JP6614684B2 - Electromagnetic wave detection device - Google Patents

Description

  The present invention relates to a technical field of an electromagnetic wave detection device that detects electromagnetic waves.

  As an example of a detection element used in this type of apparatus, Patent Document 1 discloses a detection element including a Schottky barrier diode. Patent Document 1 discloses that, as an operation example of the detection element, a direct current output can be obtained when infrared light (wavelength 10.6 μm) is irradiated with a bias voltage applied to the detection element. ing.

JP-A-9-162424

  The optimum bias voltage of the detection element varies depending on the operating temperature. However, Patent Document 1 does not disclose how to set the bias voltage. If the bias voltage is always fixed, a correct detection result may not be obtained depending on the operating temperature.

  This invention is made | formed in view of the said problem, for example, and makes it a subject to provide the electromagnetic wave detection apparatus which can suppress the influence of a temperature change.

  In order to solve the above-described problem, a first electromagnetic wave detection device of the present invention includes a detection element that generates a current corresponding to the intensity of an incident electromagnetic wave, and the detection when the electromagnetic wave is not incident on the detection element. A voltage holding unit that holds a voltage value of an applied voltage that generates a reference current having a predetermined current value in the detection element by applying to the element, and a voltage value held in the voltage holding unit when the electromagnetic wave is detected. An application circuit that applies a bias voltage set based on the detection element to the detection element; and a calculation unit that calculates a difference between a current value of a current generated in the detection element and the predetermined current value.

  In order to solve the above-described problem, the second electromagnetic wave detection device of the present invention has a detection element that generates a current corresponding to the intensity of an incident electromagnetic wave, the detection element is equivalent in electrical characteristics, and A reference element that does not receive electromagnetic waves, an application circuit that applies a voltage that generates a reference current of a predetermined current value to the reference element as a bias voltage to the detection element, and a current that is generated in the detection element when the electromagnetic wave is detected And a calculation unit that calculates a difference between the current value and the predetermined current value.

  In order to solve the above-described problem, the third electromagnetic wave detection device of the present invention has a detection element that generates a current corresponding to the intensity of an incident electromagnetic wave, the detection element is equivalent in electrical characteristics, and A reference element to which no electromagnetic wave is incident, an application circuit that applies a voltage that generates a reference current of a predetermined current value to the reference element as a bias voltage to the detection element, and (i) the detection element at the time of detection of the electromagnetic wave A calculation unit that calculates a difference between a current value of a generated current and (ii) a current value of a current generated in the detection element when the electromagnetic wave is not incident.

  The effect | action and other gain of this invention are clarified from the form for implementing demonstrated below.

It is a figure which shows an example of a voltage-current characteristic for every intensity | strength of the terahertz wave which injects into a Schottky barrier diode. It is a figure which shows an example of the temperature change of the voltage-current characteristic of a Schottky barrier diode. It is a conceptual diagram which shows the intensity | strength detection method of the terahertz wave using a Schottky barrier diode. It is a figure which shows an example of the principal part of the detection circuit of the terahertz wave intensity detection apparatus which concerns on 1st Example. It is a figure which shows an example of the difference voltage detection part which concerns on 1st Example. It is a figure which shows an example of the principal part of the detection circuit of the terahertz wave intensity detection apparatus which concerns on 2nd Example. It is a figure which shows an example of the principal part of the detection circuit of the terahertz wave intensity detection apparatus which concerns on the 1st modification of 2nd Example. It is a figure which shows an example of the principal part of the detection circuit of the terahertz wave intensity detection apparatus which concerns on the 2nd modification of 2nd Example. It is a figure which shows an example of the principal part of the detection circuit of the terahertz wave intensity detection apparatus which concerns on the 3rd modification of 2nd Example. It is a figure which shows an example of the principal part of the detection circuit of the terahertz wave intensity detection apparatus which concerns on 3rd Example.

<First Embodiment>
The electromagnetic wave detection device according to the first embodiment includes a detection element that generates a current corresponding to the intensity of an incident electromagnetic wave, and a detection element that is applied to the detection element when no electromagnetic wave is incident on the detection element. A voltage holding unit that holds a voltage value of an applied voltage that generates a reference current having a predetermined current value, and a bias voltage that is set based on the voltage value held in the voltage holding unit when detecting an incident electromagnetic wave is used as a detection element. An application circuit for applying, and a calculation unit that calculates a difference between a current value of a current generated in the detection element and a predetermined current value. Here, examples of electromagnetic waves include terahertz waves and millimeter waves. An example of the detection element is a Schottky barrier diode.

