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Frequency synthesis source applied by DDS short-wave transmitter based on CPLD design

A short-wave transmitter and frequency synthesis technology, applied in electrical components, transmission systems, etc., can solve problems such as poor filtering performance of broadband low-pass filters, and achieve easy frequency setting and working mode conversion, fast response, Effect of reducing unevenness

Inactive Publication Date: 2011-09-28
WUHAN UNIV OF TECH
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Problems solved by technology

If the frequency tracking narrowband frequency selective filter is used, because of its high Q value, the resonance point is always located at the center frequency point, which will fundamentally solve the problem of poor filtering performance of the wideband low-pass filter

Method used

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  • Frequency synthesis source applied by DDS short-wave transmitter based on CPLD design
  • Frequency synthesis source applied by DDS short-wave transmitter based on CPLD design
  • Frequency synthesis source applied by DDS short-wave transmitter based on CPLD design

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Embodiment Construction

[0034] The present invention will be further described below in conjunction with the embodiments and accompanying drawings.

[0035] The frequency synthesis source for the DDS short-wave transmitter that adopts CPLD design that the present invention provides, its structure is as follows Figure 5 Shown: including direct digital synthesis circuit, high-speed DAC conversion circuit, tracking filter and gain control circuit, phase-locked crystal oscillator source, and controller. in: Figure 5 The middle dashed box (1) is a direct digital frequency synthesizer (DDS) designed by a complex programmable device, which is composed of a data register, a phase accumulator and a sinusoidal waveform look-up table sequentially connected by electrical signals. The dashed box (2) is a high-speed DAC conversion circuit designed by a complex programmable device, refer to figure 2 , which is composed of registers and bit switching switches, R-2R resistor networks and buffer amplifiers connec...

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Abstract

The invention relates to a frequency synthesis source applied by a DDS short-wave transmitter based on a CPLD design. The frequency synthesis source mainly comprises a direct digital synthesis circuit, a high-speed DAC transformation circuit, a tracking filter circuit and a gain control circuit, a controller and a phase locked crystal oscillator. According to the invention, the high-speed DAC transformation circuit converts frequency data output by direct digital synthesis circuit to a sine frequency signal; and the tracking filter circuit filters components of stray and harmonic wave in the high-speed DAC transformation circuit, and the gain control circuit enables the output of the direct digital synthesis circuit to be stable in amplitude within a frequency range. In addition, the controller comprises a microprocessor and a microcomputer, wherein the microprocessor is connected with the microcomputer through an interface circuit of the microcomputer, and frequency arrangement and transition of working mode are realized by an upper computer. The phase locked crystal oscillator generates a clock source signal with ultrahigh frequency and high stability, and the clock source signal is used as a clock signal of the frequency synthesis source. The frequency synthesis source applied by a DDS short-wave transmitter based on a CPLD design provided in the invention has advantages of high frequency accuracy and high distinguishability, short switching time of frequency signals, constant output amplitude, and simple and high-reliable circuit.

Description

technical field [0001] The invention relates to the technical field of frequency synthesizers, in particular to a frequency synthesis signal source for a short-wave band transmitter using a direct digital frequency synthesis technology based on a complex programmable device (CPLD). Background technique [0002] At present, in the short-wave wireless transmitter, a frequency synthesis source is required to generate the required short-wave frequency excitation signal of 1.5MHz to 30MHz, and its characteristics are directly related to the performance index of the short-wave wireless transmitter. Now, with the extensive use of short-wave communication equipment, the channel is becoming more and more crowded, and the interference is increasing day by day, resulting in the continuous deterioration of the electromagnetic environment. We require frequency synthesis sources with lower noise and smaller spurs. In addition, the development of new short-wave communication technologies s...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04B1/02
Inventor 陈永泰刘泉唐静钟小虎
Owner WUHAN UNIV OF TECH
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