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Two-degree-of-freedom control of field distribution on the pseudotraveling wave resonator using nonreciprocal metamaterial lines is demonstrated for the first time. Dynamic control of current distribution on the resonator is given based on circuit theory. We employed a normally magnetized ferrite microstrip line-based composite right-/left-handed (CRLH) transmission line as a metamaterial with variable phase-shifting nonreciprocity. Numerical simulation results show that the phase gradient of the fields along the resonator is controlled by the applied dc magnetic field to the ferrite. By changing the reflection coefficients of two reflectors inserted at both ends of the CRLH line section, current distribution along series and shunt branches of the unit cell is continuously and drastically changed under the resonance. The variable field distribution was implemented to polarization-plane-rotation and beam-scanning leaky-wave antennas. The experimental demonstration verifies our basic concept and shows the performance of the prototype antenna with a beam scanning angle of 20° and a continuous rotation angle of polarization plane by ±70° at the fixed frequency.

This article presents a novel miniaturized circularly polarized (CP) antenna based on periodically structured surfaces inspired by the vertical split-ring resonator (VSRR). The VSRR is considered as a magnetic dipole placed above the ground, which could excite strong boresight radiation with a reduced size. To enhance the aperture gain, multicapacitors and inductors (Multi-C&L) are loaded on the loop, which replace the single capacitive gap of the conventional split-ring resonator (SRR). Here an SRR-inspired periodic structure with a relatively uniform field distribution is achieved. The stepped impedance resonator (SIR) structure, as the unit cell of the SRR-inspired surface, is analyzed and investigated using the circuit models derived from the SRR. By cascading multiple high-value capacitors, a larger aperture with a uniform field distribution is obtained. Linearly polarized (LP) and CP antennas are studied. The proposed CP antenna is made of thin substrates and metallic screws, resulting in a negligible dielectric loss. It offers attractive features including a compact size, a low profile ( $0.191\lambda _{0} \times 0.191\lambda _{0} \times 0.032\lambda _{0}$ ), good radiation efficiency, novel working principle, flexible performance control, and a bandwidth well covering the 902–928 MHz UHF band, which is well situated for radio frequency identification (RFID) application.

Analog photonic solutions offer unique opportunities to address complex computational tasks with unprecedented performance in terms of energy dissipation and speeds, overcoming current limitations of modern computing architectures based on electron flows and digital approaches. The lack of modularization and lumped element reconfigurability in photonics has prevented the transition to an all-optical analog computing platform. Here, we explore, using numerical simulation, a nanophotonic platform based on epsilon-near-zero materials capable of solving in the analog domain partial differential equations (PDE). Wavelength stretching in zero-index media enables highly nonlocal interactions within the board based on the conduction of electric displacement, which can be monitored to extract the solution of a broad class of PDE problems. By exploiting the experimentally achieved control of deposition technique through process parameters, used in our simulations, we demonstrate the possibility of implementing the proposed nano-optic processor using CMOS-compatible indium-tin-oxide, whose optical properties can be tuned by carrier injection to obtain programmability at high speeds and low energy requirements. Our nano-optical analog processor can be integrated at chip-scale, processing arbitrary inputs at the speed of light. All-optical platforms hold potential for fast and efficient analog computing, but are limited by their size and poor reconfigurability. Here, a zero-index nanophotonic platform enables post-Moore’s law analog optical computing, processing data with high throughput and low-energy levels.

Miniaturised circularly polarised (CP) antennas based on dispersion‐engineered metamaterial transmission lines (TLs) are proposed and developed for RFID applications. It is first studied and developed based on the equivalent circuit and dispersion curves of composite right/left‐handed TL (CRLH‐TL), which is featured by a novel/low‐cost double‐layered 3D structure, including metallic screws, one ground layer and metal‐insulator‐metal (MIM) capacitor loaded on the top layer. CP radiation is achieved by two crossed CRLH‐TLs with a microstrip‐slot coupling excitation. One CP antenna and one polarisation reconfigurable antenna, which utilise CRLH‐TLs are then implemented, respectively. Compared with the conventional right‐handed (RH) TL‐based antennas (positive resonance‐based antennas), miniaturisation is achieved by pushing down the dispersion curve to a lower frequency using larger LH capacitance or/and inductance. Negative‐order resonances could be successfully excited by cascading π‐type unit‐cells. It shows similar radiation characteristics and additional size reduction as the positive resonance‐based antennas. This antenna shows an electrical size of 0.24 λ0 × 0.24 λ0 × 0.03 λ0, a −10 dB bandwidth of 4.8%, and a peak gain of 4.2 dBic. It demonstrates advantages in terms of flexible size reduction, low cost, easy manufacturing, and good radiation performance, which are very suitable for 902–928 MHz UHF band RFID application.

