CN103488074B - A kind of amplitude variation signal transit time measurement device - Google Patents

Abstract

The invention discloses a measuring device for the transit time of variable-amplitude signals. Since the transmitted signal is sent into the multiplexer and then coupled to the received signal in a crosstalk manner, the transmitted signal and the received signal become an integral signal, and are carried out The same subsequent signal processing, so that the time interval between the transmitted signal and the received signal can be obtained more accurately. At the same time, the present invention adopts RSSI envelope detection for the received signal, and its edge more accurately reflects the time of transmitting and receiving signals, and also improves the measurement accuracy of the time interval to a certain extent.

Description

A Transit Time Measuring Device for Variable Amplitude Signals

technical field

The invention belongs to the technical field of signal processing, and more specifically relates to a measuring device for the transit time of a variable amplitude signal.

Background technique

The measurement of time parameters is widely used in many fields, and most of the processing uses such a working process: start a square wave with a certain frequency to transmit the signal, and start the timer at the same time, the square wave signal is processed and transmitted, and the transceiver circuit receives it. When the signal is received, amplify and shape the received weak signal, output a square wave, and trigger the timer to stop counting. The received signal is a weak signal and its amplitude changes with the change of environmental emission. Simply shaping and amplifying the received signal and adopting a fixed comparison threshold will also introduce certain errors.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, and provide a measuring device for the transit time of the variable amplitude signal, so as to obtain the time interval between the transmitted signal and the received signal more accurately.

In order to achieve the above object, the measuring device for the transit time of the variable amplitude signal of the present invention includes:

A plurality of transmission signal generation circuits are used to generate transmission signals, wherein, in a period of time, only one transmission signal generation circuit works to generate one transmission signal;

It is characterized in that it also includes:

The front end of the multi-channel signal receiving circuit is respectively connected with a plurality of transmitting signal generating circuits for receiving the transmitting signal and the receiving signal, and sending the received transmitting signal or receiving signal to an input terminal of the multiplexer;

The multiplexer is connected to the front end of the multiplex signal receiving circuit respectively, and the received signal it receives is strobed and sent into the receive signal amplifier; the input terminal of the multiplexer is when the input signal exceeds a certain threshold After that, they can be coupled to other channels in the form of crosstalk, so that after the transmission signal is sent to the input terminal of the signal selection output device, its amplitude is greater than the threshold value, and the transmission signal is coupled to the strobed reception signal;

Received signal amplifier and RSSI (ReceivedSignalStrengthIndication, that is, received signal strength indication) envelope detector, amplify the received signal selected by the signal multiplexer, and then perform RSSI envelope detection, and the received signal after detection processing is sent to In the voltage comparison circuit;

Voltage comparison circuit, the received signal processed by the detector is compared with the threshold voltage of the voltage comparison circuit to obtain a square wave signal, the rising edge time of the first square wave in the square wave signal corresponds to the signal transmission time, and the second The rising edge moment of the square wave corresponds to the receiving moment of the received signal;

The time measurement unit measures the time difference between the first rising edge and the second rising edge to obtain the time interval between the transmitted signal and the received signal, that is, the transit time.

The purpose of the present invention is achieved like this:

The transit time measurement device of the variable amplitude signal of the present invention, since the transmitted signal is sent into the multiplexer and then coupled to the received signal in a crosstalk manner, the transmitted signal and the received signal become an integral signal, and the same subsequent signal Processing, so that the time interval between the transmitted signal and the received signal can be obtained more accurately. At the same time, the present invention adopts RSSI envelope detection for the received signal, and its edge more accurately reflects the time of transmitting and receiving signals, and also improves the measurement accuracy of the time interval to a certain extent.

Description of drawings

Fig. 1 is a system structure diagram of a specific embodiment of the amplitude signal transit time measuring device of the present invention;

Fig. 2 is a pulse signal waveform diagram sent into the sensor drive signal generation circuit in Fig. 1;

Fig. 3 is a circuit diagram of the signal selection output device shown in Fig. 1;

Fig. 4 is a schematic diagram of the sensor driving signal generation circuit shown in Fig. 1;

Fig. 5 is a waveform diagram of the drive signal shown in Fig. 1;

FIG. 6 is a waveform diagram of the clamped drive signal shown in FIG. 1;

Fig. 7 is the multiplexer shown in Fig. 1, receive signal amplifier and RSSI envelope detector circuit diagram;

