An innovative sound transmission system for an intuitive service utilises the human body as a sound transmission medium. By using the human body as a transmission medium, sound generation in the body and sound transmission through the body can be achieved at the same time. Sound generation in the body is based on the nonlinear characteristics of the human body. Two ultrasonic waves with different frequencies produce an audio signal at the difference frequency of the two waves during the propagation process due to the nonlinearity of the body. By substituting a transmission line with the human body, wireless sound transmission is achieved. This system does not require sound transmitters and the sound transmission line required in the conventional earphones. Users can hear sound without sound transmitters and a transmission line by touching the system without making any other noise outside.

The element pattern reconstruction method is proposed to calibrate the mutual coupling effect of conformal antenna arrays. The calibration matrix due to the proposed calibration method is obtained through the transformation of element patterns rather than the analysis of currents or voltages on the antenna array, which is different from previous calibration methods. The new method can provide effective mutual coupling calibrations for conformal antenna arrays. A conformal microstrip array is designed to verify the effectiveness of the new calibration method.

A novel compact antenna is designed on a low-loss ceramic material to support multiband operation as well as to reduce the antenna size. Three monopole antennas with a single feed are designed and combined for wireless device applications, occupying only 10 × 10 × 3 mm³. Structurally, orthogonal placement of the three monopoles provides a relatively simple design process. Across the entire bands of interest, it is shown that more than 50% of the incident energy radiates into free space. Detailed analysis and measurement results are presented.

A simple topology is described for radio frequency identification (RFID) tags mountable on metal surfaces. The tag is built around a commercial UHF RFID module combining an IC and a coupling loop. The module is placed in the neighbourhood of a slot which is used both to couple the energy from the module to the patch-like antenna and to miniaturise the tag. A read range of almost 4 m is obtained in the 865–868 MHz band with a 1.6 mm low-cost FR4 substrate.

A method and formulae for correction of the sidelobe level of the radiation pattern of a high gain antenna when measured in the Fresnel region are presented. After a thorough analysis of a large number of different cases, trend curves have been computed and an empirical formula has been derived, which allows the correction of the measured values of the sidelobes when the measurement range is below or around the far-field distance.

A novel ground plane with a meander line is proposed for the design of a compact slot antenna. By using this new design, size reduction for the slot antenna can be realised. By embedding a meander line into the ground plane of the slot, it is observed that the resonant frequency of the slot antenna significantly decreases, which can lead to a large size reduction for fixed-frequency operation. In this case, the measured bandwidth of the proposed antenna is comparable with that of the reference antenna.

A tight upper bound on pattern correlation for multi-port antennas is derived. It is valid for lossy antennas and an arbitrary number of ports. As opposed to previous work, the present derivation is based on modal analysis, considering the spectrum of the radiation matrix. The new approach yields a much tighter upper bound on pattern correlation than previously available from per port characterisation of multi-port antennas. The result suggests that pattern correlation is generally small for reasonably well-matched antenna systems and therefore hardly ever relevant as an independent design criterion. Numerical results for simple model structures corresponding to 2-port, 3-port and 4-port multiple input–multiple output antennas are given to illustrate this conclusion.

A tunable lens-coupled annular-slot antenna using a Schottky varactor diode has been designed, fabricated and characterised at 140 to 220 GHz. Simulation results show that the resonant frequency of the annular-slot antenna can be effectively tuned by varying the capacitance of the imbedded varactor diode, with an average tunability of ∼2.5 GHz/fF. Prototype demonstration using a varactor with zero-bias capacitance of 3.8 fF has shown a frequency tuning range from 197 to 202.7 GHz by varying the diode DC bias voltage from 1 to −5 V (corresponding to a diode capacitance change from 4.97 to 2.4 fF). The measured tunability is 2.22 GHz/fF, which agrees well with simulation. Projections indicate tuning ranges of ∼50 GHz in the G-band should be possible using varactor diodes with ∼20 fF zero-bias capacitance.

A novel simple approach is presented for designing a broadband single layer substrate printed log-periodic dipole array (PLPDA) antenna by using microstrip technology. The PLPDA antenna has the merits of wide bandwidth, low profile and light weight, which should be fed by the balanced line. The balanced line, created by the geometric features of the microstrip, provides a balun with a considerably wide bandwidth with low profile, broad bandwidth and low insertion loss etc. The prototype of the proposed microstrip printed log-periodic array at Ka band is designed and fabricated; the measured data are in good agreement with the simulated results.

