A folded loop antenna with four resonant modes

A multimode loop antenna with compact volume for mobile applications is presented in this paper. The loop antenna consists of a loop strip with a length of about 0.5λ. The loop strip is meandered to save space and bent to generate three traditional resonant modes, the 0.5-λ, 1-λ and 1.5-λ modes, and an additional higher mode, the 2-λ mode. The additional 2-λ mode is generated by adjusting the distance between the feed point and shorting point of the loop strip. The 1-λ, 1.5-λ and 2-λ modes together form an upper band with a wide bandwidth of 1.71-2.69 GHz to cover the DCS1800, PCS1900, UMTS2100, LTE2300 and LTE2500 systems. By using a matching network at the loop input, the lower band generated by the 0.5-λ mode has a bandwidth of 0.76-1.09 GHz to cover the GSM850 and GSM900 systems.postprin

Single Feed Square Aperture Circular Polarized Antenna

In recent years, circular polarized antennas become more important in wireless communication systems because of the ability of radiating circular polarized wave. In this paper, the design of single-feed square-aperture antenna with and without reflector towards the circular polarized antenna performance is presented. The antenna made of square ground plane, square-aperture and a probing strip feed by using microstrip transmission line. The design has achieved a target axial ratio, which is less than 3 dB at frequency range of 4 GHz to 6.5 GHz. When a square ground plane reflector is integrated on the CP antenna for the unidirectional pattern, the presented antenna enhanced gain about 8 dB

A Novel Dual Ultrawideband CPW-Fed Printed Antenna for Internet of Things (IoT) Applications

This paper presents a dual-band coplanar waveguide (CPW) fed printed antenna with rectangular shape design blocks having ultrawideband characteristics, proposed and implemented on an FR4 substrate. The size of the proposed antenna is just 25 mm × 35 mm. A novel rounded corners technique is used to enhance not only the impedance bandwidth but also the gain of the antenna. The proposed antenna design covers two ultrawide bands which include 1.1–2.7 GHz and 3.15–3.65 GHz, thus covering 2.4 GHz Bluetooth/Wi-Fi band and most of the bands of 3G, 4G, and a future expected 5G band, that is, 3.4–3.6 GHz. Being a very low-profile antenna makes it very suitable for the future 5G Internet of Things (IoT) portable applications. A step-by-step design process is carried out to obtain an optimized design for good impedance matching in the two bands. The current densities and the reflection coefficients at different stages of the design process are plotted and discussed to get a good insight into the final proposed antenna design. This antenna exhibits stable radiation patterns on both planes, having low cross polarization and low back lobes with a maximum gain of 8.9 dB. The measurements are found to be in good accordance with the simulated results

Multi mode Resonator based Concurrent Triple band Band pass Filter with Six Transmission Zeros for Defence Intelligent Transportation Systems Application

A compact and highly selective triple-band bandpass filter (BPF) is designed and presented in this paper. Proposed filter offers low insertion loss, and passband characteristics is achieved by using two coupled MMR multi-mode resonators (MMR1 and MMR2) and an inverted T and circular shape MMRs. The filter operates at frequency 2.43 GHz (Vehicular Communication), 5.91 GHz (ITS band), and 8.86 GHz (satellite communication band). The simulation and measurement results show a minimum insertion loss of 1.6 dB, 0.73 dB, and 2.8 dB for triple-band BPF. The return loss is found to be greater than 13.06 dB, 28.6 dB, and 21.55 dB. It is noted that measurement results are in accordance with the result of electromagnetic simulation. Desired triple-band multi-mode resonators (MMRs) filter characteristics are achieved with six transmission zeroes (TZs). The filter comprises of MMRs which provide small size and control over the spurious frequency. By using a parallel-coupled microstrip line, the first and third passbands are realised. Whereas by using an end-coupled microstrip line, the second passband is recognised. At the input and output ports, the resonator coupling technique is used. By using the anti-parallel microstrip line arrangement, the transmission zero is acquired. The dimensions of the designed filter are 25×16 mm 2

Design of a Wideband Dual-Feed Circularly Polarized Antenna for Different Axial Ratio Requirements

A novel method of designing a wideband dual-feed circularly polarized (CP) antenna is presented for different axial ratio (AR) requirements. The output characteristics of the feed network for the dual-feed CP antenna is first analyzed and illustrated that how to obtain the variance ranges of the output magnitude and phase of the feed network for a required AR. Based on the analysis, different branch-line couplers are used for achieving wide AR bandwidths of less than 3 dB, 2 dB, and 1 dB respectively. Compared to the traditionally used 3 dB coupler, the presented feed method can have an AR peak with the expected value at the center frequency and two AR valleys beside the peak, while the traditional 3 dB coupler can only get an AR valley with narrower bandwidth. Therefore, much wider AR bandwidths for different AR requirements are obtained by using the presented method. The wideband dual-feed antenna fed by these different couplers was also simulated, fabricated, and measured for the final performance verification

