Perturbed phase modulation DDS signal generation method
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A technology of signal generation and phase modulation, applied in the direction of electrical components, etc., to achieve the effect of reducing phase noise and improving phase noise
Active Publication Date: 2018-07-24
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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[0005] The purpose of the present invention is to provide a new method for sine generation, to reduce the capacity of the trigonometric function table in the DDS, improve the frequency resolution of ...
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Embodiment 1
[0030] Embodiment 1: Using frequency f s = 250MHz drive clock generates f 0 = 4.309MHz sinusoidal subcarrier
[0031] Using the aforementioned method, the formula Calculate m=58,
[0032] The frequency resolution of this kind of perturbation phase modulation DDS is determined by the number of bits of the m accumulator and the y accumulator. The m accumulator divides a signal cycle to be generated into m equal parts, and the time interval is the driving clock cycle T s . If the bit width of the y accumulator is L, one drive clock cycle T s into 2 L Equal parts, the smallest representable time interval is 2 -L T s , so the minimum frequency interval, that is, the frequency resolution ΔF, is:
[0033]
[0034] The frequency resolution of a general single accumulator DDS is So the frequency resolution of the perturbation phase modulation DDS of the present invention improves m 2 times, when the reference clock frequency f s =250MHz, if f 0 = 4.309MHz, m = 58, m ...
Embodiment 2
[0036] Embodiment 2: Using the improved perturbation phase modulation DDS to generate a sinusoidal subcarrier signal with a small m value
[0037]When the perturbation phase modulation DDS algorithm of the present invention is relatively small, the effect is not significant, and the performance is also reduced. Because when m is relatively small, the perturbation phase Δθ is relatively large, and the approximate calculation error of the sine-cosine function also increases, which can be compensated by the following method.
[0038] Let f s = 250MHz drive clock to generate f 0 = 20.46MHz sinusoidal subcarrier, m 1 =12, when the phase is There is a large error in the first and second order approximation of the sine and cosine functions. At this point we noticed Therefore, we can divide the 250MHz clock by 12 to obtain a 125 / 6MHz sine wave, then use the perturbation phase modulation DDS method to generate a 112 / 300MHz sine wave, and synthesize it with the 125 / 6MHz sine wa...
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Abstract
The invention discloses a perturbed phase modulation DDS sine wave signal generation method. The method is different from ordinary DDS of using a single-frequency control word and a single accumulatorand starts from the time-domain sampling process of the sine waveform, by means of the mutual effect of two control words and two accumulators, integral sampling time moments and perturbed fractionalsampling time moments are generated, precise moment sampling of each sine cycle is achieved, and sine waves are synthesized by means of phase perturbation and quadrature phase modulation; and due tothe fact that the independent accumulators are adopted in perturbation components, trigonometric function values of a perturbed phases can be approximately calculated, the table look-up capacity of the trigonometric functions is reduced, the frequency resolution is increased, the high-resolution Doppler frequency offset subcarrier digital signal generation problem is solved, and a new method is provided for generation of a wireless receiving synchronization system or low-phase noise sine wave signals.
Description
1. Technical field [0001] The invention belongs to the technical field of signal design and signal processing, in particular to a digital electronic system design technology for sine wave signal generation, reception and synchronization, and is a new method for synthesizing sine wave signals with high frequency resolution. 2. Background technology [0002] Direct digital synthesis DDS (Direct Digital Synthesizer) is a sine wave generation method commonly used in modern digital electronic systems, but DDS requires a large trigonometric function table, and also needs to perform finite truncation of addresses, resulting in phase errors and causing Phase noise in sinusoidal signals, how to use less hardware resources to generate high-quality sinusoidal signals is still a hot issue that is constantly being pursued. [0003] Ordinary DDS uses the accumulation of frequency control words to generate linear phase, and directly checks the sine table to generate sine waves. Due to the...
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