Multi-parameter patient monitors (MPMs) have become increasingly important in providing quality health care to patients. A high alarm accuracy (sensitivity) will need a lower threshold for alarm detection which will lead to lower no-alarm accuracy (specificity) and vice-versa. MPMs when used in an intensive care unit (ICU) need to have high sensitivity. However they need to have high specificity when used in in-patient wards for regular health check-ups. Proposed is a novel algorithm to trade-off specificity for sensitivity and vice-versa depending on the application. The proposed method is referred as detection error trade-off, trade-off specificity for better sensitivity and vice-versa. The algorithm will help to extend the application of MPMs from ICUs to in-patient wards and thus enhance the quality of health care. Experiments have been conducted with an MPM using the classification and regression tree algorithm. By using the proposed algorithm, an improvement of 10.18% in sensitivity was obtained by trading-off 0.40% in specificity. Furthermore, the overall performance of the refined system is 1.15% better than the baseline system.

A wideband low-noise amplifier (LNA) for long-term evolution applications is presented. A capacitive cross-coupled common-gate in combination with current-bleeding common-source topologies is adopted for wideband input matching, high gain and low noise figure (NF). Inter-cascade inductors are adopted to cancel the inter-stage parasitics, which extend input matching and operational bandwidth to higher frequency with additional NF reduction. Implemented in a 0.18 µm CMOS technology, the proposed wideband LNA shows a voltage gain of 17 dB, a NF of < 2.5 dB, |S ₁₁| of higher than 10 dB and a maximum IIP3 of + 1.52 dBm over the frequency range of 0.7–2.7 GHz while consuming 7.5 mA from a 1.8 V supply.

A novel type of analogue multiplier-cum-divider is described. A square waveform of period T which is proportional to V ₂/V ₁, where V ₂ and V ₁ are the two input applied voltages, is generated. Another input voltage V ₃ is integrated during the period T. The peak value of the integrated output is V ₂ V ₃/V ₁.

A near-threshold charge pump circuit suitable for a phase-locked loop-based frequency synthesiser is presented. The charge pump uses gate switches and dual feedback loops to achieve good up/down current matching characteristics in low-voltage operation. The applied gate switches reduce the leakage current and the feedback loops provide a more stable operation. Post-layout simulation results demonstrate that the proposed charge pump circuit consumes only 60 µW with a 0.5 V supply voltage. The charge pump circuit is implemented in a 0.13 µm CMOS process.

A new approach to reducing leakage power in network-on-chip buffers is presented. The non-uniformity of buffer utilisation is leveraged across the network and power-gating is applied to scarcely utilised buffers. Instead of turning-off the buffers completely, a buffer portion is kept turned-on. This design choice has a significant performance benefit because the buffer is always able to receive network packets. Design aspects and trade-offs in a 45 nm CMOS technology are discussed and results obtained over video application benchmarks are presented. It is shown that it is possible to reduce buffer leakage by 40% without performance penalty.

A parameterised and scalable very large scale integration (VLSI) soft intellectual property (IP) is presented that can be implemented in programmable logic devices, such as field programmable gate arrays (FPGAs) or a system-on-chip design for efficient sparse approximation. The proposed architecture is optimised based on the orthogonal matching pursuit algorithm by both algorithm reformulation and architecture resource sharing techniques. The soft IP core supports a floating-point data format with 10 design parameters, which provides the necessary flexibility for application-specific customisation. The soft IP is evaluated on various FPGA platforms. The evaluation results show that design can achieve up to 30% higher throughput than the existing solutions while offering a larger dynamic range capability and better design flexibility.

An adaptive impedance tuning circuit (AITC) is used to compensate for the impedance between the arbitrary load impedance and the characteristic impedance of interest. An AITC is required for correct and accurate load impedance measurements. A new type of mismatch measurement circuit that measures the arbitrary load impedance more accurately is proposed and its performance against existing methods is compared. The proposed circuit exhibits a significant performance improvement compared with the conventional method, and it could be applied to different communication systems that have a variety of input signal strengths.

