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Abstract The oversized TE11 mode bend is able to make the transmission direction of electromagnetic wave to turn 90°, and it is one of the key components in the high‐power microwave system. The mode coupling characteristics between the TE11 and parasitic modes under two different polarisations in the bending waveguide are analysed, and it is found that the TE11 suffers less interferences from parasitic modes when its polarisation direction is perpendicular to the bending plane, and the corresponding 90° TE11 bend is easier to realise high performance. To verify this analysis, an oversized 90° TE11 bend waveguide working at 10 GHz is designed, and its structural length is only 7.5 times the central working wavelength. Simulated results indicate that its relative bandwidth is 15.6% when the transmission efficiency is over 98%, and its maximum power handling capacity reaches 5.6 GW at short microwave pulse duration (less than 100 ns). The S‐parameters indicate that its S21 is about −0.1 dB from 9.5 to 10.5 GHz, and its S11 is under −25 dB in the same frequency range. Meanwhile, the high power test indicates that the bend works stably when the injected power is 3 GW.

Abstract A two‐layered wideband single‐fed circularly polarised (CP) antenna is presented by the authors. A single‐fed corner‐truncated square patch with four identical rectangular matching branches acts as a bottom‐driven patch to generate CP radiation. To broaden the 3‐dB axial ratio (AR) bandwidth, a similar patch with a larger size is loaded atop the driven patch as a parasitic patch. The measured results show that the proposed CP antenna has a 17.9% impedance bandwidth from 2.13 to 2.55 GHz and an 11% 3‐dB AR bandwidth from 2.15 to 2.4 GHz, respectively. The measured total gain is 7.1 dBic. The results indicate that the proposed antenna is a good candidate for Wireless Local Area Network band applications.

Abstract The authors investigate the feasibility of forming a composite Gaussian waveform in the high‐frequency region for jetfighter class targets with a high potential to combat the noise effect and the late‐time signature onset ambiguity when estimating the target resonance signature. The excitation waveform comprises a composite of modulated carriers with fractional bandwidth and amplitude adapted to lower specular content while enhancing the radar target resonance content in the radar return, subsequently increasing the likelihood of extracting the resonance parameters more accurately. The validation of improvement in the resonance signature requires finding the error between the excitation frequencies and the extractable resonant frequencies in the return echo and, second, the similarity or resemblance between the original echo waveform and the reconstructed waveform by the estimated resonance set. The results presented the robustness rate in instantaneous, average, and overall fashion. In conclusion, a fractional bandwidth between 0.3 and 0.4 would significantly improve the signature overall robustness with a circular then slant scattering polarisation set outperforming the horizontal and vertical directions. Also, excluding the signal's high and low energy portions further enhance the accuracy of the estimated resonance mode set.

Abstract Polarisation diversity radar enhances the performance of target detection. Time reversal exploits the multipath effect by adaptively matching propagation channels to improve the signal‐to‐noise ratio (SNR) and realise high detectability. This work combines polarisation diversity and time‐reversal technology to propose a time‐reversal detector suitable for a polarisation array radar. The maximum likelihood estimate is carried out for the time‐varying channel response to solve the channel mismatch problem, which may cause the degradation of time‐reversal performance. In addition, a conventional polarisation detector is developed under the same varying channel scenario to benchmark the time‐reversal detector, and furthermore, the SNR gain of the time‐reversal detector over the conventional detector is derived. Numerical simulations demonstrate the superiority of the time‐reversal detector. Both the polarisation detectors proposed can take advantage of the channel variations to improve the detectability, and the greater the energy brought by the channel changes, the better the detection performance achieved.