  When an electromagnetic wave enters the detection element, a current corresponding to the intensity of the incident electromagnetic wave is generated in the detection element. For this reason, simply, the generated current can be detected, and the intensity of the electromagnetic wave can be obtained from the current value. However, it is difficult to improve detection sensitivity. In order to improve the detection sensitivity, it is conceivable to apply a bias voltage to the detection element. At this time, if the bias voltage is set to a fixed value, the current generated in the detection element changes due to the bias voltage when the operating temperature of the detection element changes. For this reason, a correct detection result may not be obtained depending on the operating temperature of the detection element.

  Therefore, in this embodiment, the voltage holding unit holds in advance the voltage value of the applied voltage that causes the detection element to generate a reference current having a predetermined current value by applying the voltage to the detection element when no electromagnetic wave is incident on the detection element. In addition, the bias voltage set based on the voltage value held in the voltage holding unit is applied to the detection element by the application circuit. That is, in the present embodiment, the bias voltage is set as a variable value so that the reference current generated in the detection element due to the bias voltage has a predetermined current value. For this reason, it is possible to generate a reference current having a predetermined current value in the detection element regardless of the operating temperature of the detection element.

  The difference between the current value of the current generated in the detection element when detecting the electromagnetic wave and the predetermined current value corresponds to the current value of the current generated in the detection element due to the electromagnetic wave incident on the detection element. Since the predetermined current value is hardly or not affected by the change in the operating temperature of the detection element, the electromagnetic wave detection device can suppress the influence of the temperature change on the detection result.

  In one aspect of the electromagnetic wave detection device according to the first embodiment, a switching unit that switches a connection destination of the voltage holding unit is provided, and the switching unit and the detection element when the electromagnetic wave is not incident on the detection element. And the voltage holding unit and the application circuit are electrically connected at the time of detecting the incident electromagnetic wave. According to this aspect, it is possible to use only one detection element and set and apply an appropriate bias voltage to the detection element.

Second Embodiment
The electromagnetic wave detection device according to the second embodiment includes a detection element that generates a current corresponding to the intensity of an incident electromagnetic wave, a reference element that has an electrical characteristic equivalent to that of the detection element and that does not receive an electromagnetic wave, A voltage that generates a reference current having a predetermined current value in the reference element is applied to the detection element as a bias voltage, and a difference between the current value of the current generated in the detection element and the predetermined current value when detecting an electromagnetic wave is calculated. And a calculating unit for calculating. Here, examples of electromagnetic waves include terahertz waves and millimeter waves. An example of the detection element is a Schottky barrier diode.

  Similarly to the electromagnetic wave detection device according to the first embodiment described above, the electromagnetic wave detection device can suppress the influence of the temperature change on the detection result. “Electrical characteristics are equivalent” is a concept that includes not only the case where the electrical characteristics are exactly the same, but also cases where the electrical characteristics are close to each other to the extent that the electrical characteristics can be considered to be practical. The “reference element where no electromagnetic wave is incident” means that no electromagnetic wave is incident on the reference element even when the electromagnetic wave detection device detects the electromagnetic wave.

  In one aspect of the electromagnetic wave detection device according to the second embodiment, the reference element is placed in a thermal environment close to the thermal environment in which the detection element is placed, and is arranged in a shield that blocks electromagnetic waves. According to this aspect, the reference element is shielded from the electromagnetic wave, and an appropriate bias voltage can be applied to the detection element even during the detection of the electromagnetic wave.

  In another aspect of the electromagnetic wave detection device according to the second embodiment, the electromagnetic wave detection device includes a plurality of detection elements, and the application circuit uses a voltage at which a reference current is generated in the reference element as a bias voltage, and the plurality of detection elements. Apply to each. According to this aspect, the electromagnetic wave detection range can be expanded.