This article presents a detailed study on an interesting compact wideband CP antenna using a novel split-ring resonator (SRR) and composite right-/left-handed transmission lines (CRLH-TLs). A novel vertical SRR made by the metallic sheets and PCB substrate is proposed, which achieves substantial size reduction. To obtain wideband CP radiation, a novel 3 dB branch-line coupler using dispersion engineered CRLH-TL is employed as the feeding circuit. The vertical SRR and CRLH-TL-based feeding network are analyzed by their own equivalent circuit models. A single-fed CP antenna and a dual-CP (LHCP/RHCP) antenna with a compact size of $0.277\,\,\lambda _{0} \times 0.277\,\,\lambda _{0} \times 0.033\,\,\lambda _{0}$ at 3.30 GHz are implemented, respectively. For the dual-CP antenna, both the measured −10 dB $\vert S_{11}\vert $ bandwidth and 3 dB axial ratio (AR) bandwidth cover the 5G N78 band (3.30–3.80 GHz, 14.1%) quite well. In addition, the measured peak gain and radiation efficiency are greater than 5.4 dBic and 77% (−1.1 dB), respectively. It shows attractive features including a miniaturized size, low-cost, wide bandwidth, and good CP performance, appearing as good candidates for fifth-generation new radio (5GNR) communication systems.

In this article, we propose nonperiodic metasurfaces used for retroreflection of oblique incident wave with linear polarization (TE/TM) and circular polarization (CP). For CP wave, both handedness reversal and handedness preservation cases are demonstrated. The proposed metasurfaces consist of nonperiodic group cells optimized by genetic algorithm for desired scattered power patterns. Each group cell includes several locally periodic elements that are characterized by their reflection phase response under TE/TM or CP illumination. The proposed metasurfaces for retroflection have achieved reduced sidelobe level and suppressed specular beam and are verified by both full wave simulation and measurement at 10 GHz. This nonperiodic metasurface design method offers fast implementation for retroreflection of any plane wave with easy planar fabrication and can be easily scaled to millimeter-wave, THz, and optical regimes.

In this article, 150-GHz CMOS transmitter (TX) and receiver (RX) are presented for contactless and plastic waveguide communications. The implemented system employs a four-level pulse-amplitude modulation (PAM-4) and noncoherent detection. The direct upconversion TX and self-mixing RX suffer amplitude nonlinearity and distort the carrier-modulated multilevel signals. A current-mode digital predistortion is integrated in the PAM-4 modulator to correct the nonlinearity for the carrier-modulated multilevel signaling. Coupling antennas are designed on FR4-HR substrates. The same antenna launches electromagnetic energy into plastic waveguides to extend the communication distance. A plastic printed circuit board (PCB) is introduced by inserting plastic waveguides into copper-coated slots on PCBs to realize terahertz PCB communications. The TX and RX are fabricated in the 28-nm standard bulk CMOS process. The system consumes 60.2 mW under 1.2/1.5 V supply while transferring 30 Gb/s PAM-4 data, achieving 2.01 pJ/bit energy efficiency.

A novel wideband (11.1% −10 dB bandwidth) and low-profile (0.03 λ 0 height) metamaterial transmission line (TL)-inspired circularly polarized (CP) antenna for radio-frequency identification (RFID) application is proposed. A capacitor-loaded TL (CL-TL) is realized by inserting multiple series metal–insulator–metal (MIM) capacitors into the TL. The MIM capacitor works as a series left-handed (LH) capacitor as well as a radiator. First, the CL-TL is studied and analyzed through circuit model and dispersion curves. Then, a linearly polarized (LP) antenna and a CP antenna based on the CL-TLs are implemented. Compared with the conventional right-handed (RH) TL-based antennas, here the size reduction is achieved by pushing down the dispersion curve to lower frequency using multistage structures and larger LH capacitance. The measured −10 dB impedance bandwidth, 3 dB axial-ratio (AR) bandwidth, and radiation efficiency for this CP antenna is 859–959 MHz (11.1%), 902–923 MHz (2.3%) and 83.9%, respectively. It features a compact size, low cost, wide bandwidth, and good radiation performance, which could be conveniently used for RFID reader.

