如波导功分器、滤波器、天线等,利用该结构设计出一种带阻滤波器,其中心频率为4.85GHz,相对带宽为1.2%,最大衰减为48dB。该滤波器具有体积小,容易加工和集成等优点。     

CPW-fed ultra wideband slot antenna with arc-shaped stub

An ultra wideband coplanar waveguide (CPW) fed slot antenna is presented. A rectangular slot antenna is excited by a 50-CPW with an arc-shaped tuning stub. For the proposed antenna, the 210 dB return loss bandwidth could reach 15.6 GHz (3.7-19.3 GHz), which is about 135% with respect to the centre frequency of 11.5 GHz. Details of the antenna design, simulation and measured results on the return loss and the E-and H-plane radiation patterns of the proposed antenna are presented.     

Dual layer stacked rectangular microstrip patch antenna for ultra wideband applications

An antenna consisting of a U-slotted rectangular microstrip patch stacked with another patch of a different size on a separate layer is presented and its performance results are investigated. An equivalent circuit model of this stacked patch design structure is also presented based on an extended cavity model to predict the input impedance. The theoretical input impedance is evaluated from this circuit model and the experimental results support the validity of the model. In this case, stacking with a simple patch adds another resonance to the antenna thus providing a wider bandwidth. The dimension of the top patch is optimised to achieve ultra wide bandwidth. A maximum impedance bandwidth of 56.8% is achieved using this structure, and the return loss |S₁₁|of the antenna is less than -10 dB between 3.06 and 5.49 GHz and the radiation patterns are found to be relatively constant throughout the band. A coaxial feed with Gaussian modulated pulse is used for this antenna.     

Reconfigurable patch-antenna design for wideband wireless communication systems

An effective design of a reconfigurable patch antenna, with a wide operational bandwidth for wireless communication and radar systems, is presented in this paper. The reconfigurable patch possesses an E-shaped structure and its operation frequency can be changed by integrated switches. The operational frequency of the antenna can cover an octave frequency range by utilising only two switch states. In state 1, the antenna operates from 9.2 GHz to 15.0 GHz and, in state 2, from 7.5 GHz to 10.7 GHz. Relative bandwidths of 48% and 35% are obtained in the two states, respectively     

Power delay profile modelling of the ultra wideband off-body propagation channel

This study presents a statistical power delay profile (PDP) model for the evaluation and design of ultra wideband (UWB) off-body communication systems. The analysis is based on extensive real-body measurements carried out in the frequency range between 3.5 and 6.5 GHz. Due to the dependence of the radio propagation channel on the body region (i.e. front, side and back), we gradually develop separate stochastic tapped-delay-line models for each body region. Based on the newly estimated parameters, channel simulation methods are provided for each of the proposed models. Finally, several comparisons between the empirical data and the simulations results are presented, by means of key properties of the recorded PDP profiles.     

Weighted high data rate ultra wideband transmitted-reference system in dense multipath fading channels

A novel weighted high data rate single-user ultra-wideband transmitted-reference (UWB-TR) system is proposed and its performance in log-normal slow fading channels is investigated, which has not been addressed before. This system employs a novel signalling scheme, which provides a nearly inter-symbol interference (ISI) free-channel response at the receiver and eliminates the need for equalisation. It also enhances the reference pulse quality by employing optimum power allocation. The performance of the proposed system is compared with that of the differential transmitted-reference (DTR) system in IEEE 802.15.3a Channel Model 1 (CM1) both analytically and via simulations by taking into account noise, log-normal slow fading, inter-path/pulse interference (IPI) and ISI. Both analytical and simulation results show that our system significantly outperforms the DTR one. It is shown that the proposed method is robust against small changes in both weighting coefficients and integration interval, whereas the UWB-DTR scheme is too susceptible to such changes in the integration interval.     

Effect of clock offset on an impulse radio ultra wideband ranging system with comparators

Impulse radio ultra wideband (IR-UWB) can achieve high resolution in ranging because it uses a very short pulse with a duration of less than 1 ns. In order to reduce cost and power consumption, a ranging system with high-speed comparators has been proposed. In this system, it is necessary to reduce noise power through averaging the comparator outputs. The authors evaluate the effect of clock offset on the averaging process, and a two-stage averaging scheme for the IR-UWB ranging system is proposed. Through computer simulation, it is proved that the proposed scheme can reduce the effect of the clock offset with appropriate numbers of initial averaging.     

