A compact double-dipole driver is constructed for designing quasi-Yagi antenna with enhanced bandwidth and stable high gain. It is composed of a magnetic dipole and a folded electric dipole, realised by cylinder dielectric resonator and split-ring resonator. The two dipoles operate at two close frequencies, leading to bandwidth enhancement. Meanwhile, the gains of the two dipoles are also close so that the stable gain in the operating band is obtained, which can be entirely enhanced by the zero-index metamaterial in front of the dual-dipole driver. For demonstration, an antenna prototype centred at about 9.6 GHz is implemented and measured. The simulated and measured results are given, showing good agreement.

The problem of optimised design of diversely polarised sparse array for joint synthesis of spatial and polarisation beampattern is addressed in this Letter. Two kinds of polarised array configurations, cocentred and non-cocentred crossed-dipole arrays, are considered. Minimum interelement spacing constraint along with non-cocentred constraint are involved in the design methods by using two discrete linear operators. The optimisation process can be formulated as a mixed-integer quadratically constrained programming problem which guarantees the optimal solution of the sparse array configuration. Comparison examples with state-of-the-art method validate the advantages of the proposed method in terms of the reduction of required element number and the enlargement of adjacent element spacing.

Due to interest in lenses at telecommunicatons in the lower frequency range of 30–600 GHz (5G/6G applications) sub-terahertz range lenses have started to make their appearance. Geometrical optics is typically used due to its faster calculation speed, which is faster than finite element methods (FEMs). A 30-mm plano-convex lens was simulated with a COMSOL ray tracing module and CST was used to simulate 30, 60, 300 and 600 GHz FEM simulations. Focal points were 248, 189, 180, 118 and 131 mm with CST and 253 mm with COMSOL.

A low-power 3-stage continuous time linear equalisation (CTLE) was designed in 28 nm CMOS technology for a high speed SerDes in a 5G backhaul. The CTLE active inductor is a transconductance-based, for high-frequency operation and for area reduction. The active inductor can be tuned around 10 GHz while consuming 11.17 mW from 0.9 V power supply. The CTLE compensates about 19.5 dB of attenuation due to the channel at a data rate of 20 Gb/s per link, with a power efficiency of 18.6 fJ/bit/dB, which is better power efficiency than the previous works reported in the literature.

A signal-dependent dithering calibration exploiting noise quantiser (NQ) technique to correct capacitor mismatch and inter-stage gain error in pipelined successive approximation register (SAR) ADCs is proposed. With signal-dependent dithering injection, capacitor mismatch and gain error are extracted and subsequently calibrated as one error in the background. Besides, a novel NQ is proposed for a dithering injection only when the residue is near the threshold of the comparator, thereby allowing the injection of dithering without consuming the dynamic range. The simulation results show that the calibration can significantly improve the performance of pipelined SAR ADCs without extra hardware overhead and timing budget.

A novel broadband balun based on centrosymmetric spiral transformers is proposed. Two parallel circular spiral transformers comprise the proposed balun, which is different from the Marchand structure. The equivalent coupled line model demonstrates that asymmetric structure is helpful to realise the appropriate balun with good amplitude balance and low return loss. Finally, combined with the structural characteristics of the spiral transformer in monolithic microwave integrated circuit designs, a centrosymmetric structure with compact size is adopted. The balun is designed and fabricated in WIN's IP2M process and its core size occupies an area of . The simulation and measurement agree well, exhibiting a bandwidth covering from 2 to 18 GHz with good return loss, flat insertion loss and high stability of 180° phase difference.

Current pulse shaping technique is proposed for low spur fractional-N phase-locked loop, which is realised by a variable amplitude charge pump (VA-CP) and a fixed-position, fixed-width and variable-period pulse generator (FFVPG). The current pulse of VA-CP driven by the FFVPG is shaped to fixed position, fixed width, variable amplitude and variable period for eradicating both reference spurs and fractional spurs. The period of VA-CP's current pulse is T _REF during transient and N ₁ × T _REF during locking status, in which the N ₁ should be properly set in order to reduce fractional spurs as far as possible and accelerate locking time. The spur performance of the proposed fractional phase-locked loop is evaluated by analysing the spectrum of tuning voltage when reference frequency is 20 MHz and division ratio is 120.13. Spectre based simulation results show the reference spurs at integer multiplies of 20 MHz is eradicated, and the fractional spurs at 10 MHz and the other fractional frequencies are 19.67 dB and much less than that with the existing technique, which verify the feasibility of this study.

