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A novel antenna with the combination of the shorted-edge patch and the coupling feed is proposed in this letter. This new combination still keeps the good features of patch antenna, such as low cost and easy integration. Moreover, it simultaneously possesses several useful features: low cross polarization, wideband, high gain, and adjustable beamwidth in design. To show the effectiveness, a prototype operating at the central frequency of 12.5 GHz is designed and measured. Good agreement between the simulated and measured results has been obtained. The gain and the cross-polarized level are 11.2 dBi and −40 dB, respectively, and the bandwidth is 35%.

Single-sideband time-modulated phased array (STMPA) provides beam-scanning capability and eliminates some undesired sidebands. To further improve the frequency spectrum, the time modulator of the STMPA with S -step waveform for better eliminating the undesired sidebands and widening the allowable signal bandwidth without aliasing is proposed in this letter. The S -step waveform is realized by digital attenuators in time modulators. Most of sidebands are eliminated and the allowable signal bandwidth becomes 4 S times as wide as that of conventional time-modulated array (TMA). The general expressions of the sideband level (SBL) and the theoretical loss of the time modulator related to the number S of the steps are given. To experimentally verify the feasibility of the proposed design, the time modulator with four-step waveform and the corresponding four-element STMPA are fabricated and measured.

Vaporized samarium (Sm) has been released in the ionosphere for artificially creating plasma clouds, which may be tailored as radio wave reflectors for over-the-horizon communications. The model of samarium releases needs to be further refined for filling the gap between experimental observations and theoretical simulations. A sophisticated simulation model, so far to date, for samarium release in the ionosphere has been developed, and the redundancy reaction, inversion, and the photochemical reactions are all taken into account. The model results are consistent with experimental observations. Due to the geomagnetic field and neutral wind, the shape of artificial plasma clouds significantly changes. The error of the spherically symmetric reflection model is large. According to the density distribution of plasma clouds, the geometric theory of diffraction (GTD) is introduced here to deal with the electromagnetic scattering. The GTD-based scattering model has been established and used to study the time–space evolution of the ground-received power patterns in this article.

This article presents an enhanced single-sideband time-modulated phased array (ESTMPA) using modulating pulses with stepped waveforms. Based on the in-phase/quadrature (I/Q) complex modulation technique, this phase-only weighting array generates a scanning beam at the 1st sideband. The proposed modulating pulses realized through a reconfigurable power divider in I/Q time modulator can avoid the power loss from the switches during switch-OFF state and eliminate the maximum undesired sideband—the 5th harmonic in STMPA. As a result, it brings a power spectrum with less undesired sidebands, lower sideband level (−16.9 dB), higher harmonic efficiency (94.96%), and wider allowable signal bandwidth (eight times as wide as that of the conventional time modulated array). To experimentally verify the feasibility of the proposed design, a wideband enhanced I/Q time modulator and its corresponding eight-element ESTMPA are designed and manufactured. A detailed study on the effect of the magnitude and phase deviations in the circuit and the transition period of modulating pulse are presented. The measured results of power spectrum and radiation pattern have a good agreement with the simulated ones.

A low-profile differentially fed microstrip patch antenna with broad impedance bandwidth is proposed by incorporating a resonant mode of the slot into TM10 and TM12 modes of the patch resonator. Initially, the shorting pins are symmetrically placed underneath the patch so as to push up the resonant frequency of TM10 mode in proximity to that of TM12 mode ( f 12). After that, the central slot could be employed to excite an additional mode resonating closely to the f 12 by increasing the slot length. Additionally, a pair of small circular disks is introduced below the radiating patch for good impedance matching. Finally, the wideband antenna is fabricated and measured to validate the predicted performance. The results illustrate that the antenna has gained a broad impedance bandwidth of about 55% (1.62–2.85 GHz) with three in-band attenuation poles while maintaining the normal radiation pattern. In particular, a low-profile property with the height of about 0.06 free-space wavelength is achieved.

