Electronic sounding instrument and radar detection system based on dual-channel digital frequency modulation

Abstract

The utility model provides a kind of electronic sounding apparatus and radar detection system based on double channel digital frequency modulation, sounding apparatus includes temperature sensor, humidity sensor, baroceptor, measurement conversion unit, transmitter and receiver, data acquisition module is used to receive temperature, humidity and air pressure signal in high altitude, single-chip microcomputer converts sounding signal into square wave signal and is transmitted to transmitter, transmitter sends square wave signal to ground radar, receiver has answering radar inquiry function, receives the answering signal generated by amplitude modulation ranging inquiry pulse sent by ground radar, inquiry pulse modulation is sent to transmitter, and answer pulse is sent back for ground radar reception;The utility model's sounding apparatus avoids the shortcomings of unstable ranging and easy to be disturbed by continuous wave ranging pulse, and cooperates with ground double channel wind finding radar, and the temperature, humidity, pressure, wind speed, wind direction in 30 kilometers from ground to high altitude, square 200 kilometers in air can be accurately detected.

Description

Technical Field

[0001] This utility model relates to the field of upper-air meteorological detection, specifically to an electronic radiosonde and radar detection system based on dual-channel digital frequency modulation. Background Technology

[0002] The most common method for upper-air meteorological detection is to use wind-measuring radar and radiosonde detection systems. During detection, the ground-based wind-measuring radar tracks the radiosonde carried by the radiosonde balloon. The radiosonde, in a free-ascent manner, detects meteorological elements such as temperature, humidity, pressure, wind speed, and wind direction from the Earth's surface to tens of thousands of meters above the ground. The radiosonde processes the detected meteorological elements and transmits them back to the ground-based radar wirelessly. The ground-based radar receives the signal from the radiosonde, amplifies and demodulates it to obtain the meteorological elements in the air, including temperature, humidity, and pressure. Based on the azimuth and elevation angles obtained by the ground-based radar and the slant distance between the radar and the radiosonde in the air, the three-coordinate aerial trajectory of the radiosonde can be obtained, from which the wind speed and wind direction can be calculated.

[0003] Conventional ground-based radars and radiosondes use amplitude modulation (AM) for slant range determination. The ground radar transmits ranging pulses, and the AM-modulated radiosonde responds with a response pulse to complete the ranging. Ground-based radar operates on the L-band frequency band used in international meteorological surveys. AM modulation occupies a wide channel, causing significant interference to meteorological satellite reception and affecting accuracy. Frequency modulation (FM) pulse modulation, with its smaller frequency offset and less interference, is the future direction. Since radiosondes are disposable consumables, high performance, high accuracy, and low cost are key development directions for radiosondes operating at high altitudes and low temperatures. Because wind-measuring radars and radiosondes need to work together, their systems and interfaces must be identical. Utility Model Content

[0004] The purpose of this invention is to address the aforementioned problems and shortcomings related to interference by proposing a dual-channel digital frequency modulation electronic radiosonde and radar detection system. By designing the electronic radiosonde based on dual channels, the radiosonde receives interrogation and ranging pulses at a carrier frequency of 403MHz from a ground-based radar. The radiosonde modulates these pulses onto a carrier frequency of 1680MHz and sends back a response pulse. The radiosonde code directly modulates the radio frequency (L-band) at 1680MHz, reducing the bandwidth to approximately 1MHz. Ranging still uses amplitude modulation pulse ranging (P-band 403MHz) to avoid the instability and susceptibility to interference associated with continuous wave ranging pulses. Due to the dual channels of the electronic radiosonde, a dual-channel radar is employed to achieve collaborative operation. The dual-channel radar uses dual-frequency pulse code modulation with separate transmit and receive signals. This invention's radiosonde and ground-based dual-channel wind-measuring radar work together to accurately detect temperature, humidity, pressure, wind speed, and wind direction from the ground to an altitude of 30 kilometers, within a radius of 200 kilometers.

[0005] To achieve the above objectives, the radiosonde technology adopted in this utility model is an electronic radiosonde and radar detection system based on dual-channel digital frequency modulation. The radiosonde includes a temperature sensor, a humidity sensor, a barometric pressure sensor, a measurement conversion unit, a transmitter, and a receiver. The measurement conversion unit includes a data acquisition module and a microcontroller. The temperature sensor, humidity sensor, and barometric pressure sensor are respectively connected to the data acquisition module. The data acquisition module is used to receive temperature, humidity, and barometric pressure signals at high altitudes. The microcontroller is connected to the data acquisition module and the transmitter and is used to convert the radiosonde signals into square wave signals and transmit them to the transmitter.

[0006] The transmitter includes a radiosonde modulation circuit and a ranging modulation circuit, which are used to modulate the radiosonde and measure the distance, respectively. The transmitter then transmits the square wave signal to the ground radar through the transmitter antenna.

[0007] The receiver has a radar interrogation response function, which is used to receive the response signal generated by the amplitude modulation ranging interrogation pulse with a carrier frequency of 403MHz sent by the ground radar. The interrogation pulse is modulated to the transmitter with a carrier frequency of 1680MHz and the response pulse is sent back for the ground radar to receive.

