Digital modulator, communication device, and control method and program for digital modulator

Abstract

To provide a digital modulator, a communication device, a control method of the digital modulator, and a program that can widen a signal bandwidth while simplifying components.SOLUTION: A digital modulator 2 in the present disclosure includes a polar converter 3 that generates a phase signal and an amplitude signal from a baseband signal. The digital modulator includes: an RF phase signal generator 4 that generates an RF phase signal on the basis of the phase signal; and a rectangularizer 5 that rectangularizes the RF phase signal to generate a rectangular RF phase signal. The digital modulator includes a time interleaver 6 that time-interleaves the amplitude signal and outputs first and second time-interleaved signals. The digital modulator also includes a ΔΣ modulator 7 that outputs first and second ΔΣ modulated signals by ΔΣ modulating the first and second time-interleaved signals on the basis of, the rectangular RF phase signal. The digital modulator further includes a selector 8 that selects and outputs either the first or second ΔΣ modulated signal on the basis of the rectangular RF phase signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a digital modulator, a communication device, a method for controlling a digital modulator, and a program. [Background technology]

[0002] A wireless access system using optical fiber will be explained using Figure 10. In mobile network access networks, in places where radio waves from outdoor base stations have difficulty reaching, such as underground shopping malls or inside buildings, a wireless access system using optical fiber as shown in Figure 10 is deployed as a system to separately supply radio waves at low cost. In this system, a digital wireless signal generated by a center unit is converted from parallel to serial and then transmitted via optical fiber to a remote unit installed in a low-power area. The remote unit then converts the signal from serial to parallel and converts it to an analog signal using a digital-to-analog converter (DAC), which then converts it to a high-frequency signal and radiates it from an antenna.

[0003] On the other hand, a system shown in Figure 11 that converts a high-frequency radio signal into a rectangular 1-bit signal and transmits it directly to a slave unit using optical fiber does not require a DAC in the slave unit. This is expected to reduce the cost and increase the efficiency of the slave unit, as well as improve ease of installation. As a low-cost 1-bit transmission method, phase-locked EDSM (Envelope Delta-Sigma Modulation), a phase-locked digital modulation method that can generate rectangular waveforms at a low rate, is used. i on) is valid.

[0004] On the other hand, in order to support 5G wideband signals, the communication method needs to be made wider bandwidth. The bandwidth when using phase-locked digital modulation is proportional to the clock frequency of the delta-sigma modulator installed inside the transmitter. When using phase-locked digital modulation, a method is adopted in which a clock signal is oscillated using an RF phase signal, so the clock frequency is fixed to the carrier frequency. Therefore, if the carrier frequency is not sufficiently high, there is a problem that a sufficient bandwidth cannot be achieved. Patent Document 1 discloses technology related to a digital modulator that quadrature-modulates an N-level digital signal using a mixer and an adder. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-167465 Summary of the Invention [Problem to be solved by the invention]

[0006] In the digital modulator disclosed in Patent Document 1, the digital signal after quadrature modulation remains N-valued. Furthermore, after quadrature modulation, an N-valued signal divider generates N-1 binary signals, i.e., parallel 1-bit signals. This can complicate the design of the mixers and other components included in the digital modulator. [Means for solving the problem]

[0007] The digital modulator of the present disclosure includes a polar converter that generates a phase signal and an amplitude signal from a baseband signal, an RF phase signal generator that generates an RF phase signal based on the phase signal, a rectangularizer that rectangularizes the RF phase signal and generates a rectangular RF phase signal, a time interleaver that time interleaves the amplitude signal and outputs a first interleaved signal and a second time interleaved signal, a delta-sigma modulator that delta-sigma modulates the first interleaved signal and the second time interleaved signal based on the rectangular RF phase signal to output a first delta-sigma modulated signal and a second delta-sigma modulated signal, and a selector that inputs the first delta-sigma modulated signal and the second delta-sigma modulated signal and selects and outputs either the first delta-sigma modulated signal or the second delta-sigma modulated signal based on the rectangular RF phase signal.

[0008] A communication device according to the present disclosure includes a digital modulator and an optical module that performs signal processing based on an output signal of the digital modulator. The digital modulator includes a polar converter that generates a phase signal and an amplitude signal from a baseband signal, an RF phase signal generator that generates an RF phase signal based on the phase signal, a rectangularizer that rectangularizes the RF phase signal to generate a rectangular RF phase signal, a time interleaver that time-interleaves the amplitude signal and outputs a first interleaved signal and a second time-interleaved signal, a delta-sigma modulator that delta-sigma-modulates the first interleaved signal and the second time-interleaved signal based on the rectangular RF phase signal to output a first delta-sigma-modulated signal and a second delta-sigma-modulated signal, and a selector that receives the first delta-sigma-modulated signal and the second delta-sigma-modulated signal as input and selects and outputs either the first delta-sigma-modulated signal or the second delta-sigma-modulated signal based on the rectangular RF phase signal.

[0009] A method for controlling a digital modulator according to the present disclosure includes the steps of generating a phase signal and an amplitude signal from a baseband signal, generating an RF phase signal based on the phase signal, rectangularizing the RF phase signal to generate a rectangular RF phase signal, time interleaving the amplitude signal and outputting a first interleaved signal and a second time-interleaved signal, ΔΣ modulating the first interleaved signal and the second time-interleaved signal based on the rectangular RF phase signal to output a first ΔΣ modulated signal and a second ΔΣ modulated signal, and inputting the first ΔΣ modulated signal and the second ΔΣ modulated signal, and selecting and outputting either the first ΔΣ modulated signal or the second ΔΣ modulated signal based on the rectangular RF phase signal.

