Spiral Slot Research Articles

Characteristic analysis of the vortex excited using the photoacoustic transducer with a spiral light absorption surface

Abstract It is proved that the vortex acoustic field can be excited with laser by designing the photoacoustic transducer with a spiral light absorption surface. The generated acoustic field has a spiral phase wavefront, and the pressure on the central axis along its propagation direction is zero. The orbital angular momentum that can be used for positioning and manipulation of particles is formed by the vortex. The characteristics of the generated acoustic vortex at different frequency and detection position are analyzed for 1-5 topological charge. And the influence of the geometric configurations such as the width and size of logarithmic spiral slot are also studied for the achieving the desired vortex field with focused intensity.

A substrate-integrated waveguide-based wideband circularly polarized slot antenna using the parasitic square patch array

In this paper, a planar low-profile wideband circularly polarized substrate-integrated waveguide (SIW) based antenna is investigated. The antenna comprises two substrates stacked over each other. The top layer of the antenna is loaded with a 4 × 4 array of parasitic square patches stacked over a spiral slot loaded in the SIW cavity. The spiral slot is utilized for the generation of narrow band circular polarization and to enhance the CP bandwidth, the parasitic patch array is excited through the electromagnetic coupling mechanism without any air gap between them. The antenna is fabricated and tested to validate the simulated results. A wide relative impedance bandwidth of 33% (8.25–11.55 GHz) and the axial ratio bandwidth of 8.55–9.70 GHz (12.60%) is exhibited. The broadside radiation characteristics are achieved with peak gain of 8.05dBic at 9 GHz. The overall size of the antenna structure is 0.8λ0 × 0.8λ0. The proposed antenna is suitable for various satellite applications.

Highly compact UWB-MIMO antenna with sharp multi-stop band characteristics

With multi-band rejection characteristics, a new low-profile antenna of size 34 × 34 mm2 is conferred in this article. It consists of quad identical monopole elements (originated orthogonally), contributing ultra-wideband characteristics in the system. The single unit of the proposed design consists of a modified spinning-top shape radiator (MSTSR), excited by a tapered microstrip line feed (TMLF) and semi-circular ground. An excellent bandwidth of 3–12.9 GHz (where S11 < − 10 dB) is obtained at each port. By inserting the structure of four spiral coils, a sharp notch ranging from 7.9 to 8.5 GHz is achieved to filter the X-band satellite communication uplink. In addition, a circular spiral slot in the radiator near the ground plane creates a stop band at 7.35–7.565 GHz band (satellite communication downlink band). Furthermore, symmetrical rectangular trapezoid resonators and inverted symmetrical rectangular trapezoid structures near the feed line are responsible for the elimination of interferences at 5.5 GHz lower WLAN and 3.5 GHz WiMAX respectively. The FR-4 substrate used for the UWB-MIMO design fabrication process and fabricated results are found in good match with the simulated results. Also, the design provides good performance metrics such as total active reflection coefficient, diversity gain, channel capacity loss, isolation, and envelope correlation coefficient.

Design and Experimental Study of a Drilling Tool for Mars Rock Sampling

Martian rocks contain crucial information about the genesis of Mars and the historical evolution of Martian climate change. Consequently, extracting and examining Martian rocks are pivotal in advancing our comprehensive understanding of the red planet. However, the current core drill string is prone to wear and tear, and the samples are susceptible to thermal denaturation. To address these challenges, we introduce two novel types of drill bits, the conical straight junk slot and the conical spiral junk slot, both employing impregnated diamond as the primary material. Comparative experiments were meticulously conducted to evaluate the influence of different junk configurations on drilling parameters, including speed, abrasion resistance, drilling force loading, and sample temperature rise. The findings unequivocally demonstrate the superior performance of the spiral junk slot. Furthermore, simulations were performed to examine the drilling process on basalt using a fixed configuration drill bit, validating the occurrence of the sample temperature rise. The research presented in this paper offers valuable programmatic references and essential data support for future Martian rock coring drilling missions.

