RU2419812C1 - Differential sensor to detect moving objects - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: proposed device comprises two antennas, pulse generator, differential amplifier, feedback device, two low frequency filters, comparator, input circuit made up of two detector. Note here that pulse generator allows generating radio pulses.

EFFECT: increased detection range.

7 dwg

Description

Technical field

The invention relates to radio engineering and can be used to detect a moving object, for example, human movement in a zone controlled by a sensor.

State of the art

The main types of currently existing object motion sensors are infrared sensors, ultrasonic detectors, capacitive object motion sensors, radio wave motion detectors, Doppler sensors and combined sensors.

Radio wave motion detectors operate in the microwave range. Radiation and reception are carried out by one (two) antenna. Radio wave detectors form a volumetric detection zone due to energy reflections. The operation of such sensors is based on the use of the Doppler effect or the interference of centimeter-wave radio waves.

Closest to the claimed technical solution is a sensor for detecting moving objects using an ultra-wideband signal (RU, No. 2311658, publ. 11/27/2007).

This sensor is a device for detecting and monitoring moving objects. The sensor contains a pulse generator, two antennas, two detectors, a differential amplifier, a low-pass filter, a feedback device, a comparator. To detect and monitor moving objects, an ultra-wideband (UWB) pulse signal is emitted by the antennas and a signal reflected from surrounding objects is received. A certain distribution of the electromagnetic field is formed in space, which changes when moving objects appear, and this change is recorded by the sensor.

The advantages of such a sensor:

- a wide range of sounding signal, allowing the use of small emitted levels;

- low power consumption due to the pulsed nature of the radiation and high duty cycle;

- the use of a differential circuit allows you to compensate for the noise incident on the sensor in the form of plane waves of an electromagnetic field, which significantly increases the sensitivity of the sensor.

However, the known technical solution has certain disadvantages.

The device uses an ultra-wideband probe signal occupying a frequency band from hundreds of megahertz to several gigahertz. The use of such signals in many countries is prohibited, and in those countries where it is allowed, there are significant restrictions on the amplitude and power of the emitted signals. For example, in the USA, the FCC 02-48 standard limits the spectral power density of UWB radiation power to a signal of -43 dBm / MHz. This significantly reduces the possibility of using the sensor both in detection range and in applications.

In addition, the negative feedback used in the known technical solution changes the mode of operation of the detector and reduces the transmission coefficient of the useful signal. A decrease in the feedback voltage increases the gain of the detector, which neutralizes its effect and requires the use of differential amplifiers with a large gain. With large imbalances in the sensor caused by the environment, it may stop functioning. The device requires the predominant use of loop antennas.

Disclosure of invention

The problem solved by the invention is the improvement of technical and operational characteristics.

The technical result that can be obtained by carrying out the invention is to increase the detection range, improve operational capabilities by significantly narrowing the emission frequency range of the probe signal and expanding the feedback adjustment range, which, in turn, allows expanding the range of environmental properties around the sensor.

To solve the problem with achieving the specified technical result in a known sensor for detecting moving objects containing a first antenna and a second antenna, a pulse generator made with two outputs, and the first output of which is respectively connected to the input / output of the first antenna, and its second output - to the input / output of the second antenna, an input circuit consisting of two detectors, the input of the first detector is connected to the input / output of the first antenna, and the input of the second detector to the input / output of the second antenna, different a social amplifier, feedback device, low-pass filter, comparator, while the output of the first detector is connected to the first input of the differential amplifier, and the output of the second detector is connected to the second input of the differential amplifier, the output of the differential amplifier is connected to the input of the low-pass filter and to the input of the feedback device communication, which is designed to suppress external interference of the sensor and whose output is connected to the output of one of the detectors, the output of the low-pass filter is connected to the input of the comparator, on the other the control input of which the voltage of the sensor threshold is applied, and the comparator output is designed to generate a sensor alarm, according to the invention, the pulse generator is designed to generate radio pulses and is based on the generator of the driving pulses and the harmonic signal generator, the output of the driving pulse generator is connected to the input of the harmonic signal generator , and its two outputs serve respectively as two outputs of the pulse generator, an additional low-pass filter is introduced The feedback device is made with two outputs, the first of which is connected to the output of one of the detectors, and the second output of which is connected through an additional low-pass filter to the input of that detector, to the output of which the first output of the feedback device is connected.

