CN1160863C - Digital method for generating local oscillation signals and its numerically controlled oscillator - Google Patents
Digital method for generating local oscillation signals and its numerically controlled oscillator Download PDFInfo
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- CN1160863C CN1160863C CNB001275062A CN00127506A CN1160863C CN 1160863 C CN1160863 C CN 1160863C CN B001275062 A CNB001275062 A CN B001275062A CN 00127506 A CN00127506 A CN 00127506A CN 1160863 C CN1160863 C CN 1160863C
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Abstract
The present invention discloses a digital local oscillation signal generating method and a digital control oscillator. In the phase calculation of a table lookup amplitude output unit, phases output by a truncation module unit are split into large phases and fine step length; the digits of large phases are used as table lookup address for looking up a large phase storage table to obtain the sine values and the cosine values of the large phases; the inphase components and the orthogonal components of the digital local oscillation signals are output after the obtained sine values and the obtained cosine values of the large phases and the obtained fine step length are calculated by a Taylor expansion formula of a trigonometric function. The present invention has the advantages of high working speed, wide application range and system resource and power consumption saving.
Description
Technical field
The present invention relates to the digital mobile communication technology, more specifically refer to a kind of digital method for generating local oscillation signal and numerically-controlled oscillator thereof.
Background technology
Frequency synthesizer is a device of realizing frequency inverted.Be widely used in producing the reference frequency of electronic system, the influence of precision, stability and peripheral circuit that precision that it is synthetic and stability mainly are subjected to its reference frequency.
Numerically-controlled oscillator (NCO-Numerical Control Oscillator) is the product of Digital Signal Processing development.It also is the reference frequency that is used to produce electronic system, compares with the legacy frequencies synthesizer, and it is very high to have frequency resolution, and frequency translation speed is very fast, and the frequency translation phase place is continuous, and phase noise is low, the integrated level height, and volume is little, produces advantages such as multiple signal flexibly.But owing to adopted full-digital circuit, must produce spurious signal, and spuious many and difficult the following of the regularity of distribution is the principal element that restriction numerically-controlled oscillator technology is used always.
In recent years, constantly perfect along with Digital Signal Processing, the raising of high-speed figure technology rapid development and integrated technique level, the paces that quickened the numerically-controlled oscillator model change.The frequency resolution of numerically-controlled oscillator has improved 9 orders of magnitude (phase-accumulated figure place has been brought up to 40 from initial tens, is generally 32 at present); From producing single sine/cosine signals to producing multiple modulation output; Clock frequency develops into tens GHz from several megahertzes; Because adopted spuious inhibition technology in the chip, the numerically-controlled oscillator spurious performance greatly improves; Frequency translation speed has been brought up to the ns level; Control mode is developed into various control forms such as serial, parallel and bus by original parallel control, numerically-controlled oscillator has entered the practicability stage.
In the modern communications electronic system, numerically-controlled oscillator is widely used in fields such as communications electronics system, radar system, electronic countermeasures, aviation, navigation as the frequency synthesizer of a new generation.
Traditional numerically-controlled oscillator basic functional principle is as shown in Figure 1: undertaken phase-accumulatedly by the frequency control word of output frequency, each phase place that obtains is searched the triangle magnitudes table, its output is exactly the sine or the cosine signal output form of this output frequency.Its numerically-controlled oscillator basic structure as shown in Figure 2, FREQUENCY CONTROL word cell 101 produces the totalizing step of a corresponding output frequency, add up in phase accumulator unit 102 with sample frequency, look into sine and cosine table amplitude output unit 105 stored and the sine/cosine of corresponding (0-2pi) phase place, the phase value that obtains after adding up by accumulator element removes to inquire about sine and cosine amplitude output unit as the address of tabling look-up, and just obtains the digitlization sine or the cosine range value of corresponding output frequency.Unit 103 wherein is phase jitter unit, and its amplitude jitter with 105 inside, unit is the same, as the spuious a kind of mode of effective inhibition.Because the storage list capacity in the unit 105 is limit, truncation modular unit 104 is that the former phase place figure place that will add phase jitter intercepts one section, promptly can reduce the storage list capacity in the unit 105, reduce resource consumption, can keep high table look-up precision and Spurious Free Dynamic Range performance again, unit 106 is an adder.
The shortcoming that exists in the above-mentioned conventional digital control generator: along with the increase of addressing phase place, the storage list of looking into sine and cosine table amplitude output unit will be progression to be increased, as, as the addressing phase place is 18bit, then needing two forms of I/Q is the 2*2^18=524288bit memory cell, so the form capacity is too big, causes system resource ROM table memory space huge, power consumption is too high, is not suitable for high speed operation.
