CN113644920A - Microwave multi-path receiving and transmitting system for brain imaging - Google Patents
Microwave multi-path receiving and transmitting system for brain imaging Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/0003—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/02042—Determining blood loss or bleeding, e.g. during a surgical procedure
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/0507—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves using microwaves or terahertz waves
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/40—Circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
Abstract
The invention relates to a microwave multi-path receiving and transmitting system for brain imaging, which comprises a data workstation, a digital interface circuit, a plurality of transceivers, a plurality of receiving and transmitting integrated antennas and an antenna bracket, wherein the data workstation is connected with the digital interface circuit; the data workstation is connected with the digital interface circuit; the digital interface circuit is connected with the plurality of transceivers; the plurality of transceivers are respectively connected with the plurality of receiving-transmitting integrated antennas; the transceivers are connected through coaxial lines; a plurality of receiving and transmitting integrated antennas are uniformly arranged on the antenna bracket, and the data workstation sends an instruction to select one transceiver to transmit signals; the transceiver receives the instruction and then transmits a signal, the signal is absorbed, reflected and scattered by the tested human brain model and then reaches the transceiving integrated antenna in each direction, the transceiving integrated antenna in each direction transmits the received scattered signal to the transceiver for receiving, and the transceiver measures an S parameter matrix in the state according to the received signal; and repeating the operation to obtain a complete S parameter matrix, and processing the complete S parameter matrix by the data workstation to form a report.
Description
Technical Field
The invention belongs to the field of: the microwave medical imaging field, the radio frequency/microwave communication system field and the medical imaging instrument field, in particular to a microwave multi-path receiving and transmitting system for brain imaging.
Background
It is well known that by using medical imaging systems, medical professionals can intuitively understand detailed images of internal tissue, anatomy and organ sections of patients, thereby reducing the need for invasive investigation procedures to identify, diagnose and assess the health of patients, and to prescribe drugs.
The microwave imaging technology is a novel nondestructive testing method and has the advantages of no damage, no radiation, high accuracy, low cost, small size, portability and the like. In recent years, microwave imaging has attracted wide attention of scholars at home and abroad for the research on the aspects of primary hemorrhage/ischemia type cerebral apoplexy detection, breast cancer detection, pulmonary inflammation detection, bone fracture detection, other noninvasive cancer detection and portable health monitoring.
The current mainstream microwave imaging methods are mainly divided into microwave backscattering tomography methods and microwave radar imaging methods according to the principle, and can be divided into two types of microwave imaging methods, namely time domain and frequency domain, from the aspect of signal processing. Regardless of the microwave imaging method, a microwave signal transceiving system is required. The information of human tissues obtained by single-path signal transceiving is very little, cannot meet the imaging requirement, and multiple-path transceiving is generally designed.
Generally, in a microwave brain stroke imaging system, a technical scheme of a commercial Vector Network Analyzer (VNA) + multiport matrix switch is adopted for multipath transceiving, as shown in fig. 1. The scheme only has two transceivers of two ports of the vector network analyzer actually, and the transceiver is not arranged on each test port connected with the antenna, so that the scheme is a 'pseudo-multipath transceiving' scheme. According to the scheme, the microwave signals are detected by the aid of the commercial vector network analyzer in the actual use process, the built test system is high in cost, large in size and inconvenient to carry, most importantly, only one path of test can be performed at the same time, and the defect of large information obtaining error still exists due to the fact that scanning test of the multi-port matrix switch is adopted.
Synthetic Aperture Radar (SAR) imaging utilizes the synthetic aperture principle to realize high-resolution microwave imaging and has the characteristics of all-time, all-weather, high resolution, large breadth and the like. Synthetic aperture radar imaging is also used for detecting cerebral apoplexy, and because radar imaging is time domain calculation imaging, the synthetic aperture radar imaging is more suitable for long-distance large target imaging, and only cerebral apoplexy bleeding clot or ischemic tissue of 2cm multiplied by 2cm in the brain of a close-distance person is imaged, so that the technical difficulty of realization is large.
Disclosure of Invention
Aiming at the problems that the treatment technology after the cerebral apoplexy is caused is high in cost, part of technology detection is long in time consumption, imaging resolution ratio is not high, the optimal rescue period of the cerebral apoplexy is very easy to delay and the like, the invention develops a microwave multi-path receiving and transmitting system for cerebral imaging, realizes noninvasive detection of the cerebral apoplexy caused by cerebral ischemia or hemorrhagic damage symptoms, assists medical institutions to make timely treatment judgment, reduces cerebral trauma of patients, and improves detection precision and treatment efficiency.