<Third Embodiment>
The electromagnetic wave detection device according to the third embodiment includes a detection element that generates a current according to the intensity of an incident electromagnetic wave, a reference element that is equivalent in electrical characteristics to the detection element, and that does not receive an electromagnetic wave, An application circuit for applying a voltage for generating a reference current having a predetermined current value to the reference element as a bias voltage to the detection element; (i) a current value of a current generated in the detection element when detecting the electromagnetic wave; and (ii) an electromagnetic wave. And a calculation unit that calculates a difference between the current value of the current generated in the detection element when no is incident. Here, examples of electromagnetic waves include terahertz waves and millimeter waves. An example of the detection element is a Schottky barrier diode.

  Similarly to the electromagnetic wave detection device according to the second embodiment described above, the electromagnetic wave detection device can suppress the influence of the temperature change on the detection result. Furthermore, even when there is a minute characteristic difference between the electrical characteristics of the reference element and the detection element, the influence of the characteristic difference on the accuracy of electromagnetic wave intensity detection can be suppressed.

  In one aspect of the electromagnetic wave detection device according to the third embodiment, the reference element is placed in a thermal environment close to the thermal environment in which the detection element is placed, and is arranged in a shield that blocks electromagnetic waves. According to this aspect, the reference element is shielded from the electromagnetic wave, and an appropriate bias voltage can be applied to the detection element even during the detection of the electromagnetic wave.

  In another aspect of the electromagnetic wave detection device according to the third embodiment, a plurality of detection elements are provided, and the application circuit applies a voltage at which the reference current is generated in the reference element to each of the plurality of detection elements as a bias voltage, and calculates The unit detects a plurality of differences between (i) the current value of the current generated in the detection element during detection of the electromagnetic wave and (ii) the current value of the current generated in the detection element when no electromagnetic wave is incident. Calculate for each of the elements. According to this aspect, the electromagnetic wave detection range can be expanded.

  Embodiments of the electromagnetic wave detection device of the present invention will be described with reference to the drawings. In the following examples, a “terahertz wave intensity detection device” is cited as an example of an “electromagnetic wave detection device” according to the present invention. An example of the “electromagnetic wave” according to the present invention is “terahertz wave”.

<First embodiment>
A first embodiment of the terahertz wave intensity detection device will be described with reference to FIGS. In the terahertz wave intensity detection device 1 according to the first embodiment, a Schottky barrier diode is used as a terahertz wave detection element.

(Schottky barrier diode)
First, the features of the Schottky barrier diode and the outline of each terahertz wave intensity detection method using the Schottky barrier diode will be described with reference to FIGS. FIG. 1 is a diagram illustrating an example of voltage-current characteristics for each intensity of a terahertz wave incident on a Schottky barrier diode. FIG. 2 is a diagram illustrating an example of a temperature change of the voltage-current characteristic of the Schottky barrier diode. FIG. 3 is a conceptual diagram showing a terahertz wave intensity detection method using a Schottky barrier diode.

  As shown in FIG. 1, as the intensity of the terahertz wave incident on the Schottky barrier diode decreases, the current generated in the Schottky barrier diode also decreases. In particular, when a bias voltage is not applied to the Schottky barrier diode (see the broken line indicating voltage 0 in FIG. 1), when the intensity of the incident terahertz wave becomes weak, the current generated in the Schottky barrier diode approaches 0, Terahertz wave intensity cannot be detected.

  By applying a bias voltage to the Schottky barrier diode, even if the intensity of the terahertz wave incident on the Schottky barrier diode is weak, a detectable current can be generated in the Schottky barrier diode (in FIG. 1). (See broken line showing voltage V).

  However, as shown in FIG. 2, the voltage-current characteristic of the Schottky barrier diode has temperature dependence. For this reason, if the bias voltage is fixed, even if no terahertz wave is incident on the Schottky barrier diode, the current generated in the Schottky barrier diode changes due to a temperature change (voltage) V and currents I1, I2 and I3).

  Here, a terahertz wave intensity detection method will be described with reference to FIG. When a voltage Vf is applied as a bias voltage to the Schottky barrier diode and no terahertz wave is incident on the Schottky barrier diode, a current generated in the Schottky barrier diode is defined as a current If.

  Assuming that the current generated in the Schottky barrier diode when the terahertz wave is incident on the Schottky barrier diode is the current Its, the difference Isig between the current Its and the current If is the current increased due to the terahertz wave. Become. As described above, the current flowing through the Schottky barrier diode also changes according to the intensity of the terahertz wave incident on the Schottky barrier diode. For this reason, the intensity of the terahertz wave can be detected from the difference Isig between the current Its and the current If.