[0008] Furthermore, the radar is a dual-channel frequency-modulated wind-measuring radar, consisting of 6 subsystems and 30 units. The receiving subsystem comprises 6.5 units, including a half-unit quad-feed parabolic antenna in the antenna assembly, a beam selection network, a preamplifier, a high-frequency joint, a high-frequency combination, an intermediate frequency unit, and a decoding self-test unit. The transmitting subsystem comprises 6.5 units, including a UPS, a transmitting power supply, a low-voltage power supply, an RF oscillator, a modulation drive, a power amplifier, and a half-unit dipole antenna in the antenna assembly. The antenna control subsystem comprises 10 units, including antenna control, azimuth conversion, azimuth driver, elevation conversion, elevation drive, azimuth synchronizer, azimuth drive motor, elevation synchronizer, elevation drive motor, and a control box. The terminal processing subsystem comprises 3 units, including a terminal interface, a terminal processing microcomputer, and a monitor. The display subsystem comprises 3 units, including a display control, a display, and a camera. The ranging subsystem consists of a ranging unit.

[0009] The antenna unit consists of a 1.8-meter parabolic metal antenna and a single 403MHz dipole antenna, forming a dual antenna. Under the control of the trigger pulse output from the ranging subsystem, the transmitting subsystem transmits a high-frequency interrogation pulse signal with amplitude modulation through the 403MHz dipole antenna into the air. This causes the radiosonde to generate a response signal related to the trigger pulse output from the ranging subsystem. The amplitude-modulated response signal is modulated onto a 31.25KHz subcarrier and then modulated to a transmitter frequency of 1680MHz, which is then transmitted into the air by the radiosonde antenna.

[0010] The ground radar receiver operates at 1680MHz and is used to receive temperature, humidity, and air pressure data from the radiosonde, as well as the radiosonde's response pulses.

[0011] Furthermore, the data acquisition module of the measurement conversion unit adopts the AD7705BRV module.

[0012] Furthermore, the model number of the measurement conversion unit is PIC16F726.

[0013] Furthermore, the transmitter's radiosonde modulation circuit consists of R2, RP2, R4, R6 and an ultra-high frequency transistor V1. The digital signals 0 and 1 of the radiosonde are divided by resistors R2, RP2, R4 and R6 and then applied to the base of the ultra-high frequency transistor V1, changing the bias voltage Vb of the base of V1.

[0014] The ranging modulation circuit of the transmitter consists of resistors R1, RP3, R5, R6 and ultra-high frequency transistor V1. The level signals 0 and 1 generated by ranging are divided by resistors R1, RP3, R5 and R6 and then applied to the base of ultra-high frequency transistor V1, changing the bias voltage Vb of the base of V1.

[0015] Furthermore, the temperature sensor employs a beaded thermistor circuit.

[0016] Furthermore, the humidity sensor employs a polymer thin-film humidity-sensitive capacitor.

[0017] Furthermore, the pressure sensor employs a silicon piezoresistive pressure sensor.

[0018] Furthermore, temperature, humidity, and air pressure sensors are connected to the corresponding interfaces of the measurement conversion unit. The microcontroller of the measurement conversion unit receives the measured signals in real time through a multiplexer, converts the collected radiosonde signals into 31.25KHz square wave signals, and transmits them to the ground radar via a transmitter for 0.2 seconds. For the remaining 0.8 seconds, the transmitter is in a radiosonde signal rest state, transmitting only carrier signals. The receiver receives the transmission pulses sent by the ground radar dipole antenna and generates response pulses to control the transmitter to send a reply signal.

[0019] Furthermore, the measurement conversion unit also includes logic gate circuits, which are connected to the data acquisition module, the microcontroller, and the transmitter. The data acquisition module converts the measured values ​​of temperature, humidity, and air pressure into hexadecimal numbers and transmits them to the logic gate circuits at a baud rate of 1.2Kbps via the microcontroller pins. At the same time, the microcontroller outputs a subcarrier and ranging control signal at a baud rate of 31.25KHz. The logic gate circuits are used to modulate the radiosonde code onto the subcarrier at a baud rate of 1.2Kbps and transmit it to the transmitter.

[0020] The beneficial effects of this utility model are:

[0021] This invention employs a sensor and a dual-channel frequency modulation circuit for upper-air meteorological detection. The radiosonde encodes and modulates the collected temperature, humidity, and pressure meteorological information, which is then transmitted via an antenna to a ground-based dual-channel frequency modulation wind radar for reception and collaborative operation. This allows for accurate detection of atmospheric parameters such as temperature, humidity, air pressure, wind speed, and wind direction within a radius of 35 km to 200 km from the ground, providing accurate data for meteorological monitoring systems. It does not interfere with satellite cloud image reception and communication. When applied to upper-air meteorological detection, it has the advantages of small size, light weight, automated signal and reception, wide communication channels, strong anti-interference ability, and stable reliability. Attached Figure Description

[0022] Figure 1 This is a block diagram of the electrical principle of the dual-channel radiosonde of this utility model.

[0023] Figure 2 This is a block diagram of the electrical principle of the dual-channel wind-measuring radar of this utility model.

[0024] Figure 3 This is the electrical schematic diagram of the transmitter of the dual-channel radiosonde of this utility model.

[0025] Figure 4 This is the electrical schematic diagram of the super-regenerative receiver of the dual-channel radiosonde of this utility model.

[0026] Figure 5 This is the circuit diagram of the pulse width adjustment circuit of the receiver of the dual-channel radiosonde of this utility model.

[0027] Figure 6 This is the circuit diagram of the receiver ranging signal shut-off circuit of the dual-channel radiosonde of this utility model.

[0028] Figure 7 This is a simplified linearized electrical schematic diagram of the temperature sensor for the dual-channel radiosonde of this utility model.

[0029] Figure 8 This is a block diagram illustrating the electrical principle of the humidity sensor in the dual-channel radiosonde of this invention.

[0030] Figure 9 This is a schematic diagram of the Wheatstone bridge circuit for the air pressure sensor of the dual-channel radiosonde of this utility model.

