Pulse microwave biological effect experiment radiation field on-line measurement system

Abstract

The utility model discloses a pulse microwave biological effect experiment radiation field on-line measurement system which is characterized in that a transmitting waveguide horn antenna is electrically connected with a first waveguide coupler, and a coupling port of the first waveguide coupler is connected with a low-loss cable and then is connected to a first sampling channel of a digital oscilloscope through a first microwave broadband attenuator and a first microwave detector; the first waveguide coupler is connected with a high-power microwave source through a transmission waveguide; the receiving waveguide probe antenna is electrically connected with a second waveguide coupler and is arranged opposite to the transmitting waveguide horn antenna, and a coupling port of the second waveguide coupler is connected with a low-loss cable and then is connected to a second sampling channel of the digital oscilloscope through a second microwave broadband attenuator and a second microwave detector; the absorption load is arranged on one side of the receiving waveguide probe antenna; and the test bracket is made of a non-metal material and is used for supporting the receiving waveguide probe antenna and the absorption load. According to the utility model, accurate monitoring and measurement of ultrahigh-power and ultra-short pulse microwave peak power density can be realized.

Description

Technical Field

[0001] The utility model relates to a microwave radiation field measuring device, in particular to an online measurement system for pulse microwave bio-effect experiment radiation field. Background Art

[0002] At present, the microwave bioeffect research in the world usually uses the specific absorption rate (SAR) to determine the dose-effect relationship, which is defined as the microwave energy or power absorbed by a unit mass of tissue. Since SAR is directly defined on the irradiated tissue and difficult to measure in practice, it is generally necessary to use the radiation field parameters that can be actually measured, such as power density and electric field strength, combined with the electromagnetic parameters of human tissue, to estimate through calculation. At present, there are better measurement methods for continuous wave radiation, but there are still challenges and bottlenecks in the measurement of microsecond or even nanosecond pulse microwave radiation field power density.

[0003] In conventional electromagnetic environment measurement, the most common power measurement method is the receiving antenna and spectrum analyzer method, that is, the RF environment signal received by the receiving antenna is fed into the spectrum analyzer through the RF cable. This method can not only measure the field strength amplitude, but also measure the spectrum of the environment. When using a spectrum analyzer for measurement, in order to reduce measurement errors, the instrument's resolution bandwidth, video bandwidth, and scanning speed (or time) and other parameters are often set according to the characteristics of the signal to be measured. The scanning time of the spectrum analyzer is related to the measurement bandwidth, resolution bandwidth (bandwidth of the signal filter), etc. Since the response time of circuits with different bandwidths is different, the response time of circuits with wider bandwidths is usually faster than that of circuits with narrower bandwidths. If the scanning time is too fast, the circuit will not have time to respond and display errors will occur; but for pulse signals, if the scanning time is too slow, it is difficult to capture the pulse signal, and nonlinear distortion is likely to occur when the signal is too large, making the test results inaccurate. Since the circuit response time of the spectrum analyzer is in the ms order, this method is suitable for the measurement of continuous waves or wide pulses with low field strength environments, but not for the measurement of ultra-short pulse signals at the ns level.

[0004] Another common method is the power meter measurement method. Power meters that cover GHz are expensive, and the pulse response time is generally at least tens of ns. The measurement accuracy is difficult to meet the requirements of measuring ultra-short pulses at the ns level and high-power signals with an average power of tens of kW. Utility Model Content

[0005] Purpose of the utility model: In view of the problems existing in the prior art, the utility model provides an online measurement system for the radiation field of a pulsed microwave bioeffect experiment, which can realize the accurate monitoring and measurement of the peak power density of ultra-high power (average power of tens of kW) and ultra-short pulse (pulse width of more than ten ns) microwaves, and can simultaneously directly display the monitored value and measured value of the peak power density at the irradiation point, the time domain and frequency domain waveforms, the peak stability and field uniformity and other parameters, thereby solving the engineering problem of accurate and safe measurement of high-power microwave radiation field parameters with ultra-high power, short pulse and carrier frequency above GHz at the sample platform.

[0006] Technical solution: A pulse microwave biological effect experiment radiation field online measurement system, including:

[0007] The transmitting waveguide horn antenna is electrically connected to the first waveguide coupler. The coupling port of the first waveguide coupler is connected to a low-loss cable and then connected to the first sampling channel of the digital oscilloscope through a first microwave broadband attenuator and a first microwave detector. The first waveguide coupler is connected to a high-power microwave source through a transmission waveguide.