The invention aims to provide a feasible microwave multi-path receiving and transmitting system for brain imaging, so that the detection precision, sensitivity and detection speed of stroke microwave scanning imaging are improved, and the volume and cost are effectively reduced.
In order to achieve the above purposes, the technical scheme adopted by the invention is as follows:
a transceiver, comprising: the structure comprises a top layer structural part 1, a radio frequency front end circuit board 2, a battery 3, a middle structural part 4, an SDR transceiver circuit board 5 and a bottom layer structural part 6;
the top layer structural member 1 is matched and installed with the upper end of the middle structural member 4, the bottom layer structural member 6 is matched and installed with the lower end of the middle structural member 4,
the radio frequency front-end circuit board 2 and the battery 3 are sequentially packaged in an inner space formed by the top layer structural member 1 and the middle structural member 4 from top to bottom;
the SDR transceiver circuit board 5 is packaged in an internal space formed by the middle structural part 4 and the bottom structural part 6;
the radio frequency front-end circuit board 2 is used for processing radio frequency signals generated by the SDR transceiver circuit board 5, switching receiving and transmitting through a receiving and transmitting switch, and transmitting signals meeting transmitting conditions or processing received signals;
the SDR transceiver circuit board 5 is used for generating a required test signal source, demodulating a received signal, processing the demodulated signal into a digital signal and sending the digital signal out through a USB interface;
the SDR transceiver circuit board 5 is also used for clock synchronization.
On the basis of the scheme, the right end of the radio frequency front-end circuit board 2 is provided with a microwave transceiving SMA interface 7, and the left end of the radio frequency front-end circuit board 2 is provided with an expansion serial port 8;
and the radio frequency front-end circuit board 2 is provided with a radio frequency front-end signal conditioning circuit.
On the basis of the above scheme, the radio frequency front end signal conditioning circuit includes: the device comprises a transmitting channel, a receiving channel, a power detection circuit, a phase detection channel and a transceiving switch;
the input end of the transmitting channel is connected with the output end of the SDR transceiver circuit board 5 through a 50 ohm coaxial line,
the transmission channel includes: the system comprises a front-stage low-pass filter, a multi-path amplifier, a numerical control attenuator, an adjustable gain amplifier, a final-stage low-pass filter and a bidirectional directional coupler;
the signal transmitted by the SDR transceiver circuit board 5 is subjected to power regulation by a preceding-stage low-pass filter, a multi-path amplifier, a numerical control attenuator and an adjustable gain amplifier, is subjected to harmonic filtering by a final-stage low-pass filter, and is finally transmitted by switching a transmitting-receiving switch;
the bidirectional directional coupler is used for separating a transmitting signal and an echo signal;
the phase detection channel is used for sending the transmitting signal and the echo signal to an SDR transceiver circuit board 5 for phase test or sending the transmitting signal and the echo signal to a power detection circuit for power value calculation, and specifically comprises: 3 radio frequency switches and 2 digital controlled attenuators;
the receiving channel includes: the device comprises an amplitude limiter, a preceding-stage low-pass filter, an LNA amplifier, a directional coupler, a multi-path amplifier, a numerical control attenuator, an adjustable gain amplifier and a final-stage low-pass filter;
the directional coupler is used for obtaining a coupling value of a received signal and sending the coupling value to the power detection circuit;
signals received by the transceiver are switched to a receiving channel through a receiving-transmitting switch, the received signals reach the LNA through the amplitude limiter and the low-pass filter, the amplitude of the received signals is adjusted through the multi-path amplifier, the numerical control attenuator and the adjustable gain amplifier, and finally the signals are sent to the SDR transceiver circuit board 5 through the final-stage low-pass filter and the radio frequency switch to be subjected to phase testing;
the power detection circuit includes: an STM32 controller and 3-way ADC converter, multiple amplifier and RMS detector;
the STM32 controller, the 3-channel ADC converter, the multiple amplifier and the RMS detector respectively form a transmitting power detection circuit, an echo power detection circuit and a receiving power detection circuit, the transmitting power detection circuit is used for measuring the power value of a transmitting signal, the echo power detection circuit is used for measuring the power value of an echo signal, and the receiving power detection circuit is used for measuring the power value of a receiving signal according to the coupling value of the receiving signal;
the STM32 controller is used for sending the transmitting signal power value, the echo signal power value and the receiving signal power value to the SDR transceiver circuit board 5 through the serial port for forwarding; and is also used for controlling each component.
