We consider discrete-time (DT) systems S in which a DT input is first tranformed to a continuous-... more We consider discrete-time (DT) systems S in which a DT input is first tranformed to a continuous-time (CT) format by phase-amplitude modulation, then modified by a non-linear CT dynamical transformation F, and finally converted back to DT output using an ideal de-modulation scheme. Assuming that F belongs to a special class of CT Volterra series models with fixed degree and memory depth, we provide a complete characterization of S as a series connection of a DT Volterra series model of fixed degree and memory depth, and an LTI system with special properties. The result suggests a new, non-obvious, analytically motivated structure of digital compensation of analog nonlinear distortions (for example, those caused by power amplifiers) in digital communication systems. Results from a MATLAB simulation are used to demonstrate effectiveness of the new compensation scheme, as compared to the standard Volterra series approach.
We consider baseband equivalent representation of transmission circuits, in the form of a nonline... more We consider baseband equivalent representation of transmission circuits, in the form of a nonlinear dynamical system S in discrete time (DT) defined by a series interconnection of a phase-amplitude modulator, a nonlinear dynamical system F in continuous time (CT), and an ideal demodulator. We show that when F is a CT Volterra series model, the resulting S is a series interconnection of a DT Volterra series model of same degree and memory depth, and an LTI system with special properties. The result suggests a new, non-obvious, analytically motivated structure of digital pre-compensation of analog nonlinear distortions such as those caused by power amplifiers in digital communication systems. The baseband model and the corresponding digital compensation structure readily extend to OFDM modulation. MATLAB simulation is used to verify proposed baseband equivalent model and demonstrate effectiveness of the new compensation scheme, as compared to the standard Volterra series approach.
Abstract. In Internet based laboratory (I-Lab), the lab devices and pilot plants are tested, cont... more Abstract. In Internet based laboratory (I-Lab), the lab devices and pilot plants are tested, controlled and programmed through a client program or standard web browser at remote computer. Control panels of HMI interface and user-controlled webcam allow monitoring the measurement devices or test plant behavior providing visual and audio feedback. As an online lab can be used from many locations and at any time, it can be utilized much more than a conventional lab in omni present omni tempore fashion. The paper presents such online Internet accessible laboratory built at the Faculty of Electrical Engineering in Sarajevo within the laboratory for HMI/SCADA systems. Web enabled HMI software with OPC communication to PLC controller is used to provide full monitoring and control to remote user, while integrated videoconferencing software is used to implement the rest of the functionalities.
We consider discrete-time (DT) systems S in which a DT input is first tranformed to a continuous-... more We consider discrete-time (DT) systems S in which a DT input is first tranformed to a continuous-time (CT) format by phase-amplitude modulation, then modified by a non-linear CT dynamical transformation F, and finally converted back to DT output using an ideal de-modulation scheme. Assuming that F belongs to a special class of CT Volterra series models with fixed degree and memory depth, we provide a complete characterization of S as a series connection of a DT Volterra series model of fixed degree and memory depth, and an LTI system with special properties. The result suggests a new, non-obvious, analytically motivated structure of digital compensation of analog nonlinear distortions (for example, those caused by power amplifiers) in digital communi-cation systems. Results from a MATLAB simulation are used to demonstrate effectiveness of the new compensation scheme, as compared to the standard Volterra series approach.
2017 47th European Microwave Conference (EuMC), 2017
In recent years, carrier based pulse-width modulation (PWM) has been extensively used for reducin... more In recent years, carrier based pulse-width modulation (PWM) has been extensively used for reducing input signal resolution in all-digital transmitters, and is known to provide better coding efficiency than other power encoding methods, e.g. delta-sigma modulation (DSM). Unfortunately, high levels of in-band distortion introduced by fully digitally implemented PWM, limit its usage in transceivers realized for software defined radio. In this paper, we exploit time-domain characterization of digital PWM in-band distortion, and propose a multilevel power encoding scheme based on DSM-PWM hybrid architecture with carefully selected design parameters, which enable optimal in-band distortion cancellation with low hardware complexity. Experiments with an arbitrary waveform generator are used to demonstrate effectiveness of the proposed novel power encoding scheme, and are compared with a standard multilevel PWM. The novel power encoding scheme offers −20dB improvement in SNR, while maintaini...