This article presents a novel ultraminiature circularly polarized (CP) antenna inspired by crossed split-ring resonators (SRRs), and its derivative forms with frequency and polarization re-configurability for radio frequency identification (RFID) applications. A novel resonator structure with two metal–insulator–metal (MIM) capacitors that is inspired by vertical SRR (VSRR) is first proposed, which could be easily miniaturized while achieving a reasonable high radiation gain. Two crossed dual-capacitance ring resonators (C-DRRs), which can be equivalent to two crossed magnetic dipoles, are then arranged perpendicularly and excited simultaneously with an SMA connector. Only an aluminum ground sheet, metallic screws, and a thin low-cost dielectric PCB board are used, where the dielectric loss is substantially minimized. This SRR-inspired CP antenna, as well as its frequency and polarization reconfigurable derivative by introducing a mechanically tunable inductor or using electrically controllable components, are analyzed and experimentally demonstrated, respectively. The developed antenna achieves an electrically small size of 0.135 $\lambda _{0}\,\,\times $ 0.135 $\lambda _{0}\,\,\times $ 0.045 $\lambda _{0}$ , and its size is considerably smaller than other reported compact RFID reader antennas. The measured −10 dB bandwidth, peak gain, and radiation efficiency are 3.1% (900–928 MHz), 5.51 dBic, and 86.5%, respectively, which agree perfectly with the simulation. They demonstrate superior advantages in terms of ultracompact size, low-cost, wide axial ratio (AR) beam-width, high efficiency, and easy fabrication/assembling for RFID-related applications.

The equivalent circuit approach (ECA) is used in this work to analyze and design a previously proposed one-dimensional planar blazed grating of the resonant type. The analysis covers both the classical Littrow configuration, when the direction of the relevant diffracted order coincides with that of the incident wave (Bragg blazing), and when these directions are different (off-Bragg blazing). Once the scattering problem of the grating structure is posed as a discontinuity problem inside an equivalent generalized waveguide (corresponding to the unit cell of the original structure) and studied in terms of its equivalent circuit network, the possibility of transferring all the power of the incident plane wave into one single-diffraction order is seen as a simple impedance matching problem. An associated resonance phenomenon is also found to be implicitly associated with this matching condition. This simplifying and fruitful standpoint makes it possible to set up a systematic design procedure to find the specifications of the planar grating for either Bragg or non-Bragg blazing operation. Dielectric and strong skin-effect ohmic losses are easily implemented in the ECA and its effects in the practical design of structures are discussed. Ministerio de Ciencia, Investigación y Universidades TEC2017-84724-P Junta de Andalucía TIC-112

This paper presents a millimeter-wave (127 GHz) CMOS transceiver with a digital pre-distortion capable PAM-4 modulator for contactless communications. The transmitter upconverts PAM-4 modulated baseband signals through a free-running 127-GHz oscillator and single-balanced mixer, and it delivers PAM-4 modulated carrier signals to a folded-dipole antenna, which is designed on a FR408HR substrate. The receiver’s low-noise amplifier provides a 10-dB gain, and the self-mixer downconverts carrier-modulated PAM-4 signals to baseband signals without the necessity of carrier synchronization. The PAM-4 modulator pre-distorts the baseband signals and corrects the non-linear characteristics of the transmitter’s upconversion mixer and the receiver’s downconversion self-mixer. Designed and fabricated in a 65-nm CMOS process, the demonstrated system transfers 20 Gb/s of PAM-4 modulated data through a 1-mm air gap and consumes 79.5 mW (transmitter: 50.8 mW and receiver: 28.7 mW) of power under a 1.2-V supply, achieving a 3.98-pJ/bit energy efficiency. The communication distance is extended to 3 cm by inserting a dielectric waveguide between the same transceiver.

In this paper, the enhancement of bandwidth for beam squint reduction in leaky-wave antennas has been numerically and experimentally demonstrated based on the pseudo-traveling-wave resonance by using nonreciprocal composite right-/left-handed metamaterial lines with almost dispersion-free phase-shifting nonreciprocities. We consider two different types of metamaterials governed by the edge-guided mode propagation in normally magnetized ferrite microstrip lines and operating at frequencies far above or below the magnetic resonance. Both metamaterials are separately designed and implemented in leaky-wave antennas based on the pseudo-traveling-wave resonance. The numerical simulation and measurement results verify the beam squint reduction for both cases with the enhanced bandwidths of 6%–10%.

In this paper, we propose a 3-D chiral metamaterial comprising of a high-K dielectric cube and metallic mesh in the microwave region. Our numerical results show that the metamaterial has dispersionless optical activity and an impedance matching to free space, resulting in broad polarization rotation and low reflectance.

A two-endfire-element array with balanced feeding structure is proposed in this paper. The array contains two endfire coupled-mode patch antennas (CMPA) [1], which are fed by a T-shape parallel plate waveguide (PPWG) power divider. The PPWG feeding provides well-balanced input signal while maintaining low profile. It eliminates the undesired radiation of common-mode current, and thus addresses the major issue for the endfire CMPA. The performance of the single antenna fed by PPWG is analyzed and compared with the same antenna fed by microstrip line (MSL). The proposed array has measured bandwidth of 2.1% centered at 2.435 GHz. It offers 4.6 dBi peak gain at endfire and maximum front-to-back ratio of 23 dB. The proposed array radiates exact endfire patterns with vertical polarization while maintaining compact size and low profile.

