Internet of Vehicles (IOV) is a wireless communication network that connects vehicles, Road-Side unit (RSU), and cloud system to deliver real-time serves for intelligent and connected transportation. As a core component of the IOV dedicated short-range communication (DSRC) chain, the receiver plays a vital role in sustaining communication between the On-Board Unit (OBU) and the RSU. To balance the image rejection requirement and system complexity, this paper presents an intermediate frequency (Low-IF) 5.8 GHz receiver with high receiving sensitivity. The presented receiver features a 5 MHz IF and incorporates a low-noise amplifier (LNA) and mixer for down-converting RF signals to the IF band. A band-pass filter (BPF) is utilized to reduce noise and interference out-of the targeted band. The following received signal strength indicator (RSSI) with a fixed gain of 60 dB extracts the envelope of the IF signal, which is sent to a single-to-differential converter (SDC) and a comparator with hysteresis for data recovery. Fabricated using a 180 nm CMOS process, the presented receiver occupies a silicon area of 460 μm × 845 μm. Measurement results show the receiving sensitivity is better than -80 dBm for both 5.83 GHz and 5.84 GHz, the designated ETC communication frequency. The results also indicate robust out-of-band rejection performance.

This work presents a 230-GHz, 128-unit, λ/2-spaced planar phased array receiver (RX) utilizing a 1-D SSPLL and a DTC phase shifter. To construct a large-scale phased array system with a precise λ/2 antenna spacing above 200 GHz, this work addresses three key challenges. First, to achieve cross-chip synchronization among multiple chips, a 1-D SSPLL is proposed to enable arbitrary local oscillator (LO) synchronization for each tile while reducing clock jitter, achieving a measured ultra-low jitter of 44 fs. Second, to reduce the loss of LO driving power while maintaining precise beam steering, a 7-bit DTC phase shifter cascaded with a subsampling multiplier is developed—with the measured integral nonlinearity (INL) of the DTC phase shifter being ≤+1.6/−1.0 LSB and the differential nonlinearity (DNL) is ≤+0.5/−0.7 LSB. Additionally, to expand IF bandwidth, a Mixer-First Zero-IF architecture for each RX unit is realized through the integration of an IQ sub-harmonic mixer. Measurement results demonstrate a 10-GHz IF bandwidth, with an IQ amplitude imbalance of ≤−0.4/+0.8 dB and an IQ phase imbalance of ≤−2.4°/+0.8°. Subsequently, 230GHz, 16-unit, and 128-unit CMOS planar phased arrays are packaged and tested. The 16-unit array achieves an equivalent isotropic conversion gain (CG) of 16–18 dB, an equivalent isotropic single-sideband (SSB) noise figure (NF) of 6–14 dB, and a scanning angle of ±45° in both horizontal (H) and vertical (V) planes, while the 128-unit array delivers an equivalent isotropic CG of 20-21 dB, an equivalent isotropic SSB NF of 4-10 dB, and an extended scanning angle of ±60° in both H and V planes.

In this article, a novel low-profile wideband bidirectional dual-circularly-polarized (DCP) reconfigurable transmitarray (RTA) antenna is proposed. The proposed design overcomes the limitations of conventional bidirectional antennas in bandwidth, profile height, and beam scanning performance. Firstly, to achieve dual-circularly-polarized radiation, a pair of orthogonal CP wideband reconfigurable transmit-reflect-array (TRA) cells are designed. The proposed TRA cell integrates two PIN diodes in the radiating patch to enable 1-bit transmission phase control for right-hand/left-hand CP (RHCP/LHCP) waves. Simultaneously, rotating the coupling structure of this TRA cell and leveraging anisotropic response achieves continuous 360° reflection phase modulation for LHCP/RHCP waves. Ground vias are further incorporated to form additional resonant structures, which significantly broaden the bandwidth. Secondly, leveraging the characteristics of the designed cells and the anomalous reflection principle, a low-profile layout of bidirectional radiation is implemented, reducing the overall antenna profile to one-third of conventional designs, effectively resolving the high-profile issue. Thirdly, the RHCP and LHCP TRAs act not only as reflectarrays for each other but also as transmitarrays for radiation, thus enabling bidirectional radiation. Lastly, to obtain the optimal 1-bit phase distribution for beam scanning, a physically-informed gradient phase optimization algorithm (PIGPOA) combining farfield physical information with gradient descent algorithm is proposed. Simulated and experimental results demonstrate that the 16 × 16 cells antenna modeled to validate the feasibility of this design achieves good bidirectional DCP beam scanning within ±50°, with peak gain and 3-dB gain bandwidth reaching 20.9 dBi and 28.6% (12.0 GHz - 16.0 GHz), respectively. This work provides a high-performance candidate solution for future wireless systems.

