TWI435063B - Pulsed radar level gauge - Google Patents

Description

Pulse radar level gauge

The invention relates to a pulse radar liquid level gauge, in particular to a pulse radar device capable of controlling high frequency accuracy, high time resolution and adjustable measuring distance.

It is applied to the industrial non-contact radar wave level gauge. The design premise is that there are many measuring liquid level products in the world, which are all measured by contact type. If the mining environment is strong acid or strong alkali, etc. In the difficult environment, the service life of the measuring instrument will be greatly reduced and easily damaged, and the failure will cause many inconveniences. In recent years, the industrial development has been scientific and technological, and the introduction of the non-contact radar wave level gauge has improved the contact type. The shortcomings of the liquid level gauge can be measured under difficult conditions.

The existing industrial pulse radar (Pulse Radar) liquid level gauge system includes a sampling circuit module, a radio frequency (Radio Frequency) transceiver circuit module, an antenna (Antenna) and a microprocessor (Microprocessor), and the sampling frequency and reflection The signal is sampled at a frequency difference to produce a time delay, forming a microprocessor capable of processing the intermediate frequency signal, and then performing signal processing. For this purpose, a modified adjustable reactance voltage controlled oscillator is used to change the emission in the patent US 4,123,726. The difference between the frequency and the sampling frequency.

As shown in FIG. 5, the conventional sampling circuit utilizes two quartz oscillators 80 and 90 of the same frequency, respectively connected to the two voltage sources 81 and 91, and is externally bypassed by capacitors 82 and 92 and variable in low resistance. The resistors 83 and 93 are controlled by fine adjustment, so that the two output ports respectively output the transmission signals having small frequency differences. With the sampling signal, however, the use of the two quartz oscillators 80, 90 is susceptible to variations in the process resulting in an uncontrollable small frequency offset, and the internal load capacitance of the quartz oscillators 80, 90 needs to match the parasitic capacitance of the PCB, and The internal parasitic capacitance of the PCB is difficult to estimate due to the different positions of the traces. Therefore, the parasitic capacitance of the PCB cannot be calculated. When the oscillation source does not match the PCB, the sampling frequency will be greatly affected. The most important is the variable resistance. The adjustment, this method is easy to cause inconsistency between the two identical systems, resulting in the difficulty of mass production of the product.

The transmission signal period T1 and the sampling signal period T2 have a small frequency difference, so as to facilitate the demodulation action of the pulse radar transmission signal to the intermediate frequency. When the periods of the two signals are different, a time extension factor is generated when performing the mixing (Expanding Time) Factor) is as follows: The time extension factor is affected by the period of the transmission frequency and the period difference of the sampling frequency. As shown in Equation 1, when the difference between the two periods is smaller, the time extension factor is increased. In the 26 GHz millimeter wave radio frequency technology, The frequency changes due to different reactance values, but the frequency error is too large due to a slight change, and the number of time extension factors is insufficient, which makes the sampling of the microprocessor difficult, the time resolution is deteriorated, and the existing voltage control circuit design Complex, so there is a need for further improvement.

In order to solve the problem that the frequency error of the existing voltage controlled oscillator is too large, the time resolution is poor, and the circuit is complicated, the main purpose of the present invention is to provide a Into the existing pulsed radar level gauge, using the microprocessor for digital control, the frequency accuracy and time resolution are significantly improved, and the complexity of the circuit design is reduced.

The technical means used in the present invention is to provide a pulse radar liquid level gauge comprising: a microprocessor; a sampling circuit, which is a programmable control pulse generating unit and is electrically connected to the microprocessor, the micro processing The programmable control pulse generating unit can generate a pulse radar transmitting signal and a sampling signal of different frequencies; a programmable RF transceiver unit is electrically connected to the microprocessor and the programmable control pulse generating unit, and The invention comprises a transmitting circuit and a receiving circuit, wherein the transmitting circuit is configured to generate a carrier signal of a controllable oscillation frequency, and is mixed with the pulsed radar transmitting signal to form a transmitting signal, and the receiving circuit is configured to receive a reflected signal, the reflection circuit The signal includes a signal reflected by the foregoing transmitting signal, and then the receiving circuit cooperates with the sampling signal to down-convert the reflected signal to an intermediate frequency signal, and the microprocessor controls the gain of the signal to the transmitting circuit and the receiving circuit; and Programmable control intermediate frequency processing unit electrically connected to the microprocessor and the programmable control radio frequency Transceiver unit, for converting the analog intermediate frequency signal becomes a digital signal by the microprocessor control signal gain.