On the basis of the scheme, the front end of the intermediate structural member 4 is provided with a coherent clock output port 10, the rear end is provided with a coherent clock input port 9, and the left end is provided with a power switch 11 and a charging indicator lamp 12; coherent clock input port 9 and coherent clock output port 10 are connected to SDR transceiver circuit board 5 for synchronization between the transceivers.
On the basis of the scheme, a charging interface 14 and a USB interface 13 are sequentially arranged at the left end of the SDR transceiver circuit board 5 from front to back;
the SDR transceiver circuit board 5 is provided with an FPGA chip, a broadband double-transceiving channel software radio chip and a USB3.0 special interface chip, the FPGA chip is used as a main control chip, the broadband double-transceiving channel software radio chip is used as a radio frequency emission source, and the USB3.0 special interface chip is used as a digital interface.
On the basis of the scheme, the model of the FPGA chip is EP4CE40F23 or EP4CE30F23, the model of the broadband double-transceiving channel software radio chip is LMS7002M, and the model of the USB3.0 special interface chip is CYUSB 3014-BZXC.
A microwave multi-channel transceiver system for brain imaging, which applies the transceiver, comprises: the system comprises a data workstation, a USB3.0 digital interface circuit, a plurality of transceivers, a plurality of receiving and transmitting integrated antennas and an antenna bracket;
the data workstation is connected with a USB3.0 digital interface circuit through a USB3.0 data line;
the USB3.0 digital interface circuit is connected with the plurality of transceivers through USB3.0 data lines;
the transceivers are respectively connected with the receiving and transmitting integrated antennas through flexible coaxial connecting wires;
the transceivers are connected through a coaxial line;
the antenna bracket is a circular bracket, and the plurality of receiving and transmitting integrated antennas are uniformly arranged on the antenna bracket;
the data workstation is used for sending a control command through a USB3.0 data line and selecting one transceiver of the transceivers to transmit microwave signals;
the USB3.0 digital interface circuit is used for forwarding the control instruction to one transceiver in the transceivers, the transceiver is switched to a transmitting mode after receiving the control instruction, and other transceivers are switched to a receiving mode;
the transceiver in the transmitting mode is used for transmitting a single-frequency microwave signal corresponding to the control instruction, the single-frequency microwave signal is transmitted through the receiving-transmitting integrated antenna and is absorbed, reflected and scattered by the tested human brain model to reach the receiving-transmitting integrated antenna in each direction, the receiving-transmitting integrated antenna in each direction transmits the received scattered signal to the transceiver in the receiving mode, and the transceiver in the receiving mode measures an S parameter matrix in the state according to the received signal;
repeating the operation, sequentially measuring the S parameter matrixes in each state, and finally obtaining a complete S parameter matrix, wherein the complete S parameter matrix is uploaded to a data workstation through a USB3.0 data line for recording and storing;
and after the data workstation obtains a complete S parameter matrix, the S parameter matrix is processed through an imaging algorithm to invert the dielectric constant spatial distribution image of the tested human brain model, so that the brain image of the tested human brain model is obtained, the position and the size of bleeding or ischemia can be clearly distinguished, and a report is formed.
On the basis of the scheme, the system further comprises a cloud end, the cloud end is communicated with the data workstation through the 5G network, and the data workstation transmits the obtained image and the obtained report to the cloud end through the 5G network.
On the basis of the scheme, the transceiver is a high dynamic range microwave transceiver of 100 MHz-3.5 GHz.
On the basis of the scheme, the number of the transceivers is 16.
On the basis of the scheme, the imaging algorithm is a deformed Bonn iteration algorithm (DBIM).
On the basis of the scheme, the microwave transceiving SMA interface 7 on the transceiver is connected with the transceiving integrated antenna through a flexible coaxial connecting line.
The invention has the beneficial effects that:
the invention can effectively reduce the cost and the volume of the microwave imaging equipment, and can improve the detection precision and the test sensitivity of the microwave imaging equipment in a customized manner.
