2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), 2019
To cater to the exponential growth of terrestrial mobile services, several frequency bands have b... more To cater to the exponential growth of terrestrial mobile services, several frequency bands have been included for use in International Mobile Telecommunications (IMT). Consequently, the 2500-2690 MHz frequency band is now being shared between Band 41 of 4G-LTE (Long Term Evolution) and regional Geo-Mobile Satellite Services (MSS) [1]. Within a country the inter-system interference is minimized through its national-level coordination, which ensures that the frequencies used for both systems are mutually exclusive. However, other countries (including neighbouring) can independently choose to use this band for either LTE or MSS, resulting in interference to systems of both countries. This paper proposes a novel method to estimate aggregate interference from LTE terrestrial services on S band Geo-MSS return (user to satellite) and forward (satellite to user) links. The results of interference analysis are presented and it is shown that MSS forward and return links of a particular countr...
This chapter provides several multiple choice questions including their answers with explanations... more This chapter provides several multiple choice questions including their answers with explanations, related to microwave active devices and circuits for communication systems and subsystems.
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), 2019
Pulse Repetition Interval (PRI) timing and its modulation types are significant features of any R... more Pulse Repetition Interval (PRI) timing and its modulation types are significant features of any Radar to comprehend its capabilities and functionalities. In this paper, an algorithm has been proposed to classify PRI modulation by estimating features from time of arrival (ToA) and its difference (dToA) of a pulse radar. Performance of the proposed algorithm is also verified for different PRI modulations with different percentage of missing pulses. PRI modulation type classified covers Dwell and Switch (DS) of 2 to 64 level, Staggered PRI of 2 to 64 levels, Jittered PRI with 20% Gaussian deviation and Sliding PRI. Estimation of features is improved by selection of an optimal window of histogram. Level of staggered/ DS PRI has also been estimated using Kernel Density Estimator (KDE) with an epanechnikov window with length $N^{0.8}$ where, N is total count of dToA. Upon classification, PRI estimation for each modulation type is also estimated.
Narrowband interference, such as tone signal or low data rate modulated signal, can jam the commu... more Narrowband interference, such as tone signal or low data rate modulated signal, can jam the communication link or degrade the performance of the communication link. It is, therefore, essential to develop a system to detect the presence of interference in communication payload onboard system susceptible to such types of interference. This paper aims at hardware implementation of frequency-domain narrowband interference detection scheme in a wideband spectrum. The performance of this scheme is analysed using Receiver Operating Characteristics (ROC), Probability of False Alarm (\(P_{\text {fa}}\)) and Probability of Detection (\(P_{\text {d}}\)). The detection scheme is implemented on Xilinx Virtex-7 FPGA board. Simulation and hardware results for tone signal or modulated signal are presented in the paper. The proposed scheme is suitable for digital processor which is employed in processing types of communication payloads.
This chapter presents the working principle, design and analysis of various types of microwave fr... more This chapter presents the working principle, design and analysis of various types of microwave frequency mixers based on diodes and transistors for communication systems. Noise performance analysis and importance of image reject filters in the design of mixers are discussed. Design details and analysis of single-ended, single-balanced, double-balanced, image reject and subharmonic mixers are also presented along with examples.
This paper presents Communication Blackout during Reentry and its Mitigation using High Frequency... more This paper presents Communication Blackout during Reentry and its Mitigation using High Frequency Method
2014 International Conference on Electronics, Communication and Computational Engineering (ICECCE), 2014
High Power Amplifier in wireless communication systems exhibit nonlinear behavior which causes si... more High Power Amplifier in wireless communication systems exhibit nonlinear behavior which causes signal degradation. This is detrimental to the signals that pass through it. It appears in the form of Harmonic distortion, Gain compression, Inter-modulation distortion, Phase distortion, adjacent channel interference, etc. Orthogonal frequency-division multiplexing (OFDM) is considered to be better techniques for multicarrier wireless communication. It has tolerance to inter-symbol interference and good spectral efficiency but are subjected to nonlinearities of power amplifiers, due to their high peak-to-average power ratio (PAPR). In this paper, some of the basic PAPR reduction techniques like: Peak clipping, random phase shifting, selected mapping (SLM) and dummy sequence insertion (DSI) methods have been discussed. The results obtained has been compared with original PAPR which suggests improvement in nonlinearity with modest reduction in efficiency and increase in hardware implementations. Among the various techniques SLM method gives low PAPR than other methods.
IEEE Microwave and Wireless Components Letters, 2013
ABSTRACT This letter presents temperature behavior and compensation technique of Schottky diode a... more ABSTRACT This letter presents temperature behavior and compensation technique of Schottky diode and p-i-n diode based pre-distortion linearizer operating at microwave frequency. We have theoretically analyzed and experimentally demonstrated the temperature behavior of the linearizer and proposed a simple but effective temperature compensation technique. The proposed temperature compensation technique provides temperature dependent control bias to the diodes to achieve temperature invariant amplitude and phase expansion of the linearizer. Here design, simulation and test results of a temperature compensated linearizer is presented that compensates amplitude and phase variation from 6 dB and 50 to less than 0.7 dB and 4.5deg
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), 2019
To cater to the exponential growth of terrestrial mobile services, several frequency bands have b... more To cater to the exponential growth of terrestrial mobile services, several frequency bands have been included for use in International Mobile Telecommunications (IMT). Consequently, the 2500-2690 MHz frequency band is now being shared between Band 41 of 4G-LTE (Long Term Evolution) and regional Geo-Mobile Satellite Services (MSS) [1]. Within a country the inter-system interference is minimized through its national-level coordination, which ensures that the frequencies used for both systems are mutually exclusive. However, other countries (including neighbouring) can independently choose to use this band for either LTE or MSS, resulting in interference to systems of both countries. This paper proposes a novel method to estimate aggregate interference from LTE terrestrial services on S band Geo-MSS return (user to satellite) and forward (satellite to user) links. The results of interference analysis are presented and it is shown that MSS forward and return links of a particular countr...
This chapter provides several multiple choice questions including their answers with explanations... more This chapter provides several multiple choice questions including their answers with explanations, related to microwave active devices and circuits for communication systems and subsystems.
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC), 2019
Pulse Repetition Interval (PRI) timing and its modulation types are significant features of any R... more Pulse Repetition Interval (PRI) timing and its modulation types are significant features of any Radar to comprehend its capabilities and functionalities. In this paper, an algorithm has been proposed to classify PRI modulation by estimating features from time of arrival (ToA) and its difference (dToA) of a pulse radar. Performance of the proposed algorithm is also verified for different PRI modulations with different percentage of missing pulses. PRI modulation type classified covers Dwell and Switch (DS) of 2 to 64 level, Staggered PRI of 2 to 64 levels, Jittered PRI with 20% Gaussian deviation and Sliding PRI. Estimation of features is improved by selection of an optimal window of histogram. Level of staggered/ DS PRI has also been estimated using Kernel Density Estimator (KDE) with an epanechnikov window with length $N^{0.8}$ where, N is total count of dToA. Upon classification, PRI estimation for each modulation type is also estimated.
Narrowband interference, such as tone signal or low data rate modulated signal, can jam the commu... more Narrowband interference, such as tone signal or low data rate modulated signal, can jam the communication link or degrade the performance of the communication link. It is, therefore, essential to develop a system to detect the presence of interference in communication payload onboard system susceptible to such types of interference. This paper aims at hardware implementation of frequency-domain narrowband interference detection scheme in a wideband spectrum. The performance of this scheme is analysed using Receiver Operating Characteristics (ROC), Probability of False Alarm (\(P_{\text {fa}}\)) and Probability of Detection (\(P_{\text {d}}\)). The detection scheme is implemented on Xilinx Virtex-7 FPGA board. Simulation and hardware results for tone signal or modulated signal are presented in the paper. The proposed scheme is suitable for digital processor which is employed in processing types of communication payloads.
This chapter presents the working principle, design and analysis of various types of microwave fr... more This chapter presents the working principle, design and analysis of various types of microwave frequency mixers based on diodes and transistors for communication systems. Noise performance analysis and importance of image reject filters in the design of mixers are discussed. Design details and analysis of single-ended, single-balanced, double-balanced, image reject and subharmonic mixers are also presented along with examples.
This paper presents Communication Blackout during Reentry and its Mitigation using High Frequency... more This paper presents Communication Blackout during Reentry and its Mitigation using High Frequency Method
2014 International Conference on Electronics, Communication and Computational Engineering (ICECCE), 2014
High Power Amplifier in wireless communication systems exhibit nonlinear behavior which causes si... more High Power Amplifier in wireless communication systems exhibit nonlinear behavior which causes signal degradation. This is detrimental to the signals that pass through it. It appears in the form of Harmonic distortion, Gain compression, Inter-modulation distortion, Phase distortion, adjacent channel interference, etc. Orthogonal frequency-division multiplexing (OFDM) is considered to be better techniques for multicarrier wireless communication. It has tolerance to inter-symbol interference and good spectral efficiency but are subjected to nonlinearities of power amplifiers, due to their high peak-to-average power ratio (PAPR). In this paper, some of the basic PAPR reduction techniques like: Peak clipping, random phase shifting, selected mapping (SLM) and dummy sequence insertion (DSI) methods have been discussed. The results obtained has been compared with original PAPR which suggests improvement in nonlinearity with modest reduction in efficiency and increase in hardware implementations. Among the various techniques SLM method gives low PAPR than other methods.
IEEE Microwave and Wireless Components Letters, 2013
ABSTRACT This letter presents temperature behavior and compensation technique of Schottky diode a... more ABSTRACT This letter presents temperature behavior and compensation technique of Schottky diode and p-i-n diode based pre-distortion linearizer operating at microwave frequency. We have theoretically analyzed and experimentally demonstrated the temperature behavior of the linearizer and proposed a simple but effective temperature compensation technique. The proposed temperature compensation technique provides temperature dependent control bias to the diodes to achieve temperature invariant amplitude and phase expansion of the linearizer. Here design, simulation and test results of a temperature compensated linearizer is presented that compensates amplitude and phase variation from 6 dB and 50 to less than 0.7 dB and 4.5deg
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