The authors propose a column counter that uses a logical-shift algorithm in column-parallel single-slope ADCs for low-power CMOS image sensors. The proposed column counter lowers power consumption by reducing the amount of internal toggling nodes and parasitic capacitance. Simulation results showed a 32% reduction in power consumption and a 60% reduction in the power-delay product compared to a conventional up/down counter.

A miniaturised dual-mode filter based on dielectric resonator (DR) with a controllable passband is proposed in this Letter. The filter is a combination of a traditional rectangular DR and a planar metallic loop with the dual-mode feature. The loop decreases the frequencies of the dominant modes inside the DR, thus the circuit size is greatly reduced compared with the traditional DR devices. By using commonly used tuning disk, the passband of the proposed filter can be altered freely. A demonstration example is designed and fabricated, and the simulated and measured results verify the design method with good agreement.

A referenceless single-loop clock and data recovery (CDR) circuit with a half-rate linear phase detector (PD) and an inherent frequency acquisition technique are introduced. Cycle-slip in the half-rate linear PD and its relationship with the frequency acquisition are described in detail. The single-loop CDR consists of a conventional phase-tracking loop and a frequency-tracking unit, referred to as the cycle-slip detector. The proposed CDR is fabricated in a 28 nm CMOS process and achieves a wide capture range of 2.6 Gb/s for a PRBS31 pattern. The RMS and peak-to-peak jitter of the recovered clock are and , respectively, at 8 Gb/s. The high frequency jitter tolerance is measured as . The CDR occupies and consumes 26 mW at 8 Gb/s from a 1.0 V supply.

The acknowledgment (ACK) compression makes the available bandwidth estimation in bottleneck bandwidth and round-trip propagation time (BBR) inaccurate which results in the high queuing delay under low packet loss rate environments. The additional queuing delay affects the user experience of interactive applications like Skype. To solve the above-mentioned issue, this Letter presents a novel method, named calibrating bandwidth estimation (CBE), to calibrate the bandwidth estimation. The CBE can detect the implausible ACK rates accurately and the extensive simulation prove the effectiveness of CBE.

This Letter presents a bias compensated M-estimate affine-projection-like algorithm for robust adaptive filtering in case of noisy input signal and impulsive noise interference. In order to mitigate the effect of bias introduced due to noisy input signal, a bias compensation vector is derived along with robust cost function minimisation employing M-estimate and accordingly the weight update learning process of the adaptive filter has been improved. In conjunction with this, a new input noise variance estimation method is introduced using the median filter. The proposed algorithm is evaluated for acoustic echo cancellation application and compared with other existing methods. Simulation results demonstrate its effectiveness in terms of enhanced convergence and better steady-state performance in case of impulsive environment and input signal contaminated with noise.

A technique to estimate an incoming radio frequency (RF) signal angle of arrival (AOA) irrespective of the RF signal amplitude is presented. It is based on measuring the DC voltage at the output of two modules where each of them consists of an optical modulator, an optical filter and a photodetector. An RF signal amplitude-independent AOA can be obtained from the ratio of the two DC voltages. Experimental results are presented that demonstrate 0°–63° AOA measurement with <3° errors for an RF signal with three different power levels of 3.2, −0.3 and −3.6 dBm into the modulator.

For classical Philips audio retrieval, the short duration and the long silent period in inserted template audio make a major challenge to the robustness in actual environments. In this study, a novel audio retrieval method is proposed to handle the challenge by modifying both the fingerprinting stage and the matching stage. While extracting audio fingerprints, the silent segments are firstly detected. Then, a specific fingerprint is arranged to the silent segments for distinguishment. In the matching stage, a window-by-window search is performed to figure out the inserted audio templates. Moreover, the searching window is divided into several segments for precise comparison between the template audio and the test audio. A testing dataset is made by randomly arranging the duration of the inserted template audio to be from 3 to 5 s. Experiment results show that mean average precision and recall are significantly improved by the proposed method.

