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To achieve a low-profile, wide-bandwidth, and highly selective design, this paper presents a substrate integrated suspended line (SISL) based broadband filtering dielectric resonator antenna (DRA) with the improvement of suppression level. The dielectric resonator is cylindrical and fed from the bottom by a microstrip-coupled slot. The dual head structure with the designed open stub can provide two radiation nulls on both sides of the passband for the filtering function and can excite three resonant modes (HEM $_{11\delta} $ , HEM $_{11\delta} $ , and TE131 mode) at different resonant frequencies to enlarge the impedance bandwidth of the proposed antenna. Then, adding a metal branch perpendicular to the feeder can offer a radiation null to eliminate the undesired resonances in the right stopband. Finally, the suppression level at high frequency is improved further by filling Sub2’s cavity with FR4. A prototype has been manufactured and measured for demonstration. Measurement shows that the proposed antenna has a - 10-dB impedance bandwidth of 32.9% (2.98-4.15 GHz), a flat gain within the passband, and the gain suppression level within the stopband exceeds 15.5 dB.

Abstract Hand gesture recognition based on micro‐Doppler (MD) radar has garnered considerable attention from researchers as a potential method for human–computer interaction (HCI). However, two significant challenges, that is, obvious differences in MD map size and lots of redundant information contained in the MD maps, are encountered. Here, a multi‐scale graph‐based hand gesture recognition framework is proposed. First, a MD graph representation method is developed, which is adapted to arbitrary‐sized frames and enables to map the key features in a sparse manner. Then, the multi‐scale information from MD graph is fully extracted for hand gesture recognition. Experimental results show that the proposed framework achieves a state‐of‐the‐art accuracy of 96.73% on the four‐class radar hand gesture dataset, while reducing up to 99% of the redundant information in the MD maps. This framework requires only a little amount of memory storage with good hand gesture recognition capability, demonstrating its high potential in the HCI field.

Abstract This paper proposes a technique named self‐packaged metal integrated suspended line (MISL) to design a high Q factor bandpass filter (BPF). This unique construction simplifies the traditional suspended stripline and substrate integrated suspended line configuration and creates a loss‐reduced structure, allowing for the implementation of high Q‐factor circuits. To demonstrate the advantages of the MISL platform, the shorted 3D metal stepped impedance resonators are first investigated using a miniaturized prototype based on this novel platform. Subsequently, a third‐order BPF based on MISL technology is designed, fabricated, and characterized. The fabricated BPF exhibits a minimum insertion loss (IL) of 0.31 dB, with centre frequencies of 5.88 GHz and 3‐dB fractional bandwidths of 19.8%, respectively.

Abstract This letter presents a compact fully differential branch‐line coupler. It is composed of folded substrate integrated suspended parallel strip line (SISPSL), which can generate slow‐wave effect and help reduce the circuit size. The used SISPSL type line is a fusion of double‐sided parallel‐strip line (DSPSL) and substrate integrated suspended line (SISL), which has the advantage of self‐packaging as compared with traditional DSPSL exposed to air. A DC to 30‐GHz differential transition from grounded coplanar waveguide (GCPW) to SISPSL is designed to test the SISPSL differential coupler. The implemented SISPSL branch‐line coupler has a compact size of 0.056 λg × 0.05 λg.

Based on the theory of reliability enhancement testing technology, this study used a variety of testing combinations and finite element simulations to analyze the stress–strain properties of 3D packaging storage modules and then evaluated its operating and destruction limits during temperature cycling tests (−65 °C~+150 °C) for the purpose of identifying the weak points and failure mechanisms affecting its reliability. As a result of temperature cycling ultimate stress, 3D packaging storage devices can suffer from thermal fatigue failure in the case of abrupt temperature changes. The cracks caused by the accumulation of plastic and creep strains can be considered the main factors. Crack formation is accelerated by the CTE difference between the epoxy resin and solder joints. Moreover, the finite element simulation results were essentially the same as the testing results, with a deviation occurring within 10%.

In recent years, biomedical optics technology has developed rapidly. The current widespread use of biomedical optics was made possible by the invention of optical instruments. The advantages of being non-invasive, portable, effective, low cost, and less susceptible to system noise have led to the rapid development of functional near-infrared spectroscopy (fNIRS) technology for hemodynamics detection, especially in the field of functional brain imaging. At the same time, laboratories and companies have developed various fNIRS-based systems. The safety, stability, and efficacy of fNIRS systems are key performance indicators. However, there is still a lack of comprehensive and systematic evaluation methods for fNIRS instruments. This study uses the fNIRS system developed in our laboratory as the test object. The test method established in this study includes system validation and performance testing to comprehensively assess fNIRS systems' reliability. These methods feature low cost and high practicality. Based on this study, existing or newly developed systems can be comprehensively and easily evaluated in the laboratory or workspace.