These advantages, as well as the features of the present invention are illustrated by the cited embodiment with reference to the accompanying figures.

Brief List of Drawings

Figure 1 depicts a functional diagram of the sensor;

Figure 2 is a schematic diagram of a pulse generator, namely radio pulses (THREE);

Figure 3 - diagrams of the formation of the output video pulse of the generator in figure 2;

Figure 4 - waveforms of the output signals: the video pulse of the generator of the driving pulses and the radio pulse (GRI) in figure 2;

5 is a schematic diagram of the input circuit in figure 1;

6 is a schematic diagram of a differential amplifier in figure 1;

Fig.7 is a schematic diagram of the feedback device of Fig.1.

The best embodiment of the invention

The sensor for detecting moving objects (Fig. 1) contains a first antenna 1 and a second antenna 2, a pulse generator 3 made with two outputs, and the first output of which is respectively connected to the input / output of the first antenna 1, and its second output to the input / the output of the second antenna 2. The input circuit 4 consists of two detectors 5 and 6. The input of the first detector 5 is connected to the input / output of the first antenna 1, and the input of the second detector 6 is connected to the input / output of the second antenna 2. The sensor contains a differential amplifier 7 (remote control ), feedback device 8 (SLD), filter 9 low frequencies (LPF), comparator 10. The output of the first detector 5 is connected to the first input of the differential amplifier 7, and the output of the second detector 6 is connected to the second input of the differential amplifier 7. The output of the remote control 7 is connected to the input of the LPF 9 and to the input of the ASL 8. Device 8 feedback is intended for automatic balancing of the sensor, suppression of its external noise, and its output is connected to the output of one of the detectors, for example, the second detector 6. The output of the low-pass filter 9 is connected to the input of the comparator 10. The control input of the comparator 10 is respectively fed to posal sensor response threshold, and the output of comparator 10 is designed to generate an alarm device.

The pulse generator 3 is configured to generate radio pulses and is based on the generator 11 of the master pulses and the harmonic signal generator 12. The output of the generator 11 of the driving pulses is connected to the input of the generator 12 of the harmonic signal, and its two outputs serve respectively as two outputs of the generator 3 pulses. An additional low-pass filter (LPSF) 13 is introduced into the sensor. The feedback device 8 is made with two outputs, the first of which is connected to the output of one of the detectors, for example, the second detector 6. The second output of the SLD 8 is connected through an additional low-pass filter 13 to the input of that detector, for example, the second detector 6, to the output of which the first SLD output 8.

The device allows the use of any type of antenna 1 and 2.

The device operates (figure 1) as follows.

The pulse generator 11 generates pulses that are used to power the harmonic signal generator 12 with two outputs.

As a result, when applying pulse power to the outputs of the generator 3 (GRI), radio pulses are generated by the antennas 1 and 2 and at the same time unlocking diodes of the first detector 5 and the second detector 6. The pulse duration of the generator 3 (GRI) determines the time interval for opening the diodes of the first and second detectors 5 , 6 and, therefore, the range zone within which the sensor receives signals reflected from distant moving objects. On the other hand, the center frequency and the spectral width of the generated GREE radio pulses of the generator 3 are determined respectively by the center frequency of the harmonic signal generator 12 and the pulse width of the generator 11. The short duration of the radio pulse determines the short opening time of the diodes of the first and second detectors 5, 6 and provides a small level of interference coming from antennas 1, 2 to the inputs of the input circuit 4 of the receiver. The first and second detectors 5, 6 are a diode mixer, the voltage difference in the shoulders of which is amplified by a remote control 7. To eliminate a possible imbalance in the signals from the reception channels, the first and second detector 5, 6 use SLR 8 with two outputs. The introduction of feedback using SLD 8 automatically in the absence of moving objects in the area of the first and second antennas 1, 2 maintains a constant output signal at the output of the remote control 7, equal to half the supply voltage (0.5 VCC).

