CN117792523A

CN117792523A - S parameter measurement system and method based on GNU Radio

Info

Publication number: CN117792523A
Application number: CN202311808458.5A
Authority: CN
Inventors: 牛玉广; 姚启航; 盖新华; 叶伟斌; 吴泽宇
Original assignee: North China Electric Power University
Current assignee: North China Electric Power University
Priority date: 2023-12-26
Filing date: 2023-12-26
Publication date: 2024-03-29

Abstract

The invention discloses an S parameter measurement system and method based on GNU Radio, and relates to the field of Radio frequency S parameter test, wherein the system comprises: the system comprises a board card, a hardware circuit and a GNU Radio module; the transmitting port of the board card is connected with the input end of the hardware circuit; the first output end of the hardware circuit is connected with a first receiving port of the board card; the second output end of the hardware circuit is connected with a second receiving port of the board card; the first receiving port and the second receiving port of the board card are connected with the GNU Radio module; the hardware circuit is connected with the device to be tested; the board card sends a sweep frequency signal to the hardware circuit, and the hardware circuit outputs a reference signal and a target signal according to the sweep frequency signal; the GNU Radio module is used for carrying out frequency domain change on the reference signal and the target signal respectively, and calculating S parameters according to the signals after the frequency domain change. The invention has low cost and small volume.

Description

S parameter measurement system and method based on GNU Radio

Technical Field

The invention relates to the field of Radio frequency S parameter testing, in particular to an S parameter measuring system and method based on GNU Radio.

Background

With the continuous development of RF microwave technology, the requirement for measuring microwave signals by using S parameters is also increasing. The radio frequency S parameter refers to a parameter used to describe signal transmission characteristics in a radio frequency circuit. It includes two parameters: s11 and S21. S11 refers to the reflection coefficient, which describes the extent to which a signal is reflected back after entering the circuit from port 1; s21 refers to a transmission coefficient describing the extent to which a signal is transmitted from port 1 to port 2 after entering the circuit. These two parameters are very important parameters in radio frequency circuit design and testing.

The network analyzer is an important device for measuring the S parameter, and the network analyzer with excellent performance is not only expensive, but also not easy to carry due to the heavier body. To meet the needs of low cost, portability and simplicity of measurement tools under specific needs, research work on single port portable RF signal S parameter measurement systems has been conducted. With the continuous development of RF microwave technology, the demand for RF devices used in various applications is increasing. The microwave detection technology plays a very key role in the development process, is a very key part in the technical field of microwave science, and is also in a very key position in the field of electromagnetic fields. The radio frequency devices are manufactured without the aid of microwave detection techniques. Any complex RF element can be replaced by a parametric network and can be characterized by two selected variables and their interrelationships for the network port reference plane. Therefore, in the current radio frequency microwave field, the most widely applied is the S parameter which is convenient to measure, and the S parameter can show the performance of any radio frequency element as the most basic parameter in a microwave network. Common components such as splitters, filters, amplifiers, tuning tables, attenuators, antennas, etc. all take into account the S-parameters. In the combination of continuous development of microwave technology, S parameters become important reference bases in auxiliary design elements of electromagnetic simulation software. Therefore, measuring the RF signal S parameter is an important direction of research in the microwave field.

At present, the measurement technology of the S parameter is mature day by day, and the accuracy of the S parameter measurement system is more perfect. In the laboratory, rf researchers prepare an S-parameter measurement system, such as a vector network analyzer, for component measurement. And today, where microwave technology has evolved greatly, microwaves have been continuously extended in other fields, and S-parameter measurement systems have not been limited to measurement verification of a single device only, but have been applied in combination with other instruments in different kinds of scenarios. At present, the main research direction of S parameter measurement at home and abroad in China is to improve the S parameter measurement precision and reduce the S parameter measurement error. Today, network analyzers have become an important tool for RF and microwave engineers to measure the S parameters of RF signals, widely used in the field of RF microwave device measurement. There are many companies producing network analyzers worldwide, and the network analyzers produced by these companies can not only measure the parameters of passive devices, but also characterize the characteristics of active devices, so that the accuracy of measuring the S parameters can be greatly ensured, and the measurement error can be reduced.

