A broadband omnidirectional distributed antenna is studied theoretically and experimentally. By loading three shorted coupling patches over the top of the radiation patches and a circular sleeve on the ground plane, the bandwidth of the antenna which is excited by a truncated cone feeding structure is significantly enhanced. Results show that an impedance bandwidth of 152% ranging from 0.97 to 7.09 GHz is achieved. Omnidirectional radiation patterns in the horizontal plane, low cross polarisation level, and stable antenna gain ranging from 2.1 to 7.3 dBi are realised over the operating band, which suggests the distributed antenna can be widely used in indoor wireless communication systems.

A feeding antenna that uses a rectangular waveguide with a patch on it to equalise the principle planes is proposed. The patch is printed on a substrate grounded with shorting pins. Typically, corrugated horn antennas are used for feeding antennas, but they are expensive because of the complex fabrication process. In comparison, the proposed antenna is inexpensive because it uses a rectangular waveguide and a dielectric substrate. The simulation and experimental results gave similar 10 dB beamwidths, while the beamwidth of the conventional waveguide was markedly different. The proposed antenna could be used as a feeding antenna for reflectors at low cost.

A quantitative intestinal motility (IM) assessment method based on a benchmark model using Legendre fitting of bowel sound spectrum is presented. The logarithmic magnitude of bowel sound sets containing IM events is decomposed into Legendre polynomial series to create the benchmark. For a bowel sound data segment under assessment, the relative spectrum fluctuation and correlation with the benchmark model are calculated and quantitative assessment can then be obtained. Experimental results have proven the accuracy of the proposed method.

The use of microwave photonics in the form of an optical link to transmit and receive microwave signals in microwave biomedical imaging systems is proposed. A single fibre is used to replace coaxial cables connecting the antenna array to the transceiver. The optical link, which is lightweight and offers an almost zero insertion loss, improves the signal-to-noise ratio and sensitivity, and thus offers better detection and localisation. As a proof of concept, an optical link that consists of a vertical-cavity surface-emitting laser, a multimode fibre and a high speed photo detector was built and tested. Experiments were performed using a 1–4 GHz microwave imaging system to scan a head phantom, which consists of accurately emulated brain tissues and embedded stroke. The head was imaged and the results were compared with those obtained using the traditional all-microwave link. The results demonstrate that the optical link increases the signal-to-noise ratio of the system and thus improves the quality of the obtained images and accuracy of the detection and localisation.

High quality fully integrated power supplies could notably improve the performances of the noise-sensitive building block in the UWB communication systems. Double buffers are inserted into the cascode flipped-voltage-follower (FVF) topology to enable designing the dominant pole at the output node for better power supply rejection (PSR) and less voltage variation during load transient. An enhanced super source follower (E-SSF) is proposed to further reduce the output impedance of the buffer that drives the power transistor. The FVF-based low dropout regulator (LDO) with E-SSF achieves a worst-case PSR of −18.9 dB across the full spectrum and a transient response time of 312 ps. The proposed LDO is designed in a 28 nm CMOS process and consumes 100 μA quiescent current with 1.0 V input and 0.8 V output voltages. In total, 120 pF on-chip capacitors are used for filtering.

A Volterra model is used to calibrate a pipeline ADC simulated in Cadence Virtuoso using the STMicroelectronics CMOS 45 nm process. The ADC was designed to work at 50 MSps, but it is simulated at up to 125 MSps, proving that calibration using a Volterra model can significantly increase sampling frequency. Equivalent number of bits (ENOB) improves by 1–2.5 bits (6–15 dB) with 37–101 model parameters. The complexity of the calibration algorithm is reduced using different lengths for each Volterra kernels and performing iterative pruning. System identification is performed by least squares techniques with a set of sinusoids at different frequencies spanning the whole Nyquist band. A comparison with simplified Volterra models proposed in the literature shows better performance for the pruned Volterra model with comparable complexity, improving linearity by as much as 1.5 bits more than the other techniques.

The design of a new bit-line sensing scheme of SRAM memories is presented, which combines offset cancellation and compensation solutions. FCMOS inverters, brought to operate in their maximum gain region, are used to compensate the systematic offset of the sense amplifier and reduce the sensing delay. Systematic offset of the inverter amplifiers is cancelled by means of equalising feedback connections. A simulation analysis in Cadence environment and TSMC PDK demonstrates the very good potential of the proposed solution when it is compared with the recent and the established literature.