3D printed circularly polarized implantable antenna with wideband impedance matching

Abstract This article proposes a slot-loaded circularly polarized implantable antenna with wide bandwidth at 2.45 GHz, i.e., Industrial, Scientific, and Medical (ISM) band. This antenna is established with a compact size of 44.52 mm3 based on 3D printing technology, and biocompatible material MED610 is adopted for human safety consideration. During the design, unilaterally shorted patch antenna loaded with T-slot is adopted, obtaining two closely spaced orthogonal modes with miniaturized antenna size. More importantly, to obtain wide impedance matching, a spiral slot is introduced around the feed, forming an L-section network consisted of a parallel capacitor and a series inductor. As a result, a wide circular polarization bandwidth of 28.7 % is realized for the proposed antenna. The measured results are well agreed with simulated results.

X-Band Tile-Based Metal-Only Reconstructible Reflectarray With 3-D Printing Support

A tiled-based metal-only reflectarray (RA) using stainless steel unit cells (UCs) is proposed in this letter. The RA aims at providing a low-cost high-gain antenna solution with the agility for customers living in harsh environments such as in the wilderness or under military threatening. The metal-only UCs, each fabricated separately using the laser cutting process with a prescribed reflection phase, are treated as mosaic tiles on a panel supported with a low-loss 3-D printing frame. The reflection phase, and hence the main beam direction, of the RA can be re-constructible according to the arrangement of the UCs. For the proof of concept, an RA with a diameter of 16 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , consisting of 820 UCs, is demonstrated at X-band. The UC comprises four spiral slots whose lengths control the reflection phase. The focal-to-diameter radio is 0.625. By re-arranging the UCs on the panel similar to a jigsaw puzzle, four application scenarios are experimentally verified. The first case has the main beam point to the broadside direction (0°). The other two have an oblique beam of 30° or 45° from the zenith; the final case consists of two main beams pointing to broadside (0°) and 30° from the zenith simultaneously. In the broadside case, a peak gain of 29.1 dBi and an aperture efficiency of 35.7% are achieved at 10 GHz, while the 3-dB gain bandwidth is 10.1%. A comparison table is summarized to manifest the uniqueness of the proposed idea.

A spiral slotted transducer with high longitudinal-torsional conversion rate

The longitudinal-torsional (L-T) composite piezoelectric transducer has wide applications in material processing, welding, and other fields due to its exceptional machining efficiency. This study introduces a spiral slotted L-T transducer, which is designed to achieve a high L-T conversion rate at low operating frequency. The equivalent spring concept is employed to derive the equivalent circuit of the L-T transducer, which provides a convenient study for the frequency characteristics of the transducer. A finite element model is developed to analyze the performance of the transducer and investigate the effect of the spiral slot parameters on the resonance frequency, amplitude, and the L-T conversion rate of it. Two prototype transducers are constructed and measured experimentally. Theoretical computation results, finite element simulation results, and experimental results are compared to each other. The comparison results demonstrate that the proposed computation model provides accurate prediction of the L-T coupling resonance frequency of the transducer. By adjusting the spiral slot parameters of the transducer, a higher L-T conversion rate can be achieved, which may have more applications in practical engineering.

Gain and bandwidth enhancement of low‐profile unidirectional radiation spiral slot antenna

AbstractA novel simple antenna based on substrate integrated coaxial‐like waveguide (SICW) is presented to enhance the gain and bandwidth of circularly polarized (CP) antenna with unidirectional radiation. The stepped inner metal strip is introduced in SICW, which results in a stronger radiation gain and wider axial ratio bandwidth. In addition, unlike traditional spiral antennas, the slot spiral antenna can be directly fed by a coaxial line at the inner port of the waveguide. As SICW can make the antenna directly realize unidirectional radiation, the extra reflector is not needed, and the antenna has a low profile of ( is the free space wavelength at the lowest frequency). The simulation and measurement results show that by using SICW with a stepped inner metal strip, the overlapping bandwidth of CP antenna can be increased significantly from 57.3% (2.7–4.85 GHz) to 71.6% (2.6–5.5 GHz) and the boresight gain of the antenna is improved 2 dBi over the entire frequency band.