Abstract Circularly polarised multiple‐input‐output antennas embedded in wearable wireless devices attract importance in the individual security and beauty fabric modelling industry involving technology embedded on‐clothes wearables. A circularly polarised wideband is designed and analysed in the present design‐study where a wearable application uses a multiple‐input‐output. It adds 2 symmetric ‘Multi‐Input‐Multi‐Output’ antennas that are good looking design like a swan‐shaped, and the ground plane is similar to the shape of a swan. The designed novel antenna comprises a ground plane having a line feed and a rectangular inverted L‐type micro‐strip which is supporting circular polarisation. The antenna element is spanning at 3‐DeciBell (dB) Axial Ratio Band‐Width of 5.2–7.1 GHz and an impedance bandwidth (S11 less than or equal to −10 dB) of 3.6–13 GHz. The proposed antenna manifesting a channel capacity loss less than 0.2 b/s/Hz, and envelope correlation coefficient less than the value 0.02, total active reflective coefficient less than −10 dB, and diversity gain greater than the value of 9.96, Mean Effective Gain (also represented as MEG) ratio is within ±0.5 dB. There is a twin‐sense circular polarisation in this antenna and superior isolation between resonating elements (greater than 18). The proposed antenna for human tissues specimens is also discussed with its specific absorption rate (also pronounced as SAR) in different situations that pertain to the living body. The overall size of the proposed ‘Circularly Polarised’ textile ‘Multi‐Input‐Multi‐Output’ antenna is 34:5 × 42 × 1 mm3. Because of its textile layers, reasonable performance, and compact size, the designed ‘Multi‐Input‐Multi‐Output’ antenna may be useful for wearable applications. The presented novel antenna can be made unrecognisable with a beautiful swan‐shaped design that can simply comingle with the other designs of fabric (in the fashion dress). The simulated antenna was made‐up following regular and general manual techniques and verified in the proposed conditions. The corner‐to‐corner distance between the ‘Multi‐Input‐Multi‐Output’ antennas is 14.2 mm, and the achieved isolation is beyond 18 dB after suitable adjustments of the designed final antenna.

Abstract In the study, a miniaturised printed quadrifilar helix antenna (PQHA) with isoflux coverage and wide‐angle circular polarisation is presented. It is composed of a three‐stage stepped impedance spiral arm and open stubs. Each of the three‐stage spiral arms has different pitches and number of turns. For the last‐stage spiral arm, meander lines are used. The proposed PQHA features the characteristics of wide bandwidth, isoflux radiation, small size, and wide‐angle circular polarisation. Moreover, in order to feed the proposed PQHA, a miniaturised quad‐feed network is designed to provide equal amplitude signals with sequential orthogonal phases. For demonstration, a prototype is designed, fabricated, and measured. The overall size of the proposed antenna is 88 × 88 × 132 mm (0.44 λ0 × 0.44 λ0 × 0.66 λ0). The results show that isoflux radiation with a coverage of about ±60° is realised from 1.40 to 1.62 GHz (14.6%) while maintaining more than 10 dB return loss and larger than 200° 3‐dB axial ratio beamwidth.

Abstract A switchable polarisation conversion/in‐phase reflection metasurface (PCIPR‐MS) based on a Pin diode is proposed in this study. By changing the working state of the Pin diode, the PCIPR‐MS can be used as a polarisation conversion metasurface (PCM) and an artificial magnetic conductor (AMC), respectively. Furthermore, the designed PCIPR‐MS can be arranged into a checkerboard surface to integrate with the antenna, which means that the PCIPR‐MS can be flexibly switched to control the radiation and scattering characteristics of the antenna in a time‐sharing manner. The simulation results show that the 3‐dB axial ratio (AR) bandwidth is 4.31 to 6.14 GHz (35%) with the application of the AMC as the metal ground plane of the antenna in the radiation state, and the right‐hand circularly polarised (RHCP) gain is enhanced by more than 1.5 dB from 4.65 to 5.80 GHz in a low‐profile compared with the reference antennas. By using the PCM, phase cancelation is achieved in the scattering state of the antenna to realise the low‐RCS characteristics.

Abstract Single‐layer ultrathin absorber patch elements are analysed under normal and oblique incidence. A compensation technique for impedance variation with an angle of incidence (θ) is proposed. An equivalent‐circuit model is formulated that provides a realisation for the absorption response (in terms of resonance frequency and absorption ratio) of non‐complicated rectangular patch absorbers using simple equations. The design methodology proposed is based on using multiple subcells of simple patches to add another degree of freedom for the design equations and keep the ultrathin planar feature. Previously reported techniques realising a wide angle of incidence are applied for fair comparison with the proposed methodology. The developed structure features angular stability, polarisation insensitivity, and a planar non‐complicated configuration compared with that of structures reported in literature. Moreover, a prototype is fabricated and measured to validate the proposed approach.

