Electromagnetic radiation from 3 Hz to 30 kHz in the ELF/ULF/VLF bands sees continued and even renewed interest, despite significant engineering challenges in creating portable radiation systems in ...this frequency range. A novel mechanical shutter-based antenna with fixed permanent magnets is presented that allows for broadband radiation from a handheld source without the excessive mechanical requirements that have made traditional mechanical antenna concepts impractical. The validated prototype is a mechanical alternative to an electrically short antenna.
Microwave UWB radar and imaging provides perspectives for early-stage breast cancer detection. We present an experimental MIMO setup for breast phantom trials based on M-sequence radar technology and ...electrically short antennas (bowtie dipoles). This approach combines short impulse responses, sufficient fidelity and very small antenna dimension and allows array construction with sufficient number of antennas around the breast. Obtained imaging results will be presented and aspects regarding the array configuration will be discussed.
Electromagnetic ultra-wideband sensing and imaging provides perspectives for early-stage breast cancer detection. This paper deals with practical challenges of real measurements. We present an ...experimental setup for breast phantom trials based on M-sequence radar technology. In contrast to similar published works we apply electrically short antennas (bowtie dipoles). This approach combines short impulse responses, appropriate fidelity and very small antenna dimension and allows array construction with sufficient number of antennas around the breast. Obtained imaging results are presented and significant aspects are discussed.
An active dipole antenna is in operation since five years at the Nançay radio Observatory (France) in the CODALEMA experiment. A new version of this active antenna has been developed, whose shape ...gave its name of “Butterfly” antenna. Compared to the previous version, this new antenna has been designed to be more efficient at low frequencies, which could permit the detection of atmospheric showers at large distances. Despite a size of only 2
m in each polarization, its sensitivity is excellent in the 30–80
MHz bandwidth. Three antennas in dual polarization were installed on the CODALEMA experiment, and four other have been recently installed on the Auger area in the scope of the AERA project. The main characteristics of the Butterfly antenna are detailed with an emphasis on its key features which make it a good candidate for the low frequency radioastronomy and the radio detection of transients induced by high energy cosmic rays.
A probe station based setup for on-wafer antenna measurements is presented. The setup allows for measurement of return loss and radiation patterns of an on-wafer antenna-hence-forth referred to as ...the antenna under test (AUT), radiating at broadside and fed through a coplanar waveguide (CPW). It eliminates the need for wafer dicing and custom-built test fixtures with coaxial connectors or waveguide flanges by contacting the AUT with a coplanar microwave probe. In addition, the AUT is probed exactly where it will be connected to a transceiver IC later on, obviating de-embedding of the measured data. Sources of measurement errors are related to calibration, insufficient dynamic range, misalignment, forward scattering from nearby objects, and vibrations. The performance of the setup is demonstrated from 2 to 40 GHz through measurement of an on-wafer electrically small slot antenna (lambda 0 /35 times lambda 0 /35,3.5 times 3.5 mm 2 ) radiating at 2.45 GHz and an aperture coupled microstrip antenna (2.4 times 1.7 mm 2 ) radiating at 38 GHz.
The radiation resistance of a short planar monopole antenna with a small ground plane is studied. The monopole of length h (λ/100 <; h <; λ/10) is located orthogonally to the edge of a rectangular ...ground plane of length L and width W . First, a parametric study is realized in order to determine the effect of the ground plane dimensions on the radiation resistance. Then, the two limit configurations, long and wide, are studied analytically with a model based on triangular current distributions, and comparisons to numerical results are shown. Finally, impedance matching by addition of one or two dipole arms is studied. We explain why this addition, besides reactance compensation, further increases the radiation resistance.
Modern high-efficiency EER transmitters to comply with the standards for electromagnetic compatibility require very precise matching with the load. The antennas used on board are often electrically ...short and therefore narrow-banded. Traditional LC-matching in some cases can not provide the required level of SWR. A method for matching electrically short narrow-band antennas with the help of RLC-circuits is proposed. It allows providing the required SWR value of the load not more than 1.05 in the band of the OFDM signal of 10 kHz and not more than 1.1 in the band of 20 kHz. A technique for designing a RLC frequency extension circuit is developed. The carried out analysis of the energy efficiency of the frequency extension circuit showed that if the antenna 3-dB bandwidth exceeds 10 kHz, the losses in the FEC do not exceed 1 dB. The developed method for calculating the frequency extension circuit was tested for Digital Radio Mondiale (DRM) LW broadcasting stations. The possibility matching of existing antennas with a height of 257 meters for the DRM mode with 9/10 kHz signal bandwidth over the entire range of LW is shown. Also, the potential for using Simulcast mode with a dual signal bandwidth is shown: for the upper half of the low-frequency range, with antennas 257 meters high and 378 meters for the lower one.
An empirical path-loss model derived from practical experiments through open space area with LOS link between two antennae, maximum extent to 30m, and less than 3meters antenna height, including ...tropical climate. Fresnel radius was practically affecting the model during different distances which has discussed. The model was successfully tested and compared with for distance measurement based on RSS technique which analyzed with the Fresnel radius. A calculator application is also generated to proceed the computations and it could automatically recognized if distance is an even Fresnel radius and recalculate the distance with consideration of Fresnel effects. Average error of distance measurement with use of this calculator was decreased by about 60%.
Objašnjen je osnovni princip rada oscilatora, uvjet samopobude i analizirana posebnost oscilatora temeljenog na nefosterovskoj impedanciji/admitanciji. Razjašnjene su temeljne karakteristike sklopova ...za dobivanje negativne impedancije te provedene simulacije S-parametara, tranzijentna analiza, simulacija velikog signala te AC analiza. Sve simulacije sklopova provedene su u programskom paketu ADS s ultra-brzim operacijskim pojačalom THS4304. Također, diskutiran je utjecaj nelinearnih efekata na svojstva negativne impedancije. Dani su temeljni zaključci u vezi negativnih pretvornika impedancije N-tipa i S-tipa. Projektirana su i međusobno komparirana tri različita oscilatora temeljena na nefosterovskoj impedanciji te analizirani njihovi valni oblici, procesi utitravanja, spektri i izlazna snaga. Razmatrani su načini ugađanja frekvencije te ovisnost frekvencije o teretu i izvedbi negativnog pretvornika impedancije. Serijski spoj kapaciteta i otpora ili induktiviteta i otpora simulirao je kao teret električki kratku antenu, a rezonantni sklop omogućio promjenu frekvencije osciliranja u širem frekvencijskom opsegu. Na koncu su obavljena mjerenja na praktično ostvarenim sklopovima i uspoređeni rezultati sa simulacijama.
Basic working principles of oscillator and conditions for oscillation were explained and specialty of oscillator based on non-Foster impedance/admittance was analised. Also, basic characteristics of circuits designed to get negative impedance were explained together with S-parameter simulations, transient simulations, large signal and AC simulations. All before mentioned simulations were performed with program ADS and based on high-speed operational amplifier THS4304. Moreover, influence of nonlinear effects on changing negative impedance characterictics was discussed. Some basic conclusions were given about short circuit stable and open circuit stable types of negative impedance converter. Three different designs of oscillator based on non-Foster impedance were made and compared as well as their waveforms, oscillation process, spectrum and output power were analised. Tuning of frequency and frequency dependance considering the load and negative impedance converter design was also discussed. Electrically short antenna as the load was simulated with serial combination of resistance and capacitance/inductance and resonant circuit enabled frequency tuning within wide frequency range. In the end measurements were made on practical circuits and compared with simulation results.