[0031] Figure 10 This is a schematic diagram of the electrical principle of the barometric pressure sensor measurement in the dual-channel radiosonde of this utility model.

[0032] Figure 11 This is the overall electrical schematic diagram of the measurement conversion unit of the dual-channel radiosonde of this utility model.

[0033] Figure 12This is the overall electrical schematic diagram of the transmitter of the dual-channel radiosonde of this utility model.

[0034] Figure 13 This is the overall electrical schematic diagram of the receiver of the dual-channel radiosonde of this utility model. Detailed Implementation

[0035] To make the contents of this utility model clearer, the embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.

[0036] This embodiment provides an electronic radiosonde and radar detection system based on dual-channel digital frequency modulation, such as... Figure 1 , Figure 11 , Figure 12 and Figure 13 As shown, the radiosonde in this embodiment includes a temperature sensor, a humidity sensor, a barometric pressure sensor, a measurement conversion unit, a transmitter, a receiver, and a battery. The temperature sensor, humidity sensor, and barometric pressure sensor are used to measure the temperature, humidity, and barometric pressure signals at high altitudes, respectively. The measurement conversion unit includes a data acquisition module and a microcontroller. The temperature sensor, humidity sensor, and barometric pressure sensor are connected to the data acquisition module ADT7705BRV, which receives the temperature, humidity, and barometric pressure signals. The data acquisition module is connected to the microcontroller, and the temperature, humidity, and barometric pressure signals from the data acquisition module are transmitted to the subcarrier-modulated microcontroller, which is a PIC16F726. The receiver is used to connect to a ground radar and receive the interrogation ranging pulses generated by the ground radar. The receiver and microcontroller are connected. The response signal generated by the receiver is sent to the microcontroller. The transmitter has a measurement conversion unit microcontroller interface, which is used to connect to the microcontroller of the measurement conversion unit. The microcontroller modulates and amplifies the temperature, humidity, air pressure and response signals before sending them to the transmitter. The microcontroller is also used to encode the radiosonde signal into a 31.25KHz square wave signal. The radiosonde signal is a stream of temperature, humidity and air pressure signals, which is transmitted within 0.2 seconds. The remaining 0.8 seconds is the radiosonde signal pause time. During this time, the transmitter only transmits the carrier signal, which is tracked by the ground wind radar through the antenna. The azimuth and elevation angles of the ground radar are used to calculate the slant distance from the radar to the radiosonde. From this, the three coordinates of the radiosonde and the wind direction, wind speed and the received temperature, humidity and pressure meteorological information are measured.

[0037] The overall electrical schematic diagram of the measurement conversion unit of the dual-channel radiosonde is as follows: Figure 11As shown, the measurement conversion unit in this embodiment includes a data acquisition module D1, a microcontroller D2, a multiplexer, and logic gate circuits. The microcontroller D2 is connected to the data acquisition module D1 and the transmitter, and is used to convert temperature, humidity, and air pressure signal streams into square wave signals and transmit them to the transmitter input. The multiplexer includes D5A, D5B, and D5C; the microcontroller of the measurement conversion unit receives the measured signals in real time through the multiplexer. The logic gate circuits are connected to the data acquisition module, the microcontroller, and the transmitter. The logic gate circuits include NAND gates D8A, D8B, D8C, and D8D. The data acquisition module converts the measured values ​​of temperature, humidity, and air pressure into hexadecimal numbers, which are then transmitted to the logic gate circuit at a baud rate of 1.2Kbps via the microcontroller pin. Simultaneously, the microcontroller outputs a 31.25KHz subcarrier and a ranging control signal. The logic gate circuit is used to modulate the radiosonde code onto the 31.25KHz subcarrier at a baud rate of 1.2Kbps and transmit it to the transmitter. The ranging control signal is used to disable the receiver's pulse width modulation circuit, ensuring that the receiver has no ranging signal output, thus guaranteeing the purity of the radiosonde code modulation, preventing interference, and ensuring that the receiver has no ranging signal and that the ranging signal is output to the transmitter.

[0038] The schematic diagram of the dual-channel radiosonde transmitter is as follows: Figure 3 As shown, the overall schematic diagram of the dual-channel radiosonde transmitter is as follows: Figure 12 As shown, the transmitter's carrier wave consists of an ultra-high frequency transistor V13DA5108, a high-Q microwave line, a fine-tunable capacitor C6, a whip antenna E1, through-core capacitors C7 and C8, and a ground network. RP1, R3, R6, and R7 are bias resistors for the ultra-high frequency transistor V1. The modulation circuit consists of R1, R2, R4, R5, RP1, RP2, and R6, and N1 is the transmitter's power supply component. The transmitter module uses a 3DA5108 integrated power amplifier to frequency-modulate the amplitude modulation subcarrier information signal to a 1680MHz carrier wave for transmission to ground radar.

[0039] By adjusting RP1, the base bias voltage of the ultra-high frequency transistor V1 is changed, allowing the transmitter to have a stable frequency output. Then, capacitor C6 is adjusted to ensure the transmitter's carrier frequency is within the required range. C6 is a variable capacitor; its capacitance is changed by adjusting the position of the copper screw. Rotating the screw clockwise increases the capacitance and decreases the frequency; rotating the screw counterclockwise decreases the capacitance and increases the frequency. Capacitors C7, C8, and C5 are used for circuit filtering.