The multichannel transceiving system is based on a high dynamic range microwave transceiver, is used for early diagnosis of stroke, reconstructs a brain tissue lesion image caused by cerebral ischemia or cerebral hemorrhage, assists a medical institution to make corresponding diagnosis, and mainly has the following advantages:
(1) the portable type: the wearable helmet comprises an antenna support, wherein the antenna support is provided with a plurality of uniformly arranged receiving and transmitting integrated antennas and a data workstation;
(2) the accuracy is high: the accuracy rate of hemorrhagic stroke is more than 97%, and the accuracy rate of ischemic stroke is more than 75%;
(3) the detection speed is high: reports are given within 5 minutes;
(4) the cost is low: the cost of each set of equipment is within 10 ten thousand yuan.
The invention can quickly detect the cerebral apoplexy and the cerebral arterial thrombosis, and can be used for mobile emergency centers such as ambulances, temporary emergency stations and the like, community hospitals, clinical intensive care or real-time monitoring of institutions of residence and the like.
Drawings
The invention has the following drawings:
fig. 1 is a block diagram of a technical scheme of a vector network analyzer + multi-port matrix switch.
Fig. 2 is a schematic diagram of a microwave multi-channel transceiver system for brain imaging according to the present invention.
Fig. 3 is a schematic block circuit diagram of a transceiver.
Fig. 4 is a circuit schematic of the rf front end circuit board.
Fig. 5 is a functional block diagram of an SDR transceiver circuit board.
Fig. 6 is an exploded view of the structure of the transceiver.
Fig. 7 is a schematic diagram of the microwave multi-path transceiving system for brain imaging applied to a tested human brain model.
In fig. 6: 1-a top layer structural member; 2-a radio frequency front end circuit board; 3-a battery; 4-an intermediate structural member; a 5-SDR transceiver circuit board; 6-bottom layer structural member; 7-a microwave transceiving SMA interface; 8-expanding the serial port; 9-coherent clock input port; 10-coherent clock output port; 11-a power switch; 12-a charge indicator light; 13-a USB interface; 14-charging interface.
Detailed Description
The invention is described in further detail below with reference to figures 2-7.
As shown in fig. 2, the microwave multi-path transceiver system for brain imaging according to the present invention is composed of a cloud, a data workstation, a USB3.0 digital interface circuit, a plurality of transceivers (16 transceivers are shown in the figure), a plurality of integrated transceiver antennas, and an antenna support.
Working principle of microwave multi-path transceiving system for brain imaging
The data workstation sends a control instruction through a USB3.0 data line, selects one transceiver of a plurality of transceivers (taking 16 paths as an example in fig. 2) to transmit a microwave signal, the USB3.0 digital interface circuit forwards the control instruction to the corresponding transceiver (such as the 9 th transceiver in fig. 2), and the transceiver switches to a transmission mode after receiving the control instruction and transmits a single-frequency microwave signal corresponding to the control instruction. And the other transceivers are switched to the receiving mode. When the transceiver in the transmission mode works, a microwave signal (a single-frequency signal corresponding to a control instruction) with a specific frequency, amplitude and phase is transmitted, the microwave signal is transmitted through the receiving-transmitting integrated antenna, and is absorbed, reflected and scattered by a tested human brain model and then reaches the receiving-transmitting integrated antenna in each direction, the receiving-transmitting integrated antenna in each direction transmits the received scattered signal to the transceiver in the reception mode through the flexible coaxial connecting line, so as to obtain an S parameter matrix in the state, wherein the S parameter matrix is generally represented by an Snp matrix, n and p respectively represent port numbers of the transceiver, and the transceiver in this embodiment has 16 ports in total. And sequentially switching the modes of the transceivers, sequentially measuring the S parameter matrixes in each state, and finally obtaining a complete S parameter matrix. The complete S parameter matrix is uploaded to a data workstation through a USB3.0 data line and recorded and stored. After the data workstation obtains the complete S parameter matrix, the dielectric constant spatial distribution image of the tested human brain model is inverted through the imaging algorithm processing (deformation Bonn iterative algorithm), so that the brain image of the tested human brain model is presented, the position and the size of bleeding or ischemia can be clearly distinguished, and a report is formed. The data workstation wirelessly transmits the obtained images and reports to the cloud end through the communication 5G network, so that doctors can make further diagnosis.
