For the local convergence phenomenon in the multiobjective evolutionary algorithm based on decomposition (MOEA/D) when applied to multiconstraint sparse array optimization, a multiconstraint evolutionary algorithm based on decomposition (MCEA/D) is proposed in this communication. Unlike MOEA/D, which constructs subproblems through weighted aggregation of multiple objectives, MCEA/D converts objective functions into constraints while retaining a single objective function, generating subproblems via constraint value space decomposition. Consequently, MCEA/D performs optimization within different constraint subspaces, with each subproblem operating in its own search space. This novel approach effectively mitigates the diversity loss and premature convergence issues of MOEA/D caused by the shared search space among subproblems. The results of uniformly excited concentric ring sparse array (CRSA) optimization demonstrate that MCEA/D can successfully identify feasible Pareto fronts (PFs), outperforming MOEA/D algorithm in this capability. Electromagnetic simulations validate the results.

This letter presents a scannable directional modulation secure communication method based on a single-sideband time-modulated array. By optimizing the modulation parameters that generate equivalent amplitude-phase weighting for each antenna element in the radio frequency channel, the main beam of the first-order harmonic and nulls of higher order harmonics are simultaneously steered toward the desired direction. This enables efficient transmission of signals with bandwidths exceeding the modulation frequency. Furthermore, in contrast to conventional approaches, the proposed method incorporates the degree of harmonic energy aliasing across all orders at nontarget directions into the optimization objective, thereby enhancing signal distortion and ensuring robust information security at these directions. Numerical simulations validate the feasibility of the proposed method. Experimental results demonstrate that the communication bit error rate decreases to as low as 1 x 10(-4 ) at the target communication direction, whereas it exceeds 30% at all nontarget directions within -40 degrees to 40 degrees.

This paper introduces a broadband four-port fullspace two-dimensional scanning phase-mode antenna based on spoof surface plasmon polaritons (SSPPs) structures. By leveraging folded multi-branch SSPPs radiators and multi-port feeding with phase-mode excitation techniques, the proposed design achieves flexible and precise full-space beam scanning. Through the integration of a four-port feeding network and a specially designed radiation structure, the antenna facilitates continuous 2D beam scanning across the entire nearhemispherical space. The prototype exhibits a broad operating bandwidth from 2.01 to 3.21 GHz (corresponding to a fractional bandwidth of 46.3%), corresponding to a fractional bandwidth of 46.3%, while occupying a compact electrical size of approximately $0.35 \lambda \times 0.35 \lambda({@} 2.61 \text{GHz})$. Additionally, active S-parameters remain below −10 dB throughout the operational frequency range of 2.44–3.12 GHz.

In this article, a single-channel frequency-modulated continuous-wave (FMCW) radar based on a 1-bit time-modulated array (TMA) is proposed. By utilizing the spectrum folding phenomenon introduced by harmonics dechirping, the frequency spectrums of beat signals generated by different harmonics are distributed in independent frequency areas, thereby avoiding target ambiguity caused by spectrum crossing and achieving the single-channel estimation of target range, velocity, and direction. The theory of range, velocity, and direction estimation based on the multiharmonic power reconstruction (MHPR) method is established. Meanwhile, the constraint condition among modulation frequency, target range, and target velocity for avoiding target ambiguity is derived. Compared with conventional single-channel FMCW radar based on switched antenna array (SAA), which employs time-division multiplexing, the proposed system improves the array reception efficiency significantly by using 1-bit time-modulation modules to enable all antenna elements to simultaneously receive echo signals. Moreover, the advantage of the proposed system is that the echo signals are received continuously in the time domain, which avoids the velocity-direction coupling problem introduced by time-division reception in a conventional single-channel system. Hence, the independent detection of range, velocity, and direction for high-speed moving targets can be achieved in the proposed system. Numerical simulations are provided to verify the performance of the proposed system, and a C-band eight-element 1-bit TMA is constructed to experimentally verify its feasibility. Simulation results show that compared with the SAA radar, the beat signal power is increased, and the beat frequency estimation error is reduced. The direction-finding accuracy is improved for high-speed targets.