The network analyzer is also divided into a vector network analyzer and a scalar network analyzer, wherein the vector network analyzer can measure different performances such as amplitude frequency, phase frequency, port impedance and the like of a device or a network to be measured in real time, and can also perform Fourier inverse transformation through an internal processor to perform time domain analysis on the device or the network to be measured. However, because of the strong and high accuracy of the network analyzer, the network analyzer produced by most companies at present is expensive, has a large body volume and a large weight, is only suitable for indoor environments such as university laboratories, for example, experimental teaching scenes, and has a heavy burden on common users when designing and developing radio frequency elements.

Disclosure of Invention

Based on the above, the embodiment of the invention provides an S parameter measurement system and method based on GNU Radio, so as to reduce cost, reduce body volume and facilitate design and development of Radio frequency elements.

In order to achieve the above object, the embodiment of the present invention provides the following solutions:

an S-parameter measurement system based on GNU Radio, comprising: the system comprises a board card, a hardware circuit and a GNU Radio module;

the transmitting port of the board card is connected with the input end of the hardware circuit; the first output end of the hardware circuit is connected with a first receiving port of the board card; the second output end of the hardware circuit is connected with the second receiving port of the board card; the first receiving port and the second receiving port of the board card are connected with the GNU Radio module; the hardware circuit is connected with the device to be tested;

the board card is used for sending a sweep frequency signal to the hardware circuit;

the hardware circuit is used for outputting a reference signal and a target signal according to the sweep frequency signal;

the reference signal is obtained by mixing a signal with a first set proportion power with a local oscillation signal after amplifying the sweep frequency signal and distributing power; the target signal is a first detected signal or a second detected signal; the first measured signal is obtained by amplifying the sweep frequency signal and distributing power, enabling a signal with a second set proportion power to enter a measured device, and mixing a reflected signal of the measured device with a local oscillation signal; the second measured signal is obtained by amplifying the sweep frequency signal and distributing power, enabling a signal with a second set proportion power to enter a measured device, and mixing an output signal transmitted by the measured device with a local oscillation signal;

The GNU Radio module is used for carrying out frequency domain change on the reference signal and the target signal respectively and calculating an S parameter according to the signals after the frequency domain change; if the target signal is the first detected signal, the S parameter is an S11 parameter; and if the target signal is the second detected signal, the S parameter is an S21 parameter.

Optionally, the GNU Radio module includes: the device comprises a signal receiving module, a first frequency domain transformation module, a second frequency domain transformation module, a data dividing module, an amplitude conversion module and a self-defining module;

the signal receiving module is used for sending the reference signal to the first frequency domain transforming module and sending the target signal to the second frequency domain transforming module;

the first frequency domain transformation module is used for performing fast Fourier transformation on the reference signal to obtain a first transformation signal;

the second frequency domain transformation module is used for performing fast Fourier transformation on the target signal to obtain a second transformation signal;

the data dividing module is used for dividing the first transformation signal by the second transformation signal to obtain a preliminary S parameter;

the amplitude conversion module is used for converting the first conversion signal into an amplitude value to obtain a signal with the amplitude value converted;

The self-defining module is used for carrying out maximum value positioning on the signals after amplitude conversion to obtain signal maximum values, and calibrating the preliminary S parameters according to the set error coefficients to obtain final S parameters; the signal maxima are used to characterize the energy of the swept frequency signal.

Optionally, the hardware circuit includes: the signal processing circuit, the first directional coupler, the second directional coupler, the first mixer, the second mixer, the third mixer and the switch;

the transmitting port of the board card, the signal processing circuit, the directional coupler, the second directional coupler and the device to be tested are sequentially connected; the coupling end of the first directional coupler is connected with a first receiving port of the board card through the first mixer; the output end of the second directional coupler is connected with the input end of the tested device; the coupling end of the second directional coupler is connected with the first wiring end of the switch through the second mixer; the output end of the tested device is connected with the second wiring terminal of the switch through the third mixer; a third wiring terminal of the switch is connected with a second receiving port of the board card;

The signal processing circuit is used for amplifying the sweep frequency signal to obtain a sweep frequency amplified signal;

the first directional coupler is used for distributing the power of the sweep frequency amplified signal, so that the coupling end of the first directional coupler outputs a signal with a first set proportion power;

the first mixer is used for performing down-conversion processing on a signal with a first set proportion power according to the local oscillation signal to obtain a reference signal;

the second directional coupler is used for inputting a signal of a second set proportion power into the tested device and receiving a reflected signal of the tested device;

the second mixer is used for carrying out down-conversion processing on the reflected signal according to the local oscillation signal to obtain a first detected signal;

the third mixer is used for performing down-conversion processing on an output signal of the signal with the second set proportion power, which is transmitted by the tested device, according to the local oscillation signal to obtain a second tested signal;

the switch is used for switching the first detected signal and the second detected signal.