  As shown in FIG. 2, if the current generated in the Schottky barrier diode changes when the terahertz wave is not incident due to a temperature change, the intensity of the terahertz wave cannot be detected correctly. .

  The “voltage Vf” according to the present embodiment is a forward voltage applied to both ends of the Schottky barrier diode, and the voltage for turning on the Schottky barrier diode, that is, the forward current of the Schottky barrier diode is abruptly increased. The voltage starts to increase. More specifically, the “voltage Vf” is used to pass a current If which is a small forward current through the Schottky barrier diode when no terahertz wave is incident on the Schottky barrier diode. Means a forward voltage to be applied to both ends.

(Terahertz wave intensity detector)
The terahertz wave intensity detection device 1 according to the present embodiment is configured so that the current generated in the Schottky barrier diode as the detection element is not affected by the temperature change when no terahertz wave is incident. .

  The terahertz wave intensity detection device 1 has a circuit shown in FIG. In FIG. 4, “D1” is a Schottky barrier diode as a detection element, “C1” is a capacitor, “OA1” is an operational amplifier, “BA1” and “BA2” are buffer amplifiers, SW1 "and" SW2 "are switches.

  The terahertz wave intensity detection device 1 generates a predetermined current value If (fixed value) in the Schottky barrier diode D1 when the terahertz wave is not incident on the Schottky barrier diode D1 at least before measurement of the terahertz wave. Thus, the bias voltage is set (or adjusted).

  Specifically, as shown in FIG. 4A, the terminal 1a is selected in the switch SW1, and the terminal 2a is selected in the switch SW2. In a state where no terahertz wave is incident on the Schottky barrier diode D1, a voltage Vf (variable value) generated at the Schottky barrier diode D1 with a predetermined current value If is applied to the Schottky barrier diode D1. The potential of the positive electrode of the DC power supply is set to “V1”. Here, the potential V1 can be expressed as “V1 = If × R1 + Vf” where the resistance value is R1. At this time, since the terminal 2a is selected in the switch SW2, the potential difference (voltage) between the plates of the capacitor C1 is “Vf”.

  At the time of measuring the terahertz wave, as shown in FIG. 4B, the terminal 1b is selected in the switch SW1, and the terminal 2b is selected in the switch SW2. As a result, the negative input terminal of the operational amplifier OA1 and the output terminal of the operational amplifier OA1 are electrically connected (that is, virtual ground). For this reason, the potential V− of the negative input terminal of the operational amplifier OA1 and the potential V + of the positive input terminal of the operational amplifier OA1 are the same potential. Here, since the potential difference between the plates of the capacitor C1 is “Vf”, both the potential V + and the potential V− are “Vf”. Accordingly, the voltage Vf is applied as a bias voltage to the Schottky barrier diode D1.

  When the current generated in the Schottky barrier diode D1 when the terahertz wave is incident on the Schottky barrier diode D1 is “Its”, the potential V2 of the output terminal of the operational amplifier OA1 can be expressed as “V2 = Its × R1 + Vf”. The potential of the positive input terminal of the differential voltage detector is “V2”, and the potential of the negative input terminal of the differential voltage detector is “V1”. A signal indicating “V2−V1 = Its × R1 + Vf− (If × R1 + Vf) = Its × R1−If × R1 = Isig × R1” is output from the differential voltage detection unit. Since the resistance value R1 is known, the intensity of the terahertz wave incident on the Schottky barrier diode D1 is detected from the output of the differential voltage detector.

(Technical effect)
Before the terahertz wave is measured (and during measurement), the state shown in FIG. 4A and the state shown in FIG. 4B are switched to apply an appropriate bias voltage to the Schottky barrier diode D1. be able to. As a result, the current generated in the Schottky barrier diode D1 when no terahertz wave is incident can be set to the predetermined current value If. Therefore, the influence of the temperature change on the detection result of the terahertz wave intensity detection device 1 can be suppressed.

  The “Schottky barrier diode D 1”, “capacitor C 1”, “operational amplifier OA 1”, “switch SW 2”, and “difference voltage detection unit” according to the embodiment are respectively “detection element” and “voltage holding unit” according to the present invention. , “Application circuit”, “switching unit”, and “calculation unit”.

