Pub Date : 2000-02-22DOI: 10.1109/NRSC.2000.838905
M.A. Aboul Dahab, Mohamed M. M. Omar
Fully or partially adaptive antenna array (AAA) techniques are designed to reduce the effect of interference and jamming signals. This is done by automatically steering nulls in the array field pattern directed towards the direction of arrival of the interfering signal. We present two simple and easy-to-implement partially AAA techniques to eliminate the effect of interfering signal when its direction of arrival is known. The first technique is based upon controlling the amplitudes of the signals at the end-elements of the array. This is done via a proposed algorithm that adjusts the weights of these elements to take one of three preset values. The technique is suitable to steer a null only within the range of the first sidelobe of the array. The second technique utilizes an auxiliary parallel array composed of 2N elements and is capable of steering a deep null at the direction of any sidelobe. This is done by controlling the weight coefficients of all elements of the auxiliary array. A performance criterion is proposed which is based upon equal weight coefficients for all auxiliary elements. In this way, the array has one degree of freedom, i.e. capable of steering only one null in the direction of arrival of interference. Satisfactory results are obtained via computer simulation results of the two techniques.
{"title":"Two partially adaptive antenna array techniques for interference elimination","authors":"M.A. Aboul Dahab, Mohamed M. M. Omar","doi":"10.1109/NRSC.2000.838905","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838905","url":null,"abstract":"Fully or partially adaptive antenna array (AAA) techniques are designed to reduce the effect of interference and jamming signals. This is done by automatically steering nulls in the array field pattern directed towards the direction of arrival of the interfering signal. We present two simple and easy-to-implement partially AAA techniques to eliminate the effect of interfering signal when its direction of arrival is known. The first technique is based upon controlling the amplitudes of the signals at the end-elements of the array. This is done via a proposed algorithm that adjusts the weights of these elements to take one of three preset values. The technique is suitable to steer a null only within the range of the first sidelobe of the array. The second technique utilizes an auxiliary parallel array composed of 2N elements and is capable of steering a deep null at the direction of any sidelobe. This is done by controlling the weight coefficients of all elements of the auxiliary array. A performance criterion is proposed which is based upon equal weight coefficients for all auxiliary elements. In this way, the array has one degree of freedom, i.e. capable of steering only one null in the direction of arrival of interference. Satisfactory results are obtained via computer simulation results of the two techniques.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133019075","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 : 1999-05-18DOI: 10.1109/NRSC.2000.838842
A. Abou El-fadl, H. Boudrand
An algorithm is developed for analyzing the propagation characteristics of multimode planar graded index optical waveguides. The algorithm is based on a modified impedance boundary method of moments, and is used to calculate the dispersion and the field distribution of multimode planar graded-index optical waveguides. The technique is based on Galerkin's procedure and the exact boundary conditions at the interfaces between the graded index guiding region and step index cover and substrate regions. Legendre polynomials are used as basis functions. The efficiency of the algorithm is tested with waveguides having various index profiles such as step, linear, parabolic, exponential, Gaussian, and complementary error functions. The convergence behaviour of the technique is also examined. With this algorithm a minimum number of basis functions is used to provide accurate results. The obtained results show good agreement with other data available in the literature. Moreover, the algorithm can be easily developed to study the propagation and coupling characteristics of planar graded-index optical waveguides directional couplers.
