Polarization-controlled bifunctional antenna based on 2-D anisotropic Gradient Metasurface

We have developed a micro fluxgate magnetic sensor using new printed circuit board (PCB) technology. The fluxgate sensor consisted of five PCB stack layers including one layer of magnetic core and four layers of excitation and pick-up coils. The center layer as a magnetic core was made of micro patterned amorphous magnetic ribbon with an extremely high DC permeability of ~100,000, and the core had a rectangular ring shape. Four outer layers as an excitation and pickup coils had a planar solenoid structure. The amorphous magnetic core was easily saturated due to the high permeability, low coercive field, and closed magnetic path for the excitation field. The chip size of the fabricated sensing element was 7.3 × 5.7 mm2. Excellent linear response over the range of –100 μT to +100 μT was obtained with sensitivity of 780 V/T at excitation sine wave of 3 Vp-p and 360 kHz. A very low power consumption of ~8 mW was measured. This low power, small size, and high sensitive fluxgate sensor to measure a low magnetic field is very useful for various applications.

An ultra-thin metasurface is proposed to realize wideband polarization-independent anomalous reflection. The sub-wavelength resonator can produce different resonance modes, which are the result of the combined effect of dielectric and the metallic structure. The gradient metasurface is done by six discrete orientation of the local sub-wavelength resonator which provides a phase gradient. The simulation and measured results show that 9[Formula: see text]GHz bandwidth of the anomalous reflection is achieved.

The use of Printed Circuit Board (PCB) technology for device packaging offers new opportunities to solve these challenges. During the past decade embedding of semiconductor chips into PCB structures evolved from a research topic to volume production. The paper will briefly describe this development and categorize today's embedding technologies. First modules with embedded chips are in production in Asia and Europe, mainly for mobile applications. In Europe embedding has gained a strong interest for power modules, especially in automotive applications. Main drivers are the capability for compact and thin packaging, the high reliability and cost saving potential. The automotive industry has a strong demand for highly reliable and cost-efficient electronics. Especially the upcoming generations of hybrid cars and fully electrical vehicles need compact and efficient 400 V power modules. Within the engine compartment installation space is of major concern. Therefore small size and high integration level of the modules are needed. Embedding of power switches, and controller into compact modules using PCB (Printed Circuit Board) technologies offers the potential to reduce the thickness and size of the module. In order to replace DCB ceramics, a structure of thermal laminate material between Cu layers has been developed and the capability for thermal conduction and electrical insulation has been evaluated. For the assembly of large power IGBTs with sizes of 100 mm² and larger, new silver sintering pastes have been evaluated. They enable a pressure-less sintering at 200 °C, compatible with PCB materials. To handle the high switching current of up to 200 A, suitable copper tracks in the PCB are required. The realization of such thick copper lines with thickness up to 1 mm requires advanced processing, compared to conventional multilayer PCB production. In order to form complex power systems out of modules with embedded chips interconnections by Ag sintering are under development.

This paper introduces the design of an air-filled substrate integrated waveguide (AFSIW), and a transition design from microstrip line (ML) to AFSIW at 60 GHz. The proposed structure is realized by printed circuit board (PCB) technology so that the fabrication cost is low and the whole structure is easy to be integrated with other planar components. An equivalent circuit model of the proposed ML-AFSIW transition is proposed and verified by full-wave simulation. To verify the proposed idea, a back-to-back transition is designed, fabricated and measured. The measured return loss is higher than 15 dB from 60.6 to 64.5 GHz. The minimum of measured insertion loss is 0.2 dB at 61 GHz. The measured results show that the proposed ML-AFSIW transition is suitable for millimeter-wave (mm-Wave) application.

