CN103944566A - Method and circuit for achieving DDS amplitude modulation output - Google Patents
Method and circuit for achieving DDS amplitude modulation output Download PDFInfo
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- CN103944566A CN103944566A CN201410176015.3A CN201410176015A CN103944566A CN 103944566 A CN103944566 A CN 103944566A CN 201410176015 A CN201410176015 A CN 201410176015A CN 103944566 A CN103944566 A CN 103944566A
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- dds
- dac
- output
- latch
- data
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Abstract
The invention discloses a method for achieving DDS amplitude modulation output. The method comprises the steps that a, a DDS is selected; b, a DAC of a parallel interface is selected; c, a parallel latch is selected, and the output end of the latch is connected with the data input end of the DAC; d, a resistor RS is connected between the output of the DAC and the DAC Rset of the DDS in series; e, the DDS and the latch are controlled by an MCU. A circuit for achieving DDS amplitude modulation output comprises the MCU, the DDS, the DAC and the resistor RS, and is characterized in that the latch is included; the input end of the latch is connected with the MCU through the parallel interface, and the output end of the latch is connected to the input end of the DAC through the parallel interface; the MCU controls the changes of output voltages of the DAC through the latch in a buffer mode, DAC full-range currents in a DDS sheet are changed, and DDS amplitude modulation output is achieved. Precise amplitude modulation on DDS output signals is achieved through the DAC.
Description
Technical field
The present invention relates to the signal amplitude modulation technique of electronic information field, particularly a kind of method and circuit of realizing the output of DDS am signals.
Background technology
DDS is Direct Digital synthesizer, owing to having the advantages such as output frequency is easy to adjust, frequency resolution is high, change-over time is short, is widely used in using as signal generator in communication and instrument field.Conventionally the amplitude of signal generator output is to need continually varying, and sometimes needs to produce am signals.But owing to being subject to the restriction of performance index and complexity in circuits, commercial DDS chip itself does not have direct amplitude modulation(PAM) function.
For realizing the amplitude modulation(PAM) output of DDS, conventional method is at the additional variable-gain amplification circuit of DDS output at present, changes amplitude output signal by the change in gain of controlling amplifying circuit.This method is convenient to large-signal output, and for small-signal output, also needs to introduce attenuator, certainly will will increase corresponding control circuit, make circuit complexity raising, reliability decrease, and cost of manufacture further improves; More seriously,, after introducing amplifier, the noiseproof feature of signal also can obviously decline.
Summary of the invention
In order to overcome the shortcoming of above-mentioned technical problem, the invention provides a kind of DDS amplitude modulation(PAM) output implementation method flexible, excellent performance of controlling.
The method that realizes the output of DDS amplitude modulation(PAM) of the present invention, its special feature is, comprises the following steps: a. chooses a Direct Digital Synthesizer DDS, the reference voltage of establishing current mode DAC in its sheet is V
rEF, full scale electric current is I, I arranges end for linking pin " the DAC R of chip exterior
set"; B. the high-speed DAC of choosing a parallel input interface of band, the analog output voltage of establishing after its number-Mo changes is V
dAC; C. the latch of choosing a parallel input, parallel output, the data bits of latch is identical with the resolution figure place of high-speed DAC, and the data output end of latch is connected with the parallel data input of high-speed DAC; D. choose a resistance R
s, R
san end be connected on the analog voltage output of high-speed DAC, the other end is connected to " the DAC R of DDS
set" end; E. choose a microcontroller, control for the output voltage of the output frequency to DDS and high-speed DAC.Direct Digital Synthesizer DDS is for generation of the signal output of setpoint frequency; The corresponding change of amplitude output signal of the variation control DDS of high-speed DAC output voltage, realizes amplitude modulation output.
The method that realizes the output of DDS amplitude modulation(PAM) of the present invention, in described step e, MCU is connected with DDS by serial line interface or parallel interface, sets DDS output signal frequency; MCU is connected with latch input by parallel interface, writes data in latch; High-speed DAC is operated in straight-through, the direct translative mode of data, the data transaction of in time latch being sent here becomes analog voltage output, in the variation control DDS sheet of this analog voltage, the full scale electric current I of current mode DAC changes thereupon, obtains the signal of the setpoint frequency of amplitude modulation(PAM) at the output of DDS.