Optionally, the GNU Radio module further includes: the signal transmitting module and the sweep frequency control module;

the signal transmitting module is connected with the transmitting port of the board card; the sweep frequency control module is connected with the signal transmitting module;

The signal transmitting module is used for converting the frequency of the initial signal into a set frequency and transmitting the converted signal to the hardware circuit from the transmitting port of the board card as a sweep frequency signal;

the sweep frequency control module is used for periodically changing the set frequency of the signal transmitting module within the set frequency range; each set frequency corresponds to a sweep point.

Optionally, in terms of calibrating the preliminary S parameter according to the set error coefficient to obtain the final S parameter, the customization module is specifically configured to:

if the S parameter is the S11 parameter, solving a first set error coefficient according to the measured S11 parameters of the standard components with set quantity and the actual reflection coefficients corresponding to the standard components by using a vector network analyzer, and calibrating the preliminary S11 parameter according to the first set error coefficient to obtain a final S11 parameter;

and if the S parameter is the S21 parameter, measuring the same coaxial line by adopting a vector network analyzer, solving a second set error coefficient according to the measured S21 parameter of the coaxial line and an actual transmission coefficient corresponding to the coaxial line, and calibrating the preliminary S21 parameter according to the second set error coefficient to obtain a final S21 parameter.

The invention also provides an S parameter measurement method based on the GNU Radio, which is applied to the S parameter measurement system based on the GNU Radio;

the method comprises the following steps:

acquiring a reference signal and a target signal; the reference signal is obtained by mixing a signal with a first set proportion of power with a local oscillation signal after amplifying and distributing the sweep frequency signal; the target signal is a first detected signal or a second detected signal; the first measured signal is obtained by amplifying the sweep frequency signal and distributing power, enabling a signal with a second set proportion power to enter a measured device, and mixing a reflected signal of the measured device with a local oscillation signal; the second measured signal is obtained by amplifying the sweep frequency signal and distributing power, enabling a signal with a second set proportion power to enter a measured device, and mixing an output signal transmitted by the measured device with a local oscillation signal;

carrying out frequency domain change on the reference signal and the target signal based on GNU Radio software respectively, and calculating an S parameter according to the signals after the frequency domain change; if the target signal is the first detected signal, the S parameter is an S11 parameter; and if the target signal is the second detected signal, the S parameter is an S21 parameter.

Optionally, frequency domain changes are performed on the reference signal and the target signal based on GNU Radio software, and an S parameter is calculated according to the signals after the frequency domain changes, which specifically includes:

performing fast Fourier transform on the reference signal to obtain a first transformed signal;

performing fast Fourier transform on the target signal to obtain a second transformed signal;

dividing the first transformation signal by the second transformation signal to obtain a preliminary S parameter;

converting the first conversion signal into an amplitude value to obtain a signal with the amplitude value converted;

and (3) carrying out maximum value positioning on the signals after amplitude conversion, and calibrating the preliminary S parameters according to the set error coefficient to obtain final S parameters.