[0008] The receiving waveguide probe antenna is electrically connected to the second waveguide coupler and is arranged opposite to the transmitting waveguide horn antenna. The coupling port of the second waveguide coupler is connected to a low-loss cable and then connected to the second sampling channel of the digital oscilloscope via a second microwave broadband attenuator and a second microwave detector;

[0009] The absorbing load is arranged on one side of the receiving waveguide probe antenna;

[0010] The test bracket is made of non-metallic material and is used to support the receiving waveguide probe antenna and absorb the load.

[0011] In one embodiment, the low-loss cable is a double-shielded coaxial cable or a semi-rigid coaxial cable.

[0012] In one embodiment, the length of the low-loss cable is 20-50m.

[0013] In one embodiment, the low-loss cable has a radio frequency loss of less than 1 dB per meter.

[0014] In one embodiment, the first microwave detector and the second microwave detector are semiconductor-based demodulating logarithmic amplifiers.

[0015] In one of the embodiments, the detection output ends of the first microwave detector and the second microwave detector are connected to the sampling channel of the digital oscilloscope through a coaxial cable with a length of less than 1 m.

[0016] In one embodiment, the test bracket is a lifting bracket, which is used to adjust the test receiving and transmitting distance. Optionally, the lifting bracket includes a transmission mechanism and a driving mechanism, the receiving waveguide probe antenna and / or the absorbing load are installed on the transmission mechanism, and the transmission mechanism and the driving mechanism are connected; the driving mechanism outputs linear or rotational motion, and the transmission mechanism converts the linear or rotational motion into linear motion of the receiving waveguide probe antenna and / or the absorbing load.

[0017] Compared with the prior art, the utility model has the following beneficial effects:

[0018] (1) Using waveguide probes and transmitting horns as transceiver antennas can meet the test requirements of high-power microwave radiation fields in different bands and have a wide range of applications. At the same time, since the waveguide probes and transmitting horn antennas have wider beams, the alignment error can be reduced.

[0019] (2) The high-power microwave pulse signal received by the waveguide antenna is transmitted and attenuated by using a waveguide coupler and a microwave broadband attenuator. On the one hand, this can keep the test personnel and test instruments away from the high-power test area, avoid the harm of high power to personnel and instruments, and reduce measurement errors. On the other hand, by placing the high-speed microwave detector after the RF coaxial cable and the microwave broadband attenuator, the low-loss RF coaxial cable can be used to attenuate the RF microwave signal itself, and the received high-power microwave signal can be attenuated to the linear working range of the high-speed microwave detector, thereby improving the dynamic range and accuracy of the measurement and also improving the flexibility of the test system.

[0020] (3) Using a high-speed microwave detector to perform envelope detection on the tested microwave pulse signal and then reading it with an oscilloscope can greatly expand the frequency range of the high-power microwave radiation field. Usually, when an oscilloscope measures a radio frequency signal, it is limited by the bandwidth and sampling rate of the oscilloscope and can only measure signals with lower frequencies (about one-tenth of the sampling rate). Therefore, it is impossible to directly measure high-power microwave signals of several GHz or even more than ten GHz with an existing oscilloscope. After detecting the microwave pulse signal with a high-speed microwave detector, the oscilloscope can measure the signal's amplitude, rise time, pulse width and other parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure of an online measurement system for pulse microwave biological effect experiments according to an embodiment of the present application;

[0022] Figure 2 A sensitivity calibration curve of a microwave detector according to an embodiment of the present application;

[0023] Figure 3 An embodiment of the present application is a liftable test stand. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below with reference to the accompanying drawings.

[0025] See also Figure 1 A pulse microwave bio-effect experiment radiation field online measurement system, the system includes a transmission waveguide, a transceiver waveguide antenna, a microwave cable, a waveguide coupler, a microwave broadband attenuator, a microwave detector, and a digital oscilloscope, wherein the digital oscilloscope is placed in the control area outside the radio wave darkroom.

[0026] The transceiver waveguide antenna comprises a transmitting waveguide horn antenna 1 and a receiving waveguide probe antenna 6 .

[0027] In this embodiment, the transmitting waveguide horn antenna 1 is installed on the top of the anechoic chamber, emitting a high-power pulse radiation field downward, the transmitting waveguide horn antenna 1 is electrically connected to the first waveguide coupler 2, the first waveguide coupler 2 is connected to the first microwave broadband attenuator 3 through a low-loss RF coaxial cable, and the transmitting waveguide horn antenna 1 is connected to the external HPM effect source through a transmission waveguide. The peak power density monitoring value is connected to the first sampling channel CH1 of the digital oscilloscope 5 through the first microwave detector 4 via the coupling port of the first waveguide coupler 2 connected to the low-loss RF coaxial cable and the first microwave broadband attenuator 3.