The core of the invention is a transceiver, which is a high dynamic range microwave transceiver of 100MHz to 3.5 GHz. The signal path of the transceiver consists of a transmitting channel and a receiving channel, and the transmitting channel and the receiving channel are switched to the same output port (namely a microwave transceiving SMA interface 7 on the transceiver) through a switch. The dynamic range of the transceiver as the transmitting end is 0-80dB, and the guarantee value of the full-section highest output power is +30 dBm. The transceiver is used as the dynamic range of the receiving end and is 0-120dB, and the sensitivity guarantee value is-112 dBm.
Fig. 3 shows a schematic block circuit diagram of the transceiver. The system mainly comprises a signal synthesis and clock synchronization circuit (also called a signal synthesis and DDS clock synchronization interface board), a 2 x 2MIMO (multiple input multiple output) Software Defined Radio (SDR) transceiver circuit (also called a Software Radio transceiver) and a Radio frequency front end signal conditioning circuit.
The signal synthesis and clock synchronization circuit and the software radio transceiver circuit are designed on a PCB board called SDR transceiver circuit board 5, and the radio frequency front end signal conditioning circuit is arranged on another circuit board called radio frequency front end circuit board 2.
The radio frequency front-end circuit board 2 is used for processing radio frequency signals generated by the SDR transceiver circuit board 5, switching to transmit and receive through the transmit-receive switch, and sending signals meeting the transmitting conditions to the transmit-receive integrated antenna for transmitting (or processing signals received by the transmit-receive integrated antenna).
The SDR transceiver circuit board 5 is used for generating a required test signal source, demodulating a received signal, processing the demodulated signal into a digital signal and sending the digital signal out through a USB interface (namely a USB interface 13);
another function of the SDR transceiver board 5 is clock synchronization.
Fig. 4 is a schematic block circuit diagram of the rf front end circuit board. It is mainly composed of a transmitting channel, a receiving channel, a power detection circuit, a phase detection channel and a receiving-transmitting switch. The input of the transmitting channel is connected with the transmitting output of the SDR transceiver circuit board 5 through a 50 ohm coaxial line, the signal transmitted by the SDR transceiver circuit board 5 sequentially passes through a pre-stage low-pass filter, a multi-path amplifier, a numerical control attenuator and an adjustable gain amplifier to adjust power, passes through a final-stage low-pass filter to filter harmonic waves, is switched by a transmitting-receiving switch to be output from a testing port (namely a microwave transmitting-receiving SMA interface 7 on the transceiver) to a transmitting-receiving integrated antenna, and then the testing signal is transmitted. Signals received by the receiving and transmitting integrated antenna are switched to a receiving channel through the receiving and transmitting switch to be processed, reach the LNA amplifier through the amplitude limiter and the low-pass filter in sequence, adjust the amplitude of the received signals through circuits such as the multistage amplifier and numerical control attenuation, and finally are sent to the receiver 2 of the SDR transceiver circuit board 5 through the final-stage low-pass filter and the radio frequency switch to be subjected to phase testing. The power detection circuit includes: the STM32 controller further comprises a 1-path ADC converter, a double-channel detector, a 1-path ADC converter and a single-channel detector, the STM32 controller, the 1-path ADC converter and the double-channel detector form a transmitting power detection circuit and an echo power detection circuit, and the STM32 controller, the 1-path ADC converter and the single-channel detector form a receiving power detection circuit.
A bidirectional directional coupler (the coupling degree is 20dB) is inserted in the transmitting channel before a transmitting-receiving switch, a transmitting signal and an echo signal are separated, and then the two signals are transmitted to two radio frequency switches, or the two signals are transmitted to a two-channel detector to detect and measure a power value, or the two signals are simultaneously transmitted to a receiver 1 and a receiver 2 of an SDR transceiver circuit board 5 to carry out phase test, so that the amplitude and the phase of the transmitting signal and the echo signal are obtained, the amplitude and the phase of S11 are calculated, S11 represents the echo quantity of a port 1 to be more than the transmitting quantity of the port 1, and the port reflection performance of the port 1 is reflected. Similarly, the receiving channel also inserts a directional coupler between the LNA amplifier and the multi-path amplifier, and the directional coupler is used for obtaining the coupling value of the receiving signal and obtaining the power value of the receiving signal through the single-channel detector.
