Amplitude Modulation Circuit

Abstract

To generate desired amplitude modulation data even if the amplitude of input data is not constant.SOLUTION: An amplitude modulation circuit 1 which generates modulation data obtained by modulating input data input from the outside includes: a detection unit 12 which detects a maximum value and a minimum value of the input data; a data conversion unit 14 which generates conversion data by converting the input data on the basis of the maximum value and the minimum value; and an amplitude modulation signal generation unit 15 which generates an amplitude modulation signal on the basis of the amplitude of the conversion data. The data conversion unit 14 converts the input data to normalized data so that the maximum value corresponds to the maximum voltage in a voltage range which is allowed to be input to the amplitude modulation signal generation unit 15 and that the maximum value corresponds to the minimum voltage in the voltage range, and generates the conversion data by converting the normalized data on the basis of a modulation degree in the amplitude modulation signal generation unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an amplitude modulation circuit. [Background technology]

[0002] There is known an amplitude modulation circuit that generates modulated data by modulating the amplitude of input data. Patent Document 1 discloses a technique for amplifying or attenuating input data with a preset amplification factor or attenuation factor so that the modulation factor of output data becomes a desired maximum modulation factor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-359656 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology of Patent Document 1, the amplification factor or attenuation factor is set on the premise that the amplitude of the input data is constant. Therefore, when input data with an indefinite amplitude is input, it is not possible to obtain output data with the desired maximum modulation degree.

[0005] Therefore, the present invention has been made in consideration of these points, and an object of the present invention is to generate desired amplitude modulated data even if the amplitude of the input data is indefinite. [Means for solving the problem]

[0006] In a first aspect of the present invention, there is provided an amplitude modulation circuit that generates modulated data by modulating input data input from an outside, the amplitude modulation circuit having: a detection unit that detects a maximum value and a minimum value of the input data; a data conversion unit that generates converted data by converting the input data based on the maximum value and the minimum value; and an amplitude modulation signal generation unit that generates an amplitude modulated signal based on the amplitude of the converted data, wherein the data conversion unit converts the input data into normalized data so that the maximum value corresponds to a maximum voltage in a voltage range that can be input to the amplitude modulation signal generation unit, and the minimum value corresponds to a minimum voltage in the voltage range, and the amplitude modulation circuit generates the converted data by converting the normalized data based on a modulation degree in the amplitude modulation signal generation unit.

[0007] The data conversion unit may convert the input data into the normalized data by offsetting the input data so that the maximum value corresponds to the maximum voltage, and converting the offset input data so that the minimum value of the offset input data corresponds to the minimum voltage.

[0008] The data conversion unit may generate the converted data by multiplying the normalized data by a first coefficient and then offsetting it so that a ratio of a difference between a maximum value and a minimum value of the converted data to a sum of the maximum value and the minimum value of the converted data becomes the modulation depth.

[0009] The data conversion unit may generate the converted data by multiplying the normalized data by the first coefficient and then offsetting the multiplied data by a second coefficient so that a maximum value of the converted data becomes a predetermined value. Effect of the Invention

[0010] According to the present invention, it is possible to generate desired amplitude modulated data even if the amplitude of the input data is indefinite. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic diagram of an amplitude modulation circuit according to the present embodiment. [Diagram 2] FIG. 4 is a schematic diagram of input data. [Diagram 3] FIG. 1 is a schematic diagram of normalized data. [Figure 4] 11 is a schematic diagram of post-multiplication data obtained by multiplying normalized data by a first coefficient. FIG. [Diagram 5] FIG. 4 is a schematic diagram of offset data. [Figure 6] 13 is a schematic diagram of conversion data generated by multiplying offset data by a second coefficient. FIG. [Figure 7] FIG. 13 is a schematic diagram of multiplied data in a comparative example in which non-normalized input data is multiplied by a first coefficient. [Figure 8] FIG. 13 is a schematic diagram of offset data of a comparative example. [Figure 9] 13 is a schematic diagram of conversion data generated by multiplying offset data of the comparative example by a second coefficient. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 1 is a schematic diagram of an amplitude modulation circuit 1 according to this embodiment. The amplitude modulation circuit 1 is, for example, an integrated circuit (programmable logic device) whose internal logic circuit can be defined and changed. The amplitude modulation circuit 1 according to this embodiment is, but is not limited to, an FPGA (field-programmable gate array).

