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Direct digital frequency synthesis method

A digital frequency synthesis, direct technology, applied in the direction of electrical components, logic circuits, pulse technology, etc., can solve the problems of low spurious suppression ratio, inability to output waveform spurious suppression, increased application cost, etc., to improve the spurious suppression ratio , save lookup table resources, and expand the effect of the application

Pending Publication Date: 2020-12-18
INST OF ELECTRONICS ENG CHINA ACAD OF ENG PHYSICS
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Problems solved by technology

Although the design methods for suppressing output spurs have been adopted in the design of direct digital frequency synthesis, such as dithering method, mutual prime method, etc., the spur suppression ratio of these methods is still very low, and they cannot effectively control the output waveform spurs. Inhibition, which in turn leads to the limitation of the application range of direct digital frequency synthesizers, especially in some occasions that require relatively high output spurious control
[0004] In addition, the existing direct digital frequency synthesis methods all use direct addressing to look up the lookup table. When the bit width of the input signal is large, the addressing depth of the established lookup table is also large, which will lead to direct Digital frequency synthesizer cannot be applied in some occasions with limited resources, even if it can be used, its application cost will be greatly increased

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preparation example Construction

[0028] Such as figure 1 A kind of direct digital frequency synthesis method shown, it is characterized in that, this method comprises the following steps:

[0029] a. Input the given frequency control word into the phase accumulator for accumulation and integration to obtain the output phase φ with a bit width of M 0 ;

[0030] b. Change the phase φ 0 decomposed into two random phases φ 1 and φ 2 ;

[0031] c. Randomize the phase φ 1 and φ 2 Carry out equal bit width decomposition respectively, and decompose into a plurality of equal bit width phases whose effective phase bit width is N, wherein, N satisfies M=2x*N, (x=1, 2, 3...);

[0032] d. Construct a lookup table corresponding to the phase of equal bit width one by one;

[0033] e. Query the lookup table;

[0034] f. Perform signal synthesis on the query results to obtain the final signal;

[0035] g. Send the final signal to the digital-to-analog converter for output.

[0036] Phase φ in step b 0 The method o...

Embodiment 1

[0066] In this embodiment, the phase equal bit width decomposition takes the parity bit decomposition method of random phase binary numbers as an example, and performs direct digital frequency synthesis according to the following steps:

[0067] a. Set the phase bit width of the frequency control word to 20 bits, input it into the phase accumulator, accumulate and integrate according to the clock beat, and obtain the output phase. In this embodiment, the output phase is 1024.

[0068] b. Phase random decomposition. Use the random phase I generated by the original polynomial, take the random phase I as 566, and the address of the corresponding random phase II is 1024-566=458; quantify the two phases according to the bit width of 20 bits respectively: the random phase I corresponds to 566 The binary phase address table is: (0000000000-1000110110), and the binary phase address table corresponding to random phase II 458 is: (0000000000-0111001010);

[0069] c. Decompose the phase...

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Abstract

The invention discloses a direct digital frequency synthesis method, which comprises the following steps of: dividing an output phase of a phase accumulator into two random phases, decomposing the tworandom phases into a plurality of phases with the same effective phase bit width, constructing lookup tables in one-to-one correspondence with the phases with the same effective phase bit width, carrying out inquiring, and finally, carrying out multi-stage signal synthesis on a query result, and sending a final synthesis signal to a digital-to-analog converter for outputting. According to the synthesis method, complex signal operation and an Euler formula rule are utilized, random query of multiple lookup tables is achieved while an output result is not changed, the signal spurious problem caused by quantization errors of an existing direct digital frequency synthesizer is effectively solved, the signal spurious suppression ratio is increased, and the signal quality is improved. In addition, a multi-lookup-table method is adopted, lookup table resources are saved, the application cost of the direct digital frequency synthesizer is saved, and the application range of the direct digitalfrequency synthesizer is expanded.

Description

technical field [0001] The invention belongs to the field of digital signal processing, and in particular relates to a direct digital frequency synthesis method based on a polyphase lookup table. Background technique [0002] A large number of digital signal processing devices are currently used in radar, communication and other fields, and the direct digital frequency synthesizer (DDS) is one of the typical digital signal processing devices. The existing direct digital frequency synthesizers basically use the look-up table LUT and the digital-to-analog converter DAC to generate the output signal. Digital devices such as the look-up table LUT and the digital-to-analog converter have quantization errors and phase truncation errors, and these errors will be As a result, the waveform signals generated by the direct digital frequency synthesizer all have large spurs. [0003] However, in modern signal systems, higher requirements are put forward for the output waveform of the d...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03K19/17728
CPCH03K19/17728
Inventor 赵亮亮杨陈汪钰谭龙龙
Owner INST OF ELECTRONICS ENG CHINA ACAD OF ENG PHYSICS