[0040] Radiosonde code is a standardized data encoding format whose main function is to efficiently, accurately, and systematically transmit and exchange meteorological data collected by a radiosonde during its ascent. In this embodiment, the radiosonde code modulation circuit of the transmitter consists of resistors R2, RP2, R4, R6, and an ultra-high frequency transistor (UHF) V1. This circuit modulates the radiosonde code, changing its oscillation frequency and modulating the digital information onto the carrier frequency. Its working principle is as follows: the digital signals "0" and "1" of the radiosonde code are divided by resistors R2, RP2, R4, and R6 and then applied to the base of the UHF transistor V1, changing the bias voltage Vb of the V1 base. When the radiosonde code is a digital signal "0", the base voltage of the UHF transistor V1 is Vb1; when the radiosonde code is a digital signal "1", the base voltage of the UHF transistor V1 is Vb2. The corresponding UHF oscillation frequency generated by Vb1 is f1, and the corresponding UHF oscillation frequency generated by Vb2 is f2.

[0041] The ranging modulation circuit of the transmitter in this embodiment consists of resistors R1, RP3, R5, and R6, and an ultra-high frequency transistor V1. This circuit modulates the ranging signal, changing its generated oscillation frequency to modulate the digital information onto the carrier frequency. Its working principle is as follows: the ranging level signals "0" and "1" are divided by resistors R1, RP3, R5, and R6 and then applied to the base of the ultra-high frequency transistor V1, changing the bias voltage Vb of V1's base. When the ranging level signal is "0", the base voltage of the ultra-high frequency transistor V1 is Vb1; when the sounding code is a digital signal "1", the base voltage of the ultra-high frequency transistor V1 is Vb2. The ultra-high frequency oscillation frequency generated by Vb1 is f1, and the ultra-high frequency oscillation frequency generated by Vb2 is f2.

[0042] In this embodiment, the radiosonde modulation circuit and the ranging modulation circuit employ time-division modulation, which is implemented by the measurement conversion unit. The transmitter is connected to the microcontroller of the measurement conversion unit. The microcontroller unifies the temperature, humidity, and air pressure signal streams into a 31.25kHz square wave signal. The transmitter transmits the square wave signal within 0.2 seconds, with the remaining 0.8 seconds being a pause time for the square wave signal. During this pause, the transmitter only transmits the carrier signal. The ground receiving equipment performs further processing based on the signal transmitted by the transmitter. The processing steps all involve existing, widely used, and mature technologies. First, the azimuth and elevation angles of the radiosonde's spatial location are determined. The altitude of the radiosonde's spatial location is obtained using the air pressure, temperature, and humidity measured by the radiosonde, thus obtaining the three-dimensional coordinates of the radiosonde's spatial location to determine the wind direction and speed.

[0043] The receiver, also known as a transponder, is shown in the overall electrical schematic diagram of a dual-channel radiosonde receiver. Figure 13As shown, the receiver in this embodiment mainly consists of a super-regenerative receiver, a pulse width modulation circuit, and a ranging signal shutdown circuit. The circuit diagram of the super-regenerative receiver of the dual-channel radiosonde is shown below. Figure 4 As shown, the super-regenerative receiver consists of an ultra-high frequency receiver and a frequency-quenching circuit.

[0044] The UHF receiver in this embodiment consists of an UHF transistor 2V1, a microstrip line, 2R16, 2C1, 2C2, 2C3, and an antenna, wherein the microstrip line exhibits inductive impedance. When 2R16 moves along the microstrip line towards 2V1, the inductance decreases, and the UHF receiver frequency increases; conversely, when 2R16 moves along the microstrip line in the opposite direction towards V1, the inductance increases, and the UHF receiver frequency decreases. Therefore, by adjusting the position of 2R16, the receiving frequency of the UHF receiver can be adjusted.

[0045] To better receive interrogation signals transmitted by ground radar transmitters, the UHF transistor 2V1 operates in a super-regenerative state. This means that the UHF transistor is in an intermittent oscillation state, switching between starting and stopping oscillation, through the bias circuit and frequency quenching circuit of 2V1. The pulses generated in the super-regenerative state, as well as the interrogation signals received by the transponder, are fed to the pulse width modulation circuit via coupling capacitor 2C7. Inductors 2L1, 2L2, and 2L3 isolate the UHF oscillation circuit from other circuits, ensuring stable UHF oscillation.

[0046] The frequency quenching circuit consists of a set of Schmitt trigger circuits 2D1D, 2R7, and 2C8 from integrated circuit 2D1, with a frequency of approximately 1MHz. Through the RC discharge circuit, its positive half-cycle allows the intermittent oscillator to approach the start-up voltage of the UHF receiver more quickly, thereby improving the sensitivity of the UHF receiver. The bias circuit for 2V1, composed of 2R1, 2R2, 2R3, 2R4, 2C5, 2C4, 2R9, and 2RP1, is used to adjust the current of 2V1.

[0047] The circuit diagram of the pulse width modulation circuit of the dual-channel radiosonde is as follows: Figure 5 As shown, the pulse width adjustment circuit of the radiosonde in this embodiment consists of integrated circuits 2D1A, 2D1B, 2D1C and resistors and capacitors, and is used to adjust the width of the ranging signal so that its output width is between 5μs and 9μs.

[0048] Even without a ranging signal, the transponder itself generates a self-excited pulse signal. This self-excited pulse signal is adjusted to between 5μs and 9μs by the pulse width adjustment circuit before being output to the transmitter. When the measurement conversion unit sends the radiosonde code, it also outputs a control signal to shut down the ranging signal shutdown circuit. Specifically, the "ranging control signal" generates a high level, thereby turning off the pulse width adjustment circuit and ensuring that the radiosonde code and the ranging signal do not interfere with each other.