This Letter presents a fine-grained hardware switching scheme to choose from the proper hardware for low power computing. It exploits the word-length optimisation opportunities for multiplication unit. With the proposed technique, the gate-level simulation result on OpenRISC shows 23.7% power reduction for the multiplication unit, which accounts for 9.5% power reduction for its execution unit.

A cross-gramian-based frequency-weighted model/controller-order reduction technique is proposed for single-input single-output and symmetric MIMO stable systems. The proposed algorithm does not require the original system to be minimal. Numerical examples are presented to show the effectiveness of the proposed technique.

A low-power visual sensor for low-light 2D imaging, proximity sensing, and 3D depth imaging is presented; it is applicable to smart sensing applications such as user recognition under dark conditions, gesture sensing, and extended user interface/user experience (UI/UX) in mobile devices. With integrated background suppression circuits, the sensor provides in-situ proximity sensing that generates a background-cancelled proximity map while capturing 2D images. In addition, 3D depth images are provided based on stereo matching with two 2D images from the visual sensor and the existing camera module. The prototype sensor was fabricated with a 0.11 μm 1P4M CMOS image sensor (CIS) process. The power consumption is 1.98 mW (at 15 fps) from the sensor and 9.38 mW (at 16 ms on-time) from the infrared LED.

A new early gesture recognition system that uses different features obtained from MYO sensor is presented. The beginning part of each gesture is detected and used by the system to train the authors’ recognition algorithm. To preserve the different features temporal alignment for each movement, two-dimensional (2D) principal component analysis was employed to obtain the dominant features by processing the obtained data in its 2D form. Canonical correlation analysis (CCA) is used to find a space where the projection of similar training testing pairs becomes highly correlated. Finally, the testing sequence is matched to the training set that gives maximum correlation in the new space obtained by CCA. Low processing complexity, storage requirement, accurate and fast decision obtained on the newly collected data set are factors that promotes the authors’ algorithm for real-time implementation.

A new class of augmented map application is introduced which can provide detailed knowledge about any area, to a user. This brief particularly focuses on obtaining itinerary perception subject to different environmental conditions. This refers to extraction of traffic related information from an augmented map. The problem is modelled as a machine learning technique where the traffic distribution at different times (including same days, different days and different weather) are observed continuously using a service robot. This data is posed as a Gaussian process for post-estimation. Our system consists of a vision sensor which will acquire the region of interest input, queried to a database of traffic density distributions, learned from the scenes at different points of time. The user interacting with the system will obtain an information pertaining to the region conditioned on environmental and timing events.

It is shown that for systems with no zeros and no complex poles, the classical estimate of the 3 dB cutoff frequency based on the sum of the zero-value time constants (ZVTs) is always conservative. A non-trivial upper bound on the cutoff frequency which depends only on the sum of the ZVTs and the system's order is also derived. It is demonstrated that both bounds are tight – specifically, the lower bound is approached by making one of the system's poles increasingly dominant, whereas the best possible bandwidth is achieved when all of the system's poles overlap. The impact of complex poles on the results is also discussed.

A new coding scheme called radix conversion variable length code (RCVLC) is proposed to represent non-negative integers from small values to very large values. RCVLC obtains lowest code length to represent mid-range and large-range integers than Fibonacci code, Elias codes and other existing schemes. This RCVLC is applied as an entropy coder of the Burrows–Wheeler Transform data compressor to compress Calgary corpus which contains both binary and text files. It is observed from the experimental results that the new RCVLC obtains better compression than the existing coding schemes on an average.

A wideband filtering power divider (FPD) with good isolation and widen upper stopband is presented. A distributed stepped-impedance resonator (SIR) network composed of three short-circuited SIRs and one isolation resistor is introduced to obtain both port-to-port isolation and harmonic suppression. For demonstration, an FPD operating at 2.3 GHz with 3 dB fractional bandwidth of 31% is designed, fabricated and measured. In the operating band, the measured isolation is better than 17 dB, while out of band, the upper stopband is extended to 9.8 GHz (4.2f ₀) with a rejection level of 20 dB.

A new microstrip wideband filtering power divider (FPD) is presented. By selecting proper coupling topology between a λ/4 short-ended microstrip transmission line and two multimode resonators, a wideband FPD is initially constructed. Meanwhile, by wisely introducing an isolation resistor between the resonators, good port-to-port isolation of the FPD is obtained. For validation, one prototype wideband FPD operating at 2.24 GHz with the fractional bandwidth of 32.1% is designed, fabricated, and measured. Results indicate that the presented FPD exhibits not only a high-frequency selectivity performance with the help of two out-of-band transmission zeros, but also better than 22.5 dB isolation within the entire operation band.