Manipulation of acoustic wavefronts by thin and planar devices, known as metasurfaces, has been extensively studied, in view of many important applications. Reflective and refractive metasurfaces are designed using the generalized reflection and Snell's laws, which tell that local phase shifts at the metasurface supply extra momentum to the wave, presumably allowing arbitrary control of reflected or transmitted waves. However, as it has been recently shown for the electromagnetic counterpart, conventional metasurfaces based on the generalized laws of reflection and refraction have important drawbacks in terms of power efficiency. This work presents a new synthesis method of acoustic metasurfaces for anomalous reflection and transmission that overcomes the fundamental limitations of conventional designs, allowing full control of acoustic energy flow. The results show that different mechanisms are necessary in the reflection and transmission scenarios for ensuring perfect performance. Metasurfaces for anomalous reflection require non-local response, which allows energy channeling along the metasurface. On other hand, for perfect manipulation of anomalously transmitted waves, local and non-symmetric response is required. These conclusions are interpreted through appropriate surface impedance models which are used to find possible physical implementations of perfect metasurfaces in each scenario. We hope that this advance in the design of acoustic metasurfaces opens new avenues not only for perfect anomalous reflection and transmission but also for realizing more complex functionalities, such as focusing, self-bending or vortex generation.

Printed circuit boards (PCBs) are designed for packing two or more semiconductor chips. On these PCBs, there are various types of faults in the wiring. We must therefore test the PCBs to detect these faults, and it is essential to establish an efficient testing method. One type of test method uses two probes. Two probes, each touching one edge (end) of an inter-chip wiring, are used to check for the presence of faults. Testing is complete when we have confirmed that no faults exist on the PCB. The objective is to minimize the completion time for the testing, that is, our aim is to design efficient routes for the two probes; this is a two-probe routing problem. Several previous studies have proposed an approach involving a two-phase method. Although the two-phase method quickly finds a feasible solution, there is no guarantee that the solution is good. Besides, in recent years, PCB technology provides dense assembly capability and increased chip packaging; this implies that the scale of the two-probe routing problem becomes larger and the problem is difficult to be solved. We therefore propose a new approach, where we formulate a two-probe routing problem as a combinatorial optimization problem and then, we solve the combinatorial optimization problem by using genetic algorithm.We expect that our approach is useful for solving the large-scale problems. In computational experiments, we compare the results of our approach with those obtained using the two-phase method, and we show that our approach outperforms the two-phase method.

A phase Gradient Metasurface (GM) is proposed to improve performance of low profile planar antenna by anomalous reflection and surface wave coupling. The unit cell of GM is composed of eight resonating metallic patch with self symmetric property in vertical direction by repetition of the resonating square patches. A prototype of the design has simulated using CST Microwave Studio to validate our proposal.

Since the 1960s, interconnection technology has been dominated by implementations of printed circuit board (PCB) technology. However, in response to the ever increasing demand for higher routing densities and improved electrical performance, this technology has been increasingly challenged by multichip module (MCM) technology and in particular the MCM‐L type. MCM‐L technology is a laminate construction and is basically a further development of PCB technology with two or more bare chips and fine line interconnects. Consequently, it is perceived that the current PCB fabricators are ideally positioned to take the initiative with MCM‐L technology. Reviews the current state of PCB industry and MCM‐L technological (process and material) requirements, within the UK, such that a comparison can be made between the two technologies. Planning, training and investment requirements for new technology implementation are then identified and compared with PCB fabricators’ technological, training, planning and investment capabilities. The shortfalls between MCM‐L fabrication requirements and PCB fabricators capability are identified and discussed.