[0049] The circuit diagram of the receiver ranging signal shut-off circuit of the dual-channel radiosonde is as follows: Figure 6 As shown, the receiver ranging signal shutdown circuit in this embodiment mainly consists of an integrated circuit, resistors, capacitors, and diodes, and is used to improve the driving capability of the "ranging control signal" output by the measurement conversion circuit.

[0050] Simultaneously with the output of the radiosonde code from the measurement conversion circuit, a ranging control signal is also output to disable the pulse width modulation circuit, ensuring that the transponder outputs no self-excitation signal or ranging signal, thus guaranteeing the purity of the radiosonde modulation. At the same time as the radiosonde output from the measurement conversion circuit ends, the level of the ranging control signal is switched, enabling the pulse width modulation circuit to output the self-excitation signal and ranging signal generated by the transponder to the transmitter.

[0051] In this embodiment, temperature, air pressure, and humidity are measured using a thermistor temperature sensor, a silicon piezoresistive air pressure sensor, and a polymer thin-film capacitive humidity sensor, respectively. Their detection accuracy, stability, and physical performance fully meet the application requirements and are at a leading level in China. The sensor's measurement circuit design employs a high-precision, high-speed integrated chip circuit, which significantly reduces measurement errors, improves measurement performance, and makes the sensor smaller, lower in cost, and easier to use.

[0052] The temperature sensor in this embodiment uses a negative temperature coefficient thermistor, and its output parameter is in the form of resistance. Resistance measurement is usually indirect, that is, the resistance value is derived by measuring other electrical quantities such as voltage and frequency.

[0053] Voltage and frequency are two relatively easy forms of electrical quantity to measure, and both can be measured using relatively simple circuits. Voltage can be measured using an A / D converter chip; frequency can also be measured using a simple pulse counter circuit or a dedicated chip.

[0054] Because the sensor has a large temperature measurement range and high accuracy and resolution, voltage measurement requires a sufficiently high bit depth of the A / D conversion chip and sufficiently stable peripheral circuitry, which complicates the circuit structure of the measurement section and increases costs. For frequency measurement using a simple pulse counting circuit, it is easy to achieve a measurement resolution of 0.1Hz or higher. For systems with frequency variations of several kHz, the resolution is quite high, and the frequency generation circuit has a simple structure and low cost.

[0055] After comparison, this embodiment determines that the resistance of the temperature sensor is measured by measuring the frequency.

[0056] Temperature measurement involves converting the resistance change of a temperature sensor into a voltage change using a resistance-voltage conversion circuit. This voltage change is then converted by an A / D converter within the measurement circuit to obtain the resistance value of the temperature sensor and its corresponding temperature value.

[0057] The simplified linearized circuit diagram of the temperature sensor of the dual-channel radiosonde is shown below. Figure 7 As shown, the relationship between the resistance of the temperature sensor and temperature in this embodiment is nonlinear and exponential, with the resistance changing by approximately 10 times across the entire temperature measurement range. Without limitation, the voltage change corresponding to the resistance would also be approximately 10 times, making it difficult to measure voltage at both high and low ends, especially prone to causing measurement errors at high frequencies. Therefore, a simple linearization process was implemented for the resistance change of the temperature sensor: first, a resistor is connected in parallel, then another resistor is connected in series, ensuring that the total equivalent resistance changes within approximately the same order of magnitude across the temperature measurement range, thus reducing measurement errors.

[0058] After adding a parallel resistor, the effect of the high-end resistance of the temperature sensor on the changing circuit will be significantly reduced, which is not conducive to maintaining a certain resolution when measuring temperature at this stage. Therefore, the parallel resistor should not be too small, and can be approximately 1 / 2 to 1 times the maximum resistance of the sensor within the temperature measurement range.

[0059] When a temperature sensor operates, the current flowing through it generates heat. This heat, in turn, causes a change in the sensor's resistance, leading to inaccurate temperature measurements. To negate the heating effect of the current flowing through the sensor, the power loss caused by the current passing through the sensor must be less than 0.1 milliwatts. Therefore, there are specific requirements for the resistance values ​​of the series and parallel resistors mentioned above.

[0060] Let the resistance of the temperature sensor be R, the parallel resistor be Rb, the series resistor be Rc, and the voltage across the linearization circuit be U. Then the current IR flowing through the temperature sensor is:

[0061]

[0062] The power loss PR on the temperature sensor is:

[0063]

[0064] According to the concept of extreme values, for the sensor resistance R, when the derivative of the denominator is 0, P R It will reach its maximum value when R satisfies

[0065]

[0066] At that time, P R The maximum value P is obtained Rmax for:

[0067]

[0068] By selecting appropriate series and parallel resistor values, the maximum power loss P of the temperature sensor can be minimized. RmaxIf the power loss is less than 0.1 milliwatts, then the power loss of the temperature sensor will not exceed 0.1 milliwatts throughout the entire temperature range. Through the above temperature measurement method, the radiosonde in this embodiment can accurately collect the temperature.

[0069] Specifically, the resistance-to-voltage conversion circuit for temperature measurement can be implemented using an A / D conversion circuit.

[0070] This embodiment provides a more preferred method for measuring temperature to correct the temperature measurement. During the measurement process, the environmental changes experienced by the sensor (especially changes in temperature, air pressure, and humidity) will cause characteristic drift of the measurement conversion circuit. At the same time, the conversion circuit itself will also generate certain characteristic drift during the power-on operation. These characteristic drifts cause the output characteristics of the conversion circuit to fail to accurately reflect the resistance change of the temperature sensor. That is, there is no one-to-one correspondence between voltage and resistance, which causes the final temperature measurement result to be biased.

