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This article presents a 140-GHz frequency-modulated continuous-wave (FMCW) radar transceiver featuring transmit/receive (TX/RX) antenna sharing that address a TX/RX beam misalignment problem when large-aperture lenses/mirrors/reflectarrays are used for pencil beam forming. A full-duplexing technique based on circular polarization and geometrical symmetry is applied to mitigate the 3 dB + 3 dB insertion loss inherent to conventionally adopted directional couplers, while still maintaining high TX-to-RX isolation. In addition, a self-adaptive self-interference cancellation (SIC) is implemented to suppress extra leakage due to antenna mismatch from a desired frontside radiation scheme. The TX/RX antenna sharing enables the pairing with a large 3-D printed planar lens and boosts the measured effective isotropic radiated power (EIRP) to 25.2 dBm. The measured total radiated power and minimum single-sideband noise figure (SSB NF) including antenna and duplexer losses are 6.2 dBm and 20.2 dB, respectively. The measured total TX-RX isolation is 33.3 dB under 14-GHz wide FMCW chirps. Based on a 65-nm complimentary metal–oxide–semiconductor (CMOS) technology, the chip has a die area of 3.1 mm2 and consumes 405 mW of dc power. Among all reported sub-THz transceivers with TX/RX antenna sharing, this work demonstrates the highest total radiated power and is the only work that has >30 dB of TX-RX isolation while mitigating the inherent 6 dB coupler loss. [ABSTRACT FROM AUTHOR]

This article presents 3-D printed metal-only dual-band millimeter-wave circularly polarized (CP) reflectarrays (RAs). The RAs’ unit cell (UC) is made of an anisotropic metal brick mounted on a full metal ground. In-plane rotating the metal brick introduces geometric Pancharatnam–Berry (PB) phase shifting, and vertically adjusting the position of the UC provides propagation phase shifting. The geometric PB and propagation phase shifting offer two different degrees of freedom, enabling independent wavefront shaping of CP wave over dual-band. Specifically, the low-band CP beam shaping solely depends on the propagation phase. In contrast, the high-band CP beam shaping depends on the geometric PB and the propagation phases. The coupling issue between dual-band is minimal because of the unique dual-band phase-shifting methods. In addition, 3-D printed dual-band left-hand CP (LHCP) horn antennas are designed, printed, and used as the feed. To demonstrate, two RA antennas with different dual-band CP beam directions are fabricated and measured. [ABSTRACT FROM AUTHOR]

This communication proposes an additively manufactured metal-only millimeter-wave dual circularly polarized (CP) reflectarray with independent control of polarizations. A metal-only right-hand CP (RHCP) antenna is designed and used as the reflectarray’s phase-shifting unit cell (UC). The RHCP UC is immune to the LHCP incidence, and the UC directly reflects the LHCP incidence into free space. Thus, the phase shifting of the LHCP wave solely depends on the rotation angle of the UC. For the RHCP incidence, it is received by the RHCP UC first and induced into the metal waveguide. Then, the energy is reflected by the ground of the metal waveguide and reradiated into free space with RHCP. Thus, the phase shifting of the RHCP wave is determined by the rotation angle of the UC and the length of the metal waveguide. By properly selecting the rotation angle of the UC and the length of the metal waveguide, RHCP and LHCP can be independently manipulated. To demonstrate, two reflectarray antennas with different LHCP and RHCP beam directions are fabricated using additive manufacturing and experimentally verified. [ABSTRACT FROM AUTHOR]

Coarse-grained reconfigurable architecture (CGRA) is a promising programmable hardware with high power-efficiency and high performance. However, compiling and optimizing loops with irregular branches on CGRAs is a challenge to fulfill the performance potential. Existing predication techniques, such as partial predication (PP) and full predication (FP), conservatively implement software pipeline with a static initiation interval (II) obtained from the maximum graph, and thus only parts of the graph in each loop iteration will be actually executed, resulting in underexploited performance. To exploit more loop-level parallelism for irregular branches, this article proposes a novel dynamic-II pipeline (DIP) scheme, which realizes a pipeline with variable II by accommodating multiple iterations of short path in one static configuration. Since the DIP scheme is effective to only certain types of branches, this article designs a hybrid compilation framework integrating other complementary methods, which selects the appropriate method for source programs according to a proposed performance evaluation model. Experimental results show that: 1) the hybrid compilation framework can effectively extract branch features, correctly choose and implement corresponding branch processing methods within acceptable compile time and 2) as compared to PP and FP, DIP brings a significant total execution time (TET) reduction by 27.21% and 22.04% on average when the execution probability of a short branch is 50%. [ABSTRACT FROM AUTHOR]

