Ultra-wideband (UWB) radios provide avenues for interference immunity using spread spectrum (SS) ... more Ultra-wideband (UWB) radios provide avenues for interference immunity using spread spectrum (SS) techniques. Doing so, provides a processing gain of 21 dB, allowing for successful retrieval of signals propagated below the noise floor. In addition, by applying advanced channel coding an additional coding gain of 9 dB can be achieved. In this paper, we are exploiting SS techniques with channel coding to maximize gain in wireless communication links. Bit error rate (BER) performance is presented for multiple channel coding approaches.
2021 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (APS/URSI), Dec 4, 2021
Spectrum scarcity in a highly congested radio environment call for simultaneous transmit and rece... more Spectrum scarcity in a highly congested radio environment call for simultaneous transmit and receive (STAR) radios. A key challenge in STAR radios is the self-interference cancellation (SIC) of the signals that leak from the transmitter into the receiver. With this in mind, this paper presents an ultra-wideband (UWB) RF-SIC filter capable of more than 20dB cancellation across 1GHz bandwidth. This SIC is part of a multistage cancellation scheme achieving more than 100dB of STAR isolation. Our presented SIC employs a filter bank with weight optimization to reach the noted unprecedented bandwidth. This design ensures phase linearity estimating the minimum number of filter stages. For optimization, a discrete-gradient descent algorithm is used to arrive at a practical SIC filter bank.
Communication links are vulnerable to signal fratricide and intentional interference. Therefore, ... more Communication links are vulnerable to signal fratricide and intentional interference. Therefore, there is a strong interest for interference resistant links to enable secure communication protocols. One way to achieve interference immunity is by exploiting Spread Spectrum (SS) coding techniques with significant coding gain. With access to large bandwidth, it is now possible to spread the signal below the noise floor and secure reliable communication. The focus of this paper is to present a Direct Sequence Spread Spectrum – Binary Phase Shift Keying (DSSS-BPSK) modulation link with over 1 GHz signal bandwidth, in presence of collocated multiple high power interferers. It is observed that DSSS results in better bit error rate (BER) performance. This improvement was in presence of an interferer-signal (I/S) ratio of 34.34 dB.
2018 IEEE International Conference on Probabilistic Methods Applied to Power Systems (PMAPS), 2018
This paper proposes an algorithm to incorporate the reliability network equivalent concept into r... more This paper proposes an algorithm to incorporate the reliability network equivalent concept into reliability assessment of complex radial distribution networks (RDNs). Using this concept, there is no need to analyze the system response to every single contingency. Instead, the equivalent impact of a group of contingencies is used to decrease the network dimension. In the proposed algorithm, the reduction takes place at protection zones. The topology of the network is given in matrix form. In different steps, this matrix is modified to derive new matrices, which are then used to perform network reduction, fault isolation, upstream and downstream restoration, and integration of the unsuccessful operation of protective devices. Use of the matrix form makes the algorithm straightforward to implement. The Roy Billinton Test System (RBTS) is used to validate computational efficiency of the proposed algorithm.
2021 IEEE Applied Power Electronics Conference and Exposition (APEC), 2021
In this paper, a constant switching frequency Finite Control Set Modulated Model Predictive Contr... more In this paper, a constant switching frequency Finite Control Set Modulated Model Predictive Control (FCS-M2PC) is proposed for a single phase 5-level flying capacitor multilevel converter with an output LC filter operating as an Uninterruptible Power Supply (UPS). In the proposed method, first Finite Control Set Model Predictive Control (FCS-MPC) is used to generate the reference voltage by inspecting all the possible converter output voltages taking into account the control delay. Then, the generated reference is applied to a modulator operating with Phase Shifted Pulse Width Modulation (PSPWM) scheme. The application to the modulator ensures a constant output switching frequency and proper voltage balancing of the flying capacitors (FCs’). The proposed method is easy to implement and provides a fast dynamic response, robustness to the load change, constant switching frequency, and decreases the computational burden of traditional FCS-MPC. Finally, the performance of the FCS-M2PC is verified by implementing different scenarios on a experimental setup and the results are presented.