A novel UWB flexible antenna with dual notch bands for wearable biomedical devices.

This study presents a novel UWB flexible antenna with dual band-notched design for wearable biomedical devices. The proposed antenna is designed on Kapton Polyimide-based flexible substrate. This includes a CPW fed circular and triangle structure. The dual notched bands are realized by using two triangular-shaped spiral slots defected ground structures. The first notched band (2.4-3.7GHz) is generated for rejecting WLAN and WiMAX, the second notch (5.15-5.725GHz) is generated for rejecting HyperLAN/2. The designed UWB antenna has approximately a bandwith of 159% (2.05-14GHz) in simulation. Thus, the designed UWB antenna meets FCC standards. The antenna has an omnidirectional radiation pattern with a maximum gain of 12.7dB in 8.4GHz. The proposed antenna is fabricated with the low-cost airbrush printed technique. In this technique, a higher gain value is obtained by controlling the thickness of the conductive layer. Effect of flexibility on the antenna performance is tested for different configurations in the simulation and anechoic chamber environments. According to the results obtained, the overall performance is not affected except for the shift in frequency. Since the antenna has a UWB structure, the frequency shift that occurs in bending is at a tolerable level. The proposed UWB antenna is suitable for wearable biomedical devices, with a high UWB performance.

Shear Strength Analysis of Anti-Rust Bolts with a Spiral Oil-Guiding Slot and Oil-Bearing Hole: Simulation and Experiment

This paper studies the shear strength of an anti-rust bolt with a spiral oil-guiding slot and oil-bearing hole by conducting a simulation and experiment. A finite element model with the bolt and the clamp tool is developed for simulating the shearing of the bolt in progressive failure analyses. An indirect method is proposed to generate a spiral entity that can produce excellent spiral elements. A clamp tool is designed for the shear experiment of the bolt. Moreover, a substitute calculation method is presented for the shear strength analysis of the special bolt, and the effect of using the oil-guiding slot on shear strengths is considered by reducing the bolt’s radius. The study results show the following: The results of the simulation are in good agreement with the experimental results. One side of the bolt with the oil-bearing hole is first cut off, and the deviation between the result obtained by using the substitute calculation and the experiment’s result is 7.97%.

Miniaturized Multilayer Surface-Mountable 5G Filter Based on Shielded Spiral Resonator

This brief presents a miniaturized bandpass filter (BPF) based on the shielded Archimedes spiral resonators using the multilayer printed circuit board (PCB) technology. The spiral resonators are incorporated inside a substrate integrated waveguide cavity, resulting in miniaturization by introducing additional coil-to-ground capacitance, and the enhancement of electromagnetic compatibility (EMC) due to the enclosed metal cavity. Detailed theoretical derivation for the resonator is presented to prove its miniaturized effect. A miniaturized 4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> -order BPF for 5G N78 application is developed with the proposed resonators. Compactness is further realized by the multilayer geometrical arrangement, consisting of two types of inter-stage coupling. One is the horizontal edge coupling and the other is the vertical space coupling through the spiral slot. Transmission zeros (TZs) are generated on each side of the passband by source-to-load coupling. The proposed filter is featured with an extremely small volume, low loss, together with good surface-mountable characteristic.

High capacity chipless RFID tags for biomass tracking application

AbstractThe design of a low-cost, flexible, miniaturized, and a high code density chipless radio-frequency identification (RFID) tag is presented as a solution for tracking the transportation of biomass fuel pellets. The performance of the tag is presented and demonstrates the applicability of the design for different material systems, while maintaining a compact size of 5.06 cm2. The tag consists of nested concentric hexagonal elements and a central spiral resonator suitable for ID encoding. The tag presented demonstrates code density of 3.6-bits/cm2, possesses angular stability up to 60°, and high radar cross section (RCS). The tag performance was also observed for tracking 5 kg of fly-ash biomass. Additionally, as the tag mass mostly consists of FR4, PET, or Taconic TLX-0 with a minute mass of either copper, gold, or silver, the tag can be easily combusted and disposed of during biomass combustion. The novel features of this tag are the combination of hexagonal and spiral shape slots for maximum space utilization thereby achieving high RCS signatures along with high code density. All these properties of the proposed chipless RFID tag provide a pioneering pathway for a real-time biomass tracking application.