A planar dual-band array with orthogonal circular polarizations (CPs) in the two frequency bands is proposed in this communication. The array is implemented on a single-layer substrate and easy to be extended to the design of a larger array. A new antenna element for such an array is exploited by symmetrically loading stubs on the edges of a square patch. In this communication, two pairs of orthogonal modes of the patch, namely, TM10/TM01 and TM30/TM03, are excited simultaneously and used to realize different senses of CP radiation in the two bands. An equivalent transmission-line model of this patch is then developed to describe its working principle and design procedure. To validate its effectiveness, a $2 \times 2$ -element array prototype operating at 2.53 and 3.59 GHz is designed and fabricated. Both the left- and right-hand CPs are obtained simultaneously in the dual bands, and the measured results are found to be in good agreement with the simulated ones. The measured radiation gains in the lower and higher bands are 10.8 and 12.5 dBic, respectively.

A single-layer microstrip-fed patch antenna with capabilities of both bandwidth enhancement and harmonic suppression is proposed. For this purpose, a pair of $\lambda $ /4 microstrip-line resonators is introduced and coupled in proximity to a rectangular patch. The wideband property can be obtained by making effective use of the two resonances introduced by the radiating patch and nonradiating $\lambda $ /4 resonators. Different from other reported dual-resonance patch antennas, the proposed antenna does not require the electrically thick substrate, so it has attractive low-profile property. Thanks to the good features of $\lambda $ /4 resonators and capacitive feeding scheme, harmonic radiating modes of the patch antenna can be significantly suppressed as highly demanded in modern highly integrated communication systems. The working principle, equivalent circuit, and design procedure are extensively described. Finally, a prototype antenna operating at 4.9 GHz is designed and fabricated. The measured results show that its bandwidth is 2.7 times wider than that of the traditional insert-fed patch counterpart, and the harmful spurious radiation from other higher order radiating modes has been effectively suppressed.

This paper presents a new approach to implement planar shared-aperture dual-band dual-circular polarization (CP) array antennas. The antennas can be fabricated on a single-layer substrate and extended to a larger array easily. In this approach, each array element is obtained by connecting two patches working at different frequencies directly. To form arrays with higher gain, two kinds of feed networks are described, which can be applied in systems where narrowband and wideband are needed, respectively. One is using the conventional feed network and the other is using the sequential rotation technique to further improve the CP axial ratio (AR) performance. Two prototype arrays with $4 \times 4$ elements are fabricated and tested in $X/Ku$ bands. Experimental results show that good CP characteristics are obtained, which agree well with the simulation results. For the first narrow-band prototype array, the 3-dB AR bandwidth is around 1.5% for both bands. For the second array using the sequential rotation technique, the bandwidth of return loss and AR are wider. In the lower band centered at 12.1 GHz, the ${-}10\hbox{-}\text{dB}$ return loss bandwidth is 8.3% and the 3-dB AR bandwidth is 14.2% [right-hand CP (RHCP)]; in the higher band centered at 17.4 GHz, the corresponding data are 18.9% and 14.9% [left-hand CP (LHCP)], respectively.

A novel substrate integrated waveguide (SIW) filtering crossover is presented based on the orthogonal degenerate TE201 and TE102 modes in SIW square cavities. By arranging the feeding ports and coupling windows at the cavity center, excellent transmission and isolation responses can be achieved successfully. In addition, the bandwidth of the crossover can be easily controlled using the well-established coupling matrix synthesis method, and the maximum bandwidth is determined by the acceptable isolation levels. A prototype operating at 20 GHz was designed and fabricated to verify this concept, and the measured results are in excellent agreement with the simulation results.

A wideband wide-coverage H-plane horn array with vertical polarization is proposed. Due to its light weight and low profile, the designed array is suitable for applications in spectrum monitoring systems on moving platforms. The switched-beam symmetrical array consists of four identical short H-plane horns. Pattern deterioration occurring in a high-frequency range is solved by inserting two pins in each horn. The measured impedance bandwidth is almost 100% for $\hbox{VSWR} owing to its fed structure with a thick-cylinder-loaded probe. The measured azimuth-plane beamwidth is about 90 $^{\circ}$ over the entire frequency range from 860 to 2500 MHz. Moreover, the measured results with the corresponding simulated results are presented and discussed in this paper.

