CN210639206U - 100M high-precision portable signal generator based on DDS - Google Patents

Abstract

The utility model discloses a 100M high accuracy portable signal generator based on DDS, including control module, the last electric connection of control module has the display module, the last electric connection of control module has power module, the last electric connection of control module has the DDS module, the DDS module electric connection has the high order filter, the high order filter electric connection has the program control to amplify, the program control amplifies the electric connection and has the broadband to amplify, the broadband amplifies the electric connection and has the plastic transform output; the utility model has the advantages of high output frequency coverage bandwidth, low step value and high precision frequency output; the high-frequency-range high-power-consumption high-frequency-range; the multi-channel waveform generator has at least three selectable waveforms and a multi-channel output function; the signal output stability and the overall anti-interference characteristic of the system, and the portable and simple operation are reasonable.

Description

100M high-precision portable signal generator based on DDS

Technical Field

The utility model relates to an instrument and meter technical field specifically is a portable signal generator of 100M high accuracy based on DDS.

Background

The signal generator has wide application in scientific research field and production practice, and the random waveform generator (AWG) has very common and wide application in the application field of analog signals or analog-digital mixed signals. Such as generating an excitation signal to simulate the reproduction of a certain sensor, e.g. a car crash test, or generating a high speed analog signal to test the function of a certain chip. From simple sine wave generation to a less complex AM/FM modulated signal to more complex QAM modulated signals, etc., there are applications for arbitrary waveform generators. Typically a function signal generator, providing a specific function signal waveform, such as a sinusoidal signal, a triangular wave, a programmable arbitrary waveform, and the like. Or a conventional high frequency signal generator to generate a high frequency, high dBm sinusoidal signal up to GHz. Common signal generators have multiple uses in the field of communication systems, for example, sinusoidal signals are mainly used for measuring frequency characteristics, nonlinear distortion, gain, system response sensitivity and the like of circuits and systems; the high-frequency signal generator generates a very high-frequency signal with the frequency of 30-300 MHz, and the signal is used for measuring technical indexes of various receivers; the high-bandwidth signal is used for testing the bandwidth and the noise characteristic of the signal processing system, processing the signal and carrying out signal integrity analysis; the rectangular pulse signal can be used to test the transient response of a linear system. Analog signals may also be used to test the performance of radar, multi-channel communications, and other pulse digital systems.

Common signal generators are function signal generators and high-frequency signal generators, namely, a DDS type (direct digital frequency synthesizer) and an analog modulation type (a series of analog circuits such as an oscillator). In the existing scheme, an FPGA is mostly adopted, a DDS kernel is written in the FPGA to serve as a signal generator part of a core, and then a rear-stage multi-stage follower circuit is adopted and a series of processing is carried out on an output signal according to a feedback signal; however, in the prior art, a post-stage circuit is too complex, and a series of feedback links and post-stage signal processing circuits are added to match with basic signals output by the FPGA, so that the design difficulty is greatly increased, and the volume and the quality of equipment are increased. Due to strict requirements on a power supply, equipment cannot be powered by low input voltage, and portability is caused; some chips need ultra-high voltage power supply, and some chips even reach 40V, so that the circuit design is over-sophisticated in power supply; the complexity of the circuitry also contributes to the inconvenience and portability of the device.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a 100M high-precision portable signal generator based on DDS, which has high output frequency coverage bandwidth, low step value and high precision frequency output; the high-frequency-range high-power-consumption high-frequency-range; the multi-channel waveform generator has at least three selectable waveforms and a multi-channel output function; the signal output stability and the overall anti-interference characteristic of the system as well as reasonable portability, simplicity and convenience in operation and the like are used for solving the problems in the background technology.

In order to achieve the above object, the utility model provides a following technical scheme: the utility model provides a portable signal generator of 100M high accuracy based on DDS, includes control module, the last electric connection of control module has display module, the last electric connection of control module has power module, the last electric connection of control module has the DDS module, DDS module electric connection has the high order filter, high order filter electric connection has programme-controlled amplification, programme-controlled amplification electric connection has the broadband to enlarge, broadband amplification electric connection has the plastic transform output.

Preferably, the control module adopts 32-bit MCUSTM32F407/F103 to drive the DDS module, the DDS module comprises writing of basic driving codes of amplitude modulation, frequency modulation, phase shift, multi-order modulation of a reference signal, gating channel output and the like, and the DDS module is electrically connected with an active crystal oscillator and a plurality of groups of capacitance resistors.