The use of feedback with two outputs, in addition to providing a constant output signal of the remote control 7, maintains a constant potential difference between the cathode and anode of the detector diode 6 with a significant imbalance of antennas 1 and 2, caused, for example, by the influence of an inhomogeneous external environment near antennas 1 and 2. Additional filter 13 low frequencies provides the connection of feedback to the input of one of the detectors, for example, the second detector 6, and the necessary isolation of the high frequency of the generated radio pulses. The time constant of SLD 8 is chosen to eliminate the slow imbalances of the first and second antennas 1, 2 and the first and second detectors 5, 6, caused by the influence of weather conditions (snow, ice, temperature). The influence of changes in weather conditions causes slow changes in signals that occur over a period of more than 10 s. At the same time, rapid changes in signals caused by the movement of living people occur at frequencies from 0.1 to 10 Hz, and such rapid changes in signals are properly transmitted to the output of the remote control 7.

The amplified signal difference obtained from the output of the remote control 7 is filtered by the low-pass filter 9 with a passband of about 10 Hz and a gain of ≈20 dB. From the low-pass filter 9, the signals are fed to the comparator 10, generating signals of the transistor-transistor logic (TTL) level when the specified threshold for the input signal from the low-pass filter 9 is exceeded.

When any moving object appears in the area of the first and second antennas 1, 2, the signals reflected from it are received by the first and second antennas 1, 2 and detected by the input circuit 4. Since antennas 1 and 2 are spatially separated, the signals received by them will differ in form, amplitude and delay, and at the output of the remote control 7, an output signal appears, which, after comparison with the threshold in the comparator 10, is used to issue an alarm.

To stabilize the operating point of the detector, for example, the second detector 6, the input of which is connected to the feedback device 8, an additional low-pass filter 13 is used. In the known technical solution, the negative feedback of the SLD 8 connected to the output of the second detector 6 changes the operating mode of this detector and reduces the transmission coefficient of the useful signal. Reducing the feedback voltage increases the gain of the second detector 6, which neutralizes its effect and requires the use of a differential amplifier 7 with a large gain. With large imbalances in the sensor caused by the environment, it may stop functioning. To eliminate these negative consequences of the feedback applied to the output of the second detector 6 (to the input of the remote control 7), the voltage from the second output of the feedback device 8 is also supplied to the input of the second detector 6. Since a high-frequency signal is present at the input of the second detector 6, this voltage is supplied through an additional low-pass filter 13, which passes only the low-frequency negative feedback signal and eliminates the shunt of the input circuit of the second detector 6 by the output of the feedback device 8. Under these conditions, the voltage at the input and output of the second detector 6 under the action of feedback changes synchronously, ensuring the constancy of the position of its operating point. Connecting feedback to the input of the second detector 6 increases its efficiency and reduces the gain of the differential amplifier 7 and its stability at different signal levels from the outputs of the first and second detectors 5, 6 by more than 10 times.

The device uses a radio-pulse sounding signal. The pulse duration of generator 3 (GRI) is hundreds of nanoseconds, which, on the one hand, determines a fairly low power consumption (at a repetition frequency of units and tens of kilohertz), and on the other hand, allows you to work in a given (allowed for use) frequency range and provide high noise immunity in various weather conditions on the emitted signals of low power.

Those skilled in the art will understand that the functional blocks shown in FIG. 1 can be performed in technically different ways, but without altering the essence of the invention given in the independent claim.

Next, for example, the implementation of the individual functional blocks depicted in figure 1 is described in more detail.

Generator 3 (figure 2) consists of a generator 11 of the driving pulses and the generator 12 of the harmonic signal. Generator 11 is an RC multivibrator on RS and D flip-flops. The RS-flip-flop D1 is a multivibrator generating a meander with an amplitude of A = 3V, a frequency of about 10 kHz, a duration of fronts of 1 ns and a constant component of A / 2 = 1.5 V. The storage capacitors C1 and C2 at the inputs of the logic zero and one and the resistors R1 and R2 in the feedback circuits form the corresponding duration of the half-waves of the meander and the repetition rate of the output pulses. Diodes VD1 and VD2 are used to accelerate the processes of charge and discharge of capacitors C1 and C2, respectively.