The circuit schematic diagram of the radio frequency front-end circuit board is shown in fig. 3, specifically, in the right part of fig. 3, a signal transmitted by the software radio transceiver circuit first passes through a front-stage low-pass filter, a multi-path amplifier and a digital controlled attenuator, then passes through an adjustable gain amplifier and a final-stage low-pass filter, then is adjusted to the power set by software through the ALC circuit controlled by the software, and finally is switched and output to a port (namely, a microwave transceiver SMA interface 7 on a transceiver) connected with a transceiver antenna through a high-isolation transceiver switch, and the signal is transmitted to the transceiver antenna to be transmitted. A bidirectional directional coupler (coupler) at the output end of the transmitting channel can couple the transmitting power and the port echo power to two ports respectively, and the two paths are switched by a radio frequency switch and sent to a receiving end of an RMS detector or an LMS7002M chip in a software radio transceiver circuit respectively. If the two paths are switched to the RMS detector by the radio frequency switch, the RMS detector can measure the transmitting signal power a1 and the echo signal power b1, so as to calculate the amplitude value of the port reflection parameter S11 of the port, and can convert the Voltage Standing Wave Ratio (VSWR) of the port. If the two paths are switched to the receiving end of the LMS7002M chip in the software radio transceiver circuit by the radio frequency switch, the phase information of the transmitting signal a1 and the echo signal b1 can be demodulated.
And the receiving channel is used for processing the signals which are transmitted by the transceiver and received by the receiving-transmitting integrated antenna and are scattered by the tested human brain model (or the tested human brain) and transmitted by other transceivers, so as to obtain the power and the phase of the received signals. After receiving the signal, the receiving antenna enters a receiving channel through a high-isolation receiving and transmitting switch. The received signal is processed by the amplitude limiter, and the amplitude of the received signal is limited within +10dBm, so that the transceiver is prevented from being damaged by the overlarge received signal. Then enters the LNA amplifier through the front-stage low-pass filter for amplification and noise suppression, then is amplified to a range which can be received by an LMS7002M chip in the software radio transceiver circuit through the two-stage low-noise amplifier, the numerical control attenuator and the variable gain amplifier, and finally is sent to a receiving end of the LMS7002M chip in the software radio transceiver circuit through the final-stage low-pass filter and the radio frequency switch, and the phase of the received signal is demodulated by the receiving end of the LMS7002M chip in the software radio transceiver circuit. Similarly, the received signal is led out through a directional coupler and sent to a detector to measure the power b2 of the received signal, so that the transmission parameters S21 of the tested human brain model (or the tested human brain) can be tested. S21 represents the 1 port transmission quantity in the wave ratio of the 1 port transmission received by the 2 port, which reflects the influence of the device between the 1 port and the 2 port on the microwave transmission, and is a transmission parameter.
Therefore, through multiple scanning tests and data recording, the whole system can test all S parameter matrixes of the tested human brain model (or the tested human brain) under 16 ports, and finally uploads the S parameter matrixes to the data workstation for inversion imaging processing.
The Voltage Standing Wave Ratio (VSWR) is detected by a broadband double-path RMS power detector HMC1030LP5E of ADI company, the detection range is-55 dBm to +15dBm, the input detection dynamic range is 70dB, and the power detection precision can reach 0.25 dB.
The variable gain amplifier adopts ADL5240ACPZ-R7 of ADI company, the gain adjusting range is-31.5 dB to +17.6dB, and the gain adjusting precision is 0.25 dB. The detector and the variable gain amplifier are matched with an STM32 controller, and finally, the Automatic Level Control (ALC) function of a transmitting signal can be realized.
As shown in fig. 5, the circuit of the SDR transceiver circuit board 5 mainly comprises an FPGA chip (EP4CE40F23 or EP4CE30F23) as a main control chip (MCU), a broadband dual transceiving channel software radio chip LMS7002M as a radio frequency emission source, and a USB3.0 dedicated interface chip CYUSB3014-BZXC as a digital interface. The core circuit is a one-transmitter-two-receiver circuit built by an LMS7002M chip, and mainly comprises a transmitter, a receiver 1 and a receiver 2, wherein the transmitter, the receiver 1 and the receiver 2 are illustrated in FIG. 4. The main performance parameters of the circuit are as follows:
the broadband dual-receiving-transmitting channel software radio chip comprises: lime Microsystems LMS7002M FPRF
An FPGA chip: altera Cyclone IV EP4CE40F 23-is also compatible with EP4CE30F23
Memory: 256MB DDR2 SDRAM
USB3.0 special interface chip: cypress USB3.0 CYUSB3014-BZXC
An oscillator: rakon RPT7050A @30.72MHz
Continuous frequency range: 100 kHz-3.8 GHz
Bandwidth: 61.44MHz
Radio frequency connection: FL connectors (6 RX, 4 TX, 2 CLK I/O)
Power output (CW): maximum 10dBm
Multiplexing: 2 x 2MIMO
Power supply: micro USB connector or optional external power supply
A status indicator lamp: programmable LED
Size: 100 mm x 60 mm
The structure of the transceiver is shown in fig. 6.