{"title":"Analysis of multimode planar graded index optical waveguides .2","authors":"A. Abou El-fadl, H. Boudrand","doi":"10.1109/NRSC.2000.838842","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838842","url":null,"abstract":"An algorithm is developed for analyzing the propagation characteristics of multimode planar graded index optical waveguides. The algorithm is based on a modified impedance boundary method of moments, and is used to calculate the dispersion and the field distribution of multimode planar graded-index optical waveguides. The technique is based on Galerkin's procedure and the exact boundary conditions at the interfaces between the graded index guiding region and step index cover and substrate regions. Legendre polynomials are used as basis functions. The efficiency of the algorithm is tested with waveguides having various index profiles such as step, linear, parabolic, exponential, Gaussian, and complementary error functions. The convergence behaviour of the technique is also examined. With this algorithm a minimum number of basis functions is used to provide accurate results. The obtained results show good agreement with other data available in the literature. Moreover, the algorithm can be easily developed to study the propagation and coupling characteristics of planar graded-index optical waveguides directional couplers.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123785248","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 : 1900-01-01DOI: 10.1109/NRSC.2000.838975
I. Ashour
Using a 2-D physical model we present a theoretical study of the parameters that affect the saturation condition of an MSM PD under high optical power at 1.55 /spl mu/m wavelength modulated at 40 GHz. We also report that, with an MSM operating at 40 GHz, we can expect a saturation limit with a maximum microwave power of 17 dBm due to the space charge effect.
利用二维物理模型，从理论上研究了在40 GHz调制的1.55 /spl μ l /m波长下高光功率下影响MSM PD饱和状态的参数。我们还报告说，当MSM工作在40 GHz时，由于空间电荷效应，我们可以预期最大微波功率为17 dBm的饱和极限。
{"title":"Microwave high power MSM PD at 1.55 /spl mu/m with optimal gradual heterojunction","authors":"I. Ashour","doi":"10.1109/NRSC.2000.838975","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838975","url":null,"abstract":"Using a 2-D physical model we present a theoretical study of the parameters that affect the saturation condition of an MSM PD under high optical power at 1.55 /spl mu/m wavelength modulated at 40 GHz. We also report that, with an MSM operating at 40 GHz, we can expect a saturation limit with a maximum microwave power of 17 dBm due to the space charge effect.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129396411","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 : 1900-01-01DOI: 10.1109/NRSC.2000.838913
H. Elkamchouchi, H. Hafez
A new antenna is proposed for use in mobile communication systems. Detailed investigations are presented through the results obtained using numerical simulation (the method of moment technique). The wire-loaded monopole antenna has proved many attractive features so that it is recommended to be used in hand held units. The design of the antenna considers simplicity, compact size (65% of monopole height), and low cost. It has an omnidirectional radiation pattern in the horizontal plane with a very high gain (about 6-7 times of monopole antenna). The input impedance matches the feeding line ensuring perfect transmission of energy between the antenna and coaxial cable.
{"title":"Wire-loaded monopole antenna","authors":"H. Elkamchouchi, H. Hafez","doi":"10.1109/NRSC.2000.838913","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838913","url":null,"abstract":"A new antenna is proposed for use in mobile communication systems. Detailed investigations are presented through the results obtained using numerical simulation (the method of moment technique). The wire-loaded monopole antenna has proved many attractive features so that it is recommended to be used in hand held units. The design of the antenna considers simplicity, compact size (65% of monopole height), and low cost. It has an omnidirectional radiation pattern in the horizontal plane with a very high gain (about 6-7 times of monopole antenna). The input impedance matches the feeding line ensuring perfect transmission of energy between the antenna and coaxial cable.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115614961","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 : 1900-01-01DOI: 10.1109/NRSC.2000.838846
H. Ghouz, F. Elghany, M.M. Qutb
For pt.I see ibid., p.B8/1-B8/8 (2000). In phased array radar systems, a tracking process is performed using an electronic scan of a predetermined sector to provide a continuous information about the detected targets. In practice, the presence of interference (noise, clutter, and jamming signals) either prevent or deceive the tracking circuit to follow the real targets, and consequently, the tracking process is terminated. This paper presents an adaptive technique of filtering to suppress the interference in phased array tracking radar systems. The aim is to provide a key feature for discrimination between the desired and the interference signals. Unlike the time processing techniques, the present filtering process is based upon the target Doppler shift as well as the interference spatial distribution to suppress adaptively the undesired signals. This technique of filtering is referred to as adaptive coherent space-time (ACST) filter. The objectives are to investigate and evaluate in detail the performance of the adaptive filter under different interference environments. This includes total intercepted power, type and spatial distribution of the interference. The spatial covariance matrix of the interference is estimated using the direct matrix inversion (DMI) algorithm. Then the optimum Wiener solution for the adaptive filter is obtained. The results of our simulation show that an appreciable improvement in the signal to interference plus noise ratio at the filter's output "SINR/sub o/" is obtained. Also, the filter's performance is very sensitive to the interference type that has a direction either coincident with or close to the desired signal direction. In this case, a trade-off between the filter's complexity and the minimum SINR/sub o/ required for a continuous target tracking should be considered. In conclusion, the presented filter is an attractive and robust solution for solving the tracking problem of low target RCS immersed in interference (e.g., stealth aircraft).