D-trigger D2 is used to generate a video pulse with the given parameters, the duration of which is determined by the feedback length, the internal signal delay in a specific microcircuit, the capacitance of the capacitor C3 and the resistance of the resistor R3.

The harmonic signal generator 12 (figure 2) is a master oscillator on the transistor VT1 and the shapers of the outputs on the transistors VT2 and VT3, included in the scheme with a common emitter. The master oscillator contains in the base circuit an oscillating circuit of capacitor C4 and a structural strip line. Feedback is determined by a capacitive divider on capacitors C5 and C6.

The generator 3 (GRI) operates as follows (figure 2).

When the power is turned on, trigger D1 is set to its initial state, corresponding, for example, to a logical unit. The capacitor C1 begins to slowly charge and when it is charged, a logic zero is supplied to the logic zero input, resetting trigger D1 to zero. The charge / discharge graph of capacitor C1 at the input of setting logic zero R of trigger D1 is shown in figure 3 (A). At this moment, the charge of the capacitor C2 begins and when it is fully charged, a logical zero is received at the input of the logical unit setup and trigger D1 is set to the state of the logical unit. The charge / discharge graph of the capacitor C2 at the input of the installation of the logical unit S of the trigger D1 is shown in figure 3 (B). Thus, the synchronization input of the trigger D2 from the non-inverting output Q1 of the trigger D1 receives a meander with a given frequency, a graph of which is shown in figure 3 (C). The duration of the processes of charge and discharge of the capacitors C1 and C2 determines the duration of the half-wave of the meander and the repetition rate of the output pulses of the generator. Trigger D2, triggering along the front of the meander, takes the value of a logical unit for a time equal to the path length of the signal along the feedback circuit and the internal delay of the trigger. The time dependence of the voltage from the non-inverting output Q2 of trigger D2 is shown in Figure 3 (D).

The output Q2 is connected to the power circuit of the harmonic signal generator 12. When the voltage rises due to positive feedback on the capacitor C5, the oscillator 12 self-excites and it generates harmonic oscillations with a frequency determined by the oscillatory circuit in the base circuit. A coarse frequency setting is determined by the length of the shorted at the end of the strip line connected in series with the capacitor C4. Smooth frequency adjustment is carried out by the capacitor C4. At the end of the pulse at the output of Q2, generation ceases.

The high-frequency signal from the emitter VT1 goes to the base of transistors VT2 and VT3 is amplified and through the capacitors C 8 and C 10 it goes to the outputs Out1 and Out2.

As a result, two output radio pulses are formed at the outputs of generator 3 (GRI). The duration, repetition period, and carrier frequency of radio pulses can vary widely. The oscillation modes of the video pulse from the output of the generator 11 of the driving pulses and the radio pulse from the output of the generator 12 are shown in Fig. 4.

The input circuit 4 of the sensor is a two diode detector (figure 5). In the absence of radio pulses from the GRI 3 diodes (VD1 and VD2) are locked, which provides noise immunity and a reduction in the frequency of false positives. Radio pulses are fed to the anodes of the VD1 and VD2 diodes, unlocking them during the positive half-waves, and are simultaneously emitted through the first and second antennas 1 and 2. During the duration of the radio pulse, signals from the first and second antennas 1 and 2 are received, and in the absence of a radio pulse, reception is not carried out . Capacitors C1 and C2 are charged by radio pulses through the diodes VD1 and VD2, respectively. In the absence of radio pulses, a discharge of capacitors occurs through the input circuits of the remote control 7. As a result, in a static mode, a certain operating pulsating voltage is established on the capacitors, which is applied to the inputs of the remote control 7. At the output of the remote control 7, a constant output voltage is established in the static mode.

When moving objects appear in the location of antennas 1 and 2, voltages at the outputs of these antennas change due to changes in the signals reflected from the surrounding objects. The sensor is triggered due to the voltage imbalance on the capacitors C1 and C2, caused by the reception of various signals by antennas 1 and 2 (A1 and A2). The voltage difference between the first and second outputs of the input circuit 4 is amplified by the remote control 7.