The synthesis of separable uniform cylindrical arrays (SUCAs) remains challenging because decomposing a target pattern into independent uniform linear array (ULA) and uniform circular array (UCA) components is ambiguous and undermines accurate control of the overall pattern. To overcome this, an alternating fast segmented cyclic convolution and fast Fourier transform (AFSCC-FFT) method is proposed. The method models a SUCA as an equivalent UCA with an iterative update element pattern incorporating the ULA factor and the basic element pattern. Thus, the transformations between array pattern and excitations are accelerated by performing inverse FFT and FFT for the ULA part, as well as performing fast segmented cyclic convolution (FSCC) and inverse FSCC for the equivalent UCA, achieving low computational complexity. Pattern constraints are achieved by developing an alternating pattern update strategy that iteratively updates the ULA and equivalent UCA patterns, jointly accounting for both subarray contributions to the total pattern, which effectively avoids amplitude and phase ambiguities used in conventional forced pattern decomposition. Numerical examples and full-wave simulations are conducted to validate the efficiency and accuracy of the proposed method, as well as its superiority over existing approaches.

This paper proposes a circularly polarized (CP) endfire helical leaky wave antenna (LWA) based on multipole elements. The antenna employs helical double-sided parallel stripline (DSPSL) to form a compact dense helix structure. By exploiting the inherent differential current characteristics of helical DSPSL and implementing a phase-reversal crossed helix structure, the multipole element is constructed, featuring unidirectional radiation for directivity enhancement. Another crossed structure with minor phase perturbance is further introduced to form the modified multiple element for improved axial ratio (AR) performance. Subsequently, a CP endfire helical LWA is constructed by periodically arranging such modified multipole elements. An antenna prototype is fabricated with stainless steel through 3D print technology and tested for validation. Measurement results demonstrate that the antenna achieves a high directivity of 16.78 dB with dimensions of 4.97 λ₀ × 0.30 λ₀ × 0.30 λ₀. The measured peak gain is 13.02dBiC with a front-to-back ratio of 16.1dB. The measured -10dB impedance bandwidth and 3-dB AR bandwidth both covers 1.75-1.9GHz. Error analysis indicates that higher gain results could be acquired, if materials of higher conductivity can be applied in fabrication with smaller deformation errors. The proposed design can find applications in high-resolution radars and long-distance communications.

In this article, an all-metal high-efficiency dual-port phase mode antenna (PMA) is proposed. By adjusting the phase difference between the two ports in the PMA, distinct characteristic modes are excited, enabling a continuous transition of the radiation pattern from a conical beam to an axial beam. Consequently, the PMA achieves element-level 2-D beam steering, with the main beam capable of scanning within +/- 45 degrees in the xoz plane and +/- 48 degrees in the yoz plane. Furthermore, high port isolation exceeding 30 dB in the dual-port PMA is achieved by introducing a novel decoupling technology, named the evanescent-wave-based decoupling method. Due to its all-metal structure and high port isolation, the PMA maintains a total efficiency exceeding 98% under all excitation conditions. To validate its potential for high-efficiency wide-angle scanning, a 4 & times;4 planar phased array based on the PMA is designed and fabricated. By employing enlarged element spacing and introducing the defected ground structure (DGS), mutual coupling between array elements is significantly reduced, resulting in improved array efficiency. The experimental results demonstrate that the 4 & times;4 array achieves wide-angle beam steering of +/- 66 degrees in the xoz plane and +/- 90 degrees in the yoz plane, with a total efficiency ranging from 79% to 94.5%.

This article presents a broadband all-metal slot array antenna based on a concave-convex array (CCAA) layout. The CCAA offers significant reduction of radar cross section (RCS) but suffers from coupling that limits radiation performance. To address this, the open rectangular resonant slots (ORRSs) are employed to suppress induced wall currents and restore bandwidth, patterns, and gain. A $4 \times 4$ prototype was designed, fabricated, and tested. Both simulation and measurement confirm a 10-dB impedance bandwidth (IBW) of 43.5% (7.9-12.3 GHz) with radiation comparable to a planar array (PAA). In addition, relative to the PAA, the decoupled CCAA achieves 10-dB RCS reduction bandwidths of 35% and 15% under X- and Co-pol. incidences. These results verify that the ORRS-based decoupling design enables the CCAA to simultaneously realize broadband radiation and low observability.

In this letter, a harmonic equalizer to mitigate aliasing-induced inter-harmonic interference in time-modulated arrays (TMAs) is proposed, which conventionally restricts the usable communication bandwidth. By prepending a pilot signal spanning the integer modulation period to the communication signal at the transmitter, the harmonic characteristics of the TMA channel can be estimated at the receiver. Leveraging the consistency between the pilot and communication signal, a harmonic equalizer is designed to redistribute the signal energy across harmonics, suppress undesirable harmonic components, and concentrate the information in the fundamental band. This effectively suppresses inter-harmonic interference, thus decoupling the communication bandwidth from the modulation frequency, which enables higher data rates within modulation-frequency-limited TMAs.

In this article, a single-channel detection method combining pulse compression and time-modulated technology with wideband linear frequency modulation (LFM) signals is proposed. To solve the range ambiguity caused by the bandwidth of the LFM signals being larger than the modulated frequency, a pulse compression network is proposed to estimate the targets' range based on the variations of cumulative pulse power compressed by the network. With the characteristic of peak-to-peak power difference after pulse compression for the modulated signals, the targets' range information can be extracted from the pseudo-peaks formed by the harmonics. By combining the harmonics' power relationship extracted from echo signals with range information, the direction of the target can be accurately estimated. Therefore, the detection system takes advantage of both a simple structure and high range resolution. To validate the effectiveness of the proposed algorithm, the numerical simulations and the experimental results of a transceiver system using an eight-element time-modulated array (TMA) working at C-band are presented.

A reconfigurable leaky wave antenna (RLWA) with a low-profile ground plane is proposed, utilizing mode-switchable units with multifeed patches to enable fixed-frequency beam scanning. Each patch element is equipped with three feed lines on both left and right sides, with individual p-i-n diode integration for each feed line. By controlling the bias states of the p-i-n diodes, different operating modes-each corresponding to distinct phase constants-are excited. An equivalent circuit model of the proposed unit has been established and investigated, demonstrating the corresponding leaking radiation characteristics. The RLWA is composed of a series of mode-switchable unit cells, enabling dynamic beam scanning by controlling the bias states of the PIN diodes to switch the operating modes of each unit. A prototype of the RLWA comprising 10 units was designed and fabricated. It achieves beam scanning from-62 degrees to +60 degrees with a peak gain of 12.9 dBi at 5.3 GHz. The antenna features a simple feeding structure, requires fewer tunable components, maintains an extremely low profile of 0.03 lambda, and offers cost-effective fabrication and easy integration. By employing simple PIN diode switches, the proposed RLWA achieves high-gain, wide-angle beam scanning capability, demonstrating great potential for wireless communication and radar applications.

Calibration is essential to ensure the optimal performance of phased arrays, as amplitude and phase mismatches degrade radiation characteristics. While amplitude-only calibration methods are attractive when direct phase measurements are infeasible, traditional techniques often suffer from high measurement overhead. This article proposes a fast rotating-element harmonic electric-field vector (fast REHV) calibration method, which achieves calibration with minimal measurements and lowest-resolution (e.g., 1-bit) phase shifters. This method applies periodic modulation to the phase shifters of both the reference and test channels at the same frequency, withthetest channel's modulation sequence delayed by a quarter of the period relative to the reference channel. This time delay induces precise phase shifts at harmonic frequencies, where the +1, +2, and +4 harmonics generated by the reference channel exhibit relative phase shifts of 90 degrees, 180 degrees, and 0 degrees, respectively, compared to the test channel. Therefore, phase calibration between these two channels can be completed solely by measuring these harmonics' amplitude only once, while amplitude ratios are determined using different modulation frequencies. Since phase shifts are generated through time delays rather than direct phase adjustments, the method is inherently robust to phase shifter errors. Moreover, by utilizing only the harmonic components produced by modulated elements, the calibration accuracy remains stable regardless of array size, making it well-suited for large-scale phased arrays. Experimental results confirm the effectiveness of the fast REHV method, with harmonic phase errors below 0.57 degrees, over-the-air (OTA) phase errors within 2 degrees, and amplitude errors within 0.44dB, along with notable improvements in main lobe gain and sidelobe suppression.

A high-precision time-modulated module (TMM) based on power cancellation method is proposed in this article. It breaks through the constraint on the minimum controllable duration of radio frequency (RF) signal, which is constrained by the finite physical characteristics of RF switches. The proposed power cancellation TMM (PCTMM) independently controls two RF signals with equal amplitude and 180° phase difference, creating an equivalent absorption state in the overlapping area through power cancellation, while nonoverlapping segments are preserved as the on-state. As a result, the minimum controllable duration of the RF signal in the PCTMM is determined by the pulse-delay resolution of the modulation signals generated by a field-programmable gate array (FPGA), which is shorter than that in conventional TMMs (CTMMs). This enables improvement in achievable amplitude modulation precision, modulation frequency, and signal bandwidth of the PCTMM. A PCTMM operating at 2.36GHz was designed using RF switches with a cumulative rise and fall time of 8.9ns. The measured results demonstrate accurate amplitude modulation, with root mean squares (RMSs) attenuation errors for the fundamental and +1st harmonic components below 0.4 and 0.93dB, respectively, even at 1% duty cycles and 50MHz modulation frequency. Under the same conditions, a CTMM using an identical switch exhibited rms errors of 1.36 and 1.77dB, respectively, and failed to operate below a 7% duty cycle. The total efficiency of the proposed PCTMM is about 3.51% at a 50% duty cycle. This high-precision modulation capability is achieved at the expense of total efficiency. An eight-channel array incorporating the PCTMMs suppressed sidelobe level (SLL) to −39.03dB at a modulation frequency of 20MHz.

In this article, a novel dual-port phase mode antenna (PMA) based on folded fishbone structure is proposed and is applied in phased arrays to achieve wide-angle scanning with polarization switching ability. The PMA antenna mainly consists of a folded fishbone structure placed above a ground plane with two ports feeding at two ends. The main radiating structure can be divided into three basic parts: the vertical part, the horizontal part, and the split ring part, which can be treated as vertical electric currents, horizontal electric currents, and equivalent magnetic dipoles, respectively. Different radiation patterns can be synthesized by those three types of radiating currents under different amplitude and phase conditions, which are controlled by the excitation states of the dual ports. In-phase and out-of-phase excitation states are analyzed for polarization switching in yOz plane, and the other intermediate states are analyzed for pattern reconfiguration in xOz plane. The proposed PMA is extended to a linear array to achieve 2-D scanning with polarization switching ability. To validate the design, a PMA element and a 4-element linear array are fabricated and tested. The measured results show that the antenna can achieve an effective working band of 2.2-2.6 GHz with impedance band and pattern band both as criteria. The proposed PMA exhibits quasi-conical vertical polarization (VP) radiation under in-phase excitation and broadside horizontal polarization (HP) radiation under out-of-phase excitation. The extended linear array achieves wide-angle scanning from broadside to 71 degrees in yOz plane with polarization switching. The HP beam scans from broadside to 46 degrees with gain ranging within 9.88-11.66 dBi and the VP beam scans from 54 degrees to 71 degrees with gain ranging within 5.72-6.83 dBi. The 3-dB beamwidth of the VP scan beam can cover endfire direction, which could be advantageous in practical use. The linear array can also scan from broadside to 43 degrees in xOz plane with HP beam and the measured gain ranging within 9.91-11.93 dBi. The proposed PMA and extended array can find applications in vehicular communication requiring wide beam coverage with polarization switching ability.

This article presents a novel four-port phase-mode antenna (PMA) featuring a folded comb-structure with a centrally gapped configuration. Compared with previously reported PMAs, the proposed design achieves independent control of the main lobe direction and polarization states while enabling multipolarized beam scanning with near-hemispherical spatial coverage. Through the integration of four monopoles at both ends of the folded comb-structure, we generate two distinct spoof surface plasmon polariton (SSPP) wave groups within a single aperture. The orthogonal polarization states inherent to the SSPP even and odd modes provide polarization diversity through hybrid mode combinations. Continuous 2-D beam steering with arbitrary polarization was achieved by adjusting the feeding phase difference between SSPP wave groups. Experimental results demonstrate multipolarization capabilities, including Phi-polarized, theta-polarized, and left-/right-hand circularly polarized radiation patterns across near-hemispherical scanning ranges (>150 degrees in the xoy-, xoz-, and yoz-planes). A four-element staggered array implementing the PMA element and the generalized principle of pattern multiplication (GPPM), furthermore, achieves extended scanning ranges of +/- 115 degrees (xoz-plane), +/- 90 degrees (yoz-plane), and full 360 degrees coverage (xoy-plane), while enabling multipolarized 2-D beam scanning functionality.

In this letter, a novel high-gain low-profile circularly polarized endfire leaky-wave antenna with binary codification is proposed. The antenna is based on the double-sided parallel strip line (DSPSL), which loads periodic metal vias for endfire vertically polarized radiation and pairs of horizontal stubs for endfire horizontally polarized radiation. To balance the amplitude ratio and phase difference between horizontal polarization and vertical polarization, the strip of DSPSL in one period is divided into 16 x 8 grids. Each grids has two states. By optimizing the state of each grid, the amplitude ratio is close to 1, and the phase difference is close to 90 degrees, and then, excellent endfire radiation with circular polarization is realized. The proposed antenna is fabricated, and the measured impedance bandwidth is from 5.6 GHz to 6.2 GHz with reflection coefficient being less than-11.9 dB and 3 dB axial ratio bandwidth is from 5.61 GHz to 5.92 GHz. The size of the antenna is 5.88 lambda(0)x 0.83 lambda(0)x 0.077 lambda(0), and the peak gain is 11.5 dBi.