2013 IEEE PES Innovative Smart Grid Technologies Conference (ISGT), 2013
ABSTRACT Effective interconnection of stochastically variable renewable energy resources like sol... more ABSTRACT Effective interconnection of stochastically variable renewable energy resources like solar PV (photovoltaic) systems to the grid requires meticulous attention to ensure system compatibility, stability and reliability. The operating characteristics of such PV power plants need to become familiar to power systems engineers and operators. Such familiarity can effectively be achieved only via system modeling, simulation and experimental studies. This paper develops models for an integrated PV power plant which comprises PV array, SEPIC (single ended primary inductance converter) converter, bi-directional de-de converter, dc-ac converter, and battery energy storage system using Matlab/Simulink. The models are used for simulation studies to investigate: 1) the response of the system to the ever-changing environmental variables, 2) the ability to track the maximum power point, 3) the role of the battery energy storage in the mitigation of voltage and power oscillations and 4) the role of the inverter in ensuring compliance to the grid requirements. Experimentally, a DSP (digital signal processing) based control system for maximum power point tracking, dc bus voltage regulation, battery charge/discharge control, dc-ac converter control, system synchronization and protection is implemented and used for the validation of the simulation studies. The simulation and experimental results are presented and discussed.
We argue that the spontaneous creation of de Sitter universes favors three spatial dimensions. Th... more We argue that the spontaneous creation of de Sitter universes favors three spatial dimensions. The conclusion relies on the causal-patch description of de Sitter space, where fiducial observers experience local thermal equilibrium up to a stretched horizon, on the holographic principle, and on some assumptions about the nature of gravity and the constituents of Hawking/Unruh radiation.
We argue that a theoretical upper bound exists on the cutoff of any effective theory that describ... more We argue that a theoretical upper bound exists on the cutoff of any effective theory that describes an electromagnetically interacting massive higher spin field in at space. The cutoff is a simple function of the particle's mass, spin and electric charge, and cannot be arbitrarily high. In the spirit of effective field theory, this bound is independent of any possible UV completion of the theory, such as string theory. A systematic study to quantify the degree of singularity of the massless limit is made with the help of the Stuuckelberg formalism. For spin 2, we find that the cutoff upper bound is Λ2 ˜ me -1/3. By demonstrating the existence of cohomological obstructions and presenting arguments involving physical processes, we prove that indeed the cutoff cannot be higher. We show that the existence of a cutoff is connected to other pathologies of the system, such as the Velo-Zwanziger acausality. In particular, we argue that, for a judicious choice of non-minimal interaction ...
Ultra-wideband (UWB) radios provide avenues for interference immunity using spread spectrum (SS) ... more Ultra-wideband (UWB) radios provide avenues for interference immunity using spread spectrum (SS) techniques. Doing so, provides a processing gain of 21 dB, allowing for successful retrieval of signals propagated below the noise floor. In addition, by applying advanced channel coding an additional coding gain of 9 dB can be achieved. In this paper, we are exploiting SS techniques with channel coding to maximize gain in wireless communication links. Bit error rate (BER) performance is presented for multiple channel coding approaches.
2021 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (APS/URSI), Dec 4, 2021
Spectrum scarcity in a highly congested radio environment call for simultaneous transmit and rece... more Spectrum scarcity in a highly congested radio environment call for simultaneous transmit and receive (STAR) radios. A key challenge in STAR radios is the self-interference cancellation (SIC) of the signals that leak from the transmitter into the receiver. With this in mind, this paper presents an ultra-wideband (UWB) RF-SIC filter capable of more than 20dB cancellation across 1GHz bandwidth. This SIC is part of a multistage cancellation scheme achieving more than 100dB of STAR isolation. Our presented SIC employs a filter bank with weight optimization to reach the noted unprecedented bandwidth. This design ensures phase linearity estimating the minimum number of filter stages. For optimization, a discrete-gradient descent algorithm is used to arrive at a practical SIC filter bank.
Communication links are vulnerable to signal fratricide and intentional interference. Therefore, ... more Communication links are vulnerable to signal fratricide and intentional interference. Therefore, there is a strong interest for interference resistant links to enable secure communication protocols. One way to achieve interference immunity is by exploiting Spread Spectrum (SS) coding techniques with significant coding gain. With access to large bandwidth, it is now possible to spread the signal below the noise floor and secure reliable communication. The focus of this paper is to present a Direct Sequence Spread Spectrum – Binary Phase Shift Keying (DSSS-BPSK) modulation link with over 1 GHz signal bandwidth, in presence of collocated multiple high power interferers. It is observed that DSSS results in better bit error rate (BER) performance. This improvement was in presence of an interferer-signal (I/S) ratio of 34.34 dB.
