3D printing of high performance low temperature sintered ceramic substrates for microwave applications
A novel method using the Invasive Weed Optimization to optimize the geometry of a collinear antenna array is presented. The goal of the optimization is to produce an antenna array geometry with a specified shape for its radiation pattern, so that reception across a designated service area is uniform. The antenna array is designed for FM radio or DVB-T TV broadcasting applications, however, this kind of optimization can be applied to other antenna.
Metamaterials represent a new paradigm in electromagnetic science and technology. They have already leaded to many unprecedented microwave applications, which may be classified in three categories: guided-wave, radiated-wave and refracted-wave applications. Radiated-wave applications cover several types of novel antennas and reflectors, which may be 1D or 2D, passive or active, and static or dynamically tuned. Progress in metamaterial technologies places challenging demands on material properties and therefore structured electromagnetic materials. The development of composite right / left-handed transmission lines (CRLH-TLs) has received considerable attention due to the unique propagation characteristics. The CRLH-TLs are the metamaterials with both of the RH and the LH properties. In this paper, study and design of smart frequency agility control system has been introduced and investigated. The proposed CRLH-TL has been evaluated using a commercial software. The final proposed system with smart control unit has been fabricated and the scattering characteristics have been illustrated using network analyzer to meet the multifunction operation requirements for communication and radar applications.
This paper presents a high-gain antenna for non-contact measurement systems around the frequency ~26GHz. The proposed antenna consists of a slot antenna on a metallic grooved structure with a single frequency selective surface. A small size and improved gain performance are the key objectives of this design. To achieve these two objectives, we use an optimization procedure based on a global algorithm. Both simulation and optimization are carried out by means of a full-wave electromagnetic simulation tool. Afterward, a prototype of the proposed antenna has been manufactured in order to verify their performances. More than 15dB of gain is obtained over the operating frequency range, with approximately 17dB at the frequency 25.5GHz. the small size and high-gain characteristics make this antenna very suitable for non-contact measurement, especially for short-range radar sensors.
Herein, a 3D 13, 56 MHz (HF) RFID reader antenna is proposed in order to optimize detection performance whatever the tag angular positioning. The design is made of a multi-loop structure, based on serial complementary antennas, as said “twisted” antennas. The RFID tag detection is optimized by two factors which rely on the modifications of the magnetic field (i) vectorial distribution and (ii) magnitude density. The reader antenna design is analyzed with electromagnetic simulation under HFSS (High Frequency Electromagnetic Field Simulation), and validated by detection measurements, in coplanar mode. A multi-loop structure, composed by 4 sub-loops, is then conformed onto a tube surface to provide the 3D structure. The goal of this improvement is to provide tag detection for any angular positions. At the center of the tube (3D reader structure), the detection of the tag is performed whatever its angular orientation, that is to say for any radial orientation.
A cylindrical dielectric resonator antenna (DRA) excited by a rectangular waveguide with tapered section is presented in this paper. By introducing a tapered section of waveguide between the rectangular waveguide and square ground plane, the coupling to a low permittivity DRA can be improved substantially. Moreover, it offers a 10 dB bandwidth of 6.34% and a maximum gain of 6 dBi. Symmetrical broadside radiation patterns with low levels of cross polarization are maintained in both the planes. The proposed antenna is very much suitable for millimeter wave applications due to the very low losses of waveguide and DRA.
A novel shaped horn antenna is proposed to improve the spot focusing and imaging systems performance at terahertz frequencies. In this paper, a waveguide-horn-waveguide structure scheme is used to model a horn antenna in order to avoid lens corrected on horn apertures usually needed to enhance the focusing. The shaped horn and lens corrected horn are compared for performance comparison at 0.92, 0.94, 0.98 and 1THz keeping horn aperture diameter 1.7mm and length 3.1mm for both type of horn antennas. The horn antennas are designed and simulated with an accurate proprietary Body-of-revolution Finite-Element code and fed by circular waveguide operating at TE11 mode. Comparison study highlighted that, the shaped horn provided slightly better spot focusing of 0.16, 0.15, 0.08 and 0.09mm as compared to lens corrected horn. The proposed shaped horn is found suitable candidate for frequency domain near field focusing in terahertz imaging systems.
A novel procedure for automated simulation-driven tuning of circularly polarized (CP) microstrip patch antennas (MPA) for improved axial ratio (AR) is presented. Our approach specifically addresses the CP MPAs exited through dual inputs which are driven by branchline couplers of unequal power splits. Our procedure allows for the improvement of AR over the required range of operating frequencies. The procedure, implemented in a part with numerical optimization, is governed by a closed form formulas computing an appropriate unequal amplitude excitation of the MPA of interest. The required excitations are implemented with microstrip branchline couplers. Numerical optimization addresses the effect of coupling (through the feed) of the entire MPA-feed circuit. In this paper, the approach is illustrated with a numerical example of a probe-fed MPA. Moreover, our methodology has also been demonstrated to work for MPAs with open-end microstrip inputs. Numerical validation is carried out using full-wave simulations of the entire MPA-feed circuits.
Design of non-Foster matching networks for monopole and loop printed antennas operating much lower their resonance frequencies are presented. Both matching networks consist of a non-Foster element (negative capacitance or negative inductance) to compensate partly the antenna reactance and a lumped-element transformer to convert the real part of the antenna impedance to 50 Ohm. The non-Foster elements are realized as transistor-based negative impedance converters. Advantages in the antenna matching bandwidth over conventional matching networks are demonstrated. Operational bandwidth of the transformer is shown to be one the main factors limiting the antenna matching bandwidth when using the non Foster matching networks under consideration.
