24 research outputs found
Analysis and design of ΣΔ Modulators for Radio Frequency Switchmode Power Amplifiers
Power amplifiers are an integral part of every basestation, macrocell, microcell and mobile
phone, enabling data to be sent over the distances needed to reach the receiver’s antenna.
While linear operation is needed for transmitting WCDMA and OFDM signals, linear
operation of a power amplifier is characterized by low power efficiency, and contributes
to unwanted power dissipation in a transmitter. Recently, a switchmode power amplifier
operation was considered for reducing power losses in a RF transmitter. A linear and
efficient operation of a PA can be achieved when the transmitted RF signal is ΣΔ modu-
lated, and subsequently amplified by a nonlinear device. Although in theory this approach
offers linearity and efficiency reaching 100%, the use of ΣΔ modulation for transmitting
wideband signals causes problems in practical implementation: it requires high sampling
rate by the digital hardware, which is needed for shaping large contents of a quantization
noise induced by the modulator but also, the binary output from the modulator needs an
RF power amplifier operating over very wide frequency band.
This thesis addresses the problem of noise shaping in a ΣΔ modulator and nonlinear
distortion caused by broadband operation in switchmode power amplifier driven by a ΣΔ
modulated waveform. The problem of sampling rate increase in a ΣΔ modulator is solved
by optimizing structure of the modulator, and subsequent processing of an input signal’s
samples in parallel. Independent from the above, a novel technique for reducing quan-
tization noise in a bandpass ΣΔ modulator using single bit quantizer is presented. The
technique combines error pulse shaping and 3-level quantization for improving signal to
noise ratio in a 2-level output. The improvement is achieved without the increase of a digital
hardware’s sampling rate, which is advantageous also from the perspective of power
consumption. The new method is explored in the course of analysis, and verified by simulated
and experimental results. The process of RF signal conversion from the Cartesian to
polar form is analyzed, and a signal modulator for a polar transmitter with a ΣΔ-digitized
envelope signal is designed and implemented. The new modulator takes an advantage of
bandpass digital to analog conversion for simplifying the analog part of the modulator.
A deformation of the pulsed RF signal in the experimental modulator is demonstrated to
have an effect primarily on amplitude of the RF signal, which is correctable with simple
predistortion
Parallelization of Bandpass Sigma-Delta Modulators for Class-S Digital Power Amplifiers
In this paper a new technique of utilizing parallel
sigma delta modulation for high frequency switch mode digital
power amplifiers is presented. This approach allows achieving a
factor of two increase of a digital logic speed for band-pass SDM
with minor adjustments made. A universal scheme for a SDM
system transformation is provided. Since the transformation
scheme is established, a parallel low-pass SDM, expandable to
a factor of four clock frequency reduction is designed. The
parallelization of a low pass SDM however requires modification
on the form of a Noise Transfer Function in order to preserve
desired speed of a digital logic. This can affect the overall
performance of the SDM. The derivation of the systems is
provided through analysis of discrete time domain equations.
The method is validated through simulations
Improved Coding-Efficiency Two-Level Source Encoder for RF Switch-Mode Power Amplifiers
A ΣΔ-driven RF switch-mode power amplifier is
inherently linear only when it has a two-level output. At the
same time, a two-level output generates the largest amount of
quantization noise. This brief analyzes the effect of nonequal
level spacing in a three-level ΣΔ output and provides a method
for shaping the corresponding error noise to regions outside the
band of interest. Subsequently, the nonlinearity-shaping property
is utilized to obtain an improved two-level drive signal based on
three-levelΣΔmodulation. The new binary drive signal is proven
to have better adjacent channel leakage ratio and higher coding
efficiency than a conventional two-level ΣΔ modulator. In the
investigated case, measured coding efficiency improves from 8.9%
of the conventional two-level modulator to 21% of the modified
two-level modulator
Reconfigurable Class S Power Amplifiers at RF and Microwave Frequencies
When a delta-sigma modulator (DSM) is placed before a class D switching stage the combination can be used to amplify time varying envelope signals. However a bandpass DSM is commonly employed and is required to have a sampling frequency approximately four times the carrier frequency. At RF or microwave frequencies proprietary hardware was previously needed to implement the DSM. However, it is shown here in simulation and from experimental measurement that a suitable DSM for class S power amplifiers can be implemented at RF and microwave frequencies using mid-range FPGA technology.
Index Terms- Class S, efficiency, power amplifiers, sigma-delta modulatio
Reconfigurable High Frequency Class S Power Amplifier Demonstrator
This paper presents an end-to-end high frequency
class S power amplifier. A description of the full testbench and
some important points on generation of RF outputs from FPGA
devices and current mode class D design are given.