[0010] The program in the present disclosure causes a digital modulator to perform the following processes: generating a phase signal and an amplitude signal from a baseband signal; generating an RF phase signal based on the phase signal; rectangularizing the RF phase signal to generate a rectangular RF phase signal; time-interleaving the amplitude signal and outputting a first interleaved signal and a second time-interleaved signal; ΔΣ-modulating the first interleaved signal and the second time-interleaved signal based on the rectangular RF phase signal to output a first ΔΣ-modulated signal and a second ΔΣ-modulated signal; and inputting the first ΔΣ-modulated signal and the second ΔΣ-modulated signal and selecting and outputting either the first ΔΣ-modulated signal or the second ΔΣ-modulated signal based on the rectangular RF phase signal. [Effects of the Invention]

[0011] An object of the present disclosure is to provide a digital modulator, a communication device, a control method for a digital modulator, and a program that can simplify the components while widening the signal bandwidth. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a configuration diagram of a digital modulator according to a first embodiment of the present disclosure. [Figure 2] FIG. 10 is a configuration diagram of a digital modulator according to a second embodiment of the present disclosure. [Figure 3] FIG. 10 is a diagram showing a time chart of a time-interleaved amplitude signal according to a second embodiment of the present disclosure. [Figure 4] FIG. 10 is a block diagram of a time-interleaved ΔΣ modulator according to a second embodiment of the present disclosure. [Figure 5] FIG. 10 is a diagram illustrating noise characteristics of a time-interleaved ΔΣ modulator according to a second embodiment of the present disclosure. [Figure 6] FIG. 10 is a timing chart of a selector and a mixer according to a second embodiment of the present disclosure. [Figure 7] FIG. 10 is a configuration diagram of a digital modulator according to a third embodiment of the present disclosure. [Figure 8] FIG. 10 is a configuration diagram of a communication device according to a fourth embodiment of the present disclosure. [Figure 9] FIG. 10 is a configuration diagram of a communication device according to a fifth embodiment of the present disclosure. [Figure 10] 1 is a schematic diagram of a related optical fiber-based wireless access system. [Figure 11] FIG. 1 is a configuration diagram of a related communication device. [Figure 12] FIG. 1 is a configuration diagram of a related ΔΣ modulator. [Figure 13] FIG. 1 is a configuration diagram of a related RF signal modulator. [Figure 14] FIG. 1 is a block diagram of a related RF signal generator. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments will be described with reference to the drawings. Note that the drawings are simplified, and the technical scope of the embodiments should not be narrowly interpreted based on the description in the drawings. Furthermore, identical elements are given the same reference numerals, and duplicate explanations will be omitted.

[0014] In the following embodiments, when necessary for convenience, the description will be divided into multiple sections or embodiments. However, unless otherwise specified, they are not unrelated to each other, and one is a partial or complete modification, application example, detailed explanation, supplementary explanation, etc. of the other. Furthermore, in the following embodiments, when the number of elements (including the number, numerical value, amount, range, etc.) is mentioned, it is not limited to that specific number, and may be more or less than the specific number, unless otherwise specified or when it is clearly limited to a specific number in principle.

[0015] Furthermore, in the following embodiments, the components (including operational steps, etc.) are not necessarily essential unless otherwise specified or considered to be clearly essential in principle. Similarly, in the following embodiments, when referring to the shape, positional relationship, etc. of components, etc., it is intended to include those that are substantially similar or approximate to the shape, etc., unless otherwise specified or considered to be clearly not essential in principle. The same applies to the above numbers, etc. (including numbers, numerical values, amounts, ranges, etc.).

[0016] <Background of the study leading to the idea of ​​the digital modulator according to the embodiment> First, a related delta-sigma modulator will be described with reference to Fig. 11. The delta-sigma modulator used in the communication device shown in Fig. 11 can significantly reduce the quantization noise that occurs when binarizing the input signal in the vicinity of a desired band by operating at a speed that is sufficiently higher than the input signal frequency. In Fig. 11, a phase signal is used as the clock signal for the delta-sigma modulator, so the clock rate is fc.

[0017] Figure 12 shows the configuration of a related ΔΣ modulator. The ΔΣ modulator is composed of an adder, a delay, and a comparator, and the transfer function is expressed by the following equation (1), where IN(z) is the input signal and OUT(z) is the output signal. Note that N(z) is the quantization noise generated in the comparator, and f is the signal frequency. S is the operating frequency of the present ΔΣ modulator.

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[0018] As shown in equation (1), the quantization noise N(z) has a coefficient (1-z -1 ) is multiplied by the operating speed f S The larger z is compared to the frequency domain f that the input signal occupies, -1 approaches 1, which means that the noise component contained in the output signal is reduced and the signal-to-noise ratio (SNR) is improved.

[0019] On the other hand, the 1-bit signal generated by the digital modulator is generated by integrating the phase signal and the output signal of the ΔΣ modulator. The RF phase signal is a rectangularized sine wave signal with a carrier frequency of fc, so it alternates between low and high levels fc times per second. Therefore, the data rate is 2fc.

[0020] In the communication device shown in FIG. 11, the signal band is f bw In this case, in equation (1), the SN ratio is f bw If the signal is widened while keeping the carrier frequency constant, the coefficient of N(z) (1-z -1 ) increases, the noise component, (1-z -1 )·N(z) increases, and the SNR deteriorates. Therefore, the communication device shown in Fig. 11 has a problem in that it is not possible to widen the signal bandwidth without causing a deterioration in the SNR.

[0021] Figure 13 is a diagram showing the configuration of a related RF signal modulator. In the RF signal modulator shown in Figure 13, the output of a doubler that receives a phase signal as an input is used as the clock signal for a ΔΣ modulator, thereby achieving twice the wideband characteristics. However, the high cost of the doubler and the need to operate the ΔΣ modulator at twice the clock rate further increase the manufacturing costs of the ΔΣ modulator.

[0022] Figure 14 is a configuration diagram of a related RF signal generator. In the RF signal generator shown in Figure 14, the clock rate of the ΔΣ modulator is 2fc, which increases the SNR and enables the signal bandwidth to be widened. However, the signal rate is 4fc, which is twice the signal rate of the communication device shown in Figure 11. This increases the required characteristics of the optical modules used in the E / O and O / E converters, further increasing manufacturing costs.

[0023] The digital modulator of the present disclosure has been made to solve the problems of the background art as described above. Hereinafter, an embodiment of the digital modulator of the present disclosure will be described.