A low-complexity twiddle factor generation structure for fast Fourier transform (FFT) is proposed. In FFT, twiddle faction generation and multiplication occupies more area than the other mathematical operations. The proposed structure reduces the twiddle factor generation part by removing the redundancies in the conventional structure and compressing the twiddle factor ROM contents. With the proposed structure, the twiddle factor generation part is reduced by 32–45% compared with that of the conventional structure.

A pipelined phase accumulator (PACC) for direct digital frequency synthesisers (DDFSs) is presented. A highly pipelined structure is inevitable in a PACC design to achieve high-speed performance, which causes a large number of pre-skewing flip-flops (F/Fs) and leads clock signals to be a large source of power dissipation. Since the input data do not change every single cycle, clock gating can save power by decreasing the number of unnecessary clock switching in the pre-skewing F/Fs. Sequential clock gating for pipelined PACCs is proposed. Compared with the conventional pipelined PACCs with and without clock gating, the proposed scheme reduces power dissipation by up to 55.4 and 77.2%, respectively, for the 32-bit 8-pipeline-stage PACCs.

A memristance enhancement method using an external voltage source is proposed. The proposed method is suitable for circuit implementation due to the tunability of the external voltage source. Numerical results show a memristance enhancement and an enlarged hysteresis eye-openness of current–voltage characteristics.

A novel switched-capacitor bandgap voltage reference circuit is presented that dispenses entirely with the use of resistors. Since capacitors are used instead of resistors, variability problems from devices mismatch and process spread are reduced, compared with traditional topologies. The proportional-to-absolute-temperature drift and the complementary-to-absolute-temperature drift voltages are both generated by the same PNP vertical bipolar transistor obtained in bulk CMOS, minimising mismatch problems even further. A switched-capacitor circuit stores, amplifies and sums these voltages, generating the bandgap voltage after five clock cycles. The operational amplifier offset voltage is also cancelled by the switching scheme proposed. The current sources which are used to generate different junction current densities are averaged in the switching process, reducing their mismatch impact on the circuit performance. A systematic comparison to a traditional bandgap topology with resistors is presented, both designed in the CMOS 180 nm process, and demonstrates the better performance of the new topology with respect to the former. Monte Carlo simulations show significantly lower spread resulting from devices mismatch in the output reference voltage (V _REF) and also in its temperature coefficient.

An efficient genetic algorithm-based robot path planning method is proposed that finds collision-free paths while minimising the distance of the paths obtained. By using an improved evaluation and natural selection process, the proposed robot path planning method provides markedly faster computation and better success rates than well-known conventional methods.

Humidity is a very important factor in representing the severity of electrostatic discharge (ESD). Low humidity indicates high risk of ESD problems; high humidity indicates low risk of ESD problems. Both relative humidity and absolute humidity can represent the level of humidity: which one is more important? The reported measurement result shows that relative humidity is more important in the discharge phase. The qualitative analysis is given.

There are many ways to accurately estimate the low-frequency region of the primary quantisation table in a double compressed JPEG image with different quality factors. However, they cannot accurately estimate the high-frequency region. An image compression model to describe the relationship between the primary compression and the second compression is used to present a simple approach to accurately estimate the whole primary quantisation table, and based on this, an efficient method for detection of image tampering involving JPEG recompression is proposed. The effectiveness of the proposed algorithms is tested by experiments and the experimental results are presented.

Spin images have been widely used for representing local three-dimensional (3D) shapes in 3D object recognition and 3D facial landmark detection. An improved spin image descriptor is proposed which enhances shape discrimination performance significantly over the spin image. By generating several sub-spin images for angular-partitioned subspaces, the description of unique angular features within local surfaces can be offered. The experimental results show that the proposed angular-partitioned spin image enhances the localisation accuracy of facial landmarks by 47% and detection reliability by 33% as compared to the spin image.

Tests to determine the multiplicity of (1 + x) in a polynomial in 𝔽₂[x] are provided. The primary application is to detect decode failure in binary BCH codes whose generator polynomial includes multiple factors of (1 + x).