[0071] To correct the impact of the aforementioned characteristic drift on the measurement results, a standard signal variation is introduced: a resistor with a stable resistance or a known resistance variation pattern is introduced at the corresponding position of the temperature sensor in the conversion circuit. The drift generated when this resistor is connected to the circuit is the standard. The variation in the standard can be considered as being caused by the characteristic drift of the conversion circuit. By comparing the drift of the measured voltage corresponding to the temperature sensor with the drift of the standard voltage of the same value, the unknown drift in the measured voltage can be eliminated.

[0072] Because the resistance of a temperature sensor has a range of variation, standard voltage drift values ​​must be obtained for different resistance values ​​to eliminate the influence of voltage drift. Voltage drift is influenced by numerous factors, and these factors interact with each other. Therefore, finding a clear formula to express the pattern of voltage drift is almost impossible. In practical applications, the drift values ​​at different frequencies can be obtained through comparison. Experiments show that, for the same oscillator, under the same changing conditions, the drift at different frequencies corresponds to approximately a linear relationship with the frequency.

[0073] Because the change is linear, two standards, high and low, are introduced into the circuit, which means two standard resistors are required. These standard resistors and the temperature sensor are connected to the circuit via an analog switch, ensuring that only one resistor is connected at any given time, thus enabling the output of either the standard value or the measured value.

[0074] The humidity sensor in this embodiment uses a polymer thin-film humidity-sensitive capacitor, and the output parameter is in the form of capacitance. The measurement of capacitance, like the measurement of resistance, is usually indirect, that is, the capacitance value is derived by measuring other electrical quantities such as voltage, frequency, or time.

[0075] Humidity measurement involves converting the capacitance change of the humidity sensor into a frequency change using a capacitance-to-frequency conversion circuit. The frequency is then measured by a frequency measurement circuit within a dedicated integrated chip, and the capacitance value of the humidity sensor and its corresponding humidity value are obtained based on the frequency measurement results.

[0076] The circuit diagram of the humidity sensor measurement principle of the dual-channel radiosonde is as follows: Figure 8 As shown, in this embodiment, humidity is measured by frequency measurement, which is the same as temperature measurement. Therefore, the conversion circuit for humidity measurement can also be implemented by an RC multivibrator composed of a Schmitt trigger.

[0077] In an RC multivibrator, the oscillator frequency is calculated using the formula... (where a is a constant related to the electrical parameters of the Schmitt trigger). For frequency, the role of capacitor and resistor is the same. Therefore, the discussion on RC multivibrators and frequency measurement in 'Temperature Measurement Method Design' is also applicable to humidity measurement.

[0078] The capacitance of a humidity sensor changes approximately linearly with relative humidity. The humidity sensor can be directly connected to the conversion circuit without the need for an additional linearization circuit like that for a temperature sensor, which simplifies the subsequent processing.

[0079] Humidity sensors go through a process of absorbing and releasing moisture when sensing humidity, which affects the humidity around the sensor. Therefore, it is important to ensure ventilation when taking measurements to ensure that the sensor measures the true ambient humidity.

[0080] In this embodiment, a silicon pressure sensor is used, and the output parameters are in the form of a bridge circuit. The measurement of the pressure sensor is actually converted into a bridge circuit measurement.

[0081] Barometric pressure is measured by converting the resistance change of the barometric pressure sensor into a voltage change through a resistance-to-digital converter. After frequency measurement using a dedicated A / D chip, the voltage of the barometric pressure sensor and its corresponding barometric pressure value are obtained based on the frequency measurement results.

[0082] The Wheatstone bridge circuit diagram of the barometric pressure sensor in a dual-channel radiosonde is shown below. Figure 9 As shown, the principle of air pressure measurement and humidity measurement in this embodiment is the same, so the measurement method is also basically the same. The conversion circuit for air pressure measurement is also implemented by an A / D conversion circuit.

[0083] Since the methods for measuring air pressure and temperature are basically the same, the measurement conversion circuits are also the same. Therefore, the air pressure measurement circuit and the temperature measurement circuit can be integrated and designed into a unified measurement circuit.

[0084] Figure 9The output Vo of the bridge is the differential voltage between Vo+ and Vo-. When using a sensor, the resistance of one or more resistors will change depending on the parameter being measured. This change in resistance will cause a change in the output voltage. Equation 1 gives the output voltage Vo, which is a function of the excitation voltage and all the resistances of the bridge.

[0085] Formula 1: Vo=Ve(R2 / (R1+R2)-R3 / (R3+R4))

[0086] Equation 1 appears complex, but it can be simplified for most bridge applications. When Vo+ and Vo- are equal to half of Ve, the bridge output is highly sensitive to changes in resistance. Using the same nominal value R for all four resistors greatly simplifies the above formula. The resistance change caused by the measurement is represented by the increment of R, or dR. A resistor with a dR term is called an "active" resistor. In the following four cases, all resistors have the same nominal value R, and one, two, or four resistors are active resistors or resistors with a dR term. When deriving these formulas, dR is assumed to be positive. If the actual resistance decreases, it is represented by -dR. In the following special cases, all active resistors have the same dR value.

[0087] The electrical schematic diagram of the barometric pressure sensor measurement circuit of the dual-channel radiosonde is as follows: Figure 10 As shown, since the air pressure measurement in this embodiment is based on the same principle as the temperature measurement, the correction method for air pressure measurement is also the same as that for temperature measurement – ​​introducing a standard signal resistor.