[0024] <Embodiment 1> The digital modulator 2 in this embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of the digital modulator 2 in this embodiment.

[0025] The digital modulator 2 includes a polar converter 3 , an RF phase signal generator 4 , a rectangular converter 5 , a time interleaver 6 , a ΔΣ modulator 7 , and a selector 8 .

[0026] The polar converter 3 generates a phase signal and an amplitude signal from the baseband signal. The RF phase signal generator 4 generates an RF phase signal based on the phase signal. The rectangularizer 5 rectangularizes the RF phase signal to generate a rectangular RF phase signal.

[0027] The time interleaver 6 time-interleaves the amplitude signal and outputs a first interleaved signal and a second time-interleaved signal. The delta-sigma modulator 7 delta-sigma-modulates the first interleaved signal and the second time-interleaved signal based on the rectangular RF phase signal, thereby outputting a first delta-sigma-modulated signal and a second delta-sigma-modulated signal.

[0028] The selector 8 receives the first ΔΣ modulated signal and the second ΔΣ modulated signal, and selects and outputs either the first ΔΣ modulated signal or the second ΔΣ modulated signal based on the rectangular RF phase signal.

[0029] According to the digital modulator 2 of this embodiment, it is possible to simplify the components and widen the signal bandwidth.

[0030] <Embodiment 2> The digital modulator 10 in this embodiment will be described with reference to Fig. 2. Fig. 2 is a configuration diagram of the digital modulator 10 in this embodiment.

[0031] The digital modulator 10 in this embodiment includes a baseband signal generator 11, a polar converter 12, an RF phase signal generator 13, a rectangular converter 14, a time interleaver 15, a time interleaved ΔΣ modulator 16, a selector 17, and a mixer 18. The time interleaved ΔΣ modulator 16 may be simply referred to as a ΔΣ modulator. The mixer 18 may also be referred to as a multiplier.

[0032] Baseband signal generator 11 generates a quadrature modulated signal (I(t), Q(t)), which is a wireless baseband signal. Baseband signal generator 11 outputs the generated quadrature modulated signal (I(t), Q(t)) to polar converter 12. The quadrature modulated signal (I(t), Q(t)) generated in baseband signal generator 11 is converted in polar converter 12 into an amplitude signal r(t) and a phase signal θ(t) according to the following equations (2) and (3).

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[0033] The phase signal is used as a phase control signal for the RF phase signal generator 13, and the output of the RF phase signal generator 13 becomes an RF phase signal RFθ(t) as shown in the following equation (4), where fc is the carrier frequency.

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[0034] A desired radio signal RF(t) with a carrier frequency fc is generally expressed as the following equation (5) using quadrature modulation signals I(t) and Q(t).

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[0035] Equation (5) can be written as the following equation (6) using the amplitude signal r(t) and phase signal θ(t) after polar conversion.

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[0036] The RF phase signal RFθ(t) is squared using a zero-comparison square wave converter 14 to generate a square RF phase signal RFθr(t). The square RF phase signal is a square wave having an oscillation frequency and a phase difference equal to the phase indicated by the phase signal, based on an oscillation signal and a phase signal that serve as a reference for the oscillation frequency, generated by an RF phase signal generator 13. RFθr(t) is used as a clock signal for a time-interleaved ΔΣ modulator 16 (described later), a control signal for a selector 17, and a second input signal for a mixer 18. RFθr(t) is the sum of RFθ(t) and a harmonic Hm(t) generated when RFθ(t) is squared, and is therefore RFθ(t)+Hm(t).

[0037] FIG. 3 shows a time chart of time interleaver 15. Time interleaver 15 time-interleaves amplitude signal r(t) to generate time-interleaved amplitude signal r_TI(t). r_TI(t) treats the data before and after the amplitude signal r(t) on the time axis as a set. Specifically, as shown in FIG. 3, the element data of r_TI(t) are represented as r1(t) for the previous data and r2(t) for the next data. The element data at the kth sample point are r1(k)=r(2k-1) and r2(k)=r(2k), respectively.

[0038] The time-interleaved delta-sigma modulator 16 performs delta-sigma modulation on the time-interleaved amplitude signal r_TI(t) by using the rectangular RF phase signal as a clock signal. A block diagram of the time-interleaved delta-sigma modulator 16 is shown in FIG. 4(b).

[0039] The input signals in1(t) and in2(t) and output signals out1(t) and out2(t) of the time-interleaved ΔΣ modulator 16 are time-interleaved signals. The relationships with the non-time-interleaved signals in(t) and out(t) are in1(k)=in(2k−1), in2(t)=in(2k), out1(k)=out(2k−1), and out2(k)=out(2k), respectively.

[0040] When the z-converted input signal and output signal of the time-interleaved ΔΣ modulator 16 are written as in(z) and out(z), respectively, the following relational expression (7) holds as a first-order ΔΣ modulator.

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[0041] The variable z is z=exp(2πj*f / fs), where f is the frequency, fs is the sampling frequency, and j is an imaginary number. In this configuration, the sampling frequency is effectively doubled to 2fs. Therefore, z is expressed by the following equation (8).

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[0042] Nq(z) is the quantization noise generated inside the ΔΣ modulator, and is white noise whose magnitude is independent of frequency. The second term on the right side of equation (7) for out(z) is the frequency characteristic N_TI of the noise of the time-interleaved ΔΣ modulator 16 shown in Figure 5. N_TI is expressed as follows:

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[0043] A block diagram of a non-time-interleaved ΔΣ modulator is shown in Figure 4(a). In this case, the output signal out_NTI(z) of the non-time-interleaved ΔΣ modulator is similarly expressed as the following equation (10). However, the relationship between z and f differs from that of the time-interleaved ΔΣ modulator 16 because the sampling frequency is effectively fs. Note that Nq_NTI(z) is the quantization noise generated in the non-time-interleaved ΔΣ modulator.

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[0044] When the second term on the right side of equation (10) is expressed as the frequency characteristic N_NTI of noise of the non-time interleaved ΔΣ modulator as shown in FIG. 5, it becomes as shown in equation (11) below.

