Search

This paper presents the latest developments regarding the single-feed Quality Wideband Linear (QWL) wire array antenna, known for its broadband and high-gain electromagnetic characteristics and robust design. A systematic review of recent advances in relation to the QWL antenna is provided, covering its driven element, director, reflector, low common-mode current interference connector, and array series-feed configuration. For the first time, an analytical expression and a quick design formula for the input impedance of the QWL antenna’s driven element, the linear Wideband High-gain Electromagnetic Structure (WHEMS) antenna, are presented. Theoretical analysis demonstrates the potential for broadband performance using the WHEMS antenna. The rugged design of the QWL array antenna offers engineering advantages such as simple feeding, low wind resistance, a lightweight construction, low cost, and structural robustness. The QWL antenna has already found applications in various industrial sectors, with potential for broader use in the future, contributing to further advancements in antenna technology.

Enhancing road safety by monitoring a driver’s physical condition is critical in both conventional and autonomous driving contexts. Our research focuses on a wireless intelligent sensor system that utilizes millimeter-wave (mmWave) radar to monitor heart rate variability (HRV) in drivers. By assessing HRV, the system can detect early signs of drowsiness and sudden medical emergencies, such as heart attacks, thereby preventing accidents. This is particularly vital for fully self-driving (FSD) systems, as it ensures control is not transferred to an impaired driver. The proposed system employs a 60 GHz frequency-modulated continuous wave (FMCW) radar placed behind the driver’s seat. This article mainly describes how advanced signal processing methods, including the Huber–Kalman filtering algorithm, are applied to mitigate the impact of respiration on heart rate detection. Additionally, the autocorrelation algorithm enables fast detection of vital signs. Intensive experiments demonstrate the system’s effectiveness in accurately monitoring HRV, highlighting its potential to enhance safety and reliability in both traditional and autonomous driving environments.

Radio sensitivity serves as a commonly used parameter in wireless receiver systems. When excess antenna noise is introduced into the system, it results in a reduction of radiated sensitivity. This phenomenon, referred to as radiated sensitivity desensitization, occurs upon connecting antennas. This paper elucidates a shared impedance noise coupling mechanism, which sheds light on how passive antennas can introduce excess noise into the wireless system. To address this apparent contradiction, the paper introduces the general theory of antenna noise temperature, providing an explanation for the mechanism of noise coupling through a shared impedance path. Additionally, a mathematical expression for radiated sensitivity is presented in this paper. An understanding of this noise coupling mechanism holds significant implications for various fields, including antenna technology, electromagnetic compatibility, radio science, remote sensing, and wireless communication systems.

In modern wireless communication systems, the signal-to-noise ratio (SNR) is one of the most important performance indicators. When the other radio frequency (RF) performance of the components is well designed, passive intermodulation (PIM) interference may become an important factor limiting the system’s SNR. Whether it is a base station, an indoor distributed antenna system, or a satellite system, there are stringent PIM level requirements to minimize interference and enhance network capacity in multicarrier networks. Especially for systems of high power and wide bandwidth such as 5G wireless communication, PIM interference is even more serious. Due to the complexity and uncertainty of PIM, measurement is the most important means to study and evaluate the PIM performance of wireless communication systems. In this review, the current main PIM measurement methods recommended by International Electrotechnical Commission (IEC) and other standard organizations are introduced, and several key challenges in PIM measurement and their solutions (including the design of PIM tester, the location of the PIM sources, the design of compact PIM anechoic chambers, and the evaluation methods of PIM anechoic chambers) are highlighted. These challenges are of great significance to solve PIM problems that may arise during device characterization and verification in real wireless communication systems.