The invention utilizes the provided pulse radar device, and the specific benefit that can be obtained is that the present invention utilizes a microprocessor for digital control, and mainly controls the sampling circuit to generate a pulse width of a pulse radar transmission signal and a sampling signal. (Pulse Width) and pulse period accuracy to generate pulsed radar transmit and sample signals with different periodic square waves, to achieve control frequency accuracy, time resolution and measured distance.

In order to understand the technical features and practical functions of the present invention in detail, and in accordance with the contents of the specification, the following is further illustrated in the preferred embodiment as illustrated in the following:

A first preferred embodiment of the pulse radar device of the present invention is shown in FIGS. 1 and 2, and includes a microprocessor 10, a sampling circuit 20 formed by a programmable control pulse generating unit, and a programmable The RF transceiver unit 30 and a programmable intermediate frequency processing unit 40 are controlled.

The programmable control pulse generating unit 20 is electrically connected to the microprocessor 10, and includes a quartz oscillator 21, a programmable pulse frequency synthesizer 22 and two programmable pulse generators 23, 23A. The oscillator 21 is electrically coupled to the programmable pulse frequency synthesizer 22, the programmable pulse frequency synthesizer 22 is electrically coupled to the two programmable pulse generators 23, 23A, the microprocessor 10 is electrically coupled to the The programmable pulse frequency synthesizer 22 and the programmable control pulse generators 23, 23A can control the two programmable control pulse generators 23, 23A to generate a pulse radar transmission signal and a sampling signal respectively at different frequencies; The programmable control pulse frequency synthesizer 22 of the programmable control pulse generating unit 20 uses the quartz oscillator 21 to trigger the programmable control pulse frequency synthesizer 22 to generate two output signals via the microprocessor 10, and respectively transmit the two output signals to the two Programmable control pulse generator 23, 23A, two output signals The frequency difference can be less than 1-100 Hz; then the microprocessor 10 controls the pulse width (Pulse Width) and pulse period accuracy of the two programmable pulse generators 23 to generate pulsed radar signals and samples of different periodic square waves. The signal, in other words, the frequency of the pulsed radar transmit signal and the sampled signal are also different, simplifying the traditional sampling circuit system architecture, and the pulse radar transmit signal period and the sampling signal period are controlled by the microprocessor 10 to enable the frequency. More accurate, in addition, the measured distance can be changed through the pulse width adjustment, so that the overall system measurement can achieve high precision requirements.

The programmable RF transceiver unit 30 is electrically connected to the microprocessor 10 and the programmable control pulse generating unit 20, and includes a transmitting circuit 31, a receiving circuit 32, a voltage controlled oscillator 33 and a coupler 34. The transmitting circuit 31 includes a first up-converter 311 and a power amplifier 312. The first up-converter 311 is electrically connected to the power amplifier 312, the voltage-controlled oscillator 33 and a programmable programmable pulse generator 23. The power amplifier 312 is electrically connected to the coupler 34; the microprocessor 10 is electrically connected to the power amplifier 312, and can control the signal gain of the power amplifier 312, and the voltage controlled oscillator 33 is used to generate a carrier of a controllable oscillation frequency. The signal is mixed with the pulsed radar transmit signal to form a transmit signal. The receive circuit 32 includes a second up-converter 321, a downconverter 322, a low noise amplifier 323, and a filter 324. The second up-converter The 321 is electrically connected to the voltage controlled oscillator 33 and the programmable control pulse generator 23A. The frequency reducer 322 is electrically connected to the second up 321 and the low noise amplifier 323. The low noise amplifier 323 is electrically connected. Connected to Multiplexer 324 and the microprocessor 10, the microprocessor 10 to control the LNA 323 a signal gain, the filter 324 is electrically connected to the coupler 34, the receiving circuit 32 is configured to receive a reflected signal, the reflected signal includes a signal reflected by the transmitted signal, and then down-convert the reflected signal to an intermediate frequency signal.

