Slot Line Research Articles

Miniaturization of substrate integrated waveguide filters using novel compact metamaterial unit-cells based on SIR technique

In this paper, three novel compact metamaterial unit-cells are proposed. The proposed unit-cells are based on the concept of the stepped-impedance resonator (SIR) technique which are used to miniaturize the physical size of the conventional complementary split ring resonators (CSRRs). The proposed metamaterial unit-cells consists of two modified rings so that in these unit-cells, the slot lines in the conventional CSRRs are replaced by the stepped-impedance slot lines. The electrical size of the proposed unit-cells called the SIR-CSRR are larger than the conventional CSRR. To investigate the performance of the proposed SIR-CSRR unit-cells in the size reduction, three substrate integrated waveguide filters loaded by SIR-CSRR unit-cells with different configurations are designed. By loading the SIR-CSRRs on the surface of the waveguide, an additional forward-wave passband propagating below the initial cut-off frequency of the waveguide is produced. Consequently, by using the proposed SIR-CSRR unit-cells instead of the conventional CSRRs, miniaturization with arbitrary ratio are achieved. In order to validate the proposed miniaturization technique, the designed filters are fabricated and measurement results are provided. Good agreement between simulation and measurement results are achieved.

Radiation from a two-dimensional array of coupled slot lines

The problem of radiation of the eigenmodes of an infinite 2D array of semi-infinite coupled slot lines is solved. An analytical solution for the electric field on conductors is found by the Wiener–Hopf method in the approximation of narrow conductors forming the slot lines. An algorithm of numerical implementation of this solution is developed. Expressions for elements of the scattering matrix of an infinite array are found. Dependences of the elements of the scattering matrix on frequency and the structure parameters are studied numerically.

Bandwidth enhancement of monopole antenna with DGS for SHF and reconfigurable structure for WiMAX, WLAN and C-band applications

In this study a reconfigurable antenna for WiMAX, WLAN, C-bands and SHF applications has been presented. The main body of antenna includes rectangular and L-shaped slotted ground plane and a rectangular patch with slotted feed line, for impedance bandwidth enhancement. In the proposed antenna, a PIN diode is used to adjust the frequency band to SHF, WiMAX, WLAN and C-bands applications. When PIN diode is forward-biased, the antenna covers the 3.5–31 GHz frequency range (i.e. a 160% bandwidth) and when the PIN diode is in its off-state, it operates between 3.4–5.8 GHz. The designed antenna, with a very small size of 12 × 18 × 1.6 mm3, has been fabricated and tested. The radiation pattern is approximately omnidirectional. Simulations and experimental results are in a good agreement with each other and suggest good performance for the presented antenna.

Circularly‐polarised slot array with high front‐to‐back ratio and low axial ratio

A novel design for circularly-polarised (CP) arrays is proposed. The proposed array is composed of dual CP slot antenna elements arranged in a face-to-face configuration, and they are simultaneously excited through a slot line. By properly controlling the excitation amplitudes and phases of the two radiating elements, the cross polarisation and back radiation of the array can be effectively reduced. From the measured results, the proposed array can give an axial ratio of lower than 1 dB and a front-to-back ratio of higher than 12 dB within a 10 dB-return-loss bandwidth of >16%. Simulation results obtained with high frequency structure simulator (HFSS) also agree well with the experimental data.

Low windage resistance frequency‐selective rasorber based on windmill‐shape coupling line arrays

In this Letter, the authors report on the analysis, design, fabrication and measurement of a low windage resistance frequency selective rasorber (FSR) based on windmill-shape coupling slot line arrays. A lossy structure is added to the traditional frequency selective surface structure to make up a FSR with the characteristics of small insertion loss within the passband and weak reflection at frequencies below and above the passband meanwhile. In addition, the hollow structure can reduce windage resistance effectively. The measurements show that an insertion loss of 1.01 dB can be obtained at 7.71 GHz, while both lower and upper passband edges have at least 10 dB reflection reduction under the normal incidence. Both simulation and experiment results exhibit that the proposed FSR is insensitive to both transverse-electric (TE) and transverse-magnetic (TM) polarisation. The proposed FSR can be applied in the field of radome, cloaking and other microwave applications.