Fig. 8 is the received signal wave diagram after the envelope detection of the RSSI envelope detector shown in Fig. 1;

Fig. 9 is a schematic diagram of the floating threshold detection voltage comparison circuit shown in Fig. 1;

Fig. 10 is a schematic diagram of receiving a square wave signal obtained by level inversion of a fixed threshold comparator circuit;

Fig. 11 is a schematic diagram of receiving a square wave signal obtained by level inversion of a floating threshold comparison circuit;

FIG. 12 is a waveform diagram of the received square wave signal shown in FIG. 1 .

detailed description

Specific embodiments of the present invention will be described below in conjunction with the accompanying drawings, so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when detailed descriptions of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

Fig. 1 is a system structure diagram of a specific embodiment of the device for measuring the transit time of the amplitude signal of the present invention.

In this embodiment, as shown in FIG. 1 , the device for measuring the transit time of the variable-amplitude signal of the present invention includes three parts: a main control processor unit 1 , a time measurement unit 2 , and a transceiver signal processing device 3 .

In this embodiment, four transceiver-integrated sensors 303 are required, respectively corresponding to the four directions of east, west, north, south, and one direction. The transmission signal is emitted by the sensor in one direction and received by the sensor in the opposite direction. In Fig. 1, for the sake of brevity, only a sensor NORTH located in the north as a transmitter and a sensor SOUTH located in the south as a receiver are drawn, and the sensor drive signal generation circuit NORTH and the front end NORTH of the receiving circuit are respectively connected to them. , SOUTH.

In this embodiment, the main control processor unit 1 controls the time measurement unit 2 to generate a pulse signal, which is used as a control signal for the switching transistor MOSFET in the four-way sensor drive signal generation circuit 302, and the pulse signal is sent to the transceiver signal processing device 3 to complete the sensor Generation of driving signals and receiving and processing of received signals. That is, the transceiver signal processing device 3 includes a plurality of transmitting signal generating circuits, a multi-channel signal receiving circuit front end, a multiplex signal multiplexer, a receiving signal amplifier, an RSSI envelope detector and a voltage comparison circuit.

The specific work flow of the variable amplitude signal transit time measurement device of the present invention is as follows: the main control processor unit 1 controls the time measurement unit 2 to generate 5 square wave pulse sequences of 330 kHz every 10 ms, that is, the pulse signal, which is input to the transceiver signal processing device 3 The emission signal generation circuit in the example, in this example, the emission signal generation circuit includes a sensor driving signal generation circuit and a sensor as a transmitter. In order to ensure that only one transmit signal generating circuit works within a time period, this embodiment adopts the output selector 301 to implement.

In this embodiment, the pulse signal passes through the signal output selector 301, and is sent to the sensor drive signal generation circuit NORTH302 connected to the sensor selected as the transmitter to generate a boosted pulse signal of 360Vpp, and output it as a drive signal Generates an emission signal to sensor NORTH as an emitter. The sensor SOUTH303 in the corresponding direction receives the transmission signal as a receiver and converts it into an electrical signal, and inputs it as a received signal in the transceiver signal processing device 3 and converts it into a square wave signal of 0-5V, and the input time measurement unit 2 acquires the transmission signal Select the sensor in other directions to get the time interval between the transmitted signal and the received signal in this direction.

After the variable-amplitude signal transit time measurement device is started, the chip TDC-GP21 first generates five pulse signals of a square wave sequence with a frequency of 330kHz, as shown in Figure 2. The influence of parasitic inductance and parasitic capacitance causes the standard square wave to become the waveform shown in Figure 2), which is sent to the dual-channel four-channel analog signal multiplexer/signal output selector 74HCT4052, and processed by the main control The two digital input pins S0 and S1 connected to the device I/O port are strobed. As shown in FIG. 3, in this embodiment, S0 and S1 are 0 and 0, so that the 1Y0 end of the signal output selector 301, that is, the multiplexer/signal output selector 74HCT4052, is gated, that is, the drive signal DRIVE_NORTH is loaded to The gate of the MOSFET at the front end of the pulse transformer in the sensor drive signal generation circuit NORTH302 is used as the control signal to drive the MOSFET on and off.

Since four sensors are required in this embodiment, there are four sensor drive signal generation circuits, and these four circuits are the same. Figure 4 shows one of the sensor drive signal generation circuits. When the sensor is used as a receiver A part of the circuit at the back end is the front end 304 of the signal receiving circuit.

