The scientific capability of an astronomical phased array feed receiver can be quantified by combining the bandwidth, sensitivity, and field of view into the overall survey speed of the instrument. The authors investigate the relationships between survey speed and reflector geometry, array layout, element spacing and element configuration using numerical simulations, to determine the values of these parameters that lead to optimal system performance. They characterise the array element spacing that leads to maximum survey speed as a function of the reflector f/D. To further improve survey speed in relation to the overall number of array elements, the authors explore the possibility of using elements with modest levels of superdirectivity to sample more of the focal plane Airy pattern and increase optimal spacing for survey speed figure of merit. The results explain how optimal survey speed is controlled primarily by the influence of element type and array layout on the peak achievable aperture efficiency.

This Letter proposed a polarisation detection sensor by utilising electro-optic (EO) crystals in purpose of tumour's boundary detection. In this work, efficiency of uniaxial (anisotropic) EO crystals like CdTe and isotropic EO crystals such as polymer-dispersed liquid crystal (PDLC) as the polarisation detection sensor is studied and compared with each other. Based on, derived equations for refractive index change as a function of electric field (Pockels effect) for these two types of EO crystals, capability of using PDLCs in polarisation detection sensors is confirmed. In addition, simulations are prepared to support this claim. To this end, PDLC probe is used to detect boundaries of a simulated tumour (target with the ability to change polarisation of backscattered signal).

This Letter proposes a circularly polarised horn antenna with large side length ratio. In virtue of 45° deflection structure and rectangular aperture with large aspect ratio, the proposed antenna achieves wideband circular polarisation radiation in small dimension. The fabrication is made on the prototype of the proposed antenna operating in the range of 220–320 GHz. Both of the measured circular polarisation bandwidth and impedance bandwidth of the designed antenna are 37% (220–320 GHz). This compact wideband circularly polarised antenna can be widely used in terahertz applications.

In this Letter, a simplified design approach for zero-bias power detectors suited for integration in six-port receiver architectures is presented. The proposed concept uses the quadrature hybrid coupler as an effective way to improve the input impedance matching and linearity performance. The proposed solution has been experimentally validated through its implementation into a 60 GHz six-port receiver prototype to investigate its performance in detecting various M-ary quadrature amplitude modulation (M-QAM) signals. The obtained measurement results show a high accurate and linear detection responses for all investigated M-ary QAM modulation techniques (4-QAM, 16-QAM, 32-QAM). The variation in the error rates of the demodulated signals at the adjacent differential outputs is minimal (<1%), and the maximum error rate achieved does not exceed 5%. The obtained precision and linearity performances make the proposed structure highly suitable for the emerging millimetre-wave six-port receiver front-ends.

A background bit-weight calibration in pipelined successive approximation register ADC is proposed. By exploiting the conversion results of the first stage to determine the injection of the dithered signal and introducing two extra capacitors into the first stage to reduce the range of first-stage residue, a robust and totally background calibration is implemented. According to the simulation, the signal-to-noise and distortion ratio and spurious free dynamic range are improved from 66.3 to 73.3 dB and 78.4 to 85.1 dB, respectively, after calibration.

A compact Ku-band bandpass filter is proposed by using low-temperature cofired ceramic (LTCC) technology in this Letter. For miniaturisation, the folded dual-composite right- and left-handed (D-CRLH) resonator is introduced. By folding the inter-digital capacitor and microstrip section inductor in multiple metal layers, the circuit size of D-CRLH resonator can be reduced to one third of the planner one. Furthermore, the additional transmission loss caused by reverse currents is also investigated. To this end, a very compact LTCC filter is designed, fabricated, and measured, with the core circuit size smaller than 0.91 × 0.95 × 0.29 mm³. The minimum insertion loss is 1.95 dB at 13 GHz while with wide stopband suppression from 14.3 to 33.1 GHz.

This Letter presents a dual-band filtering power divider (FPD) by employing square-loop resonator loaded by open stubs. The even- and odd-mode equivalent circuits of the proposed resonator are analysed and design equations are derived. For demonstration, the power divider (PD) is fabricated and measured. The simulated results of the PD not only show a good selectivity but also it does good isolation. Finally, the comparisons of the measured and simulated results of the dual-band FPD are presented, which are in good agreement. The measured results show that the dual-band FPD has better than −30/−36 dB isolation, −16.5/−18 dB return loss, and −3.9/−4.0 dB insertion loss at centre frequencies of 3.1 and 5.3 GHz, respectively.