Optionally, calibrating the preliminary S parameter according to the set error coefficient to obtain a final S parameter, which specifically includes:

According to the specific embodiment provided by the invention, the invention discloses the following technical effects:

the S parameter measurement system based on the GNU Radio comprises: the system comprises a board card, a hardware circuit and a GNU Radio module; the transmitting port of the board card is connected with the input end of the hardware circuit; the first output end of the hardware circuit is connected with a first receiving port of the board card; the second output end of the hardware circuit is connected with a second receiving port of the board card; the first receiving port and the second receiving port of the board card are connected with the GNU Radio module; the hardware circuit is connected with the tested device, and the board card, the hardware circuit and the GNU Radio module are adopted to replace a vector network analyzer to realize the measurement of the S parameter of the tested device, so that the cost can be reduced, the volume of the machine body is reduced, and the design and development of the Radio frequency element are facilitated.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of an S parameter measurement system based on GNU Radio according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a GNU Radio module according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a hardware circuit according to an embodiment of the present invention;

fig. 4 is a specific structural block diagram of an S parameter measurement system based on GNU Radio according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of an S11 error calibration model according to an embodiment of the present invention;

fig. 6 is a schematic diagram of an S11 frequency domain measurement result provided in an embodiment of the present invention;

fig. 7 is a schematic diagram of S11 time domain measurement results according to an embodiment of the present invention;

fig. 8 is a schematic diagram of S21 parameter measurement values according to an embodiment of the present invention.

Symbol description:

transmit port-TX _A First receiving port-RX _A Second receiving port-RX _B The device under test comprises a first directional coupler-1, a second directional coupler-2, a device under test-DUT, a switch-3, a first frequency multiplier-4, a first power amplifier-5, a second frequency multiplier-6, a second power amplifier-7, a first mixer-8, a second mixer-9, a third mixer-10, a primary vibration source-11, a third power amplifier-12 and a power divider-13.

Detailed Description

The technical solutions in the embodiments of the present invention will be described below with reference to the accompanying drawings in the embodiments of the present invention.

In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.

Referring to fig. 1, the S parameter measurement system based on GNU Radio of the present embodiment uses software Radio and related hardware to perform sweep measurement on S parameters of a device under test, and the system includes: board card, hardware circuit and GNU Radio module.

Transmitting port TX of the board card _A The input end of the hardware circuit is connected with the input end of the hardware circuit; a first output end of the hardware circuit and a first receiving port RX of the board card _A Connecting; a second output end of the hardware circuit and a second receiving port RX of the board card _B Connecting; a first receiving port RX of the board card _A And a second receiving port RX _B Are all connected with the GNU Radio module; the hardware circuit is connected with the DUT.

The board card is used for sending sweep frequency signals to the hardware circuit. The board card may be a B210 board card.

The hardware circuit is used for outputting a reference signal and a target signal according to the sweep frequency signal.

The reference signal is obtained by mixing a signal with a first set proportion power with a local oscillation signal after amplifying the sweep frequency signal and distributing power; the target signal is a first detected signal or a second detected signal; the first measured signal is obtained by amplifying the sweep frequency signal and distributing power, enabling a signal with a second set proportion power to enter a measured device DUT, and mixing a reflected signal of the measured device DUT with a local oscillation signal; the second measured signal is obtained by amplifying and distributing the sweep frequency signal, enabling a signal with a second set proportion power to enter a measured device DUT, and mixing an output signal transmitted by the measured device DUT with a local oscillation signal.

In one example, referring to fig. 2, the GNU Radio module includes: the device comprises a signal receiving module, a first frequency domain transformation (FFT) module, a second frequency domain transformation (FFT) module, a data dividing module, an amplitude conversion module and a self-defining module.

The signal receiving module is used for sending the reference signal to the first frequency domain transforming module and sending the target signal to the second frequency domain transforming module. The first frequency domain transformation module is used for performing fast Fourier transformation on the reference signal to obtain a first transformation signal. The second frequency domain transformation module is used for performing fast Fourier transformation on the target signal to obtain a second transformation signal. The data dividing module is used for dividing the first transformation signal by the second transformation signal to obtain a preliminary S parameter. The amplitude conversion module is used for converting the first conversion signal into an amplitude value to obtain a signal with the amplitude value converted. The self-defining module is used for carrying out maximum value positioning on the signals after amplitude conversion to obtain signal maximum values, and calibrating the preliminary S parameters according to the set error coefficients to obtain final S parameters; the signal maxima are used to characterize the energy of the swept frequency signal.

It should be noted that, the clutter signal is introduced in the transmission process of the system hardware by the sweep frequency signal, so that the frequency offset occurs, and the energy of the useful signal is larger than the energy of the clutter signal, so that the energy of the useful signal can be accurately read by reading the maximum value of the signal after the amplitude conversion each time, thereby effectively eliminating the frequency offset of the system. Therefore, the self-defining module not only can realize the calibration of the S parameter, but also can solve the problem of hardware frequency offset.