The programmable RF transceiver unit 30 performs RF transceiving using 26 GHz. The transmitting circuit 31 receives the pulse radar transmission signal from a programmable control pulse generator 23 and carries the 26 GHz carrier signal to the pulse radar transmission signal via the power amplifier 312. The signal strength is enhanced, and the 26 GHz transmit signal is transmitted through the coupler 34 directly coupled to the antenna 50. The coupler 34 can be a branch coupler, a radio frequency switch or a circular splitter, and the 26 GHz transmit signal meets the test. After the object is reflected, the reflected signal is received by the antenna 50, and the reflected signal received by the coupler 34 is first coupled to the receiving loop, and then the frequency is selected by the filter 324 to filter out the frequency signal other than 26 GHz. Varying interference, leaving the required 26 GHz signal, then suppressing the signal noise of the reflected signal via the low noise amplifier 323 and amplifying the signal into the downconverter 322; the voltage controlled oscillator 33 sends a 26 GHz carrier signal and another programmable The sampling signal generated by the control pulse generator 23A enters the second up-converter 321 for mixing to carry the carrier signal of 26 GHz. A 26 GHz pulse sampling signal is generated on the sample signal, and the pulse sampling signal generated by the second up-converter 321 enters the down-converter 322 together with the reflected signal output from the low noise amplifier 323 for mixing to the intermediate frequency. signal.

The programmable intermediate frequency processing unit 40 is electrically connected to the microprocessor 10 and the programmable RF transceiver unit 30, and includes a programmable intermediate frequency amplifier 41, an intermediate frequency filter 42 and an Analogous digit a signal converter 43, the programmable intermediate frequency amplifier 41 is electrically connected to the analog digital signal converter 43 and the down converter 322, and the programmable intermediate frequency processing unit 40 is configured to convert the analog intermediate frequency signal into Digital signal.

The intermediate frequency signal generated by the frequency reducer 322 is transmitted to the programmable intermediate frequency processing unit 40, and the microprocessor 10 controls the programmable intermediate frequency amplifier 41 to adjust the gain to perform gain compensation, and the amplified intermediate frequency signal enters the intermediate frequency. The filter 42 performs filtering to filter out signals other than the intermediate frequency, and after taking out the desired signal, the analog digital signal converter 43 is converted into a digital signal and sent to the microprocessor 10 for processing.

When the reflected signal is mixed with the sampling signal, it can be reduced to the intermediate frequency, so that the number of points read by the microprocessor 10 is more easily processed and demodulated, and therefore, due to the programmable pulse frequency synthesis The frequency difference between the two output signals of the device 22 can be precisely controlled, which is advantageous for the increase of the time extension factor, so that the microprocessor 10 can increase the time resolution when processing.

Another preferred embodiment of the sampling circuit of the pulse radar device provided by the present invention is shown in FIG. 3. The programmable control pulse generating unit 20A includes a quartz oscillator 21 and a programmable pulse frequency synthesizer 22. The quartz oscillator 21 is electrically connected to the programmable pulse frequency synthesizer 22, the programmable pulse frequency synthesizer 22 has two output ports, and the first upconverter 311 is electrically connected to the programmable pulse frequency synthesizer. An output 22 of 22, the aforementioned down converter 322 is electrically connected to another output 该 of the programmable pulse frequency synthesizer 22; the microprocessor 10 is electrically connected to the programmable control pulse frequency synthesizer 22, and can Triggering the programmable control pulse frequency synthesizer 22 generates a pulse radar transmission signal and a sampling signal, and the difference in frequency can be accurately controlled The system facilitates an increase in the time extension factor, so that the microprocessor 10 can increase its temporal resolution when processed.