2017 IEEE 60th International Midwest Symposium on Circuits and Systems (MWSCAS), 2017
Pulse-width modulation (PWM) has been extensively used in switched converter systems, and recentl... more Pulse-width modulation (PWM) has been extensively used in switched converter systems, and recently in RF applications, due to an increased interest in all-digital transmitters. These architectures employ high efficiency switched-mode power amplifiers (SMPA), where PWM is commonly used to generate the PA driving signal. However, digitally implemented PWM introduces large amount of in-band distortion, which is traditionally explained by spectral aliasing. In this paper we derive a novel closed-form time-domain expression for the output signal of a multilevel carrier-based digital PWM, driven by an arbitrary bounded input signal. We show that the spectral aliasing effects are equivalent to amplitude quantization of the PWM input signal, and give theoretical bounds on the output signal resolution for a given PWM scheme. Parameters of this quantization process are determined, and their dependence on PWM design specifications is shown. Numerical simulations in MATLAB were used to verify d...
2017 IEEE Asia Pacific Microwave Conference (APMC), 2017
Pulse-width modulation (PWM) has recently become very popular power encoding method in all-digita... more Pulse-width modulation (PWM) has recently become very popular power encoding method in all-digital transmitter (ADT) architectures, which employ switch-mode power amplifiers (SMPA) for high power efficiency. Main drawback of PWM is high level of in-band harmonic distortion when digitally implemented, which limits its usage in transceivers realized for software defined radio. Furthermore, upconversion to RF frequency in such ADT systems is commonly done in digital domain. This introduces additional design difficulties, since significant amount of out-of-band harmonic noise, originating from PWM power encoding process, gets folded back into the input signal frequency band, further increasing the total in-band distortion. This paper presents a novel method for simultaneous multilevel power encoding and upconversion to RF frequency, by the means of a ΔΣM-PWM hybrid architecture. It fully exploits time-domain characterization of multilevel carrier-based digital PWM, to both provide optim...
This paper presents a novel method for multilevel power coding and upconversion to RF frequency, ... more This paper presents a novel method for multilevel power coding and upconversion to RF frequency, by the means of a digital radio-frequency pulse width modulation (RF-PWM). Delta-sigma modulation (ΔΣM) and memoryless predistortion are used to mitigate spectral aliasing effects, inherent to digital RF-PWM operation, and achieve high linearity of the transmitter. In this method, time-domain characterization of a multilevel digital RF-PWM was fully exploited in order to provide optimal parameter selection for the ΔΣM, which in turn enables aliasing-free digital RF-PWM that runs at reasonable clock speeds. Experiments with an arbitrary waveform generator are used to demonstrate effectiveness of the proposed novel power encoding scheme. The novel algorithm offers in-band SNR of —45dB, while maintaining coding efficiency of about 55%, for a 20MHz-bandwidth 64QAM signal, while mere RF-PWM, running at the same clock speed, can achieve SNR of only — 10dB.
We consider baseband equivalent representation of transmission circuits, in the form of a nonline... more We consider baseband equivalent representation of transmission circuits, in the form of a nonlinear dynamical system $\mathbf S$ in discrete time (DT) defined by a series interconnection of a phase-amplitude modulator, a nonlinear dynamical system $\mathbf F$ in continuous time (CT), and an ideal demodulator. We show that when $\mathbf F$ is a CT Volterra series model, the resulting $\mathbf S$ is a series interconnection of a DT Volterra series model of same degree and memory depth, and an LTI system with special properties. The result suggests a new, non-obvious, analytically motivated structure of digital pre-compensation of analog nonlinear distortions such as those caused by power amplifiers in digital communication systems. The baseband model and the corresponding digital compensation structure readily extend to OFDM modulation. MATLAB simulation is used to verify proposed baseband equivalent model and demonstrate effectiveness of the new compensation scheme, as compared to th...
