JP4039947B2 - Electromagnetic proximity detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic proximity detector that detects that a detection object such as a human being or an animal has approached, and more particularly, to an electromagnetic proximity detector that can reduce power consumption.
[0002]
[Prior art]
Conventionally, as this type of electromagnetic proximity detector, there is an electromagnetic proximity sensor disclosed in Patent Document 1. FIG. 3 of Patent Document 1 shows electromagnetic wave radiation including a gallium arsenide FET 2a for microwave oscillation, and an oscillation coil 2b that is connected to the base of the gallium arsenide FET 2a and is configured by a distributed constant circuit, which also serves as an antenna. Extracted by the disturbance component extraction unit 3, the disturbance component extraction unit 3 that amplifies the collector voltage fluctuation extracted from the collector of the gallium arsenide FET 2 a of the electromagnetic wave radiation unit 2, and limits the band to extract the disturbance component An electromagnetic wave proximity sensor including a level comparison unit 5 that compares a disturbance component with a predetermined reference level and outputs a sensor signal when a disturbance component larger than the reference level is detected is disclosed.
[0003]
According to this electromagnetic proximity sensor, electromagnetic waves are radiated to the detection area from the oscillation coil 2b that also serves as an antenna. When a detection object approaches the detection area, the electromagnetic wave is reflected while undergoing a Doppler shift. When the reflected wave is caught by the oscillation coil 2b of the electromagnetic wave radiation unit 2, it is mixed with a part of the transmission wave to generate a beat (low frequency disturbance), and a low frequency disturbance component is added to the collector voltage of the gallium arsenide FET 2a. The fluctuation of the collector voltage is detected by the collector resistor 2c and input to the disturbance component extraction unit 3 through the DC cut capacitor 2d. The disturbance component extraction unit 3 amplifies the input voltage, limits the band, extracts the disturbance component, and outputs the disturbance component to the level comparison unit 5. The level comparison unit 5 compares the input disturbance component with the reference level, and outputs a sensor signal when a disturbance component larger than the reference level is detected.
[0004]
[Problems to be solved by the invention]
However, the conventional electromagnetic proximity detector has a problem that the current consumption for radiating electromagnetic waves of a predetermined output is large because the oscillation coil that also serves as an antenna is connected to the base of the transistor.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide an electromagnetic wave proximity detection device that can reduce current consumption for radiating electromagnetic waves having a predetermined output.
[0006]
It is another object of the present invention to provide an electromagnetic wave proximity detection device that can reduce current consumption for radiating electromagnetic waves having a predetermined output and can improve detection sensitivity.
[0007]
[Means for Solving the Problems]
The electromagnetic wave type proximity detector of the present invention includes a high frequency radiation / reception unit that performs oscillation of a predetermined high frequency, reception of the high frequency electromagnetic wave, and reception of the reflected wave of the electromagnetic wave, and the high frequency radiation / reception. In the electromagnetic wave proximity detecting device including an amplifying unit that extracts and amplifies a low-frequency disturbance component from a current change on the output side of the unit, the high-frequency radiation / receiving unit includes a transistor and an output side terminal of the transistor A first conductor pattern connected to a collector and having a length that resonates at the predetermined frequency; and a base that is an input side terminal of the transistor; and the first conductor pattern and a predetermined And a second conductor pattern having a predetermined length arranged at intervals. With this configuration, the voltage on the collector side of the transistor is fed back to the base side due to the inductance of the first conductor pattern and the stray capacitance between the first conductor pattern and the second conductor pattern. By using the first conductive pattern as an antenna and radiating electromagnetic waves on the collector side of the transistor, current consumption for radiating electromagnetic waves with a predetermined output can be reduced.
[0008]
In the electromagnetic wave proximity detector according to the present invention, the high-frequency radiation / reception unit includes an antenna connected to an emitter of the transistor. With this configuration, the detection sensitivity can be improved by supplying the electromagnetic wave received by the antenna to the emitter of the transistor and extracting the disturbance component on the collector side of the transistor from which a large current change can be extracted.
[0009]
Furthermore, the electromagnetic wave type proximity detector according to the present invention includes a conductor in which the high-frequency radiation / receiving unit is connected between an emitter of the transistor and a ground and has a length that resonates at the predetermined frequency. It is characterized by that. With this configuration, the received electromagnetic wave resonates with the conductor, thereby improving detection sensitivity.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, an electromagnetic wave proximity detector according to an embodiment of the present invention includes a high frequency radiation / wave receiving unit 1, a coupling capacitor 6 that extracts a change in output current of the high frequency radiation / wave receiving unit 1, and a coupling An amplifying unit 7 that extracts and amplifies a predetermined frequency component from the output of the capacitor 6 and a display unit 8 that visually displays the output of the amplifying unit 7 are provided. As will be described in detail later, this electromagnetic proximity detector is mounted on a circuit board made of glass epoxy or the like.