This communication presents a dual-band aperture-shared high gain antenna for millimeter-wave (mm-wave) multi-beam and sub-6 GHz applications by integrating transmitarray into Fresnel zone plate (FZP) lens. The transmistarray consists of two sets of unit cells (UCs), which can provide high transmission magnitude and [ $-\pi $ , $\pi $ ] phase tuning at the mm-wave frequency band. Meanwhile, they show distinct transmission features at the sub-6 GHz band (one set of UC allows the electromagnetic (EM) wave to pass while the other prohibits the EM wave from passing). Then, by properly arranging the two kinds of UCs into the transparent and opaque region of the FZP lens respectively, the sub-6 GHz FZP lens and the mm-waveband transmitarray are integrated into the same aperture seamlessly. A waveguide-integrated patch antenna is adopted as the feed. The patch antenna operates at the sub-6 GHz band and three open waveguide antennas are used for the mm-wave multi-beam radiation. The proposed antenna achieves high gain at both bands with a reused radiating aperture. Mm-wave multi-beam radiation is obtained without an extra feeding network. For demonstration purposes, the central frequencies of the sub-6 GHz and the mm-wave bands are selected at 6 and 27 GHz, respectively. An antenna prototype is fabricated and experimentally verified. [ABSTRACT FROM AUTHOR]

This letter presents a dual-band antenna with a large frequency ratio of 11.7 (2.4 GHz/28 GHz) by integrating an mm-wave Fabry–Perot cavity (FPC) antenna into a sub-6 GHz patch antenna. The patch with periodic slots functions as both the 2.4 GHz radiator and the partially reflective surface (PRS) of the 28 GHz FPC antenna. By properly tuning the length of the periodic slot, the PRS's reflection can be easily adjusted. As the periodic slot's length and width operating at 28 GHz are much smaller than the wavelength at 2.4 GHz, periodic slot operating at 28 GHz have little impact on the radiation of the patch. Furthermore, because of the Fabry–Perot resonance, the antenna can have a peak gain reaching 15 dBi at 28 GHz band with an easy feeding structure. For demonstration, a prototype is fabricated and experimentally verified. Note that the frequency ratio is not limited to the proposed design (11.7 for demonstration). It can be easily adjusted based on the same principle. [ABSTRACT FROM AUTHOR]

This communication proposes a dual-band antenna hybridizing a folded reflectarray antenna (FRA) and a folded transmitarray antenna (FTA). First, a polarization-rotation transmitarray is designed based on a new Fabry–Perot (FP)-liked phasing element. Unlike its counterparts, this new FP-liked phasing element twists the polarization of electromagnetic (EM) waves and provides sufficient phase tuning range only in the operating band of FTA. In the meantime, in the band of FRA, the transmitarray acts as the polarizing grid, which reflects one polarization while allowing the orthogonally polarized one to pass without affecting its polarization and phase. Second, a polarization-rotation-ground-integrated (PRGI) reflectarray is designed. The reflectarray collimates the EM wave in the band of FRA and twists its polarization by 90°, forming the folded reflectarray. Meanwhile, it also twists the polarization of the EM wave in the band of FTA. By hybridizing the FTA and FRA sharing the same aperture, the proposed design achieves dual-band high-gain radiation. To the best of our knowledge, this is the first time that the FRA and FTA are combined to form a shared aperture antenna, which inherits the advantages of both FRA and FTA, such as high gain, low profile, and reduced blockage effect of the feed. An antenna prototype is fabricated and measured to verify the idea. [ABSTRACT FROM AUTHOR]