The initial S parameter is calibrated according to the set error coefficient, and the final S parameter is obtained specifically as follows:

and if the S parameter is the S11 parameter, solving a first set error coefficient according to the measured S11 parameters of the standard components with the set number and the actual reflection coefficient corresponding to the standard components by using a vector network analyzer, and calibrating the preliminary S11 parameter according to the first set error coefficient to obtain the final S11 parameter.

After the first set error coefficient and the second set error coefficient are obtained, the first set error coefficient and the second set error coefficient are directly calibrated by adopting the stored first set error coefficient and second set error coefficient after each measurement, the S11 parameter and the S21 parameter are not required to be calibrated by a standard calibration piece each time, and the method is convenient to use.

In another example, still referring to fig. 2, the GNU Radio module further includes: the signal transmitting module and the sweep frequency control module.

The signal transmitting module and the transmitting port TX of the board card _A Connecting; the sweep frequency control module is connected with the signal transmitting module. The signal transmitting module is used for converting the frequency of the initial signal into a set frequency and transmitting the converted signal as a sweep frequency signal from a transmitting port TX of the board card _A To the hardware circuit. The sweep frequency control module is used for periodically changing the set frequency of the signal transmitting module within the set frequency range; each set frequency corresponds to a sweep point.

In another example, referring to fig. 3, the hardware circuit includes: a signal processing circuit, a first directional coupler 1, a second directional coupler 2, a first mixer 8, a second mixer 9, a third mixer 10 and a switch 3.

Transmitting port TX of the board card _A The signal processing circuit, the directional coupler, the second directional coupler 2 and the driven objectThe DUT is sequentially connected; the coupling end of the first directional coupler 1 is connected with a first receiving port RX of the board card through the first mixer 8 _A Connecting; the output end of the second directional coupler 2 is connected with the input end of the device under test DUT; the coupling end of the second directional coupler 2 is connected with a first terminal S1 of the switch 3 through the second mixer 9; the output end of the device under test DUT is connected with the second wiring terminal S2 of the switch 3 through the third mixer 10; a third terminal of the switch 3 and a second receiving port RX of the board card _B And (5) connection.

The signal processing circuit is used for amplifying the sweep frequency signal to obtain a sweep frequency amplified signal. The signal processing circuit specifically comprises: the first frequency multiplier 4, the first power amplifier 5, the second frequency multiplier 6 and the second power amplifier 7 are sequentially connected. The first frequency multiplier 4 is configured to twice amplify the frequency sweep signal to obtain a twice amplified signal. The first power amplifier 5 is configured to amplify the energy of the twice amplified signal to obtain an energy amplified signal. The second frequency multiplier 6 is configured to twice amplify the energy amplified signal to obtain a quadruple amplified signal. The second power amplifier 7 is configured to amplify the energy of the quadruple amplified signal to obtain a swept amplified signal.

The first directional coupler 1 is configured to distribute the power of the swept amplified signal, so that a coupling end of the first directional coupler 1 outputs a signal with a first set proportion of power. The first mixer 8 is configured to perform down-conversion processing on a signal with a first set proportion power according to a local oscillation signal LO OUT, so as to obtain a reference signal. The second directional coupler 2 is used for inputting a signal with a second set proportion power into the DUT and receiving a reflected signal of the DUT. The second mixer 9 is configured to perform down-conversion processing on the reflected signal according to the local oscillation signal LO OUT, so as to obtain a first measured signal. The third mixer 10 is configured to perform down-conversion processing on an output signal of the signal with the second set proportion power after being transmitted by the DUT according to the local oscillation signal LO OUT, so as to obtain a second measured signal. The switch 3 is used for switching the first measured signal and the second measured signal.

The working process of the S parameter measurement system based on GNU Radio in practical application will be described in further detail below with reference to fig. 4.

The S parameter measurement system based on the GNU Radio is divided into a hardware part for processing the Radio frequency signal from the B210 board card and a software part for extracting and calibrating the characteristics of the signal.