<Second embodiment>
A second embodiment of the terahertz wave intensity detection device will be described with reference to FIG. The second embodiment is the same as the first embodiment described above except that a part of the configuration of the terahertz wave intensity detection device is different. Therefore, in the second embodiment, the description overlapping with that of the first embodiment is omitted, and common portions in the drawing are denoted by the same reference numerals, and only different points are basically described with reference to FIG. To do. FIG. 6 is a diagram illustrating an example of a main part of a detection circuit of the terahertz wave intensity detection device according to the second embodiment.

(Terahertz wave intensity detector)
The terahertz wave intensity detection device 2 has a circuit shown in FIG. In FIG. 6, “D2” is a Schottky barrier diode, “D3” is a Schottky barrier diode as a detection element, and “OA2” is an operational amplifier. The Schottky barrier diode D2 is covered with a shield made of a conductor that shields terahertz waves.

  Particularly in this embodiment, the electrical characteristics of the Schottky barrier diode D2 and the electrical characteristics of the Schottky barrier diode D3 are equivalent. In addition, the Schottky barrier diode D2 is placed in a thermal environment close to the thermal environment in which the Schottky barrier diode D3 is placed.

  In the terahertz wave intensity detection device 2, during measurement of the terahertz wave, the voltage Vf is applied as a bias voltage so that the predetermined current value If is generated in the Schottky barrier diode D2. Specifically, the resistance value between the positive electrode of the DC power supply and the positive input terminal of the operational amplifier OA2 is “R2”, and the potential of the positive electrode of the DC power supply is set to “V1 = If × R2 + Vf”.

  As shown in FIG. 6, since the negative input terminal of the operational amplifier OA2 and the output terminal of the operational amplifier OA2 are electrically connected, the potential V− of the negative input terminal of the operational amplifier OA2 and the positive input of the operational amplifier OA2 The potential V + of the terminal becomes the same potential. Since the potential V + is “Vf”, the potential V− is also “Vf”.

  Therefore, the voltage Vf is applied as a bias voltage to the Schottky barrier diode D3 as the detection element. Since the electrical characteristics of the Schottky barrier diode D3 are equivalent to the electrical characteristics of the Schottky barrier diode D2, as described above, the Schottky barrier diode D3 has a predetermined current value If when no terahertz wave is incident. Occurs.

  When a terahertz wave is incident on the Schottky barrier diode D3, the current generated in the Schottky barrier diode D3 is “Its”, and the resistance value between the output terminal of the operational amplifier OA2 and the negative input terminal of the operational amplifier OA2 is “R2”. ". The potential V2 of the output terminal of the operational amplifier OA2 can be expressed as “V2 = Its × R2 + Vf”. The potential of the positive input terminal of the differential voltage detector is “V2”, and the potential of the negative input terminal of the differential voltage detector is “V1”.

(Technical effect)
In this embodiment, in particular, the current generated in the Schottky barrier diode D3 when no terahertz wave is incident can always be set to the predetermined current value If. Therefore, the influence of the temperature change on the detection result of the terahertz wave intensity detection device 2 can be suppressed.

  The “Schottky barrier diode D3” and the “operational amplifier OA2” according to the embodiment are other examples of the “detection element” and the “application circuit” according to the present invention. The “Schottky barrier diode D2” according to the embodiment is an example of the “reference element” according to the present invention.

<First Modification>
A first modification of the terahertz wave intensity detection device according to the second embodiment will be described with reference to FIG. FIG. 7 is a diagram illustrating an example of a main part of the detection circuit of the terahertz wave intensity detection device according to the first modification of the second embodiment.

(Terahertz wave intensity detector)
The terahertz wave intensity detection device 3 has a circuit shown in FIG. In FIG. 7, “OA3” and “OA4” are operational amplifiers. In the terahertz wave intensity detection device 3, the resistance value between the positive electrode of the DC power supply and the negative input terminal of the operational amplifier OA4 is “R2”, and the potential of the positive electrode of the DC power supply is set to “V3 = If × R2”. The

  As shown in FIG. 7, since the negative input terminal of the operational amplifier OA4 and the output terminal of the operational amplifier OA4 are electrically connected, the potential V− of the negative input terminal of the operational amplifier OA4 and the positive input of the operational amplifier OA4. The terminal potential V + becomes the same potential (here, the ground potential).