A novel dual-port dual-layer planar spiral slot multiband antenna

In order to realize a dual-port multiband antenna, a novel planar spiral slot antenna is proposed and analyzed. The antenna adopts a dual-layer substrate structure. A spiral slot is etched on its bottom metal surface with a ring gap beside the slot to improve the isolation and lower the frequency. An elliptical metal ring radiation unit in the middle surface of the antenna plays the role of radiating and impedance matching. Two mutually perpendicular microstrips on the upper surface are used for feeding the radiation unit. The simulation and test results show that two ports of the antenna can work at multiple frequencies with the same radiator, and the isolation is more than 13.5 dB in the working bands (1.86-1.99 GHz, 2.47-2.5 GHz, 2.57-2.64 GHz, 2.90-5.7 GHz and 6.35-9.66 GHz). The antenna has the advantages of high gain, small volume, quasi omnidirectional radiation, and so on.

Compact High-Isolated MIMO Antenna Module With Chip Capacitive Decoupler for 5G Mobile Terminals

In this letter, a compact high-isolated multiple-input–multiple-output (MIMO) antenna module based on a chip capacitive decoupler is proposed for the fifth-generation (5G) smartphones. The antenna module consists of two feeding ports, radiating metal strips, and a chip capacitive decoupler within a compact size of 16 × 6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . In this design, two L-shaped metal strips are used as distributed capacitors to compress the size of the module. Meanwhile, a chip capacitive decoupler is added to improve isolation between the two feeding ports, which is realized with an analysis of common and differential modes. In addition, spiral slots are used to adjust the isolation between the modules. A prototype MIMO antenna with four such dual-port antenna modules was tested in the 3.5 GHz band. The measured –6 dB bandwidths of the two ports are 310 MHz (3.42–3.73 GHz) and 360 MHz (3.33–3.69 GHz), respectively, and the isolation is 24 dB at 3.5 GHz. The measured efficiencies are 60.5% and 52.7% at 3.5 GHz. The compact MIMO antenna module with high-isolation property provides a hopeful solution for the 5G mobile terminals.

Archimedean Spiral Slotted Leaky-Wave Antenna

In this work, a novel leaky-wave antenna (LWA) with Archimedean spiral slots is proposed for realizing high radiation efficiency and stable gain performance in both frequency-controlled and fixed-frequency beam-scanning applications. The structural feature of the proposed Archimedean spiral slot privileges LWA with properties of easy impedance matching and high leakage rate, because it avoids the strong reflection from large-size slots that commonly used in LWA design for high leakage rate. The bandwidths of the final designed Ka-band LWA defined by radiation efficiency larger than 90% and 80% are 13% and 25%, respectively, while the bandwidth defined by return loss less than −10 dB is 29%. And the gain fluctuations between different scanned beams are less than 2.4 dBi in the whole broadband. The LWA is further applied in designing a new-type antenna with double-layer substrate-integrated waveguide (SIW) structures, which has four feeding ports at the ends and a coupling plane in the middle interface and can realize the fixed-frequency beam switching between directions of −46°, −36°, 34°, and 45° at 28 GHz through changing the excitation port. The proposed LWAs are potential candidates for applying in future millimeter wave communication systems where multifunction integrated and multifrequency adaptive antennas are required.