The system mainly comprises a B210 board card, a hardware circuit and a GNU Radio module. The system work flow:

(1) The GNU Radio module transmits a command to the B210 board card through a computer.

(2) The B210 board card sends a sweep frequency signal to the hardware part according to the received command, wherein RX of the B210 board card _A End, RX _B End, TX _A The terminal is connected with the hardware circuit. The software part comprises a signal transmitting module, a signal receiving module, a sweep frequency control module, a first frequency domain transformation module (FFT module 1), a second frequency domain transformation module (FFT module 2), a data dividing module, a complex amplitude conversion module and a self-defining module.

(3) The hardware circuitry processes and transmits signals from B210.

(4) The hardware circuit transmits the reflected signal of the DUT or the output signal transmitted by the DUT to the B210 board.

(5) And the B210 board card transmits the signal to the GNU Radio module.

(6) The GNU Radio module performs calibration on the data and stores the calibrated data.

The hardware schematic mainly comprises a power amplifier, a frequency multiplier, a directional coupler, a mixer and a power divider. Workflow of hardware part:

1. still referring to fig. 3, the S11 parameter measurement process is as follows:

when the switch 3 is pulled toward S1, measurement of the S11 parameter is performed. The specific measurement flow is as follows:

(1) The frequency of the sweep frequency signal A is doubled by the first frequency multiplier 4, and a signal B with doubled frequency is obtained.

(2) The signal B is subjected to power amplification by a power first-rate amplifier, and the signal C subjected to power amplification is obtained after the signal B is subjected to the power amplification by a first power amplifier 5.

(3) The frequency of the signal C is doubled by the second frequency multiplier 6 to obtain a signal D with doubled frequency.

(4) The signal D is power amplified by the second power amplifier 7 to obtain a power amplified signal E.

(5) The signal E is divided into a reference signal and an output signal by the first directional coupler 1. The reference signal is transferred to RX of the B210 board card through the first mixer 8 _A The port (specifically, the first mixer 8 and the local oscillator signal LO OUT perform down-conversion processing on the reference signal). The local oscillation source 11 is a signal source for transmitting a fixed frequency signal, and the signal from the local oscillation source 11 is amplified by the third power amplifier 12 to obtain a local oscillation source 11 signal with higher power. The signal from the third power amplifier 12 is divided equally into three local vibration source 11 signals by the power divider 13.

(6) The output signal from the first directional coupler 1 passes through the second directional coupler 2 and is divided into two paths of output signals and reflected signals of the device under test DUT. The reflected signal of the DUT passes through the second mixer 9 to the RX of the B210 board card _B The port (specifically, the second mixer 9 and the local oscillation signal LO OUT perform down-conversion processing on the reference signal).

2. The S21 parameter measurement procedure is as follows:

when the switch 3 is pulled to S2, measurement of the S21 parameter is performed. The specific measurement flow is as follows:

(2) The signal B is subjected to power amplification by the first power amplifier 5, and the signal C after power amplification is obtained by the signal B through the first power amplifier 5.

(5) The signal E is divided into a reference signal and an output signal by the first directional coupler 1. The reference signal is transferred to RX of the B210 board card through the first mixer 8 _A Port (specifically, the first mixer 8 and the local oscillation signal LO OUT perform down-conversion processing on the reference signal and transmit the reference signal to RX of the B210 board card) _A Ports).

(6) The output signal from the first directional coupler 1 passes through the second directional coupler 2 and is divided into two paths of output signals and reflected signals of the device under test DUT.

(7) The output signal from the second directional coupler 2 is passed through the device under test DUT to obtain a signal F.

(8) The signal F is transmitted to RX of the B210 board card through the third mixer 10 _B Port (specifically, the third mixer 10 and the local oscillator signal LO OUT perform down-conversion processing on the reference signal and transmit the reference signal to RX of the B210 board card) _B Ports).

Still referring to fig. 2, the software part workflow:

(1) The signal transmitting module increases the frequency of the low-frequency signal to the signal setting frequency and transmits the signal to the TX of the B210 board card _A The port emits out.

(2) And the sweep frequency control module is used for changing the set frequency of the signal transmission module at regular time so as to achieve the purpose of sweep frequency.

(3) RX on B210 board card _A 、RX _B Is transmitted to port 1 and port 2 of the signal receiving module.