Design, Modelling and Implementation of Several Multi-Standard High Performance Single-Wideband and Multi-Wideband Microwave Planar Filters

The objectives of this work are to review, investigate and model the microwave planar filters of the modern wireless communication system. The recent main stream of microwave filters are classified and discussed separately. Various microwave filters with detailed applications are investigated in terms of their geometrical structures and operational performances. A comprehensive theoretical study of microwave filters is presented. The main types of microwave filters including the basic low-pass filters such as Butterworth and Chebyshev filters are fully analysed and described in detail. The transformation from low-pass prototype filters to high-pass filters, band-pass filters and band-stop filters are illustrated and introduced. Research work on stepped impedance resonator (SIR) and asymmetric stepped impedance resonator (ASIR) structure is presented. The characteristics of λg/4, λg/2 and λg (λg is the guided wavelength of the fundamental frequency in the free space) type SIR resonators, and the characteristic of asymmetric SIR resonator are categorized and investigated. Based on the content mentioned above, novel multi-standard high performance asymmetric stepped impedance resonator single-wideband and dual-wideband filters with wide stopbands are proposed. The methodologies to realize wide passband and wide stop-band filters are detailed. In addition, multi-standard high performance triplewideband, quadruple-wideband and quint-wideband filters are suggested and studied. The measurement results for all prototype filters agree well with the theoretical predictions and simulated results from Ansoft HFSS software. The featured broad bandwidths over single/multiple applicable frequency bands and the high performances of the proposed filters make them very promising for applications in future multistandard wireless communication

Novel approaches in voltage-follower design

The aim of this research programme was to design and develop novel voltagefollowerslbuffers, suitable for radio frequency (RF) applications. The emphases throughout has been on improving key characteristics, in particular distortion, operating bandwidth, input and output impedances, offset-voltage and power supply demands of the design. The majority of the results of this work have been reported by the author in the technical literature (I] to (6). Initially this research focuses on the investigation of the underlying operating principles of the voltage-follower to provide an in-depth understanding of its operation. This study concentrates on establishing reasons for the poor distortion, low input and high output impedances and increased offset-voltage and confirmed that these designs have inherently poor performance in these parameters. The analysis is carried out using both theoretical modelling and computer simulation, using the wellestablished software package ORCAD PSpice. Despite the availability of high performance computer simulation tools, it becomes apparent that 'hand' calculations in the design process, generally based on DC and small-signal transistor parameters, are essential. Therefore a detailed analysis of the transistor-models used throughout this research is carried out with PSpice data. Using the analytical results of the conventional voltage-follower as a benchmark, various novel circuit techniques investigated. Several new circuits are proposed with respect to improving the previously mentioned key characteristics. The first technique comprises local feedback and single-valued current biasing and 111 consists of emitter-followers exclusively throughout the signal path, keeping the distortion of the input signal to low levels [1 J, (2). The second technique is based on local feedback with double-valued current biasing, increasing somewhat the power dissipation but reducing, notably, the distortion of the configuration [3J, [4J, [5J, [6J. The final technique employs the emitter-followers throughout the signal path in combination with global feedback and double-valued current biasing, which presents significantly better results, on certain parameters, than conventional and existing configurations. It is anticipated that this work will be published in the near future

Designing a Compact Microstrip Antenna Using the Machine Learning Approach, Journal of Telecommunications and Information Technology, 2020, nr 4

This paper presents how machine learning techniques may be applied in the process of designing a compact dual-band H-shaped rectangular microstrip antenna (RMSA) operating in 0.75–2.20 GHz and 3.0–3.44 GHz frequency ranges. In the design process, the same dimensions of upper and lower notches are incorporated, with the centered position right in the middle. Notch length and width are verified for investigating the antenna. An artificial neural network (ANN) model is developed from the simulated dataset, and is used for shape prediction. The same dataset is used to create a mathematical model as well. The predicted outcome is compared and it is determined that the model relying on ANN offers better result

Design and characterization of the measurement electronics for a magnetic induction tomography imaging system

Includes abstract.Includes bibliographical references (p. 103-110).A data acquisition transceiver circuit for magnetic induction tomography (MIT) has been developed. MIT is a type of tomography technique that is sensitive to the conductivity of objects, and which can be used in both industrial and biomedical applications. A detailed design process of the MIT transceiver board and the coupling sensor coils are presented in this dissertation. For the purpose of testing the designed hardware, a three channel MIT measuring system was assembled, and various experiments were run on the system. Several different samples with high conductivity (metal sheets) or low conductivity (saline solution) were used to test the performance of the designed transceiver. Its suitability for being applied to the actual MIT system could then be assessed. The noise characteristics and stability of the system were also characterised. A complete eight channel MIT measurement system is presently being assembled based on the prototypes presented in the dissertation. The results obtained from the experiments are very promising. The construction of the multi-channel MIT system and the image reconstruction can confidently be expected in future development