One of the beneficial methods being widely used to preserve genetic resources of imperiled animals or improved agricultural animals is cryopreservation of germplasm. During this process, the biological structure of the cells remains relatively intact by freezing and storing them at very low temperatures. Freezing condition plays an essential role in cryopreservation procedure since the exposure of the cells to low temperature can cause damage to the cells [1]. Therefore, accurate monitoring of the freezing process can improve the recovery rate of the cells after thawing. During the phase change phenomena, the dielectric and conduction properties of ice changes [2]. Herein we present, a portable platform for monitoring of the freezing and thawing processes based on the electrical impedance of the samples during cryopreservation. The system is composed of a portable temperature and impedance measurement system in conjunction with an impedance sensing probe fabricated with printed circuit board (PCB) technology. The impedance measurement circuit, temperature measurement circuit, control unit for data acquisition and wireless communication and touch screen LCD with a graphical user interface are the building blocks of the measurement system that enables users to perform impedance measurement at single or multiple frequencies with various excitation signals (Figure 1A). Utilizing impedance measurement instead of DC resistance measurement enable us to monitor both dielectric properties and resistance changes during phase change and avoids the polarization of the electrodes. In addition, an impedance sensing probe was developed by using PCB technology, which provides accurate electrodes fabrication at low cost. The probe has been designed to be used within 0.5 ml French straw which is a conventional container in cryopreservation application. Pair of parallel electrodes were fabricated on the probe at three detection zones (Figure 1B). The system was evaluated at different cryopreservation conditions including various sample solutions and cooling rates. Hank's Balanced Salt Solution (HBSS) is being widely used in cryopreservation to maintain cells in a viable state. The system was characterized by measuring the impedance in HBSS and DI water solutions solution. The 0.5 ml French straws were filled sample solution along with the probe and a T-type thermocouple. Next, the samples were placed on top of the liquid nitrogen with a 2 cm gap to freeze, and after the sample temperature reached lower than -40 oC, the samples were left at room temperature to thaw. During this process, the impedance and temperature were measured inside the samples. Figures 1C and 1D show the magnitude and phase of the measured impedance for HBSS and DI water sample respectively. When the HBSS sample starts to freeze, the impedance magnitude does not change before the latent heat removal stage. However, the impedance phase starts to increase after the sample cools down. It reaches a minimum value during nucleation and increases during latent heat removal. Therefore, the phase change phenomena can be detected with the imaginary part of the impedance. In the DI water case, the impedance starts to increase by cooling down the solution when the nucleation happens there it remains relatively constant, and it keeps increasing after that. This shows that the solution containing various ions has different impedance characteristics, which can be used as a parameter to monitor the cryopreservation phenomena. The system was also characterized by different solutions containing salts and cryoprotectants, frozen at various cooling rates, to further investigate the potential of impedimetric sensors in quality control for cell freezing protocols. Figure 1

In this letter, we proposed to achieve wideband polarization-independent anomalous reflection for linearly polarized (LP) waves based on the phase gradient metasurface (PGM) with a dispersionless phase gradient. A polarization-keeping metasurface reflector for circularly polarized (CP) waves was firstly presented. Based on the reflector, a reflective PGM was designed to realize dispersionless but adverse phase gradients for left- and right-handed circularly polarized (LCP and RCP, respectively) waves. Under normal incidence, high-efficiency anomalous reflection occurs for both LCP and RCP waves with opposite-signed reflection angles. Under the LP wave incidence, the reflected waves are separated into two beams due to the decomposition of LP waves into LCP and RCP waves. The anomalous reflection of LP waves is independent of the polarization angle. Both the experimental and simulated results are consistent with theoretical predictions, which convincingly verifies the wideband polarization-independent anomalous reflection of LP waves.

A single-layer reflecting element is proposed based on the principle of linear-to-circular polarization conversion focusing metasurface, which can independently control the phases of x-polarized and y-polarized reflecting waves and operate in a broadband of 10-14 GHz. Following the generalized Snell's laws of reflection, a super cell is designed with a phase-gradient of -60 for x-polarized waves and 60 for y-polarized waves, and the simulation results show the well wideband anomalous reflection as expected. In the design of the multifunctional metasurface, the 1313 unit cells are used to satisfy the parabolic profile and the focal-distance-to-diameter ratio is set to be 0.5. The phase compensation for forming a constant aperture phase is provided by the individual reflected elements with different structure parameters and x-y=90 is used to realize polarization conversion. The designed sample is simulated in CST Microwave Studio and the results show that both of the x-polarized and y-polarized plane waves are well focused through the reflection of the focusing metasurface in a broadband of 10-14 GHz. Traditionally, multi-layer element is used to broaden phase coverage and bandwidth, the single-layer design in this paper greatly reduces the cost, processing difficulty and thickness of the lens. For further application, a linearly polarized Vivaldi antenna with a highest gain of 10 dB is located at the focal point of metasurface and the angle included between its polarization direction and x-axis is 45 in order to acquire right-handed circularly polarized reflecting wave. According to the reversibility principle of electromagnetic wave propagation, the spherical wave radiated by the feed antenna is converted into plane wave by the reflection of the focusing metasurface so that the antenna gain is remarkably enhanced. Simultaneously, the linearly polarized wave can be transformed into circularly polarized wave. Finally, the feed antenna and the metasurface are fabricated, assembled and measured. Numerical and experimental results are in good agreement with each other, which shows that the -1 dB gain bandwidth of the high-gain antenna is 24% (11-14 GHz) and the 3 dB axial ratio bandwidth is 29.8% (10-13.5 GHz). In addition, the gain at 12 GHz reaches a highest value of 19.6 dBic, and the aperture efficiency is more than 54%. The good performances indicate that the proposed broadband high-gain circularly polarized antenna has a well promising application in various communication systems. It is worth noting that the horizontally polarized, vertically polarized, right-handed circularly polarized and left-handed circularly polarized high-gain antenna can be realized with the rotation of feed antenna. In this case the idea is more versatile and valuable for designing the polarization reconfigurable antenna systems.