Summary of the invention
For this reason, the objective of the invention is the shortcoming that exists in the conventional digital control generator, a kind of improved digital method for generating local oscillation signal and numerically-controlled oscillator thereof are provided.
To achieve these goals, the present invention adopts following technical scheme:
Digital method for generating local oscillation signal of the present invention comprises:
Produce the totalizing step of a corresponding output frequency with the FREQUENCY CONTROL word cell, and the step that totalizing step is added up by accumulator;
Produce the step of dither signal by the phase jitter unit;
The accumulation result of described totalizing step and dither signal are input to adder carry out the step that add operation obtains additive phase;
The input step of amplitude output unit of tabling look-up after one section of the additive phase figure place intercepting that add operation is obtained with the truncation modular unit;
The amplitude output unit carries out the phase place of truncation modular unit output to export the in-phase component of digital local oscillation signal and the step of quadrature component after the computing with tabling look-up;
The amplitude output unit carries out further comprising in the computing to the phase place of truncation modular unit output tabling look-up:
The phase place of truncation modular unit output is split as the step of thick phase place and tiny stepping length;
Obtain the step of thick phase place sine value and thick phase cosine value as the thick phase place storage list of the address search of tabling look-up with described thick phase place figure place;
With the thick phase place sine value, cosine value and the tiny stepping length that obtain by the Taylor expansion formula operation of trigonometric function after the in-phase component of the digital local oscillation signal of output and the step of quadrature component.
According to said method, numerically-controlled oscillator of the present invention comprises the FREQUENCY CONTROL word cell, phase accumulator unit, adder, the phase jitter unit, the truncation modular unit, the amplitude of tabling look-up output unit, the FREQUENCY CONTROL word cell produces the totalizing step of a corresponding output frequency and inputs to phase accumulator unit, phase accumulator unit inputs to adder after the totalizing step of this output frequency is added up, and the phase jitter signal plus that produces with the phase jitter unit, after intercepting one section, the additive phase figure place that the truncation modular unit is exported adder inputs to the amplitude output unit of tabling look-up, the in-phase component and the quadrature component of the amplitude of tabling look-up output unit output digitlization local oscillation signal, wherein: the described amplitude output unit of tabling look-up comprises the phase place decomposing module of tabling look-up, thick phase place sine, the cosine storage list, arithmetic logic unit, the phase place of tabling look-up decomposing module is decomposed into thick phase place and tiny stepping length with the output phase value of truncation modular unit, and it is sinusoidal mutually for the thick phase place of the address search of tabling look-up with thick phase place figure place, the cosine storage list, thick phase place sine, the output of cosine storage list just, cosine value and tiny stepping length are delivered to arithmetic logic unit handled and exported digital local oscillation signal by the Taylor expansion formula operation of trigonometric function in-phase component and quadrature component.
Because method of the present invention adopts the phase place with the output of truncation modular unit to be split as thick phase place and tiny stepping length; Obtain thick phase place sine value and thick phase cosine value with described thick phase place figure place as the thick phase place storage list of the address search of tabling look-up; With the thick phase place sine value, cosine value and the tiny stepping length that obtain by the Taylor expansion formula operation of trigonometric function after the in-phase component and the quadrature component of the digital local oscillation signal of output.In the amplitude output unit of tabling look-up, adopted and comprised the phase place decomposing module of tabling look-up, thick phase place storage list, arithmetic logic unit, the phase place of tabling look-up decomposing module is decomposed into thick phase place and tiny stepping length with the output phase value of truncation modular unit, and being the thick phase place storage list of the address search of tabling look-up with thick phase place figure place, the output of thick phase place storage list and tiny stepping length are delivered to arithmetic logic unit and are carried out calculation process and export in-phase component and quadrature component.The present invention has overcome traditional digital controlled oscillator because the form capacity is big, and it is many to take resource, and the too big shortcoming of the power consumption of memory in causing showing, and it has the following advantages:
1, reduces the capacity of memory and reduced resource widely, and reduced power consumption;
2, solved memory owing to the excessive high defective that is not suitable for high speed operation of power consumption that causes, improved the practicality of digital controlled oscillator, and expanded its range of application;
3, the spuious effect of inhibition is good, can be up to about 110dB;
4, adopt digital mode, the signal quality of generation is good, has higher accuracy.