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[0045] Here, the quantization noise per unit frequency decreases in inverse proportion to the sampling frequency. Therefore, the quantization noise generated in the time-interleaved ΔΣ modulator 16 is half of the quantization noise generated in a non-time-interleaved ΔΣ modulator, so Nq(z)=Nq_NTI(z) / 2.

[0046] As described above, the effective sampling frequency of the time-interleaved ΔΣ modulator 16 is 2 fs, and the effective sampling frequency of the non-time-interleaved ΔΣ modulator is half that, fs. Therefore, the following equation (12) holds:

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[0047] According to equation (12), this means that the noise characteristics of the non-time-interleaved ΔΣ modulator, expanded twice on the x-axis (frequency axis) and halved on the y-axis (magnitude axis), match the noise characteristics of the time-interleaved ΔΣ modulator 16. For example, as shown in Figure 5, if the noise of the non-time-interleaved ΔΣ modulator at frequency f_th is N_th, the noise of the time-interleaved ΔΣ modulator 16 at frequency 2f_th is N_th / 2.

[0048] If we define the noise characteristics as the amount obtained by integrating the frequency components from 0 to f as integrated noise, and let the integrated noise of the non-time-interleaved ΔΣ modulator and the time-interleaved ΔΣ modulator 16 be INT_N_NTI(f) and INT_N_TI(f), respectively, then the following equation (13) holds:

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[0049] According to equation (13), the bandwidth in which a certain integrated noise is reached is twice as wide in the time-interleaved ΔΣ modulator 16 as in the non-time-interleaved ΔΣ modulator. The operating bandwidth of a ΔΣ modulator is defined as the bandwidth in which an arbitrarily determined integrated noise is reached. Therefore, the bandwidth of the time-interleaved ΔΣ modulator 16 is twice as wide as that of the non-time-interleaved ΔΣ modulator.

[0050] Next, the operations of the selector 17 and the mixer 18 will be described with reference to Fig. 6. Fig. 6 is a time chart of the selector 17 and the mixer 18 at the subsequent stage.

[0051] The selector 17 receives the time-interleaved output signal of the time-interleaved ΔΣ modulator 16. The first input terminal receives an element signal r1(t) of the time-interleaved signal, and the second input terminal receives r2(t). The control terminal of the selector 17 receives a rectangular RF phase signal RFθr(t).

[0052] When a high signal is input to the control terminal, the selector 17 outputs from its output terminal the signal input to its first input terminal, and when a low signal is input, the selector 17 outputs from its output terminal the signal input to its second input terminal. The output signal of the selector 17 is a non-time-interleaved signal. Note that the time-interleaved ΔΣ modulator 16 in the preceding stage operates in synchronization with the rectangular RF phase signal, so the sampling frequency, i.e., the data rate, is fc. On the other hand, the output signal of the selector 17 selects output data depending on the high and low levels of the rectangular RF phase signal, so the data rate is 2fc.

[0053] Mixer 18, located downstream of selector 17, multiplies a first input signal input to its first input terminal by a second input signal input to its second input terminal. The first input signal is the output signal selected by selector 17, and the second input signal is a rectangular RF phase signal. Mixer 18 assigns +1 to the high signal and -1 to the low signal of the rectangular RF phase signal.

[0054] The output signal of the selector 17 corresponds to a signal obtained by converting the time-interleaved signal output from the time-interleaved ΔΣ modulator 16 into a non-time-interleaved signal. If the amplitude signal is r(t) and the noise signal added by the ΔΣ modulator is N_TI(t), the output signal Sout(t) from the selector 17 is written as shown in the following equation (14).

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[0055] MIXout(t), which is the output from the mixer 18, is the product of Sout(t) and RFθr(t), and is therefore given by the following equation (15).

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[0056] As shown in equation (15), the output signal MIXout(t) of the mixer 18 contains the radio signal RF(t). The waveform of the output signal of the mixer 18 is rectangular. In MIXout(t), Hm(t) generally has peaks at integer multiples of the carrier frequency fc. Therefore, the product r(t) · Hm(t) of MIXout(t) and the amplitude signal r(t) also has peaks at integer multiples of the carrier frequency fc. Because the desired signal is near fc, the peak components of r(t)Hm(t) can be sufficiently removed without affecting the desired signal by using a high-frequency filter. Therefore, N_TI(t) · RFθr(t) is the dominant noise component near fc. Because N_TI(t) is the noise characteristic of the ΔΣ modulator, given the signal-to-noise characteristic specifications, the operable bandwidth must satisfy the noise characteristics of N_TI(t).

[0057] As described above, in terms of noise characteristics of the time-interleaved ΔΣ modulator 16, the band that satisfies the specifications is twice that of a non-time-interleaved ΔΣ modulator.

[0058] In this embodiment, that is, in the form using the time-interleaved ΔΣ modulator 16, the operating band is doubled compared to when a non-time-interleaved ΔΣ modulator is used, even though the clock is fc.

[0059] The digital modulator 10 of this embodiment can further widen the signal bandwidth without degrading the SNR. Furthermore, the digital modulator 10 can reduce costs without causing the clock rate of the ΔΣ modulator to exceed fc.

[0060] <Embodiment 3> The digital modulator 10 in this embodiment will be described with reference to Fig. 7. Fig. 7 is a diagram showing the configuration of the digital modulator 10 in this embodiment.

[0061] The digital modulator 10 in this embodiment includes a baseband signal generator 11, a polar converter 12, an RF phase signal generator 13, a rectangular converter 14, a time interleaver 15, a time interleaved ΔΣ modulator 16, a selector 17, and an inverter circuit 19.

[0062] The baseband signal generator 11, polar converter 12, RF phase signal generator 13, rectangularizer 14, time interleaver 15, time interleaved ΔΣ modulator 16 and selector 17 are the same as those in embodiment 2, so detailed explanations of these will be omitted.