Preferably, the DDS module is electrically connected to a front-end rf transformer, the rf transformer employs an ADTT1-1 chip, one end of the rf transformer is electrically connected to a high-order elliptic filter, the high-order elliptic filter is configured as a seven-order elliptic filter, and the high-order elliptic filter is electrically connected to a post-stage signal processing circuit.

Preferably, the post-stage signal processing circuit comprises a hysteresis comparator, the hysteresis comparator is electrically connected with a TLV3502 high-speed rail-to-rail comparator, the hysteresis comparator is electrically connected with a positive feedback circuit, the hysteresis comparator is electrically connected with a secondary amplitude modulation circuit, the secondary amplitude modulation circuit is electrically connected with a digital step attenuator HMC624, the post-stage signal processing circuit comprises a triangular wave generator driving circuit, and the triangular wave generator driving circuit adopts an AD9833DDS chip of an ADI semiconductor.

Preferably, the power module adopts a single transformer to reduce the voltage, the single transformer is electrically connected with a linear LDO, and the power module is electrically connected with a lithium battery pack.

Preferably, the lithium battery pack adopts a max8903 lithium battery charging and discharging intelligent management chip as a control chip of the charging circuit, the max8903 lithium battery charging and discharging intelligent management chip is electrically connected with a booster circuit, the booster circuit is electrically connected with a booster chip TPS61230, a voltage stabilizing circuit is electrically connected behind the booster circuit, and the voltage stabilizing circuit adopts an AMS1117 voltage stabilizing chip.

Compared with the prior art, the beneficial effects of the utility model are that:

1. portable design: the prior technical scheme mostly adopts a voltage reduction scheme such as a multi-transformer and the like to ensure the power supply to be stable, and the invention adopts a single transformer and a multistage LDO linear voltage stabilizer voltage reduction circuit, so that the power is properly reduced under the condition of not losing the normal working state to obtain the volume and the weight of portability.

2. A rational and lower cost core signal source scheme: the DDS (direct digital frequency synthesizer) chip has been widely applied in various fields and products, the performance is not inferior to that of the conventional FPGA as a basic signal source, and the maintenance cost (comprehensive development cost and device cost) required by the direct digital frequency synthesizer is much lower than that of the FPGA, because the FPGA needs to use a hardware description language as a working basis, and the DDS device is a device with a fixed internal circuit.

3. More compact post-processing circuitry: due to the scheme of taking the FPGA as a core signal source, a series of complex feedback processing circuits are needed to ensure that the waveforms of the required corresponding frequency, amplitude and phase can be normally output, such feedback links can be effectively reduced by adopting the DDS device, and a series of processing can be directly carried out on the signals.

4. The method gets rid of the constraint of the power supply mode of the traditional instrument: the AC voltage reduction power supply system has the main core content that a series of voltage reduction and increase and lithium battery charge and discharge circuits are arranged, and has the function and the purpose of impacting the traditional AC voltage reduction power supply mode of various instruments. Although the traditional power supply mode can effectively ensure the stable work of the system and the accuracy of the instrument, people obviously and more hope that more things can be put into pockets and backpacks under the high-speed life rhythm and working state, so as to achieve the more efficient and relaxed working state; and in order to meet the demands of various environments, the conventional power supply mode should be attempted to be broken. Compared with the traditional power supply mode, the mobile power supply system adopts a novel power supply design idea of mutual coordination among integrated ICs, simulates various application scenes through a series of limiting circuits and power supply management modes, and designs and manufactures a mobile power supply scheme which is as efficient and reasonable as possible. Even if the energy storage of the movable energy block limits, only short power supply time can be provided for a large-power-consumption instrument, and the method is a small step of forward innovation.

Drawings

FIG. 1 is a basic hardware block diagram of the present invention;

fig. 2 is a DDS device driving circuit of the present invention;

fig. 3 is a high order elliptic filter according to the present invention;

fig. 4 is a hysteresis comparator circuit of the present invention;

fig. 5 is a driving circuit of an AD9833 triangular wave generator of the present invention;

fig. 6 is a lithium battery booster circuit of the present invention;

fig. 7 is the utility model discloses a lithium battery charging and discharging and power management circuit.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

The same reference numbers in different drawings identify the same or similar elements; it should be further understood that terms such as "first," "second," "third," "upper," "lower," "front," "rear," "inner," "outer," "end," "portion," "section," "width," "thickness," "zone," and the like, may be used solely for convenience in reference to the figures and to aid in describing the invention, and are not intended to limit the invention.