Eigenmodes of a 2D array of coupled slot lines in the impedance approximation

A 2D periodic array of coupled slot transmission lines is considered in the approximation of equivalent boundary conditions. The eigenmode problem for an array operating in the quasi-periodic mode is formulated and solved. The dispersion equation for eigenmode propagation constants and expressions for eigenmode fields are obtained. The behavior of eigenmodes in a frequency band and in a range of values of geometric parameters is analyzed. The orthogonality of eigenmodes is shown. Theoretical results are compared to the results of numerical calculation performed with the use of electromagnetic simulation systems.

A Miniaturized 878 MHz Slotted Meander Line Monopole Antenna

<p>A slotted meander line printed monopole antenna for low frequency applications at 878 MHz is presented. The operating frequency of the conventional printed monopole antenna was greatly reduced by the presence of the slots and meander line which lead to the reduction of the antenna size. The size reduction up to 70% compared to the conventional reference antenna is achieved in this study. The antenna has a simple structure and small antenna size of 46.8 mm x 74 mm or 0.137𝝀<sub>0</sub> x 0.217𝝀<sub>0</sub>. The antenna has been fabricated on the low-cost FR4 substrate and measured to validate the simulation performances. Measured results display that the proposed antenna produces omnidirectional radiation pattern of impedance bandwidth of 48.83 MHz and the maximum gain of -1.18 dBi.</p>

Curved convex slot: an effective needleless electrospinning spinneret

Slot electrospinning that uses narrow slot as a spinneret combines the advantages of both needle and needleless electrospinning with precisely controlled solution condition. Most of the existing slot electrospinning techniques, however, use a straight linear slot as spinneret. The effects of slot geometry on electrospinning process and fiber morphology have not been reported in the research literature. In this study, four convex slots with different line shapes, i.e., curved, straight, rectangle and triangle, have been used as spinnerets to examine the effects of slot line shape on electrospinning process, fiber morphology and productivity. The electric field intensity distribution of these slot spinnerets was analyzed by finite element method. Our experimental results have indicated that the slot line shape played an important role in affecting fiber diameter, productivity and uniformity of the fibrous membranes. Compared to the other slots studied, the curved slot can produce nanofibers with larger productivity and the resulting fibrous membranes were more uniform as well; the curved slot had higher electric field with more uniform distribution of electric field intensity along the slot length direction. These understandings may be helpful for designing new slot electrospinning systems.

Curved coupled‐line resonators for microwave filter applications

AbstractPlanar resonant structures made of curved coupled microstrip and slot lines and their application for microwave filtering are presented. The prominent feature of the proposed resonators is their wide bandwidth. It is demonstrated that such resonators are useful for microwave band‐reject and low‐pass filtering applications. The proposed structures were compared with split‐ring resonators (SRRs) and complementary split‐ring resonators (CSRRs). The size of the filters made with the proposed resonators was similar to those made with SRR and CSRR; however, their bandwidths were larger. Prototypes were fabricated and tested.

Novel Four-Way Slotted-Substrate Integrated Waveguide Power Divider Using Identical Coupling Circuits

ABSTRACTA novel four-way X-band slotted-substrate integrated waveguide (SIW) power divider using an identical slot-coupling structure has been proposed in this article. The proposed power divider was realized by using an identical transition between a resonant slotted SIW and output microstrip lines, and four identical rectangular coupling slots were employed to achieve good impedance matching and equal signal transmission. The proposed power divider is designed, fabricated, and measured. The measured results show a reasonable agreement with the simulated ones and the advantages of its low profile, efficient heat sinking, as well as its potential for high power-combining efficiency.

Broadband SIW-to-Waveguide Transition in Multilayer LCP Substrates at W-Band

In this letter, we present a substrate-integrated waveguide (SIW) to air-filled rectangular waveguide (WG) transition in multilayer liquid crystal polymer substrates at W-band. The proposed transition is achieved by using a SIW-fed linearly flared antipodal slot line inserted into a WG. To minimize packaging leakage, no guided vias are utilized in the slot line region. Full-wave simulation reveals a low insertion loss of 0.8 dB for the proposed transition at W-band. To experimentally demonstrate this design, a WG-to-SIW-to-WG transition was fabricated and characterized. The measured insertion and reflection loss of the back-to-back transition is less than 1.8 and −11 dB, respectively, at W-band.