A novel microstrip bandpass filter with multiple transmission zeros is proposed, where two half-wavelength resonators loaded by short-circuited stubs are implemented into its design. A section of coupled lines and a grounded via-hole are introduced to serve as a capacitor and an inductor, respectively. Then, four controllable transmission zeros can be successfully obtained, and the locations of two outer transmission zeros are controlled by the diameter of the via-hole. A second-order filter sample with better frequency selectivity and wide stopband was fabricated using standard printed circuit board (PCB) technology, and its measured S-parameters agree well with the simulated ones.

Optical rectification of ultrafast laser pulses is widely used to generate THz radiation. Here, the microwave frequency comb generated by optical rectification with a ZnTe(100) crystal and a mode-locked ultrafast laser has been measured, showing that the harmonics are at integer multiples of the pulse repetition rate of the laser (500 Hz). Strong correlations of the peak powers of the simultaneously measured THz spectrum and the measurements of the microwave frequency comb near 7.5 GHz suggest that they have a common origin.

A novel liquid crystal (LC) based hollow waveguide phase shifter with an LC section of 14.6 mm is presented , operating at 80–110 GHz. As a proof-of-concept, the phase shifter is biased by using permanent magnets, which results in a differential phase shift of 307°–318° and an insertion loss of 2.1–2.7 dB in the desired frequency range of 99–105 GHz. Hence, a phase shifter figure of merit of 118°–148°/dB is determined, which are to the authors’ knowledge the highest values in this frequency range for passive phase shifters.

The effect of temperature on thermoelectric microwave power sensors is researched in order to extend its application field. The fabrication of this microwave power sensor is divided into a front side and a back side processing using GaAs MMIC process and MEMS technology. The measurement results show that the temperature has a significant effect on the performance of thermoelectric microwave power sensors. The obtained temperature coefficient is about 0.488 mV/(W · K), which has an important reference value for the thermoelectric microwave power sensors. The reason is that the accuracy of microwave power measurement will be realised as long as the environment temperature is tracked.

A compact substrate integrated waveguide (SIW) filter with an improved stopband using multilayer embedded mixed coupling (MC) is presented. By implementing MC into the input/output SIW, the filter not only exhibits good rejection for the upper stopband, owing to an additional controllable transmission zero, but also has a miniature size of 18 × 12 mm² by profiting from its low-temperature co-fired ceramic structure. An experimental second-order filter with three TZs has been designed and fabricated. The measured results show good agreement with the simulated ones.

The bilateral transformer coupling technique is proposed to improve the phase noise of the transformer-based voltage controlled oscillator (VCO). Current-reuse and self-injection locking techniques are also included and demonstrated in CMOS 0.18 µm technology. The oscillation frequency ranges from 5.02 to 5.41 GHz. The output power is − 1.2 dBm, the phase noise at 1 MHz offset frequency is − 128 dBc/Hz and the chip size is 0.478 mm². The power consumption is 3.6 mW. The figure-of-merit of this oscillator is − 197.

All-optical three-input logic minterms are generated at 42 Gbit/s with a Sagnac interferometer by using cross-phase modulation in a semiconductor optical amplifier. To the best of the author's knowledge, this is the first time that high-speed logic operations with more than two inputs have been experimentally demonstrated in a Sagnac interferometer. Correct and clear temporal waveforms are successfully observed. Bit error ratios and optical signal-to-noise ratios are measured to demonstrate the effectiveness of the method. As the basic units of combinational logic operations, logic minterms are promising candidates to construct reconfigurable and programmable logic functions.

A long-term miniaturised stabilisation scheme for a mode-locked laser based on a rubidium coherent population trapping atomic resonator is demonstrated. By directly locking the repetition rate of a mode-locked laser to the ⁸⁵Rb 3.035 GHz coherent population trapping resonance, a miniaturised stabilisation system for the mode-locked laser is achieved. The stabilised laser shows a frequency instability of 5 × 10⁻¹¹ (1 s) and a long-term instability of ∼3 × 10⁻¹². This scheme avoids the extra stability loss in the electronic connection between the mode-locked laser and the frequency reference. The whole stabilisation system occupies only a physics package of 5 × 5 × 2.2 cm, which provides a compact and portable approach for mode-locked laser repetition rate stabilisation.