(4) The FFT module fourier transforms the signals of port 1 and port 2.

(5) The data stream from the FFT module 1 is converted to amplitude and transmitted to port 4.

(6) The data dividing module divides the data stream from the FFT module 1 by the data stream of the FFT module 2 and transmits the processed data stream to the port 3.

(7) The user-defined module performs maximum value positioning on the data stream of the port 4 so as to solve the problem of hardware frequency offset. When the radio frequency device works, frequency offset occurs, and when signals are received according to the set frequency, a large error is caused. The algorithm fully utilizes the characteristic that the energy of the signal is much larger than that of clutter, thereby effectively eliminating the frequency offset of the system. The signal is fourier transformed to yield 1024 data points, the magnitude of which indirectly reflects the signal energy at each frequency. The operating frequency is precisely located by finding the maximum of the 1024 data points.

(8) The custom module calibrates the port 3 data stream. When measuring S21, the same coaxial line is measured using a vector network analyzer and system, and the measured value is recorded. And (3) obtaining a correction parameter of the S21 parameter by calculating the ratio between the vector network analyzer and the system measured value, and storing the correction parameter. The system measurements are then multiplied by the correction parameters for each measurement to calibrate the S21 parameter. When measuring S11, three different loads are measured using a vector network analyzer and system, and the measured values are recorded. The error calibration model of fig. 7 is constructed using the three sets of measurements, error coefficients are calculated from the calibration model, and the error coefficients are saved. The error coefficient is used for calibrating S11 the parameter for each subsequent measurement.

The calibration process of the parameters is described in detail below.

In comparison with calibration using a calibration piece, the present embodiment proposes to calibrate S11 parameters using three loads. The calibration model of the S11 parameter is shown in fig. 5. Wherein a and b respectively represent an incident signal and a reflected signal of the system, a ₁ 、b ₁ Representing the incident and reflected signals of the DUT, E ₀₁ 、E ₁₀ 、E ₁₁ 、E ₀₀ Representing frequency response, forward, source match, directivity error, S11, S21, S12, S22 represent actual S11, S21, S12, S22 parameters of the device under test DUT. For the calibration of the S11 parameter, open-circuit, short-circuit, matched load calibration pieces with reflection coefficients of 1, -1, 0 are mostly adopted. However, the calibration element having good reflectivity is high in cost, and the reflectivity measured by the calibration element can reach an ideal reflectivity only in a specific frequency band, thereby affecting the calibration accuracy. In the embodiment, the vector network analyzer is adopted to measure S11 parameters of three groups of loads to be measured, and each load is arranged in the following wayThe reflection coefficient at different frequency points is denoted as Γ _a1 、Γ _a2 、Γ _a3 . S11 parameter measurement is carried out on three groups of loads to be measured by adopting the system, and reflection coefficients of the loads under different frequency points are marked as gamma _m1 、Γ _m2 、Γ _m3 . And solving error coefficients under different frequency points according to an error coefficient calculation formula. In the S21 system parameter calibration, the ratio of the measured value of the S21 parameter on the same coaxial cable line of the vector network analyzer and the system is used as the error coefficient of the S21 system parameter. Error coefficient E of S11 parameter ₀₁ 、E ₁₀ 、E ₁₁ 、E ₀₀ The calculation formula of (i.e. the first set error coefficient) is:

the effectiveness of the S-parameter measurement system based on GNU Radio will be described below.

(1) S11 parameter measurement results

The system builds an error model through three loads, measures S11 parameters of the three loads in a full frequency band through a vector network, and takes S11 vector network measured values under different frequency points as S11 actual values of the three loads under different frequency points. And solving an error coefficient according to the system measured value and the vector network measured value, and correcting the S11 parameter according to the error coefficient, wherein the measurement result is shown in fig. 6. It can be seen that the system has a higher accuracy than conventional SOL calibration.