[0028] A test bracket 11 is provided on the floor of the radio wave darkroom, and a receiving waveguide probe antenna 6 and an absorption load 10 are installed on the bracket. The receiving waveguide probe antenna 6 is arranged upward and opposite to the transmitting waveguide horn antenna 1. A second waveguide coupler 7 is also installed on the bracket, which is electrically connected to the receiving waveguide probe antenna 6. The second waveguide coupler 7 is connected to the second microwave broadband attenuator 8 through a low-loss radio frequency coaxial cable. The peak power density test value is connected to the second sampling channel CH2 of the digital oscilloscope 5 through the second microwave detector 9 via the coupling port of the second waveguide coupler 7, which is connected to the low-loss radio frequency coaxial cable and the second microwave broadband attenuator 8. The system can directly display the peak power density monitoring value and the measured value, time domain and frequency domain waveforms, peak stability, field uniformity and other parameters of the irradiation point.

[0029] Specifically, the peak power density monitoring value at the transmitting waveguide horn is calculated using the following formula:

[0030]

[0031] In formula (1), S 监测值 Indicates the peak power density monitoring value of the radiation field at the transmitting waveguide horn, in W / cm 2 ;P det1It represents the input power of the first microwave detector, which is obtained by the calibration curve of the CH1 channel detection voltage of the digital oscilloscope and the microwave detector input power, and the unit is W; A1 represents the total attenuation of the corresponding attenuation channel, including the attenuation of the low-loss RF coaxial cable attenuation channel and the attenuation of the first microwave broadband attenuator, and the unit is dB; R represents the far-field test distance, and the unit is cm.

[0032] The peak power density test value at the receiving waveguide probe is calculated using the following formula:

[0033]

[0034] In formula (2), S 测试值 Indicates the peak power density test value of the radiation field at the receiving waveguide probe, in W / cm 2 ;P det2 It represents the input power of the second microwave detector, which is obtained by the calibration curve of the CH2 channel detection voltage of the digital oscilloscope and the microwave detector input power, and the unit is W; A2 represents the total attenuation of the corresponding attenuation channel, including the attenuation of the low-loss RF coaxial cable attenuation channel and the attenuation of the second microwave broadband attenuator, and the unit is dB; A e Indicates the effective area of ​​the receiving antenna, in cm 2 .

[0035] The transmitting waveguide horn antenna 1 transmits a high-power pulse radiation field, and the receiving waveguide probe antenna 6 receives the high-power pulse radiation field, converts the high-power signal into a high-frequency voltage signal, passes through a low-loss RF coaxial cable with attenuation and a microwave broadband attenuator, and then connects to a microwave detector. The narrow pulse signal envelope output by the detection is fed into a digital oscilloscope, and the voltage amplitude and pulse width parameters of the envelope signal after detection are measured by the digital oscilloscope; after comprehensively considering the receiving horn antenna gain, the attenuation of the low-loss RF coaxial cable attenuation channel, the attenuation of the microwave broadband attenuator, and the detection coefficient parameters of the microwave detector, the peak power of the high-power microwave radiation field is obtained; by reading the interval time of a group of pulses on the digital oscilloscope, the repetition frequency of the pulse can be obtained.

[0036] The transmitting waveguide horn antenna 1 has a large power capacity and is suitable for transmitting high-power microwave radiation fields; the receiving waveguide probe antenna 6 also has a large power capacity and a wide beam pattern, which is suitable for measuring narrow-spectrum high-power microwave radiation fields of different frequencies. Since the antenna has good polarization characteristics and a wide beam, different polarization components of the high-power microwave radiation field (usually measuring two components, horizontal polarization and vertical polarization) can be measured by adjusting the polarization direction of the antenna, and the alignment accuracy requirements for the incoming wave direction are relatively low.