A varifocal lens (previously reported by the authors) made of a single crystal of potassium tantalite niobate (KTa_{1− x} Nb _x O₃, KTN) is characterised by its fast responses and large apertures ( ∼ 3 mm). Presented is a report on the focus shift performance of this varifocal lens with response times of < 2 μs. To investigate this quick response, a strobe technique was introduced. It was confirmed that the KTN lens changed its lens power in 2 μs as predicted by the theory stating that the lens power is proportional to the square of the applied voltage. The lens power can be controlled from 0 to 0.8 m⁻¹ at a wavelength of 1.06 μm.

A charge recycling dual-rail voltage supply is proposed for battery-powered radio frequency identification tags. By utilising a capacitor voltage divider and recycling charge from the upper to the lower rail with a virtual ground balancing circuit, an implicit on-chip DC–DC converter can be achieved. The proposed dual voltage scheme provides an effective way of reducing power consumption both in sleep and active modes of operation.

A novel high-efficiency rectifier using a composite right-/left-handed (CRLH) transmission line (TL) is proposed for 900 MHz wireless power transmission applications. The open-ended CRLH TL stub replaces the bandpass filter (BPF) of a conventional rectifier and has a small size as compared to the traditional BPF. The open-ended CRLH TL stub is designed to suppress the second and third harmonics and to match the fundamental frequency to 50 Ω impedance. The maximum RF-to-DC conversion efficiency of the proposed rectifier is 69.9% at an input power of 50 mW and a load of 1.8 kΩ. A design procedure based on the phase response of a CRLH TL is presented and validated by simulated and measurement results.

Within future homes and electrical power networks, emphasis is being placed on intelligent, distributed measurement devices. In particular, the recognition of individual or aggregated loads through harmonic signature has been proposed as a useful way to enhance the value of home energy monitoring/control. Clearly, the cost of implementing such measurement devices is a major barrier to acceptance. In a recent project, a challenge was set to implement real-time software on an ARM ^® Cortex™ LPC1768 microcontroller platform (chip cost c. £4). The software must be capable of measuring a single-phase AC frequency, real and reactive power flows and provide a full breakdown of the voltage and current (and power) behaviour via harmonic analysis from DC to the 40th, in real-time with a new output every 20 ms. In addition, the algorithm must be capable of adapting the measurement when the frequency is not nominal (50 Hz) so that spectral leakage is minimised. It is found that the LPC1768 processor is capable of supporting such an algorithm when it is coded appropriately. This knowledge de-risks the proposed use of such cheap microcontrollers for these relatively complex tasks.

A reliable and methodical solution to restrain transient undershoot on VS pin for a high-voltage gate drive circuit with a transient negative voltage detector circuit (TNVDC) is proposed. The proposed TNVDC circuit does not consume any quiescent current while the chip works normally and it is totally integrated in a high-voltage integrated circuit (HVIC) without any additional discrete devices in the system. The proposed circuit could send a control signal to the drive stage of the HVIC for decreasing the sink current while the transient undershoot of the VS is excessive. The measurement shows that the negative voltage surge tolerance is −98 V of the HVIC with TNVDC.

A periodic comb reflection frequency selective surface (CR-FSS) is presented for reducing interference caused by the propagation of signals via corridors. The novel CR-FSS has been designed to reduce the power of the forward scattered signal and increase the backscatter. For a specified comb period and angle of incidence, the direct forward scatter of the CR-FSS can be reduced by 5–15 dB and the backscatter increased by 10–15 dB over a frequency range of 10.8–13.5 GHz for a vertically polarised signal and 10.8–17 GHz for the horizontal polarisation. The CR-FSS is thus shown to be effective for both vertically and horizontally polarised signals. Comb period and angle of incidence are chosen to satisfy the conditions of Bragg's Law to provide a maximum backscatter at 10.8 GHz. By installing this novel surface in corridors, interference between multiple neighbouring transmitters can be reduced.

The dimensionality effect is avoided by the use of sufficient statistics in event probability estimators realised by importance sampling. If the system function is not a sufficient statistic, an approach is proposed to reduce the dimensionality effect in the estimators. Simulation results of false-alarm probability estimations, applied to radar detection, confirm a clear concordance with the theoretical results.

