Compact mode-matched excitation structures for radar distance measurements in overmoded circular waveguides
TL;DR: In this article, a waveguide taper concept is presented for low-precision radar measurements of liquid materials in large metal tubes, so-called stilling wells, bypass or still pipes.
Abstract: . This contribution deals with guided radar level measurements of liquid materials in large metal tubes, so-called stilling wells, bypass or still pipes. In the RF domain these tubes function as overmoded circular waveguides and mode-matched excitation structures like waveguide tapers are needed to avoid higher order waveguide modes. Especially for high-precision radar measurements the multimode propagation effects need to be minimized to achieve submillimeter accuracy. Therefore, a still pipe simulator is introduced with the purpose to fundamentally analyze the modal effects. Furthermore, a generalized design criterion is derived for the spurious mode suppression of compact circular waveguide transitions under the constraint of specified accuracy levels. According to the obtained results, a promising waveguide taper concept will finally be presented.
Citations
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TL;DR: In this paper, a systematic evaluation of the antenna impact on the gauging accuracy of industrial radar level measurements for process automation is presented, where a framework is provided by which the antenna parameters of major influence on the measuring accuracy can be identified.
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.
14 citations
Proceedings Article•
30 Oct 2009TL;DR: In this article, the effects of intermodal dispersion are reviewed and based on these results, a correlation-based signal processing method is presented to exploit the otherwise parasitic dispersion effects to enhance the measurement precision even in constellation with a simple waveguide transition or antenna, respectively.
Abstract: This contribution deals with guided radar distance measurements in the field of industrial tank level control. The aim is to achieve a submillimeter gauging accuracy even when conducting the measurement within a highly dispersive environment of large and thus overmoded cylindrical waveguides. Normally multimode propagation causes a decrease in measurement precision. Therefore, the effects of intermodal dispersion are fundamentally reviewed and based on these results, a correlation-based signal processing method is presented. The method is able to exploit the otherwise parasitic dispersion effects to enhance the measurement precision even in constellation with a simple waveguide transition or antenna, respectively. Measurement results in a frequency range of 8.5 to 10.5 GHz are provided for two different kinds of waveguide transitions proving the capability of the method.
11 citations
Cites background or methods from "Compact mode-matched excitation str..."
...As a basic principle, waveguide transitions, when supposed to be loss-free multi-port devices featuring independent ports for each excited mode, cannot be matched for every single port, if multimode excitation is present [2]....
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...Due to the large tube diameter the mode-inherent (chromatic) dispersion of the H11 mode plays an inferior role [2], so the measurement device is able to receive an almost Figure 1....
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...Based on the theoretical fundament of analytical waveguide equations accounting for the mode-dependent propagation behavior inside the metal tube, a MATLAB-based waveguide simulator is utilized in conjunction with an analytical model of a waveguide transition to synthesize multimode propagation scenarios [2]....
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01 Oct 2008
TL;DR: In this paper, the cross-section of a single-moded waveguide is enlarged to an overmoded circular waveguide to obtain a mostly monomode signal propagation within the waveguide, a parabolic waveguide transition in combination with a centrically mounted metallic obstacle is investigated.
Abstract: This contribution deals with a concept for the realization of compact mode-preserving waveguide transitions. For radar distance measurements, the cross-section of a single-moded waveguide is enlarged to an overmoded circular waveguide. In order to obtain a mostly monomode signal propagation within the waveguide, a parabolic waveguide transition in combination with a centrically mounted metallic obstacle is investigated. In comparison to the same transition without obstacle, a significant improvement in terms of the fundamental H11 mode preservation can be achieved over a wide frequency range from 8.5 to 10.5 GHz. Radar measurements are presented that prove the capability of such a concept providing submillimeter distance accuracy without any need of modifying the applied conventional free-space signal processing algorithms.
10 citations
Cites background or methods from "Compact mode-matched excitation str..."
...ing to [5], characteristic optimization values are the modal transmission coefficients, given in terms of scattering parameters of a two-port model derived from a commercial 3D FIT field simulator (CST MICROWAVE STUDIO, Vers....
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...the fundamental mode excitation purity of a conical horn taper obviously suffers from curved phase fronts inside every taper structure [5]....
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...Furthermore, the MATLAB implemented waveguide simulator (see [5] for details) yields the possibility Fig....
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16 Mar 2015
TL;DR: In this article, a time-variant inverse filtering technique has been developed to compensate for the dispersion, and the implementation in a Frequency Modulated Continuous Wave (FMCW) radar level meter is discussed.
Abstract: The conventional approach for radar level measurement of liquids in tanks is to perform echo measurements in the free space above the liquid In this paper, the alternative approach of distance measurement using a bypass, which is a communicating pipe connected with the tank, is discussed The goal behind the presented work was to optimize these systems in order to allow for high precision level measurements It is shown with a system theoretical model of the cylindrical bypass pipe that the given dispersion might introduce severe systematical measurement errors A time-variant inverse filtering technique has been developed to compensate for the dispersion, and the implementation in a Frequency Modulated Continuous Wave (FMCW) radar level meter is discussed For further optimization of the system's performance, especially in the case of weakly-reflecting liquids, a metallic float is used as an improved radar target The proposed concepts have been evaluated by means of measurements with a 57 to 67 GHz FMCW radar system for level measurement using a bypass pipe with an inner diameter of 38 mm Measurement results show that the distance measurement error is decreased from +/−496 mm to +/−144mm by means of the proposed inverse filtering approach
9 citations
Cites background from "Compact mode-matched excitation str..."
