CN103199825B - Method and circuit for regulating and controlling DDS output signal amplitudes based on DCPs - Google Patents

Abstract

The method for regulating and controlling DDS output signal amplitudes based on DCPs includes: a, the DDS is selected and used; b, four DCPs are selected, after connection in series and parallel of the DCPs, the DCPs and resistors are connected in parallel to form an equivalent DCP; c, the equivalent DCP and a current-limiting resistor are connected in series between a DACRset of the DDS and the ground; and d, a MCU is used for controlling the DDS and the DCPs. A circuit for regulating and controlling the signal amplitudes comprises the MCU, the DDS, the four DCPs, the DDS load resistor R1, and the DDS load resistor R2 and is characterized by comprising two auxiliary resistors. The DCP1 is connected with the DCP2 in parallel, the DCP3 is connected with the DCP4 in parallel, two groups of DCPs connected in parallel are connected in series and then connected with the resistors in parallel to form the equivalent DCP, and the MCU controls tapping variation of the DCPs and changes resistance of the equivalent DCP to cause changes of a DAC full scale current in the DDS to achieve the purpose that the output signal amplitudes are regulated. Regulation and control of the DDS output signal amplitudes can be achieved through the DCPs, wherein the regulation and control are high in resolution and relatively wide in range.

Description

Based on DDS amplitude output signal regulate and control method and the circuit for regulating and controlling of DCP

Technical field

The present invention relates to the signal amplitude control technique of electronic information field, particularly a kind of DDS amplitude output signal regulate and control method based on DCP and circuit for regulating and controlling.

Background technology

DDS is as Direct Digital Synthesizer, and output frequency is easy to adjust, and low in energy consumption, resolution is high, change-over time is short, is generally designed to signal generator, be widely used in communication with electronic equipment in.In much equipment, the amplitude of signal needs change, but due to the restriction by performance index and complexity in circuits, commercial DDS chip does not arrange direct amplitude adjusted function.

For addressing this problem, method conventional at present adds amplifying circuit at the output of DDS, realizes the regulation and control to signal amplitude by the gain controlling amplifying circuit.This method is convenient to the amplitude adjusted realizing large-signal, and is difficult to regulate and control the amplitude of small-signal.And circuit is comparatively complicated, cost is high; 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 that a kind of circuit is simple, regulation and control are flexibly based on the DDS amplitude output signal regulate and control method of DCP.

DDS amplitude output signal regulate and control method based on DCP of the present invention, its special feature is, comprise the following steps: a. chooses a Direct Digital Synthesizer DDS, if in its sheet the full scale electric current of current mode DAC be I, this I pin " the DAC R of end for linking chip exterior is set _set"; B. 4 same model digital regulation resistance DCP are chosen, the R of wherein 2 DCP _wend connects together, R _lend also connects together, and forms DCP parallel form; The R of other 2 DCP _wend connects together, R _lend also connects together; The DCP of two groups of parallel connections connects again, then with an auxiliary resistance R ₃parallel connection, forms a high-resolution, high-precision equivalent DCP, if the all-in resistance of each DCP is R _t, tap number is t, and the variable resistance of equivalent DCP is R _e; C. an equivalent DCP and current-limiting resistance R ₄after series connection, then be connected in " the DACR of DDS _set" end and " " between; D. a microcontroller is chosen, for controlling the output frequency of DDS and the tap position of 4 DCP chips.Direct Digital Synthesizer DDS exports for generation of the signal of setpoint frequency; The change of each DCP tap position, makes equivalent DCP and current-limiting resistance R ₄total resistance value R after series connection changes thereupon, and the change of R causes DAC full scale electric current I change in DDS sheet, and the load resistance of DAC obtains the voltage signal of the setpoint frequency of changes in amplitude.

DDS amplitude output signal regulate and control method based on DCP of the present invention, the actual tap position n round numbers of described equivalent DCP, span is 0 to 2 (t-1); MCU changes the tap position of equivalent DCP by the value of control n.DCP is in parallel for improving the resolution of digital regulation resistance, the total tap number of DCP series connection for expanding equivalent DCP of two groups of parallel connections.Can show that the resistance of equivalent DCP is by analyzing:

$R_E=\frac{n{R}_T}{2(t-1)}//R_3\·\·\·\left(1\right)$

According to the full scale Current calculation Coefficient m that DDS databook provides, the variable resistor R of DAC full scale electric current I and equivalent DCP in DDS sheet can be obtained _ewith current-limiting resistance R ₄between relationship expression be:

$I=\frac{m}{R_E+R_4}\·\·\·\left(2\right)$

Correspondingly, in order to overcome the shortcoming of above-mentioned technical problem, the invention provides that a kind of circuit is simple, regulation and control are flexibly based on the DDS amplitude output signal circuit for regulating and controlling of DCP.

