CN101131594A - A DDS signal generator and its waveform storage depth control method - Google Patents

Abstract

The invention relates to a DDS signal generator and a waveform storage depth control method thereof. The depth of the waveform storage space is set according to the length of the waveform data, and the waveform data is stored in the waveform storage space of the corresponding depth; one of the waveform storage spaces The waveform data is stored externally in a certain order; the length of the externally stored waveform data is obtained; the phase address of the next waveform data point is accumulated according to the phase address of the initial waveform data point of the externally stored waveform data; according to the length of the waveform data, The phase address is mapped to the address of the waveform data stored externally; the waveform data stored externally is processed by digital-to-analog conversion to construct a waveform output. It is used to reconstruct a memory depth control mechanism that does not distort the waveform and can make full use of the storage space according to the number of arbitrary waveform sampling points, which can meet the requirements of storing more short waveforms and meet the requirements of storing long waveforms .

Description

A DDS signal generator and its waveform storage depth control method

technical field

The present invention relates to signal generator technology, in particular to the control of waveform storage depth of Direct Digital Frequency Synthesis (DDS: DirectDigital Frequency Synthesis) signal generator, specifically a DDS signal generator and its waveform storage depth control method.

Background technique

As shown in Figure 1, the overall architecture of a DDS signal generator generally includes a man-machine interface, a waveform memory, a frequency synthesis unit, a waveform control unit and an analog unit. The waveform memory stores the sampling points within a waveform period; the frequency synthesis unit generates different waveform phase transformation points according to the frequency setting, and extracts the sampling point amplitude of the corresponding phase from the waveform memory; the waveform control unit controls the amplitude of the waveform. Offset and other related parameters; the analog unit reconstructs the sampling point into an analog signal for output.

However, in fact, not all waveforms need to occupy all the waveform storage space to reconstruct a waveform that meets the requirements. Moreover, for arbitrary waveforms, the internal waveform storage space provided by the DDS signal generator for users is a fixed-length waveform storage space. For arbitrary waveforms whose waveform sampling points are less than this length, a storage space has to be occupied, which is very important. wasteful. Arbitrary waveforms longer than this length cannot be stored in one storage space, which causes a huge waste of storage space because the remaining storage space cannot be used, and cannot meet the storage requirements of arbitrary waveforms of different lengths.

Contents of the invention

The present invention provides a DDS signal generator and its waveform storage depth control method, which are used to reconstruct a storage depth control mechanism that does not distort the waveform and fully utilizes the storage space according to the number of arbitrary waveform sampling points. It can meet the requirements for storing more short waveforms and also meet the requirements for storing long waveforms.

In order to achieve the above-mentioned purpose of the invention, one of the purposes of the present invention is to provide a method for controlling the waveform storage depth of a DDS signal generator. The method includes the following steps: setting the depth of the waveform storage space according to the length of the waveform data, and storing the waveform data into the waveform storage space of the corresponding depth; store a waveform data in the waveform storage space externally in a certain order; obtain the length of the waveform data stored externally; accumulate the phase address of the initial waveform data point according to the waveform data stored externally Get the phase address of the next waveform data point; according to the length of the waveform data, map the phase address to the address of the waveform data stored externally; convert the waveform data stored externally to construct a waveform output.

The acquisition of the length of the waveform data stored externally includes: judging whether the request to read the waveform data exceeds the depth of the corresponding waveform storage space, and if so, scrolling back to the initial position of the external storage to read the waveform data points.

Another object of the present invention is to provide a DDS signal generator, including: a control device, a waveform memory, a waveform processing device, an analog unit, a man-machine interface device and a display device; The processing device, the human-machine interface device and the display device are connected, and the waveform processing device is connected with the analog unit; the DDS signal generator also includes: a memory depth control unit, connected with the control device, used According to the depth of storage space set by the man-machine interface device, the waveform memory is controlled to store waveform data of corresponding length; the external memory is connected to the waveform processing device, and is used to store a waveform data in the waveform memory in a certain order storing; the waveform data length control unit is used to obtain the phase address of the waveform data point of the external memory, and according to the waveform data length, map the phase address to the waveform data address of the external memory; the The analog unit is used to receive the waveform data from the external memory, and perform digital-to-analog conversion processing on the received waveform data to construct a waveform output.

The waveform processing device includes: a frequency synthesis unit, which is used to send a waveform reading request to the external memory and transmit the read waveform data to the analog unit; the waveform data length control unit intercepts the frequency synthesis The unit reads the waveform request from the external memory, and judges whether the length of the waveform data requested by the read waveform exceeds the corresponding storage depth, and if so, rolls back to the initial position of the external memory to read the waveform data point; otherwise, synthesizes the frequency The phase of the unit is mapped to the waveform data address in the external memory.

The frequency synthesis unit includes: a phase accumulator, which is used to accumulate the phase address of the next waveform data point according to the phase address of the initial waveform data point of the waveform data in the external memory.

The control device is a DSP, and the storage depth control unit is integrated in the DSP. The waveform processing device is an FPGA, and the FPGA is integrated with a frequency synthesis unit and a waveform data length control unit.