Abstract Scattering of the E‐polarised plane electromagnetic wave from two different but of the same‐period all‐dielectric rectangular bar gratings on substrates is analysed using a volume‐integral‐equation (VIE) method. Here, VIE is a Fredholm integral equation of the second kind with unknown function being the electric field in the gratings regions. Discretisation of the VIE is performed by applying an entire‐domain Galerkin technique. The developed algorithm possesses guaranteed convergence, provides accuracy, and is easily controlled by the order of discretisation. Numerical results for frequency‐selective reflection, manipulation of light to propagate in prescribed directions, and the ultrahigh‐Q lattice‐modes resonances are presented and discussed.

Abstract Scattering and absorption of the H‐polarized plane wave by the infinite grating of flat graphene strips are considered in the environment met most frequently—on or at the surface of a dielectric‐slab substrate. The full‐wave meshless code is based on the analytical semi‐inversion using the Riemann–Hilbert problem solution. This leads to a Fredholm second‐kind matrix equation for the Floquet harmonic amplitudes that guarantees code convergence and provides easy control of computational error, which can be reduced to machine precision. The matrix elements are combinations of elementary functions, and therefore, the code is accurate and quite economical. This enables computation of the reflectance, transmittance, and absorbance as a function of the frequency in the wide band from static case to 10 THz. Numerical results show that such a metasurface with micrometre‐sized strips is a composite periodic open resonator. It is highly frequency‐selective thanks to the interplay of three types of natural modes—low‐Q slab, moderate‐Q plasmon strip, and ultra‐high‐Q lattice—that do not exist in the absence of the substrate. Varying the chemical potential of graphene, one can manipulate the electromagnetic characteristics of the metasurface at a fixed frequency from almost total transmission to almost total reflection.

Abstract A rigorous theory is developed for the multiple scattering analysis of an E− polarised plane wave from an ensemble of 2‐D slotted arbitrary cylinders. The Method of Analytical Regularisation, previously applied to the solution of scattering wave problems for isolated slotted cylinders, is generalised to problems incorporating ensembles of closed or slotted cylinders. Numerical calculations of the complex eigenvalues, Q− factors and resonant current densities are performed for various configurations of two slotted circular or elliptical cavities, focussing on an accurate assessment of differing peculiarities of the mutual resonant electromagnetic coupling.

Abstract The diffraction of an E‐polarized plane wave from two finite sinusoidal gratings is investigated by a rigorous approach, based on the Method of Analytical Regularization. This allows us to analyse the problem in a wide frequency band without limitations on the depth of the sinusoidal corrugation, the wave size of the gratings, or their relative location. The homogeneous version of the equations obtained is used for accurate computation of the complex eigenvalues in an open resonator of Fabry–Perot type with sinusoidally corrugated strips. In the calculations, two types of structures were used: one is formed by parallel translation of the sinusoidally corrugated strips and the other is obtained by rotation of one of the strips in the first structure. For each relative location of the corrugated strips, the resonance excitation of the structure by an obliquely incident E‐polarized plane wave is considered. Based on the calculation of the surface current density for different incidence angles, their specific values for optimal excitation of the complex modes are established.

Abstract The Cauchy method of analytical regularisation, first in full explanation, is used for the modelling of the plane wave scattering by a flat pre‐fractal system of impedance strips. It is based on a modification of the singular integral equation technique and the correct type of inversion formula of the simplest Cauchy singular integral equation. The approach is effective for the plane H‐polarised electromagnetic (or sonic) wave scattering problems. The principle of strict mathematical orderings of the pre‐fractal strip grating deals with a five‐parts class of perfect fractal sets, which is characterised by a variable positive fractal dimension. Considerable attention is devoted to the asymptotic model of the plane wave scattering by a sparsely filled grating, which has an explicit solution. This result is very important for verification of the mathematical models presented and testing of direct numerical methods. The scattered electromagnetic field in the far zone is successfully analysed with the aid of the asymptotic solution derived for electrically narrow strips.

Abstract The Carleman method of analytical regularization is used to model the plane E‐polarized electromagnetic wave scattering by flat grating of a finite number of impedance strips. It is based on a modification of the singular integral equation technique, the perturbation method and the Carleman inversion formula for the simplest logarithmically singular integral equation. Attention is focussed on the asymptotic model of the plane E‐polarized electromagnetic wave scattering by a sparsely filled impedance strip grating. In this case, the corresponding singular integral equation system has an explicit solution. This result is important to verify direct numerical methods. The scattered electromagnetic field in the far zone is successfully analysed with the aid of the asymptotic solution derived for electrically narrow strips.