As a differential amplifier 7 (FIG. 1), a standard differential amplifier circuit for two operational amplifiers is used (FIG. 6). The output of the first operational amplifier D1 is connected to the inverting input of the second operational amplifier D2.

The signal from the output of the remote control 7 is fed to the input of the ASL 8 and the low-pass filter 9 (figure 1). The low-pass filter 9 and the comparator 10 can be performed similarly to the closest analogue. Changes in the ambient temperature and dielectric constant of the medium surrounding the first or second antennas 1 and 2, leads to the appearance of various voltages at the outputs of the detectors 5, 6 and, as a result, a constant voltage at the output of the remote control 7. This voltage can cause the comparator 10 and its the wrong job. To suppress this effect, a feedback device 8 with two outputs is included in the circuit (Fig. 1), the input of which is supplied with a signal from the output of the remote control 7, and its first output is connected to the output of the detector 6, and the second output is connected through a second additional filter connected in series 13 low frequencies (DPF) to the input of the detector 6.

The feedback device 8 (Fig. 7) consists of an integrator implemented on an operational amplifier. The time constant of the RC feedback circuit of the operational amplifier determines the minimum speed with which the object can be registered by the sensor and is determined by the ratio

where Toc is the feedback circuit time constant, s;

S is the distance covered by the object in the volumetric zone of detection of the sensor, m;

Vmin is the minimum speed with which an object can move to register its movement sensor, m / s.

In the practical implementation of the device, the time constant, for example, is 12 seconds, which corresponds to the minimum speed of a moving object.

The voltage at the output 1 of the ASL 8 is supplied from the output 2 through the resistor R3. The use of two outputs with synchronously changing voltages for feedback makes it possible to stabilize the voltage between the cathode and anode of the detector diode while stabilizing the output voltage of the remote control in a wide range of destabilizing factors.

In contrast to the closest analogue of UOS 8 with two outputs, it allows to significantly expand the range of possible changes in environmental properties, for example, to place the sensor on concrete surfaces and near metal structures. The resulting imbalance of the channels does not lead to a change in the detector mode, loss of sensitivity and limitation of the output voltage in the remote control 7.

The use of a radio pulse of adjustable duration in this technical solution allows, in contrast to the closest analogue, to change the occupied frequency band and the central radiation frequency. The design of narrow-band antennas can also be simpler and, in the particular case, allows the implementation of antennas on a printed circuit board. Due to the work in the allowed sections of the frequency range, it is possible to use a greater radiation power than that of the closest analogue and detect objects at distances of more than 1 ÷ 5 m, for example 10 ÷ 20 m.

Industrial applicability

The most successfully declared sensor for detecting moving objects is industrially applicable for their detection at distances from 1 to 20 m in various security systems.

Claims (1)

A sensor for detecting moving objects, comprising a first antenna and a second antenna, a pulse generator made with two outputs, and the first output of which is respectively connected to the input / output of the first antenna, and its second output to the input / output of the second antenna, an input circuit consisting of of two detectors, the input of the first detector is connected to the input / output of the first antenna, and the input of the second detector is connected to the input / output of the second antenna, differential amplifier, feedback device, low-pass filter, comparator, while the output the first detector is connected to the first input of the differential amplifier, and the output of the second detector is connected to the second input of the differential amplifier, the output of the differential amplifier is connected to the input of the low-pass filter and to the input of the feedback device, which is designed to suppress external interference of the sensor, and the output of which is connected to the output one of the detectors, the output of the low-pass filter is connected to the input of the comparator, the voltage of the sensor threshold is applied to the other control input, and the output of the comparator it is designed to generate a sensor alarm, characterized in that the pulse generator is configured to generate radio pulses and is based on the generator of the driving pulses and the harmonic signal generator, the output of the driving pulse generator is connected to the input of the harmonic signal generator, and its two outputs respectively serve as two outputs of the pulse generator , an additional low-pass filter is introduced, the feedback device is made with two outputs, the first of which is connected to the output o one of the detectors, and the second output of which is connected through an additional low-pass filter to the input of that detector, to the output of which the first output of the feedback device is connected.

Images