DDS amplitude output signal circuit for regulating and controlling based on DCP of the present invention, comprises microcontroller, the DDS for generation of setpoint frequency signal, 4 same model DCP, DDS output load resistance R for DAC full scale electric current in control DDS sheet ₁and R ₂, its special feature is: also comprise auxiliary resistance R ₃, R ₄; The R of DCP1 in described 4 same model DCP _wthe R of end and DCP2 _wend is in parallel, the R of DCP1 _lthe R of end and DCP2 _lend is in parallel; The R of DCP3 _wthe R of end and DCP4 _wend is in parallel, the R of DCP3 _lthe R of end and DCP4 _lend is in parallel; The R of DCP2 _lend links the R of DCP3 _wend; The R of DCP1 _wthe R of end and DCP4 _lauxiliary resistance R in parallel between end ₃; The R of DCP1 _win the sheet of termination DDS, DAC full scale electric current arranges pin " DAC R _set", the R of DCP4 _ltermination auxiliary resistance R ₄one end, R ₄other end ground connection; The R of all DCP _hhold all unsettled; Described MCU controls the tap position change of each DCP, and the tap position of DCP1 and DCP2 is identical all the time, and the tap position of DCP3 and DCP4 is identical all the time.

DDS amplitude output signal circuit for regulating and controlling based on DCP of the present invention, in described 4 same model DCP, DCP1 and DCP2 is in parallel, and DCP3 and DCP4 is in parallel; The DCP of two groups of parallel connections connects again, and with auxiliary resistance R ₃parallel connection, forms an equivalent DCP; The actual tap position n round numbers of this equivalent DCP, span is 0 to 2 (t-1).DCP is in parallel for improving the resolution of digital regulation resistance, to improve the regulation and control resolution of DDS amplitude output signal; The total tap number of DCP series connection for expanding equivalent DCP of two groups of parallel connections, to expand the modification scope of DDS amplitude output signal; Described auxiliary resistance R ₃for improving the change linearity of DAC full scale electric current I in DDS sheet, improve the control accuracy of DDS amplitude output signal; Described auxiliary resistance R ₄numerical value is set for what limit DAC full scale electric current I in DDS sheet, avoids burning out DDS because I is excessive.

The invention has the beneficial effects as follows: combined by the series and parallel of 4 same model digital regulation resistance DCP, form a high-resolution, change that high-precision equivalent DCP removes DAC full scale electric current in control DDS sheet, realize the flexible modulation of the high-resolution to DDS amplitude output signal, wide region.

Accompanying drawing explanation

Accompanying drawing is electric theory diagram of the present invention.

In figure: 1MCU, 2 Direct Digital Synthesizer DDS, 3 the 1st digital regulation resistance DCP1,4 the 2nd digital regulation resistance DCP2,5 the 3rd digital regulation resistance DCP3,6 the 4th digital regulation resistance DCP4,7 equivalent DCP.

Embodiment

By reference to the accompanying drawings, the DDS amplitude output signal regulate and control method based on DCP of the present invention, carries out according to following steps: a. chooses a Direct Digital Synthesizer DDS (2), produces the signal needing frequency; If in DDS sheet the full scale electric current of current mode DAC be I, this I pin " the DAC R of end for linking chip exterior is set _set"; B. choose the digital regulation resistance DCP of 4 same models, DCP1 (3) is in parallel with DCP2 (4), and DCP3 (5) is in parallel with DCP4 (6); The DCP of these two groups of parallel connections connects again, then in parallel with auxiliary resistance R3, forms a high-resolution, high-precision equivalent DCP; If the all-in resistance of each DCP is R _t, tap number is t, and the variable resistance of equivalent DCP is R _e, the actual tap position n round numbers of this equivalent DCP, span is 0 to 2 (t-1); C. an equivalent DCP and current-limiting resistance R ₄after series connection, then be connected in " the DAC R of DDS _set" end and " " between; The resistance R of equivalence DCP _ewith current-limiting resistance R ₄sum determines the value of I; D. a microcontroller (1) is chosen, for controlling the output frequency of DDS and the tap position of 4 DCP chips.

In above-mentioned DDS amplitude output signal regulate and control method, Direct Digital Synthesizer DDS exports for generation of the signal of setpoint frequency; The change of each DCP tap position, causes the value of the tap position n of equivalent DCP to change, equivalent resistance R _ewith current-limiting resistance R ₄total resistance value R after series connection changes thereupon, and the change of R causes DAC full scale electric current I change in DDS sheet, and DDS amplitude output signal follows the proportional change of I.