  As shown in FIG. 7, a Schottky barrier diode D2 is arranged between the negative input terminal of the operational amplifier OA4 and the output terminal of the operational amplifier OA4. The Schottky barrier diode D2 has a predetermined current value If. Flows. Therefore, the voltage Vf that generates the predetermined current value If is applied as a bias voltage to the Schottky barrier diode D2.

  As described above, since the potential V− of the negative input terminal of the operational amplifier OA4 (that is, the potential V1 on the anode side of the Schottky barrier diode D2) is the ground potential, the potential V4 of the output terminal of the operational amplifier OA4 (in other words, The potential on the cathode side of the Schottky barrier diode D2 is “−Vf”. Accordingly, the potential on the cathode side of the Schottky barrier diode D3 is also “−Vf”.

  As shown in FIG. 7, since the negative input terminal of the operational amplifier OA3 and the output terminal of the operational amplifier OA3 are electrically connected, the potential V− of the negative input terminal of the operational amplifier OA3 and the positive input of the operational amplifier OA3. The potential V + of the terminal becomes the same potential. Here, since the potential V + of the positive input terminal of the operational amplifier OA3 is equal to the potential V1 on the anode side of the Schottky barrier diode D2, it is a ground potential. As a result, the potential V− of the negative input terminal of the operational amplifier OA3, in other words, the potential V2 on the anode side of the Schottky barrier diode D3 also becomes the ground potential. That is, the voltage Vf is applied as a bias voltage to the Schottky barrier diode D3.

  When a terahertz wave enters the Schottky barrier diode D3, a current Its (Its> If) is generated in the Schottky barrier diode D3. At this time, the current flowing through the resistor (resistance value R3) between the negative input terminal of the operational amplifier OA3 and the output terminal of the operational amplifier OA3 becomes “Its-If” according to Kirchhoff's law, and the output of the circuit shown in FIG. The voltage is “(Its−If) × R3 = Isig × R3”.

<Second Modification>
A second modification of the terahertz wave intensity detection device according to the second embodiment will be described with reference to FIG. FIG. 8 is a diagram illustrating an example of a main part of a detection circuit of a terahertz wave intensity detection device according to a second modification of the second embodiment.

  In the first modification of the second embodiment described above, the terahertz wave is detected only by the Schottky barrier diode D3. As shown in FIG. 8, the terahertz wave intensity detection device 4 according to this modification includes a plurality of Schottky barrier diodes as detection elements.

<Third Modification>
A third modification of the terahertz wave intensity detection device according to the second embodiment will be described with reference to FIG. FIG. 9 is a diagram illustrating an example of a main part of a detection circuit of a terahertz wave intensity detection device according to a third modification of the second embodiment.

(Terahertz wave intensity detector)
The terahertz wave intensity detection device 5 has a circuit shown in FIG. In FIG. 9, “OA3” and “OA5” are operational amplifiers. In the terahertz wave intensity detection device 5, the negative input terminal of the operational amplifier OA5 and the output terminal of the operational amplifier OA5 are electrically connected. The input terminal potential V + becomes the same potential (here, the ground potential).

  Since the negative input terminal of the operational amplifier OA3 and the output terminal of the operational amplifier OA3 are electrically connected, the potential V− of the negative input terminal of the operational amplifier OA3 and the potential V + of the positive input terminal of the operational amplifier OA3 are Become the same potential. Here, since the potential V + of the positive input terminal of the operational amplifier OA3 is equal to the potential V− of the negative input terminal of the operational amplifier OA5, the potential V + of the positive input terminal of the operational amplifier OA3 is a ground potential. Accordingly, the potential V− of the negative input terminal of the operational amplifier OA3 is also the ground potential.

  As shown in FIG. 7, the Schottky barrier diodes D2 and D3 are electrically connected in series. When no terahertz wave is incident on the Schottky barrier diode D3, the Schottky barrier diodes D2 and D3 are used. The same current flows through. Therefore, the relationship between the cathode-side potential V4 of the Schottky barrier diode D2 and the anode-side potential V3 of the Schottky barrier diode D3 is “V4 = −V3” (the electrical characteristics of the Schottky barrier diode D2). And the electrical characteristics of the Schottky barrier diode D3 are equivalent).