As numerical weather forecasting advances, there is a growing demand for higher-quality atmospheric data. Hyperspectral instruments can capture more atmospheric information and increase vertical resolution, but there has been limited research into retrieval algorithms for obtaining hyperspectral microwaves in the future. This study proposes an atmospheric temperature profile detection algorithm based on Convolutional Neural Networks (CNN) and Local Attention Mechanisms for local feature extraction, applied to hyperspectral microwave sensors. The study utilizes the method of information entropy to extract more effective channels in the vicinities of 60 GHz, 118 GHz, and 425 GHz. The algorithm uses the brightness temperature as the input of the network. The algorithm addresses common issues encountered in conventional networks, such as overfitting, gradient explosion, and gradient vanishing. Additionally, this method isolates the three oxygen-sensitive frequency bands for modularized local feature extraction training, thereby avoiding abrupt changes in brightness temperature between adjacent frequency bands. More importantly, the algorithm considers the correlation between multiple channels and information redundancy, focusing on variations in local information. This enhances the effectiveness of hyperspectral microwave channel information extraction. We simulated the brightness temperatures of the selected channels through ARTS and divided them into training, validation, and test sets. The retrieval capability of the proposed method is validated on a test dataset, achieving a root mean square error of 1.46 K and a mean absolute error of 1.4 K for temperature profile. Detailed comparisons are also made between this method and other commonly used networks for atmospheric retrieval. The results demonstrate that the proposed method significantly improves the accuracy of temperature profile retrieval, particularly in capturing fine details, and is more adaptable to complex environments. The model also exhibits scalability, extending from one-dimensional (pressure level) to three-dimensional space. The error for each pressure level is controlled within 0.7 K and the average error is within 0.4 K, demonstrating effectiveness across different scales with impressive results. The computational efficiency and accuracy have both been improved when handling a large amount of radiation data.

Abstract This work proposes a compact voltage‐controlled oscillator (VCO) using the transformer‐based triple‐tanks on substrate integrated suspended line (SISL) platform for 5G applications. In order to broaden the tuning range, the varactors are loaded on the second tank to avoid the effect of parasitic capacitance of bipolar junction transistors (BJTs) on the tuning range, and compact transformed triple‐tanks are designed to decrease the parasitic capacitance. By using a compact transformed triple‐tanks and double layers wiring technology, the core circuit area is only 0.1λg × 0.1λg, which is the smallest among the reported board‐level VCOs. Although the low‐cost FR4 is chosen, the phase noise is still acceptable by adopting cross‐coupled topology and multi‐tanks technology. The measured results show that the VCO exhibits a wide tuning range of 28.9% from 2.88 to 3.85 GHz, and the best phase noise is –119.45 dBc/Hz @1 MHz at 3.76 GHz.

In this paper, a multi-mode magnetically coupled and tuned inductive peaking technique with impedance transforming capability is proposed to achieve a wider operational locking range in the injection locked frequency divider (ILFD) for low injected power levels. Fabricated in 65 nm CMOS process, the proposed ILFD operating at 60 GHz, achieves a locking range of 16.3% from 53.2 to 63 GHz with a low injected power of -10 dBm. Occupying a small area of 0.0288 mm2, the ILFD delivers an average single-ended output power of -6 dBm with a dc power consumption of 3.7 mW from a 1.2 V supply voltage. The power efficiency (Pout/Pdc) of the proposed ILFD is 6.8%.

The linearity of active mixers is usually determined by the input transistors, and many works have been proposed to improve it by modified input stages at the cost of a more complex structure or more power consumption. A new linearization method of active mixers is proposed in this paper; the input 1 dB compression point (IP1dB) and output 1 dB compression point (OP1dB) are greatly improved by exploiting the “reverse uplift” phenomenon. Compared with other linearization methods, the proposed one is simpler, more efficient, and sacrifices less conversion gain. Using this method, an ultra-high-linearity double-balanced down-conversion mixer with wide IF bandwidth is designed and fabricated in a 130 nm SiGe BiCMOS process. The proposed mixer includes a Gilbert-cell, a pair of phase-adjusting inductors, and a Marchand-balun-based output network. Under a 1.6 V supply voltage, the measurement results show that the mixer exhibits an excellent IP1dB of +7.2~+10.1 dBm, an average OP1dB of +5.4 dBm, which is the state-of-the-art linearity performance in mixers under a silicon-based process, whether active or passive. Moreover, a wide IF bandwidth of 8 GHz from 3 GHz to 11 GHz was achieved. The circuit consumes 19.8 mW and occupies 0.48 mm2, including all pads. The use of the "reverse uplift" allows us to implement high-linearity circuits more efficiently, which is helpful for the design of 5G high-speed communication transceivers.

Stretchable tactile sensors are popular in soft and conformable electronics, and innovations in their architectural design and manufacturing process are in demand for more advanced applications. In this work, a resistive-type core-shell tactile sensor was designed and fabricated via the coaxial ink writing of a continuous single core-shell fiber. Particularly, a facile tubular deposition modeling method was established, in which deionized (DI) water was selected as the core and first coextruded with the elastomeric shell and then scarified and replaced by injecting liquid metal (LM). To weave the continuous single core-shell fiber, tactile sensing nodes were formed easily and precisely to position-registered mechanical pressure stimuli. The resistive responses including sensitivity, coupling and reliability of the sensor architecture were examined, and the tracing mode was performed. Furthermore, the tactile sensor could be directly patterned on a 3D surface. The core-shell fiber-based tactile sensor design and its scalable manufacturing are significant for the advanced fabrication of 3D printed conformable electronics. Keywords: Stretchable resistive tactile sensor, Core-shell fiber, Sacrificial coaxial ink writing, Conformable printing