The full scale Current calculation Coefficient m providing according to DDS databook, can obtain the full scale electric current I and sheet high-speed DAC output voltage V outward of current mode DAC in DDS sheet
dACpass be:
I＝m×(V
REF-V
DAC)/R
S…………(1)
DDS amplitude output signal V
outalso with its external load resistance R
lrelevant, expression formula is:
V
out＝I×R
L＝m×(V
REF-V
DAC)×R
L/R
S…………(2)
Correspondingly, in order to overcome the shortcoming of above-mentioned technical problem, the invention provides a kind of circuit of realizing the output of DDS amplitude modulation(PAM) of practicality.
The circuit of realizing DDS amplitude modulation(PAM) output of the present invention, comprises microcontroller, for generation of the DDS of setpoint frequency signal, for controlling high-speed DAC and the resistance R of current mode DAC full scale electric current in DDS sheet
s, its special feature is: also comprise latch; The input of described latch is connected with MCU by parallel interface, and latch data output is connected to the data input pin of high-speed DAC by parallel interface; The analog voltage output contact resistance R of described high-speed DAC
sone end, R
sthe sheet of another termination DDS in current mode DAC full scale electric current pin " DAC R is set
set"; Described MCU sends into the data of latch by programming Control.Described high-speed DAC is operated in straight-through, the direct translative mode of data, and DDS amplitude output signal is changed fast with the input data of high-speed DAC, realizes amplitude modulation(PAM); Described resistance R
sfor limiting the numerical value that arranges of the interior DAC full scale electric current I of DDS sheet, avoid the excessive DDS of burning out because of I.
The invention has the beneficial effects as follows: between MCU and latch, adopt parallel interface connected mode between latch and high-speed DAC, high-speed DAC is operated in straight-through, the direct translative mode of data, make total-Mo short change-over time, can realize fast high accuracy amplitude modulation(PAM), avoid the situation that occurs that changes in amplitude lags behind; Latch is connected between MCU and high-speed DAC, by MCU and high-speed DAC isolation, avoid the clock of MCU and the impact of the data of variation at a high speed on DDS output signal spectrum performance, can reduce component and the amplitude of spurious signal, obtained comparatively pure output signal.
Brief description of the drawings
Accompanying drawing is electric theory diagram of the present invention.
In figure: 1MCU, 2 Direct Digital Synthesizer DDS, 3 latchs, 4 high-speed DACs.
Embodiment
By reference to the accompanying drawings, realize the method for DDS amplitude modulation(PAM) output, carry out according to following steps: a. chooses a Direct Digital Synthesizer DDS (2), produce the signal that needs frequency; If the reference voltage of current mode DAC is V in DDS sheet
rEF, full scale electric current is I, this I arranges end for linking pin " the DAC R of chip exterior
set"; B. the high-speed DAC (4) of choosing a parallel input interface of band, establishing its analog output voltage is V
dAC; C. the latch (3) of choosing a parallel input, parallel output, the data bits of latch is identical with the resolution figure place of high-speed DAC, and the data output end of latch is connected with the parallel data input of high-speed DAC; D. choose a resistance R
s, R
san end be connected on the analog voltage output of high-speed DAC, the other end is connected to " the DAC R of DDS
set" end; E. choose a microcontroller (1), be connected with DDS by serial line interface or parallel interface, MCU is connected with latch input by parallel interface.
In the above-mentioned method that realizes the output of DDS amplitude modulation(PAM), Direct Digital Synthesizer DDS produces under the control of MCU needs the output of the signal of frequency; MCU is written to DDS amplitude output signal data in latch by parallel interface; High-speed DAC is operated in straight-through, the direct translative mode of data, and the data transaction of in time latch being sent here becomes analog voltage output, through resistance R
sin rear control DDS sheet, the full scale electric current I of current mode DAC changes by setting rule, and then controls the output signal voltage amplitude of DDS, realizes amplitude modulation output.
As shown in drawings, provided the circuit of the DDS of realization amplitude modulation(PAM) output of the present invention, it comprises MCU (1), DDS (2), latch (3), high-speed DAC (4), resistance R
s, two load resistance R of DAC in DDS sheet
l.Shown MCU is connected with DDS by serial line interface or parallel interface, is connected with latch input by parallel interface; The data output end of latch is connected with the parallel data input of high-speed DAC; Analog voltage output and the R of high-speed DAC
sbe connected, R
sthe other end be connected to " the DAC R of DDS
set" end; Am signals is IOUT, the output of IOUTB pin from DDS with balance mode.