  If the resistance value of the resistor between the negative input terminal of the operational amplifier OA5 and the output terminal of the operational amplifier OA5 is “R2” and the current value flowing through the resistor is “Ir”, the potential V3 of the output terminal of the operational amplifier OA5 (ie, The potential V3 on the anode side of the Schottky barrier diode D3 is “V3 = Ir × R2”. The potential V4 on the cathode side of the Schottky barrier diode D2 is “V4 = −V3 = −Ir × R2”.

  The current generated in the Schottky barrier diode D2 (further, the Schottky barrier diode D3 when no terahertz wave is incident) needs to be set to the predetermined current value If. When the current generated in the Schottky barrier diode D2 is the predetermined current value If, the potential difference between the anode and the cathode of the Schottky barrier diode D2 is “Vf”. As a result, the potential V4 = −Vf and the potential V3 = Vf. Therefore, the voltage Vf is applied as a bias voltage to the Schottky barrier diode D3.

  In the terahertz wave intensity detection device 5, the current value I1 is controlled so that the current generated in the Schottky barrier diode D2 becomes the predetermined current value If at least before the measurement of the terahertz wave.

  When a terahertz wave enters the Schottky barrier diode D3, a current Its (Its> If) is generated in the Schottky barrier diode D3. At this time, the current flowing through the resistance (resistance value R3) between the negative input terminal of the operational amplifier OA3 and the output terminal of the operational amplifier OA3 becomes “Its-If” according to Kirchhoff's law, and the output of the circuit shown in FIG. The voltage is “(Its−If) × R3 = Isig × R3”.

<Third embodiment>
A third embodiment of the terahertz wave intensity detection device will be described with reference to FIG. The third embodiment is the same as the second embodiment described above except that a part of the configuration of the terahertz wave intensity detection device is different. Therefore, the description of the third embodiment that is the same as that of the second embodiment is omitted, and common portions in the drawing are denoted by the same reference numerals, and only differences are basically described with reference to FIG. To do. FIG. 10 is a diagram illustrating an example of a main part of a detection circuit of the terahertz wave intensity detection device according to the third embodiment.

(Terahertz wave intensity detector)
The terahertz wave intensity detection device 3 which is the first modification of the second embodiment described above is the reference element and the current Its that the operational amplifier OA3 flows to the Schottky barrier diode D3 that is the detection element when the terahertz wave is detected. A voltage corresponding to the difference from the predetermined current value If flowing through the Schottky barrier diode D2 is output. Here, the electrical characteristics of the Schottky barrier diode D2 and the electrical characteristics of the Schottky barrier diode D3 are equivalent, but if there is a small characteristic difference between them, the terahertz wave intensity detection accuracy will be affected. It will be. Therefore, the terahertz wave intensity detection device 6 of the present embodiment stores the value of the current If1 generated in the Schottky barrier diode D3 when no terahertz wave is incident before starting detection of the terahertz wave, When the terahertz wave is detected, the difference between the stored current If1 and the current Its1 flowing through the Schottky barrier diode D3 is calculated and output.

  The terahertz wave intensity detection device 6 includes a calculation unit 1 including an AD converter and a memory, instead of the operational amplifier OA3 of the first modification. An ammeter A1 for measuring the current flowing through the Schottky barrier diode D3 is inserted in series with the Schottky barrier diode D3. The ammeter A1 preferably has a low internal resistance, and may be composed of an electronic circuit or the like.

  The ammeter A1 supplies a voltage corresponding to each of the current If1 generated in the Schottky barrier diode D3 when no terahertz wave is incident and the current Its1 flowing in the Schottky barrier diode D3 when the terahertz wave is detected to the arithmetic unit 1. Output. The calculation unit 1 performs AD conversion on the voltage output from the ammeter A1, stores information on the current If1 in a memory, obtains information on the current Its1, and then calculates a difference between the current If1 and the current Its1. Output as information corresponding to terahertz wave intensity.

  Furthermore, as shown in FIG. 10, the terahertz wave intensity detection device 6 according to the present embodiment includes a plurality of Schottky barrier diodes, ammeters, and arithmetic units as detection elements, and each terahertz wave is detected for each detection element. The difference between the current value of the current generated at the time of detection and the current value of the current generated when no terahertz wave is incident is output as a detected value of the terahertz wave intensity in each detection element.