[0088] Similar to temperature correction, the standard frequency correction method only corrects for errors in the measurement circuit caused by various factors. The resistance changes of the barometric pressure sensor itself due to environmental parameters also contribute to pressure measurement errors, especially temperature, which has a significant impact. The temperature characteristics of a barometric pressure sensor are primarily affected by changes in the component's geometric dimensions caused by the coefficient of thermal expansion. Since the influence of the electrical parameters of various parts of the barometric pressure sensor on the resistance value is not easily expressed accurately with formulas, it is also very difficult to explicitly state the change in sensor resistance with temperature using theoretical formulas. A simpler method is to conduct temperature experiments on the sensor to find an empirical formula or reference table between the temperature coefficient of the barometric pressure sensor and temperature, and then incorporate temperature correction during the pressure conversion process.

[0089] In this embodiment, the AD7705BRV data acquisition module of the measurement conversion circuit converts the sensor measurements into hexadecimal numbers, which are then output to the logic gate circuit at a baud rate of 1.2kbps by the PIC16F726-ISS microcontroller connected to the transmitter. Simultaneously, the microcontroller outputs a 31.25kHz subcarrier and ranging control signal. After processing by the logic gate circuit, the sounding code is modulated onto the 31.25kHz subcarrier at a baud rate of 1.2kbps and transmitted to the transmitter.

[0090] In other embodiments, a wind-measuring radar based on a dual-channel digital frequency modulation (DFFM) electronic radiosonde and radar detection system is also provided. Specifically, the wind-measuring radar is a dual-channel DFFM wind-measuring radar. For example... Figure 2 As shown, the dual-channel wind-measuring radar in this embodiment consists of 6 subsystems, divided into 30 units. The receiving subsystem comprises a half-unit quad-feed parabolic antenna from the antenna assembly, a beam selection network, a preamplifier, a high-frequency joint, a high-frequency combination unit, an intermediate frequency unit, and a decoding self-test unit, totaling 6.5 units. The transmitting subsystem comprises a UPS, a transmitting power supply, a low-voltage power supply, an RF oscillator, a modulation drive, a power amplifier, and a half-unit dipole antenna from the antenna assembly, totaling 6.5 units. The antenna control subsystem comprises antenna control, azimuth transformation, azimuth driver, elevation transformation, elevation drive, azimuth synchronizer, azimuth drive motor, elevation synchronizer, elevation drive motor, and a control box, totaling 10 units. The terminal processing subsystem comprises a terminal interface, a terminal processing microcomputer, and a monitor, totaling 3 units. The display subsystem comprises display control, a display, and a camera, totaling 3 units. The ranging subsystem comprises a ranging unit.

[0091] The antenna unit consists of a 1.8-meter parabolic metal antenna and a single 403MHz dipole antenna, forming a dual-antenna configuration. The ground radar employs a four-feed parabolic antenna. Specifically, the parabolic antenna feed utilizes existing four-feed single-channel single-pulse technology to receive four sets of signals (up, down, left, and right). It employs a proprietary technology—a sum-difference loop component called "Secondary Wind Measurement Radar," patent number ZL200710019436.5—to obtain the sum, difference, and error signals of the up, down, left, and right signals. The error signal is used to track the radiosonde. The parabolic antenna feed frequency is 1680MHz. Signals from the radiosonde are extracted to obtain azimuth and elevation angle values. The time difference between the ranging interrogation pulse and the radiosonde's response pulse, along with the radio wave velocity, are used to determine the radiosonde's position and the ground radar's slant range. This eliminates the drawback of poor tracking accuracy caused by large sidelobes when using four sets of parabolic antennas to extract error signals.

[0092] Under the control of the trigger pulse output by the ranging subsystem, the transmitting subsystem transmits a high-frequency interrogation pulse signal with a certain power through a 403MHz dipole antenna to interrogate the airborne radiosonde. This causes the radiosonde to generate a response signal related to the trigger pulse output by the ranging subsystem. The amplitude modulated response signal is modulated to 1680MHz on a 31.25KHz subcarrier and transmitted to the airborne radar for reception.

[0093] The radar receiving subsystem operates at 1680MHz and is used to receive temperature, humidity, and pressure data signals from the airborne radiosonde, as well as the radiosonde's response pulses. The radar acquires the three-coordinate position of the airborne radiosonde and meteorological information such as temperature, humidity, pressure, wind speed, and wind direction in the air. In this embodiment, the radiosonde and radar of the dual-channel digital electronic radiosonde and radar detection system work together to acquire meteorological information such as temperature, humidity, pressure, wind speed, and wind direction within a radius of 200 kilometers from the ground to a height of 30 kilometers.

[0094] This embodiment overcomes the drawbacks of amplitude modulation (AM) systems, such as large bandwidth usage and significant interference in the L-band meteorological channel. By designing the electronic radiosonde based on a dual-channel architecture, the radiofrequency (L-band) 1680MHz is directly modulated by the radiosonde code, reducing the bandwidth to approximately 1MHz. Ranging still employs AM pulse ranging (P-band 403MHz) to avoid the instability and susceptibility to interference associated with continuous wave ranging pulses. Furthermore, the dual-channel electronic radiosonde also utilizes a dual-channel radar for collaborative operation, with the dual-channel radar employing dual-frequency pulse code modulation and separate transmission and reception.

[0095] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications are also within the protection scope of this application.