Dynamic Conductivity and Two-Dimensional Plasmons in Lateral CNT Networks

We study theoretically the carrier transport and the plasmonic phenomena in the gated structures with dense lateral carbon nanotube (CNT) networks (CNT “felt”) placed between the highly-conducting slot line electrodes. The CNT networks under consideration consist of a mixture of semiconducting and metallic CNTs. We find the dispersion relations for the two-dimensional plasmons, associated with the collective self-consisted motion of electrons in the individual CNTs, propagating along the electrodes as functions of the net electron density (gate voltage), relative fraction of the semiconducting and metallic CNTs, and the spacing between the electrodes. In a wide range of parameters, the characteristic plasmonic frequencies can fall in the terahertz (THz) range. The structures with lateral CNT networks can used in different THz devices.

Modeling of magnetoelectric microwave devices

The possibility of computer modeling implementation of electrically controlled magnetoelectric (ME) microwave devices is considered. The computer modeling results of different structures of ME microwave devices based on layered ferrite-piezoelectric structure formed on the slot line, microstrip line and coplanar waveguide are offered. Results are reported as frequency dependencies of insertion losses of ME devices.

In brief

PAGE 40 A methane-hydrogen dry etching technique has been used to fabricate GaSb-based cascade diode lasers emitting near 3 µm. The process, developed by researchers in the USA, produces a diffraction-limited laser with minimal increase in threshold current density and no voltage penalty when compared with wide ridge multimode lasers. PAGE 36 A performance trade-off was found when examining different methods for inserting microstrip lines into aerospace composite structures. Research from Australia showed that embroidered microstrip lines exhibited better electromagnetic performance, whilst stencil transfer was more resistant to mechanical deformation. Cascade diode lasers fabricated using methane-hydrogen dry etching technique. PAGE 34 Researchers from the UK have designed an easy to control microstrip coupler that enhances power coupling between two microstrips. Two small slot lines are inserted in the ground plane underneath the microstrips, forcing an increased number of shared field lines between strips, thus eliminating the need to narrow the distance between microstrip lines. Microstrip lines stitched into HexPly 914 S-Glass. PAGE 7 A high-performing 3D terahertz (THz) filtering antenna was designed by researchers in China, using a low-temperature co-fired ceramic (LTCC) process. This 3D structure is more compact, has enhanced radiation performance and allows for more design flexibility compared with traditional planar designs. Slot lines underneath microstrips enhance coupling. PAGE 16 Researchers from Korea have developed a dual correlated double sampling scheme (CDS) for low-noise CMOS imagers, without the need for a power-consuming programmable gain amplifier (PGA). This scheme reduces noise by removing sampling error, and reduces power consumption by amplifying the readout channel's output. Photograph of 3D THz filtering antenna. The correlated double sampling scheme can be applied to SAR-based ADCs for CMOS imagers without the use of a PGA.

A Novel Beam-Switching Array Antenna Using Series-Fed Slots With PIN Diodes

A novel slot array is proposed for uses on femtocells of mobile services. The array contains multiple sets of equally spaced slots connected in series on a coplanar waveguide. A diode-loaded shorting strip is mounted across each slot to enable or disable radiation so that switchable beams of different tilting angles can be provided. The proposed design comes as a flat panel hanging on the wall. The beam direction of this base station antenna can be set to yield an appropriate coverage depending on user equipment locations. A two-state prototype was fabricated to demonstrate the feasibility of this approach. Measured down-tilt angles are 13° and 32°, respectively. The 3-dB beamwidths are approximately 25°. The proposed structure can be configured to achieve versatile performance features. A design of low sidelobe levels as well as a three-state design is devised. Discussions about slot excitation, line termination, and diode biasing circuitry are also provided.

Determination of Binder Content in Traditional Sandmixes by Microwave Method

This paper presents preliminary research on the possibility of determining the binder content in traditional sandmixes by the microwave method. The research included examinations of three kinds of bentonite. The presented measurements were carried-out with the use of a special stand – the so-called slot line. The concentration of the binder in molding sand was determined on the grounds of measurements of a parameter; i.e., absorbed power or output power of the electromagnetic wave. One of the main advantages of the suggested new method is the short time of the measurement.