(Technical effect)
In the present embodiment, in particular, even when a small characteristic difference exists in the electrical characteristics of each Schottky barrier diode, the influence of the characteristic difference on the accuracy of terahertz wave intensity detection can be suppressed.

  The “calculation unit 1” according to the present embodiment is another example of the “calculation unit” according to the present invention.

  All the terahertz wave intensity detection devices according to the above-described embodiments detect the intensity of the terahertz wave, but may detect the intensity of the millimeter wave.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and an electromagnetic wave detection device with such a change is also included. Moreover, it is included in the technical scope of the present invention.

1, 2, 3, 4, 5, 6 ... terahertz wave intensity detector C1 ... capacitor (voltage holding unit)
D1, D3 ... Schottky barrier diode (detection element)
D2 ... Schottky barrier diode (reference element)
OA1, OA2, OA4, OA5... Operational amplifier (application circuit)
SW2 ... switch (switching part)

Claims (11)

A detection element that generates a current according to the intensity of the incident electromagnetic wave;
A voltage holding unit that holds a voltage value of an applied voltage that causes the detection element to generate a reference current of a predetermined current value by applying to the detection element when the electromagnetic wave is not incident on the detection element;
An application circuit that applies a bias voltage set based on a voltage value held in the voltage holding unit to the detection element when the electromagnetic wave is detected;
A calculation unit for calculating a difference between a current value of a current generated in the detection element and the predetermined current value;
An electromagnetic wave detection apparatus comprising: A switching unit for switching the connection destination of the voltage holding unit;
The switching unit electrically connects the voltage holding unit and the detection element when the electromagnetic wave is not incident on the detection element, and when detecting the electromagnetic wave, the voltage holding unit and the application circuit The electromagnetic wave detection device according to claim 1, wherein the electromagnetic wave detection device is electrically connected. The electromagnetic wave is a terahertz wave or a millimeter wave,
The electromagnetic wave detection device according to claim 1, wherein the detection element is a Schottky barrier diode. A detection element that generates a current according to the intensity of the incident electromagnetic wave;
A reference element having electrical characteristics equivalent to those of the detection element and not receiving the electromagnetic wave;
An application circuit that applies a voltage that generates a reference current of a predetermined current value to the reference element to the detection element as a bias voltage;
A calculation unit that calculates a difference between a current value of a current generated in the detection element at the time of detection of the electromagnetic wave and the predetermined current value;
An electromagnetic wave detection apparatus comprising:   The electromagnetic wave detection according to claim 4, wherein the reference element is placed in a thermal environment close to a thermal environment in which the detection element is placed, and is disposed in a shield that blocks the electromagnetic wave. apparatus. A plurality of the detection elements;
The electromagnetic wave detection apparatus according to claim 4, wherein the application circuit applies a voltage generated by the reference current to the reference element as a bias voltage to each of the plurality of detection elements. The electromagnetic wave is a terahertz wave or a millimeter wave,
The electromagnetic wave detection device according to claim 4, wherein the detection element is a Schottky barrier diode. A detection element that generates a current according to the intensity of the incident electromagnetic wave;
A reference element having electrical characteristics equivalent to those of the detection element and not receiving the electromagnetic wave;
An application circuit that applies a voltage that generates a reference current of a predetermined current value to the reference element to the detection element as a bias voltage;
(I) calculating a difference between a current value of a current generated in the detection element at the time of detection of the electromagnetic wave and (ii) a current value of a current generated in the detection element when the electromagnetic wave is not incident. A calculation unit;
An electromagnetic wave detection apparatus comprising:   The electromagnetic wave detection according to claim 8, wherein the reference element is placed in a thermal environment close to a thermal environment where the detection element is placed, and is disposed in a shield that blocks the electromagnetic wave. apparatus. A plurality of the detection elements;
The application circuit applies a voltage at which the reference current is generated in the reference element as a bias voltage to each of the plurality of detection elements,
(I) The calculation unit includes a current value of a current generated in the detection element when the electromagnetic wave is detected, and (ii) a current value of a current generated in the detection element when the electromagnetic wave is not incident, The electromagnetic wave detection apparatus according to claim 9, wherein the difference between the plurality of detection elements is calculated for each of the plurality of detection elements. The electromagnetic wave is a terahertz wave or a millimeter wave,
The electromagnetic wave detection device according to claim 8, wherein the detection element is a Schottky barrier diode.

Images