Below in conjunction with drawings and Examples, digital method for generating local oscillation signal of the present invention and numerically-controlled oscillator work one are explained:
Description of drawings
Fig. 1 is conventional digital control vibration basic principle block diagram.
Fig. 2 is traditional numerically-controlled oscillator structural representation block diagram.
Fig. 3 is a numerically-controlled oscillator structural representation block diagram of the present invention.
Fig. 4 utilizes the resulting signal power spectrogram of numerically-controlled oscillator of the present invention.
Embodiment
Digital method for generating local oscillation signal of the present invention is based on one and comprises the numerically-controlled oscillator that FREQUENCY CONTROL word cell, accumulator, phase jitter unit, adder, truncation modular unit, the amplitude of tabling look-up output unit constitute, and may further comprise the steps:
The FREQUENCY CONTROL word cell produces the totalizing step of a corresponding output frequency, and by accumulator totalizing step is added up;
Produce dither signal by the phase jitter unit;
The accumulation result of described totalizing step and dither signal are input to adder carries out add operation and obtains additive phase;
After intercepting one section, the additive phase figure place that the truncation modular unit obtains add operation imports the amplitude output unit of tabling look-up;
At the amplitude output unit of tabling look-up the phase place of truncation modular unit output being carried out computing further may further comprise the steps:
The phase place of truncation modular unit output is split as thick phase place and tiny stepping length;
Obtain thick phase place sine value and thick phase cosine value with described thick phase place figure place as the thick phase place storage list of the address search of tabling look-up;
With the thick phase place sine value, cosine value and the tiny stepping length that obtain by the Taylor expansion formula operation of trigonometric function after the in-phase component and the quadrature component of the digital local oscillation signal of output.
See also shown in Figure 3, oscillator of the present invention is based on traditional numerically-controlled oscillator basic structure basis, comprise FREQUENCY CONTROL word cell 101, phase accumulator unit 102, adder 106, phase jitter unit 103 truncation modular units 104, the amplitude of tabling look-up output unit 105, FREQUENCY CONTROL word cell 101 produces the totalizing step of a corresponding output frequency and inputs to phase accumulator unit 102, after adding up, the totalizing step of 102 pairs of these output frequencies of phase accumulator unit inputs to adder 106, and the phase jitter signal plus that produces with phase jitter unit 103, input to the amplitude output unit 105 of tabling look-up after one section of the additive phase figure place intercepting of 104 pairs of adders outputs of truncation modular unit.
The described amplitude output unit 105 of tabling look-up comprises the phase place decomposing module 203 of tabling look-up, thick phase place storage list 201, arithmetic logic unit 202, the phase place of tabling look-up decomposing module 203 is decomposed into thick phase place and tiny stepping length with the output phase value of truncation modular unit 104, the figure place W that always tables look-up that is about to former angle represents with thick interval phase place and tiny stepping length, and be the thick phase place storage list 201 of the address search of tabling look-up, the output of thick phase place storage list 201 with thick phase place figure place, and tiny stepping length is delivered to arithmetic logic unit 202 and is carried out calculation process and export in-phase component I and quadrature component Q.
The figure place generation capacity of always tabling look-up that the described phase place decomposing module 203 of tabling look-up is exported truncation modular unit 104 according to Taylor's formula is two pairing phase place storage lists of thick phase place.That is, described thick phase place storage list 201 comprises sinusoidal storage list of thick phase place and thick phase cosine storage list (do not draw and illustrate) in Fig. 3.
The basic principle of the above-mentioned phase place decomposing module 203 of tabling look-up is to utilize Taylor's formula:
cos(t0+Δt)＝cost0-sint0×Δt+R
k+l(Δt)；
sin(T0+Δt)＝sint0+cost0×Δt+R
k+l(Δt)
This shows, it carries out Taylor with the trigonometric function value of former table look-at phase value W and decomposes expansion, the phase place of will tabling look-up W (Npbit) is divided into thick phase place (Hbit) and tiny phase place stepping length (Np-H bit), the figure place H bit of corresponding thick phase place, the capacity of setting up only is the little table of SIN/COS trigonometric function value of 2^H.The SIN/COS value of other all phase places is according to Taylor expansion, the SIN/COS value that finds with the thick interval phase place after launching respectively, be multiplied by tiny phase place stepping length, carry out addition/subtract computing again, can obtain inphase/orthogonal (I/Q) value of total phase place W correspondence, finish the Frequency and Amplitude value output of whole numerically-controlled oscillator.