In this Letter, the author proposes a new feed-forward controller for single-stage flyback power factor correction (PFC) converters. By compensating the phase-lead effect caused by input capacitor current, the proposed feed-forward control duty improves the displacement factor as well as the distortion factor, and so the flyback PFC converter has high power quality. By means of the synchronous rectification circuit, the flyback PFC converter can operate in reverse when the negative current is required. To confirm the theoretical analysis and validity of the proposed control scheme, the author demonstrated the proposed control algorithm with 80 W flyback PFC converter prototype.

A novel region-scalable fitting (RSF) active contour model with symmetric cross entropy (SCE)-based global constraint is proposed to segment various kinds of images. The energy functional is mainly composed of two parts, namely the local and global constraints. The local constraint is the weighted region-scalable fitting term, which computes the local intensity information. The global constraint is constructed by measuring the difference between the intensity distribution of the object image and the intensity distribution of the original image using SCE. Moreover, some regularised terms are incorporated into the energy functional. Experimental results for synthetic and real images show that the proposed model achieves better segmentation performance and is insensitive to initial contour and noise.

Optical coherence tomography cannot easily be used for visual identification of the ganglion cell layer (GCL) for diagnosing retinal diseases owing to the extremely low image contrast between adjacent layers. To solve this problem, the authors used a limit-clipping optimisation method along with the image entropy to enhance the image contrast of targeted layers. As a result, the GCL was successfully extracted using an intelligent tracking system without impacting the segmentation of other retinal layers and image morphology. The segmentation results were evaluated through comparisons with manual segmentation results provided by clinical experts. The results of this study should help realise simple and efficient discrimination of important retinal layers for the early diagnosis of glaucoma.

Intrusion detection is a prevailing area of research for several years, and numerous intrusion detection systems have been proposed for industrial control systems (ICS). In recent ages, the attacks like seismic net, duqu and flame against ICS infrastructures have instigated great harm to nuclear infrastructures and precarious facilities in several nations. The authors outline an approach to detect intrusions/anomalies in ICS. A method is presented to detect intrusions in real-time and automatically. The existing techniques are normally designed for open systems and protocols, that lacks adequate generalisation and resistance to acclimate to other networks, and they have either short detection rate or tall rate of false positive. This Letter presents a network packet contents behaviour and bidirectional Gated Recurrent Units-based method to detect intrusions in a timely and efficient manner. The method has proven a robust method of classifying intrusions/anomalies in a proficient way. Through extensive evaluation on an actual huge scale dataset spawned from SCADA-based gas pipeline network, the proposed method shows significant performance enhancement and outclasses the standard state-of-the-art methods with 98.68% rate of accuracy. Moreover, it is also able to detect zero-day (unseen) attacks.

Radio-frequency (RF) watermarking is a new technology for physical layer authentication, whose carrier is not the traditional multimedia signals but the digital signals. In the available literature, the watermark detectors are based on the cooperative environment, where the parameters of the watermark signal are known to the receiver. In this Letter, a blind watermark detection scheme with Kolmogorov–Smirnov (K-S) test is presented. The simulation results show that the proposed scheme is effective.

In this Letter, the authors introduce a new class of concatenated codes, throughput enhancing concatenated code 2 (TECC-2), by extending the TECCs schemes to include a second uncoded implicit stream. It is shown here that TECC-2 schemes can significantly increase the throughput enhancing capability of TECCs with only a slight increase in complexity. The tradeoff between the low signal to noise ratio performance and throughput expansion of TECC schemes is also studied.

A novel folded ridge substrate integrated waveguide (FRSIW) is proposed, and the design of a higher-order-mode bandpass filter in FRSIW technology is presented. The FRSIW is proposed by folding a typical RSIW. It has a size nearly half of the conventional RSIW while keeping a relatively wide single-mode bandwidth. A higher-order-mode bandpass filter is designed and tested based on the TE₂₀₁ mode in the FRSIW. The measured frequency responses show that the proposed FRSIW filter has good selectivity, low loss and compact size.

A novel high-selective triple-mode substrate integrated waveguide (SIW) bandpass filter using higher-order resonant modes is proposed in this Letter. The new triple-mode SIW resonator is realised by the second degenerate dual modes TM₂₁₀ and one perturbed higher-order mode TM₀₂₀ in a circular SIW cavity. The resonance of TM₀₂₀ mode can be independently moved to that of dual modes TM₂₁₀ by changing the size of a floating circular patch. The proposed triple-mode SIW filter can produce three finite-transmission zeros (FTZs), which can also be controlled well by the angle between two feeding lines. For the demonstration, a triple-mode SIW filter with the centre frequency of 13.5 GHz was designed, fabricated and measured. The proposed triple-mode circular SIW filter has the merits of the high-quality factor, high selectivity and controllable bandwidth as well as FTZs.