As shown in Figure 4, after the 12VDC voltage is limited by two parallel 100Ω resistors R10 and R11, it is used as the initial voltage boosted by the pulse transformer T1, and the capacitors C13 and C14 are filter capacitors for the power supply VCC_+12V. The 330kHz square wave pulse sequence is loaded to the MOSFET as the on-off switch of the primary coil of the pulse transformer, and the 12V DC voltage can be boosted to Vpp close to 400V after being processed by the pulse transformer T1 with a primary-to-secondary ratio of 1:30. The high-voltage pulse is the driving signal, as shown in FIG. 5 , and then the high-voltage pulse is loaded on the sensor 303 to excite it to emit a signal.

As shown in Figure 4, when the secondary coil of the pulse transformer T1 is turned on, a DC-isolated capacitor C2 is connected to the rear end of the sensor. Since the voltage applied to the sensor is very large (Vpp is about 360V), the DC-isolated capacitor C2 The withstand voltage value of the capacitor is 1000V. At the same time, in order to avoid the damage of the signal processing circuit caused by the high-voltage pulse, two anti-parallel diode pairs BAV99W are connected to the ground at the back end of the DC blocking capacitor, so that the grounded two reverse The diode connected in parallel clamps the input terminal of the multiplexer/signal output selector 74HCT4052 of the receiving circuit behind, and the voltage amplitude of the clamped signal is about 0.4V, as shown in Figure 6.

The DC-isolated capacitor C2 and two anti-parallel diode pairs BAV99W form the front end of the signal receiving circuit. The driving signal applied to the sensor or the received signal received by the sensor passes through the DC-isolated capacitor C2 and then sent to the multiplexer 305 in.

At the same time, since the selected sensor is an integrated transceiver, in order to avoid the receiving signal and the secondary coil of the pulse transformer T1 forming a loop when the sensor is used as a receiver, a high-speed bidirectional diode chip of NXP Company is added between the pulse transformer T1 and the sensor. BAV99W.

The signal received by the sensor is very weak, which is a voltage signal of mV level. Since the conduction voltage of the diode is 0.7V, the amplitude of the received signal prevents it from forming a loop through the BAV99W and the secondary coil of the pulse transformer, but can only enter the corresponding gate channel of the multiplexer/output selector 74HCT4052. In this embodiment, S0 and S1 are 0 and 0, and the 2Y0 input terminal is selected for output.

As shown in Figure 7, since the signal ECHO_NORTH received by the sensor SOUTH as a receiver needs to pass through the corresponding channel 2Y0 of the gating multiplexer/output selector 74HCT4052, only one of the four channels is gated. . When the sensor NORTH shown in Figure 4 is used as a transmitter, the back end, that is, the ECHO_SOUTH at the front end of the signal receiving circuit is connected to the selection input terminal 2Y4 of the multiplexer/output selector 74HCT4052, so the signal is in the multiplexer/output selection tor 74HCT4052 is not gated. In this embodiment, the selected dual-channel four-channel analog signal multiplexer/selection output device 74HCT4052, when the peak-to-peak value of the crosstalk signal passing through one of its channels exceeds 110mV, the signal will be coupled in the form of crosstalk to the selected channel, and then output from the selected channel after -60dB attenuation. From Figure 6, we can see that the peak-to-peak value of the signal exceeds the threshold of 110mV, so the signal passes through the multiplexer/selection output 74HCT4052 in the form of crosstalk between channels, and the amplitude of the received signal received by the receiver Values are on the order of mV without crosstalk between channels of the multiplexer/select outputter 74HCT4052. In this way, as shown in Figure 7, when the 2Y4 terminal of the multiplexer/selection output device 74HCT405274HCT4052 is connected to the sensor NORTH as the transmitter, the rear end is the front end of the signal receiving circuit. The 2Y4 terminal enters the multiplexer/selection output device 74HCT4052, and then crosstalks and couples to the receiving signal ECHO_NORTH. At this time, the received signal of ECHO_SOUTH in FIG. 7 is actually the clamped drive signal DRIVE_NORTH. After such ingenious processing, the signal at the time of sensor driving and the signal received by the receiver become an integral signal.

The pulse signal after the high-voltage pulse passes through the clamping circuit is used as the starting signal of the transmission, that is, the pulse signal is used as the original signal at the beginning of the measurement time interval.