This article presents an aperture-shared dual-band large frequency-ratio high gain antenna for sub-6 GHz and millimeter-wave (mm-wave) bands applications. Initially, the partially reflective surface (PRS) of the Fabry–Pérot cavity (FPC) antenna operating at the sub-6 GHz band is realized by using single-layered periodic grid patches while the opaque region of the mm-wave bandwaveband Fresnel zone plate (FZP) lens antenna is implemented by using periodic double-screen dipoles. Then, the PRS and the FZP lens are hybridized together and upgraded into a kind of composite metasurface, which simultaneously functions as the PRS of the sub-6 GHz FPC antenna and the mm-wave bandwaveband FZP lens with little dual-band mutual interference. Thus, the FPC antenna and the FZP lens can share the same aperture with high aperture reuse efficiency. Because the principles are based on the FPC resonance and the collimating FZP lens, high gains are achieved at both bands without a feeding network. Meanwhile, a dual-band large frequency-ratio antenna is designed as the feed. A prototype working at 3 and 28 GHz bands is designed, fabricated, and measured to verify the idea. [ABSTRACT FROM AUTHOR]

This communication proposes a new all-dielectric broadband dual-band reflectarray with a large frequency ratio using low-cost 3-D printing. In contrast to conventional reflectarrays using metallic resonant cells or dielectric slabs as phasing elements with full metal ground, the proposed design uses air as the phasing element and a stepped dielectric mirror structure as the ground. In this way, the metal ground is removed, which makes the design an all-dielectric one. Taking advantage of the dielectric mirror that only exhibits a bandgap in the predesigned band while allowing electromagnetic (EM) waves to pass through it at the frequency out of the bandgap region, a dual-band reflectarray is obtained. By properly selecting the bandgap frequency of the dielectric mirror, the dual-band frequency ratio is scalable and can be very large. Furthermore, instead of using a metallic or dielectric resonator based on resonance, air layers with linear phase response are adopted as the phasing element. Thus, the reflectarray shows broadband and stable performance over the dual-band. Compared with the state-of-the-art works using printed circuit boards (PCBs) or microfabrication, the proposed design is low cost and lightweight, and can be rapidly prototyped. For proof-of-concept, a prototype operating at $K$ -band and $V$ -band with a frequency ratio of 2.7 is printed and measured. [ABSTRACT FROM AUTHOR]

Fresnel zone plate (FZP) lens antenna, consisting of a set of alternative transparent and opaque concentric rings arranged on curvilinear or flat surfaces, have been widely used in various fields for sensing and communications. Nevertheless, the state-of-art FZP lens antennas are limited to a single band due to the frequency-dependent feature, which hinders their use in multi-band applications. In this work, a shared aperture dual-band FZP metalens antenna is proposed by merging two single-band FZP metalens antenna operating at distinct frequency bands seamlessly into one. Instead of using conventional metallic conductors, double-screen metagrids are devised in this work to form the concentric rings. Because the metagrids show distinct transmission/reflection properties at different frequencies, the performance of one set of concentric rings operating at the one band will not be affected by the other operating at the different band. In addition, to compensate for the phase shift introduced by the metagrids, an additional dielectric ring layer is added atop the FZP taking advantage of additive manufacturing. Thus, the radiation performance of the dual-band FZP lens antenna is comparable to that of each single FZP metalens antenna. For proof-of-concept, an antenna prototype operating at the dual band, 75 and 120 GHz with a frequency ratio of 1.6, is fabricated using an integrated additively manufactured electronics (AME) technique. The measured peak gains of 20.3 and 21.9 dBi are achieved at 75 and 120 GHz, respectively. [ABSTRACT FROM AUTHOR]