Experimental measurements are provided for the prototype PA
consisting of a signal generator, analog to digital converter,
driver circuit, current mode class D switching stage and
bandpass filter. Theory and experimentally measured results for
this prototype are presented for a multi tone signal centred at
930 MHz and with a total output power of 24.7dBm
Design of signal modulator for RF polar transmitter
This paper presents new approach to signal modulation
for high efficiency polar transmitter. The new modulator
is derived by analyzing complex to polar transforming equations.
Once spectral behavior of an envelope and phase signals
are known, new architecture offering lower complexity in an
analog domain and more flexibility for reconfiguration than a
conventional modulator is derived. Concept of the modulator is
verified in the course of step-by step simulations with a 5MHz
BW input signal at a carrier frequency fC = 2:14GHz. Also,
a drain efficiency of a Class E PA driven by the modulator is
discussed, and optimal solution for sampling rate is propose
Analysis and design of ΣΔ Modulators for Radio Frequency Switchmode Power Amplifiers
Power amplifiers are an integral part of every basestation, macrocell, microcell and mobile
phone, enabling data to be sent over the distances needed to reach the receiver’s antenna.
While linear operation is needed for transmitting WCDMA and OFDM signals, linear
operation of a power amplifier is characterized by low power efficiency, and contributes
to unwanted power dissipation in a transmitter. Recently, a switchmode power amplifier
operation was considered for reducing power losses in a RF transmitter. A linear and
efficient operation of a PA can be achieved when the transmitted RF signal is ΣΔ modu-
lated, and subsequently amplified by a nonlinear device. Although in theory this approach
offers linearity and efficiency reaching 100%, the use of ΣΔ modulation for transmitting
wideband signals causes problems in practical implementation: it requires high sampling
rate by the digital hardware, which is needed for shaping large contents of a quantization
noise induced by the modulator but also, the binary output from the modulator needs an
RF power amplifier operating over very wide frequency band.
This thesis addresses the problem of noise shaping in a ΣΔ modulator and nonlinear
distortion caused by broadband operation in switchmode power amplifier driven by a ΣΔ
modulated waveform. The problem of sampling rate increase in a ΣΔ modulator is solved
by optimizing structure of the modulator, and subsequent processing of an input signal’s
samples in parallel. Independent from the above, a novel technique for reducing quan-
tization noise in a bandpass ΣΔ modulator using single bit quantizer is presented. The
technique combines error pulse shaping and 3-level quantization for improving signal to
noise ratio in a 2-level output. The improvement is achieved without the increase of a digital
hardware’s sampling rate, which is advantageous also from the perspective of power
consumption. The new method is explored in the course of analysis, and verified by simulated
and experimental results. The process of RF signal conversion from the Cartesian to
polar form is analyzed, and a signal modulator for a polar transmitter with a ΣΔ-digitized
envelope signal is designed and implemented. The new modulator takes an advantage of
bandpass digital to analog conversion for simplifying the analog part of the modulator.
A deformation of the pulsed RF signal in the experimental modulator is demonstrated to
have an effect primarily on amplitude of the RF signal, which is correctable with simple
predistortion
Analysis and design of ΣΔ Modulators for Radio Frequency Switchmode Power Amplifiers
Power amplifiers are an integral part of every basestation, macrocell, microcell and mobile
phone, enabling data to be sent over the distances needed to reach the receiver’s antenna.
While linear operation is needed for transmitting WCDMA and OFDM signals, linear
operation of a power amplifier is characterized by low power efficiency, and contributes
to unwanted power dissipation in a transmitter. Recently, a switchmode power amplifier
operation was considered for reducing power losses in a RF transmitter. A linear and
efficient operation of a PA can be achieved when the transmitted RF signal is ΣΔ modu-
lated, and subsequently amplified by a nonlinear device. Although in theory this approach
offers linearity and efficiency reaching 100%, the use of ΣΔ modulation for transmitting
wideband signals causes problems in practical implementation: it requires high sampling
rate by the digital hardware, which is needed for shaping large contents of a quantization
noise induced by the modulator but also, the binary output from the modulator needs an
RF power amplifier operating over very wide frequency band.
This thesis addresses the problem of noise shaping in a ΣΔ modulator and nonlinear
distortion caused by broadband operation in switchmode power amplifier driven by a ΣΔ
modulated waveform. The problem of sampling rate increase in a ΣΔ modulator is solved
by optimizing structure of the modulator, and subsequent processing of an input signal’s
samples in parallel. Independent from the above, a novel technique for reducing quan-
tization noise in a bandpass ΣΔ modulator using single bit quantizer is presented. The
technique combines error pulse shaping and 3-level quantization for improving signal to
noise ratio in a 2-level output. The improvement is achieved without the increase of a digital
hardware’s sampling rate, which is advantageous also from the perspective of power
consumption. The new method is explored in the course of analysis, and verified by simulated
and experimental results. The process of RF signal conversion from the Cartesian to
polar form is analyzed, and a signal modulator for a polar transmitter with a ΣΔ-digitized
envelope signal is designed and implemented. The new modulator takes an advantage of
bandpass digital to analog conversion for simplifying the analog part of the modulator.
