CN112415293A

CN112415293A - Amplitude-frequency characteristic measuring instrument and method based on stm32

Info

Publication number: CN112415293A
Application number: CN201910772313.1A
Authority: CN
Inventors: 谢扬琛; 原永钊; 李威远; 邱崧
Original assignee: East China Normal University
Current assignee: East China Normal University
Priority date: 2019-08-21
Filing date: 2019-08-21
Publication date: 2021-02-26

Abstract

The invention provides an amplitude-frequency characteristic measuring instrument based on stm32, which adopts a method of combining a single chip microcomputer and an analog circuit, reduces a plurality of standards in the aspect of hardware through a digital algorithm in the aspect of software, thereby ensuring the precision and simultaneously reducing the scale of the whole circuit, and finally realizing the function of measuring the amplitude-frequency characteristic of a circuit network system. The frequency sweep of this instrument can carry out the frequency sweep with the frequency of 40M at most, can realize the amplitude-frequency characteristic display of 1hz to 40 Mhz.

Description

Amplitude-frequency characteristic measuring instrument and method based on stm32

Technical Field

The invention relates to the technical field of electronic instruments, in particular to an amplitude-frequency characteristic measuring instrument and a measuring method.

Background

The amplitude-frequency characteristic measuring instrument is an instrument for testing the amplitude-frequency characteristic of a circuit, and is required by electronic family members for experiments and network characteristic analysis in scientific research projects. However, some common measuring instruments of large manufacturers such as agilent and common sources in the market are generally heavy and inconvenient to carry, and bring much inconvenience to electronic engineers and students of electronic systems. On the other hand, the amplitude-frequency characteristic measuring instrument with the display function on the market is expensive. Therefore, a portable amplitude-frequency characteristic measuring instrument with a display function is designed.

Disclosure of Invention

The invention discloses a portable amplitude-frequency characteristic measuring instrument based on stm32, which is designed for solving some defects of the amplitude-frequency characteristic measuring instrument in the existing market. The invention adopts the method of combining the singlechip and the analog circuit, reduces the standards in the aspect of hardware through the digital algorithm in the aspect of software, thereby ensuring the precision and simultaneously reducing the scale of the whole circuit, and finally realizing the function of measuring the amplitude-frequency characteristic of the circuit network system. The frequency sweep of this instrument can carry out the frequency sweep with the frequency of 40M at most, can realize the amplitude-frequency characteristic display of 1hz to 40 Mhz.

The invention mainly comprises the following parts:

first, DDS

The DDS adopts a chip AD9910 of a 1G SPS, 14-bit and 3.3V CMOS direct digital frequency synthesizer of ADI company. The AD9910 has built-in 1G SPS, 14-bit DAC (digital to analog converter), and the frequency resolution can reach 0.23hz through 1GSPS internal clock speed (up to 400M analog output). In addition, it has excellent dynamic performance (greater than 80db narrow-band SFDR) and extremely low phase noise (1khz offset, less than-125 dBc/Hz at 400M carrier). The DDS in the system mainly has the functions of outputting a sine signal generator with constant amplitude and frequency from 1Hz to 40MHz, and outputting a direct current signal to a singlechip part from a DAC (for example, 0.82V corresponds to 1M) at the current output frequency through code table mapping. Second, the signal conditioning module

The signal conditioning module includes: emitter follower, attenuator, and effective value detecting section. The network under test of the entire system is connected between the emitter follower and the effective value detection section. The first part of the signal conditioning module is an emitter follower which is used for isolating the DDS from the rear stage and preventing the influence of series and parallel connection between the two stages. The attenuator is composed of n-type resistor network and is used for attenuating the signal output by the DDS, so that the DDS output signal is attenuated to the input range accepted by the tested network. The effective value detection part uses an AD8362 chip to convert an output end signal of a detected network from an alternating current sinusoidal signal into a direct current signal so as to be convenient for the acquisition of a later-stage ADC. Third, the single chip part

The single chip microcomputer part consists of stm32h7 series single chip microcomputers stm32h 743. The H7 series has main frequency as high as 480M, can conveniently apply various digital algorithms, and has very advantage in single chip of the same main frequency. In the system, the singlechip acquires a direct current signal output by the effective value chip through adc, and divides the direct current signal by a known output signal (a DDS output signal is a known signal) to obtain an amplification factor. And the single chip microcomputer can also read direct current transmitted from the DDS part in real time through another AD to acquire current frequency information, so that the current amplitude-frequency characteristic is obtained.

The implementation method comprises the following steps: the sine alternating current signal is output by the DDS, and the signal is output to the emitter follower, so that the front and rear two-stage signals of the emitter follower are isolated and do not influence each other. The signal output by the emitter follower enters an attenuator, so that the DDS output signal is attenuated to be within an input range accepted by the tested network. The back of the attenuator enters a tested network, and a signal output by the tested network is accessed to the effective value chip to acquire the amplitude information of the output signal. In addition, the frequency information output by the DDS at the moment is directly input to the singlechip by a DAC through code table mapping (for example, 0.82V corresponds to 1M).