A symmetric tri-port phase mode antenna (PMA) based on radial spoof surface plasmonic polaritons' (SSPPs') structure and two kinds of 1-D linear arrays of it are proposed with extended 2-D scanning characteristics. The proposed tri-port PMA is composed of a horizontal metal ground, a parallel circular PCB ( 0.28 lambda x 0.28 lambda), and feeding pillars connecting them. The radial spoof surface plasmonic polaritons' (SSPPs') scatterer and three feeding spiral arms excited by three isolated ports are printed on each side of the PCB. The three ports generate similar hybrid EM modes with only angular differences, which can be separated into fields equivalent to those excited by a horizontal and vertical current element by the SSPPs' scatterer. The superposition of fields with two controllable independent phased differences contributes to 2-D scanning patterns of the PMA, which further facilitates wide-range 2-D scanning characteristics of two kinds of 1-D arrays applying the generalized principle of pattern multiplication (GPPM). Beam scanning ranges - 92(degrees) <= theta(m) <= 92(degrees) and 92(degrees) <= theta(m) <= 91(degrees) are realized by two 1x4 linear arrays with a peak gain of 11.5 dBi and a gain fluctuation of 4.9 and 4.7 dB. The extra independent channels and scanning properties of the presented PMA and its arrays can be further exploited for more promising applications such as communication, direction finding, and navigation systems.

With the growing complexity of communication systems, the development of efficient and intelligent jamming techniques has become a critical requirement in electronic countermeasure scenarios. In this paper, a broad coverage dynamic jamming method based on space-time modulated metasurface (STMM) is proposed. By leveraging digital control, time and space modulation can be imposed on the incident signal, enabling precise control over the beam direction and the radiation characteristics. The adaptive generation of in-band aliasing harmonics enables frequency-following jamming across multiple directions, without the need for prior signal detection. The proposed method is validated through theoretical model and numerical simulations, providing a novel technique foundation for the development of intelligent communication jamming systems.

A planar quad-port phase mode antenna (PMA) based on radial spoof surface plasmon polaritons (SSPPs) radiator and two arrays of it are proposed with extended 3-D scanning and polarization controlling characteristics. The proposed quad-port PMA is composed of a tri-layer PCB with a grounded SSPPs radiator, four feed patches, and the ground. The four isolated ports generate similar hybrid EM modes with structural angular differences and phase differences applied on the ports. The superposition of fields with three controllable independent phased differences contributes to a scanning range of -66(degrees)<=theta(me) <= 66(degrees) in both xoz plane and yoz plane, and controllable polarization variation with polarization ratio shifting from 0.6 to 21.3 dB in the main lobe width, which further facilitate wide-range 2-D scanning and polarization controlling characteristics of arrays through generalized principle of pattern multiplication (GPPM). Scanning range -71(degrees)<=theta(m)<= 71(degrees) in xoz plane with extremely low gain fluctuation 2.4 dB within -60(degrees)<= theta(m)<= 60(degrees ) and aperture efficiency 98% at theta(m)=0(degrees ) and scanning range -65(degrees ) <= theta(m)<= 65(degrees) in yoz plane are realized by the 1x 4 linear array. Scanning range -65(degrees ) <= theta(m)<= 65(degrees) is realized by the 2x 2 array with aperture efficiency 98% at theta(m)=0(degrees) . The wide-range scanning properties of the presented arrays can be further exploited in large-scale 2-D arrays for more promising applications.

In this letter, an effective decoupling strategy with multiple lumped and distributed hybrid elements is proposed to enhance isolation between tightly placed stacked patch antennas. To start with, a novel capacitor-loaded defect ground structure and a lumped inductor are combined to adjust antenna system's differential mode (DM) impedance. Then, a metal strip grounded with two lumped capacitors, is employed to tune common mode (CM) impedance to coincide with that of DM, thus implementing excellent reduction of mutual coupling. Here, more importantly, through equivalent magnetic-current analysis, it is found that the CM and DM impedance of mirrored and translated stacked patch antennas alternatingly correspond to each other. Thereby, the proposed method demonstrates effectiveness for stacked patch antenna pairs with mirrored and translated arrangements. To validate the concept, a prototype is fabricated and measured. The experimental results manifest that original poor isolation of -5 dB is significantly enhanced to better than -20 dB over -10-dB impedance bandwidth of 3.30 GHz to 3.80 GHz (14.1%), with a close center-to-center spacing of 0.24 lambda(0).