A broadband compact antenna is proposed in this paper with an enhanced broadside gain performances in the +/− z directions. A design method of complementary gains is presented to overcome the gain reduction caused by the cancellation of reverse currents in the middle of the band of interest, where a design equation of the excited element of the antenna is given. This objective is achieved by accurately analyzing the resonant modes of the two parallel connected antennas of the excited element in order to achieve an overall wideband radiator. An orthogonal radiating choke (ORC) is proposed to remove the gain depression due to the leakage of electromagnetic waves toward the upper portion of the band of interest through simultaneously enhancing the broadside gain and choking the end-fire travelling wave. Each one patch of the ORC acting as both a TM10 mode microstrip antenna and a choke of end-fire travelling wave. With the help of the ORC, the gain in +/− z directions is enhanced by 13.1 dB at 6 GHz compared to that without the ORC. The proposed antenna presents a realized broadside gain of 2.1-7.8 dBi in the +/− z directions within a bandwidth of 158% (700 MHz – 6 GHz). Both the simulated and measured results demonstrate that the proposed antenna exhibits desirable bandwidth and gain characteristics and is a promising candidate for broadband integrated wireless systems.

Human retina is by nature a superior image sensor with a high sensitivity, wide dynamic range as well as low power consumption. In this paper, an image sensor array based on randomly-accessible active pixel design is studied where to mimic retinal photoreceptor, a photodiode-body-biased MOSFET (PD-MOS) with an adjustable gain of 10–420000 (higher than 105), a wide dynamic range of 140 dB and a spectral responsibility of 3-25000A/W from near UV to near IR wavelengths, is proposed. The image sensor array can capture images under light intensity ranging from 10nW/cm2 to 3mW/cm2 and its dynamic range is approximately 110dB.

In large-area dynamic imaging, an active pixel sensor (APS) is proposed. However, there is a trade-off between signal-to-noise ratio (SNR) and spatial resolution. To resolve this, a 256 × 256 active pixel image sensor array based on a 3-D dual-gate photosensitive thin-film transistor (TFT) is presented in this work, with a pixel pitch of 50 μm, pixel fill factor of 63%, photoconductive gain of 102–104 and spatial resolution of 505 ppi. An electronic global shutter is enabled by dual-gate biasing without additional a shutter TFT. Such an array is capable of dynamic imaging at a frame rate of 34 Hz.

In order to reduce the probability of automobile safety incidents, the in-vehicle occupant monitoring is indispensable. However, occupant monitoring using frequency-modulated continuous wave (FMCW) radar can be challenging due to the interference from passengers’ posture, movement, and the presence of multiple people. This paper proposes an improved method for generating point clouds using FMCW radar. The approach involves point cloud clustering, post-processing operations such as segmentation, merging, and filtering of the clustered point cloud to match the actual in-vehicle environment, and a state machine combination step. Experimental results show that the proposed method can achieve high recognition accuracy in scenarios with multiple passengers who are moving and sitting in a relaxed manner.

In optical sensors and imagers, high gain that leads to high sensitivity and high signal to noise ratio (SNR) is often desirable. One popular approach is avalanche photomultiplication initiated by impact ionization in an avalanche photodiode or similar devices and the other approach is active pixel sensor (APS) with in-pixel amplifier. However, the former requires high electric field which induces high shot noise and the latter needs a multiple-transistor pixel circuit which compromises the fill factor and consequently, reduces the SNR. This work proposes and summarizes our recent efforts taken to achieve high gain optical sensors through subthreshold operation of photodiode-gated transistors.

The measurement of the phased array antenna (PAA) is completely different from the traditional antenna, due to its multi beam patterns. Usually, each beam pattern of the PAA needs a separate measurement, which makes the overall time extremely long. Thus, the traditional method can no longer meet the efficiency and cost requirements of new PAA measurement. In this paper, a pattern reconstruction method is proposed which significantly reduce the measurement time of multi-beam PAAs. With the known array element patterns (AEP) and theoretical weighted port excitation of the beams, any beam pattern can be predicted by measuring only a certain beam pattern, due to the element excitation coefficient (including the matching, mutual coupling, and manufacturing factors, etc.) of the specific PAA being calculated. The approach has low reconstruction error in term of beam pointing accuracy, side lobe, and co-polar and cross-polar patterns while being validated for large scanning range. Through theoretical derivation and experiments, the effectiveness of the method is verified, and the testing efficiency of the phased array antenna can be improved by 10 times or even more.