2018 IEEE International Conference on Probabilistic Methods Applied to Power Systems (PMAPS), 2018
This paper proposes an algorithm to incorporate the reliability network equivalent concept into r... more This paper proposes an algorithm to incorporate the reliability network equivalent concept into reliability assessment of complex radial distribution networks (RDNs). Using this concept, there is no need to analyze the system response to every single contingency. Instead, the equivalent impact of a group of contingencies is used to decrease the network dimension. In the proposed algorithm, the reduction takes place at protection zones. The topology of the network is given in matrix form. In different steps, this matrix is modified to derive new matrices, which are then used to perform network reduction, fault isolation, upstream and downstream restoration, and integration of the unsuccessful operation of protective devices. Use of the matrix form makes the algorithm straightforward to implement. The Roy Billinton Test System (RBTS) is used to validate computational efficiency of the proposed algorithm.
2021 IEEE Applied Power Electronics Conference and Exposition (APEC), 2021
In this paper, a constant switching frequency Finite Control Set Modulated Model Predictive Contr... more In this paper, a constant switching frequency Finite Control Set Modulated Model Predictive Control (FCS-M2PC) is proposed for a single phase 5-level flying capacitor multilevel converter with an output LC filter operating as an Uninterruptible Power Supply (UPS). In the proposed method, first Finite Control Set Model Predictive Control (FCS-MPC) is used to generate the reference voltage by inspecting all the possible converter output voltages taking into account the control delay. Then, the generated reference is applied to a modulator operating with Phase Shifted Pulse Width Modulation (PSPWM) scheme. The application to the modulator ensures a constant output switching frequency and proper voltage balancing of the flying capacitors (FCs’). The proposed method is easy to implement and provides a fast dynamic response, robustness to the load change, constant switching frequency, and decreases the computational burden of traditional FCS-MPC. Finally, the performance of the FCS-M2PC is verified by implementing different scenarios on a experimental setup and the results are presented.
2013 IEEE PES Innovative Smart Grid Technologies Conference (ISGT), 2013
ABSTRACT Effective interconnection of stochastically variable renewable energy resources like sol... more ABSTRACT Effective interconnection of stochastically variable renewable energy resources like solar PV (photovoltaic) systems to the grid requires meticulous attention to ensure system compatibility, stability and reliability. The operating characteristics of such PV power plants need to become familiar to power systems engineers and operators. Such familiarity can effectively be achieved only via system modeling, simulation and experimental studies. This paper develops models for an integrated PV power plant which comprises PV array, SEPIC (single ended primary inductance converter) converter, bi-directional de-de converter, dc-ac converter, and battery energy storage system using Matlab/Simulink. The models are used for simulation studies to investigate: 1) the response of the system to the ever-changing environmental variables, 2) the ability to track the maximum power point, 3) the role of the battery energy storage in the mitigation of voltage and power oscillations and 4) the role of the inverter in ensuring compliance to the grid requirements. Experimentally, a DSP (digital signal processing) based control system for maximum power point tracking, dc bus voltage regulation, battery charge/discharge control, dc-ac converter control, system synchronization and protection is implemented and used for the validation of the simulation studies. The simulation and experimental results are presented and discussed.
We argue that the spontaneous creation of de Sitter universes favors three spatial dimensions. Th... more We argue that the spontaneous creation of de Sitter universes favors three spatial dimensions. The conclusion relies on the causal-patch description of de Sitter space, where fiducial observers experience local thermal equilibrium up to a stretched horizon, on the holographic principle, and on some assumptions about the nature of gravity and the constituents of Hawking/Unruh radiation.
We argue that a theoretical upper bound exists on the cutoff of any effective theory that describ... more We argue that a theoretical upper bound exists on the cutoff of any effective theory that describes an electromagnetically interacting massive higher spin field in at space. The cutoff is a simple function of the particle's mass, spin and electric charge, and cannot be arbitrarily high. In the spirit of effective field theory, this bound is independent of any possible UV completion of the theory, such as string theory. A systematic study to quantify the degree of singularity of the massless limit is made with the help of the Stuuckelberg formalism. For spin 2, we find that the cutoff upper bound is Λ2 ˜ me -1/3. By demonstrating the existence of cohomological obstructions and presenting arguments involving physical processes, we prove that indeed the cutoff cannot be higher. We show that the existence of a cutoff is connected to other pathologies of the system, such as the Velo-Zwanziger acausality. In particular, we argue that, for a judicious choice of non-minimal interaction ...
Uploads
Papers by Rakibur Rahman