(2) S11 parameter time domain measurement results

The S-parameters of the measured element are generally measured by a vector network analyzer, including voltage standing waves, insertion loss, phase, delay time, and the like. Taking a reflectance test as an example, the test result is superposition of a plurality of reflection factors of a tested object on a reference end surface, and the influence of the test result can be analyzed only by observing the test result in a time domain. In the time domain, the most intuitive method is a time domain reflectometer, and the time domain analysis can also be realized through a time domain function of a vector network. The system adopts the time domain transformation to the measured S11 parameter to realize the time domain analysis function of the vector network analyzer. The system time domain measurement results are shown in fig. 7. The vector network analyzer is substantially coincident with the system measurements.

(3) S21 parameter frequency domain measurement result

The system measures the full-band S21 parameter of any coaxial cable connector by using a vector network analyzer, and inputs the S21 parameter into the system. And (3) calculating the ratio of the vector network analyzer and the system measured value of the S21 parameter at each frequency point to obtain the correction parameter of the S21 parameter. The S21 parameter measurement result is shown in fig. 8.

The embodiment aims at the problems of high price, large volume, poor flexibility and the like of the vector network analyzer, designs a set of S parameter measuring system with low price and wide frequency range by combining a software Radio module and related hardware, specifically uses GNU Radio software and a Radio frequency device to realize wide-frequency measurement of S11 parameters and S21 parameters of a device to be measured, and can replace a standard component to calibrate the S11 parameters and the S21 parameters. In order to enable the device to be applied to engineering tests, the measurement frequency and the measurement point number can be selected according to actual needs.

In order to realize a corresponding system of the above embodiment to obtain a corresponding technical effect, an S parameter measurement method based on GNU Radio is provided below. The method is applied to the S parameter measurement system based on the GNU Radio in the first embodiment.

The method comprises the following steps:

acquiring a reference signal and a target signal; the reference signal is obtained by mixing a signal with a first set proportion of power with a local oscillation signal after amplifying and distributing the sweep frequency signal; the target signal is a first detected signal or a second detected signal; the first measured signal is obtained by amplifying the sweep frequency signal and distributing power, enabling a signal with a second set proportion power to enter a measured device DUT, and mixing a reflected signal of the measured device DUT with a local oscillation signal; the second measured signal is obtained by amplifying and distributing the sweep frequency signal, enabling a signal with a second set proportion power to enter a measured device DUT, and mixing an output signal transmitted by the measured device DUT with a local oscillation signal.

In one example, the GNU Radio software is used to perform frequency domain change on the reference signal and the target signal, and calculate the S parameter according to the signal after the frequency domain change, which specifically includes:

And performing fast Fourier transform on the reference signal to obtain a first transformed signal.

And performing fast Fourier transform on the target signal to obtain a second transformed signal.

Dividing the first transformed signal by the second transformed signal to obtain a preliminary S parameter.

And converting the first conversion signal into amplitude values to obtain signals with amplitude values converted.

In one example, the calibration of the preliminary S parameter according to the set error coefficient, to obtain the final S parameter, specifically includes:

In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.

The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.

Claims

1. An S parameter measurement system based on GNU Radio, comprising: the system comprises a board card, a hardware circuit and a GNU Radio module;

2. The GNU Radio based S parameter measurement system of claim 1, wherein the GNU Radio module comprises: the device comprises a signal receiving module, a first frequency domain transformation module, a second frequency domain transformation module, a data dividing module, an amplitude conversion module and a self-defining module;

3. The GNU Radio based S parameter measurement system of claim 1, wherein the hardware circuit comprises: the signal processing circuit, the first directional coupler, the second directional coupler, the first mixer, the second mixer, the third mixer and the switch;

4. The GNU Radio based S parameter measurement system of claim 2, wherein the GNU Radio module further comprises: the signal transmitting module and the sweep frequency control module;

5. The GNU Radio-based S parameter measurement system of claim 2, wherein the custom module is configured to:

6. An S parameter measurement method based on GNU Radio, characterized in that the method is applied to the S parameter measurement system based on GNU Radio as set forth in any one of claims 1 to 5;

The method comprises the following steps:

7. The GNU Radio based S parameter measurement method of claim 6, wherein the GNU Radio based software performs frequency domain changes on the reference signal and the target signal, respectively, and calculates S parameters from the frequency domain transformed signals, specifically comprising:

8. The GNU Radio-based S parameter measurement method of claim 7, wherein the preliminary S parameter is calibrated according to a set error coefficient to obtain a final S parameter, specifically comprising: