Electromagnetic wave transmitting apparatus

Abstract

The electromagnetic wave transmission device of the present invention can increase the transmission speed.SOLUTION: And a modulation unit that modulates an acquired digital signal into the modulation signal using first voltage values of two or more levels in a first voltage region equal to or higher than a voltage of the maximum value and equal to or lower than a voltage of the minimum value, a second voltage value in a second voltage region lower than the voltage of the maximum value, and a third voltage value in a third voltage region on a higher voltage side than the voltage of the minimum value. A first signal that transitions from an arbitrary voltage value of the first voltage region to any one voltage value of the first voltage value via the second voltage value and a second signal that transitions from the arbitrary voltage value to the any one voltage value via the third voltage value are the same signal, and the modulation unit selects a signal having a smaller total transition potential difference between the first signal and the second signal.SELECTED DRAWING: Figure 6A

Description

[Technical Field]

[0001] The present invention relates to an electromagnetic wave transmitting device. [Background technology]

[0002] Amplitude-shift keying (hereinafter referred to as ASK) is a known modulation method for communication used in oscillator elements for transmitting electromagnetic waves. On-off keying (hereinafter referred to as OOK) is also known as a modulation method for communication, and is included in the ASK modulation method.

[0003] Here, Patent Document 1 discloses a technology relating to an ASK modulation method using a resonant tunneling diode (hereinafter referred to as an RTD) as an oscillation element for transmitting electromagnetic waves. Specifically, this technology is a technology that expresses two values ​​by switching between data in the oscillation region of the RTD (e.g., a signal corresponding to On) and data in the non-oscillation region (e.g., a signal corresponding to Off), that is, a technology that expresses On and Off by differences in amplitude. Furthermore, Patent Document 2 discloses a technology relating to an ASK modulation method using continuous wave terahertz waves from an RTD or the like. Specifically, this technology is a technology in which variable light with a variable intensity is incident on a modulation element as signal light in a superimposed manner, and the amplitude of the terahertz wave is modulated according to the signal intensity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-191520 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-41204 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the techniques disclosed in Patent Documents 1 and 2 are techniques that express binary values ​​by differences in amplitude, and therefore there is a limit to how fast the transmission speed (or communication speed) can be increased.

[0006] One example of a problem that the present invention aims to solve is increasing the transmission speed. [Means for solving the problem]

[0007] The invention described in claim 1 is a transmitter that transmits an electromagnetic wave representing a modulated signal, the voltage-current characteristic of which has a maximum value and a minimum value located on a higher voltage side than the maximum value; an acquisition unit that acquires a digital signal; a modulation unit that modulates the digital signal into the modulated signal using a first voltage value of two or more levels in a first voltage range that is a voltage range equal to or higher than the maximum voltage and equal to or lower than the minimum voltage, a second voltage value in a second voltage range that is a voltage range lower than the maximum voltage, and a third voltage value in a third voltage range that is a voltage range higher than the minimum voltage; Equipped with a first signal that transitions from an arbitrary voltage value among two or more first voltage values ​​in the first voltage region via the second voltage value to any one of the two or more voltage values ​​of the first voltage value, and a second signal that transitions from the arbitrary voltage value to the any one voltage value via the third voltage value are the same signal; When a total transition potential difference of the first signal and a total transition potential difference of the second signal are different, the modulation unit selects one of the first signal and the second signal, which has a smaller total transition potential difference of the modulation signal. It is an electromagnetic wave transmitting device. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an electromagnetic wave communication system according to an embodiment of the present invention. [Figure 2A] 1 is a schematic diagram of an electromagnetic wave transmitting device according to an embodiment of the present invention. [Figure 2B] 3 is a detailed configuration diagram of a synchronization signal level conversion unit included in the electromagnetic wave transmission device of the present embodiment. FIG. [Figure 3] 4 is a graph showing the voltage-current characteristics and five levels of voltage values ​​of an element that oscillates an electromagnetic wave and is provided in the electromagnetic wave transmission device of the present embodiment. [Figure 4] 1 shows a first example of modulated signals (modulated signals Vsync1, Vsync2, Vsync3) transmitted by the electromagnetic wave transmission device of the present embodiment. [Figure 5] 10 shows a second example of modulated signals (modulated signals Vsync4 and Vsync5) transmitted by the electromagnetic wave transmission device of the present embodiment. [Figure 6A] 10 is a third example (modulated signal Vsync6) of a modulated signal transmitted by the electromagnetic wave transmission device of the present embodiment. [Figure 6B] 10 is a first comparative example (modulated signal Vsync7) of a modulated signal transmitted by an electromagnetic wave transmission device of a comparative embodiment. [Figure 7A] 10 is a fourth example (modulated signal Vsync8) of a modulated signal transmitted by the electromagnetic wave transmission device of the present embodiment. [Figure 7B] 10 is a second comparative example (modulated signal Vsync9) of a modulated signal transmitted by an electromagnetic wave transmission device of a comparative embodiment. [Figure 8A] 10 is a fifth example (modulated signal Vsync10) of a modulated signal transmitted by the electromagnetic wave transmission device of the present embodiment. [Figure 8B] 10 is a third comparative example of a modulated signal (modulated signal Vsync11) transmitted by an electromagnetic wave transmission device of a comparative embodiment. [Figure 9A] 1 is a diagram showing a first example of the relationship between a graph showing the voltage-current characteristics of an element that oscillates an electromagnetic wave and is provided in the electromagnetic wave transmission device of the present embodiment, and a graph showing the voltage-output level characteristics. [Figure 9B] 10 is a diagram showing a second example of the relationship between a graph showing the voltage-current characteristics of an element that oscillates an electromagnetic wave and is provided in the electromagnetic wave transmission device of the present embodiment, and a graph showing the voltage-output level characteristics. FIG. [Figure 9C]10 is a diagram showing a third example of the relationship between a graph showing the voltage-current characteristics of an element that oscillates an electromagnetic wave and is provided in the electromagnetic wave transmission device of the present embodiment, and a graph showing the voltage-output level characteristics. FIG. [Figure 9D] 10 is a diagram showing a fourth example of the relationship between a graph showing the voltage-current characteristics of an element that oscillates an electromagnetic wave and is provided in the electromagnetic wave transmission device of the present embodiment, and a graph showing the voltage-output level characteristics. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Summary> This embodiment (one example of the present invention) will now be described. First, the function and configuration of an electromagnetic wave communication system 10 (see FIG. 1) of this embodiment will be described with reference to the drawings. Next, the operation of the electromagnetic wave communication system 10 of this embodiment will be described with reference to the drawings. The effects of this embodiment will be explained in the explanation of the operation. Furthermore, in all drawings referred to in this specification, components having similar functions will be assigned similar reference numerals, and explanations thereof will be omitted in the specification as appropriate.

[0010] <Configuration> 1 is a schematic diagram of an electromagnetic wave communication system 10 according to this embodiment. The electromagnetic wave communication system 10 includes an electromagnetic wave transmitting device 20 and an electromagnetic wave receiving device 30. The electromagnetic wave communication system 10 has a function of receiving, by the electromagnetic wave receiving device 30, electromagnetic waves W transmitted by the electromagnetic wave transmitting device 20.

[0011] The electromagnetic wave W in this embodiment is an electromagnetic wave representing a modulation signal, which will be described later. Furthermore, as an example, the electromagnetic wave W in this embodiment is a terahertz wave. Here, terahertz waves are electromagnetic waves with wavelengths shorter than millimeter waves and longer than infrared rays. Terahertz waves are electromagnetic waves that possess the properties of both light waves and radio waves, and have the property of being able to pass (or easily pass) through, for example, cloth, paper, wood, plastic, ceramics, etc., but not (or difficult to pass) through metal, water, etc. Generally, the frequency of terahertz waves is said to be around 1 THz (corresponding to a wavelength of around 300 μm), but there is no clear definition of this range. Therefore, in this specification, the wavelength range of terahertz waves is defined as being between 70 GHz and 10 THz.

[0012] [Electromagnetic wave transmitting device] 2A is a schematic diagram of an electromagnetic wave transmission device 20 according to this embodiment. The electromagnetic wave transmission device 20 has a function of transmitting an electromagnetic wave W representing a multi-level modulated signal. The electromagnetic wave transmission device 20 includes, for example, an acquisition unit 22, a conversion unit 24 (an example of a modulation unit), a switching unit 26A, a selector 26B, a transmission unit 28, a multi-level level setting unit 29A, and a synchronization level setting unit 29B.

[0013] (Acquisition Department) The acquisition unit 22 of this embodiment has a function of acquiring digital signals such as sound, video, etc. The acquisition unit 22 also has a function of outputting the acquired digital signals to the conversion unit 24.

[0014] (Conversion section) The conversion section 24 of this embodiment includes, for example, a multi-level conversion section 24A and a synchronization signal level conversion section 24B. The multi-level conversion unit 24A has a function of receiving a digital signal (communication data) from the acquisition unit 22 as input, converting it into a multi-level signal according to a multi-level setting, and outputting the converted signal. Here, the multi-level setting refers to the setting of two or more voltage levels (first voltage values ​​V2, V3, V4) in a first voltage region RA (described later), a voltage level (second voltage value V1) in a second voltage region RB (described later), and a voltage level (third voltage value V5) in a third voltage region (described later) (see FIG. 3). The synchronization signal level converter 24B has a function of outputting a predetermined synchronization signal level in accordance with a synchronization level setting, which means setting two or more voltage levels in the first voltage region RA, a voltage level in the second voltage region RB, and a voltage value level in the third voltage region (see FIG. 3). 2B is a detailed configuration diagram of the multi-level conversion unit 24A of this embodiment. The multi-level conversion unit 24A has a multi-level conversion unit 24B1, a multi-level extension unit 24B2, and a voltage conversion unit 24B3. Details of the multi-level conversion unit 24B1, the multi-level extension unit 24B2, and the voltage conversion unit 24B3 will be described later. The synchronization signal level conversion section 24B of this embodiment has the same configuration as that shown in FIG. 2B.

[0015] (Switching and selection section) The switching unit 26A has a function of generating switching timing for data selected by the selector 26B and output to the transmitting unit 28, and inputting the generated timing to the selector 26B. Here, the data in question is data output by the multi-level conversion unit 24A (hereinafter referred to as multi-level data) and data output by the synchronization signal level conversion unit 24B (hereinafter referred to as synchronization signal data). The selector 26B has a function of outputting the synchronization signal data and the multi-level data to the transmitter 28 at different timings in accordance with the switching timing of the data generated by the switching unit 26A.

[0016] (Transmitter) The transmitter 28 has a function of oscillating the data selected and input by the selector 26B as electromagnetic waves W (in the present embodiment, terahertz waves are used as an example). Therefore, the transmitter 28 has an element that oscillates terahertz waves. In the present embodiment, the element that oscillates terahertz waves is an RTD as an example. However, the element does not have to be an RTD as long as it oscillates terahertz waves.

[0017] The voltage-current characteristics of an RTD will now be described with reference to the graph in Figure 3. Here, "voltage-current characteristics" refers to the characteristics of current relative to voltage in a two-dimensional graph showing the relationship between voltage and current. FIG. 3 is a graph showing the voltage-current characteristics of the RTD of this embodiment, as well as three levels of first voltage values ​​V2, V3, and V4 in the first voltage region RA, the second voltage value V1 in the second voltage region RB, and the third voltage value V5 in the third voltage region RC. The voltage-current characteristic of an RTD has a maximum value and a minimum value located on the higher voltage side than the maximum value. Here, the voltage value at the maximum value is referred to as the voltage value V OL The voltage value at the minimum value is V OH Then, the voltage value V OL to voltage value V OH The current spectrum over this range is considered to be a negative differential resistance region that exhibits negative differential resistance characteristics. In this specification, this negative differential resistance region is defined as a first voltage region RA. That is, the RTD has a negative differential resistance region (first voltage region RA) that exhibits negative differential resistance characteristics in the voltage-current characteristics of its operating region. Also, in this specification, the voltage value V in the voltage regions on both sides of the first voltage region RA in the voltage-current characteristic graph is defined as OL The lower voltage region is called the second voltage region RB, and the voltage value V OH The region higher than the first voltage value V2, V3, V4 in the first voltage region RA, the second voltage value V1 in the second voltage region RB, and the third voltage value V5 in the third voltage region RB are defined as a third voltage region RC. The RTD functions as an element that oscillates electromagnetic waves W when at least one of the first voltage values ​​V2, V3, and V4 in the first voltage region RA, the second voltage value V1 in the second voltage region RB, and the third voltage value V5 in the third voltage region is applied.

[0018] When the transmitter 28 receives the synchronization signal data from the synchronization signal level converter 24B, it transmits a synchronization signal having a pattern corresponding to at least one of the three first voltage values ​​V2, V3, and V4 in the first voltage range RA, the second voltage value V1 in the second voltage range RB, and the third voltage value V5 in the third voltage range. The synchronization signal in this embodiment notifies the electromagnetic wave receiving device 30 of the detection timing of the transmission signal and also serves to identify some or all of the voltage levels used in the modulated signal. When the transmitter 28 receives the multilevel data from the multilevel converter 24A, it transmits a digital signal having a pattern corresponding to at least one of the three first voltage values ​​V2, V3, and V4 in the first voltage range RA, the second voltage value V1 in the second voltage range RB, and the third voltage value V5 in the third voltage range. In this embodiment, the first voltage values ​​V2, V3, and V4 in the first voltage region RA are set to three levels of voltage values ​​as an example, but the first voltage values ​​in the first voltage region RA may have two or more levels.

[0019] As described above, the multi-level setting and synchronization level setting in this embodiment are set to at least one of three first voltage values ​​V2, V3, and V4 in the first voltage region RA, the second voltage value V1 in the second voltage region RB, and the third voltage value V5 in the third voltage region. Furthermore, the electromagnetic wave transmitting device 20 of this embodiment is configured to multi-level-modulate the multi-level data and synchronization signal data, and transmit the multi-level-modulated data on an electromagnetic wave W to the electromagnetic wave receiving device 30.

[0020] [Electromagnetic wave receiving device] The electromagnetic wave receiving device 30 receives the electromagnetic waves W transmitted by the electromagnetic wave transmitting device 20 and demodulates the received electromagnetic waves W into a digital signal. For example, if the digital signal is a digitized sound signal, the electromagnetic wave receiving device 30 generates detection timing based on synchronization signal data in the electromagnetic waves W received by the electromagnetic wave receiving device 30 and demodulates the digital sound signal.

[0021] The above is a description of the configuration of this embodiment.

[0022] <Operation> Next, the operation of the electromagnetic wave communication system 10 of this embodiment will be described with reference to the drawings. First, the overall flow will be described, and then specific examples of multi-level modulation will be explained. Note that as an example, a case will be taken where a sound-related signal is communicated using the electromagnetic wave communication system 10. As mentioned above, the effects of this embodiment will also be described in conjunction with the following explanation.

[0023] [Overall flow] The overall flow of the operation of this embodiment will be described with reference to FIG. 1, FIG. 2A and FIG. 2B. First, the acquisition unit 22 acquires a digital signal relating to sound from an external device (not shown), and outputs the acquired digital signal to the conversion unit 24 (multi-level conversion unit 24A).

[0024] Next, the multi-level conversion section 24A receives the digital signal (communication data) from the acquisition section 22 as input, converts it into a multi-level signal according to the multi-level setting by the multi-level setting section 29A, and outputs it. As shown in FIG. 2B, the multi-level conversion section 24A has a multi-level conversion section 24B1, a multi-level extension section 24B2, and a voltage conversion section 24B3, and the flow of operations thereof is as follows. When a digital signal (communication data) is input, the multi-value conversion unit 24B1 converts the data into multi-values ​​and outputs n values ​​(n≧3, in this embodiment, n=4 as an example) to the multi-value expansion unit 24B2. Next, the multi-value extension unit 24B2 converts the n value to an n+1 value (for example, using a multi-value (n+1) level setting value). Then, the multi-value extension unit 24B2 determines that the voltage output during non-oscillation will be either the voltage level of the second voltage region RB (second voltage value V1) or the voltage value level of the third voltage region (third voltage value V5). In this case, the multi-value extension unit 24B2 selects the smaller of the total transition potential difference (described later) when passing through the voltage level of the second voltage region RB (second voltage value V1) and the total transition potential difference when passing through the voltage value level of the third voltage region (third voltage value V5). Next, the voltage conversion unit 24B3 converts the n+1 values ​​(for example, 5 values) into voltages of n+1 levels (5 levels) according to the multi-level setting value, and outputs the voltages to the selector 26B. Furthermore, the synchronization signal level conversion section 24B outputs a predetermined synchronization signal level in accordance with the synchronization level setting by the synchronization level setting section 29B. Here, the synchronization signal level conversion section 24B has the configuration shown in FIG. 2B, and operates in the same manner as the multi-value level conversion section 24A.

[0025] Next, the switching unit 26A generates switching timing between the multi-level data and the synchronization signal data, which are selected by the selector 26B and output to the transmission unit 28, and inputs the generated timing to the selector 26B. As a result, the selector 26B outputs the synchronization signal data and the multi-level data to the transmission unit 28 at different timings in accordance with the switching timing generated by the switching unit 26A.

[0026] Next, the transmitter 28 transmits the data selected and input by the selector 26B (the n+1 level (for example, 5-level) data transmitted by the voltage converter 24B3) on an electromagnetic wave W. That is, the transmitter 28 transmits the electromagnetic wave W indicating the modulated signal for the data.

[0027] Next, the electromagnetic wave receiving device 30 receives the electromagnetic wave W transmitted by the transmitting unit 28 (electromagnetic wave transmitting device 20), generates detection timing based on the synchronization signal data in the received electromagnetic wave W, and demodulates the multi-level data into a digital signal. As a result, the electromagnetic wave W received by the electromagnetic wave receiving device 30 is demodulated into a digital sound signal.

[0028] The above is a description of the overall flow of operations in this embodiment.

[0029] [Example of multi-level modulation] Next, a specific example of a modulated signal in multi-level modulation will be described with reference to the following example.

[0030] (Example 1 and Example 2) First, a first example and a second example will be described with reference to FIGS. 4 and 5 are examples of modulated signals transmitted by the electromagnetic wave transmission device 20 of this embodiment, with FIG. 4 being a first example and FIG. 5 being a second example. Here, in FIGS. 4 and 5, V represents voltage value and t represents time. On the axis of voltage value V, V1, V2, V3, V4, and V5 represent the second voltage value in the second voltage region RB, the three first voltage values ​​in the first voltage region RA, and the third voltage value in the third voltage region RC, respectively. The patterns of these modulated signals include multi-level data and synchronization signal data. In addition, V in Figure 4 sync1 , V sync2 and V sync3 and V in Figure 5 sync4 and V sync5 indicates a portion of the modulated signal that corresponds to the synchronization signal data. The overall pattern in Fig. 5 indicates a modulated signal that includes a portion that corresponds to the synchronization signal data and the other portion (the portion that corresponds to the modulated data). That is, in this embodiment, the transmitter 28 transmits the synchronization signal as at least a portion of the modulated signal.

[0031] As shown in FIGS. 4 and 5 , the signal generated by the converter 24 in this embodiment is a modulated signal using two or more voltage levels among the first voltage levels V2, V3, and V4 in the first voltage region RA and at least one of the second voltage level V1 in the second voltage region RB and the third voltage level V5 in the third voltage region. That is, the signal generated by the converter 24 in this embodiment is a modulated signal that has been multi-level modulated using three or more voltage levels. Specifically, the modulated signal is a signal that has been multi-level modulated by converting m-bit (m≧1, for example, m=2 in this embodiment) data into n-level (n≧3, for example, n=4 in this embodiment) voltage levels. Therefore, in this embodiment, a larger amount of data can be transmitted in the same time period than the techniques disclosed in the aforementioned Patent Documents 1 and 2 (hereinafter referred to as the comparative techniques). Therefore, the electromagnetic wave transmission device 20 of this embodiment can achieve a higher transmission speed than the comparative technology, and accordingly, the electromagnetic wave communication system 10 of this embodiment can achieve a higher communication speed than the comparative technology.

[0032] The second voltage region RB and the third voltage region RC are generally considered to be non-oscillation regions. The "non-oscillation region" refers to a region other than the voltage region for oscillating the electromagnetic wave W in the voltage-current characteristics of the RTD. However, as shown in FIG. 4, in this embodiment, the synchronization signal V sync1 , V sync2 , V sync3 is set to include at least one of the voltage values ​​in the second voltage region RB and the third voltage region RC (see FIG. 3). A voltage transition including the voltage values ​​in the second voltage region RB and the third voltage region RC (the second voltage value V1 and the third voltage value V5), which are normally considered to be non-oscillation regions, can increase the S / N ratio compared to, for example, a voltage transition at voltage values ​​only within the normal oscillation region (corresponding to the first voltage region RA). Therefore, the electromagnetic wave transmitting device 20 of this embodiment can transmit a signal that is less likely to be erroneously detected by the electromagnetic wave receiving device 30. Accordingly, the electromagnetic wave communication system 10 of this embodiment has high communication stability in terms of the recognizability of the synchronization signal. Furthermore, as described above, the electromagnetic wave transmitting device 20 of this embodiment can increase the transmission speed compared to the comparative technology, and therefore the electromagnetic wave transmitting device 20 of this embodiment can transmit a signal that is less likely to be erroneously detected by the electromagnetic wave receiving device 30 while increasing the transmission speed compared to the comparative technology.

[0033] Also, in FIG. 4 (first example), the synchronization signal V sync1 is set to a specific pattern in which the voltage value transitions from one of the minimum voltage value (second voltage value V1) and the maximum voltage value (first voltage value V4) to the other (a pattern in which the voltage value transitions in the order of V1, V2, V3, V4, or a pattern in which the voltage value transitions in the reverse order). That is, the synchronization signal V sync1is a pattern including the maximum voltage value (first voltage value V4) and the minimum voltage value (second voltage value V1) of the voltage setting levels within the first voltage range RA. Therefore, the electromagnetic wave receiving device 30 of this embodiment recognizes the maximum and minimum voltage values ​​of the modulated signal to be received. The digital signal is multi-level modulated using the voltage values ​​V1, V2, V3, and V4. In Figure 4 (first example), the synchronization signal V sync3 The synchronization signal V is set to a specific pattern in which the voltage value transitions from one of the minimum voltage value (first voltage value V2) to the other of the maximum voltage value (third voltage value V5) (a pattern in which the voltage value transitions in the order of V2, V3, V4, V5, or a pattern in which the voltage value transitions in the reverse order). sync2 are set to a specific pattern in which the voltage value transitions from one of the minimum voltage value (first voltage value V2) and the maximum voltage value (second voltage value V1) to the other (a pattern in which the voltage value transitions in the order of V2 and V1, or a pattern in which the voltage value transitions in the reverse order).The digital signal is multi-level modulated using the voltage values ​​V2, V3, V4, and V5. Therefore, the electromagnetic wave transmitting device 20 of this embodiment can transmit a synchronization signal that is easily recognized by the electromagnetic wave receiving device 30. Accordingly, the electromagnetic wave communication system 10 of this embodiment has high communication stability in terms of the recognizability of the synchronization signal.

[0034] Also, the synchronization signal V in Figure 5 (second example) sync4 , V sync5 is set to use four levels, which include any voltage value (second voltage value V1 and third voltage value V5) in the second voltage region RB and the third voltage region RC (see FIG. 3), which are considered to be normal non-oscillation regions, and which represent all levels that a digital signal can take as multi-value levels. Therefore, in this embodiment, by using such a synchronization signal, it becomes possible to transmit the level voltage of the synchronization signal as teacher data to the electromagnetic wave transmitting device 20. Furthermore, in the electromagnetic wave receiving device 30, it becomes possible to extract each level voltage from the synchronization signal and set the level of the multi-value data of the received signal. Therefore, the electromagnetic wave transmitting device 20 of this embodiment can cause the electromagnetic wave receiving device 30 to recognize the level voltage of the modulated signal.