In this paper, a polarization-plane-controllable beam-scanning leaky-wave antenna based on pseudo-traveling-wave resonance is proposed and demonstrated by using nonreciprocal metamaterials. The antenna is composed of a ferrite-microstrip-line-based nonreciprocal composite right/left-handed transmission-line resonator that is terminated with tunable reactive loads for reflectors and a feed line. By changing the externally applied dc magnetic field to the ferrite, beam scanning was achieved at the fixed frequency. In addition, plane of polarization can be rotated independently by changing the phase condition of the reflectors. The numerical and experimental results verified the basic concept.

In this paper, we propose stacked metasurfaces that can convert linearly polarized (LP) wave into circularly polarized (CP) wave. The metasurfaces consist of two layers of periodic subwavelength Jerusalem cross elements and one interlayer of periodic square rings. The anisotropic metasurface elements yield 90° phase difference for two orthogonal linear polarizations upon transmission. The aperture coupling interlayer can provide a flat and close to unity magnitude response to improve the axial ratio (AR). A prototype of this metasurface polarization converter is simulated, fabricated and measured in Ku band. Both simulation and measurement results demonstrate good AR in the operating frequency band. This linear-to-circular polarization converter design can also be used in quasi-optical applications.

The coupling between a pair of anti-symmetrically nonreciprocal composite right/left-handed metamaterial lines is investigated. It is found from the numerical simulation results that wideband nonreciprocal circulation characteristics are achieved among the four ports in the bandgap regions due to the coupling at Γ point in the dispersion diagram. Experimental results support the numerical simulation results on the nonreciprocal transmission characteristics.

Background: Neuropathic intestinal disorders continue to pose a significant burden, and current treatment options do not target the underlying cellular deficiencies. The goal of this study is to determine whether acupuncture and electroacupuncture (EA) can affect the growth of neuronal cells. Methods: Three groups of Lewis rats received 25 minutes of acupuncture twice a week for 10 weeks. The 3 groups of rats received treatment with either sham acupuncture (SA), real acupuncture (RA), or EA. After 10 weeks of treatment, skin and intestinal tissue were collected and analyzed for histology and mRNA expression of neuronal marker genes. Results: Compared with rats that received SA, rats that received RA and EA showed a significant increase in the mRNA expression levels of multiple neuronal genes in the skin. No significant histologic changes were seen. Conclusions: Acupuncture and EA result in significant changes in the expression of genes implicated as markers for neural stem cells, neural cell development, and neurons. This may, therefore, provide a novel avenue for developing treatments in patients suffering from intestinal aganglionic and neuropathic diseases.

A single-layer two-pole dual-band filtering antenna (DBFA) with orthogonal polarizations in the two bands is presented in this letter. The DBFA is based on a common dual-mode T-shaped resonator (TR). The two modes of the common resonator each couple to one of the two orthogonally placed patches, resulting in required radiation. The TR is responsible for generation of three transmission zeroes (TZs) in frequency response corresponding to each polarization at the broadside: two of them being intrinsic TZs due to the TR and the third caused by far field interference of TR's radiation with that of the patch.The low profile microwave design has its two passbands operating at 4.13 and 4.7 GHz (resulting in a frequency ratio of 1.14) with 10 dB return loss bandwidths of 1.2% and 2.9%, respectively.

We demonstrate the first-ever silicon photonics enabled hyper-wideband RF spread-spectrum link. A hybrid III/V-silicon photonic mode-locked laser encoded with a four-channel silicon photonic phase encoder is used to generate optical carriers that coherently demodulate a received RF signal spanning an instantaneous bandwidth greater than 85% of the center frequency (12/14 GHz). This allows low-speed (

In this paper, enhancement of phase-shifting nonreciprocity is proposed by using metamaterial lines with comb-shaped capacitive stubs on the normally magnetized ferrite substrate. The insertion of capacitive stubs enhances the effective permittivity, i.e., effective propagation distance in one propagation direction due to edge-guided mode propagation along the comb-shaped stub edges. The nonreciprocity of the proposed structure was numerically compared with those of other types of metamaterial lines, and transmission characteristics of the prototype circuit were measured and reproduced by the numerical simulations, verifying the enhancement.

A low-profile single-layer substrate integrated waveguide (SIW) diplexing filtering antenna with two-pole response in each channel is presented. Synthesis technique is proposed, which allows independent design of the filtering networks for the two channels. A common slot loaded SIW cavity is used to obtain the desired radiation in both channels. The diplexing filtering antenna provides quasi-elliptic response in both channels due to source-load coupling. The filtering antenna provides a maximum broadside gain of 2.65 and 2.7 dBi at operating frequencies of 5.25 (lower channel) and 5.8 GHz (upper channel), respectively. The interchannel isolation is more than 29 dB with a channel frequency ratio as low as 1.1.