Martin Holters | Helmut Schmidt University (original) (raw)
Papers by Martin Holters
2016 24th European Signal Processing Conference (EUSIPCO), 2016
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ACME v0.9.3 Diff since v0.9.2 <strong>Closed issues:</strong> Readme uses deprecated ... more ACME v0.9.3 Diff since v0.9.2 <strong>Closed issues:</strong> Readme uses deprecated syntax (#18) <strong>Merged pull requests:</strong> Fix usage of outdated Julia syntax in README.md (#19) (@martinholters) Extend MOSFET model (#21) (@martinholters)
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The sound of a vacuum tube guitar amplifier may be significantly influenced by the non-linear beh... more The sound of a vacuum tube guitar amplifier may be significantly influenced by the non-linear behavior of its output transformer, which therefore should also be considered in digital simulations. In this work, we develop a model for inductors and transformers with the magnetization following the model of Jiles and Atherton. For this purpose, the original magnetization model is rewritten to a differential equation with respect to time which can then easily be integrated into a previously developed circuit simulation framework. The model thus derived is then exercised in the simulation of three simple circuits where it shows the expected behavior.
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The Ebers-Moll model has been widely used to represent Bipolar Junction Transistors (BJTs) in Vir... more The Ebers-Moll model has been widely used to represent Bipolar Junction Transistors (BJTs) in Virtual Analogue (VA) circuits. An investigation into the validity of this model is presented in which the Ebers-Moll model is compared to BJT models of higher complexity, introducing the Gummel-Poon model to the VA field. A comparison is performed using two complementary approaches: on fit to measurements taken directly from BJTs, and on application to physical circuit models. Targeted parameter extraction strategies are proposed for each model. There are two case studies, both famous vintage guitar effects featuring germanium BJTs. Results demonstrate the effects of incorporating additional complexity into the component model, weighing the trade-off between differences in the output and computational cost.
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The Red Llama guitar overdrive effect pedal differs from most other overdrive effects because it ... more The Red Llama guitar overdrive effect pedal differs from most other overdrive effects because it utilizes CMOS inverters, formed by two metal-oxide-semiconductor field-effect transistors (MOSFETs), instead of a combination of operational amplifiers and diodes to obtain nonlinear distortion. This makes it an interesting subject for virtual analog modeling, obviously requiring a suitable model for the CMOS inverters. Therefore, in this paper, we extend a well-known model for MOSFETs by a straight-forward heuristic approach to achieve a good match between the model and measurement data obtained for the individual MOSFETs. This allows a faithful digital simulation of the Red Llama.
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A straight-forward design of graphic equalizers with minimumphase behavior based on recently deve... more A straight-forward design of graphic equalizers with minimumphase behavior based on recently developed higher-order bandshelving filters is presented. Due to the high filter order, the gain in one band is almost completely independent from the gain in the other bands. Although no special care will be taken to design filters with complementary edges except for a suitable definition of the cut-off frequencies, the resulting amplitude deviation in the transitional region between the bands will be sufficiently low for many applications.
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Bucket brigade devices (BBDs) were invented in the late 1960s as a method of introducing a time-d... more Bucket brigade devices (BBDs) were invented in the late 1960s as a method of introducing a time-delay into an analog electrical circuit. They work by sampling the input signal at a certain clock rate and shifting it through a chain of capacitors to obtain the delay. BBD chips have been used to build a large variety of analog effects processing devices, ranging from chorus to flanging to echo effects. They have therefore attracted interest in virtual analog modeling and a number of approaches to modeling them digitally have appeared. In this paper, we propose a new model for the bucket-brigade device. This model is based on a variable samplerate, and utilizes the surrounding filtering circuitry found in real devices to avoid the need for the interpolation usually needed in such a variable sample-rate system.
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Applied Sciences
Nonlinear systems, such as guitar distortion effects, play an important role in musical signal pr... more Nonlinear systems, such as guitar distortion effects, play an important role in musical signal processing. One major problem encountered in digital nonlinear systems is aliasing distortion. Consequently, various aliasing reduction methods have been proposed in the literature. One of these is based on using the antiderivative of the nonlinearity and has proven effective, but is limited to memoryless systems. In this work, it is extended to a class of stateful systems which includes but is not limited to systems with a single one-port nonlinearity. Two examples from the realm of virtual analog modeling show its applicability to and effectiveness for commonly encountered guitar distortion effect circuits.
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2006 14th European Signal Processing Conference, Sep 4, 2006
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2012 6th International Conference on Signal Processing and Communication Systems, Dec 1, 2012
ABSTRACT High Frequency Surface Wave Radars (HFSWRs) play an important role in long-range ocean s... more ABSTRACT High Frequency Surface Wave Radars (HFSWRs) play an important role in long-range ocean surveillance, with particular interest in reliable detection and tracking of far-distant ships. One of the biggest challenges in ship target detection in HFSWR is the non-homogeneous detection background. Depending on the chosen detection parameters, this non-homogeneous detection background leads to extensive false alarms or poor detection performance. This paper shows how scan-by-scan averaging can help to reduce a significant number of these false alarms. In addition the problem of target spreading and multiple detections of the same target is addressed by an Adjacent Detection Merging Algorithm (ADMA). Furthermore, it is shown how the result of the ADMA can be used to improve the estimation of target parameters, such as azimuth, Doppler and range.