The transceiver is the cuboid structure, mainly includes: the structure comprises a top layer structural part 1, a radio frequency front end circuit board 2, a battery 3, a middle structural part 4, an SDR transceiver circuit board 5 and a bottom layer structural part 6;
the top layer structural member 1 and the bottom layer structural member 6 are respectively matched with the middle structural member 4 and are mainly used for shielding;
the radio frequency front-end circuit board 2 and the battery 3 are sequentially packaged in an internal space formed by the top layer structural member 1 and the middle structural member 4 from top to bottom, the right end of the radio frequency front-end circuit board 2 is provided with a microwave transceiving SMA interface 7, the left end of the radio frequency front-end circuit board 2 is provided with an extended serial port 8, and the connection mode of the extended serial port 8 is realized by adopting the prior art;
the front end of the middle structural member 4 is provided with a coherent clock output port 10, the rear end is provided with a coherent clock input port 9, the left end is provided with a power switch 11 and a charging indicator lamp 12, and the connection mode of the coherent clock output port 10, the coherent clock input port 9, the power switch 11 and the charging indicator lamp 12 is realized by adopting the prior art;
the SDR transceiver circuit board 5 is packaged in an internal space formed by the middle structural part 4 and the bottom structural part 6;
the left end of the SDR transceiver circuit board 5 is sequentially provided with a charging interface 14 and a USB interface 13 from front to back, and the connection mode of the charging interface 14 and the USB interface 13 is realized by adopting the prior art;
the charging interface 14 is a 12V DC charging interface, and the USB interface 13 is a B-type USB3.0 interface
The signal transmission between the signal source of the SDR transceiver circuit board 5 and the interface circuit and the radio frequency signal conditioning circuit of the radio frequency front end circuit board 2 is through the coaxial connecting line, and is isolated through the middle structural part 4, and the top layer structural part 1 and the bottom layer structural part 6 are used for shielding the internal circuit from the outside.
Fig. 7 is a schematic diagram of the microwave multi-path transceiver system applied to the tested human brain model.
Those not described in detail in this specification are within the skill of the art.
Claims (12)
1. A transceiver, comprising: the system comprises a top layer structural part (1), a radio frequency front end circuit board (2), a battery (3), a middle structural part (4), an SDR transceiver circuit board (5) and a bottom layer structural part (6);
the top layer structural member (1) is matched and installed with the upper end of the middle structural member (4), the bottom layer structural member (6) is matched and installed with the lower end of the middle structural member (4),
the radio frequency front-end circuit board (2) and the battery (3) are sequentially packaged in an inner space formed by the top layer structural member (1) and the middle structural member (4) from top to bottom;
the SDR transceiver circuit board (5) is packaged in an inner space formed by the middle structural part (4) and the bottom structural part (6).
2. The transceiver of claim 1, wherein the right end of the radio frequency front end circuit board (2) is provided with a microwave transceiving SMA interface (7), and the left end of the radio frequency front end circuit board (2) is provided with an expansion serial port (8);
and the radio frequency front-end circuit board (2) is provided with a radio frequency front-end signal conditioning circuit.
3. The transceiver of claim 2, wherein the radio frequency front end signal conditioning circuit comprises: the device comprises a transmitting channel, a receiving channel, a power detection circuit, a phase detection channel and a transceiving switch;
the input end of the transmitting channel is connected with the output end of the SDR transceiver circuit board (5).
4. A transceiver according to claim 3, wherein the transmission channel is used for processing signals transmitted by the SDR transceiver circuit board (5) and transmitting the signals after being switched by the transceiver switch, and comprises: the system comprises a front-stage low-pass filter, a multi-path amplifier, a numerical control attenuator, an adjustable gain amplifier, a final-stage low-pass filter and a bidirectional directional coupler; the bidirectional directional coupler is used for separating a transmitting signal and an echo signal.