Abstract Large scale (i.e.

Abstract Given that the discrimination between the two senses of circular polarisation (CP) has been reported for cascades of progressively rotated wire‐grids, the author investigates whether or not the progressive rotation of the elements of a cascade would be the fundamental reason for the cascade to discriminate between the two senses of CP. The author also investigates whether or not the particular progressive rotation that consists in aligning each element of the cascade with the polarisation of a normally incident CP plane wave would necessarily provide the maximum discrimination between the two senses of CP. It is shown that neither progressive rotation nor alignment are fundamental or optimal for CP discrimination. CP discrimination is shown to be achieved even when the physical geometry of the CP antenna does not match the screw that is traced in space by the CP wave which is meant to be received/transmitted by the CP antenna. This observation is important to avoid misunderstanding the mechanism that underlies the phenomenon of CP discrimination.

Abstract This study presents a simple and low‐profile cylindrical dielectric resonator antenna (CDRA) for the fifth‐generation (5G) band (3.5 GHz) with switchable polarization. The antenna can operate with linear or circular polarization (right‐handed circular polarization [RHCP] or left‐handed circular polarization [LHCP]) by changing the states of the PIN diodes below the CDRA, while keeping the same operating frequencies. The antenna operates at three modes (Mode 1, Mode 2, and Mode 3). It exhibits linear polarization in Mode 1, RHCP in Mode 2, and LHCP in Mode 3. The 10‐dB bandwidths of 750 MHz (3.1–3.85 GHz), 950 MHz (3.03–3.98 GHz), and 960 MHz (3.03–3.99 GHz) are noted for Mode 1, Mode 2, and Mode 3, respectively. The 3‐dB axial ratio bandwidth of 22.2% (3.09–3.86 GHz) and 21.4% (3.08–3.82 GHz) is achieved for Mode 2 and Mode 3, respectively. The reported antenna has high gain ( >5.25 dBi for all operating modes) and high radiation efficiency ( >79.8% for all operating modes). The proposed antenna is suitable for use in polarization diversity applications.

Abstract The interaction of radar signals with a planetary surface is critical for the utility of radar data. Herein, a power‐law roughness spectrum is used to model the roughness and an inhomogeneous vertical permittivity to describe the dielectrics from the surface of Mars. Numerical simulations of depolarised radar backscattering are then conducted. To gain a more complete picture of depolarised characteristics, a wide range of surface roughness is considered. Results reveal that the depolarised backscattering is sensitive to the dielectric profiles with –10 dB is observed. The polarization conversion ratio, the ratio of depolarisation to total polarization backscattering, is a sensitive indicator of dielectric profiles and roughness, and thus is useful in retrieving dielectric profile.

Abstract In the present study, a novel periodic planar leaky‐wave antenna (PLWA) was designed, simulated, and fabricated based on the substrate integrated waveguide (SIW) technology. The antenna can scan the main beam from around −60° to +20° continuously with complete suppression of open stopband (OSB) by the sweeping frequency from 9.2 to 14.1 GHz. The proposed structure was designed to have circular polarisation (CP) in the entire operating frequency range, where the broadside or centre frequency is 12.25 GHz. Antenna gain in the broadside frequency is around 13 dBi. The radiation efficiency of the structure is improved and equalised through broadside, which is around 80% in the frequency band of operation. Also, series and shunt analysis was applied to the proposed periodic PLWA in the fundamental TE10 mode. In the next step, the asymmetric was applied longitudinally and transversely to the proposed structure to achieve OSB elimination combined with circular polarised radiation simultaneously. The equivalent circuit of the proposed structure was extracted and, finally, the antenna was fabricated. Based on the results, excellent agreement was observed between the measured, modelled, and simulated results.

This study discusses the design of a low-profile metamaterial-based antenna consisting of a 3 × 5 array of Hilbert shaped unit cells organised as a rectangular patch. The antenna is backed by with a partial ground plane loaded with square electromagnetic band gap defects for energy harvesting applications in the context of ultra-wideband self-powered wearable wireless devices. The antenna is mounted on a 28 × 32 mm FR4 substrate, with a thickness of 0.394 mm, a relative permittivity of 4.2 and a loss tangent of 0.02. The antenna is also printed on a flexible solar panel for self-powered devices through solant–rectenna output terminals. The proposed solant–rectenna is found to cover the frequency range from 0.8 up to 10 GHz. The I–V characteristics of the solar panel are measured with and without the antenna structure to realize low shadowing effects. After that, the solant radiofrequency (RF) port is connected to a rectifier circuit to create a rectenna port that collects the RF energy and converts it to an output DC voltage at 0.915 GHz. It is found that the proposed rectenna provides an output DC voltage of 1.42 V with a conversion efficiency of 90%.

In radar systems, transmitting and receiving waveforms with different polarisations benefit to acquire complete information about the target and its environment, ensuring significant enhancement of the radar's performance. Here, the authors consider the optimisation problem of jointly designed transmitter and receiver (TR) polarisation from the view of target scattering estimation. Under the condition that the target and clutter scattering covariance is known as a prior, they first use sequential linear minimum mean square error estimation to obtain the target scattering matrix and then optimise the sensing vector, which contains the polarisation information under the constraint of minimising the mean square error. The mentioned problem can be solved by eigenvector decomposition. Then, a method to get the TR polarisation parameters is provided. Finally, they use numerical simulations to show the advantage of the proposed methods.

A 1 × 4 low-loss frequency scanning planar array with hybrid feeding structure in Ku-band has been designed. In order to improve the array efficiency, the planar array was designed by four parallel sub-arrays and the waveguide slow-wave line structure with electromagnetic coupled slot on narrow side was used as feed line. The results of simulation show that, except at the centre frequency, the voltage standing wave ratio of the antenna array is below 1.2 at the operation band, the range of the scanning angles is (−30.5°, 29°), the beam width of the antenna is about 5.5°–6.6°, the sidelobe is below −20 dB, and the gain is more than 30 dBi.

Polarisation is an inner property of electromagnetic wave. It has considerable significance to analyse the polarimetric feature of targets in target recognition and classification applications. Slant 45° dual polarisation measurement is widely used due to its low requirements on system complexity and data rate on the one hand, and good polarisation measure and anti-interference capabilities on the other. However, its performance is seriously affected by rotation angle of the polarisations in transmission and reception. Here, the impact of rotation error of the transmit–receive polarisations on feature extraction is assessed by theoretical derivation at first. The variations with rotation angles of the transmit–receive polarisations are then simulated using standard scatterers and ground targets data. This permits quantification of the resulting rotation error on slant 45° dual polarisation measurement. The impact of the rotation error on H/α and polarimetric similarity features is also quantified in results. Some practical advices on system design, calibration, and feature application are given at last.

This study researches the potential benefits of clutter suppression in polarisation filtering technology. In the author's laboratory, the antenna of the experimental system has been designed, called dual-polarised Yagi-Uda antenna and the antenna can receive both horizontal and vertical polarisation simultaneously. The experimental results show that the method of improved polarisation filtering can suppress the clutter effectively, which is composed of direct-path signal and multipath clutters.

A compact ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna is presented. The MIMO antenna consists of four monopoles which are printed on FR4 substrate, whose impedance bandwidth is from 2 to 12 GHz, and the isolation of two adjacent antennas is less than−20 dB in mostly frequency band. The current distribution of the antenna is discussed by simulation, and the radiation characteristics of the antenna are improved by increasing the parasitic radiation patch and digging holes in the radiation patch. Four monopoles are placed with polarisation orthogonality, and the adjacent units are separated by slot to cut off the coupling current on the floor, thus effectively improving the isolation of the antenna.

A novel compact design of a circularly polarised corner-slotted microstrip antenna for satellite and synthetic aperture radar (SAR) applications is presented. A single-feed is used to excite a single-square patch with two L-shaped slots added at the upper right corner and at the opposite lower left corner (or at the other two corners) to achieve circular polarisation (CP) radiation. The proposed antenna has a simple shape, straightforward fabrication, and low cost. The impedance bandwidth (10 dB return loss) is ∼600 MHz at 8.1 GHz. An axial ratio bandwidth of 170 MHz is realised. The importance of the axial ratio 3 dB bandwidth is emphasised. In addition, an analysis for the direction of rotation of the CP is given. The experimental results have a reasonable agreement with the simulation.