Distance vector-hop (DV-hop) is a classical node localisation method for wireless sensor networks. Its main advantages are ease of use and excellent scalability, but its shortcomings are also very prominent for the high requirements on the network topology and low localisation accuracy in practical applications. An amended DV-hop strategy is provided to improve the shortcomings of the classical DV-hop including two aspects: one is that an N-gram model is adopted to amend the distances between unknown nodes and beacons and the other is that a weighed Levenberg–Marquardt method is adopted to optimise the unknown nodes’ initial positions. Simulation results show that compared with the original DV-hop method and the other two typical improved methods, our proposed strategy improves the adaptability of the DV-hop class methods to network topology changes, and the localisation accuracy is significantly enhanced.

Polynomial cancellation coded discrete Fourier transform-spread orthogonal frequency division multiplexing (PCC-DFT-s-OFDM) is famous for the flexibility of DFT-s-OFDM on the trade-off between peak-to-average power ratio performance and spectral efficiency. Deploying it on numerous user equipments (UEs) as enhanced uplink signalling becomes a practical issue. In this Letter, a bit-level implementation of PCC mapping is proposed, so that the compatibility of implementation of corresponding circuits on UE transmitters would make the deployment more easily. By taking Long Term Evolution and New Radio standards as examples, the equivalency of bit/symbol-level implementations is validated in terms of bit error rate performance.

Existing high-precision inter-satellite radio frequency (RF) measurement systems were mostly based on two-satellite formations, and there lacks further research on measurement schemes for multi-satellite formations. The frequency division multiple access (FDMA) and the code division multiple access based schemes are widely used, but not applicable for distributed applications due to their poor scalability. The time division multiple access (TDMA) based scheme can overcome this weakness, and has been applied in the global positioning system (GPS) IIR/IIF inter-satellite link. However, the atomic clock used in GPS is not suitable for microsatellites. If a miniaturised frequency source instead of the atomic clock is utilised, the two way ranging (TWR) method adopted in this system would encounter a sharp decrease of measurement accuracy. To this end, this Letter aims to propose a novel TDMA based distributed RF measurement scheme for multi-microsatellite formations. A TDMA based distributed broadcast protocol is employed in the media access control layer, closely integrated with the asymmetric double-sided two-way ranging method adopted in the physical layer. Numerical and simulation results demonstrate the superiority of the proposed scheme over the conventional TDMA scheme. The proposed scheme can be recommended for future multi-microsatellite formation missions.

Modulation recognition (MR) is an important technology in modern communication systems. Traditional MR methods can be categorised as the maximum likelihood hypothesis, pattern recognition, and deep learning-based methods. The authors can achieve high-recognition accuracy when the signal-to-noise ratio (SNR) is high. However, their recognition accuracy is greatly reduced when the SNR is low, especially when the SNR is below 0 dB. In order to improve the MR accuracy at low SNRs, they propose a pre-denoising algorithm, which is used before MR methods. The model of the pre-denoising algorithm is a fully convolutional neural network, which is similar to an auto-encoder. They also use residual learning to speed up the training process. Experimental results show that the proposed pre-denoising algorithm can significantly enhance the SNRs of modulated signals and improve the accuracy of MR methods.

Antenna arrays are widely used in radar systems and mobile networks in the physical layer to mitigate interference as well as to enhance the reliability and the capacity of the system. The performance of beamforming algorithms depends on the channel realisation and its associated micro-parameters (angle of arrivals, multi-path components, fading) plus the array geometry. The multiplicity of these micro-parameters makes it difficult to establish a tractable characterisation of the overall performance. In this Letter, a new parameter, an algebraic angle cosine between the signal subspace and the interference subspace, is introduced to characterise the interference impact. It allows the derivation of a lower bound on the signal-to-interference-plus noise ratio of the Capon beamformer. Outside two regions where the interferers are quasi-orthogonal or quasi-aligned with the desired user, the lower bound decreases linearly with this parameter.

In this Letter, the authors analyse the diversity order of the precoding-aided spatial modulation (PSM) system with receive antenna subset (RAS) selection. It is shown that when there are transmit antennas, receive antennas, and selected receive antennas, the achievable diversity order is given by , where the product gain of is achieved by the zero-forcing precoding scheme and another of can be attained by the optimal RAS selection algorithm.