Moving target detection using super‐resolution algorithms with an ultra wideband radar

We present subspace based detection algorithms for detecting moving targets applied to the data collected by an ultra wideband radar system. Combining the results of time reversal MUSIC algorithm and delay estimation MUSIC methods resulted in successful localization of targets. We have investigated methods to resolve the ambiguities in target detection and we performed experiments using two targets to test the effectiveness of the algorithms. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 237–244, 2010     

基于新型对偶复合左右手传输线的高性能带阻滤波器设计

 利用交指螺旋线结构和枝节贴片设计了一种新型对偶复合左右手传输线结构.采用电磁全波仿真软件和Bloch-Floquet 理论对其进行研究,计算并提取了其色散曲线,研究结果表明该对偶复合左右手传输线结构具有良好的带阻特性,并且阻带内2个传输零点独立可控．在此基础上采用2个单元结构级联的方式设计了一款具有小型化特性的性能优越的带阻滤波器,进行实物加工并使用适量网络分析仪测试,测量结果与仿真结果吻合较好,表明所设计的带阻滤波器中心频率为3.56 GHz,阻带带宽为39.3%,阻带矩形度为0.85,通带带宽为4.47~8.42 GHz,整体性能优越．此外所设计的带阻滤波器整体尺寸为0.237λ×0.145λ（λ为中心频率在自由空间波长）,小型化优势明显．     

Development of ultra wideband, high efficiency, distributed power amplifiers using discrete GaN HEMTs

This study describes the design and performance of a discrete ultra wideband GaN HEMT distributed power amplifier (DPA) with over 5 W (37 dBm) output power and a PAE exceeding 27 in the 0.02-3 GHz frequency range. The implemented DPA design is comprised of three discrete GaN HEMT devices. Its performance was enhanced using tapered drain lines and non-uniform gate capacitive coupling. The design methodology is based on both small and large signal analysis using harmonic balance technique, and their associated predicted and experimental results are discussed here in detail.     

A new filter design technique for coded excitation systems

To increase range resolution and produce acceptable range sidelobe levels, filtering techniques rather than direct complex correlation are applied in coded excitation systems. A filter design technique based on both peak sidelobe levels and minimum sidelobe energy criteria is developed. In comparison to a classic inverse filter, this approach reduces sidelobe levels under a prespecified threshold. Further reduction can be achieved by extending the filter length. This technique can be more generally applied to similar signal processing problems. Both the mathematical formulation and simulation results demonstrating the utility of the technique are presented. A discussion of quantization effects is included.     

Design and experimental verification of terahertz wideband filter based on double-layered metal hole arrays

A terahertz wideband filter based on double layer metal hole arrays is designed in this paper. A metal hole array is perforated on a metal layer with a square array of circular air holes. The transmission characteristics of the electromagnetic waves through the metal hole array can be determined by the accumulation of in-phase scattering, spoof surface plasmon polaritons, and waveguide modes. The transmission spectrum is tuned by adding another identical layer metal hole array, and a wideband filter can be formed accordingly. Samples containing double-layered metal hole arrays were fabricated by micromachining technology. A wideband filter with center frequency located at 0.8 THz and FWHM reaching 400 GHz was experimentally achieved.     

Model-based phase velocity and attenuation estimation in wideband ultrasonic measurement systems

A parametric method to estimate frequency-dependent phase velocity and attenuation is presented in this paper. The parametric method is compared with standard nonparametric Fourier analysis techniques using numerical simulations as well as real pulse-echo experiments. Approximate standard deviations are derived for both methods and validated with numerical simulations. Compared to standard Fourier analysis, the parametric model gives considerably lower variance when estimating attenuation and phase velocity. In contrast to nonparametric techniques, the proposed estimator avoids the phase unwrapping problem because analytical expressions for the continuous phase velocity and attenuation can be derived.     

0.9 V low-power switched-opamp switched-capacitor bandpass filter for electroneurography acquisition systems

A 0.9 V fully differential switched-opamp-based sixth-order switched-capacitor bandpass filter, which has frequency response centred at 1.118 kHz with a Q of 0.235 and power saving by a proposed low-power biquad structure, is designed for electroneurography acquisition systems. It is implemented in a 0.18 mum CMOS technology with a normal threshold voltage of 0.48 V. The measured peak signal-to-noise ratio is 52 dB at 1 kHz sinusoid wave with input amplitude of 1 V_pp. In addition, the measured power-supply rejection ratio and common-mode rejection ratio are >40 dB in the desired bandwidth and have peak values of 70 and 67 dB, respectively. A dynamic range of 50 dB for total harmonic distortion of 3% is obtained while dissipating 262 muW and occupying a chip area of 0.35 mm².