[0013] The amplitude modulation circuit 1 generates conversion data based on normalized data obtained by normalizing input data input from an external device. The amplitude modulation circuit 1 then generates an amplitude modulation signal based on the amplitude of the generated conversion data. The amplitude modulation circuit 1 includes a memory 11, a detection unit 12, a coefficient calculation unit 13, a data conversion unit 14, and an amplitude modulation signal generation unit 15.

[0014] The memory 11 is, for example, a static random access memory (SRAM) and stores various information, for example, the memory 11 stores the modulation degree, the maximum signal level, and the input data input from the outside.

[0015] The detection unit 12 detects the maximum and minimum values ​​of the input data. FIG. 2 is a schematic diagram of the input data. The vertical axis indicates the magnitude of the input data value. The range of the vertical axis is the voltage range that can be input to the amplitude modulation signal generation unit 15. Note that the maximum voltage VMAX in FIG. 2 is the maximum voltage in the inputtable voltage range, and the minimum voltage VMIN is the minimum voltage in the inputtable voltage range. The detection unit 12 detects the maximum value 51 and minimum value 61 of the input data shown in FIG. 2.

[0016] The coefficient calculation unit 13 calculates various coefficients used by the data conversion unit 14. For example, the coefficient calculation unit 13 acquires a modulation degree from the memory 11, and calculates a first coefficient based on the acquired modulation degree. The first coefficient is a coefficient that is multiplied by predetermined data to set the ratio of the difference between the maximum value and the minimum value of the predetermined data to the sum of the maximum value and the minimum value of the predetermined data to the acquired modulation degree. The modulation degree can be appropriately set, for example, by a designer who designs the amplitude modulation circuit 1 or a user of a device having the amplitude modulation circuit 1, and a value input from an external device, for example, is stored in the memory 11.

[0017] The coefficient calculation unit 13 acquires the maximum signal level from the memory 11, and calculates a second coefficient based on the acquired maximum signal level. The second coefficient is a coefficient that is multiplied by predetermined data to make the maximum value of the predetermined data the maximum signal level. The maximum signal level can be appropriately set by, for example, a designer who designs the amplitude modulation circuit 1, and a value input from, for example, an external device is stored in the memory 11.

[0018] The data conversion unit 14 generates converted data by converting the input data based on the maximum and minimum values ​​detected by the detection unit 12. Specifically, the data conversion unit 14 has a normalization unit 141, a modulation adjustment unit 142, and a maximum signal level adjustment unit 143.

[0019] Normalization unit 141 converts input data into normalized data so that the input data corresponds to a voltage range that can be input to amplitude modulation signal generation unit 15. The input voltage range is determined according to the specifications of amplitude modulation signal generation unit 15. Values ​​that can be input as the voltage range are represented by, for example, 16-bit digital data. In this case, the value represented as the maximum voltage is FFFF, and the value represented as the minimum voltage is 0000.

[0020] The normalization unit 141 offsets the input data so that the maximum value of the input data corresponds to the maximum voltage VMAX of the voltage range. Next, the normalization unit 141 converts the offset input data into normalized data by converting the offset input data so that the minimum value of the offset input data corresponds to the minimum voltage VMIN in the voltage range. Specifically, the normalization unit 141 converts the offset input data into normalized data by expanding the offset input data so that the minimum value of the offset input data corresponds to the minimum voltage VMIN.

[0021] 3 is a schematic diagram of the normalized data. As shown in FIG 3, the maximum value 52 of the normalized data corresponds to the maximum voltage VMAX of the voltage range, and the minimum value 62 corresponds to the minimum voltage VMIN of the voltage range.