Nowadays, hardware security has become a serious concern for modern CPUs. State-of-the-art detection approaches rely heavily on trustworthy and intimate internal states, incurring significant design/operation overheads and additional risks to security and intellectual property. This article proposes an architecture called Jintide, which utilizes trusted external monitors to validate an untrusted CPU chip at runtime. This architecture records, replays, and analyzes the CPU’s IO and memory behavior with the architectural states. The Jintide simultaneously verifies whether the records are correctly replayed with the instruction set architecture and whether the records involve malicious behavior. Consequently, not only architectural but also micro-architectural threats can be detected. The Jintide adopts the states from the untrusted source because it has a built-in function to detect spurious states. The monitors comprise three types of chips (with 28-/40-nm TSMC technology): a tracer chip to record the behavior of IO ports, multiple tracer chips to record the behavior of DDR4 DIMMs, and a reconfigurable chip to verify these records with software states. As runtime external monitors, the Jintide would be especially suitable to constitute distributed large-scale clusters, which can amortize operation overheads. This scheme is effective in detecting pervasive hardware security issues, including vulnerabilities, backdoors, and hardware Trojans. The measured results show that a system composed of 300 000 Jintide CPUs containing Intel Xeon Skylake processors can detect over 99.8% of recognizable attacks at the cost of 0.98% performance loss. Hence, the Jintide is an extensible, low-cost, and effective solution to improve the hardware security of large-scale CPU clusters. [ABSTRACT FROM AUTHOR]

In order to reduce the burden of medical PSG testing, we proposed a system or a way for preliminary screening of OSA and rehabilitation self-examinations for patients with moderate or severe OSA in family units. The snoring vibrations of 28 sets of data were collected by this system. And then, performing segmentation processing of the acquired signals in the time domain to obtain the snore silence segments, and two preliminary screening methods of OSA were proposed based on the silence segments, which were the SSI-Diagnostic Method and $\xi $ -Diagnostic Method. All data were divided into 4 groups, based on PSG Apnea Hypopnea Index (AHI): No OSA, (n = 5;AHI< 5), mild (n=6; 5 ≤ AHI< 15), moderate (n=4; 15 ≤ AHI< 30) or severe OSA (n=13; AHI>30 events/h). The thresholds of the $\xi $ -diagnostic method were obtained from the $\xi $ -ROC scatter plots, 0.0236, 0.0666, and 0.2134 for simple/mild, mild/moderate, and moderate/severe OSA, respectively. Bland–Altman graphical analysis showed the strong agreement between SSIs and AHIs (r = 0.96, p < 0.001). Additionally, results showed that, except for NPV, all indicators are greater than 90%, the $\xi $ -diagnostic method had a more balanced, real and excellent preliminary screening performance than the SSI-diagnostic method among the diagnostic indicators involved. The preliminary screening performance of proposed screening system with particularly significant practical significance could meet the screening requirements of potential OSA patients and self-examinations of rehabilitation training for much heavier OSA patients in family units to reduce the burden of screening and PSG testing of patients. [ABSTRACT FROM AUTHOR]

This article proposes a novel wideband single-layer coplanar waveguide (CPW)-fed antenna element and multiple-input, multiple-output (MIMO) antenna based on a multimode resonator. Equivalent circuits of the multimode resonator are analyzed by adopting the odd- and even-mode analysis approach. To prove the effectiveness of the equivalent circuit, scattering (S)-parameters of the equivalent circuit are simulated in Advanced Design System (ADS). Additionally, transmission coefficients are studied under the weakly coupling condition. The first and second resonant points are introduced by even and odd modes, respectively, whereas the third resonance is caused by the embedded stepped impedance resonator (ESIR). The CPW-fed antenna element is designed based on the proposed resonator. CPW fed not only excites the multimode resonator but also generates an extra resonance between the odd mode and ESIR resonant frequencies. Furthermore, the odd-mode resonance creates the lower cutoff frequency, and the resonance caused by ESIR forms the higher cutoff frequency. Hence, a filteringlike operating frequency band is achieved without introducing an extra filtering circuit. The filtering characteristic is favorable for the system to realize high sensitivity and reduce outof-band interferences simultaneously. [ABSTRACT FROM AUTHOR]

This article presents a new linear-to-circular polarization conversion coding unit, on which two new kinds of beam-shaping lenses are proposed. First, under periodic boundary conditions, a linear-to-circular polarization conversion coding unit is introduced, which introduces the necessary phase delay by adjusting its geometrical parameters. The phase delay ranges from 0° to 360° and is discretized into 3 bit coding units corresponding to specific delays. Second, by properly arranging the coding units, a high-gain circularly polarized (CP) lens is proposed. The lens achieves linear-to-circular polarization conversion and beam collimation in the transmission mode simultaneously with a planar configuration, which is different from counterparts that place a lens atop of a polarizer. Furthermore, the coding units are used to form Wollaston-prism-like and Rochon-prism-like planar CP beam-shaping lenses, which split the beams with different polarizations into right- and left-handed components. These beams can be controlled independently. Prototypes working at 30 GHz band are designed, fabricated, and measured to verify the idea. [ABSTRACT FROM AUTHOR]