The design and characterisation of two different power divider techniques, i.e. Y-branch and multimodal power dividers, based on subwavelength dielectric fibre technology is presented. Both have been successfully established in the optical domain for dielectric waveguides and are adapted to W-band frequencies (75–110 GHz). Both power dividers are made out of the cross-linked polystyrene Rexolite 1422 and have been processed by milling. Simulations predicted insertion losses between 3.5 and 4 dB while the electrical characterisation showed insertion losses between 3.5 and 5 dB. The multimodal power divider has the best performance with 1–1.5 dB lower insertion losses compared with the Y-branch divider.

The RF design of stub-loaded-based wide-band bandpass filters (BPFs) with multiple tunable rejection bands in their transmission range is presented. The proposed concept exploits the replacement of the short-circuited resonant stubs of the stub-loaded-based BPF with multi-band bandstop (BS) sections. Each multi-frequency BS section is formed by several in-parallel-cascaded 90°-long stubs that are terminated by frequency-agile resonators so that each of them results in an independently-controlled transmission zero. In this manner, a plurality of high-order reflective-type rejection bands can be created and arbitrarily controlled. Further operational characteristics include: (i) scalability to any number of rejection bands and degree of selectivity, (ii) independent tuning of each notch without any influence on the remaining ones, and (iii) spectral-merging of multiple stopbands to increase their bandwidth (BW) and enable controllability of the number of active notches in the passband. The aforementioned principles are experimentally validated through a prototype that exhibits a wide-band (fractional BW: 68%), low-loss (<0.7 dB) passband at 1000 MHz and two high-attenuation (>60 dB) notches that can be independently tuned within the 870–1150 MHz range.

A screen-printed mechanical switch based on an electrode structure on stretchable polyurethane (PU)-foam film, Platilon U 4021, combined with a piezoelectric actuator, Smart Material MFC M-4010-P1, is proposed. The minimum actuation voltage of the prepared component is 300 V. The measured resistance was 2 Ω while closed and >0.5 TΩ when open. The electrode structure endured on average of up to 15.5 M cycles with movement ≥100 times greater than the ≤1 µm required for actuation. The results suggest that the switch could be advantageous for various e-textile applications.

A novel optical comparator is proposed for the novel Viterbi-decoding scheme, and the performance of the proposed scheme with the optical comparators is analytically investigated. The net coding gain of the proposed scheme is not degraded compared with conventional scheme, and the proposed scheme could reduce the calculation steps by a factor of ∼4/5 of the conventional scheme.

The effects of crystallographic orientation on the ferroelectric properties of Pb(Zr,Ti)O₃ (PZT) thin films grown on (111) and (100)-oriented Pt substrates are investigated. The effects of doping PZT with species X (forming PXZT) thin films (Pb:X:Zr:Ti, 113:3:30:70; X = La, Nb, or Y) using chemical solution deposition were studied. The crystallinity of all PXZT films was almost identical. The remnant polarisation of the un-doped, La-, Nb-, and Y-doped PZT capacitors with Pt(111) bottom electrodes were 133.4, 64.7, 60.2, and 98.4 µC/cm², respectively. In ferroelectric capacitors with Pt(100) bottom electrodes, the remnant polarisations were 185.6, 148.1, 103.1, and 135.7 µC/cm², respectively. The remnant polarisation was larger with Pt(100) than with Pt(111). The initial remnant polarisation of the un-doped PZT capacitors was larger than that of PXZT.

High-power terahertz quantum cascade lasers at −97.4 μm based on coplanar waveguide epitaxial-side down (Epi-down) mounting technique are presented. With the improved thermal management, excellent performance is obtained for the Epi-down mounted lasers. The maximum output powers of 685 mW in pulsed mode and 164 mW in continuous-wave (C-W) mode are realised at 10 K. The maximum C-W wall-plug efficiency of 1.67% is also realised. Fundamental lateral mode emissions are achieved for wide ridge lasers through a mode loss differentiation process.

In this Letter, a novel high step-up converter based on inductor-capacitor structure is proposed. Utilising switched capacitor to increase the voltage across inductor-capacitor structure, and by parallel charging and series discharging of inductors and capacitors, the voltage gain of the converter is improved greatly. This method can reduce duty ratio and current ripple of power switches, and hence circuit loss of the converter can be decreased. This Letter discusses topological structure and operating principle of the proposed converter. Performance comparison with other converters is presented to prove the high voltage conversion advantage of the proposed converter. Experimental results are provided to verify feasibility of the converter and correctness of the theoretical analysis.