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4Th European Education and Research Conference, Dec 1, 2010
ABSTRACT
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2016 24th European Signal Processing Conference (EUSIPCO), 2016
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ACME v0.9.3 Diff since v0.9.2 <strong>Closed issues:</strong> Readme uses deprecated ... more ACME v0.9.3 Diff since v0.9.2 <strong>Closed issues:</strong> Readme uses deprecated syntax (#18) <strong>Merged pull requests:</strong> Fix usage of outdated Julia syntax in README.md (#19) (@martinholters) Extend MOSFET model (#21) (@martinholters)
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A changelog is being generated, please check back in a few minutes.
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The sound of a vacuum tube guitar amplifier may be significantly influenced by the non-linear beh... more The sound of a vacuum tube guitar amplifier may be significantly influenced by the non-linear behavior of its output transformer, which therefore should also be considered in digital simulations. In this work, we develop a model for inductors and transformers with the magnetization following the model of Jiles and Atherton. For this purpose, the original magnetization model is rewritten to a differential equation with respect to time which can then easily be integrated into a previously developed circuit simulation framework. The model thus derived is then exercised in the simulation of three simple circuits where it shows the expected behavior.
Bookmarks Related papers MentionsView impact
The Ebers-Moll model has been widely used to represent Bipolar Junction Transistors (BJTs) in Vir... more The Ebers-Moll model has been widely used to represent Bipolar Junction Transistors (BJTs) in Virtual Analogue (VA) circuits. An investigation into the validity of this model is presented in which the Ebers-Moll model is compared to BJT models of higher complexity, introducing the Gummel-Poon model to the VA field. A comparison is performed using two complementary approaches: on fit to measurements taken directly from BJTs, and on application to physical circuit models. Targeted parameter extraction strategies are proposed for each model. There are two case studies, both famous vintage guitar effects featuring germanium BJTs. Results demonstrate the effects of incorporating additional complexity into the component model, weighing the trade-off between differences in the output and computational cost.
Bookmarks Related papers MentionsView impact
The Red Llama guitar overdrive effect pedal differs from most other overdrive effects because it ... more The Red Llama guitar overdrive effect pedal differs from most other overdrive effects because it utilizes CMOS inverters, formed by two metal-oxide-semiconductor field-effect transistors (MOSFETs), instead of a combination of operational amplifiers and diodes to obtain nonlinear distortion. This makes it an interesting subject for virtual analog modeling, obviously requiring a suitable model for the CMOS inverters. Therefore, in this paper, we extend a well-known model for MOSFETs by a straight-forward heuristic approach to achieve a good match between the model and measurement data obtained for the individual MOSFETs. This allows a faithful digital simulation of the Red Llama.
Bookmarks Related papers MentionsView impact
A straight-forward design of graphic equalizers with minimumphase behavior based on recently deve... more A straight-forward design of graphic equalizers with minimumphase behavior based on recently developed higher-order bandshelving filters is presented. Due to the high filter order, the gain in one band is almost completely independent from the gain in the other bands. Although no special care will be taken to design filters with complementary edges except for a suitable definition of the cut-off frequencies, the resulting amplitude deviation in the transitional region between the bands will be sufficiently low for many applications.
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Bucket brigade devices (BBDs) were invented in the late 1960s as a method of introducing a time-d... more Bucket brigade devices (BBDs) were invented in the late 1960s as a method of introducing a time-delay into an analog electrical circuit. They work by sampling the input signal at a certain clock rate and shifting it through a chain of capacitors to obtain the delay. BBD chips have been used to build a large variety of analog effects processing devices, ranging from chorus to flanging to echo effects. They have therefore attracted interest in virtual analog modeling and a number of approaches to modeling them digitally have appeared. In this paper, we propose a new model for the bucket-brigade device. This model is based on a variable samplerate, and utilizes the surrounding filtering circuitry found in real devices to avoid the need for the interpolation usually needed in such a variable sample-rate system.
Bookmarks Related papers MentionsView impact
Applied Sciences
Nonlinear systems, such as guitar distortion effects, play an important role in musical signal pr... more Nonlinear systems, such as guitar distortion effects, play an important role in musical signal processing. One major problem encountered in digital nonlinear systems is aliasing distortion. Consequently, various aliasing reduction methods have been proposed in the literature. One of these is based on using the antiderivative of the nonlinearity and has proven effective, but is limited to memoryless systems. In this work, it is extended to a class of stateful systems which includes but is not limited to systems with a single one-port nonlinearity. Two examples from the realm of virtual analog modeling show its applicability to and effectiveness for commonly encountered guitar distortion effect circuits.
Bookmarks Related papers MentionsView impact
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2006 14th European Signal Processing Conference, Sep 4, 2006
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2012 6th International Conference on Signal Processing and Communication Systems, Dec 1, 2012
ABSTRACT High Frequency Surface Wave Radars (HFSWRs) play an important role in long-range ocean s... more ABSTRACT High Frequency Surface Wave Radars (HFSWRs) play an important role in long-range ocean surveillance, with particular interest in reliable detection and tracking of far-distant ships. One of the biggest challenges in ship target detection in HFSWR is the non-homogeneous detection background. Depending on the chosen detection parameters, this non-homogeneous detection background leads to extensive false alarms or poor detection performance. This paper shows how scan-by-scan averaging can help to reduce a significant number of these false alarms. In addition the problem of target spreading and multiple detections of the same target is addressed by an Adjacent Detection Merging Algorithm (ADMA). Furthermore, it is shown how the result of the ADMA can be used to improve the estimation of target parameters, such as azimuth, Doppler and range.
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4Th European Education and Research Conference, Dec 1, 2010
ABSTRACT
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