Orbital angular momentum (OAM) generation based on metasurfaces has attracted tremendous interest due to its potential in capacity enhancement of high-speed wireless communication systems. Reconfigurability is one of the key desired characteristics for the design of future metasurfaces. In this paper, a metasurface taking advantage of vanadium dioxide (VO2) is proposed. The proposed design can generate a non-diffractive OAM beam and achieve the multiple reconfigurability of the topological charge, beam radius, beam deflection angle. The operation frequency can be adjusted by controlling the state of VO2 at terahertz (THz) region. Simulation results demonstrate that the designed metasurface can generate a non-diffractive OAM beam with tunable topological charge and beam radius, propagating along ±x or ±y directions with the controllable deflection angle between 6.74° and 44.77°, ranging from 0.69 THz to 0.79 THz. [ABSTRACT FROM AUTHOR]

This communication presents a low-profile wideband and high-gain patch antenna array using low-temperature cofired ceramics (LTCCs) fabrication technique for 60 GHz applications. A coupled feeding scheme is adopted so that the antenna achieves wide impedance bandwidth that covers the entire 60 GHz license-free band with a height of only 0.384 mm (four tape layers). The shorting via connecting the upper patch and ground achieves the function of a virtual ac ground plane of differential feeding. This enables the antenna element to achieve good radiation performances, including stable gain (variation less than 1 dB) and a symmetrical beam with low cross-polarization over the entire frequency band. The performances of the antenna element are comparable to that of the differential-driven patch antenna while the complex differential feeding network is not required. Furthermore, the proposed antenna element with simple and easy-to-integrate geometry is successfully extended to a $4 \times 4$ antenna array using a substrate integrated waveguide (SIW)-based feeding network. The measured results show that the impedance bandwidth of the array covers the 60 GHz license-free band. The maximum gain can reach 16.7 dBi and the radiation performances are very stable over the operating frequency band. [ABSTRACT FROM AUTHOR]

This paper presents a new dual-band dual circularly polarized (CP) high gain patch antenna array for vehicle satellite communications. The array consists of 16 linearly polarized dual-band elements backed with a new frequency-selective-surface (FSS)-integrated polarization rotation ground. The polarization rotation ground is located underneath the array, which not only acts as a reflector to increase the array boresight gain but also enables the array's dual CP radiation. The electromagnetic (EM) waves reflected by the ground retard either 90° or 270° with respect to the EM waves of the array directly radiated to the upper sphere at two frequency bands, leading to the dual-band dual CP radiation. This is totally different from many of the former counterparts which are based on either the perturbation on the stacked patch or external feeding network. Measured results show the −10-dB impedance bandwidth is from 7.8 to more than 8.5-GHz for X-band and from 14 to 15.3-GHz for Ku-band. The 3-dB axial ratio bandwidth is from 8.15 to 8.35-GHz for the lower band (right-hand CP) and from 14.2 to 14.8-GHz for the higher band (left-hand CP), respectively. [ABSTRACT FROM AUTHOR]

This paper presents new single-ended-fed planar aperture antennas (SPAAs) using low-temperature co-fired ceramics (LTCC) process technology. The SPAA element is proposed first, which not only inherits the merits of the aperture antennas including high gain and wide bandwidth but also exhibits advantages of low profile and compact size. The aperture is excited by a cross-shaped patch, and a loop-shaped balun structure placed below the patch is introduced to convert the single-ended signal into differential one to drive the patch. In this way, the energy can propagate on the patch in a traveling waveform and illuminate the aperture with uniform E-field distributions. Therefore, the antenna achieves good electrical and radiation performances, which are comparable to its balanced-fed counterparts, while processing a simplified structure. Measured results demonstrate that the impedance bandwidth of the antenna covers the 60 GHz license-free band (57–64 GHz), and the maximum gain can reach 11.5 dBi with a cavity area of only about 27 mm2. Furthermore, the element is successfully extended to a $4\,\,\times \,\,4$ element array using a substrate-integrated-waveguide based feeding network to further increase the gain up to 20.4 dBi. The measured results show that the impedance bandwidth of the array is from 57.5 to 65.7 GHz and the radiation performances are very stable over the operating frequency band. [ABSTRACT FROM AUTHOR]