{"title":"Adaptive space-time processing for interference suppression in phased array radar systems. II. Tracking radar","authors":"H. Ghouz, F. Elghany, M.M. Qutb","doi":"10.1109/NRSC.2000.838846","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838846","url":null,"abstract":"For pt.I see ibid., p.B8/1-B8/8 (2000). In phased array radar systems, a tracking process is performed using an electronic scan of a predetermined sector to provide a continuous information about the detected targets. In practice, the presence of interference (noise, clutter, and jamming signals) either prevent or deceive the tracking circuit to follow the real targets, and consequently, the tracking process is terminated. This paper presents an adaptive technique of filtering to suppress the interference in phased array tracking radar systems. The aim is to provide a key feature for discrimination between the desired and the interference signals. Unlike the time processing techniques, the present filtering process is based upon the target Doppler shift as well as the interference spatial distribution to suppress adaptively the undesired signals. This technique of filtering is referred to as adaptive coherent space-time (ACST) filter. The objectives are to investigate and evaluate in detail the performance of the adaptive filter under different interference environments. This includes total intercepted power, type and spatial distribution of the interference. The spatial covariance matrix of the interference is estimated using the direct matrix inversion (DMI) algorithm. Then the optimum Wiener solution for the adaptive filter is obtained. The results of our simulation show that an appreciable improvement in the signal to interference plus noise ratio at the filter's output \"SINR/sub o/\" is obtained. Also, the filter's performance is very sensitive to the interference type that has a direction either coincident with or close to the desired signal direction. In this case, a trade-off between the filter's complexity and the minimum SINR/sub o/ required for a continuous target tracking should be considered. In conclusion, the presented filter is an attractive and robust solution for solving the tracking problem of low target RCS immersed in interference (e.g., stealth aircraft).","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130783027","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 : 1900-01-01DOI: 10.1109/NRSC.2000.838909
A. Zaghloul, A. Abou El-fadl
A new technique is developed for calculating the dispersion characteristics and field distribution of a multimode rib optical waveguide. The technique is based on the combination of the effective index and the variational methods. An algorithm is implemented to study the effect of the structure parameters and dimensions on the dispersion curves for quasi-TE and TM-modes of a rib optical waveguide. The field distribution of the fundamental and higher order modes for the two cases are also computed. The obtained results are compared with other published data where good agreement is found.
{"title":"Two mixed methods for the analysis of a multimode optical rib waveguide","authors":"A. Zaghloul, A. Abou El-fadl","doi":"10.1109/NRSC.2000.838909","DOIUrl":"https://doi.org/10.1109/NRSC.2000.838909","url":null,"abstract":"A new technique is developed for calculating the dispersion characteristics and field distribution of a multimode rib optical waveguide. The technique is based on the combination of the effective index and the variational methods. An algorithm is implemented to study the effect of the structure parameters and dimensions on the dispersion curves for quasi-TE and TM-modes of a rib optical waveguide. The field distribution of the fundamental and higher order modes for the two cases are also computed. The obtained results are compared with other published data where good agreement is found.","PeriodicalId":211510,"journal":{"name":"Proceedings of the Seventeenth National Radio Science Conference. 17th NRSC'2000 (IEEE Cat. No.00EX396)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133456632","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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