Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.736943
W.H. Buttner, L. Staphorst, L. Linde
The purpose of this paper is the investigation of trellis decoding of linear block codes. The intersymbol relationship of convolutional codes makes the Viterbi algorithm ideally suited as a decoding strategy. By representing linear block codes in trellis form, the Viterbi algorithm can also be used to decode linear block codes. A distinct advantage of the Viterbi algorithm above traditional block decoders, is the existence of efficient soft decision algorithms employing channel measurement information. This paper will investigate a method of constructing trellises for block codes as well as the Viterbi decoding of block codes using these trellises. The proposed block trellis decoding technique will be supported with simulation results, comparing its performance with traditional methods such as syndrome decoding.
{"title":"Trellis decoding of linear block codes","authors":"W.H. Buttner, L. Staphorst, L. Linde","doi":"10.1109/COMSIG.1998.736943","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736943","url":null,"abstract":"The purpose of this paper is the investigation of trellis decoding of linear block codes. The intersymbol relationship of convolutional codes makes the Viterbi algorithm ideally suited as a decoding strategy. By representing linear block codes in trellis form, the Viterbi algorithm can also be used to decode linear block codes. A distinct advantage of the Viterbi algorithm above traditional block decoders, is the existence of efficient soft decision algorithms employing channel measurement information. This paper will investigate a method of constructing trellises for block codes as well as the Viterbi decoding of block codes using these trellises. The proposed block trellis decoding technique will be supported with simulation results, comparing its performance with traditional methods such as syndrome decoding.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129029654","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.737007
I. Meier, J. B. de Swardt
Microwave field pattern synthesis using interference is proposed as a novel approach to microwave heating. It is based on ideas already well known from optics (interference circles, holograms), but applied and adapted to microwaves. The angle of total transmission (Brewster's angle) keeps reflections at the microwave to material interface to a minimum, thereby improving energy transfer. Signals from two injection-locked magnetron based sources are made to interfere with each other to demonstrate the idea. No direct limit is imposed on the number of sources by the topology. Simulation indicates that certain heating patterns can be obtained, simply changing relative phases between sources. Phase being variable, particular average heat distribution patterns can be realized throughout the interference space. Limits mainly occur as a result of material properties, especially loss, material dimensions and wavelength.
{"title":"Interference modulation for microwave dielectric heating","authors":"I. Meier, J. B. de Swardt","doi":"10.1109/COMSIG.1998.737007","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.737007","url":null,"abstract":"Microwave field pattern synthesis using interference is proposed as a novel approach to microwave heating. It is based on ideas already well known from optics (interference circles, holograms), but applied and adapted to microwaves. The angle of total transmission (Brewster's angle) keeps reflections at the microwave to material interface to a minimum, thereby improving energy transfer. Signals from two injection-locked magnetron based sources are made to interfere with each other to demonstrate the idea. No direct limit is imposed on the number of sources by the topology. Simulation indicates that certain heating patterns can be obtained, simply changing relative phases between sources. Phase being variable, particular average heat distribution patterns can be realized throughout the interference space. Limits mainly occur as a result of material properties, especially loss, material dimensions and wavelength.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122357324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.736945
B.J. Van Wyk, F. Virolleau
A method to simulate a room impulse response using optimum quasi bi-orthogonal (OQB) filters in an octave filter bank structure is demonstrated. It is further shown that the poly-phase adaptive filter structure (PPS) or the log transform can be used to obtain accurate subband reference responses and that equi order filters in the subbands yield satisfactory results.
{"title":"The application of optimum quasi bi-orthogonal wavelets to the simulation of room acoustics","authors":"B.J. Van Wyk, F. Virolleau","doi":"10.1109/COMSIG.1998.736945","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736945","url":null,"abstract":"A method to simulate a room impulse response using optimum quasi bi-orthogonal (OQB) filters in an octave filter bank structure is demonstrated. It is further shown that the poly-phase adaptive filter structure (PPS) or the log transform can be used to obtain accurate subband reference responses and that equi order filters in the subbands yield satisfactory results.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"279 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130633527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.736976
A. Wilkinson
The joint statistics of coregistered SAR images are studied, concentrating particularly on the statistics of the signals in layover areas of the SAR image. A new model for the joint statistics in layover areas (i.e., where several parts of the scene map into the same range bin) is derived. It is shown that, under certain assumptions, the statistics in layover areas may be modelled by a jointly circular Gaussian probability distribution, parameterized by the so-called covariance matrix. It is shown that the coherence between two SAR images may be expressed as the weighted average of the complex coherence values of each of the individual regions whose mappings are overlaid. The model is verified with simulated data.
{"title":"Synthetic aperture radar interferometry: a model for the joint statistics in layover areas","authors":"A. Wilkinson","doi":"10.1109/COMSIG.1998.736976","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736976","url":null,"abstract":"The joint statistics of coregistered SAR images are studied, concentrating particularly on the statistics of the signals in layover areas of the SAR image. A new model for the joint statistics in layover areas (i.e., where several parts of the scene map into the same range bin) is derived. It is shown that, under certain assumptions, the statistics in layover areas may be modelled by a jointly circular Gaussian probability distribution, parameterized by the so-called covariance matrix. It is shown that the coherence between two SAR images may be expressed as the weighted average of the complex coherence values of each of the individual regions whose mappings are overlaid. The model is verified with simulated data.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"83 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132017793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.736954
G. Carter, R. Inggs
This paper presents a else study which explores the use of system level simulation for digital systems. A digital filter for a synthetic aperture radar was designed and tested using a RASSP (rapid application specific signal processor) like design process.
