Gunnar Armbrecht

Bio: Gunnar Armbrecht is an academic researcher from Leibniz University of Hanover. The author has contributed to research in topics: Antenna (radio) & Radar. The author has an hindex of 10, co-authored 61 publications receiving 386 citations.

Antenna characterization in a waveguide

Abstract: A method for determining at least one characteristic of an antenna requiring: a) positioning an antenna in a space surrounded by a waveguide; b) feeding an electric excitation signal (u tx (t)) into a feed connection of the waveguide; c) receiving the electric response signal (u rx (t)) emitted by the antenna resulting from the excitation signal (u tx (t)); d) determining at least one characteristic of the antenna from a portion of the response signal (u rx (t)) and a corresponding portion of the excitation signal (u tx (t)), where the portion of the response signal (u rx (t)) is evaluated in the time domain and satisfies the following conditions: (i) only one or more waves of the electromagnetic field caused by the excitation signal (u tx (t)) and running from the feed connection towards the antenna exist at the location of the antenna; and (ii) the electromagnetic field at the location of the antenna is a TEM field.

High frequency plasma ignition device

Abstract: A high frequency plasma ignition device for the ignition of a fuel/air mixture in a combustion chamber of an internal combustion engine, having a series resonant circuit of an electric inductor and an electric capacitor connected in series, and a high frequency generator with a first electrical terminal and a second electrical terminal for the resonant excitation of the series resonant circuit, a first electrical contact point being provided in which one end of the capacitor and one end of the inductor are connected to one another electrically. An electrical connecting device connects the high-frequency generator to the inductor and to the capacitor such that an output signal of the high-frequency generator is applied to the series resonant circuit. An electric voltage is applied across the capacitor for igniting a plasma between free ends of a first and second electrode. An electric voltage is further applied to maintain the plasma after ignition.

Compact directional UWB antenna with dielectric insert for radar distance measurements

Abstract: A circular waveguide-fed UWB antenna for the frequency range from 8.5 to 10.5 GHz is presented, incorporating a dielectric insert mounted inside a short metallic excitation horn, yielding a significantly enlarged aperture efficiency compared to the same horn without dielectric insert and even to the theoretical limit of a conical horn antenna of infinite length having similar geometrical aperture restrictions. Regarding industrial radar level gauging, the maximum antenna dimensions are strictly limited due to standardized nozzle and flange diameters and thus compact directional antennas with low side lobe levels are needed allowing broadband radar operation and simultaneously suppressing signal distortions by unwanted scatterers. By utilizing a prototype setup of the proposed antenna, the anticipated performance gain is proved by measurement results validating the simulated characteristic antenna parameters as well as the improved radar distance measurement accuracy.

Computation of antenna pattern correlation and MIMO performance by means of surface current distribution and\ spherical wave theory

Abstract: . In order to satisfy the stringent demand for an accurate prediction of MIMO channel capacity and diversity performance in wireless communications, more effective and suitable models that account for real antenna radiation behavior have to be taken into account. One of the main challenges is the accurate modeling of antenna correlation that is directly related to the amount of channel capacity or diversity gain which might be achieved in multi element antenna configurations. Therefore spherical wave theory in electromagnetics is a well known technique to express antenna far fields by means of a compact field expansion with a reduced number of unknowns that was recently applied to derive an analytical approach in the computation of antenna pattern correlation. In this paper we present a novel and efficient computational technique to determine antenna pattern correlation based on the evaluation of the surface current distribution by means of a spherical mode expansion.

Antenna Impact on the Gauging Accuracy of Industrial Radar Level Measurements

Abstract: This paper deals with a systematic evaluation of the antenna impact on the gauging accuracy of industrial radar level measurements for process automation. By this means, a framework is provided by which the antenna parameters of major influence on the gauging accuracy can be identified. Guidelines are given to what extent an improvement of these parameters results in a measurable accuracy increase. Firstly, the radar system theory for monostatic level gauging and the emulation of such radar systems by software and hardware are briefly reviewed. Secondly, an analytical model of traveling-wave endfire antennas is introduced, allowing to separately study the influence of individual antenna parameters on the distance measurement accuracy. Thus, a direct relationship between characteristic antenna properties, such as the level of the pattern attenuation in the direction of a parasitic scatterer, and the gauging performance is obtained. The investigations are conducted for one specific pulse-based barycentric signal-processing scheme, which is predestined for industrial level gauging due to its low complexity and reliability. Finally, the results are verified by measurements within a compact radar test range.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Method and apparatus for coupling an antenna to a device

Abstract: Aspects of the subject disclosure may include, for example, receiving, by a feed point of a dielectric antenna, electromagnetic waves from a dielectric core coupled to the feed point without an electrical return path, where at least a portion of the dielectric antenna comprises a conductive surface, directing, by the feed point, the electromagnetic waves to a proximal portion of the dielectric antenna, and radiating, via an aperture of the dielectric antenna, a wireless signal responsive to the electromagnetic waves being received at the aperture. Other embodiments are disclosed.

Remote distributed antenna system

Abstract: A distributed antenna system is provided that frequency shifts the output of one or more microcells to a 60 GHz or higher frequency range for transmission to a set of distributed antennas. The cellular band outputs of these microcell base station devices are used to modulate a 60 GHz (or higher) carrier wave, yielding a group of subcarriers on the 60 GHz carrier wave. This group will then be transmitted in the air via analog microwave RF unit, after which it can be repeated or radiated to the surrounding area. The repeaters amplify the signal and resend it on the air again toward the next repeater. In places where a microcell is required, the 60 GHz signal is shifted in frequency back to its original frequency (e.g., the 1.9 GHz cellular band) and radiated locally to nearby mobile devices.

Method and apparatus for sensing a condition in a transmission medium of electromagnetic waves

Abstract: Aspects of the subject disclosure may include, for example, a device that facilitates transmitting electromagnetic waves along a surface of a wire that facilitates delivery of electric energy to devices, and sensing a condition that is adverse to the electromagnetic waves propagating along the surface of the wire. Other embodiments are disclosed.