A planar phase gradient metasurface (PGM) with phase gradients in two in-plane directions will introduce two additional wave vectors to the reflected wave vector. For small incident angles, close to the normal vector, the magnitude of the reflected wave vector is smaller than that of the incident wave vector and the direction of the anomalous reflected wave can be determined from the incident wave vector components and additional phase gradient components. The expanded generalized Snell’s law, which includes diffraction order modes, is combined with array theory to accurately predict the directions of the reflected waves from a planar PGM for incident angles where the magnitude of the reflected wave vector is larger than that of the incident wave vector. The predicted directions of the reflected waves from a planar PGM are compared with simulated RCS results obtained with CST Studio Suite and measured results obtained in a compact range.

This paper presented one novel microstrip antenna with triple-band triple-mode and triple-polarization (TBTMTP) characteristics. In the lower frequency band, the antenna operates in the linearly polarized (LP) dipole mode with omnidirectional radiation pattern along the YOZ plane which is like one horizontally located dipole antenna. In the middle frequency band, the antenna operates in the LP dipole mode with omnidirectional radiation pattern along the XOY plane which is like one vertically located dipole antenna. While in the upper frequency band, the antenna works in the circularly polarized (CP) patch mode with directional radiation patterns along the Z-axis direction. Three modes with different patterns were excited in three different bands because of the mutual-coupling periodical circular patches and inductance metal pins. By etching inverted L shaped slot in the down circular mental patch, CP is realized for the patch mode without affecting the other two modes. The surface current distribution is introduced to analyze the antenna working principle. Due to the compact structure, easy fabrication, radiation pattern selectivity and polarized diversity, this antenna has potential application value in wireless communications in future.

Microwave measurements of minute dielectric property variations have many advantages such as noninvasive test, rapid sensing capability, and being label-free. Several researches including concentration detection are promoted by measuring the minute dielectric property variations of samples. Highly sensitive and accurate device is required for measurement of electrolyte concentration in biological fluids, especially when measuring samples in nanoliter or less scale. In this paper, a miniaturized broadband coplanar waveguide (CPW) transmission-line (TL) sensor with enhanced sensitivity is proposed. The sensitive device is realized by introducing interdigital capacitance (IDC) at the central conduction band of the CPW TL. The sensor is fabricated using print circuit board (PCB) technology with a microfluidic channel designed on it. A calibration based on microwave network theory is used to obtain the characteristic impedance and propagation constant of the sensing part. And accordingly, variations in magnitude and phase of S-parameters are employed to express the changes in concentration of the sample. Furthermore, an extracted equation between S-parameters and electrolyte concentration of the sample is first proposed. Experiments show the proposed sensor can detect the minimum concentration of 0.05 g/l for the three electrolytes (NaCl, KCl, and GaCl2 in deionized (DI) water)). Compared with a corrugator coplanar transmission line and a split ring resonator senor, the proposed sensor has a much higher sensitivity. Moreover, the device is robust in front of cross sensitivity caused by external factors (such as temperature variations, moisture, etc.). Thus, the proposed sensor is well suited for low-cost, real-tine, and CMOS compatibles sensing technologies.

Rotational electret energy harvester (EH) is prototyped for powering low-power electronics from human motion. Stator with electrodes and rotor with electret are fabricated using flexible print circuit board (PCB) technology, which makes it easier to combine with metal ball bearing for rotational support. The maximum thickness for the rotational part including the eccentric mass is as thin as 3.3 mm. Output power up to 80 μW has been obtained from arm swing during walking at 1.45 m/s in our initial test.