[0063] The difference from the second embodiment is in the subsequent stage of the time-interleaved ΔΣ modulator 16. One of the component signals in the output signal of the time-interleaved ΔΣ modulator 16 is inverted using an inverter circuit 19 and input to a selector 17. The output signal of the selector 17 becomes the output signal in this embodiment.

[0064] Fig. 6 shows a time chart of the selector 17 in this embodiment. In Fig. 6, the output of the selector 17 in this embodiment is Soutx, the first input signal of the selector 17 is r1(t), and the second input signal is r2b(t), which is an inverted signal of r2(t).

[0065] 6, Soutx in this embodiment is the same as the output signal MIXout of the mixer 18 in embodiment 2. This means that the signal processing in this embodiment is the same as the signal processing in embodiment 2. Furthermore, compared to embodiment 2, this embodiment does not require the mixer 18, and therefore can be realized with a simpler circuit configuration.

[0066] <Embodiment 4> The communication device 1 in this embodiment will be described with reference to Fig. 8. Fig. 8 is a configuration diagram of the communication device 1 in this embodiment. In this embodiment, the communication device 1 includes a digital modulator A and a digital modulator B that share a baseband signal generating unit 11.

[0067] The rectangularizer 14, time interleaver 15, time interleaved ΔΣ modulator 16, selector 17, and mixer 18 that constitute digital modulators A and B are circuits similar to the circuit blocks of the same names that constitute embodiment 2 described in Figure 2, and their mutual connection relationships are also similar, so detailed explanations of these will be omitted.

[0068] In this embodiment, the quadrature radio signals (I, Q) generated in the baseband signal generating unit 11 are input to digital modulators A and B, respectively, and converted into pulse signals. Furthermore, an output from an RF phase signal generator 13 with an oscillation frequency fc is input to digital modulator A, and a signal that is 90° phase delayed from the output signal from the same RF phase signal generator 13 is input to digital modulator B.

[0069] The output signals of the digital modulators A and B are combined via fiber transmission using wavelength division multiplexing. The output signal MIXoutA(t) of the digital modulator A is expressed by the following equation (16) by replacing r(t) with I(t) and RFθr(t) with cos(ωct)+HmA(t) in equation (15) for MIXout(t) in the second embodiment. Note that HmA(t) is a harmonic component generated when the output signal of the RF phase signal generator 13 is squared inside the digital modulator A. Furthermore, N_TI_A(t) is quantization noise generated in the time-interleaved ΔΣ modulator 16 inside the digital modulator A.

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[0070] Similarly, the output signal MIXoutB(t) of digital modulator B is expressed as the following equation (17) by replacing r(t) with Q(t) and RFθr(t) with sin(ωct)+HmB(t) in equation (15) for MIXout(t) in embodiment 2. Here, HmB(t) is a harmonic component that is generated when the output signal of the RF phase signal generator 13 is squared inside the digital modulator B. Also, N_TI_B(t) is a quantization noise that is generated in the time-interleaved ΔΣ modulator 16 inside the digital modulator B.

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[0071] The combined signal comb(t) after fiber transmission is the sum of MIXoutA(t) and MIXoutB(t), as shown in the following equation (18): According to equation (18), comb(t) contains the desired RF signal.

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[0072] In this embodiment, as in the case where a non-time-interleaved ΔΣ modulator is used, the clock rate of the time-interleaved ΔΣ modulator 16 is fc, and the rate of the output signals of the digital modulators A and B is 2fc. As described above, the bandwidth that satisfies the specifications in terms of noise characteristics of the time-interleaved ΔΣ modulator 16 is twice that when a non-time-interleaved ΔΣ modulator is used.

[0073] As described above, in this embodiment, that is, in the configuration using the time-interleaved ΔΣ modulator 16, the operating band is doubled compared to the case where a non-time-interleaved ΔΣ modulator is used.

[0074] <Embodiment 5> The communication device 1 in this embodiment will be described with reference to Fig. 9. Fig. 9 is a configuration diagram of the communication device 1 in this embodiment. The communication device 1 in this embodiment has a configuration in which the digital modulators A and B used in embodiment 4 are replaced with digital modulators 8-A and 8-B, respectively.

[0075] The rectangular converter 14, time interleaver 15, time interleaved ΔΣ modulator 16, selector 17, and inverter circuit 19 that constitute the digital modulators 8-A and 8-B are circuits similar to the circuit blocks of the same names that constitute the digital modulator 10 in embodiment 3, and their mutual connection relationships are also similar, so detailed explanations of these will be omitted.

[0076] The signals generated in digital modulators 8-A and 8-B are equal to the signals generated in digital modulators A and B. Therefore, in this embodiment, as in embodiment 4 shown in FIG. 8, the operating bandwidth is doubled compared to when a non-time-interleaved ΔΣ modulator is used. By implementing time interleaving, the rate of the externally applied clock is fc, but the clock frequency of the time-interleaved ΔΣ modulator 16 is virtually doubled. In equation (1), since fs is doubled, a wider bandwidth can be achieved without degrading the SNR.

[0077] <Other embodiments> The digital modulator 10 of the present disclosure includes, for example, an embodiment as a control method. That is, the control method includes the steps of generating a phase signal and an amplitude signal from a baseband signal, generating an RF phase signal based on the phase signal, rectangularizing the RF phase signal to generate a rectangular RF phase signal, time-interleaving the amplitude signal and outputting a first interleaved signal and a second time-interleaved signal, ΔΣ-modulating the first interleaved signal and the second time-interleaved signal based on the rectangular RF phase signal to output a first ΔΣ-modulated signal and a second ΔΣ-modulated signal, and inputting the first ΔΣ-modulated signal and the second ΔΣ-modulated signal, and selecting and outputting either the first ΔΣ-modulated signal or the second ΔΣ-modulated signal based on the rectangular RF phase signal.

