Patent
Direct digital frequency synthesizer for cellular wireless communication systems based on fast frequency-hopped spread spectrum technology
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TLDR
In this article, the authors proposed a method for reducing spurious harmonics, voltage and/or current glitches in the frequency synthesizer's power density spectrum caused by phase truncation, amplitude and time quantization errors introducing jitter into the waveform of the output signal.Abstract:
Direct digital frequency synthesizer (DDFS) are used for generating an oscillator signal
( ( t )) with an approximately sinusoidal waveshape and can advantageously be applied to
wireless RF transceivers in a cellular communication system based on a fast frequency-hopped
spread spectrum (FHSS) technology. The invention particularly refers to a method
for reducing spurious harmonics, voltage and/or current glitches in the frequency synthesizer's
noise power density spectrum ( ( kf )) caused by phase truncation, amplitude and
time quantization errors introducing jitter into the waveform of the output signal ( ( t )).
Thereby, discrete P -bit phase difference values (Δϕ s ( nT )) serving as frequency control
words (FCWs) are repeatedly accumulated to generate P'-bit samples of a digital sawtooth
signal ( ϕ s ( nT )) with a predefined time period ( N · T ), which are then submitted to a phase-to-sine-amplitude
conversion of the obtained discrete phase input values ( ϕ s ( nT )) into a set of
discrete sine amplitude sample values ( s ( nT )). After that, these sine amplitude sample values
( s ( nT )) are converted into an approximation of a quantized analog sine wave ( a 1 '( t )). According to one embodiment of the underlying invention, spurious harmonics (DSCs) are
spread over the entire signal spectrum by adding a P "-bit number word representation of a
random number ( r ( nT )) to the obtained sine amplitude sample values ( s ( nT )). Thus, the
periodical structure of glitches, phase truncation and quantization errors ( ( nT )) of the
approximated sine wave ( ( t )) is destroyed and its spurious discrete noise power density
spectrum ( ( kf )) caused by said error signal ( ( nT )) is transformed into a broadband
continuous noise power density spectrum ( ( f )). Finally, the additive noise is compensated
by subtracting a digital-to-analog converted representation of said random number
( r ( nT )) from the quantized analog sine wave approximation ( a 1 '( t )) at the analog output
port of the direct digital frequency synthesizing unit (DDFS).read more
Citations
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References
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Proceedings ArticleDOI
Spur reduction techniques in direct digital synthesizers
TL;DR: Spur reduction techniques used in direct digital synthesizers (DDSs) or numerically controlled oscillators (NCOs) are reviewed and spur reduction techniques which reduce spurs by destroying the coherence of the aliasing process are discussed.
Patent
Method and apparatus for locating a digital control channel in a downbanded cellular radiocommunication system
TL;DR: In this paper, a method and system for locating control channels, particularly digital control channels are described, by grouping the channels which are candidates for carrying supervisory messages in blocks indicative of their relative likelihood for being used as control channels.
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Signal generation using digital-to-analogue conversion
TL;DR: In this paper, a digital-to-analogous conversion circuit for generating an analogue signal by way of digital to analog conversion, such as a direct digital frequency synthesiser (DFS), is presented.
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Wireless communication system
TL;DR: In this article, a cellular radio communication system with a plurality of base stations and terminals is considered, in which one cell is divided into a plurality and each base station transmits and receives control information by an omnidirectional beamforming and receives traffic information by a directional beam.