Further, as shown in FIG. 4, which is a sampling circuit of a pulse radar device, the programmable control pulse generating unit 20B includes two programmable control pulse generators 23, 23A, and the microprocessor 10 is electrically connected. Up to the programmable pulse generators 23, 23A, the first up-converter 311 is electrically connected to a programmable pulse generator 23, and the down-converter 322 is electrically connected to another programmable program. The control pulse generator 23A is controlled by the microprocessor 10 to generate a square wave signal of two different periods of the pulse radar transmission signal and the sampling signal by using the programmable control pulse generator 23, 23A, using a simple programmable pulse generator. The traditional sampling circuit system architecture is simplified, and the transmit signal period and the sampling signal period are controlled by the microprocessor 10, and the frequency is more accurate.

In summary, the sampling circuit of the present invention can use the quartz oscillator 21 as an oscillation source (Crystal) to enter the programmable control pulse frequency synthesizer 22 to generate two output signals, and then the microprocessor 10 triggers the control of the two output signals to generate The frequency difference is slightly different; the two programmable control pulse generators 23 can also be directly matched, and the microprocessor 10 can trigger the two output signal signals to generate a slight frequency difference, so that the reflected signal and the sampled signal are mixed and then reduced to the intermediate frequency. Increasing the readable signal reflected by the microprocessor 10 as a process to increase the signal time resolution; therefore, the sampling circuit of the present invention can effectively avoid the use of a two-crystal oscillator, which is susceptible to process variations and uncontrollable small frequencies. Offset, or change the sampling frequency due to parasitic capacitance of the PCB. Furthermore, the microprocessor 10 controls the pulsed radar transmit signal and the sampled signal generated by the programmable control pulse generator 23 to significantly improve the frequency accuracy and time resolution. Moreover, the measured distance can be changed by the control of the microprocessor 10, so that the sampling rate is increased and is easily handled by the micro-integrator, and the complexity of the circuit design is also reduced.

The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any one of ordinary skill in the art can use the present invention without departing from the technical features of the present invention. Equivalent embodiments of the present invention may be made without departing from the technical features of the present invention.

10‧‧‧Microprocessor

20, 20A, 20B‧‧‧ programmable control pulse generation unit

21‧‧‧Crystal Oscillator

22‧‧‧Programmable Pulse Frequency Synthesizer

23, 23A‧‧‧ Programmable Control Pulse Generator

30‧‧‧Programmable RF Transceiver Unit

31‧‧‧Transmission circuit

311‧‧‧First upconverter

312‧‧‧Power Amplifier

32‧‧‧ receiving circuit

321‧‧‧Second upconverter

322‧‧‧Downer

323‧‧‧Low noise amplifier

324‧‧‧ filter

33‧‧‧Variable Control Oscillator

34‧‧‧ Coupler

40‧‧‧Programmable IF processing unit

41‧‧‧Programmable IF amplifier

42‧‧‧IF filter

43‧‧‧ Analog Digital Signal Converter

50‧‧‧Antenna

80‧‧‧Crystal Oscillator

81‧‧‧voltage source

82‧‧‧ Capacitance

83‧‧‧Variable resistor

90‧‧‧Crystal Oscillator

91‧‧‧Voltage source

92‧‧‧ Capacitance

93‧‧‧Variable resistor

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a first preferred embodiment of a pulse radar level gauge of the present invention.

Figure 2 is a block diagram of the detailed circuit of Figure 1 of the present invention.

3 is a circuit block diagram of another preferred embodiment of the sampling circuit of the present invention.

4 is a circuit block diagram of still another preferred embodiment of the sampling circuit of the present invention.

Figure 5 is a circuit diagram of a conventional sampling circuit.