[0037] Preferably, the coupling degree between the first and second waveguide couplers is 50 dB. The low-loss RF coaxial cable is used to transmit the microwave pulse signal received by the antenna. The low-loss RF coaxial cable usually adopts a double-shielded coaxial cable or a semi-rigid coaxial cable to reduce the direct coupling effect of the cable under the high-power electromagnetic pulse field. The length of the low-loss RF coaxial cable should be selected from 20m to 50m to ensure that the tester and the oscilloscope can be far enough away from the main beam. The RF loss per meter of the low-loss RF coaxial cable is not more than 1dB. The microwave broadband attenuator should select a suitable attenuation, which can be selected as 20dB, 30dB, etc. as needed, and the frequency range covers the main frequency of the high-power microwave radiation field to be measured. After comprehensively configuring the attenuation of the low-loss RF coaxial cable and the microwave broadband attenuator, when the microwave pulse signal received by the antenna is transmitted to the input end of the microwave detector, the amplitude range of the signal is in the linear working area of ​​the high-speed microwave detector.

[0038] Furthermore, the detection output ends of the first and second microwave detectors are preferably connected to the sampling channels (CH1, CH2) of the digital oscilloscope through a short coaxial cable less than 1 m in length.

[0039] The microwave detector performs envelope detection on the tested microwave pulse signal, and then converts the microwave pulse signal into a voltage detection signal and connects it to the digital oscilloscope for pulse waveform observation and peak measurement. There is a linear response relationship curve between the detection voltage amplitude of the digital oscilloscope and the microwave pulse input peak power. Figure 2 The figure shows the response relationship curve between the detection voltage of the digital oscilloscope and the input power of the microwave detector. In the case of high detection accuracy requirements for traditional peak envelope detectors, the output voltage change lags behind the change of the input signal envelope, that is, the response time cannot meet the measurement requirements; the present application is different from the traditional peak envelope detector, and adopts a semiconductor-based demodulation logarithmic amplifier (integrated microwave detection chip) to realize the peak detection function of the detector. Compared with conventional detectors, it has the advantages of high precision, wide bandwidth, large dynamic range and low temperature coefficient. Among them, the demodulation logarithmic amplifier is a circuit with an instantaneous compressed dynamic input range in which the output voltage and the power of the input signal are in a logarithmic function relationship. The high-speed microwave detector performs envelope detection on the tested microwave pulse signal, and the response time is less than 1 / 3 of the signal pulse width, the maximum tolerable power is not less than +30dBm, the voltage sensitivity is better than 0.3mV / μW, the standing wave ratio is less than 1.5, and the frequency range covers the main frequency of the high-power microwave radiation field to be measured.

[0040] Before testing, the high-speed microwave detector should be calibrated, that is, for the high-power microwave frequency to be measured, the output voltage U of the high-speed microwave detector should be calibrated and measured at different RF input powers P. Since the high-speed microwave detector is a nonlinear semiconductor device, during calibration, the input power should be gradually increased from small to large in the linear working area, and during measurement, it should also be ensured that the input signal is in its linear working area.

[0041] like Figure 3 As shown, the present application further adopts a liftable test bracket, and the bracket structure adopts a non-metallic material with a small dielectric constant to effectively reduce the influence of the structure on the measurement in microwave measurement. The test bracket should be lightweight and movable to facilitate field uniformity measurement. In this embodiment, the receiving waveguide probe antenna 6, the second waveguide coupler 7, and the absorbing load 10 are installed on the lifting rod, so that the test receiving and transmitting distance can be effectively adjusted to meet the needs of power density and field uniformity area size adjustment. Optionally, the lifting bracket includes a transmission mechanism and a driving mechanism, and the transmission mechanism is driven by the driving mechanism; the driving mechanism outputs linear or rotational motion, and the transmission mechanism converts the linear or rotational motion into linear motion of the lifting rod. For example, the driving mechanism is preferably a motor; the transmission mechanism includes a vertically arranged guide rail, a slider is installed on the guide rail, and a structural member is installed on the slider for fixing the receiving waveguide probe antenna 6 and / or the absorbing load 10; the slider is threadedly connected to a lead screw, the output shaft of the motor is connected to the lead screw, the motor rotates to drive the lead screw to rotate, and the rotation of the lead screw can be converted into a linear motion of the slider, thereby driving the slider and the receiving waveguide probe antenna 6 and / or the absorbing load 10 to move up and down along the guide rail. In addition, the test bracket can also realize the lifting function by means of an electric push rod or a cylinder drive.