We consider discrete-time (DT) systems S in which a DT input is first transformed to a continuous... more We consider discrete-time (DT) systems S in which a DT input is first transformed to a continuous-time (CT) format by phase-amplitude modulation, then modified by a non-linear CT dynamical transformation F, and finally converted back to DT output using an ideal de-modulation scheme. Assuming that F belongs to a special class of CT Volterra series models with fixed degree and memory depth, we provide a complete characterization of S as a series connection of a DT Volterra series model of fixed degree and memory depth, and an LTI system with special properties. The result suggests a new, non-obvious, analytically motivated structure of digital compensation of analog nonlinear distortions (for example, those caused by power amplifiers) in digital communication systems. We also argue that this baseband model, and its corresponding digital compensation structure, can be readily extended to OFDM modulation. Results from a MATLAB simulation are used to demonstrate effectiveness of the new ...
In this paper, we propose a power encoding method for converting a high-resolution OFDM baseband ... more In this paper, we propose a power encoding method for converting a high-resolution OFDM baseband signal into a signal that assumes only a finite number of values. This is achieved by the series interconnection of, optimally (co)designed, delta- sigma (/spl Delta/ /Spl Sigma/M) and digital pulse-width modulators (DPWM). Given an input signal class with a known mplitude distribution (e.g., OFDM), parameters of the multilevel DPWM are designed such that the mean squared error of the inherent DPWM quantization noise is inimized. Parameters of the /spl Delta/ /Spl Sigma/M are then chosen with respect to the designed DPWM, so to optimally shape the inherent quantization noise out of the spectral band of interest. The superior performance of the proposed novel power encoding scheme is demonstrated by Matlab simulations on several standardized LTE test signals.
In this paper, we consider a problem of designing discrete-time systems which are optimal in freq... more In this paper, we consider a problem of designing discrete-time systems which are optimal in frequency-weighted least squares sense subject to a maximal output amplitude constraint. In such problems, the optimality conditions do not provide an explicit way of generating the optimal output as a real-time implementable transformation of the input, due to causal instability of the resulting dynamical equations and sequential nature in which criterion function is revealed over time. On the other hand, under some mild conditions, the optimal system has exponentially fading memory which suggests existence of arbitrarily good finite-latency approximations. In this paper, we extend the method of balanced truncation for linear systems to the class of nonlinear models with weakly contractive operators. We then propose a causally stable finite-latency nonlinear system which returns high-quality approximations to the optimal map. The proposed system is obtained by a careful truncation of an infinite dimensional state space representation of the optimal system, as suggested by the derived generalization of the balanced truncation algorithm.
2018 IEEE International Symposium on Circuits and Systems (ISCAS), 2018
Radio frequency pulse-width modulation (RF-PWM) has been used as a power coding method in all-dig... more Radio frequency pulse-width modulation (RF-PWM) has been used as a power coding method in all-digital transmitters, which employ highly efficient switched-mode power amplifiers (SMPA). The main drawback of RF-PWM is the high level of in-band harmonic distortion when digitally implemented. In order to reduce spectral aliasing effects and produce acceptable levels of harmonic noise, ultra-fast clock speeds are required, making it commercially infeasible. In this paper, we derive a novel compact analytical model of a multilevel digital RF-PWM, driven by an arbitrary bounded baseband signal. We show that the spectral aliasing effects are equivalent to a particular amplitude quantization of the input baseband signal. This result implies that highly linear digital RF-PWM can be realized with modest clock speeds if and only if the input baseband signal is pre-quantized according to the inherent quantization process. We provide full description of this quantization process and describe its ...