Referring to fig. 1-7, the present invention provides a technical solution: a DDS-based 100M high-precision portable signal generator comprises a control module, wherein the control module is electrically connected with a display module, and the display module adopts an LCD (liquid crystal display) and can display the waveform of the signal generator; the control module is electrically connected with a power supply module, and the power supply module realizes power supply and lithium battery charging; the control module is electrically connected with a DDS module which is used as a core signal source for generating signals; the DDS module is electrically connected with a high-order filter, the high-order filter is electrically connected with a program-controlled amplifier, and the program-controlled amplifier is used as a first amplifier for amplifying a signal to about 1 VPP; the program-controlled amplifier is electrically connected with a broadband amplifier, the broadband amplifier is used as a second-stage amplifier, and the gain is fixed gain; the broadband amplification is electrically connected with the shaping conversion output.

Specifically, the control module adopts 32-bit MCUSTM32F407/F103 to drive the DDS module, the DDS module comprises writing of basic driving codes of amplitude modulation, frequency modulation, phase shifting, multi-order modulation, gating channel output and the like of a reference signal, the DDS module is electrically connected with an active crystal oscillator and a plurality of groups of capacitance resistors, the active crystal oscillator and the various capacitance resistors at a position can effectively bring noise and various clutter, and the MCUSTM32F407/F103 can control the DDS module to generate signal waves.

Specifically, the DDS module is electrically connected to a front-end rf transformer, the rf transformer employs an ADTT1-1 chip, one end of the rf transformer is electrically connected to a high-order elliptic filter, the high-order elliptic filter is set as a seven-order elliptic filter, the high-order elliptic filter is electrically connected to a post-stage signal processing circuit, the rf transformer converts an output current signal into a voltage signal, and the voltage signal is pre-processed by the high-order elliptic filter and then delivered to the post-stage signal processing circuit.

Specifically, the post-stage signal processing circuit comprises a hysteresis comparator, the hysteresis comparator is electrically connected with a TLV3502 high-speed rail-to-rail comparator, the hysteresis comparator is electrically connected with a positive feedback circuit, the hysteresis comparator is electrically connected with a secondary amplitude modulation circuit, the secondary amplitude modulation circuit is electrically connected with a digital step attenuator HMC624, the post-stage signal processing circuit comprises a triangular wave generator driving circuit, the triangular wave generator driving circuit adopts an AD9833DDS chip of an ADI semiconductor, the hysteresis comparator at the position is added with positive feedback to accelerate the response speed of the comparator, the positive feedback added by the hysteresis comparator is very strong, and the parasitic coupling in a far-comparison circuit is much stronger, so the hysteresis comparator can also avoid self-excited oscillation generated by the circuit parasitic coupling.

Specifically, power module adopts single transformer to decompress, the last electric connection of single transformer has linear LDO, power module electric connection has lithium cell group, and this department adopts single transformer decompression, truns into 200 ~ 240VAC power into 18VDC power, under the circumstances of guaranteeing that the instrument normally works, power can be up to more than 20W.

Specifically, the lithium battery pack adopts a max8903 lithium battery charging and discharging intelligent management chip as a control chip of a charging circuit, the max8903 lithium battery charging and discharging intelligent management chip is electrically connected with a booster circuit, the booster circuit is electrically connected with a booster chip TPS61230, a voltage stabilizing circuit is electrically connected behind the booster circuit, the voltage stabilizing circuit adopts an AMS1117 voltage stabilizing chip, and the booster circuit is mainly used for meeting the basic requirement that voltage is reduced after 5V is required when a 3.7V lithium battery is equipped as a power supply to supply power to a system.

The working process is as follows:

1. the DDS device is driven by adopting 32-bit MCUSTM32F 407/F103: the driving device comprises the writing of basic driving codes such as amplitude modulation, frequency modulation, phase shifting, multi-order modulation of reference signals, gating channel output and the like, and a basic hardware driving circuit is shown in figure 2.

2. After the DDS device is driven, each channel obtains two current signal outputs, the output current signals are converted into voltage signals through a front radio frequency transformer, the voltage signals are preprocessed through a seven-order elliptic filter and then delivered to a post-stage signal processing circuit, and a circuit schematic diagram of the part is shown in fig. 3.