[0042] by Figure 1 The waveform of a high-power, ultra-short pulse, microwave radiation field oscilloscope measured by the present invention is taken as an example. The carrier frequency of the microwave radiation field is 2.45GHz, and the duty cycle is 7%. After the test system is calibrated and the data is processed, the peak power of the spatial pulse field at the biological sample platform is calculated using formula (1), wherein the high-speed microwave detector detection output voltage is 2802mV, the corresponding detector input power is -5dBm, the loss of the low-loss RF coaxial cable at the test frequency is about 4.96dB, the attenuation of the microwave broadband attenuator is 19.98dB, and the coupling degree of the waveguide coupler is 50.02dB; the probe antenna gain is 7.03dB, and the corresponding effective receiving area is 60.14cm 2 Substituting into formula (2) and calculating, the peak power of the received high-power microwave pulse radiation field is about 10KW, and the peak power density is 166W / cm 2 .

[0043] This application uses field uniformity detection equipment to improve the accuracy and operational efficiency of high-power microwave radiation field uniformity detection. The system can directly display the peak power density monitoring value and measured value, time domain and frequency domain waveforms, peak stability and field uniformity parameters at the irradiation point, providing basic data for dosimetry and biological effect research.

[0044] It should be noted that the implementation of the system of the present application involves data acquisition and processing, device selection and configuration, such as the calculation method of the monitored value and the measured value of the peak power density, the circuit structure of the demodulated logarithmic amplifier, the calibration method of the high-speed microwave detector, and the driving method (such as an electric push rod) used to achieve the lifting of the test bracket, but these contents are mature existing technologies, and their specific implementation methods have been published in various documents before the filing date of this application. Therefore, the present application seeks to protect a system architecture that is independent of the above-mentioned data processing method / circuit structure / calibration method / electromechanical driving principle. Although the implementation of the present application needs to be applied to the above-mentioned data processing method / circuit structure / calibration method / electromechanical driving principle, the implementation of the present application does not rely on any unknown computer software program or method, and is the object of protection of the utility model.

Claims

1. A pulse microwave biological effect experiment radiation field online measurement system, characterized in that: include: The transmitting waveguide horn antenna (1) is electrically connected to a first waveguide coupler (2); the coupling port of the first waveguide coupler (2) is connected to a low-loss cable and then connected to a first sampling channel of a digital oscilloscope (5) via a first microwave broadband attenuator (3) and a first microwave detector (4); the first waveguide coupler (2) is connected to a high-power microwave source via a transmission waveguide; The receiving waveguide probe antenna (6) is electrically connected to the second waveguide coupler (7) and is arranged opposite to the transmitting waveguide horn antenna (1); the coupling port of the second waveguide coupler (7) is connected to a low-loss cable and then connected to a second sampling channel of a digital oscilloscope (5) via a second microwave broadband attenuator (8) and a second microwave detector (9); An absorbing load (10) is arranged on one side of the receiving waveguide probe antenna (6); The test bracket (11) is made of non-metallic material and is used to support the receiving waveguide probe antenna (6) and the absorbing load (10).

2. The pulse microwave biological effect experiment radiation field online measurement system according to claim 1 is characterized in that: The low-loss cable is a double-shielded coaxial cable or a semi-rigid coaxial cable.

3. The pulse microwave biological effect experiment radiation field online measurement system according to claim 1 or 2, characterized in that: The length of the low-loss cable is 20-50m.

4. The pulse microwave biological effect experiment radiation field online measurement system according to claim 3 is characterized in that: The low-loss cable has a radio frequency loss of less than 1 dB per meter.

5. The pulse microwave biological effect experiment radiation field online measurement system according to claim 1 is characterized in that: The first microwave detector (4) and the second microwave detector (9) adopt semiconductor-based demodulation logarithmic amplifiers.

6. The pulse microwave biological effect experiment radiation field online measurement system according to claim 1 is characterized in that: The detection output ends of the first microwave detector (4) and the second microwave detector (9) are connected to the sampling channel of the digital oscilloscope via a coaxial cable with a length of less than 1 m.

7. The pulse microwave biological effect experiment radiation field online measurement system according to claim 1 is characterized in that: The test bracket (11) is a lifting bracket, which is used to adjust the test transmission and reception distance.

8. The pulse microwave biological effect experiment radiation field online measurement system according to claim 7 is characterized in that: The lifting bracket comprises a transmission mechanism and a driving mechanism, a receiving waveguide probe antenna (6) and / or an absorbing load (10) are mounted on the transmission mechanism, and the transmission mechanism and the driving mechanism are connected; the driving mechanism outputs linear or rotational motion, and the transmission mechanism converts the linear or rotational motion into linear motion of the receiving waveguide probe antenna (6) and / or the absorbing load (10).

Images