...For this reason, TLPR measurements of liquids in tanks are sometimes performed inside a bypass pipe, which is a communicating pipe used as a waveguide for the propagation of microwaves [3-9]....
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TL;DR: In this paper, the effects of intermodal dispersion are fundamentally reviewed and, based on these results, a correlation-based signal processing method is presented to exploit the otherwise parasitic dispersion effects to enhance the measurement precision even in constellation with a simple waveguide transition or antenna, respectively.
Abstract: This contribution deals with guided radar distance measurements in the field of industrial tank level control The aim is to achieve a submillimeter gauging accuracy even when conducting the measurement within a highly dispersive environment of large and thus overmoded circular waveguides Normally, multimode propagation causes a decrease in measurement precision Therefore, the effects of intermodal dispersion are fundamentally reviewed and, based on these results, a correlation-based signal processing method is presented This method is able to exploit the otherwise parasitic dispersion effects to enhance the measurement precision even in constellation with a simple waveguide transition or antenna, respectively Furthermore, considerations on the mode variety and its influence on the signal complexity as well as investigations on the technique's reliability and accuracy are presented Measurement results in a frequency range of 85–105 GHz are provided for three different kinds of waveguide transitions proving the capability of the method
6 citations
References
More filters
Book•
30 Jun 1998
TL;DR: In this paper, the authors present and develop the mathematical tools required to effectively examine and analyse propagation processes of waves of various natures using the cross section method, in artificial and non-artificial waveguides.
Abstract: This book presents and develops the mathematical tools required to effectively examine and analyse propagation processes of waves of various natures using the cross section method, in artificial and non-artificial waveguides. These techniques are used in the solution of practical situations in various fields, such as plasma heating in nuclear fusion, materials processing and radar and satellite communication systems.
133 citations
TL;DR: A 24 GHz FMCW-radar system is presented using a fractional-N phase locked loop ramp generator that achieves relative ramp nonlinearities below 10/sup -8/.
Abstract: A 24-GHz FMCW radar system is presented using a fractional-N phase-locked loop ramp generator. This fractional-N ramp generator achieves relative ramp nonlinearities below 10/sup -8/. Among others linear frequency ramps are important tools in high precision FMCW radar systems. Highly linear frequency ramps make post measurement error correction feasible. Other important aspects of the high performance FMCW radar system are the design of the microwave circuit and the digital signal processing of the IF signals. Furthermore, a large RF bandwidth of more than 3 GHz obtained by thorough simulations results in a high range resolution and a good potential measurement accuracy. To maintain this high potential accuracy, a phase slope algorithm is used to calculate the precise range value leading to a significantly better precision with absolute range errors below 0.8 mm, compared to the commonly used spectral center algorithm.
65 citations
01 Oct 1936
TL;DR: In this article, the conditions for minimum attenuation were obtained for the minimum dielectric loss, substantially perfect shielding, and a simplicity of structure for a hollow pipe system with a high-pass filter.
Abstract: Electromagnetic energy may be transmitted through the inside of hollow tubes of metal, provided the frequency is greater than a certain critical value; this value is inversely proportional to the tube radius and to the dielectric coefficient for the tube interior. Calculations and measurements of the more important characteristics of this new kind of transmission system have been made, and the conditions for minimum attenuation obtained. Terminal devices for connecting a hollow pipe system to a biconductor system and others, in the form of horns, for directly radiating radio waves, have been developed; these electromagnetic horns may also be fed with ordinary coaxial lines. Certain types of terminals act as sharply resonant hollow tube elements. Several independent communication channels may be established within a single pipe line by utilizing distinct types of waves for each channel in a unique kind of multiplex operation. A section of a hollow tube may be used as a high-pass filter. Although presupposing adequate technique for the generation and utilization of the shortest radio waves, this new system possesses several features, among which are a minimum dielectric loss, substantially perfect shielding, and a simplicity of structure.
54 citations
TL;DR: In this article, the authors calculated the scattered field from a hyperboloidal reflector by integrating the induced current density over the front of the hyperboloid, and the resulting integral expressions for the fields possess a stationary term which, when evaluated, yields the geometrical ray-optics approximation to the scattering problem.
Abstract: The scattered field from a hyperboloidal reflector is calculated by integrating the induced current density over the front of the hyperboloid. The resulting integral expressions for the fields possess a stationary term which, when evaluated, yields the geometrical ray-optics approximation to the scattering problem. The complete field, including diffraction effects, may be obtained by numerical evaluation of the integrals. The formulas are applied to a hyperboloid illuminated by an idealized, sharply cut off uniform feed pattern. Characteristic diffraction phenomena are reduced with increasing D/\lambda until the geometrical ray-optics result is obtained in the limit of vanishing wavelength. Theoretical field patterns are also obtained for a horn-fed hyperboloidal subreflector in a Cassegrainian feed system; they indicate that for moderately large hyperboloidal reflectors spillover may be reduced to an acceptable level, but there is a tendency toward increased forward spillover. The results of 9600-Mc model tests compare favorably with the theoretical patterns.
44 citations
08 May 1995
TL;DR: New signal evaluation methods as well as hardware design solutions are presented for measuring product levels in process and storage tanks.
Abstract: Various classical and modern methods exist to measure product levels in process and storage tanks. Instruments which use electromagnetic waves have, for these applications, a lot of advantages. The special requirements for these instruments are pointed out. New signal evaluation methods as well as hardware design solutions are presented.
39 citations
"Compact mode-matched excitation str..." refers background in this paper
...Es- Correspondence to:G. Armbrecht (armbrecht@hft.uni-hannover.de) pecially many commercial radar systems are based on frequency modulated continuous wave (FMCW) technologies (Brumbi, 1995)....
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