A new tri-band dual-polarised omnidirectional antenna is proposed. The dual-polarised antenna consists of a metal cuboid body with a vertical slot for horizontal polarisation (HP) and a rectangular back metal cavity with two folded horizontal slots for vertical polarisation (VP). A metal HP feedline is employed to coupling feed the vertical slot while a metal VP feedline is used to excite the two horizontal slots. Due to the coupling feed and the orthogonality between the vertical and horizontal slots, the dual-polarised antenna features three bands and a high isolation. Experimental results show that the tri-band dual-polarised antenna covers the Chinese Unmanned Aircraft System bands (840.5–845, 1430–1444 and 2408–2440 MHz) with reflection coefficients <−10 dB and isolation >32 dB. Good omnidirectional radiation patterns are observed for both HP and VP.

This Letter presents a novel pseudo-omnidirectional antenna that is appropriate for wide beam applications, e.g. handheld devices, along with a reduced back radiation that suits wearable applications as well. The design consists of a horizontal omnidirectional antenna placed on a proposed artificial magnetic conductor (AMC) surface that enhances the gain in the broadside direction, reduces the back radiation, and enables good radiation in the side directions. A 5 GHz folded dipole on a 2 × 2 AMC array surface is designed and characterised. Simulations and measurements, which are in a very good agreement, show that the radiation has a heart-shaped pattern, with a front to back ratio of >13 dB, a front to side ratio of <2.5 dB, and a half-power beam width of >230°.

With the increasingly multiple-input multiple-output (MIMO) applications in ultra-wideband (UWB) communication systems, antenna researchers face big challenges in designing compact operational geometries that meet the essential demand of achieving high isolation among antenna elements over the ultra-wide operating bandwidth. Disposed antenna elements orthogonally are seen to be the most common methodology to reduce mutual coupling of MIMO antenna by exploiting polarisation diversity performance. In such configuration, the mutual coupling mainly depends on the inter-element spacing, which it may not be in line with the compact structure. In this Letter, taking the advantages of symmetry of planar UWB antennas, asymmetric feeding scheme miniaturising technique is utilised to improve the inter-element isolation of a reference MIMO antenna made up of four previously designed slot antenna elements, closely-disposed orthogonally. Analytical results have validated the design concept and the improved MIMO antenna using the halved-chopped elements, showing good performance in terms of impedance matching, isolation, radiation features, signal correlation, and system fidelity factor.

Mode tracking in a proper way is still a challenging task for characteristic mode analysis. A novel mode tracking method is proposed based on correlating mode current density distribution matrix. First, the mode current density distribution matrix corresponding to eigenvectors is calculated. Secondly, the proposed tracking method is performed by correlating the mode current density distribution matrix. In order to verify the effectiveness of the proposed method, a planar Minkowski fractal structure and a complex three-dimensional structure are analysed by the proposed tracking method and the commercial software FEKO, respectively. The results show that the proposed method works effectively.

In a very interesting recent paper, the authors illustrated an improved analysis of orthogonal matching pursuit in the general perturbation model , where is the measurement perturbation. This comment will point out that there are some errors in that paper.

The performance of the effective capacity metric under Fisher–Snedecor fading channels is investigated. To this end, a novel exact closed-form expression for the effective capacity is derived. Furthermore, in order to gain more insight, a simple asymptotic expression at the high signal-to-noise ratio regime is also provided. Additionally, expressions for the effective capacity of the Nakagami-m and Rayleigh distributions are deduced from the proposed results as special cases. The analytical results are compared to Monte-Carlo simulations to prove the correctness of the analysis. The results show that fading has a more positive influence on effective capacity performance than shadowing.

This letter proposes winding switching for the high-performance of permanent-magnet vernier machines (PMVMs) in wide speed range operation. The machine is operated in two modes: cumulative and differential. Before winding switching (cumulative mode), the machine is operated like a conventional three-phase PMVM. The machine provides high torque density and high efficiency in this mode. After winding switching (differential mode), the back EMF and inductance of the machine are decreased significantly, which enable wide speed range operation and the attainment of high power factor in high-speed operation.

A compact dual-band filtering power divider (FPD) is presented based on substrate-integrated waveguide (SIW) triangular cavities (TCs). By exploiting the first two modes in SIW TCs, the FPD is synthesised and designed with centre frequencies of 5.5 and 8.3 GHz and identical absolute bandwidths of 0.8 GHz. Two-section 50-Ω transmission lines loaded with two resistors are explored to achieve good isolation at two arbitrary frequency bands of the dual-band PFD. Good agreements can be observed between the measured and simulated results and better than 20-dB isolation within the two passbands has been successfully achieved.

The development of a compact 41–93 GHz symmetric quadrature hybrid based on multi-conductor coupled lines in standard 65 nm bulk CMOS process is presented. The equivalent two-line model of the multi-conductor coupled line is derived and analysed with even/odd mode theory and ABCD matrix. With the multi-conductor coupled-line sections, high coupling coefficient, compact size, and wideband operation can be realised; meanwhile, keeping the responses of four ports fully symmetric, which is suitable for circuit applications demanding port symmetry. Designed compact symmetric quadrature hybrid is implemented with 65 nm bulk CMOS process. Measured results show the CMOS quadrature hybrid has good phase difference within 90 ± 2.5° and amplitude balance <±0.5 dB from 41 to 93 GHz, or a 75.5% fractional bandwidth, with an extremely compact size of 93 µm × 149 µm (0.0138 mm²), or 0.051λ ₀ × 0.024λ ₀.