[0035] In addition, in this embodiment, it is possible to generate a modulation signal using two or more voltage values ​​among the first voltage values ​​V2, V3, and V4 in the first voltage region RA, as well as both the second voltage value V1 in the second voltage region RB and the third voltage value V5 in the third voltage region. However, in this embodiment, for example, which voltage value among the second voltage value V1 in the second voltage region RB and the third voltage value V5 in the third voltage region is used to generate a modulation signal is determined as follows. Here, a signal (an example of a first signal) that transitions from one of the first voltage values ​​V2, V3, and V4 to the second voltage value V1 and a signal (an example of a second signal) that transitions from the same one of the first voltage values ​​V2, V3, and V4 as the first signal to the third voltage value V5 are the same signal. When the multi-level conversion section 24A (conversion section 24) of this embodiment transitions a signal from one of the first voltage values ​​V2, V3, and V4 to one of the second voltage value V1 and the third voltage value V5, it transitions the signal in the direction that reduces the total transition potential difference. Here, the "total transition potential difference" refers to the sum of the potential differences that vary from the potential before (at the start) a transition in a certain modulated signal to the potential after (at the end) the transition. Specifically, when the voltage value before a transition in a certain modulated signal is V1, and then the voltage value after the transition via voltage value V4 is V3, the total transition potential difference is the sum of the potential difference between V1 and V4 and the potential difference between V4 and V3. From the above, for example, when the voltage value of one of the first voltage values ​​V2, V3, and V4 is the first voltage value V2, and the potential difference ΔV between the voltage value V2 and the second voltage value V1 is 12 is the potential difference ΔV between the voltage value V2 and the third voltage value V5 25 , the multi-level conversion unit 24A transitions the signal to the second voltage value V1, which is the voltage value that results in a smaller total transition potential difference. 24 is the potential difference ΔV between the voltage value V4 and the third voltage value V5 45 If the voltage difference is greater than V1, the multi-level conversion section 24A transitions the signal to the third voltage value V5, which is the voltage difference that reduces the total transition potential difference. Therefore, in this embodiment, when a modulation signal is generated using the voltage value in the first voltage region RA and the voltage values ​​in both the second voltage region RB and the third voltage region, the total transition potential difference is reduced as described above, thereby making it possible to further increase the transmission speed (communication speed).

[0036] The above is the explanation of the first and second examples. Note that the above point, i.e., specific examples of which voltage value, the second voltage value V1 in the second voltage region RB or the third voltage value V5 in the third voltage region, is used to generate the modulation signal will be explained using the third and subsequent examples described later.

[0037] (Example 3) Next, a third example will be described with reference to Fig. 6A and Fig. 6B. Fig. 6A shows another example (third example) of a modulated signal transmitted by the electromagnetic wave transmission device 20 of this embodiment. In contrast, Fig. 6B shows an example (first comparative example) of a modulated signal transmitted by an electromagnetic wave transmission device of a comparative embodiment. As shown in FIGS. 6A and 6B, the potential difference between V1 and V2 is ΔV, where V2, V3, and V4 are three levels in the first voltage region RA, V1 is a second voltage in the second voltage region RB, and V5 is a third voltage in the third voltage region. 12 , the potential difference between V2 and V3 is Δ 23 , the potential difference between V3 and V4 is Δ 34 , the potential difference between V4 and V5 is Δ 45 Specifically, the potential difference Δ 12 , potential difference Δ 23 , potential difference Δ 34 , potential difference Δ 45 are set to 15 mV, 10 mV, 20 mV, and 25 mV, respectively. In other words, in this embodiment, when the voltage values ​​V2, V3, and V4 of the first voltage value, the second voltage value V1, and the third voltage value V5 are arranged in order from the smallest to the largest, the potential difference (potential difference Δ 12 , potential difference Δ 23 , potential difference Δ 34 , potential difference Δ 45) have different potential differences. In addition, the potential differences Δ 12 , Δ 13 , Δ 14 are the potential differences Δ between the voltages V2, V3, and V4, which are two or more levels of the first voltage, and the third voltage V5. 25 , Δ 35 , Δ 45 The potential difference is different.

[0038] The modulated signal V in Figure 6A sync6 (an example of the first signal) and the modulated signal V sync7 (an example of the second signal) has a voltage value V3 before the transition and a voltage value V3 after the transition. sync6 , V sync7 The difference is that the modulation signal V sync6 passes through the second voltage value V1 in the second voltage region RB and the total transition potential difference is 50 mV, while the modulation signal V sync7 is the point at which the third voltage value V5 in the third voltage region is passed and the total transition potential difference is 90 mV. sync6 and the modulated signal V in Figure 6B sync7 means the same signal (meaning a signal with the same technical meaning).

[0039] In this embodiment, the modulated signal V sync6 and the modulated signal V in Figure 6B sync7 Although the modulation signal V in Fig. 6A is the same as the modulation signal V in Fig. 6B, the total transition potential difference is smaller. sync6 Select . As described above, in this embodiment, when a modulated signal is generated using voltage values ​​in the first voltage region RA and voltage values ​​in both the second voltage region RB and the third voltage region, the transmission speed (communication speed) can be increased by selecting the third example (see Figure 6A) rather than the first comparative example (see Figure 6B) of the comparative form.

[0040] This concludes the explanation of the third example.

[0041] (Example 4) Next, a fourth example will be described with reference to Fig. 7A and Fig. 7B. Fig. 7A shows another example (fourth example) of a modulated signal transmitted by the electromagnetic wave transmission device 20 of this embodiment. In contrast, Fig. 7B shows an example (second comparative example) of a modulated signal transmitted by an electromagnetic wave transmission device of a comparative embodiment. Here, as shown in FIGS. 7A and 7B, the potential difference Δ 12 , potential difference Δ 23 , potential difference Δ 34 , potential difference Δ 45 are 15 mV, 10 mV, 20 mV, and 5 mV, respectively. In other words, in this embodiment, when the voltage values ​​V2, V3, and V4 of the two or more levels of the first voltage value, the second voltage value V1, and the third voltage value V5 are arranged in order from the smallest to the largest, the potential difference (potential difference Δ 12 , potential difference Δ 23 , potential difference Δ 34 , potential difference Δ 45 ) have different potential differences. The modulated signal V in Figure 7A sync8 (an example of the first signal) and the modulated signal V sync9 (an example of the second signal) has a voltage value V3 before the transition and a voltage value V3 after the transition. sync8 , V sync9 The difference is that the modulation signal V sync8 passes through the second voltage value V1 in the second voltage region RB, whereas the modulated signal V sync9 is a point passing through the third voltage value V5 in the third voltage region. sync8 , V sync9 The total transition potential difference is 50 mV.

