A direct digital frequency synthesizer includes a multi-modulus divider, a numerically controlled oscillator and a programmable delay generator. The divider receives an input clock having an input pulse frequency and outputs some integer fraction of those pulses at an instantaneous frequency that is some integer fraction (1/P) of the input frequency. The divider selects between at least two ratios of P (1/P or 1/P+1) in response to a signal from the oscillator. The oscillator receives a value which is the accumulator increment (i.e. the number of divided pulse edges) required before an overflow occurs that causes the divider to change divider ratios in response to receiving an overflow signal. The oscillator also outputs both the overflow signal and a delay signal to the delay generator. The delay signal contains phase-dithering noise that is induced by input into the accumulator of an increment generated from a pseudo-random noise generator.

Direct digital synthesizer for reference frequency generation

In accordance with the present invention, in a case of using persistent scheduling, when detecting a transition from a talk state to a silent state, resources to be allocated during a silent state are allocated to a channel exclusive for silent period, and the resources which have been allocated to a mobile terminal during the talk spurt are released. Therefore, the useless allocation of resources can be reduced, and the throughput of the system can be improved.

Communication method, base station, communication system, mobile terminal

Apparatus and methods for distributing spurious tones through the frequency domain are disclosed. One such apparatus can include a dithering circuit configured to generate a sequence of numbers that exhibit statistical randomness and a variable frequency circuit configured to adjust a frequency of an output based on the sequence of numbers so as to spread energy of spurious tones in a frequency response of the output to lower a noise floor. In one example, spurious tones can be reduced in a negative voltage generator of a radio frequency (RF) attenuator.

Variable frequency circuit controller

The invention relates to a data transmission rapid frequency hopping radio station, capable of correspondingly modifying circuits such as a filter and the like according to actual requirement of a user so as to realize wireless frequency hopping communication in a wide frequency band of 175 MHz to 240MHz. Frequency hopping band width of the radio station is adjustable, band widths such as 5MHz, 10MHz, 20MHz and the like can be supported, frequency hopping speed is more than1000 hops per second, and the minimum frequency step value can be 0.12Hz. In structure, the radio station provided by the invention can be divided into two parts, namely a base band module and a radio frequency module, wherein the base band module is arranged below the radio frequency module, and the base band module and the radio frequency module are connected by virtue of a contact pin. The radio frequency module adopts a double-channel direct digital frequency synthesizer and a corresponding signal conditioning circuit as a frequency hopping local oscillator and has the advantages of high frequency hopping speed and high accuracy. The radio station provided by the invention can realize fixed frequency communication and rapid frequency hopping communication according to a customized protocol and has the advantages of small volume, high frequency hopping speed and strong anti-interference performance.

Data transmission rapid frequency hopping radio station

An embodiment of the invention provides a DDS signal generator and a frequency hopping method. The DDS signal generator comprises a phase accumulator, an adder and a waveform memory. The DDS signal generator also comprises a frequency control word memory cell used for storing a frequency control word table which comprises a plurality of frequency control words which are calculated according to frequency set by a user and an acquisition point control unit which acquires a frequency control word from the frequency control word table according to a frequency hopping interval. Thus the DDS signal generator controls output frequency according to the frequency control word to realize frequency hopping. Through the embodiment, a frequency hopping function is realized on hardware resource of a present DDS signal generator, design cost is low, and the frequency hopping function has good extensible and upgradeable performance.

DDS signal generator and frequency hopping method

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).

Alexander Sony Ericsson Mob. Com. Int. Ab Repin

Papers

Direct digital frequency synthesizer for cellular wireless communication systems based on fast frequency-hopped spread spectrum technology