{"title":"System level simulation of digital designs: a case study","authors":"G. Carter, R. Inggs","doi":"10.1109/COMSIG.1998.736954","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736954","url":null,"abstract":"This paper presents a else study which explores the use of system level simulation for digital systems. A digital filter for a synthetic aperture radar was designed and tested using a RASSP (rapid application specific signal processor) like design process.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128771332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.736989
P. Meyer
A theoretical and experimental evaluation of different mode-matching formulations for microstrip lines is presented. Four different formulations, using the two-dimensional method-of-lines for the calculation of the modes, are investigated. A number of measured microstrip steps, open ends and gaps are used for evaluation, with excellent results being obtained.
{"title":"Accuracy and convergence of mode-matching formulations for microstrip circuits, using the method-of-lines","authors":"P. Meyer","doi":"10.1109/COMSIG.1998.736989","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736989","url":null,"abstract":"A theoretical and experimental evaluation of different mode-matching formulations for microstrip lines is presented. Four different formulations, using the two-dimensional method-of-lines for the calculation of the modes, are investigated. A number of measured microstrip steps, open ends and gaps are used for evaluation, with excellent results being obtained.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128841861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.736967
G. W. Milne, E. Jansen, J. J. Roux, J. Koekemoer, P. Kotzé
The 63 kg SUNSAT micro-satellite includes VHF (144-146 MHz) narrowband FM (NBFM) radio receivers for amateur radio service. Significant radio frequency interference (RFI) from data buses was a problem, but was successfully screened from antennas using aluminium plates. The harmonics and noise of from the 650 kHz switching regulators drifted through receiver channels causing unpredictable sensitivity losses of up to 20 dB. Without shielding, the regulators generated signals at VHF of -85 dBm in a quarter wave antenna at 0.5 m range. This is 34 dB above the noise floor of a 2 dB NF 18 kHz BW VHF receiver. Test results, solution methods, measurement techniques, and lessons learned are reported in this paper.
{"title":"EMC and RFI problems and solutions on the SUNSAT micro-satellite","authors":"G. W. Milne, E. Jansen, J. J. Roux, J. Koekemoer, P. Kotzé","doi":"10.1109/COMSIG.1998.736967","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736967","url":null,"abstract":"The 63 kg SUNSAT micro-satellite includes VHF (144-146 MHz) narrowband FM (NBFM) radio receivers for amateur radio service. Significant radio frequency interference (RFI) from data buses was a problem, but was successfully screened from antennas using aluminium plates. The harmonics and noise of from the 650 kHz switching regulators drifted through receiver channels causing unpredictable sensitivity losses of up to 20 dB. Without shielding, the regulators generated signals at VHF of -85 dBm in a quarter wave antenna at 0.5 m range. This is 34 dB above the noise floor of a 2 dB NF 18 kHz BW VHF receiver. Test results, solution methods, measurement techniques, and lessons learned are reported in this paper.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125444614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.736982
J. Abele, J. Joubert, J. Odendaal
Omnidirectional antennas with controllable nulls are desirable in cellular communication systems. The introduction of nulls in the pattern of a general antenna array has been widely discussed. However, for omnidirectional patterns these techniques disturb the pattern and introduce undesirable ripple. A synthesis procedure is proposed for the introduction of multiple nulls with controllable ripple in an omnidirectional pattern of a circular array.
{"title":"Introduction of multiple nulls in an omnidirectional pattern using circular arrays","authors":"J. Abele, J. Joubert, J. Odendaal","doi":"10.1109/COMSIG.1998.736982","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736982","url":null,"abstract":"Omnidirectional antennas with controllable nulls are desirable in cellular communication systems. The introduction of nulls in the pattern of a general antenna array has been widely discussed. However, for omnidirectional patterns these techniques disturb the pattern and introduce undesirable ripple. A synthesis procedure is proposed for the introduction of multiple nulls with controllable ripple in an omnidirectional pattern of a circular array.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121340102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.736973
T.E.W. Stuart, H. Reader
This paper demonstrates the need for care with some EMI problems present in even simple low-frequency (<1 MHz) measurements. Two experiments on cable crosstalk, found in the IEEE EMC Educational Manual, are used. Predictions are made from field theory, and compared to results from a series of measurement setups. Although the setups appear similar, it is found that unwanted coupling between the experiment and the measurement equipment influences the results.
{"title":"Apparently simple low-frequency measurements: an EMC view","authors":"T.E.W. Stuart, H. Reader","doi":"10.1109/COMSIG.1998.736973","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736973","url":null,"abstract":"This paper demonstrates the need for care with some EMI problems present in even simple low-frequency (<1 MHz) measurements. Two experiments on cable crosstalk, found in the IEEE EMC Educational Manual, are used. Predictions are made from field theory, and compared to results from a series of measurement setups. Although the setups appear similar, it is found that unwanted coupling between the experiment and the measurement equipment influences the results.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121739810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.736995
D. Pansegrouw, K. Palmer
A comparative study is presented of a number of commercial CAD package analyses of 4 microstrip patch antennas. Predicted results are compared to measurements, and comparisons of computer run-time are presented. Three techniques to measure the dielectric constant of substrates are also presented.
{"title":"Evaluation of microstrip antenna analysis using numerical tools","authors":"D. Pansegrouw, K. Palmer","doi":"10.1109/COMSIG.1998.736995","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736995","url":null,"abstract":"A comparative study is presented of a number of commercial CAD package analyses of 4 microstrip patch antennas. Predicted results are compared to measurements, and comparisons of computer run-time are presented. Three techniques to measure the dielectric constant of substrates are also presented.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122484462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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