[0011]
The high frequency radiation / wave receiving unit 1 includes a transistor 11. The collector of the transistor 11 is connected to the power supply VDD via a series connection circuit of the first conductor pattern 12 on the circuit board surface and the resistor 13. The emitter of the transistor 11 is connected to the ground via a series connection circuit of a conductor line 21 described later and a semi-fixed resistor 19. A series connection circuit of a resistor 14, a resistor 15, and a diode 16 for supplying a base bias voltage to the transistor 11 is connected between the power supply VDD and the ground. A second conductor pattern 17 on the surface of the circuit board is connected between the base of the transistor 11 and the connection point of the resistors 14 and 15. Further, the third conductor pattern 18 on the back surface of the circuit board forms a capacitor with a stray capacitance between the third conductor pattern 18 and the first conductor pattern 12. The diode 16 performs a temperature drift compensation function of the transistor 11. The semi-fixed resistor 19 is for fine adjustment of the base bias voltage of the transistor 11.
[0012]
The high-frequency radiation / wave receiving unit 1 includes an antenna 20 connected to the emitter of the transistor 11 and a conductor line 21 connected between the emitter of the transistor 11 and the semi-fixed resistor 19. Details of these will be described later.
[0013]
The coupling capacitor 6 is connected to a connection point between the first conductor pattern 12 and the resistor 13. The amplifying unit 7 extracts and amplifies a current change component having a predetermined frequency, for example, 10 Hz or less. The display unit 8 includes a driving transistor 81 to which the output of the amplifying unit 7 is input, and a light emitting diode 82 driven by the transistor 81.
[0014]
FIG. 2 is a view for explaining the configuration of the main part of the circuit board and the mounting state of the components in the electromagnetic wave proximity detection device of the present embodiment. In this figure, the same components as those in FIG. 1 are denoted by the reference numerals used in FIG.
[0015]
As shown in FIG. 2, a first conductor pattern 12 and a second conductor pattern 17 are formed on the surface of the circuit board. These conductor patterns are formed by bonding a copper foil to the surface of a circuit board and etching it. The first conductor pattern 12 functions as an inductance of the oscillation circuit 1 and also functions as an antenna that radiates the electric vibration generated by the oscillation circuit 1 as an electromagnetic wave. The length d1 of the first conductor pattern 12 is set to about ¼ of the wavelength of the radiated electromagnetic wave. The second conductor pattern 17 is arranged in parallel with the first conductor pattern 12. The distance d2 between the second conductor pattern 17 and the first conductor pattern 12, and the length d3 of the portion where the second conductor pattern 17 and the first conductor pattern 12 face each other in parallel. Thus, the value of the capacitance due to the stray capacitance between the second conductor pattern 17 and the first conductor pattern 12 is determined. The third conductor pattern 18 is formed on the back surface of the circuit board. Although not shown, a conductor pattern serving as a ground is formed at an appropriate position on the surface of the circuit board.
[0016]
A transistor 11 is mounted between the vicinity of the lower left end of the first conductor pattern 12 and the lower end of the second conductor pattern 17. The collector C of the transistor 11 is connected to the first conductor pattern 12, and the base B of the transistor 11 is connected to the second conductor pattern 17. Although not shown, an antenna 20 made of a tin-plated steel wire having a diameter of about 0.5 mm is erected on the emitter E of the transistor 11. The length of the antenna 20 is set to about ¼ of the wavelength of the electromagnetic wave, and it becomes a straight whip antenna. With this antenna 20, reception directivity in all directions can be obtained. A conductor line 21 is connected to the emitter E of the transistor 11. The length of the conductor wire 21 is set to about ½ of the wavelength of the electromagnetic wave.
[0017]
Next, the operation of the electromagnetic proximity detector configured as described above will be described in the order of (1) oscillation of the high-frequency radiation / receiver unit 1 and electromagnetic radiation, and (2) proximity detection.
[0018]
(1) Oscillation and Electromagnetic Radiation Operation of the High Frequency Radiation / Reception Unit 1 The high frequency radiation / reception unit 1 is an LC oscillation circuit using an inductance and a capacitance as a feedback circuit. Here, the first conductor pattern 12 serves as an inductance, and the stray capacitance between the first conductor pattern 12 and the second conductor pattern 17 serves as a capacitance. The voltage of the inductance connected to the collector on the output side of the transistor 11 is positively fed back to the base on the input side of the transistor 11 by the stray capacitance, and oscillation is performed. The oscillation frequency includes the length d1 of the first conductor pattern 12 (the inductance is determined by this value), the distance d2 between the second conductor pattern 17 and the first conductor pattern 12, and the second conductivity. This is basically determined by the length d3 (the capacitance is determined by these values) of the part where the body pattern 17 and the first conductor pattern 12 face each other in parallel. The oscillation frequency is preferably set to 2.4 GHz of quasi-microwave (1 to 3 GHz). Electromagnetic radiation is mainly performed by the first conductor pattern 12 connected to the collector of the transistor 11. As described above, by radiating electromagnetic waves on the collector side of the transistor, the current consumption can be reduced as compared with the conventional configuration in which electromagnetic waves are radiated by the oscillation between the base and the emitter if the radiation is the same power.