A deformation of the pulsed RF signal in the experimental modulator is demonstrated to
have an effect primarily on amplitude of the RF signal, which is correctable with simple
predistortion
Analysis and design of ΣΔ Modulators for Radio Frequency Switchmode Power Amplifiers
Power amplifiers are an integral part of every basestation, macrocell, microcell and mobile
phone, enabling data to be sent over the distances needed to reach the receiver’s antenna.
While linear operation is needed for transmitting WCDMA and OFDM signals, linear
operation of a power amplifier is characterized by low power efficiency, and contributes
to unwanted power dissipation in a transmitter. Recently, a switchmode power amplifier
operation was considered for reducing power losses in a RF transmitter. A linear and
efficient operation of a PA can be achieved when the transmitted RF signal is ΣΔ modu-
lated, and subsequently amplified by a nonlinear device. Although in theory this approach
offers linearity and efficiency reaching 100%, the use of ΣΔ modulation for transmitting
wideband signals causes problems in practical implementation: it requires high sampling
rate by the digital hardware, which is needed for shaping large contents of a quantization
noise induced by the modulator but also, the binary output from the modulator needs an
RF power amplifier operating over very wide frequency band.
This thesis addresses the problem of noise shaping in a ΣΔ modulator and nonlinear
distortion caused by broadband operation in switchmode power amplifier driven by a ΣΔ
modulated waveform. The problem of sampling rate increase in a ΣΔ modulator is solved
by optimizing structure of the modulator, and subsequent processing of an input signal’s
samples in parallel. Independent from the above, a novel technique for reducing quan-
tization noise in a bandpass ΣΔ modulator using single bit quantizer is presented. The
technique combines error pulse shaping and 3-level quantization for improving signal to
noise ratio in a 2-level output. The improvement is achieved without the increase of a digital
hardware’s sampling rate, which is advantageous also from the perspective of power
consumption. The new method is explored in the course of analysis, and verified by simulated
and experimental results. The process of RF signal conversion from the Cartesian to
polar form is analyzed, and a signal modulator for a polar transmitter with a ΣΔ-digitized
envelope signal is designed and implemented. The new modulator takes an advantage of
bandpass digital to analog conversion for simplifying the analog part of the modulator.
A deformation of the pulsed RF signal in the experimental modulator is demonstrated to
have an effect primarily on amplitude of the RF signal, which is correctable with simple
predistortion
Analysis and design of ΣΔ Modulators for Radio Frequency Switchmode Power Amplifiers
Power amplifiers are an integral part of every basestation, macrocell, microcell and mobile
phone, enabling data to be sent over the distances needed to reach the receiver’s antenna.
While linear operation is needed for transmitting WCDMA and OFDM signals, linear
operation of a power amplifier is characterized by low power efficiency, and contributes
to unwanted power dissipation in a transmitter. Recently, a switchmode power amplifier
operation was considered for reducing power losses in a RF transmitter. A linear and
efficient operation of a PA can be achieved when the transmitted RF signal is ΣΔ modu-
lated, and subsequently amplified by a nonlinear device. Although in theory this approach
offers linearity and efficiency reaching 100%, the use of ΣΔ modulation for transmitting
wideband signals causes problems in practical implementation: it requires high sampling
rate by the digital hardware, which is needed for shaping large contents of a quantization
noise induced by the modulator but also, the binary output from the modulator needs an
RF power amplifier operating over very wide frequency band.
This thesis addresses the problem of noise shaping in a ΣΔ modulator and nonlinear
distortion caused by broadband operation in switchmode power amplifier driven by a ΣΔ
modulated waveform. The problem of sampling rate increase in a ΣΔ modulator is solved
by optimizing structure of the modulator, and subsequent processing of an input signal’s
samples in parallel. Independent from the above, a novel technique for reducing quan-
tization noise in a bandpass ΣΔ modulator using single bit quantizer is presented. The
technique combines error pulse shaping and 3-level quantization for improving signal to
noise ratio in a 2-level output. The improvement is achieved without the increase of a digital
hardware’s sampling rate, which is advantageous also from the perspective of power
consumption. The new method is explored in the course of analysis, and verified by simulated
and experimental results. The process of RF signal conversion from the Cartesian to
polar form is analyzed, and a signal modulator for a polar transmitter with a ΣΔ-digitized
envelope signal is designed and implemented. The new modulator takes an advantage of
bandpass digital to analog conversion for simplifying the analog part of the modulator.
A deformation of the pulsed RF signal in the experimental modulator is demonstrated to
have an effect primarily on amplitude of the RF signal, which is correctable with simple
predistortion