Distributed compressive sensing (DCS) has been used in multiple-input multiple-output (MIMO) radar system. This application has led to substantial improvements over existing methods in MIMO radar. But there are also some challenges that should be resolved in order to benefit the most from DCS-based MIMO radar, such as radar signal with low signal to noise ratio and optimizing measurement matrix design. In distributed DCS-based MIMO radar context, this paper presents a cognitive mechanism for optimizing transmit and receive gain by applying the optimization guideline which based on the coherence of the sensing matrix (CSM) and signal-to-noise ratio. This paper proposed two kinds of method: the first one is to optimize transmit gain with the aim to maximize SNR, and the second one is to minimize CSM by adjusting receive gain. Simulations show that the proposed methods obtain significant better recovery performance than traditional DCS-based MIMO radar systems.

This article presents two novel resonators, that is, frequency selecting coupling structure loaded stepped-impedance resonator FSCSLSIR and π-section loaded FSCSLSIR. The resonator behaviors and guidelines are given to design FSCSLSIR dual-band bandpass filter BPF and π-section loaded FSCSLSIR triband BPF. The proposed dual- and triband BPF have very compact sizes of 0.13 λgd × 0.06 λgd and 0.115 λgt × 0.074 λgt, respectively. Moreover, good return loss, low insertion loss, and high band-to-band isolation can be observed, and the proposed FSCSLSIR dual-band BPF has an ultrawide stopband from 5.79 to 36 GHz. The experimental results are in good agreement with the simulations. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:427-435, 2015.

A new correction method is proposed for the single RF channel digital beamforming (DBF) antenna array. In this array, each array element is followed by a $0/\pi$ phase shifter, and the element outputs can be recovered by the single channel through the time sequence phase weighting (TSPW) technique. The outputs can be used to form desired beams through DBF. The performance of the DBF is influenced by the imperfection of the phase shifters. To obtain the errors in each phase shifter, the online test method based on a single known plane wave is introduced. The online test results are used to correct the element outputs using the relationship between the actual and the incorrect outputs. Compared with another previously proposed correction method, the new method is simpler and more suitable for real time correction. The factors that may influence the capability of the correction are analyzed. To validate the proposed method, an eight-element prototype is measured, and the data are used to synthesize low sidelobe patterns. Results show that the sidelobe level and gain improvements after correction are 11.1 and 2.6 dB, respectively.

A wideband microstrip series-fed magnetic dipole array antenna is proposed. The five-element dipole array antenna is designed to achieve both wide bandwidth and high gain because of its microstrip series feeding structure. The low-profile low-cost array is suitable for applications such as wideband high-gain wireless communications. Measured and simulated results are in good agreement. The measured impedance bandwidth of the array is enhanced up to 28.6% (5.0–6.7 GHz). The radiation patterns show its advantages of high gain (about 10 dBi), endfire radiation and vertical polarisation.

Low SNR condition has been a big challenge in the face of distributed compressive sensing MIMO radar (DCS-MIMO radar) and noise in measurements would decrease performance of radar system. In this paper, we first devise the scheme of DCS-MIMO radar including the joint sparse basis and the joint measurement matrix. Joint orthogonal matching pursuit (JOMP) algorithm is proposed to recover sparse targets scene. We then derive a recovery stability guarantee by employing the average coherence of the sensing matrix, further reducing the least amount of measurements which are necessary for stable recovery of the sparse scene in the presence of noise. Numerical results show that this scheme of DCS-MIMO radar could estimate targets’ parameters accurately and demonstrate that the proposed stability guarantee could further reduce the amount of data to be transferred and processed. We also show the phase transitions diagram of the DCS-MIMO radar system in simulations, pointing out the problem to be further solved in our future work.

A new type of digital beamforming (DBF) multibeam antenna array is proposed. In this antenna array, the amplitude and phase distributions on the array aperture are recovered using a single radio frequency (RF) channel through time sequence phase weighting (TSPW). The distributions can then be used to produce multibeams by digital beamforming. A proof-of-concept prototype of an eight-element receiving array in JC-band has been fabricated and tested. The measured results confirm the validity and advantages of the proposed scheme.