The invention has the beneficial effects that: the invention provides an amplitude-frequency characteristic measuring instrument based on stm32, which utilizes the programmable characteristic of an stm32 series single chip microcomputer to realize some hardware circuits through a software algorithm, reduces the scale of the whole circuit and reduces the expected volume of the amplitude-frequency characteristic measuring instrument. And the monolithic processor of stm32h7 series makes the whole power consumption of circuit reduce, has prolonged the live time of instrument.

Drawings

FIG. 1 is a block diagram of the system of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following specific examples and the accompanying drawings. The procedures, conditions, experimental methods and the like for carrying out the present invention are general knowledge and common general knowledge in the art except for the contents specifically mentioned below, and the present invention is not particularly limited.

As shown in fig. 1, the stm 32-based amplitude-frequency characteristic measuring instrument mainly includes the following parts:

first, DDS

The DDS adopts a chip AD9910 of a 1G SPS, 14-bit and 3.3V CMOS direct digital frequency synthesizer of ADI company. The AD9910 has built-in 1G SPS, 14-bit DAC (digital to analog converter), and the frequency resolution can reach 0.23hz through 1GSPS internal clock speed (up to 400M analog output). In addition, it has excellent dynamic performance (greater than 80db narrow-band SFDR) and extremely low phase noise (1khz offset, less than-125 dBc/Hz at 400M carrier). The DDS in the system mainly has the functions of outputting a sine signal generator with constant amplitude and frequency from 1Hz to 40MHz, and outputting a direct current signal to a singlechip part from a DAC (for example, 0.82V corresponds to 1M) at the current output frequency through code table mapping.

Second, the signal conditioning module

The signal conditioning module includes: emitter follower, attenuator, and effective value detecting section. The network under test of the entire system is connected between the emitter follower and the effective value detection section. The first part of the signal conditioning module is an emitter follower which is used for isolating the DDS from the rear stage and preventing the influence of series and parallel connection between the two stages. The attenuator is composed of n-type resistor network and is used for attenuating the signal output by the DDS, so that the DDS output signal is attenuated to the input range accepted by the tested network. The effective value detection part uses an AD8362 chip to convert an output end signal of a detected network from an alternating current sinusoidal signal into a direct current signal so as to be convenient for the acquisition of a later-stage ADC.

Third, the single chip part

The protection of the present invention is not limited to the above embodiments. Variations and advantages that may occur to those skilled in the art may be incorporated into the invention without departing from the spirit and scope of the inventive concept, and the scope of the appended claims is intended to be protected.

Claims

1. An amplitude-frequency characteristic measuring instrument based on stm32, comprising:

first, DDS:

the DDS is a sine signal generator which outputs sine signals with constant amplitude and stepped frequency from 1Hz to 40MHz, and the current output frequency is mapped by a DAC through a code table to output direct current signals to the singlechip part;

secondly, the signal conditioning module:

the signal conditioning module includes: emitter follower, attenuator, effective value detecting section; the tested network of the whole system is connected between the emitter follower and the effective value detection part; the first part of the signal conditioning module is an emitter follower which is used for isolating the DDS from the rear stage and preventing the influence of series and parallel connection between the two stages; the attenuator is composed of an n-shaped resistor network and is used for attenuating the signal output by the DDS so that the signal output by the DDS is attenuated to the input range accepted by the tested network; the effective value detection part uses an AD8362 chip to convert an output end signal of a detected network from an alternating current sinusoidal signal into a direct current signal so as to facilitate the acquisition of a post-stage ADC;

thirdly, the singlechip part:

the single chip microcomputer collects the direct current signal output by the effective value chip through adc and divides the direct current signal with the known output signal to obtain the amplification factor; and the single chip microcomputer can also read direct current transmitted from the DDS part in real time through another AD to acquire current frequency information, so that the current amplitude-frequency characteristic is obtained.

2. The stm 32-based amplitude-frequency characteristic measuring instrument as claimed in claim 1, wherein the DDS adopts a chip AD9910 of a 1G SPS, 14-bit, 3.3V CMOS direct digital frequency synthesizer of ADI company.

3. The stm 32-based amplitude-frequency characteristic measuring instrument as claimed in claim 2, wherein the AD9910 is internally provided with 1G SPS, 14-bit DAC, and the frequency resolution reaches 0.23hz through 1GSPS internal clock speed.

4. The stm 32-based amplitude-frequency characteristic measuring instrument as claimed in claim 1, wherein the single chip microcomputer part is composed of a stm32h7 series single chip microcomputer stm32h 743; the H7 series has main frequency up to 480M, and various digital algorithms can be conveniently applied.

5. An stm 32-based amplitude-frequency characteristic measuring method, which is characterized in that the stm 32-based amplitude-frequency characteristic measuring instrument as claimed in any one of claims 1-4 is adopted, and the method comprises the following steps: sinusoidal alternating current signals are output by the DDS, and the signals are output to the emitter follower, so that front and rear two-stage signals of the emitter follower are isolated and do not influence each other; the signal output by the emitter follower enters an attenuator to enable the DDS output signal to be attenuated within an input range accepted by a network to be tested; the back of the attenuator enters a tested network, and a signal output by the tested network is accessed to the effective value chip to acquire the amplitude information of the output signal.

6. The stm 32-based amplitude-frequency characteristic measurement method as claimed in claim 5, wherein frequency information output by the DDS is directly input to the single chip microcomputer by a DAC through code table mapping.