This paper proposes a multi-antenna based physical layer secure communication scheme and conducts a quantitative analysis of its secret key rate (SKR). Firstly, in order to meet the secure communication needs of long-distance terminals, a Rician fading multi-antenna secure communication model that conforms to the characteristics of satellite broadcast channels was established. Secondly, the upper and lower bounds of the SKR as well as its asymptotic limit under large-scale eavesdropping scenarios are derived, and the quantitative impacts of the antenna number ratio and channel gain ratio on the SKR limit are elucidated. To address the problem of limited antenna resources at the satellite, an optimal antenna number allocation strategy among legitimate terminals is further proposed. Simulations verify that tilting the antenna number allocation toward legitimate terminals with more prominent channel advantages can maximize the SKR. Compared with the uniform allocation of antenna numbers, the optimal allocation strategy can improve the SKR by up to 4.6% under certain scenario conditions. In addition, this strategy can achieve a positive SKR with only half the number of antennas. This scheme effectively addresses the issues of insufficient model adaptability and low resource efficiency in existing studies on satellite scenarios, providing a key theoretical basis for the design of satellite secure communication systems.

In this paper, a millimeter-wave full-metal circularly polarized AiP(Antenna-in-Package) with a cavity-backed structure is presented. The antenna consists of a regular octagonal patch, a C-shaped metal column, and a metal cavity-backed structure with an annular slot, where the patch is supported by the C-shaped metal column. This C-shaped metal column is connected to the ceramic substrate and excited by the GCPW(Grounded Coplanar Waveguide) structure to achieve circularly polarized radiation. The 3dB Axial Ratio(AR) bandwidth of the proposed antenna is 27.3-30GHz(9.4%).

To meet high efficiency and signal quality standards, digital pre-distortion (DPD) is widely used in base stations. It effectively balances the linearity and efficiency of power amplifiers (PA). Traditional research faces two challenges: first, the added overhead of the feedback link; second, the wide dynamic range of feedback signals, which imposes high demands on the ADC of the receiving chain. If these demands are not met, it can result in saturation distortion, thereby impacting DPD calibration. This work eliminates the need for a dedicated DPD feedback structure by repurposing the ISAC sensing receiver as the DPD calibration path. This approach avoids the hardware overhead of a conventional separate feedback link through innovative component reuse .The innovation introduced in this paper is the integration of folding technology into the receiver, thus effectively preventing saturation issues in the received signal. We present an optimization of transmission and reception beamforming, enabling signal folding followed by DPD processing without the need for recovery. Theoretical analysis and simulations demonstrated in this paper to show the quantization advantages of signal folding DPD. According to the performance result, the proposed method can achieve 2dB ACLR gain with 4bit quantization.

While beam-oriented digital predistortion (BO-DPD) is an effective technique to deal with power amplifier (PA) nonlinearity in hybrid beamforming (HBF) communication systems, it suffers from a limited linearization angle. Recent research shows such a drawback can be substantially mitigated by a post-weighting (PW) process. However, the linearization performance of traditional PW-DPD still has room for improvement since the PA distortion is therein approximated by a constant term irrelevant to the PW coefficients. In this work, we address the linearization angle widening issue via an iterative approach based on the alternating optimization framework, which leads to better performance in distortion reduction compared to the conventional PW scheme.

An ultra-sensitive temperature sensor via nonlinear optics (NLO) type-I second harmonic generation (SHG) in periodically poled lithium niobate (PPLN) is theoretically and experimentally studied. Like linear optics longperiod grating and Mach-Zehnder regime, a refractive group dispersion factor dominates the peak wavelength shifting. The sensitivity of SHG peak wavelength near the dispersion turning point (DTP) in phase matching relationship is nonlinear dependent on temperature, theoretically up to infinite. The sensitivity of unilateral peak wavelength and linewidth are more than 16.83 nm/degrees C and 2.88 nm/degrees C at 37 similar to 38.2 degrees C, respectively. The relative power at almost fixed DTP is determined as - 5/degree celsius. In addition, the SHG wavelength in 751 similar to 755 nm is demodulated by the linear rising edge of an optical spectrum filter instead of spectrometer. The proposed NLO sensor will enrich the ultra-sensitive strategy as the promotion and dual of linear optics. It is expected to be employed in the temperature monitoring of mammals and energy-efficient lithium niobate photonic integrated circuit (PIC).

In this article, the beam scanning range expansion and polarization diversity of a circularly polarized (CP) tightly coupled (TC) phased array are investigated. A systematic theoretical analysis of the scanning axial ratio (AR) is conducted, and guidelines for implementing wide-angle CP beam scanning phased array are provided. Following these guidelines, to achieve similar radiation patterns in the element's E- and H-planes, a novel method based on the Fourier transform relationship theory is proposed which instructs the element structure design by tailoring its surface current distribution. The influence of spatial phase difference between two orthogonal linearly polarized (LP) waves is analyzed, motivating the adoption of a colocated feed array topology. Furthermore, a wideband coupler is developed, and scanning blindnesses are effectively mitigated. An 8 x 8 dual CP phased array prototype is simulated, fabricated and measured, which demonstrates good impedance matching and scanning AR performance across the X-band with a beam scanning range up to +/- 70 degrees. In addition, the proposed array features a fully planar and modular architecture.