As shown in drawings, give the DDS amplitude output signal circuit for regulating and controlling based on DCP of the present invention, it comprises MCU (1), DDS (2), first digit potentiometer DCP1 (3), second digit potentiometer DCP2 (4), third digit potentiometer DCP3 (5), fourth digit potentiometer DCP4 (6), auxiliary resistance R ₃and R ₄, the load resistance R of DAC in DDS sheet ₁and R ₂.4 shown digital regulation resistance DCP models are identical, the R of DCP1 _w, R _lend respectively with the R of DCP2 _w, R _lend is in parallel; The R of DCP3 _w, R _lend respectively with the R of DCP4 _w, R _lend is in parallel; The R of DCP2 _lend links the R of DCP3 _wend, is together in series the DCP of two groups of parallel connections; The R of DCP1 _wthe R of end and DCP4 _lauxiliary resistance R in parallel again between end ₃; The R of DCP1 _win termination DDS sheet, DAC full scale electric current arranges pin " DAC R _set"; The R of DCP4 _ltermination auxiliary resistance R ₄one end, R ₄other end ground connection; The R of all DCP _hhold all unsettled; MCU controls the tap position change of each DCP, and the tap position of DCP1 and DCP2 is identical all the time, and the tap position of DCP3 and DCP4 is also identical all the time.

By the analysis carried out circuit, can show that the expression formula of DAC full scale electric current I in DDS sheet is:

$I=\frac{m}{R_E+R_4}=\frac{m}{[\frac{n{R}_T}{2(t-1)}//R_3]+R_4}$

The parallel connection of DCP, makes the resistance adjustment resolution of equivalent DCP by R _t/ (t-1) is doubled, and the regulation and control resolution of DDS amplitude output signal is improved; The DCP series connection of two groups of parallel connections, makes total tap number of equivalent DCP be expanded to (2t-1) by t, expands the modification scope of DDS amplitude output signal; Auxiliary resistance R in parallel ₃contribute to the change linearity improving I, improve the control accuracy of DDS amplitude output signal; The auxiliary resistance R of series connection ₄restriction I arranges numerical value, avoids burning out DDS because I is excessive.

Claims (4)

1., based on the DDS amplitude output signal regulate and control method of DCP, it is characterized in that, comprise the following steps:

A. choose a Direct Digital Synthesizer DDS, if in its sheet the full scale electric current of current mode DAC be I, this I pin " the DAC R of end for linking chip exterior is set _set";

B. 4 same model digital regulation resistance DCP are chosen, the R of wherein 2 DCP _wend connects together, R _lend also connects together, and forms DCP parallel form; The R of other 2 DCP _wend connects together, R _lend also connects together; The DCP of two groups of parallel connections connects again, then with an auxiliary resistance R ₃parallel connection, forms a high-resolution, high-precision equivalent DCP, if the all-in resistance of each DCP is R _t, tap number is t, and the variable resistance of equivalent DCP is R _e;

C. an equivalent DCP and current-limiting resistance R ₄after series connection, then be connected in " the DAC R of DDS _set" end and " " between;

D. a microcontroller is chosen, for controlling the output frequency of DDS and the tap position of 4 DCP chips.

2. the DDS amplitude output signal regulate and control method based on DCP according to claim 1, it is characterized in that: the actual tap position n round numbers of described equivalent DCP, span is 0 to 2 (t-1); MCU changes the tap position of equivalent DCP by the value of control n.

3., based on the DDS amplitude output signal circuit for regulating and controlling of DCP, comprise microcontroller, the DDS for generation of setpoint frequency signal, 4 same model DCP, DDS output load resistance R for DAC full scale electric current in control DDS sheet ₁and R ₂, it is characterized in that: also comprise auxiliary resistance R ₃, R ₄; The R of DCP1 in described 4 same model DCP _wthe R of end and DCP2 _wend is in parallel, the R of DCP1 _lthe R of end and DCP2 _lend is in parallel; The R of DCP3 _wthe R of end and DCP4 _wend is in parallel, the R of DCP3 _lthe R of end and DCP4 _lend is in parallel; The R of DCP2 _lend links the R of DCP3 _wend; The R of DCP1 _wthe R of end and DCP4 _lauxiliary resistance R in parallel between end ₃; The R of DCP1 _win the sheet of termination DDS, DAC full scale electric current arranges pin " DAC R _set", the R of DCP4 _ltermination auxiliary resistance R ₄one end, R ₄other end ground connection; The R of all DCP _hhold all unsettled; Described MCU controls the tap position change of each DCP, and the tap position of DCP1 and DCP2 is identical all the time, and the tap position of DCP3 and DCP4 is identical all the time.

4. the DDS amplitude output signal circuit for regulating and controlling based on DCP according to claim 3, is characterized in that: in described 4 same model DCP, DCP1 and DCP2 is in parallel, and DCP3 and DCP4 is in parallel; The DCP of two groups of parallel connections connects again, and with auxiliary resistance R ₃parallel connection, forms an equivalent DCP; The actual tap position n round numbers of this equivalent DCP, span is 0 to 2 (t-1).