A dual-mode bandpass filter is proposed using a single ring resonator with non-uniform linewidth. The proposed filter consists of a circular patch with a circular hole and two chip inductors loaded into the gap in the ring. The non-uniform linewidth ring resonator can be realised by moving a circular hole in the circular patch. This asymmetric structure creates a pair of degenerate modes, and thus acts as a dual-mode filter. Two inductors applied to the gap generate one transmission zero on each side of the passband, improving the skirt characteristics of the filter. In addition, a dual-mode filter with the same characteristics is implemented by replacing the chip inductor with a meander line.

Lost-shell casting as a novel fabrication technique is examined, providing the durability of solid metal components with the shape flexibility of additive manufacturing. The feasibility of lost-shell casting is established for use in microwave and RF applications. A well known, standard rectangular cavity resonator design was used to validate this novel method of fabrication. Using lost-shell casting, a cavity resonator with a quality factor of 2200 was constructed. The results shown in this work confirm the validity of lost-shell casting as a novel method of rapid fabrication for completely metalised components in RF and microwave applications.

A Fermi-level managed barrier (FMB) diode was used for the heterodyne detection of terahertz waves for the first time. A quasi-optical module integrating an FMB diode and a broadband trans-impedance amplifier exhibited an intermediate frequency bandwidth of 11 GHz. A very low noise-equivalent-power of 1.1 × 10⁻¹⁸ W/Hz was achieved at ∼300 GHz with a very low local oscillator power of 6 × 10⁻⁶ W.

The free-space optical communication of high-speed 120 Gbit/s wavelength-division multiplexing (WDM) QPSK signals is demonstrated in an outdoor atmospheric channel with a distance of about 1 km. A pair of optical terminal systems with the capture and tracking functions is used to establish the atmospheric channel. The power fluctuation through the atmospheric turbulence agrees well with the exponentiated Weibull distribution. At the BER of 3.8 × 10⁻³, the required receiving powers for the three WDM channels are similar, which are all <−15.4 dBm.

The authors propose a transmitter digital filter for joint optimisation of signal pulse shaping and chromatic dispersion pre-compensation, providing a detailed analysis of the architecture complexity. Experimental transmission of 40 × 50G channels (28 Gbaud four-level pulse amplitude modulation) over up to 110 km uncompensated standard single mode fibre with low-bandwidth hardware is demonstrated.

A current fed resonant converter is presented and developed to have the advantages of wide input voltage operation range and less ripple current. The developed circuit includes two boost inverters in the front stage and one resonant converter in the rear stage. Two boost converters are operated using interleave pulse-width modulation in order to reduce the input ripple current. The resonant converter with voltage doubler circuit topology is adopted to obtain high-voltage output and realise zero-voltage turn-on switching for all power switches over all load ranges. The active switches of two boost converters and the resonant converter share the same power switches so that the switch counts in the studied circuit are reduced. In order to extend the input voltage operation range, an additional boost converter is active when the input voltage is lower than the defined voltage level. Therefore, a wide input voltage range operation, 24–76 V, of the developed circuit can be realised to apply in the fuel cells or solar cells input applications. The feasibility and practicality of the developed circuit are confirmed by the test results with an 800 W prototype circuit.

Two-dimensional (2D) gold multiple signal classification (gold-MUSIC) is proposed in order to reduce the complexity of MUSIC and make real-time processing possible for joint range and angle estimation by multi-carrier frequency multiple-input multiple-output radar. 2D gold-MUSIC evaluates the MUSIC spectrum at coarse intervals, then determines peaks by narrowing the 2D search area iteratively based on a simultaneous gold-section of range and angle to find accurate localisation of the peaks. The proposed method eliminates huge computation burden caused by a grid-by-grid spectral search of classical MUSIC and obtains remarkable resolution in range and angle with no dependence on array configurations. Numerical studies demonstrate the effectiveness and efficiency of the proposed method.

A new wideband cavity-backed aperture coupled microstrip antenna is presented for 79 GHz short-range multi-input multi-output radar applications. This design is based on a sub-array consisting of two single elements, and each element is founded on a cavity backed aperture coupled patch antenna. A microstrip to strip-line transition and a series feeding topology is used to feed the elements. The antennas are manufactured by using a new high-resolution multi-layer PCB technology. This technology is able to deliver high-resolution stacked micro-vias on very thin substrates. The performance of the designed antenna has been verified by both simulations and measurements. The bandwidth is 11.2%, and the maximum gain and efficiency are 6.05 dBi and 80% along 77–81 GHz.

A phase improvement algorithm has been developed to design the non-linear frequency modulated (NLFM) signal for the four windows of Raised-Cosine, Taylor, Chebyshev, and Kaiser. The authors have already designed NLFM signal by stationary phase method (SPM). The simulation results for the peak sidelobe level of the autocorrelation function in the phase improvement algorithm reveal a significant average decrement of about 5 dB with respect to the stationary phase method. Moreover, to evaluate the efficiency of the phase improvement algorithm, the minimum error value for each iteration is calculated.

One of the prerequisites of electronic warfare (EW) is to have the means to provide secure point-to-point wireless data and voice communications with other ground stations. New technologies are giving rise to bigger information security threats. This situation illustrates the best the urgency of reducing the development time of EW systems. Previous works suggest that digital systems are the best candidates for this purpose and therefore form the backbone of modern EW. As a result, digital modulation techniques are widely used in modern wireless communication systems. This is largely due to their high resistance to noise and their high transmission capacity that can be achieved through data multiplexing. In this Letter, a new reconfigurable architecture of a phase shift keying (PSK) modulator is described and implemented on FPGA. The latter can be configured in real time to produce the following modulation schemes: QPSK, 8-PSK, and 16-PSK without having to regenerate the FPGA configuration bits. This action can be done by software via programming or manually using a DIP switch. The proposed design is implemented on the Xilinx xc7k325tfbg900 FPGA using the Genesis 2 development board. The experimental results are in agreement with the simulations.