Highly compact UWB bandpass filter based on composite right/left-handed transmission line and meander fractal like ring slot in ground

An ultra-wideband (UWB) highly compact bandpass filter with extremely high passband bandwidth is presented. The proposed structure is made using three-staged stepped-impedance lines and a composite right/left-handed transmission line (CRLH-TL) synthesized with meander fractal like ring slot in the ground and series capacitive gap in conductor strip. The capacitive gap in conductor strip and meander fractal like ring slot in the ground plane play major role for controlling the lower and higher cut-off frequencies. The equivalent circuit model of proposed filter is demonstrated and lumped parameters are extracted. A prototype is fabricated to experimentally validate the performance of proposed filter. The proposed UWB filter has extremely wide −10 dB return loss passband bandwidth from 3.14 to 18.26 GHz with relative bandwidth of 142% and insertion loss better than 0.5 dB. Also it achieves a wide upper-stopband from 19.7 to 24.4 GHz with insertion loss better than 13.0 dB, return loss <1.5 dB and sharpened rejection skirts outside the passband at both lower and upper frequency ends. Good agreement is found between simulated and measured results with measured group delay variation in the passband <0.65 ns.

Bandwidth reconfigurable antenna with a fixed lower and a variable upper limit

This paper presents a frequency bandwidth reconfigurable antenna capable of gradually varying its bandwidth from 43 to 76% by keeping the lower band limit fixed and varying the upper one. The antenna consists of a disc-monopole antenna with four vertical slot lines and a via-shorted slot ring incorporated in its ground-plane. To vary the bandwidth, the first slot line is used to create a new resonance below the operating band of the monopole, which is used as the fixed lower band limit. The next two slots are used to vary the upper limit while adjusting the middle resonance in order to maintain a good impedance-matching over the bandwidth. The fourth slot line and the shorted slot ring are used together to suppress high frequencies. In addition to this gradual bandwidth reconfiguration, the proposed antenna has the potential to offer several different modes of operation; however for concise reasons, only two other modes corresponding to a single-band and a dual-band narrowband, modes are presented here. To validate the proposed bandwidth reconfiguration approach, simulated and measured results are provided and a good agreement is achieved. The antenna is potentially suitable for applications needing to adjust the frequency bandwidth such as cognitive radios.

Research and Manufacture of Microwave Material Automatic Measurement System of Slotted Line

In this paper we designed a microwave material measurement system by using slotted line waveguide.Compared with the VNA,this system have the smaller size and lower cost.Considering the test technical specifications, test methods of complex permittivity of microwave materials, and the performance of test system,we used the short-circuited line method to test the complex permittivity of the microwave material, and used the TI DSP [1] (TMS320C6747) as a minimum core processor system. Developed a set of X-band automatic slotted line system, this paper carried out the design of the prototype test system and the programing of the system's automated testing software. Finally,we used the measuring system to test two kinds of sample(fiberglass and quartz) and compare the result with the other result testing by the VNA.it is not difficult to conclude the measured result is relatively accurate.

Effect of Sand Base Grade and Density of Moulding Sands with Sodium Silicate on Effectiveness of Absorbing Microwaves

Abstract In the paper, presented is a research on effectiveness of absorbing electromagnetic waves at frequency 2.45 GHz by unhardened moulding sands prepared of three kinds of high-silica base and a selected grade of sodium silicate. Measurements of power loss of microwave radiation (Pin) expressed by a total of absorbed power (Pabs), output power (Pout) and reflected power (Pref) were carried-out on a stand of semiautomatic microwave slot line. Values of microwave power loss in the rectangular waveguide filled with unhardened moulding sands served for determining effectiveness of microwave heating. Balance of microwave power loss is of technological and economical importance for manufacture of high-quality casting moulds and cores of various shapes and sizes. It was found that relative density influences parameters of power output and power reflected from samples of moulding sand placed in a waveguide. Absorption expressed by the parameter Pabs is not related to granularity of high-silica base: fine, medium and coarse. It was found that the semiautomatic microwave slot line supports evaluation of effectiveness of microwave absorption on the grounds of power loss measurements and enables statistic description of influence of relative density of the sandmix on penetration of electromagnetic waves in unhardened moulding sands.