3. The invention aims to generate three basic signals, namely sine wave, square wave and triangular wave, and is discussed below according to each single waveform, and the design idea of the sine wave is discussed first.

Sine wave: according to the requirements, besides the frequency of 100M and above the bandwidth which is only provided by the high-end function signal generator, the sine wave also needs to have certain output amplitude and radio frequency power (dBm), and the direct output of the signal generated by the DDS device is influenced by the amplitude-frequency characteristic of the device, so that the requirement cannot be met, therefore, a series of post-stage processing circuits are arranged to output the high-frequency sine wave after the high-frequency sine wave is subjected to stage processing, and the main stage processing comprises the following points:

(1) after passing through the elliptic filter, the first stage of amplification is carried out: program-controlled amplification, which amplifies the signal to about 1 VPP;

(2) setting a second-stage gain through a current feedback type or voltage feedback type broadband amplifier, wherein the gain is a fixed gain and is set to be about 10-20 dB;

(3) the final stage sets fixed or voltage-variable adjustable gain through a high-frequency radio-frequency power amplifier, the gain is set to be 1-5 times, and the high-frequency output signal can be pushed to meet the power requirement of the equipment under the condition of highly reducing the signal;

(4) therefore, the conditioning of the sine wave is basically finished, the final output circuit can be provided with the high-order passive filter again according to the actual situation, the problems of signal delay, reflection, oscillation and the like caused by the passive system are noticed, and the final output circuit is selected according to the actual situation.

4. The second type of demand waveform is a square wave, and several existing generation forms of square waves can be known first, such as a DAC directly outputting a square wave, or a hysteresis comparator, a single threshold comparator, a double threshold comparator, and the like:

(1) referring to the hysteresis comparator circuit, it is also the main circuit of the present invention to generate square wave, as shown in fig. 4. The hysteresis comparator with positive feedback can increase the response speed of the comparator, which is an advantage. In addition, the hysteresis comparator can avoid self-oscillation caused by circuit parasitic coupling because the positive feedback added by the hysteresis comparator is strong and much stronger than the parasitic coupling in the circuit. The use of TLV3502 high speed rail-to-rail comparator by TI (texas instruments semiconductor) to construct a hysteretic comparator circuit to generate a square wave is clearly the second choice for the square wave signal.

(2) After the square wave signal is generated, the square wave signal can be easily obtained, and the waveform is the square wave signal with the amplitude fixed at 5VPP because the signal is output by the comparator, and the requirement of amplitude modulation can not be met if the square wave signal is directly output. Therefore, a secondary amplitude modulation circuit is needed, and a digital step attenuator HMC624 is adopted for attenuation and amplitude modulation to perfect square wave output.

5. The third waveform is a triangle wave:

there are two common methods of generating the triangle wave, namely direct DDS output (DAC type) and integrator output. After the comparison scheme, it is not difficult to obtain, the integrator integrates the sine wave, and after tens k to hundreds kHZ, the system response delay is serious, and the waveform is output without reaching the required integration effect, so that the output waveform is still a sine wave or a distorted waveform, and a better triangular wave output cannot be brought to the project, which is also the reason that most common function signal generators on the market limit the triangular wave output frequency bandwidth to 0-500 kHZ or even lower. Therefore, in order to ensure that the highest possible triangular waveform output can be achieved, the present project uses AD9833DDS (direct digital frequency synthesizer) chips of ADI semiconductor as a single triangular output channel to provide a stable, high frequency triangular output (up to 2M), as shown in fig. 5.

6. Another core technology of the project is how to design and verify the power supply scheme of the portable instrument, and the following is a description of the power supply scheme.

The voltage reduction circuit: the basic instrument is provided with a typical voltage reduction and stabilization circuit for converting 200V-240 VAC alternating voltage into a low-voltage direct-current power supply, and in combination with the portable weight and size, the single-transformer voltage reduction device is adopted to reduce the voltage and convert the 200-240 VAC power supply into an 18VDC power supply, so that the power can be up to more than 20W under the condition of ensuring the normal work of the instrument. The 18V voltage is used as a basic voltage, and a stable voltage is provided for different devices through a linear LDO (5V, 3.3V, 2.5V and 1.8V) which steps down and drives more power circuits with typical voltage values.