In the method for the invention, be that second order Taylor expansion formula by trigonometric function carries out computing with thick phase place sine value, cosine value and the tiny stepping length that obtains.
Can reach very high compression ratio after utilizing method for generating local oscillation signal of the present invention and numerically-controlled oscillator.If former addressing phase place is 18bit, then needing two forms of inphase/orthogonal (I/Q) is the 2*2^18=524288bit memory cell.After adopting triangle symmetry and Taylor expansion to decompose, two low capacity forms only need about 512bit memory cell altogether, compression ratio was up to 1024: 1, saved system resource widely beyond doubt, overcome the conventional digital control generator because the form capacity is too big, and caused system resource storage list memory space huge, power consumption is too high, be not suitable for the defective of high speed operation, simultaneously, suppress spuious dynamic range SFDR and can reach 109.96dB.Thereby improved the practicality of numerically-controlled oscillator and expanded application, can be widely used in the fields such as communications electronics system, radar system, electronic countermeasures, aviation, navigation as digital frequency synthesizer.
Through simulation study checking, adopt numerically-controlled oscillator of the present invention after, its spectral characteristic as shown in Figure 4, this figure is the power spectrum of output frequency=18MHz.Ordinate is a power spectral density, and the dB of unit, abscissa are frequency range, the MHz of unit.At this moment, the SFDR=119.3dB of numerically-controlled oscillator.
Claims (3)
1, a kind of digital method for generating local oscillation signal, this method comprises:
Produce the totalizing step of a corresponding output frequency with the FREQUENCY CONTROL word cell, and the step that totalizing step is added up by accumulator;
Produce the step of dither signal by the phase jitter unit;
The accumulation result of described totalizing step and dither signal are input to adder carry out the step that add operation obtains additive phase;
The input step of amplitude output unit of tabling look-up after one section of the additive phase figure place intercepting that add operation is obtained with the truncation modular unit;
The amplitude output unit carries out the phase place of truncation modular unit output to export the in-phase component of digital local oscillation signal and the step of quadrature component after the computing with tabling look-up;
It is characterized in that the amplitude output unit carries out further comprising in the computing to the phase place of truncation modular unit output tabling look-up:
The phase place of truncation modular unit output is split as the step of thick phase place and tiny stepping length;
Obtain the step of thick phase place sine value and thick phase cosine value as the thick phase place storage list of the address search of tabling look-up with described thick phase place figure place;
With the thick phase place sine value, cosine value and the tiny stepping length that obtain by the Taylor expansion formula operation of trigonometric function after the in-phase component of the digital local oscillation signal of output and the step of quadrature component.
2, digital method for generating local oscillation signal as claimed in claim 1 is characterized in that: the thick phase place sine value that will obtain, cosine value and tiny stepping length are that the second order Taylor expansion formula by trigonometric function carries out computing.
3, a kind of numerically-controlled oscillator, this oscillator comprises the FREQUENCY CONTROL word cell, phase accumulator unit, adder, the phase jitter unit, the truncation modular unit, the amplitude of tabling look-up output unit, the FREQUENCY CONTROL word cell produces the totalizing step of a corresponding output frequency and inputs to phase accumulator unit, phase accumulator unit inputs to adder after the totalizing step of this output frequency is added up, and the phase jitter signal plus that produces with the phase jitter unit, after intercepting one section, the additive phase figure place that the truncation modular unit is exported adder inputs to the amplitude output unit of tabling look-up, the in-phase component and the quadrature component of the amplitude of tabling look-up output unit output digitlization local oscillation signal, it is characterized in that: the described amplitude output unit of tabling look-up comprises the phase place decomposing module of tabling look-up, thick phase place sine, the cosine storage list, arithmetic logic unit, the phase place of tabling look-up decomposing module is decomposed into thick phase place and tiny stepping length with the output phase value of truncation modular unit, and be the thick phase place sine of the address search of tabling look-up with thick phase place figure place, the cosine storage list, thick phase place sine, the output of cosine storage list just, cosine value and tiny stepping length are delivered to arithmetic logic unit handled and exported digital local oscillation signal by the Taylor expansion formula operation of trigonometric function in-phase component and quadrature component.
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| CNB001275062A CN1160863C (en) | 2000-11-23 | 2000-11-23 | Digital method for generating local oscillation signals and its numerically controlled oscillator |
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| CNB001275062A CN1160863C (en) | 2000-11-23 | 2000-11-23 | Digital method for generating local oscillation signals and its numerically controlled oscillator |
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