A novel multilayer diplexer with low insertion loss and high selectivity for long-term evolution (LTE) application is proposed through the combination of two quasi-lumped element filters. Based on the equivalent circuit of the diplexer, the locations of the transmission zeros can be adjusted separately by changing the component value of each channel, thus high isolation level and wide stopband can be achieved simultaneously. Furthermore, the diplexer has an extremely compact size of 1.6 mm × 0.8 mm × 0.5 mm by using low temperature co-fired ceramic (LTCC) multilayer technology.

This Letter addresses the coherent integration problem for the moving target detection in a pulse repetition interval (PRI)-staggered radar system. Due to the random sampling, the complex coupling effects between range and azimuth will severely degrade the target parameter estimation and coherent integration performance. To deal with this issue, a fast coherent integration detection method with random azimuth sampling is proposed, where range migration is firstly compensated by applying the range-frequency reversal transform. Then, the random phase fluctuation caused by the staggered PRI can be efficiently removed by applying the non-uniform FFT technique. Finally, a moving target can be well focused. Simulated results are provided to validate the effectiveness of the proposed algorithm.

This Letter focuses on the problem of analytically evaluating the performance metric using the Cramer–Rao lower bound (CRLB) for three-dimensional (3D) time-of-arrival (TOA) target localisation. The necessary and sufficient condition on the invertibility (non-singularity) of the Fisher information matrix (FIM) is presented, and then the existence of the CRLB is analysed. Two types of equivalent closed-form formulas of the CRLB are proposed, and any one of which can be adopted to analytically evaluate the best achievable accuracy of 3D TOA localisation. Moreover, three types of the worst sensor-target geometries described by the unit vectors of line-of-sight of TOA sensors are extensively illustrated, which will lead to a worse localisation accuracy or even result in singularities of the FIM and should be avoided in the deployment of 3D TOA sensors.

Most adaptive filtering schemes employ the tapped-delay line. In part, such a fact can be explained by the assumption that the plant they intend to estimate is linear. Although such a hypothesis can be reasonable if the input signal is constrained to a certain range, sometimes it may not be valid. In this last case, the performance and stability guarantees provided by stochastic models that presume linearity of the ideal system are no longer valid. This Letter advances an analytic model of the least-mean-square (LMS) learning capabilities when the ideal system is not linear, with the additive noise including non-linear functions of the input samples. The proposed analysis does not assume neither that the excitation signal is statistically independent of the adaptive weights, nor that the additive noise is white and/or independent of input data. Furthermore, it can be applied to non-Gaussian and/or non-white input signals. Simulations show that the advanced model is more accurate than traditional approaches.

Increasingly popular online social networks contribute to the massive growth in mobile traffic. The authors find that social network data, which is easier to obtain than carrier data, can be used to optimise the deployment of small base station (SBS). In this Letter, the authors propose a framework based on analysing social network data to identify and cluster mobile traffic hot-spots by using the density-based spatial clustering of applications with noise algorithm. By comparing the clustered hot-spots with the existing macro base stations' locations, they identify where additional SBSs need to be deployed and show that such deployment can effectively improve the quality of service. The proposed simulation results show that the SBSs deployment around hot-spot has relatively better user received signal power on mobile communication network than random SBS deployment following the normal distribution or the Poisson distribution.

Several approximate matrix inversion methods have been used in linear massive MIMO uplink detectors where their convergence rate, performance, and complexity are greatly affected by the initial solution. In this Letter, the authors exploit a stair matrix, instead of a diagonal matrix, in initialising iterative linear minimum mean square error massive MIMO detector based on several approximate matrix inversion methods, namely, the Gauss–Seidel, successive over relaxation, Richardson iteration, and Newton iteration methods. Numerical results show a significant performance enhancement without a burden of extra complexity using a stair matrix over a diagonal matrix in all methods.

This Letter investigates the impacts of hardware impairments (HIs) and channel estimation errors (CEEs) on the performance of non-orthogonal multiple access (NOMA)-based satellite communication networks. Especially, the authors obtain the closed-form expression of the outage probability (OP) of the considered NOMA-based satellite communication networks. Furthermore, in order to analyse the effects of HIs and CEEs in high signal-to-noise ratios (SNRs) regime, they derive the asymptotic expression of OP at high SNRs, which provide efficient and fast ways to evaluate the impact of system parameters on the system performance. In addition, Monte Carlo simulations are provided to verify the correctness of the analytical results.