[0022] The modulation degree adjustment unit 142 converts the normalized data so that it has a desired modulation degree. Specifically, first, the modulation degree adjustment unit 142 multiplies the normalized data by a first coefficient. The first coefficient is set so that the ratio of the difference between the maximum value and the minimum value of the offset data, which is offset so that the maximum value of the predetermined data becomes the maximum voltage, to the sum of the maximum value and the minimum value of the offset data, becomes the desired modulation degree. In other words, the first coefficient is set so that the modulation degree of the offset data, which is obtained by multiplying the normalized data by the first coefficient and offsetting the multiplied data so that the maximum value of the multiplied data corresponds to the maximum voltage, becomes the desired modulation degree.

[0023] Fig. 4 is a schematic diagram of data after multiplication in which normalized data is multiplied by a first coefficient. A maximum value 53 shown in Fig. 4 is the maximum value 52 in Fig. 3 multiplied by a first coefficient. Also, a minimum value 63 shown in Fig. 4 is the minimum value 62 in Fig. 3 multiplied by a first coefficient.

[0024] The modulation adjustment unit 142 generates offset data by offsetting multiplied data obtained by multiplying the normalized data by a first coefficient. The modulation adjustment unit 142 generates offset data by offsetting the multiplied data such that the maximum value of the multiplied data corresponds to the maximum voltage VMAX.

[0025] Fig. 5 is a schematic diagram of offset data. As shown in Fig. 5, the maximum value 54 of the offset data corresponds to the maximum voltage VMAX. The value of the maximum value 54 is α, and the value of the minimum value 64 is β. The ratio of the difference between α and β to the sum of α and β is the modulation index acquired by the coefficient calculation unit 13. If the acquired modulation index is mp, mp is expressed by the following formula (1). mp = (α-β) / (α+β)…(1)

[0026] The maximum signal level adjustment unit 143 adjusts the amplitude of the offset data to generate the converted data. Specifically, the maximum signal level adjustment unit 143 generates the converted data by multiplying the offset data by a second coefficient. The second coefficient is set so that the maximum value of the converted data generated by multiplying the offset data by the second coefficient becomes the maximum signal level.

[0027] Fig. 6 is a schematic diagram of the converted data generated by multiplying the offset data by the second coefficient. As shown in Fig. 6, the maximum value 55 of the converted data corresponds to the maximum signal level SMAX. If the second coefficient is N, the maximum value of the converted data is αN and the minimum value of the converted data is βN. The modulation depth of the converted data is expressed by the following formula (2). mp=(αN-βN) / (αN+βN)=(α-β) / (α+β)…(2) As shown in equation (2), multiplying the offset data by the second coefficient does not change the modulation depth.

[0028] [Example of a comparison where input data is not normalized] Unlike this embodiment, the converted data generated by an amplitude modulation circuit of a comparative example that does not normalize input data will be described. Fig. 7 is a schematic diagram of multiplied data of a comparative example in which non-normalized input data is multiplied by a first coefficient. The maximum value 72 of the multiplied data of the comparative example shown in Fig. 7 is smaller than the maximum value 53 of the multiplied data of this embodiment shown in Fig. 4. In addition, the absolute value of the minimum value 82 of the multiplied data of the comparative example shown in Fig. 7 is smaller than the absolute value of the minimum value 63 of the multiplied data of this embodiment shown in Fig. 4.

[0029] Fig. 8 is a schematic diagram of offset data of a comparative example. The value of maximum value 73 of the offset data of the comparative example shown in Fig. 8 is α, similar to the value of maximum value 54 of the offset data of this embodiment shown in Fig. 5. On the other hand, the value of minimum value 83 of the offset data of the comparative example shown in Fig. 8 is B, different from the value of minimum value 64 of the offset data of this embodiment shown in Fig. 5.