7. A booster circuit: the booster circuit is mainly used for meeting the basic requirement that when a 3.7V lithium battery is used as a power supply to supply power to a system, the voltage is reduced after 5V is achieved. A fundamental problem often faced by boost circuits is insufficient power. The present invention employs a booster chip TPS61230 of TI (texas instruments semiconductor) outputting up to 5V4A, which can meet the basic requirements of the present invention after the pressure test. The reference circuit is shown in fig. 6.

8. Lithium battery charge-discharge circuit: the lithium battery charging and discharging circuit is used for supplying power to the lithium battery when the lithium battery is switched to supply power, the lithium battery is insufficient in electric quantity and needs to supply power to a system while charging, or the lithium battery is charged simultaneously under the condition of switching to external power supply, and the lithium battery charging and discharging circuit is actually under the same condition, namely, the lithium battery charging and the system can be charged simultaneously and supplied power to the system simultaneously. The invention adopts a max8903 lithium battery charging and discharging intelligent management chip of a MAXIM semiconductor focusing on power supply management as a core component of a charging circuit, combines a post-stage boosting circuit, and refers to a circuit diagram shown in FIG. 7 to provide a complete design idea for boosting the lithium battery and the charging circuit, so that the power supply management requirements under various conditions can be met.

9. The output setting of signals, including amplitude setting, frequency setting, phase place setting, all by MCU STM32F1/F4 collocation dabs the button, the touch display screen accomplishes.

10. The shell with certain strength and interference resistance is completed by matching SolidWorks3D modeling and 3D printing technology.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (6)

1. A100M high accuracy portable signal generator based on DDS, includes the control module, its characterized in that: the system comprises a control module, a display module, a power module, a DDS module, a high-order filter, a program-controlled amplifier, a broadband amplifier and a shaping transformation output, wherein the control module is electrically connected with the display module, the control module is electrically connected with the power module, the DDS module is electrically connected with the high-order filter, the high-order filter is electrically connected with the program-controlled amplifier, the program-controlled amplifier is electrically connected with the broadband amplifier, and the broadband amplifier is.

2. A DDS based 100M high precision portable signal generator as claimed in claim 1 wherein: the control module adopts 32-bit MCUSTM32F407/F103 to drive the DDS module, the DDS module comprises writing of basic driving codes of amplitude modulation, frequency modulation, phase shifting, multi-order modulation of reference signals, gating channel output and the like, and the DDS module is electrically connected with an active crystal oscillator and a plurality of groups of capacitive resistors.

3. A DDS based 100M high precision portable signal generator as claimed in claim 2 wherein: the DDS module is electrically connected with a preposed radio frequency transformer, the radio frequency transformer adopts an ADTT1-1 chip, one end of the radio frequency transformer is electrically connected with a high-order elliptic filter, the high-order elliptic filter is set to be a seven-order elliptic filter, and the high-order elliptic filter is electrically connected with a post-stage signal processing circuit.

4. A DDS based 100M high precision portable signal generator as claimed in claim 3 wherein: the post-stage signal processing circuit comprises a hysteresis comparator, the hysteresis comparator is electrically connected with a TLV3502 high-speed rail-to-rail comparator, the hysteresis comparator is electrically connected with a positive feedback circuit, the hysteresis comparator is electrically connected with a secondary amplitude modulation circuit, the secondary amplitude modulation circuit is electrically connected with a digital step attenuator HMC624, the post-stage signal processing circuit comprises a triangular wave generator driving circuit, and an AD9833DDS chip of an ADI semiconductor is adopted in the triangular wave generator driving circuit.

5. A DDS based 100M high precision portable signal generator as claimed in claim 1 wherein: the power module adopts single transformer to reduce pressure, the last electric connection of single transformer has linear LDO, power module electric connection has lithium cell group.

6. A DDS based 100M high precision portable signal generator as claimed in claim 5 wherein: the intelligent charging and discharging management circuit is characterized in that a max8903 lithium battery charging and discharging intelligent management chip is used as a control chip of the charging circuit, the max8903 lithium battery charging and discharging intelligent management chip is electrically connected with a booster circuit, the booster circuit is electrically connected with a booster chip TPS61230, a voltage stabilizing circuit is electrically connected behind the booster circuit, and the voltage stabilizing circuit adopts an AMS1117 voltage stabilizing chip.

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