Claims

1. An electronic radiosonde and radar detection system based on dual-channel digital frequency modulation, characterized in that, The radiosonde includes a temperature sensor, a humidity sensor, a barometric pressure sensor, a measurement conversion unit, a transmitter, and a receiver. The measurement conversion unit includes a data acquisition module and a microcontroller. The temperature sensor, humidity sensor, and barometric pressure sensor are connected to the data acquisition module, which is used to receive temperature, humidity, and barometric pressure signals from the upper atmosphere. The microcontroller is connected to the data acquisition module and the transmitter and is used to convert the radiosonde signals into square wave signals and transmit them to the transmitter. The transmitter includes a radiosonde modulation circuit and a ranging modulation circuit, which are used to modulate the radiosonde and measure the distance, respectively. The transmitter then transmits the square wave signal to the ground radar through the transmitter antenna. The receiver has a radar interrogation response function, which is used to receive the response signal generated by the amplitude modulation ranging interrogation pulse with a carrier frequency of 403MHz sent by the ground radar. The interrogation pulse is modulated to the transmitter with a carrier frequency of 1680MHz and the response pulse is sent back for the ground radar to receive.

2. The electronic radiosonde and radar detection system based on dual-channel digital frequency modulation according to claim 1, characterized in that, The radar is a dual-channel frequency-modulated wind-measuring radar, consisting of 6 subsystems and 30 units. The receiving subsystem comprises 6.5 units: a half-unit quad-feed parabolic antenna from the antenna assembly, a beam selection network, a preamplifier, a high-frequency joint, a high-frequency combination unit, an intermediate frequency unit, and a decoding self-test unit. The transmitting subsystem comprises 6.5 units: a UPS, a transmitting power supply, a low-voltage power supply, an RF oscillator, a modulation drive, a power amplifier, and a half-unit dipole antenna from the antenna assembly. The antenna control subsystem comprises 10 units: antenna control, azimuth conversion, azimuth driver, elevation conversion, elevation drive, azimuth synchronizer, azimuth drive motor, elevation synchronizer, elevation drive motor, and a control box. The terminal processing subsystem comprises 3 units: a terminal interface, a terminal processing microcomputer, and a monitor. The display subsystem comprises 3 units: display control, a display, and a camera. The ranging subsystem consists of a ranging unit. The antenna unit consists of a 1.8-meter parabolic metal antenna and a single 403MHz dipole antenna, forming a dual antenna. Under the control of the trigger pulse output from the ranging subsystem, the transmitting subsystem transmits a high-frequency interrogation pulse signal with amplitude modulation through the 403MHz dipole antenna into the air. This causes the radiosonde to generate a response signal related to the trigger pulse output from the ranging subsystem. The amplitude-modulated response signal is modulated onto a 31.25KHz subcarrier and then modulated to a transmitter frequency of 1680MHz, which is then transmitted into the air by the radiosonde antenna. The ground radar receiver operates at 1680MHz and is used to receive temperature, humidity, and air pressure data from the radiosonde, as well as the radiosonde's response pulses.

3. The electronic radiosonde and radar detection system based on dual-channel digital frequency modulation according to claim 1, characterized in that, The data acquisition module of the measurement conversion unit uses the AD7705BRV module.

4. The electronic radiosonde and radar detection system based on dual-channel digital frequency modulation according to claim 1, characterized in that, The unit model of the measurement conversion unit is PIC16F726.

5. The electronic radiosonde and radar detection system based on dual-channel digital frequency modulation according to claim 1, characterized in that, The transmitter's sounding code modulation circuit consists of R2, RP2, R4, R6 and an ultra-high frequency transistor V1. The digital signals 0 and 1 of the sounding code are divided by resistors R2, RP2, R4 and R6 and then applied to the base of the ultra-high frequency transistor V1, changing the bias voltage Vb of the base of V1. The ranging modulation circuit of the transmitter consists of resistors R1, RP3, R5, R6 and ultra-high frequency transistor V1. The level signals 0 and 1 generated by ranging are divided by resistors R1, RP3, R5 and R6 and then applied to the base of ultra-high frequency transistor V1, changing the bias voltage Vb of the base of V1.

6. The electronic radiosonde and radar detection system based on dual-channel digital frequency modulation according to claim 1, characterized in that, The temperature sensor uses a beaded thermistor circuit.

7. The electronic radiosonde and radar detection system based on dual-channel digital frequency modulation according to claim 1, characterized in that, The humidity sensor uses a polymer thin-film humidity-sensitive capacitor.

8. The electronic radiosonde and radar detection system based on dual-channel digital frequency modulation according to claim 1, characterized in that, The pressure sensor uses a silicon piezoresistive pressure sensor.

9. The electronic radiosonde and radar detection system based on dual-channel digital frequency modulation according to claim 1, characterized in that, Temperature, humidity, and air pressure sensors are connected to the corresponding interfaces of the measurement conversion unit. The microcontroller of the measurement conversion unit receives the measured signals in real time through a multiplexer, converts the collected radiosonde signals into 31.25KHz square wave signals, and transmits them to the ground radar via a transmitter for 0.2 seconds. For the remaining 0.8 seconds, the transmitter is in a radiosonde signal rest state, transmitting only the carrier signal. The receiver receives the transmission pulses sent by the ground radar dipole antenna and generates response pulses to control the transmitter to send a reply signal.

10. The electronic radiosonde and radar detection system based on dual-channel digital frequency modulation according to claim 1, characterized in that, The measurement conversion unit also includes logic gate circuits, which are connected to the data acquisition module, the microcontroller, and the transmitter. The data acquisition module converts the measured values ​​of temperature, humidity, and air pressure into hexadecimal numbers and transmits them to the logic gate circuits at a baud rate of 1.2Kbps via the microcontroller pins. At the same time, the microcontroller outputs a subcarrier and ranging control signal at a baud rate of 31.25KHz. The logic gate circuits are used to modulate the radiosonde code onto the subcarrier at a baud rate of 1.2Kbps and transmit it to the transmitter.

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