In the present invention, only a piece of 74HCT4052 chip is used. When the sensor is used as a transmitter, this chip is used as a signal output selector 301, which is the part shown in Figure 3. When the sensor is used as a receiver, this chip is used as a multiplexer 305 That is, the part given in Figure 7. In order to make the drawn circuit easy to understand, in the present invention, the chip 74HCT4052 is divided into two parts according to the multiplexer and the signal selection output device for drawing, see the circuits shown in Fig. 4 and Fig. 7 .

In this embodiment, as shown in Figures 1 and 7, the transceiver signal processing device also includes three module circuits: a receive signal amplifier, an RSSI envelope detector and a floating threshold voltage comparison circuit, after processing by these three module circuits In order to convert the received signal into a square wave signal of 0-5V.

Since the received signal is very weak and the amplitude is at the mV level, it needs to be filtered and amplified before other effective processing can be performed. Since the sensor has fixed physical characteristics, the signal received by the receiver has good consistency, that is to say, the number of cycles from the first wave point to the peak point is the same, and is not affected by the amplitude. According to this feature of the received signal, the filtered and amplified received signal is subjected to envelope detection processing, so that the time interval can be obtained very accurately.

In this embodiment, as shown in FIG. 7 , chip SA614AD is used to implement filter amplification and envelope detection processing of received signals. The chip integrates two-stage limiting intermediate frequency amplifier, quadrature detector, noise suppression, and logarithmic received signal strength indicator (RSSI). In the present invention, the first stage intermediate frequency amplifier of the chip is used to amplify the received signal, and then the RSSI module is used to realize the RSSI envelope detection of the amplified received signal (the logarithmic method is used to realize the envelope detection).

When the sensor is used as the receiving end, the received signal is strobed and output by the chip 74HCT4052, and then enters the chip SA614AD through pin 16. In this chip, the received signal is first amplified by the intermediate frequency amplifier with a gain of 39dB, and then the amplified received signal is After the signal is processed by RSSI for envelope detection, it is output from pin 5, and the output waveform is shown in Figure 8. In the circuit shown in Figure 7, C17, C22, C25, and C31 are all 100nF decoupling capacitors recommended in the SA614A chip documentation. R19, C23, R18, C18, and C19 are calculated based on the IF input impedance of pin 16, the IF output impedance of pin 14, and the limiter input impedance of pin 12 of the SA614A.

In this embodiment, as shown in Figure 1, after the received signal is filtered and amplified and processed by RSSI envelope detection, it needs to be processed by the floating threshold voltage comparison circuit 307 to convert it into a square wave signal of 0-5V. The floating threshold voltage comparator circuit 307 is composed of an ultra-high-speed, high-precision, rail-to-rail comparator LMV7239M5. In this embodiment, the threshold voltage of the voltage comparison circuit is not a fixed value, it is jointly determined by the received signal and the 5V power supply. The specific circuit is shown in Figure 9, including a comparator LMV7239M5. The received signal RSSI_OUT after detection is input to the positive terminal of the comparator through a resistor R14; the power supply voltage is divided by two resistors R12 and R20 connected in series to the ground. It is connected to the negative terminal of the comparator, and at the same time, the series point is connected to the positive terminal of the comparator through another resistor R17. Two resistors R12 and R20 connected in series to the ground are connected in parallel with a capacitor C24 at both ends of the resistor R20 connected to the ground. The comparator The output terminal outputs the receiving square wave signal.

In the circuit shown in Figure 10, when the received signal processed by the chip SA614A has not been sent to the non-inverting terminal of the comparator, the threshold voltage of the comparator can be calculated to be approximately equal to 1V. When the processed received signal enters the non-inverting terminal of the comparator, the received signal will enter the inverting terminal of the comparator through the resistor R17. It can be seen from Figure 8 that the received signal sent to the comparator is not a regular signal of equal amplitude, and the amplitude of the received signal will change, but its phase will basically not change, so the received signal is a non-equal amplitude signal. If a fixed value is used as the comparator The threshold voltage will introduce random errors due to changes in the amplitude of the received signal. By adopting a variable threshold and allowing the threshold of the comparator to be adjusted according to the amplitude of the input signal, the error introduced by the amplitude change of the received signal can be eliminated to a certain extent. In the design of Figure 9, if the RSSI_OUT input signal is Vin, and the voltage across C24 is Vo, then the initial moment is:

$\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 20</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; cc</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 17</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Where R12=1.5M, R20=1.5M, R14=1.5K, R17=499K, Vcc=5V,

Substitute into the above formula to get:

V _o =V _cc -V _o +3(V _in -V _o ) (2)

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; cc</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 3</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; 5</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

From the above formula (3), as the amplitude of the RSSI_OUT input signal increases, Vo, that is, the voltage across the capacitor C24 rises, and the capacitor starts to charge. The RSSI_OUT input signal has a large amplitude and a large rising slope, and the voltage across C24 also increases. Fast, the charging speed of capacitor C24 is fast, thereby raising the threshold voltage of the comparator, which can reduce the time interval measurement error caused by the fixed threshold level when the level is flipped.

As shown in Figure 10 below, the curves S1 and S2 in the figure respectively represent two received signals with different amplitudes entering the comparator. The reference terminal voltage of the comparator is L, and a fixed threshold is used. At this time, the S1 input curve comparator is at point A' Trigger, the corresponding time is TA'; the S2 input curve comparator is triggered at point B', the corresponding time is TB', therefore, two signals with different amplitudes of S1 and S2 correspond to the same comparison threshold phase, there will be TB'-TA' error. However, as shown in Figure 11, with a changing threshold, when the comparator input is S1, the corresponding reference terminal signal is curve L1, the comparator is triggered at point A, and when the comparator input is S2, the corresponding reference terminal signal is curve L2, the comparator is triggered at point B. At this time, it can be seen that the time difference between points A and B is smaller than the time difference between A' and B' in Figure 10. The changing threshold can reduce the phase error compared with the fixed threshold, so that Reduce the time interval measurement error caused by the fixed threshold level when the level flips.

The waveform of the comparator output signal is shown in Figure 12. It can be seen from Figure 12 that the moment when the transmitting signal is generated corresponds to the rising edge of the first square wave, and the moment when the signal received by the sensor as a receiver corresponds to the rising edge of the second square wave. Therefore, the measurement of the time interval is to measure the time difference between the first rising edge and the second rising edge.

Although the illustrative specific embodiments of the present invention have been described above, so that those skilled in the art can understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, As long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are included in the protection list.

Claims (2)

1. A time-of-flight measurement device for a variable-amplitude signal, comprising: A plurality of transmission signal generation circuits are used to generate transmission signals, wherein, in a period of time, only one transmission signal generation circuit works to generate one transmission signal; It is characterized in that it also includes: The front end of the multi-channel signal receiving circuit is respectively connected with a plurality of transmitting signal generating circuits for receiving the transmitting signal and the receiving signal, and the front end of the signal receiving circuit sends the received transmitting signal or receiving signal to the simultaneous an input terminal; The multiplexer is connected to the front end of the multiplex signal receiving circuit respectively, and the received signal it receives is strobed and sent into the receive signal amplifier; the input terminal of the multiplexer is when the input signal exceeds a certain threshold After that, they can be coupled to other channels in the form of crosstalk, so that after the transmit signal is sent to the input end of the multiplexer, its amplitude is greater than the threshold, and the transmit signal is coupled to the gated receive signal; Received signal amplifier and RSSI (ReceivedSignalStrengthIndication, that is, received signal strength indication) envelope detector, amplify the received signal selected by the multiplexer, and then perform RSSI envelope detection, and the received signal after detection processing is sent to the voltage In the comparison circuit; Voltage comparison circuit, the received signal processed by the detector is compared with the threshold voltage of the voltage comparison circuit to obtain a square wave signal, the rising edge time of the first square wave in the square wave signal corresponds to the signal transmission time, and the second The rising edge moment of the square wave corresponds to the receiving moment of the received signal; The time measurement unit measures the time difference between the first rising edge and the second rising edge, that is, the time interval between the transmitted signal and the received signal, that is, the transit time. 2. The time measurement device according to claim 1, wherein the voltage comparison circuit is a floating threshold voltage comparison circuit, comprising a comparator, four resistors and a capacitor; The received signal after detection is input to the positive terminal of the comparator through a resistor R14; the power supply voltage is divided through the other two resistors R12 and R20 connected in series to the ground. The four resistors R17 are connected to the positive terminal of the comparator, and the other two resistors R12 and R20 connected in series to the ground are connected in parallel with a capacitor C24 at both ends of the resistor R20 connected to the ground, and the output terminal of the comparator outputs a receiving square wave signal.