This communication presents a new design of a quadri-polarization-agile aperture-coupled patch antenna array for 60 GHz applications. Four polarization states, namely, vertical linear polarization, horizontal linear polarization, left-hand circular polarization (LHCP), and right-hand circular polarization (RHCP) can be flexibly reconfigured by dynamically switching the excitation of the corresponding port. More importantly, as the LP and CP radiations are achieved by using differential feeding and sequential-rotation feeding, respectively, the array exhibits wide impedance and axial ratio (AR) bandwidths, high polarization purity as well as symmetrical pattern with the main beam fixed at boresight. The −10 dB impedance bandwidths are better than 11.6% (57–64 GHz) for the four polarization states. The measured AR bandwidths are from 58 to more than 64 GHz for both the LHCP and RHCP. The good radiation performance together with the quadri-polarization-agile capability of this new array, as demonstrated in the communication, underlines its suitability for the future 5G communication systems, especially in a multipath propagation environment. [ABSTRACT FROM AUTHOR]

This communication presents a new kind of substrate-integrated waveguide (SIW) slot antenna array with 1-D and 2-D monopulse radiation patterns. First, a new SIW magic-tee is developed, which exhibits a wide phase/amplitude balance bandwidth. Then, the magic-tee is extended to a new comparator which is used to feed the antenna with 2-D monopulse radiation pattern. Based on the proposed magic-tee and the comparator, 1-D and 2-D monopulse slot antenna arrays with $4\times 4$ elements are designed and measured, respectively. The experimental results show that the arrays exhibit good monopulse performance. More importantly, compared with their former counterparts, the monopulse performance of the arrays exhibits merely slight degradation over a much wider bandwidth due to the wide phase/ amplitude balance bandwidth that the comparators achieved. [ABSTRACT FROM AUTHOR]

This letter presents a new wideband high-gain circularly polarized (CP) substrate integrated cavity excited antenna array for the 60 GHz applications. First, a 2 × 2-element CP array is proposed with an aperture-coupled two-arm spiral antenna as its radiating element, which can exhibit good CP radiation performance. Instead of the conventional lossy and complicated feed network, a simple but efficient excitation structure based on higher-order-mode (TE340) cavity resonance is used to feed the array. The higher-order-mode cavity feeds all of the radiating elements in the same phase and magnitude, and the resonant mode is excited by a single slot aperture. Then, the proposed 2 × 2-element CP array is used as subarray to implement a sequential-rotationally fed 4 × 4-element CP array. Measured results show that the array has a wide axial-ratio bandwidth of more than 18.8% (53–64 GHz) with a peak gain reaching 20 dBic occurring at 61 GHz. The radiation patterns of the array are generally symmetrical with its main beam fixed at boresight. [ABSTRACT FROM AUTHOR]

A wideband highly isolated multiple-input–multiple-output patch antenna with an artificial magnetic conductor (AMC) ground plane is proposed in this letter. The antenna, which is rotationally symmetrical, is constructed by V-shaped patches coupled by a bowtie dipole. The bowtie dipole and the V-shaped parasitic patches produce two resonant modes that are coupled together. Therefore, a wide impedance bandwidth is obtained. Thanks to the orthogonal feeding and the rotationally symmetrical geometry, the antenna exhibits high port isolation as well as symmetrical radiation patterns with a compact size of 40 × 40 × 1.524 mm3. By placing an AMC ground plane with a distance of 10.5 mm below the radiating element, the antenna can achieve a unidirectional high gain with a lower height of the profile compared to that with perfect electrical conductor ground. Measured results show the antenna has an impedance bandwidth of 31.0% (3.0–4.1 GHz) with port isolation better than 25 dB. The peak gain can reach 7.1 dBi with stable and symmetrical radiation patterns. [ABSTRACT FROM AUTHOR]