5. The transceiver of claim 4, wherein the phase detection path is configured to send the transmit signal and the echo signal to an SDR transceiver board (5) for phase testing or to send the transmit signal and the echo signal to a power detection circuit for power level calculation, comprising: 3 radio frequency switches and 2 digital controlled attenuators.
6. The transceiver of claim 5, wherein the receive path is configured to process the received signal and transmit the processed signal to the SDR transceiver board (5) through the rf switch for phase testing, and comprises: the device comprises a limiter, a pre-stage low-pass filter, an LNA amplifier, a directional coupler, a multi-path amplifier, a numerical control attenuator, an adjustable gain amplifier and a final-stage low-pass filter.
7. The transceiver of claim 6, wherein the directional coupler is configured to obtain a coupling value of the received signal and to send the coupling value to the power detection circuit.
8. The transceiver of claim 7, wherein the power detection circuit comprises: the controller, the 3-path ADC converter, the multiple amplifier and the RMS detector;
the controller, the 3-path ADC, the multiple amplifier and the RMS detector respectively form a transmitting power detection circuit, an echo power detection circuit and a receiving power detection circuit, the transmitting power detection circuit is used for measuring the power value of a transmitting signal, the echo power detection circuit is used for measuring the power value of an echo signal, and the receiving power detection circuit is used for measuring the power value of a receiving signal according to the coupling value of the receiving signal;
the controller is used for sending the transmitting signal power value, the echo signal power value and the receiving signal power value to an SDR transceiver circuit board (5) through a serial port for forwarding.
9. The transceiver according to claim 1, wherein the front end of the intermediate structure member (4) is provided with a coherent clock output port (10), the rear end is provided with a coherent clock input port (9), and the left end is provided with a power switch (11) and a charging indicator lamp (12); the coherent clock input port (9) and the coherent clock output port (10) are connected with the SDR transceiver circuit board (5) and used for synchronization among a plurality of transceivers.
10. The transceiver of claim 1, wherein the SDR transceiver circuit board (5) is provided with a charging interface (14) and a USB interface (13) at the left end thereof from front to back;
the SDR transceiver circuit board (5) is provided with an FPGA chip, a broadband double receiving and transmitting channel software radio chip and a USB3.0 special interface chip, the FPGA chip is used as a main control chip, the broadband double receiving and transmitting channel software radio chip is used as a radio frequency emission source, and the USB3.0 special interface chip is used as a digital interface.
11. A microwave multiplexing transceiver system for brain imaging, using the transceiver of any one of claims 1-10, comprising: the system comprises a data workstation, a digital interface circuit, a plurality of transceivers, a plurality of receiving and transmitting integrated antennas and an antenna bracket;
the data workstation is connected with the digital interface circuit;
the digital interface circuit is connected with a plurality of transceivers;
the transceivers are respectively connected with the receiving and transmitting integrated antennas;
the transceivers are connected through a coaxial line;
the plurality of receiving and transmitting integrated antennas are uniformly arranged on the antenna bracket;
the data workstation is used for sending a control command and selecting one transceiver in the plurality of transceivers to transmit microwave signals;
the digital interface circuit is used for forwarding the control instruction to one transceiver in the transceivers, the transceiver is switched to a transmitting mode after receiving the control instruction, and other transceivers are switched to a receiving mode;
the transceiver in the transmitting mode is used for transmitting microwave signals corresponding to the control instructions, the microwave signals are transmitted through the receiving-transmitting integrated antenna and reach the receiving-transmitting integrated antenna in each direction after being absorbed, reflected and scattered by the tested human brain model, the receiving-transmitting integrated antenna in each direction transmits the received scattered signals to the transceiver in the receiving mode, and the transceiver in the receiving mode measures an S parameter matrix in the state according to the received signals;
repeating the operation, sequentially measuring the S parameter matrixes in each state, and finally obtaining a complete S parameter matrix which is uploaded to a data workstation through a digital interface circuit for recording and storing;
and after the data workstation obtains a complete S parameter matrix, processing the S parameter matrix through an imaging algorithm, inverting the dielectric constant spatial distribution image of the tested human brain model to obtain the brain image of the tested human brain model, and distinguishing the position and the size of bleeding or ischemia to form a report.
12. The microwave multiplex system for brain imaging according to claim 11, further comprising a cloud in communication with a data workstation for transmitting the resulting images and reports to the cloud.
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