[0030] Fig. 9 is a schematic diagram of conversion data generated by multiplying the offset data of the comparative example by the second coefficient. The maximum value 74 of the conversion data of the comparative example shown in Fig. 9 is αN, similar to the maximum value 55 of the conversion data of the present embodiment shown in Fig. 6. On the other hand, the minimum value 84 of the conversion data of the comparative example shown in Fig. 9 is BN, unlike the minimum value 65 of the conversion data of the present embodiment shown in Fig. 6.

[0031] The modulation degree of the converted data in the comparative example is (αN-BN) / (αN+BN), and since β≠B, it does not become the acquired modulation degree mp. If input data with an indefinite amplitude is amplitude modulated without normalization as in the comparative example, it is not possible to obtain the desired modulation degree. On the other hand, the amplitude modulation circuit 1 of this embodiment can normalize the input data, thereby amplitude modulating normalized data with a constant amplitude, and therefore can generate converted data with the desired modulation degree.

[0032] The amplitude modulation signal generating unit 15 generates an amplitude modulation signal based on the amplitude of the converted data. Specifically, the amplitude modulation signal generating unit 15 has a D / A 151 and a mixer 152. The D / A 151 is a digital-to-analog converter, and converts the converted data generated by the data converting unit 14 into an analog signal. The mixer 152 superimposes a carrier wave on the converted analog signal to generate an amplitude modulation signal.

[0033] [Effect of Amplitude Modulation Circuit 1] As described above, the amplitude modulation circuit 1 converts the input data into normalized data so that the maximum value 51 of the input data corresponds to the maximum voltage VMAX in a predetermined voltage range, and the minimum value 61 corresponds to the minimum voltage VMIN in the voltage range. Next, the amplitude modulation circuit 1 generates an amplitude modulated signal based on the amplitude of the converted data obtained by converting the normalized data and a predetermined modulation degree. In this way, the amplitude modulation circuit 1 normalizes the input data to make the amplitude constant, and therefore can generate an amplitude modulated signal with a desired modulation degree even if the amplitude of the input data is not constant.

[0034] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by distributing or integrating functionally or physically in any unit. In addition, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment resulting from the combination combines the effect of the original embodiment. [Explanation of symbols]

[0035] 1 Amplitude Modulation Circuit 11. Memory 12 Detection section 13 Coefficient calculation section 14 Data conversion section 141 Normalization section 142 Modulation Adjustment Section 143 Maximum signal level adjustment section 15 Amplitude modulation signal generator 151 D / A 152 Mixer

Claims

1. An amplitude modulation circuit that generates modulated data by modulating input data input from an external device, A detection unit for detecting maximum and minimum values ​​of the input data; a data conversion unit that generates converted data by converting the input data based on the maximum value and the minimum value; an amplitude modulation signal generating unit that generates an amplitude modulation signal based on the amplitude of the converted data; having the data conversion unit converts the input data into normalized data so that the maximum value corresponds to a maximum voltage in a voltage range that can be input to the amplitude modulation signal generation unit, and the minimum value corresponds to a minimum voltage in the voltage range, and generates the converted data by converting the normalized data based on a modulation degree in the amplitude modulation signal generation unit.

2. The data conversion unit is offsetting the input data so that the maximum value corresponds to the maximum voltage; converting the input data to the normalized data by converting the offset input data such that a minimum value of the offset input data corresponds to the minimum voltage; 2. The amplitude modulation circuit according to claim 1.

3. the data conversion unit generates the converted data by multiplying the normalized data by a first coefficient and then offsetting the normalized data so that a ratio of a difference between a maximum value and a minimum value of the converted data to a sum of the maximum value and the minimum value of the converted data becomes the modulation index.

3. The amplitude modulation circuit according to claim 1 or 2.

4. the data conversion unit generates the converted data by multiplying the normalized data by the first coefficient and then offsetting the multiplied data by a second coefficient so that a maximum value of the converted data becomes a predetermined value.

4. The amplitude modulation circuit according to claim 3.

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