Circularly Polarized Leaky-Wave Antenna With Natural Curl Property

This letter proposes a novel leaky-wave antenna (LWA) based on low profile substrate integrated waveguide (SIW), which can operate in either left-handed circular-polarization (LHCP) or right-handed circular-polarization (RHCP) mode. Different from other kinds of literature, the proposed SIW LWA is capable of CP state switching without introducing multiple LWA elements, phase-correct couplers or polarization converter, which is a single LWA element with a simple coaxial feeding/matching structure. Specially, the periodic slots on its radiation aperture are Archimedean spiral slots which are curved slots with curl property. These curled slots can excite vortex fields in the waveguide channel of SIW, and the generated vortex field is capable of changing vortex direction by selectively exciting the port of LWA, making the CP features flexible. The final Archimedean spiral slotted SIW LWA realizes LHCP or RHCP (AR < 3 dB) in the wide CP band of 27.7–34.6 GHz (BW = 22%), and the LHCP scanning range is from −51° to −10° while the RHCP beam scans from 10° to 50°.

High-Efficiency Plasmonic Lens Based on Archimedes-Spiral with Cross Section of an Asymmetric Slot

A high-efficiency plasmonic lens composed of a single Archimedes-spiral slot with a cross section of an asymmetric slot is proposed. By adding an auxiliary nanocavity under the primary spiral slot, unidirectional plasmonic waves can be efficiently transmitted in the inward direction and focused on a hot spot in the center. Due to the asymmetric slot, the finite-difference time-domain (FDTD) method is used to numerically optimize the geometric parameters of the single spiral slot, which can achieve high-intensity unidirectional inward focusing. The proposed structure can decrease background noises and prevent cross-talk of nearby components in optical networks, which significantly improves the integration level of nanophotonic circuits and devices.

Spoof surface plasmon polaritons characteristics of band‐stop slot resonators

AbstractBy periodically patterning the conductor surface, the so‐called spoof surface plasmon polaritons (SSPPs) in microwave band can be transmitted and SSPP mode devices with the cutoff frequency at high frequency end can be constructed. In this paper, the spiral slots are loaded in the edge and the feed port of a printed monopole antenna element and two rejection bands are achieved. The results indicate that in the intuitive physical sense, the slot‐typed band‐stop resonator in antenna structure actually works according to the SSPP mode mechanism. Furthermore, it is proposed that its structure size should be determined according to the principle that the slot resonant frequency is a bit lower than the asymptotic frequency of SSPP modes.

Analysis of Archimedean Spiral Slot Antennas in Infinite Ground Planes Using the Theory of Characteristic Modes

The analysis of Archimedean spiral slots using the theory of characteristic modes is presented in this article. Purely magnetic characteristic modes are used to study the behavior of a spiral slot etched in an infinite ground plane. The effect of the spiral geometry parameters (slot width, separation between spiral slot arms, number of spiral turns, and inner spiral spacing) on the characteristic modes are investigated using the theory of characteristic modes. Based on the results of the characteristic mode analysis, guidelines are presented for selecting the appropriate slot dimensions for realizing a compact spiral slot assembly (miniaturization), multimode behavior and for improving the bandwidth of the purely magnetic characteristic modes. Additionally, analytical equations are presented for accurately predicting the resonant frequencies of the purely magnetic characteristic mode of the spiral slot antenna.

Experimental and Numerical Study on Air Flow Behavior for a Novel Retractable Reverse Circulation Drill Bit of Casing-while-Drilling (CwD)

A reverse circulation Down-The-Hole (DTH) hammer drill bit in Casing-while-Drilling (CwD) processes is designed and applied to drilling under complicated formation. The drill bit is a special retractable drill bit with an exclusive reverse circulation gas channel. Using numerical simulations and experiments, the influence of the gas channel structure parameters of the drill bit, including the inner jet nozzles, flushing nozzles, suction channel, and other parameters, on its reverse circulation performance is analyzed, and the optimal gas channel structure parameters of the drill bit are determined to improve the reverse circulation effect. The results show that the flushing nozzles and inner jet nozzles have an important influence on entrainment performance. The entrainment rate η decreases as the flushing nozzle diameter increases and decreases as the inner jet nozzle diameter increases. An increase in the suction channel diameter can improve the reverse circulation effect of the drill bit. The spiral slot drill bit is more conducive to air being sucked into the central channel in the form of spiral flow, so it can improve the entrainment performance. The entrainment rate η can reach 23.4% with the optimum structured drill bit.