This letter proposes a compact, dual-band, dual-circularly polarized shared-aperture antenna based on the structure reuse of a dielectric resonator (DR) structure. The proposed antenna reuses a smaller DR, originally designed for the high-band (HB) radiator, as the radiating structure for the low-band (LB). It incorporates an LB right-hand circularly polarized (RHCP) dielectric resonator antenna (DRA) and an HB left-hand circularly polarized (LHCP) DRA into a compact shared-aperture construction, attaining a high aperture reuse efficiency. The RHCP radiation in the LB is produced by the DR mode, and the LHCP radiation in the HB is produced by the combination of the patch mode and the DR mode. Two operating bands can be adjusted independently. Additionally, the cross-band port isolation is improved by using band-stop filtering decoupling technology. For verification, an antenna prototype with a transverse size of 0.59 lambda(L) x 0.59 lambda(L) is fabricated. Measured results show that the proposed antenna has a -10 dB impedance bandwidth of 17.5% and 11.8%, and a 3 dB AR bandwidth of 7.4% (RHCP) and 7.47% (LHCP). The measured cross-band port isolation of more than 33.2 dB and 31.3 dB are obtained in the LB and HB, respectively.

Raman spectroscopy is a nondestructive, label-free optical analysis technique, and has seen various applications. Gated-Raman spectroscopy provides an effective way to suppress the influence of fluorescence photons. In this work, a novel Time-to-digital convertor (TDC) structure for gated-Raman spectroscopy is discussed. The proposed design consists of 32 independent, 30um height-TDC channels, which can be conveniently integrated with concurrent single photon avalanche diode (SPAD) technology. The TDC channel is constructed entirely by standard digital gates, and therefore uniformity among all TDC channels is naturally achieved. 13 rising edges for measurement are generated from delay interpolation, and the time-measuring accuracy is set as 48 ps, by two feedback locking loops referenced to a 100MHz clock. The digital-gate-only TDC channel makes the proposed design flexible to be expanded, and multiple such designs can be easily combined for more TDC channels if required.

We have proposed and experimentally demonstrated a bus temperature sensor array based on nonlinear optics second harmonic generation (SHG) in periodically poled lithium niobate (PPLN) and wavelength coded with poling period. The temperature response on bulk PPLN is studied by interrogating SHG spectra. Group dispersion factor and efficient thermal-birefringence between fundamental wave and second harmonic wave are proposed to describe peak wavelength shift. Single temperature sensor capitalizing on mode-locked laser provides 0.11 nm/degrees C sensitivity, 80 degrees C dynamic range around room temperature, and 2 degrees C temperature resolution. Additionally, a wavelength-coded 1 x 4 sensor array is demonstrated via quasi-comb spectra induced by poling period engineering. Each sensing unit has a unique poling period and SHG peak wavelength which can shift independently, and the temporal-evolved joint spectra of two non-cooperative targets confirm the practicability. The arrayed temperature sensors validate great applying potential on photonic integrated circuits (PIC).

This paper introduces a state-space modeling approach for target localization using axial magnetic fields. Through rigorous theoretical analysis and comprehensive simulation experiments, the study effectively demonstrates the proposed method’s ability to achieve precise and robust target positioning. The research underscores the significant advantages of state-space modeling in addressing the complexities inherent in magnetic target tracking, and it offers a novel and effective solution for enhancing localization accuracy in challenging environments.

Edge-enhanced imaging by spiral phase contrast has proven instrumental in revealing phase or amplitude gradients of an object, with notable applications spanning feature extraction, target recognition, and biomedical fields. However, systems deploying spiral phase plates encounter limitations in phase mask modulation, hindering the characterization of the modulation function during image reconstruction. To address this need, we propose and demonstrate an innovative nonlinear reconstruction method using a Laguerre-Gaussian composite vortex filter, which modulates the spectrum of the target. The involved nonlinear process spectrally transforms the incident short-wavelength-infrared (SWIR) signal from 1550 to 864 nm, subsequently captured by a silicon charge-coupled device. Compared with conventional schemes, our novel filtering method effectively suppresses the diffraction noise, significantly enhancing image contrast and resolution. By loading specific phase holograms on the spatial light modulator, bright-field imaging, isotropic, amplitude-controlled anisotropic, and directional second-order edge-enhanced imaging are realized. Anticipated applications for the proposed SWIR edge-enhanced imaging system encompass domains such as artificial intelligence recognition, deep tissue medical diagnostics, and non-destructive defect inspection. These applications underscore the valuable potential of our cutting-edge methodology in furthering both scientific exploration and practical implementations.