We consider discrete-time (DT) systems S in which a DT input is first tranformed to a continuous-... more We consider discrete-time (DT) systems S in which a DT input is first tranformed to a continuous-time (CT) format by phase-amplitude modulation, then modified by a non-linear CT dynamical transformation F, and finally converted back to DT output using an ideal de-modulation scheme. Assuming that F belongs to a special class of CT Volterra series models with fixed degree and memory depth, we provide a complete characterization of S as a series connection of a DT Volterra series model of fixed degree and memory depth, and an LTI system with special properties. The result suggests a new, non-obvious, analytically motivated structure of digital compensation of analog nonlinear distortions (for example, those caused by power amplifiers) in digital communication systems. Results from a MATLAB simulation are used to demonstrate effectiveness of the new compensation scheme, as compared to the standard Volterra series approach.
We consider baseband equivalent representation of transmission circuits, in the form of a nonline... more We consider baseband equivalent representation of transmission circuits, in the form of a nonlinear dynamical system S in discrete time (DT) defined by a series interconnection of a phase-amplitude modulator, a nonlinear dynamical system F in continuous time (CT), and an ideal demodulator. We show that when F is a CT Volterra series model, the resulting S is a series interconnection of a DT Volterra series model of same degree and memory depth, and an LTI system with special properties. The result suggests a new, non-obvious, analytically motivated structure of digital pre-compensation of analog nonlinear distortions such as those caused by power amplifiers in digital communication systems. The baseband model and the corresponding digital compensation structure readily extend to OFDM modulation. MATLAB simulation is used to verify proposed baseband equivalent model and demonstrate effectiveness of the new compensation scheme, as compared to the standard Volterra series approach.
Abstract. In Internet based laboratory (I-Lab), the lab devices and pilot plants are tested, cont... more Abstract. In Internet based laboratory (I-Lab), the lab devices and pilot plants are tested, controlled and programmed through a client program or standard web browser at remote computer. Control panels of HMI interface and user-controlled webcam allow monitoring the measurement devices or test plant behavior providing visual and audio feedback. As an online lab can be used from many locations and at any time, it can be utilized much more than a conventional lab in omni present omni tempore fashion. The paper presents such online Internet accessible laboratory built at the Faculty of Electrical Engineering in Sarajevo within the laboratory for HMI/SCADA systems. Web enabled HMI software with OPC communication to PLC controller is used to provide full monitoring and control to remote user, while integrated videoconferencing software is used to implement the rest of the functionalities.
We consider discrete-time (DT) systems S in which a DT input is first tranformed to a continuous-... more We consider discrete-time (DT) systems S in which a DT input is first tranformed to a continuous-time (CT) format by phase-amplitude modulation, then modified by a non-linear CT dynamical transformation F, and finally converted back to DT output using an ideal de-modulation scheme. Assuming that F belongs to a special class of CT Volterra series models with fixed degree and memory depth, we provide a complete characterization of S as a series connection of a DT Volterra series model of fixed degree and memory depth, and an LTI system with special properties. The result suggests a new, non-obvious, analytically motivated structure of digital compensation of analog nonlinear distortions (for example, those caused by power amplifiers) in digital communi-cation systems. Results from a MATLAB simulation are used to demonstrate effectiveness of the new compensation scheme, as compared to the standard Volterra series approach.
2017 47th European Microwave Conference (EuMC), 2017
In recent years, carrier based pulse-width modulation (PWM) has been extensively used for reducin... more In recent years, carrier based pulse-width modulation (PWM) has been extensively used for reducing input signal resolution in all-digital transmitters, and is known to provide better coding efficiency than other power encoding methods, e.g. delta-sigma modulation (DSM). Unfortunately, high levels of in-band distortion introduced by fully digitally implemented PWM, limit its usage in transceivers realized for software defined radio. In this paper, we exploit time-domain characterization of digital PWM in-band distortion, and propose a multilevel power encoding scheme based on DSM-PWM hybrid architecture with carefully selected design parameters, which enable optimal in-band distortion cancellation with low hardware complexity. Experiments with an arbitrary waveform generator are used to demonstrate effectiveness of the proposed novel power encoding scheme, and are compared with a standard multilevel PWM. The novel power encoding scheme offers −20dB improvement in SNR, while maintaini...