[0019]
(2) Proximity detection operation When a detection object such as a person approaches a detection area (for example, within about 1.5 m) of the proximity detection device, the light emitting diode 82 of the display unit 8 is turned on. At this time, the collector current of the transistor 11 changes in a sine wave shape according to the approach speed of the detection target. The change in the collector current is extracted by the coupling capacitor 6, amplified by the amplifier 7, and displayed on the display unit 8.
[0020]
The operation at this time is as follows. The electromagnetic waves mainly radiated from the first conductor pattern 12 of the high-frequency radiation / wave receiving unit 1 are reflected by the detection target and received by the antenna 20. When the detection object approaches and the distance between the antenna 20 and the detection object changes, the reflected wave changes, and is received by the antenna 20 and injected into the conductor wire 21. Here, the radiated electromagnetic wave and the received electromagnetic wave are mixed, and a low-frequency disturbance is generated, and a low-frequency disturbance component is added to the voltage of the collector resistor 13. This disturbance component is taken out from the coupling capacitor 6. Since the conductor wire 21 connected to the emitter of the transistor 11 has a length that resonates with the received electromagnetic wave, the electromagnetic wave received by the antenna 20 resonates with the conductor wire 21 and the detection sensitivity is improved.
[0021]
In the above embodiment, the antenna 20 is provided. However, even if the antenna 20 is omitted, the directivity in all directions cannot be obtained, but a detection operation with directivity can be performed. The conductor wire 21 may be a conductor pattern on the circuit board. Further, the length of the first conductor pattern 12 is not limited to about ¼ wavelength, and may be a length that resonates with the oscillation frequency of the high-frequency radiation / receiving unit 1. Similarly, the length of the antenna 21 and the length of the conductor wire 21 may be any length that resonates with the oscillation frequency of the high-frequency radiation / receiving unit 1. Further, the antenna 21 is not limited to a whip antenna, but may be an antenna having another shape.
[0022]
【The invention's effect】
As is apparent from the above description, according to the electromagnetic wave proximity detector of the present invention, the inductance of the first conductor pattern and the stray capacitance between the first conductor pattern and the second conductor pattern. Thus, the voltage on the collector side of the transistor is positively fed back to the base side and oscillated, and the first conductor pattern is used as an antenna to radiate the electromagnetic wave on the collector side of the transistor. The current consumption for radiating can be reduced.
[0023]
In addition, according to the electromagnetic wave type proximity detection device of the present invention, the detection sensitivity is improved by supplying the electromagnetic wave received by the antenna to the emitter of the transistor and extracting the low-frequency disturbance component on the collector side where a large current change can be extracted. Can be made.
[0024]
Furthermore, according to the electromagnetic wave type proximity detector of the present invention, the received electromagnetic wave resonates with the conductor, so that the detection sensitivity can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of an electromagnetic wave proximity detector according to an embodiment of the present invention;
FIG. 2 is a diagram for explaining a configuration of a main part of a circuit board and a mounting state of components in an electromagnetic wave proximity detector according to an embodiment of the present invention.
[Explanation of symbols]
1 High Frequency Radiation / Receiving Unit 6 Coupling Capacitor 7 Amplifying Unit 8 Display Unit
11, 81 transistor
12 First conductor pattern
13, 14, 15, 19 resistance
16 diodes
17 Second conductor pattern
18 Third conductor pattern
20 Antenna
21 Conductor wire
82 Light-emitting diode

Claims (3)

A high frequency radiation / reception unit that oscillates at a predetermined high frequency, radiates the high frequency electromagnetic wave, and receives a reflected wave of the electromagnetic wave, and a low frequency from a current change on the output side of the high frequency radiation / reception unit In the electromagnetic wave proximity detecting device including an amplifying unit that extracts and amplifies a disturbance component, the high-frequency radiation / receiving unit is connected to a transistor and a collector that is an output side terminal of the transistor, and the predetermined unit A first conductor pattern having a length resonating with a frequency, and a predetermined length connected to a base which is an input side terminal of the transistor and arranged at a predetermined interval from the first conductor pattern. An electromagnetic wave proximity detecting device comprising: a second conductive pattern having a second conductive pattern. 2. The electromagnetic wave proximity detector according to claim 1, wherein the high-frequency radiation / reception unit has an antenna connected to an emitter of the transistor. 3. The high-frequency radiation / reception unit includes a conductor connected between an emitter of the transistor and a ground and having a length that resonates at the predetermined frequency. Electromagnetic proximity detector.

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