The man-machine interface device is a keyboard, a touch screen, a mouse or a communication interface.

The display device is LCD or plasma display.

The waveform memory is FLASH, and the external memory is SRAM.

The beneficial effect of the present invention is that, by providing a DDS signal generator and its waveform storage depth control method, the signal generator can store all waveforms with all the storage space for the requirement of reproducing the details of the waveform amplitude, because in DDS The more points in the waveform, the more accurate the phase amplitude value can be obtained by the phase accumulator, and the phase noise can be reduced. Let the signal generator reproduce the amplitude of each sampling point finely, and reproduce the amplitude characteristics of the waveform as a whole.

For the requirement of reproducing the frequency characteristics and basic amplitude of the waveform, the signal generator needs fewer sampling points and occupies less storage space. By using the superior characteristics of DDS, the basic amplitude characteristics of the waveform can be reproduced very quickly.

Description of drawings

Fig. 1 is the structural block diagram of DDS signal generator in the prior art;

Fig. 2 is a flow chart of the method of the present invention;

Fig. 3 is the structural block diagram of embodiment 1 of the present invention;

FIG. 4 is a structural block diagram of a DDS signal generator according to Embodiment 2 of the present invention.

Detailed ways

The specific embodiments of the present invention will be described below in conjunction with the accompanying drawings.

Example 1

The present invention provides a DDS signal generator waveform storage depth control method, as shown in Figure 2, a variable length control unit is set in the common DDS signal generator, the variable length control unit is located in the common DDS signal generator Between the frequency synthesis unit and the waveform memory, used to control the access control of the frequency synthesis unit to the waveform memory.

First, the waveform depth is downloaded to the storage depth control unit through the man-machine interface. The storage control unit intercepts the read request of the frequency synthesis unit to the waveform memory. Once the waveform request is found to exceed the set storage depth, it will roll back to the waveform memory. The beginning of the read waveform point. The specific steps are (as shown in Figure 3): set the depth of the waveform storage space according to the length of the waveform data, and store the waveform data into the waveform storage space of the corresponding depth; Sequentially carry out external storage; obtain the length of the waveform data stored externally; accumulate the phase address of the next waveform data point according to the phase address of the initial waveform data point of the externally stored waveform data; according to the length of the waveform data, the The phase address is mapped to the address of the waveform data stored externally; the waveform data stored externally is processed by digital-to-analog conversion to construct the waveform output.

The acquisition of the length of the waveform data stored externally includes: judging whether the request to read the waveform data exceeds the depth of the corresponding waveform storage space, and if so, scrolling back to the initial position of the external storage to read the waveform data points. Otherwise, map the phase of the frequency synthesis unit to the waveform data address of the external memory.

Example 2

The invention provides a DDS signal generator. As shown in Figure 4, the digital signal processing (DSP) chip is used as the control device, the flash memory (FLASH) is used as the waveform memory, the field programmable gate array (FPGA) is used as the waveform processing device, and the analog unit still uses a common DDS signal generator In the digital-to-analog conversion and simulation part, the keyboard is used as the human-machine interface device and the liquid crystal display (LCD) is used as the display device; the DSP is connected with the FPGA, the keyboard and the LCD respectively, and the FPGA is connected with the analog unit.

A storage depth control unit is integrated in the DSP, which is used to control FLASH to store waveform data of corresponding length according to the storage space depth set by the keyboard;

SRAM is used as the external memory, and the SRAM is connected to the FPGA to store a waveform data in the FLASH in a certain order;

A waveform data length control unit is also integrated in the FPGA, which is used to obtain the phase address of the waveform data point of the SRAM, and maps the phase address to the waveform data address of the SRAM according to the waveform data length;

The analog unit is used to receive waveform data from the SRAM, and perform digital-to-analog conversion on the received waveform data to construct a waveform output.

A frequency synthesis unit is also integrated in the FPGA, which is used to send a read waveform request to the external memory and read waveform data to the analog unit; the waveform data length control unit intercepts the frequency synthesis unit to the external The memory reads the waveform request, and judges whether the length of the waveform data requested by the read waveform exceeds the corresponding storage depth, and if so, rolls back to the initial position of the external memory to read the waveform data point; otherwise, the phase of the frequency synthesis unit Mapped to the waveform data address of the external memory.

The frequency synthesis unit includes: a phase accumulator, which is used to accumulate the phase address of the next waveform data point according to the phase address of the initial waveform data point of the waveform data in the external memory.

A waveform data length control unit integrated in the FPGA is an important part of the DDS signal generator of the present invention, it is between the frequency synthesis unit and the waveform memory, and controls the access control of the frequency synthesis unit to the waveform memory. First, the waveform depth is downloaded to the storage depth control unit through the man-machine interface. The storage control unit intercepts the read request of the frequency synthesis unit to the waveform memory. Once the waveform request is found to exceed the set storage depth, it will roll back to the waveform memory. The beginning of the read waveform point.

A variable solution of Embodiment 2 further includes: the human-machine interface device may be a keyboard, a touch screen, a mouse, or a communication interface or a combination thereof. The display device can be a plasma display.