[0042] In this embodiment, the modulated signal V sync8 and the modulated signal V in Figure 7B sync9 7A, which is the smaller voltage value of the second voltage value V1 and the third voltage value V5, even though they are the same signal. sync8 Select . As described above, in this embodiment, the modulation signal V in FIG. 7B, which is the larger voltage value of the second voltage value V1 and the third voltage value V5, is used. sync9 This can suppress heat generation from the RTD compared to when

[0043] This concludes the explanation of the fourth example.

[0044] (Example 5) Next, a fifth example will be described with reference to Fig. 8A and Fig. 8B. Fig. 8A shows another example (fifth example) of a modulated signal transmitted by the electromagnetic wave transmission device 20 of this embodiment. In contrast, Fig. 8B shows an example (third comparative example) of a modulated signal transmitted by an electromagnetic wave transmission device of a comparative embodiment. As shown in FIGS. 8A and 8B, the potential differences Δ between the first voltage V1 and each of the voltages V2, V3, and V4, which are at least two levels, are 12 , Δ 13 , Δ 14 are the potential differences Δ between the voltages V2, V3, and V4, which are two or more levels of the first voltage, and the third voltage V5. 25 , Δ 35 , Δ 45 The potential difference is different.

[0045] The modulated signal V in Figure 8A sync10 (an example of the first signal) and the modulated signal V sync11 (an example of the second signal) has a voltage value of V4 before the transition and a voltage value of V2 after the transition. sync10 , V sync11 The difference is that the modulation signal V sync10 passes through the second voltage value V1 in the second voltage region RB and the total transition potential difference is 60 mV, while the modulation signal V sync11 is the point at which the third voltage value V5 in the third voltage region is passed and the total transition potential difference is 70 mV. sync10 and the modulated signal V in Figure 8B sync11 is the same signal.

[0046] In this embodiment, the modulated signal Vsync10 and the modulated signal V in Figure 8B sync11 Although the modulation signal V in Fig. 8A is the same as the modulation signal V in Fig. 8B, the total transition potential difference is smaller. sync10 Select . As described above, in this embodiment, when generating a modulated signal using the voltage values ​​in the first voltage region RA and the voltage values ​​in both the second voltage region RB and the third voltage region, by selecting the fifth example (see FIG. 8A) instead of the third comparative example (see FIG. 8B) of the comparative embodiment, the transmission speed (communication speed) can be increased. Furthermore, this embodiment can suppress heat generation from the RTD compared to when the third comparative example (see FIG. 8B) of the comparative embodiment is selected.

[0047] This concludes the explanation of the fifth example.

[0048] [Additional information on the relationship between voltage and output carrier level] Next, the relationship between each voltage value in the voltage-current characteristics of the RTD and the voltage-output carrier level in this embodiment will be further described with reference to FIGS. 9A and 9B.

[0049] (Example 1) FIG. 9A is a diagram showing a first example of the relationship between a graph showing the voltage-current characteristics of an RTD and a graph showing the voltage (bias voltage)-output level characteristics in this embodiment. The graph showing the voltage-current characteristics of the RTD is as explained above in FIG. In contrast, as shown in FIG. 9A, the graph showing the voltage-output level characteristics shows that the output level is not proportional to the voltage, but rather increases from a minimum value to a maximum value as the voltage value increases, before returning to a minimum value. Here, the conversion unit 24 converts the first voltage value (three voltage values ​​in this case) of two or more levels, the second voltage value, and the third voltage value into corresponding output carrier levels O1, O2, O3, and O4, respectively, in accordance with the voltage-output level characteristic shown by the curve, so that the relationship between the first voltage value and the third voltage value in the first voltage range RA is determined. In the first example of this embodiment, the relationship between the determined output carrier levels is a relationship in which the corresponding output carrier levels O1, O2, O3, and O4 are arranged at equal intervals in the output level (the difference ΔO 12 , the difference between O2 and O3 ΔO 23 and the difference between O3 and O4, ΔO 34 are equal to each other) (therefore, the first voltage values ​​at two or more levels in the first voltage region RA are not arranged at equal intervals). As described above, in the first example of this embodiment, it is possible to shorten the data transition time for generating modulation data that includes at least one of the second voltage region RB and the third voltage region RC, which are normally used as non-oscillation regions, and thus to save power.