[0078] In the above example, the program can be stored and supplied to a computer using various types of non-transitory computer-readable media. Non-transitory computer-readable media include various types of tangible storage media. Non-transitory computer-readable media include, for example, magnetic recording media, magneto-optical recording media, CD-ROMs, CD-Rs, CD-R / Ws, and semiconductor memories. Semiconductor memories include, for example, mask ROMs, programmable ROMs (PROMs), erasable PROMs (EPROMs), flash ROMs, and RAMs. The program may also be supplied to a computer by various types of transitory computer-readable media. Examples of transitory computer-readable media include electrical signals, optical signals, and electromagnetic waves. The transitory computer-readable media can supply the program to a computer via wired communication paths such as electrical wires and optical fibers, or via wireless communication paths.

[0079] The above program causes digital modulator 10 to execute the following processes: generating a phase signal and an amplitude signal from a baseband signal; generating an RF phase signal based on the phase signal; rectangularizing the RF phase signal to generate a rectangular RF phase signal; time interleaving the amplitude signal and outputting a first interleaved signal and a second time-interleaved signal; ΔΣ modulating the first interleaved signal and the second time-interleaved signal based on the rectangular RF phase signal to output a first ΔΣ modulated signal and a second ΔΣ modulated signal; and inputting the first ΔΣ modulated signal and the second ΔΣ modulated signal, and selecting and outputting either the first ΔΣ modulated signal or the second ΔΣ modulated signal based on the rectangular RF phase signal.

[0080] The embodiments of the present disclosure have been described in detail above with reference to the drawings, but the specific configurations are not limited to those described above, and various design changes and the like are possible within the scope that does not deviate from the gist of the present disclosure.

[0081] Some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes. (Appendix 1) a polar converter that generates a phase signal and an amplitude signal from a baseband signal; an RF phase signal generator that generates an RF phase signal based on the phase signal; a squarer that squares the RF phase signal to generate a squared RF phase signal; a time interleaver that time-interleaves the amplitude signal and outputs a first interleaved signal and a second time-interleaved signal; a ΔΣ modulator that outputs a first ΔΣ modulated signal and a second ΔΣ modulated signal by ΔΣ modulating the first interleaved signal and the second time-interleaved signal based on the rectangular RF phase signal; a selector that receives the first ΔΣ modulated signal and the second ΔΣ modulated signal, and selects and outputs either the first ΔΣ modulated signal or the second ΔΣ modulated signal based on the rectangular RF phase signal; A digital modulator comprising: (Appendix 2) The rectangular RF phase signal is The RF phase signal generator generates a rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on the oscillation signal that is a reference for the oscillation frequency and the phase signal. 10. The digital modulator of claim 1. (Appendix 3) The selector selecting either the first ΔΣ modulated signal or the second ΔΣ modulated signal based on whether the rectangular RF phase signal is at a high level or a low level; 3. A digital modulator according to claim 1 or 2. (Appendix 4) The ΔΣ modulator is ΔΣ modulation of the first interleaved signal and the second time-interleaved signal by using the rectangular RF phase signal as a clock signal; 4. The digital modulator according to any one of claims 1 to 3. (Appendix 5) further comprising a multiplier that multiplies the first ΔΣ modulated signal or the second ΔΣ modulated signal selected by the selector by the rectangular RF phase signal; 5. The digital modulator according to any one of appendices 1 to 4. (Appendix 6) further comprising an inversion circuit that inverts the second ΔΣ modulated signal, and inputs the inverted second ΔΣ modulated signal to the selector; 6. The digital modulator according to any one of appendices 1 to 5. (Appendix 7) a digital modulator; and an optical module that performs signal processing based on an output signal of the digital modulator; Equipped with The digital modulator comprises: a polar converter that generates a phase signal and an amplitude signal from a baseband signal; an RF phase signal generator that generates an RF phase signal based on the phase signal; a squarer that squares the RF phase signal to generate a squared RF phase signal; a time interleaver that time-interleaves the amplitude signal and outputs a first interleaved signal and a second time-interleaved signal; a ΔΣ modulator that outputs a first ΔΣ modulated signal and a second ΔΣ modulated signal by ΔΣ modulating the first interleaved signal and the second time-interleaved signal based on the rectangular RF phase signal; a selector that receives the first ΔΣ modulated signal and the second ΔΣ modulated signal, and selects and outputs either the first ΔΣ modulated signal or the second ΔΣ modulated signal based on the rectangular RF phase signal; Communication equipment. (Appendix 8) The rectangular RF phase signal is The RF phase signal generator generates a rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on the oscillation signal that is a reference for the oscillation frequency and the phase signal. 8. The communication device of claim 7. (Appendix 9) The selector selecting either the first ΔΣ modulated signal or the second ΔΣ modulated signal based on whether the rectangular RF phase signal is at a high level or a low level; 9. The communication device according to claim 7 or 8. (Appendix 10) The ΔΣ modulator is ΔΣ modulation of the first interleaved signal and the second time-interleaved signal by using the rectangular RF phase signal as a clock signal; 10. The communication device according to any one of appendices 7 to 9. (Appendix 11) further comprising a multiplier that multiplies the first ΔΣ modulated signal or the second ΔΣ modulated signal selected by the selector by the rectangular RF phase signal; 11. The communication device according to any one of appendices 7 to 10. (Appendix 12) The digital modulator comprises: further comprising an inversion circuit that inverts the second ΔΣ modulated signal, and inputs the inverted second ΔΣ modulated signal to the selector; 12. The communication device according to any one of Supplementary notes 7 to 11. (Appendix 13) generating a phase signal and an amplitude signal from the baseband signal; generating an RF phase signal based on the phase signal; square-square the RF phase signal to generate a square-square RF phase signal; time-interleaving the amplitude signal to output a first interleaved signal and a second time-interleaved signal; outputting a first ΔΣ modulated signal and a second ΔΣ modulated signal by ΔΣ modulating the first interleaved signal and the second time-interleaved signal based on the rectangular RF phase signal; a step of inputting the first ΔΣ modulated signal and the second ΔΣ modulated signal, selecting and outputting either the first ΔΣ modulated signal or the second ΔΣ modulated signal based on the rectangular RF phase signal; A method for controlling a digital modulator comprising: (Appendix 14) The rectangular RF phase signal is A rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on an oscillation signal that is a reference for the oscillation frequency and the phase signal. 14. A method for controlling a digital modulator according to claim 13. (Appendix 15) further comprising a step of multiplying the first ΔΣ modulated signal or the second ΔΣ modulated signal by the rectangular RF phase signal. 15. A method for controlling a digital modulator according to claim 13 or 14. (Appendix 16) generating a phase signal and an amplitude signal from the baseband signal; generating an RF phase signal based on the phase signal; rectangularizing the RF phase signal to generate a rectangular RF phase signal; time-interleaving the amplitude signal to output a first interleaved signal and a second time-interleaved signal; a process of outputting a first ΔΣ modulated signal and a second ΔΣ modulated signal by ΔΣ modulating the first interleaved signal and the second time-interleaved signal based on the rectangular RF phase signal; a process of inputting the first ΔΣ modulated signal and the second ΔΣ modulated signal, and selecting and outputting either the first ΔΣ modulated signal or the second ΔΣ modulated signal based on the rectangular RF phase signal; A program that causes the digital modulator to execute the above. (Appendix 17) The rectangular RF phase signal is A rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on an oscillation signal that is a reference for the oscillation frequency and the phase signal. 16. The program described in Appendix 16. (Appendix 18) further comprising a step of multiplying the first ΔΣ modulated signal or the second ΔΣ modulated signal by the rectangular RF phase signal. 18. The program according to claim 16 or 17. [Explanation of symbols]