2017 IEEE 60th International Midwest Symposium on Circuits and Systems (MWSCAS), 2017
Pulse-width modulation (PWM) has been extensively used in switched converter systems, and recentl... more Pulse-width modulation (PWM) has been extensively used in switched converter systems, and recently in RF applications, due to an increased interest in all-digital transmitters. These architectures employ high efficiency switched-mode power amplifiers (SMPA), where PWM is commonly used to generate the PA driving signal. However, digitally implemented PWM introduces large amount of in-band distortion, which is traditionally explained by spectral aliasing. In this paper we derive a novel closed-form time-domain expression for the output signal of a multilevel carrier-based digital PWM, driven by an arbitrary bounded input signal. We show that the spectral aliasing effects are equivalent to amplitude quantization of the PWM input signal, and give theoretical bounds on the output signal resolution for a given PWM scheme. Parameters of this quantization process are determined, and their dependence on PWM design specifications is shown. Numerical simulations in MATLAB were used to verify d...
2017 IEEE Asia Pacific Microwave Conference (APMC), 2017
Pulse-width modulation (PWM) has recently become very popular power encoding method in all-digita... more Pulse-width modulation (PWM) has recently become very popular power encoding method in all-digital transmitter (ADT) architectures, which employ switch-mode power amplifiers (SMPA) for high power efficiency. Main drawback of PWM is high level of in-band harmonic distortion when digitally implemented, which limits its usage in transceivers realized for software defined radio. Furthermore, upconversion to RF frequency in such ADT systems is commonly done in digital domain. This introduces additional design difficulties, since significant amount of out-of-band harmonic noise, originating from PWM power encoding process, gets folded back into the input signal frequency band, further increasing the total in-band distortion. This paper presents a novel method for simultaneous multilevel power encoding and upconversion to RF frequency, by the means of a ΔΣM-PWM hybrid architecture. It fully exploits time-domain characterization of multilevel carrier-based digital PWM, to both provide optim...
This paper presents a novel method for multilevel power coding and upconversion to RF frequency, ... more This paper presents a novel method for multilevel power coding and upconversion to RF frequency, by the means of a digital radio-frequency pulse width modulation (RF-PWM). Delta-sigma modulation (ΔΣM) and memoryless predistortion are used to mitigate spectral aliasing effects, inherent to digital RF-PWM operation, and achieve high linearity of the transmitter. In this method, time-domain characterization of a multilevel digital RF-PWM was fully exploited in order to provide optimal parameter selection for the ΔΣM, which in turn enables aliasing-free digital RF-PWM that runs at reasonable clock speeds. Experiments with an arbitrary waveform generator are used to demonstrate effectiveness of the proposed novel power encoding scheme. The novel algorithm offers in-band SNR of —45dB, while maintaining coding efficiency of about 55%, for a 20MHz-bandwidth 64QAM signal, while mere RF-PWM, running at the same clock speed, can achieve SNR of only — 10dB.
We consider baseband equivalent representation of transmission circuits, in the form of a nonline... more We consider baseband equivalent representation of transmission circuits, in the form of a nonlinear dynamical system $\mathbf S$ in discrete time (DT) defined by a series interconnection of a phase-amplitude modulator, a nonlinear dynamical system $\mathbf F$ in continuous time (CT), and an ideal demodulator. We show that when $\mathbf F$ is a CT Volterra series model, the resulting $\mathbf S$ is a series interconnection of a DT Volterra series model of same degree and memory depth, and an LTI system with special properties. The result suggests a new, non-obvious, analytically motivated structure of digital pre-compensation of analog nonlinear distortions such as those caused by power amplifiers in digital communication systems. The baseband model and the corresponding digital compensation structure readily extend to OFDM modulation. MATLAB simulation is used to verify proposed baseband equivalent model and demonstrate effectiveness of the new compensation scheme, as compared to th...