The paper describes a method of inkjet-printing a Co-Planar Waveguide (CPW)-fed flexible antenna for the development of a wearable microwave imaging (MWI) device for cancer detection and monitoring. The single side of a monopole antenna is represented as a fractal pattern with customized slots. The antenna is inkjet-printed using a low-cost additive fabrication method on a flexible substrate such as Kapton using Dimatix materials printer. Simulation using CST Microwave Studio and measurement carried out on an inkjet printed antenna with a VNA confirm that the designed antenna bandwidth ranges from 2.5GHz to 6.5GHz making it suitable for Microwave imaging applications.
This paper presents recent developmental work on a low-profile ultra-wideband disk-loaded monopole. A novel single port feed configuration is investigated were the RF power is split and circulated by a branched transmission line network. This is composed of a balanced stripline and capacitive coupling network which both excite a metallic disk radiator. Measurements and computations show that the impedance bandwidth and input match can be enhanced using this matching approach. The configuration provides an impedance match VSWR of 3.4:1 over a 10:1 frequency bandwidth with a single lobed pattern bandwidth of 4:1.
In this paper, an optimization-based procedure for performance comparison of alternative compact UWB antenna topologies is discussed. Our approach allows for fast assessment of compact antenna performance by identifying the best possible trade-offs between the antenna size and its reflection responses. Analysis of such Pareto-optimal designs obtained for various antenna topologies allows for their fair comparison, particularly in terms of the minimum size they can be designed for (assuming acceptable reflection response levels) or the best attainable reflection characteristics. The multi-objective optimization algorithm utilized in this work exploits sequential domain patching technique and variable-fidelity EM simulation models. The proposed approach is demonstrated using two topologies of compact UWB monopole antennas.
A wideband, singly fed, circularly polarized, elliptical dielectric resonator antenna has been designed using a conformal open loop antenna in conjunction with a concentric parasitic open loop. A wideband 3dB axial ratio has been achieved over a bandwidth of ~12% with an impedance matching bandwidth of ~23% over the same frequency bandwidth.
This paper presents the concept of substrate integrated waveguide (SIW) technology along with superstrate layer, which is used to design a high gain antenna for 79 GHz automotive short range radar (SRR) applications. The maximum gain of a single antenna with superstrate layer is 14.6 dBi at 79 GHz, which is higher than the gain of a classical 2 × 2 array. It is found that the gain of a single superstrate layer increases nearly 8.78 dB at 79 GHz over its SIW base antenna. The CST simulated 2:1 VSWR bandwidth with superstrate layer is from 75.9 GHz to 81 GHz (6.46 %). The antenna patterns are found to be broadside all over the frequency band of interest. Also the results are verified using another simulation software HFSS.
The stringent constraint in any wireless communication system is the wireless channel itself. The indoor radio channel in an industrial environment exhibits a lot of multipath due to the prevalent metallic structures. In this research, an indoor radio channel is investigated in a severe multipath engine test bed environment. The study of this channel is undertaken for the applicability of a cost-efficient passive ultra high frequency radio frequency identification system capable of performing two dimensional localization of tagged objects in an engine test bed facility.The channel transfer functions were measured using a vector network analyzer. Vital channel characteristics investigated in this paper are the power delay profiles, the root mean square (RMS) delay and the power-ratio between the line of sight (LoS) and non-line of sight (NLoS) paths. The maximum RMS delay experienced is 47.1 ns and a minimum of 8.6 ns. The power-ratio values are appreciable for the majority of the LoS positions, but not satisfactory for the NLoS positions. Using this information, it will be helpful in analyzing the localization performance of a measurement-based system simulator or of a prospective hardware setup, in an engine test bed environment.
Low Temperature Co-fired Ceramics (LTCC) is deployed in this paper as a dielectric material for design of a directive Dielectric Resonator Antenna (DRA). The antenna accomplishes its enhanced directivity by higher order modes excitation in relatively narrow frequency band. By using slot in Substrate Integrated Waveguide (SIW) for feeding the resonator, the back radiation is significantly reduced as compared to microstrip feed line. The antenna produces broadside radiation pattern with linear polarization and radiation efficiency of about 87 %. The desired center frequency of the antenna is 25.5 GHz; however due to manufacturing tolerances, the resonant frequency of the fabricated antenna is shifted to 25.8 GHz.
In this paper a design of linearly and circularly polarised Bull's Eye antenna is presented. The proposed antenna consists of two identical rectangular slots in a shape of cross surrounded by symmetric periodic grooves drilled in the surface of metallic plate. The antenna can operate on vertical, horizontal and circular polarisation over its entire bandwidth. It resonates at 14.8 GHz and it has a simulated impedance bandwidth of 11% with achieved gain and side lobe level of 17.8 dBi and 15 dB, respectively.
This paper presents novel designs, analyses, and simulations of two miniaturised pyramidal double-ridged horn (PDRH) microwave antennas for medical imaging systems. The PDRH antennas have been optimised to operate within a ceramic material filling with permittivity of 41 (which approximately is the permittivity of the human skin in the intended frequency range), in order to make the compact antennas, and also to minimise the first bulky reflection due to the large contrast of the pulse from the free-space to the human skin surface, which cause the difficulty to process the overall reflected pulse. The proposed antennas can operate in conjunction with each other to cover the whole radio frequency (RF) range of 1.25 to 2.47 GHz, where the high-gain and directivity for medical imaging systems are the main factors. Both RF antennas have the bandwidth larger than 500-MHz that would qualify them as ultra-wideband (UWB) antennas. The optimised designed microwave antennas are numerically verified based on the electromagnetic (EM) method of finite integration technique (FIT), using the CST Microwave Studio (CST-MWS) software.