A novel soft-switching step-up/down DC–DC converter is proposed, which generates symmetric bipolar outputs while maintaining the grounded capability. The proposed converter consists of a zeta converter cell and a buck–boost converter cell, sharing an inductor and a power switch. High efficiency is achieved by zero voltage switching for all switches. Meanwhile, by connecting one load between positive and negative output terminals, high voltage gain can be achieved. Experimental results of a 3.7 V battery input and ±10 VDC/10 W outputs prototype are presented to verify the analysis results of the proposed converter.

The isotropic reflectivity assumption is a valid approximation in traditional narrow-angle synthetic aperture radar (SAR). However, for large angular ranges most targets exhibit only limited scattering persistence. Therefore, this assumption is violated in circular-SAR (CSAR). Thus, the performance of traditional fully coherent image formation is poor in CSAR, because coherent integration over the entire aperture will obscure aspect-independent reflectivity characteristics. To address this problem, an adaptive imaging algorithm which accommodates anisotropic targets to improve image quality is proposed. The efficient use of valid azimuth angles can reduce noise and errors and highlight anisotropic targets in CSAR image. Another advantage of this algorithm is that the anisotropy target scattering behaviour can be extracted by data inversion in the imaging process. Compared with the sub-aperture approach, which can also extract the anisotropic scattering properties of target, the data inversion approach in the algorithm can provide more accurate results and a finer curve. The adaptive imaging method is validated in this Letter by simulation and an airborne dataset.

GaN planar Schottky barrier diode (SBD) with an n⁻/n⁺ structure was grown and fabricated on sapphire substrate. An n⁺ GaN epitaxial layer with doping concentration of 8 × 10¹⁸ cm⁻³ was employed to reduce the parasitic resistance. An air-bridge structure and 50 μm substrate thinning-down technique were adopted in order to reduce the parasitic capacitance. A record cut-off frequency (f _c) of 902 GHz was achieved for GaN planar SBD with 2 μm anode diameter.

A double sparse learning (DSL) model with a pyramid structure-based feature extraction scheme to handle speech emotion recognition (SER) problem is proposed. The key novelty of the method is that the proposed DSL model is able to take into consideration two scales of the pyramid structure-based features for selecting the features which have great contributions to SER. Extensive experiments on eNTERFACE and AFEW emotion databases to evaluate the method are conducted. The experimental results demonstrate that, compared with some recent competitive methods, DSL with the pyramid structure-based feature extraction scheme has a more promising performance in dealing with the SER task.

When developing and validating algorithms and protocols for wireless sensor networks, simulations provide valuable insights that would be impractical to gather from real world experimental deployments. For these simulations to be meaningful, realistic models of the way energy is consumed in the targeted sensor devices need to be produced. A number of inaccuracies are identified to avoid when constructing simulation energy models and in doing so draw attention to a device specific behaviour with the potential to invalidate research assumptions.

A novel energy efficiency (EE)-oriented cognitive spectrum sharing scheme in heterogeneous cognitive radio networks, called energy-efficient cognitive cooperation (ECC) is proposed, in which the primary system release a part of its radio spectrum to the secondary system in exchange for secondary user (SU) served as a relay to assist the transmission of the primary user (PU) traffic. On the basis of ECC scheme, an EE maximisation non-convex problem for SUs is formulated under the circuit power consumption and the QoS requirements as well as power constraints. By virtue of parametric Dinkelbach's algorithm and golden section search method, an efficient resource allocation algorithm is developed. Simulation results show that our proposals attain significantly higher EE compared with the non-cooperation transmission without sacrificing the performance of PU's QoS, and thus, a ‘win-win’ situation is achieved.

A principal component analysis-based blind wideband spectrum sensing (WSS) algorithm is presented, in which the WSS issue is transformed into a sequential binary hypothesis test under the framework of the general likelihood ratio test. The proposed method operates simultaneously over all the subbands rather than one single subband each time. Furthermore, the new method overcomes the noise uncertainty problem, and can also perform well without information about the channel, the primary signal, and the noise power. Most importantly, unlike the existing classical blind wideband detectors based on the information theoretic criterion, the decision threshold for the proposed detector can be flexibly determined according to the target false-alarm probability. Simulation results verify its effectiveness and superiority to the existing sensing algorithms.