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Digital modulation signal generator based on DDS

A digital modulation signal, digital modulation technology, applied in the direction of digital function generator, angle modulation components, etc., can solve the problem of inconvenient digital modulation signal, etc.

Inactive Publication Date: 2010-07-14
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, it cannot easily generate digitally modulated signals

Method used

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  • Digital modulation signal generator based on DDS
  • Digital modulation signal generator based on DDS
  • Digital modulation signal generator based on DDS

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] 1. FM signal, FSK modulation signal and frequency sweep signal

[0028] In this example, if figure 2 As shown, the digital modulation signal output by the DDS-based digital modulation signal generator includes frequency modulation (FM), frequency sweep (SWEEP), frequency shift keying (FSK), phase shift keying (PSK) and amplitude modulation (AM) and other five digital modulation signals.

[0029] Such as figure 2 As shown, the DDS-based digital modulation signal generator includes a high-speed DDS 2 composed of a high-speed phase accumulator 201, a phase adder 202, a high-speed waveform RAM 203, a D / A converter 204, and a low-pass filter 205. The high-speed waveform Corresponding carrier waveform data is stored in the RAM 203; the low-speed DDS 3 composed of the low-speed phase accumulator 301 and the low-speed waveform RAM 302, the corresponding modulation waveform data is stored in the low-speed waveform RAM 302, and the low-speed sampling clock signal clk L Under...

Embodiment 2

[0043] 2. Phase shift keying modulation signal

[0044] Phase shift keying modulation (PSK) refers to a modulation method in which the phase of the carrier changes with the change of the digital modulation signal.

[0045] In this example, if image 3 As shown, on the basis of Embodiment 1, the digital modulation signal generator based on DDS of the present invention also includes a PSK phase selection switch 9, and also includes a phase adder 202 in the high-speed DDS 2, and the phase adder 202 is located at the high-speed phase accumulation Between the device 201 and the high-speed waveform RAM 203;

[0046] When the output waveform is a PSK modulation signal, according to the selected carrier waveform, the corresponding carrier waveform data is stored in the high-speed waveform RAM 203; according to the set carrier frequency, the frequency control word K is calculated according to formula (4) 1 , by controlling the FSK frequency selection switch and the FSK / FM selection s...

Embodiment 3

[0051] 3. AM signal

[0052] AM modulation refers to a modulation method in which the amplitude of the carrier varies with the amplitude of the modulating waveform.

[0053] In this example, if Figure 4 As shown, on the basis of Embodiment 2, the DDS-based digital modulation signal generator of the present invention also includes an amplitude modulation operation circuit 10 and an AM / FM selection switch 11, and the AM / FM selection switch 11 is connected to the high-speed waveform RAM 203 Between the D / A converter 204 , the carrier waveform data D output by the high-speed waveform RAM 203 is used as one input, and the output is connected to the D / A converter 204 .

[0054] The modulation waveform data A is in the amplitude modulation operation circuit 10 and the modulation degree control factor A depth After multiplication, it is multiplied with the carrier waveform data D output by the high-speed waveform RAM 203 in the high-speed DDS 2, and the multiplication result is add...

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Abstract

The invention discloses a digital modulation signal generator based on DDS; a modulation source selection switch selects modulation waveform data and outputs the same to a frequency modulation operation circuit, is multiplied by a frequency step factor Kstep, and then pluses an initial frequency control word Kstart and serves as a frequency control word KH of high-speed DDS; the high-speed DDS is produced under the control of a sampling clock clkH, the frequency control word KH is accumulated in a high-speed phase accumulator, the high MH bit thereof is output to the high-speed waveform RAM and serves as a data address of the high-speed waveform RAM, outputs modulation waveform data, passes through D / A conversion and a low-pass filter and outputs digital modulation signals corresponding to the modulation waveform. The digital modulation signal generator based on DDS can regulate the modulation signal frequency only by changing a low-speed frequency control word KL, can change the modulation waveform only by changing the storage waveform data of the low-speed waveform RAM, can changing the carrier frequency and the modulation depth only by regulating the initial frequency control word Kstart and the step frequency control word Kstep, and has high precision and high switching speed because the control words are digital signals.

Description

technical field [0001] The invention relates to a signal generator, in particular to a signal generator for generating output digital modulation signals. Background technique [0002] In modern communication systems, baseband signals cannot meet the requirements of modern communication due to reasons such as transmission distance and transmission efficiency. In order to transmit information effectively and reliably, it is often necessary to move the baseband spectrum of the low-frequency signal to an appropriate or designated frequency band, which is called modulation. Traditional analog modulation is difficult to meet the requirements of high precision and high speed. As modern communication enters the digital age, analog modulation is increasingly replaced by advanced digital modulation. [0003] Direct digital synthesis (DDS) technology is a frequency synthesis technology based on waveform storage. It has the characteristics of short frequency conversion time, high resol...

Claims

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Application Information

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IPC IPC(8): G06F1/03H03C3/09
Inventor 刘科田书林肖寅东黄建国王厚军
Owner UNIV OF ELECTRONICS SCI & TECH OF CHINA
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