[0082] 1. Communications equipment 2, 10 Digital Modulator 11 Baseband signal generator 3, 12 polar converter 4, 13 RF phase signal generator 5, 14 Rectangularizer 6, 15 Time Interleaver 7 Delta-Sigma Modulator 8, 17 selector 16 Time-interleaved ΔΣ modulator 18 Mixer 19 Inverting circuit

Claims

1. a polar converter that generates a phase signal and an amplitude signal from a baseband signal; an RF phase signal generator that generates an RF phase signal based on the phase signal; a squarer for square-rectifying the RF phase signal to generate a square-rectangular RF phase signal; a time interleaver that time-interleaves the amplitude signal and outputs a first time-interleaved signal and a second time-interleaved signal; a ΔΣ modulator that uses the rectangular RF phase signal as a clock signal to ΔΣ-modulate the first time-interleaved signal and the second time-interleaved signal in synchronization with the rectangular RF phase signal, and outputs a first ΔΣ-modulated signal and a second ΔΣ-modulated signal, which are time-interleaved signals; a selector that receives the first ΔΣ modulated signal and the second ΔΣ modulated signal, selects either the first ΔΣ modulated signal or the second ΔΣ modulated signal in synchronization with the rectangular RF phase signal based on whether the rectangular RF phase signal is at a high level or a low level, and outputs a non-time-interleaved signal; a multiplier that multiplies the first ΔΣ modulated signal or the second ΔΣ modulated signal selected by the selector by the rectangular RF phase signal; Equipped with The rectangular RF phase signal is a rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on an oscillation signal that is a reference for an oscillation frequency and the phase signal, which are generated by the RF phase signal generator. Digital modulator.

2. a polar converter that generates a phase signal and an amplitude signal from a baseband signal; an RF phase signal generator that generates an RF phase signal based on the phase signal; a squarer for square-rectifying the RF phase signal to generate a square-rectangular RF phase signal; a time interleaver that time-interleaves the amplitude signal and outputs a first time-interleaved signal and a second time-interleaved signal; a ΔΣ modulator that uses the rectangular RF phase signal as a clock signal to ΔΣ-modulate the first time-interleaved signal and the second time-interleaved signal in synchronization with the rectangular RF phase signal, and outputs a first ΔΣ-modulated signal and a second ΔΣ-modulated signal, which are time-interleaved signals; a selector that receives the first ΔΣ modulated signal and the second ΔΣ modulated signal, selects either the first ΔΣ modulated signal or the second ΔΣ modulated signal in synchronization with the rectangular RF phase signal based on whether the rectangular RF phase signal is at a high level or a low level, and outputs a non-time-interleaved signal; Equipped with the rectangular RF phase signal is a rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on an oscillation signal that is a reference for an oscillation frequency and the phase signal, which are generated by the RF phase signal generator; further comprising an inversion circuit that inverts the second ΔΣ modulated signal, and inputs the inverted second ΔΣ modulated signal to the selector; Digital modulator.

3. a digital modulator; and an optical module that performs signal processing based on an output signal of the digital modulator; Equipped with The digital modulator comprises: a polar converter that generates a phase signal and an amplitude signal from a baseband signal; an RF phase signal generator that generates an RF phase signal based on the phase signal; a squarer for square-rectifying the RF phase signal to generate a square-rectangular RF phase signal; a time interleaver that time-interleaves the amplitude signal and outputs a first time-interleaved signal and a second time-interleaved signal; a ΔΣ modulator that uses the rectangular RF phase signal as a clock signal to ΔΣ-modulate the first time-interleaved signal and the second time-interleaved signal in synchronization with the rectangular RF phase signal, and outputs a first ΔΣ-modulated signal and a second ΔΣ-modulated signal, which are time-interleaved signals; a selector that receives the first ΔΣ modulated signal and the second ΔΣ modulated signal, selects either the first ΔΣ modulated signal or the second ΔΣ modulated signal in synchronization with the rectangular RF phase signal based on whether the rectangular RF phase signal is at a high level or a low level, and outputs a non-time-interleaved signal; a multiplier that multiplies the first ΔΣ modulated signal or the second ΔΣ modulated signal selected by the selector by the rectangular RF phase signal; Equipped with The rectangular RF phase signal is a rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on an oscillation signal that is a reference for an oscillation frequency and the phase signal, which are generated by the RF phase signal generator. Communication equipment.