This study proposes a joint sparse algorithm based on Bayesian compressive sensing to improve full polarisation inverse synthetic aperture radar (ISAR) imaging performance. The proposed method not only uses the sparseness of each single channel polarisation, but also takes into account the correlation of amplitude information between single-polarised channels. Through the comprehensive use of single channel polarisation imaging results, a better full-polarisation imaging result is achieved. Simulation results are used to verify the effectiveness of the method.

Although many different kinds of polarisers have been extensively studied in the last 20 years, most previous designs were passive and single-functional designs. In this study, a kind of a new active polarisation converter is designed. The active polarisation converter is comprised of periodically arranged circular ring embedded with PIN diodes. Four different results of polarisation transformation and reflection can be presented by controlling the bias voltage of the PIN diodes. The full-wave simulation results show that the proposed metasurface can rigorously satisfy the asymmetric transmission and can achieve cross-polarisation conversion with high efficiencies for linearly polarised waves. In addition, there is another particularly obvious advantage of the proposed structure is its broad operation bandwidth in microwave band, the bandwidth of the polariser reaches 70%, more than 90% cross-polarisation conversion efficiency is observed from 6.5 to 13.5 GHz.

Here a dual-polarisation printed dipole antenna for spherical near-field measurements is proposed. The printed dipole employs double-layered structure to obtain low cross-polarisation and uses irregular patch to get wide bandwidth. Two such dipoles are cross arranged to form a dual-polarisation dipole antenna. Simulated results show that the bandwidth is over 72% when VSWR is less than 3, the cross-polarisation ratio is better than 30 dB, the port isolation between two dipoles is better than −26 dB, while good radiation performance is also obtained. All the results above prove that the crossed arrangement structure will not affect the performance of the printed dipole, and the strength of mutual coupling between probes can be neglected.

Detection of corona discharge of the transmission line can reflect its health status and provide warning information for maintenance. Some existing detection methods are flawed and cannot be used widely. This study presents a new method by measuring the electromagnetic wave caused by corona discharge with RF antenna. Then a circularly polarised log-periodic antenna was designed by making two pairs of log-periodic antennas 90° orthogonal. Finally, this antenna was simulated and manufactured to detect electromagnetic signals, the result shows that the time domain signal of corona discharge is a high frequency oscillation wave and its fast Fourier transform main distributes between 200 and 350 MHz.

A method to excite dual band for a microstrip antenna on a two-layer substrate by combining the proximity feed and the inset feed in a simple way is presented. Both linearly polarised and circularly polarised (CP) dual-band waves can be excited. The CP antenna consists of two stacked perturbed patches. If the lower patch were directly connected to the feed line, it is hard to form two bands. A single resonant frequency is found dependent on the size of the lower patch and is insensitive to the loading effect of the upper patch. The lower patch is inset coupled to the feed line. The authors found that two bands can easily be excited. To demonstrate the idea, a dual-band global positioning system antenna is designed and tested. The achieved impedance bandwidths are 60 MHz centred at 1215 and 65 MHz centred at 1563 MHz. The 3 dB axial-ratio bandwidths are 15 MHz centred at 1228 and 20 MHz centred at 1575 MHz.

The design of spectrally-efficient, high-throughput satellite (HTS) systems with capacity approaching one terabit per second requires operating at Ka-band frequencies and above, where there are several gigahertz of allocated radio spectrum, using multiple spot beams with dual orthogonal polarisation mode. At these high frequencies, rain attenuation poses a major obstacle to the design of high-availability satellite links which are needed for the realisation of ubiquitous broadband multimedia communication services including high-speed Internet access at rural and remote locations. Furthermore, depolarisation-induced interference in such systems could have a performance-limiting impact if a co-channel cross-polar signal combines with system noise to drive the carrier-to-noise-plus-interference ratio (CNIR) below an acceptable threshold. This paper employs real measurement data to investigate the impact of depolarisation-induced interference on dual-polarised HTS systems for temperate and tropical climatic regions. Scenarios that cause significant system performance degradation are analysed, including the effects of signal frequency, antenna size, and regional rainfall rate. The impact of depolarisation on system performance is quantified by the reductions in the CNIR and link availability of a dual-polarised system when compared with those of a similarly-dimensioned single-polarised system.