By the analysis that circuit is carried out, can draw DDS amplitude output signal V
outexpression formula be:
V
out＝I×R
L＝m×(V
REF-V
DAC)×R
L/R
S
Utilize the amplitude data that high-speed DAC is sent MCU here in time to convert high-precision analog voltage to, control the full scale curent change of DAC in DDS sheet, thereby accurately control the output signal voltage amplitude of DDS, realize amplitude modulation output; Be connected to the latch between MCU and high-speed DAC, by MCU and DAC isolation, reduced the impact of MCU on DDS quality of output signals, obtain comparatively pure output signal.
Claims (3)
1. a method that realizes the output of DDS amplitude modulation(PAM), is characterized in that, comprises the following steps:
A. choose a Direct Digital Synthesizer DDS, the reference voltage of establishing current mode DAC in its sheet is V
rEF, full scale electric current is I, I arranges end for linking pin " the DAC R of chip exterior
set";
B. the high-speed DAC of choosing a parallel input interface of band, the analog output voltage of establishing after its number-Mo changes is V
dAC;
C. the latch of choosing a parallel input, parallel output, the data bits of latch is identical with the resolution figure place of high-speed DAC, and the data output end of latch is connected with the parallel data input of high-speed DAC;
D. choose a resistance R
s, R
san end be connected on the analog voltage output of high-speed DAC, the other end is connected to " the DAC R of DDS
set" end;
E. choose a microcontroller, control for the output voltage of the output frequency to DDS and high-speed DAC.
2. the method that realizes the output of DDS amplitude modulation(PAM) according to claim 1, is characterized in that, in described step e, MCU is connected with DDS by serial line interface or parallel interface, sets DDS output signal frequency; MCU is connected with latch input by parallel interface, writes data in latch; High-speed DAC is operated in straight-through, the direct translative mode of data, the data transaction of in time latch being sent here becomes analog voltage output, in the variation control DDS sheet of this analog voltage, the full scale electric current I of current mode DAC changes thereupon, obtains the signal of the setpoint frequency of amplitude modulation(PAM) at the output of DDS.
3. realize a circuit for DDS amplitude modulation(PAM) output, comprise microcontroller, for generation of the DDS of setpoint frequency signal, for controlling high-speed DAC and the resistance R of current mode DAC full scale electric current in DDS sheet
s, it is characterized in that: also comprise latch; The input of described latch is connected with MCU by parallel interface, and latch data output is connected to the data input pin of high-speed DAC by parallel interface; The analog voltage output contact resistance R of described high-speed DAC
sone end, R
sthe sheet of another termination DDS in current mode DAC full scale electric current pin " DAC R is set
set"; Described MCU sends into the data of latch by programming Control.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410176015.3A CN103944566B (en) | 2014-04-24 | 2014-04-24 | A kind of method realizing the output of DDS amplitude modulation(PAM) and circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410176015.3A CN103944566B (en) | 2014-04-24 | 2014-04-24 | A kind of method realizing the output of DDS amplitude modulation(PAM) and circuit |
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| Publication Number | Publication Date |
|---|---|
| CN103944566A true CN103944566A (en) | 2014-07-23 |
| CN103944566B CN103944566B (en) | 2017-03-01 |
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ID=51192082
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201410176015.3A Expired - Fee Related CN103944566B (en) | 2014-04-24 | 2014-04-24 | A kind of method realizing the output of DDS amplitude modulation(PAM) and circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104391142A (en) * | 2014-12-22 | 2015-03-04 | 永新电子常熟有限公司 | Novel convenient signal generator |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN202957806U (en) * | 2012-12-26 | 2013-05-29 | 黑龙江工程学院 | FPGA-based DDS signal generator |
-
2014
- 2014-04-24 CN CN201410176015.3A patent/CN103944566B/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN202957806U (en) * | 2012-12-26 | 2013-05-29 | 黑龙江工程学院 | FPGA-based DDS signal generator |
Non-Patent Citations (2)
| Title |
|---|
| 司朝良: "用DDS激励的双环频率合成器", 《电子元器件应用》 * |
| 司朝良: "精确控制DDS输出信号幅度的一种新方法", 《今日电子》 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104391142A (en) * | 2014-12-22 | 2015-03-04 | 永新电子常熟有限公司 | Novel convenient signal generator |
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| CN103944566B (en) | 2017-03-01 |
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Address after: 250023 Shandong, Ji'nan Flyover District School Road, No. 5 Applicant after: Shandong Jiaotong College Address before: 250357 Ji'nan, Changqing Province University of science and Technology Park, Haitang Road, No. 5001, No. Applicant before: Shandong Jiaotong College |
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Granted publication date: 20170301 Termination date: 20180424 |