Rinehart-Luneburg lens antenna with feature of rotational-symmetric shape offers a wide angular range and multiple-beam capabilities. An integrated modeling and analysis approach is proposed in this paper to simplify the design of this antenna with non-parametric folded curve. An optimized Rinehart-Luneburg lens antenna working at Q-band with reduced profile is designed. The height of the designed lens has been reduced by a factor of 2.7 compared to original Rinehart-Luneburg lens. Eleven waveguides are placed at an angle of 12° provide beam scanning capability in 120° range with scan loss below 1 dB, a realized gain higher than 18.5 dBi over the whole bandwidth.

A voltage mode capacitance multiplier for ultra-low frequency physiological signal processing is designed with a circuit model. With the proposed multiplier, a filter can achieve a cutoff frequency of 12 mHz with a 1 pF basic capacitance and a 10 kΩ resistor. The corresponding multiplication factor will be 1.35 × 109. By changing the controlling terminal, the multiplication factor can be widely tuned from 1950 to 1.35 × 109 and the corresponding filter cutoff frequency will be from 12 mHz to 8.15 kHz. According to the circuit model, to further increase the multiplication factor to decrease the chip area, more multiplication stages can be added to the feedback loop.

Edge-enhanced imaging is invaluable in feature extraction, fingerprinting analysis, and biomedicine due to its ability to accentuate peripheries. Nevertheless, in systems employing vortex phase plates, the modulation of the phase mask is suppressed, resulting in the inability to characterize the modulation function during image reconstruction. To address this need, we propose a nonlinear reconstruction method that incorporates a superimposed vortex phase filter (SVPF) designed to modulate the spectrum of the target. In this paper real-time ultra-sensitive edge enhanced imaging in the short-wavelength-infrared (SWIR) region is demonstrated using nonlinear frequency upconversion. The SWIR signal at 1550 nm is spectrally converted to 864 nm for detection by a quantitative CMOS (qCMOS) camera. Anisotropic edge enhancement with controlled amplitude can be achieved by the SVPF. The imaging sensitivity at the single-photon level is realized by increasing the conversion efficiency and reducing the background noise of the upconversion system. By rapidly switching a series of specific phase patterns with a spatial light modulator, we also present the ability of the scheme to detect outlines and gradual edges in real time. The implemented SWIR edge-enhanced imaging system is expected to be directly used in non-destructive defect inspection and infrared monitoring of low-light objects.

This paper introduces a frequency division multiplexing (FDM) design of intermediate frequency (IF) that can be used for digital beamforming (DBF) phased array antennas, analyzes and describes on the basic principles and control methods for phase consistency between channels are present. After adopting this design, the number of A/D and D/A in digital processing can be greatly reduced, and the overall power consumption and cost can be reduced.

We have proposed and experimentally demonstrated an efficient ultra-sensitive mid-wavelength-infrared (MWIR) detector using a periodically poled lithium niobate nonlinear crystal and a silicon single-photon counting module. The involved frequency upconversion technique can spectrally convert the MWIR signal photons to the short-wavelength-infrared (SWIR) region. The internal quantum efficiency (QE) of the upconversion detector (UPD) reaches 8.87% at an average pump power of 10.67 W. The noise equivalent power of the UPD is measured as 3.24×10−15W/Hz1/2 at the MWIR wavelength of 4.6μm. In addition, the long-term stability is manifested by at least 12 h of operation with a relative fluctuation in the count rates as low as 0.35%.

A spaceborne Earth-coverage phased array (ECPA) antenna at Ka-band is proposed for low-Earth orbit (LEO) satellite applications, which is based on digital beamforming (DBF) partially shared subarray architecture to implement two stages of DBF. By taking into account the effects of mutual coupling in active element pattern optimization, a new method to obtain an Earth-matched beam of the equivalent element of the ECPA is presented, in which the DBF-shared subarray, segmental shaping technique, and differential evolution algorithm are utilized to achieve Earth-coverage characteristic for the ECPA. Both the design method and the principle of DBF partially shared subarray for grating lobe suppression are presented. Moreover, a 16-element DBF-shared subarray with a shared ratio of 4:1 obtaining an Earth-matched beam pattern is designed, optimized, and verified by full-wave simulation in Ansys Electronics Desktop. Taking the DBF-shared subarray as the equivalent element, an ECPA including 40 DBF-shared subarrays is also designed and simulated. Numerical results demonstrate that the proposed ECPA has excellent performance of Earth-coverage scanning to compensate for the satellite communication link variation caused by path loss variation during beam scanning for LEO applications. In addition, the ECPA has the advantages of a low sidelobe level better than -20 dB as well as grating lobe suppression.