Radar research using transmitters of opportunity (commensal radar (CR)) has experienced a resurgence in popularity, focused mainly on target detection and less so on target classification. This reported work has demonstrated that CR can be used to estimate the rotation rate of an aircraft propeller accurately over a wide range of frontal aspect angles. The propeller induces polarisation modulation, which results in amplitude modulation of the signal received by the passive radar receiver. This effect is derived mathematically and verified with a detailed electromagnetic simulation of the aircraft's propeller. Lastly, these findings were validated with field measurements of a Cessna 172 aircraft.

The three-dimensional integrated circuit has attracted considerable attention because of the evolving functions of today's integrated circuit products and a continuing demand for reduced power consumption and miniature chip size. Through-silicon vias (TSVs) provide a vertical interconnection between stacked dies; they are much shorter and have a denser connectivity than the hybrid horizontal and bondwire interconnects in conventional use. Differential interconnects are more commonly used in high-speed digital circuits rather than single-ended ones because of their higher immunity to common-mode noise. Accordingly, presented is a scalable physical model for differential TSVs. Mixed-mode S-parameters were generated using the established model and the electrical performance of a GSSG-type differential TSV was compared with that of a GSGSG-type differential TSV. Furthermore, four-port S-parameters were measured up to 40 GHz to validate the modelled results.

Floating-gate transistors are increasingly used for digital and/or analogue non-volatile memory in standard CMOS integrated circuits. The mask design of the floating-gate's tunnelling junction, where erasure and/or writing occur, is examined. Aided by static and transient tunnelling current measurements for a variety of tunnelling junctions, recommendations for constructing these junctions to minimise the duration, power consumption and oxide degradation of programming are presented.

A high-voltage extended drain MOS (EDMOS) transistor with a dual work function gate (DWFG) is discussed. This device enhances device performance by modifying the electric field in the channel. For DWFG EDMOS device fabrication, the polycrystalline silicon gates on the source and drain sides are doped by p + and n + ion implantation, respectively. Experimental results from the fabricated DWFG EDMOS devices show improved transconductance (g _m), drain conductance (g _ds) and specific on-resistance (R _ON) characteristics without breakdown voltage reduction.

First, a counter example is constructed to show that for any given positive integer K ≥ 2 and for any (1/√K + 1) ≤ t < 1, there always exists a K-sparse x and a matrix A with the restricted isometry constant δ_{K +1} = t such that the orthogonal matching pursuit (OMP) algorithm fails in K iterations. Secondly, it is shown that even when δ _{K + 1} = (1/(√K + 1)), the OMP algorithm can also perfectly recover every K-sparse vector x from y = Ax in K iterations. This improves the best existing results which were independently given by Mo and Shen and Wang and Shim.

Using complex wavelets, the tree-structured complex wavelet Bayesian compressive sensing method is proposed. The hidden Markov tree is used for inter-scale relations of wavelet coefficients. The spike-slab distribution is considered for the prior. From simulation results, the number of measurements and the value of reconstruction error reduce by 25% and 65%, respectively.

The comb structure formed by the fundamental frequency and its harmonic partials in the spectrum is the important distinction between the pitch and the white noise or other coloured noises. A pitch estimation method based on harmonic salience is proposed which utilises the characteristic mentioned above to enhance the noise immunity and suppress the half-frequency errors and multi-frequency errors effectively. Experiments on various noised data of the TIMIT database demonstrate the robustness compared with other state-of-the art pitch estimation approaches.

The existing data-forwarding strategies in wireless sensor networks (WSNs) may not be feasible for some applications where synchronisation and physical location information are not available. A novel asynchronous data-forwarding strategy for energy-harvesting WSNs is proposed, where the sleep duration, wake-up moment and the transmission coverage of a sensor node are determined independently on a per-node basis. This strategy obviates the need for synchronisation control and the precise location information of the sensor node. The numerical results show that the data-forwarding delay can be significantly reduced by the proposed strategy. The reduction in the delay is more notable for WSNs with more sensor nodes.

Data fusion methods are proposed for cooperative modulation classification by using multiple sensors in multipath fading channels. Performances of these methods are evaluated, and compared with those of the existing optimal decision fusion method, through Monte Carlo simulations for a realistic application scenario, and evident gains are confirmed.