We consider discrete-time (DT) systems S in which a DT input is first transformed to a continuous... more We consider discrete-time (DT) systems S in which a DT input is first transformed to a continuous-time (CT) format by phase-amplitude modulation, then modified by a non-linear CT dynamical transformation F, and finally converted back to DT output using an ideal de-modulation scheme. Assuming that F belongs to a special class of CT Volterra series models with fixed degree and memory depth, we provide a complete characterization of S as a series connection of a DT Volterra series model of fixed degree and memory depth, and an LTI system with special properties. The result suggests a new, non-obvious, analytically motivated structure of digital compensation of analog nonlinear distortions (for example, those caused by power amplifiers) in digital communication systems. We also argue that this baseband model, and its corresponding digital compensation structure, can be readily extended to OFDM modulation. Results from a MATLAB simulation are used to demonstrate effectiveness of the new ...
In this paper, we propose a power encoding method for converting a high-resolution OFDM baseband ... more In this paper, we propose a power encoding method for converting a high-resolution OFDM baseband signal into a signal that assumes only a finite number of values. This is achieved by the series interconnection of, optimally (co)designed, delta- sigma (/spl Delta/ /Spl Sigma/M) and digital pulse-width modulators (DPWM). Given an input signal class with a known mplitude distribution (e.g., OFDM), parameters of the multilevel DPWM are designed such that the mean squared error of the inherent DPWM quantization noise is inimized. Parameters of the /spl Delta/ /Spl Sigma/M are then chosen with respect to the designed DPWM, so to optimally shape the inherent quantization noise out of the spectral band of interest. The superior performance of the proposed novel power encoding scheme is demonstrated by Matlab simulations on several standardized LTE test signals.
In this paper, we consider a problem of designing discrete-time systems which are optimal in freq... more In this paper, we consider a problem of designing discrete-time systems which are optimal in frequency-weighted least squares sense subject to a maximal output amplitude constraint. In such problems, the optimality conditions do not provide an explicit way of generating the optimal output as a real-time implementable transformation of the input, due to causal instability of the resulting dynamical equations and sequential nature in which criterion function is revealed over time. On the other hand, under some mild conditions, the optimal system has exponentially fading memory which suggests existence of arbitrarily good finite-latency approximations. In this paper, we extend the method of balanced truncation for linear systems to the class of nonlinear models with weakly contractive operators. We then propose a causally stable finite-latency nonlinear system which returns high-quality approximations to the optimal map. The proposed system is obtained by a careful truncation of an infinite dimensional state space representation of the optimal system, as suggested by the derived generalization of the balanced truncation algorithm.
2018 IEEE International Symposium on Circuits and Systems (ISCAS), 2018
Radio frequency pulse-width modulation (RF-PWM) has been used as a power coding method in all-dig... more Radio frequency pulse-width modulation (RF-PWM) has been used as a power coding method in all-digital transmitters, which employ highly efficient switched-mode power amplifiers (SMPA). The main drawback of RF-PWM is the high level of in-band harmonic distortion when digitally implemented. In order to reduce spectral aliasing effects and produce acceptable levels of harmonic noise, ultra-fast clock speeds are required, making it commercially infeasible. In this paper, we derive a novel compact analytical model of a multilevel digital RF-PWM, driven by an arbitrary bounded baseband signal. We show that the spectral aliasing effects are equivalent to a particular amplitude quantization of the input baseband signal. This result implies that highly linear digital RF-PWM can be realized with modest clock speeds if and only if the input baseband signal is pre-quantized according to the inherent quantization process. We provide full description of this quantization process and describe its ...
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Papers by Omer Tanovic