10‧‧‧Microprocessor

20‧‧‧programmable pulse generation unit

30‧‧‧Programmable RF Transceiver Unit

40‧‧‧Programmable IF processing unit

50‧‧‧Antenna

Claims (4)

A pulse radar liquid level gauge comprising: a microprocessor; a sampling circuit is a programmable control pulse generating unit and is electrically connected to the microprocessor, the microprocessor can control the programmable pulse generation The unit generates a pulse radar transmission signal and a sampling signal of different frequencies; a programmable RF transceiver unit includes a voltage controlled oscillator for providing a carrier signal, a coupler for connecting to the antenna, a transmitting circuit and a receiving circuit The transmitting circuit includes a first up-converter and a power amplifier, the first up-converter is electrically connected to the voltage-controlled oscillator and the sampling circuit, and the first up-converter is electrically connected to the power amplifier, a power amplifier is electrically connected to the coupler; the first up-converter receives a carrier signal and a pulse radar transmission signal from the voltage-controlled oscillator and the sampling circuit, respectively, to mix the carrier signal and the pulse radar transmission signal into a transmission signal, The antenna is externally transmitted; the receiving circuit includes a second upconverter, a downconverter, a low noise amplifier and a filter, the second riser Is electrically connected to the sampling circuit, the filter is electrically connected to the coupler, the low noise amplifier is electrically connected to the filter, and the frequency reducer is connected between the second upconverter and the low noise amplifier; the coupler Receiving a reflected signal from the antenna, the reflected signal comprising a signal reflected by the transmitting signal, the second up-converter receiving a carrier signal and a sampling signal from the voltage controlled oscillator and the sampling circuit, respectively, to the carrier signal Mixing with the sampling signal to form a pulse sampling signal, and the frequency reducing device respectively receives the pulse sampling signal and the reflected signal for mixing, and generates a medium And a programmable intermediate frequency processing unit, comprising: a programmable intermediate frequency amplifier, an intermediate frequency filter and an analog digital signal converter electrically connected in sequence, wherein the programmable intermediate frequency amplifier is electrically connected to the signal The frequency converter of the radio frequency transceiver can be programmed to receive the intermediate frequency signal, and the intermediate frequency filter filters the intermediate frequency signal, and the analog digital signal converter is electrically connected to the microprocessor to convert the intermediate frequency signal After being a digital signal, it is transmitted to the microprocessor. The pulse radar level gauge according to claim 1, wherein the programmable control pulse generating unit comprises a quartz oscillator, a programmable pulse frequency synthesizer and two programmable pulse generators, the quartz An oscillator is electrically connected to the programmable pulse frequency synthesizer, the programmable pulse frequency synthesizer is electrically connected to the two programmable pulse generators, and the two programmable pulse generators are respectively electrically connected to the first frequency division And a second frequency divider, the microprocessor is electrically connected to the programmable pulse frequency synthesizer and the two programmable pulse generators to control the programmable pulse frequency synthesizer and the two programmable pulse generation The pulse radar transmitting signal and the sampling signal are respectively generated to the first frequency divider and the second frequency divider. The pulse radar level gauge of claim 1, wherein the programmable control pulse generating unit comprises a quartz oscillator and a programmable pulse frequency synthesizer, the quartz oscillator being electrically connected to the programmable control a pulse frequency synthesizer, the programmable control pulse frequency synthesizer electrically connecting the first frequency divider and the second frequency divider, respectively, the microprocessor is electrically connected to the programmable control pulse frequency synthesizer to trigger the programmable control a pulse frequency synthesizer respectively generates the pulse radar transmission signal and the sampling signal to the first frequency division And the second divider. The pulse radar level gauge according to claim 1, wherein the programmable control pulse generating unit comprises two programmable control pulse generators, and the two programmable control pulse generators are electrically connected to the first frequency division respectively. And a second frequency divider, the microprocessor is electrically connected to the two programmable control pulse generators for controlling the two programmable control pulse generators to respectively generate the pulse radar transmission signal and the sampling signal to the first frequency divider With the second divider.