In the DDS signal generator of the present invention, the size of the stored waveform in the waveform storage unit can be of any length, bounded by the capacity of the waveform memory. In this way, for some waveforms with strong periodicity and simple spectral characteristics, fewer samples can be stored and the original waveform can be restored by frequency synthesis (DDS). Less waveform storage can shorten the waiting time between when the man-machine interface switches the waveform and actually outputs the complete waveform. Especially for signal generators, its digital part is often isolated from the analog part. In order to reduce the number of communication lines between the two parts, serial data is usually used to exchange data. Such a short waveform will inevitably shorten the waveform data greatly. Transmission time, improve system response speed.

Flexible pre-stored arbitrary waveforms. An important application of the signal generator is to edit and store arbitrary waveforms, but the arbitrary waveform storage space (non-waveform storage space) provided by the system is very limited, and can only store several fixed-length waveforms. However, in practical applications, the length of the arbitrary waveform provided by the user is very limited: much smaller than this fixed length; or the length of the arbitrary waveform is very long: greater than this fixed length. In these two cases, for ordinary signal generators, either the storage space is wasted, or such a large waveform cannot be stored. And this storage depth control unit can easily solve this problem, it can store more for small waveforms, and it can also store for large waveforms.

For the requirement of reproducing the details of the waveform amplitude, the signal generator can use all the storage space to store all the waveforms, because the more waveform points in DDS, the more accurate the phase amplitude value can be obtained by the phase accumulator, and the phase noise can be reduced. Let the signal generator reproduce the amplitude of each sampling point finely, and reproduce the amplitude characteristics of the waveform as a whole.

For the requirement of reproducing the frequency characteristics and basic amplitude of the waveform, the signal generator needs fewer sampling points and occupies less storage space. By using the superior characteristics of DDS, the basic amplitude characteristics of the waveform can be reproduced very quickly.

The above specific embodiments are only used to illustrate the present invention, but not to limit the present invention.

Claims (10)

1. DDS signal generator waveshape memory depth control method said method comprising the steps of:

According to Wave data length the waveform storage space degree of depth is set, and Wave data is deposited in the waveform storage space of respective depth;

A Wave data in the described waveform storage space is carried out exterior storage in certain sequence;

Obtain the Wave data length of exterior storage;

According to add up out the phase bit address of next waveform data points of the initial waveform data points phase bit address of the Wave data of exterior storage;

According to described Wave data length, with described phase place map addresses to the Wave data address of exterior storage;

Wave data structure waveform output after digital-to-analog conversion is handled with exterior storage.

2. method according to claim 1, it is characterized in that, the described Wave data length of obtaining exterior storage comprises: judge whether the waveform request of reading read Wave data has surpassed the corresponding waveform storage space degree of depth, if then rollback reads waveform data points to the reference position of exterior storage.

3. a DDS signal generator comprises: control device, wave memorizer, waveform processing device, analogue unit, human-computer interface device and display device; Described control device is connected with display device with described waveform processing device, human-computer interface device respectively, and described waveform processing device is connected with analogue unit; It is characterized in that described DDS signal generator also comprises:

The storage depth control module is connected with described control device, is used for controlling according to the storage space degree of depth of human-computer interface device setting the Wave data of described waveform memory stores respective length;

External memory storage is connected with described waveform processing device, is used for a Wave data of wave memorizer is stored in certain sequence;

Wave data length control module is used to obtain the phase bit address of the waveform data points of external memory storage, and according to described Wave data length, with described phase place map addresses to the Wave data address of external memory storage;

Described analogue unit is used to receive the Wave data that external memory storage transmits, and the Wave data that receives is carried out digital-to-analog conversion handle back structure waveform output.

4. DDS signal generator according to claim 3 is characterized in that, described waveform processing device comprises:

The frequency synthesis unit is used for sending to read the waveform request and read Wave data to described external memory storage sending described analogue unit to;

Described Wave data length control module, intercepting frequency synthesis unit is to the waveform request of reading of external memory storage, judge whether the Wave data length read the waveform request has surpassed corresponding storage depth, if then rollback reads waveform data points to the reference position of external memory storage; If otherwise with the phase mapping of frequency synthesis unit to the Wave data address of external memory storage.

5. DDS signal generator according to claim 4, it is characterized in that, described frequency synthesis unit comprises: phase accumulator is used for add up out the phase bit address of next waveform data points of initial waveform data points phase bit address according to the Wave data of external memory storage.

6. DDS signal generator according to claim 3 is characterized in that, described control device is DSP, is integrated with described storage depth control module in described DSP.

7. DDS signal generator according to claim 3 is characterized in that, described waveform processing device is FPGA, and described FPGA is integrated with frequency synthesis unit, Wave data length control module.

8. DDS signal generator according to claim 3 is characterized in that, described human-computer interface device is keyboard, touch-screen, mouse or communication interface.

9. DDS signal generator according to claim 3 is characterized in that, described display device is LCD or plasma display.

10. DDS signal generator according to claim 3 is characterized in that, described wave memorizer is FLASH, and described external memory storage is SRAM.

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