4. a digital modulator; and an optical module that performs signal processing based on an output signal of the digital modulator; Equipped with The digital modulator comprises: a polar converter that generates a phase signal and an amplitude signal from a baseband signal; an RF phase signal generator that generates an RF phase signal based on the phase signal; a squarer for square-rectifying the RF phase signal to generate a square-rectangular RF phase signal; a time interleaver that time-interleaves the amplitude signal and outputs a first time-interleaved signal and a second time-interleaved signal; a ΔΣ modulator that uses the rectangular RF phase signal as a clock signal to ΔΣ-modulate the first time-interleaved signal and the second time-interleaved signal in synchronization with the rectangular RF phase signal, and outputs a first ΔΣ-modulated signal and a second ΔΣ-modulated signal, which are time-interleaved signals; a selector that receives the first ΔΣ modulated signal and the second ΔΣ modulated signal, selects either the first ΔΣ modulated signal or the second ΔΣ modulated signal in synchronization with the rectangular RF phase signal based on whether the rectangular RF phase signal is at a high level or a low level, and outputs a non-time-interleaved signal; Equipped with the rectangular RF phase signal is a rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on an oscillation signal that is a reference for an oscillation frequency and the phase signal, which are generated by the RF phase signal generator; further comprising an inversion circuit that inverts the second ΔΣ modulated signal, and inputs the inverted second ΔΣ modulated signal to the selector; Communication equipment.

5. generating a phase signal and an amplitude signal from the baseband signal; generating an RF phase signal based on the phase signal; square-square the RF phase signal to generate a square-square RF phase signal; time-interleaving the amplitude signal to output a first time-interleaved signal and a second time-interleaved signal; a step of ΔΣ modulating the first time-interleaved signal and the second time-interleaved signal in synchronization with the rectangular RF phase signal by using the rectangular RF phase signal as a clock signal, and outputting a first ΔΣ modulated signal and a second ΔΣ modulated signal, which are time-interleaved signals; a step of inputting the first ΔΣ modulated signal and the second ΔΣ modulated signal, selecting either the first ΔΣ modulated signal or the second ΔΣ modulated signal in synchronization with the rectangular RF phase signal based on whether the rectangular RF phase signal is at a high level or a low level, and outputting a non-time-interleaved signal; multiplying the selected one of the first ΔΣ modulated signal and the second ΔΣ modulated signal by the rectangular RF phase signal; Equipped with the rectangular RF phase signal is a rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on an oscillation signal that is a reference for an oscillation frequency and the phase signal, which are generated in the step of generating the RF phase signal. A method for controlling a digital modulator.

6. generating a phase signal and an amplitude signal from the baseband signal; generating an RF phase signal based on the phase signal; square-square the RF phase signal to generate a square-square RF phase signal; time-interleaving the amplitude signal to output a first time-interleaved signal and a second time-interleaved signal; a step of ΔΣ modulating the first time-interleaved signal and the second time-interleaved signal in synchronization with the rectangular RF phase signal by using the rectangular RF phase signal as a clock signal, and outputting a first ΔΣ modulated signal and a second ΔΣ modulated signal, which are time-interleaved signals; a step of inputting the first ΔΣ modulated signal and the second ΔΣ modulated signal, selecting either the first ΔΣ modulated signal or the second ΔΣ modulated signal in synchronization with the rectangular RF phase signal based on whether the rectangular RF phase signal is at a high level or a low level, and outputting a non-time-interleaved signal; Equipped with the rectangular RF phase signal is a rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on an oscillation signal that is a reference for an oscillation frequency and the phase signal, which are generated in the step of generating the RF phase signal; further comprising a step of inverting the second ΔΣ modulated signal, and inputting the inverted second ΔΣ modulated signal to the step of selecting and outputting the non-time-interleaved signal; A method for controlling a digital modulator.

7. generating a phase signal and an amplitude signal from the baseband signal; generating an RF phase signal based on the phase signal; square-square the RF phase signal to generate a square-square RF phase signal; time-interleaving the amplitude signal to output a first time-interleaved signal and a second time-interleaved signal; a process of ΔΣ modulating the first time-interleaved signal and the second time-interleaved signal in synchronization with the rectangular RF phase signal by using the rectangular RF phase signal as a clock signal, and outputting a first ΔΣ modulated signal and a second ΔΣ modulated signal, which are time-interleaved signals; a process of inputting the first ΔΣ modulated signal and the second ΔΣ modulated signal, selecting either the first ΔΣ modulated signal or the second ΔΣ modulated signal in synchronization with the rectangular RF phase signal based on whether the rectangular RF phase signal is at a high level or a low level, and outputting a non-time-interleaved signal; multiplying the selected first ΔΣ modulated signal or the selected second ΔΣ modulated signal by the rectangular RF phase signal; is executed by the digital modulator, The rectangular RF phase signal is a rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on an oscillation signal that is a reference for an oscillation frequency and the phase signal, which are generated in a process of generating the RF phase signal. program.

8. generating a phase signal and an amplitude signal from the baseband signal; generating an RF phase signal based on the phase signal; square-square the RF phase signal to generate a square-square RF phase signal; time-interleaving the amplitude signal to output a first time-interleaved signal and a second time-interleaved signal; a process of ΔΣ modulating the first time-interleaved signal and the second time-interleaved signal in synchronization with the rectangular RF phase signal by using the rectangular RF phase signal as a clock signal, and outputting a first ΔΣ modulated signal and a second ΔΣ modulated signal, which are time-interleaved signals; a process of inputting the first ΔΣ modulated signal and the second ΔΣ modulated signal, selecting either the first ΔΣ modulated signal or the second ΔΣ modulated signal in synchronization with the rectangular RF phase signal based on whether the rectangular RF phase signal is at a high level or a low level, and outputting a non-time-interleaved signal; is executed by the digital modulator, the rectangular RF phase signal is a rectangular wave having an oscillation frequency and a phase difference with respect to the oscillation signal that is equal to the phase indicated by the phase signal, based on an oscillation signal that is a reference for an oscillation frequency and the phase signal, which are generated in a process of generating the RF phase signal; further causing the digital modulator to perform a process of inverting the second ΔΣ modulated signal, and inputting the inverted second ΔΣ modulated signal to the process of selecting and outputting the non-time-interleaved signal; program.

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