[0050] (Example 2) Next, the second example will be described with reference to FIG. 9B, focusing on differences from the first example. In the second example, the relationship between the predetermined output carrier levels is such that the maximum value O4 of the corresponding output carrier levels O1, O2, O3, and O4 is set to a value smaller than the maximum value of the voltage-output level characteristics. Therefore, in the second example, the output carrier level O4 is more likely to be accurately output than in the first example. This is because the curve of the voltage-output level characteristics of the RTD fluctuates when the RTD heats up due to the application of voltage. Other effects of the second example are similar to those of the first example.

[0051] (Example 3) Next, the third example will be described with reference to FIG. 9C, focusing on differences from the first example. In the third example, the relationship between the determined output carrier levels is such that the minimum value O1 of the corresponding output carrier levels O1, O2, O3, and O4 is set to a value greater than the minimum value of the voltage-output level characteristics. Therefore, in the third example, the output carrier level O1 is more likely to be accurately output than in the first and second examples. This is because the curve of the RTD's voltage-output level characteristics is more likely to fluctuate due to noise as it approaches the minimum value (closer to 0). Other effects of the third example are similar to those of the first example.

[0052] (Example 4) Next, the fourth example will be described with reference to FIG. 9D, focusing on differences from the first, second and third examples. In the fourth example, the relationship between the determined output carrier levels is such that the maximum value O4 of the corresponding output carrier levels O1, O2, O3, and O4 is set to a value smaller than the maximum value of the voltage-output level characteristics, and the minimum value O1 is set to a value larger than the minimum value of the voltage-output level characteristics. In other words, the fourth example is a combination of the second and third examples. As described above, the effect of the fourth example is the same as that of the first, second and third examples.

[0053] As described above, the present invention has been described using a specific embodiment as an example, but the present invention is not limited to this embodiment. The technical scope of the present invention also includes, for example, the following forms (modifications).

[0054] For example, in the present embodiment, three voltage levels are set within the first voltage region RA, but the number of set voltage levels within the first voltage region RA may be two or more.

[0055] In this embodiment, the pattern of the synchronization signal is V in FIG. sync1 , V sync2 , V sync3 and V in Fig. 5 sync4 , V sync5However, the pattern of the synchronization signal may be different from these. In the description of this embodiment, the pattern of the synchronization signal is V in FIG. sync1 , V sync2 , V sync3 and V in Fig. 5 sync4 , V sync5 was described as an example. However, the technical scope of the present invention may include any one of these synchronization signal patterns or variations thereof. That is, the synchronization signal may be any one of (1) a signal that includes the second voltage value V1 in the second voltage region RB and does not include the third voltage value V5 in the third voltage region RC, (2) a signal that does not include the second voltage value V1 in the second voltage region RB and includes the third voltage value V5 in the third voltage region RC, and (3) a signal that includes the second voltage value V1 in the second voltage region RB and the third voltage value V5 in the third voltage region RC.

[0056] In the present embodiment, the synchronization signal level conversion unit 24B, which may be provided in a subsequent stage due to the same configuration, has been described as having a multi-value extension unit 24B2 and a voltage conversion unit 24B3 (see FIG. 2B). However, for example, the multi-value extension unit 24B2 and the voltage conversion unit 24B3 may be extracted from the synchronization signal level conversion unit 24B, and the multi-value extension unit 24B2 and the voltage conversion unit 24B3 may be provided between the selector 26B and the transmission unit 28.

[0057] This application claims priority based on Japanese Patent Application No. 2019-080688, filed April 22, 2019, the disclosure of which is incorporated herein by reference in its entirety. [Explanation of symbols]

[0058] 10 Electromagnetic communication systems 20 Electromagnetic wave transmitting device 22 Acquisition Department 24 Conversion section (an example of a modulation section) 24A Multi-value level conversion section 24B Sync signal level conversion section 24B1 Multi-level conversion section 24B2 Multi-value extension 24B3 Voltage conversion unit 26A Switching Unit 26B Selector 28 Transmitter 30 Electromagnetic wave receiving device RA First voltage area RB Second voltage region RC 3rd voltage area V1 second voltage value V2, V3, V4 first voltage value V5 3rd voltage value W Electromagnetic waves (an example of terahertz waves)

Claims

[Claim 1] a transmitter that transmits an electromagnetic wave representing a modulated signal, the voltage-current characteristic of which has a maximum value and a minimum value located on a higher voltage side than the maximum value; an acquisition unit that acquires a digital signal; a modulation unit that modulates the digital signal into the modulated signal using a first voltage value of two or more levels in a first voltage range that is a voltage range equal to or higher than the maximum voltage and equal to or lower than the minimum voltage, a second voltage value in a second voltage range that is a voltage range lower than the maximum voltage, and a third voltage value in a third voltage range that is a voltage range higher than the minimum voltage; Equipped with a first signal that transitions from an arbitrary voltage value among two or more first voltage values ​​in the first voltage region to one of the two or more voltage values ​​of the first voltage value via the second voltage value, and a second signal that transitions from the arbitrary voltage value to the one of the voltage values ​​via the third voltage value are the same signal; the modulation unit selects the modulation signal having a smaller total transition potential difference between the first signal and the second signal when the total transition potential difference between the first signal and the second signal is different. Electromagnetic wave transmitting device.

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