6 research outputs found
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
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
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
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