JP4713435B2 - Delta-sigma modulator - Google Patents

Description

  The present invention relates to a delta-sigma modulation apparatus that modulates an input signal by delta-sigma modulation to a quantized signal, and more particularly to a delta-sigma modulation apparatus that superimposes an input signal in a band in which quantization noise in the frequency characteristics of quantization noise is reduced. About.

FIG. 15 is a block diagram illustrating a configuration of a conventional delta-sigma modulation circuit, and FIG. 16 is a graph illustrating a frequency characteristic of a quantization noise distribution of a quantized signal output from the conventional delta-sigma modulation circuit.
For example, referring to FIG. 15, a conventional delta sigma modulation circuit 20 that performs delta sigma modulation on an input signal to modulate a quantized signal includes seven integration elements F1,. Multipliers Aa1 to Aa7 interposed in front of the integration elements F1 to F7, respectively. Each of the integration elements F1 to F7 includes a delay device that delays the output by one sampling period (Ts: 1 / sample frequency fs), and an adder that adds the output from the delay device to the input signal and outputs it. Therefore, the previous output signal for one sampling period is added to the input signal from the previous stage side, and the output signal to the next stage side is created.

  An analog signal or a multi-bit digital signal input as an input signal X to the input terminal P1 is supplied to the first stage integration element F1 via the adder Cb and the first stage multiplier Aa1. Input to the integration element F1 at the stage, and outputs of the integration elements F1 to F6 are respectively input to the integration elements F2 to F7 of the next stage via the multipliers Aa2 to Aa7, and outputs from the integration elements F1 to F7. Are added to each other by the adder Cc and then input to the quantizer 10. The quantizer 10 compares the output from the adder Cc with a predetermined value, for example, 0 level for each sampling frequency fs, and outputs an output terminal when the output from the adder Cc is a predetermined value, for example, 0 level or more. The output signal Y to P2 is “1”, and is “−1” when it is less than a predetermined value. Further, the output signal Y from the quantizer 10 is negatively fed to the adder Cb interposed in the preceding stage of the first-stage multiplier Aa1 through the delayer D1 and the multiplier Ab that are delayed by m sampling periods. It has been returned.

  Further, adders Cd1 to Cd3 are interposed in front of the integration elements F2, F4, and F6, respectively, and delay elements D2 to D4 that delay the outputs of the integration elements F3, F5, and F7 by one sampling period and multiplications. Three partial negative feedback loops are respectively fed back to the adders Cd1 to Cd3 interposed in the preceding stage of the first-stage multiplier Aa1 through the units Ac1 to Ac3, respectively.

  FIG. 16 shows the frequency characteristics of the quantization noise distribution of the conventional delta-sigma modulation device shown in FIG. 15, and the quantization noise is shifted to the high frequency band side, and the quantization noise is reduced to near zero. A band is formed and three dips are formed by three partial negative feedback loops.

  In the delta-sigma modulation circuit, the signal input in the band where the quantization noise is small is superimposed. However, the additional information signal generation circuit is provided, and the signal having the carrier frequency at which the dip is formed as the channel information And a signal multiplexing technique for superimposing channel information on the frequency at which the dip is formed together with the main signal (input signal) of the quantized signal. (For example, refer to Patent Document 1).

However, in the prior art, since the dip formed by the partial negative feedback loop is formed in a band where the quantization noise on which the main signal is superimposed is small, the data amount of the signal superimposed on the frequency at which the dip is formed is small. There is a problem in that a signal having the same amount of data as the main signal cannot be superimposed.
Japanese Patent Laid-Open No. 10-322215

  The present invention has been made in view of such problems, and an object of the present invention is to form a plurality of signals in a frequency band apart from a band in which quantization noise capable of superimposing a plurality of signals is small. It is in providing a delta-sigma modulator that can be used.

In order to solve the above problems, the present invention has the following configuration.
Delta-sigma modulator of the present invention, vertical and continue a plurality of connected integrating means, and adding means for adding outputs from each integrating means, the output from the adding means is quantized based on the sampling frequency Quantum A quantizing means for outputting a quantized signal; and a negative feedback loop for negatively feeding back the output from the quantizing means to the integrating means at the first stage, and the quantizing of the input signal input to the integrating means at the first stage In the delta-sigma modulation apparatus that modulates a signal, the plurality of integrating means includes a plurality of delay units that are cascaded by one sampling period , and a first delay unit that delays an output by a sampling period corresponding to the number of the delay units . delay means, each comprise addition means for adding the output from said first delay means to the input, the negative feedback loop, cascaded first delay means and the same number of the delay units The output from the quantizing means is negatively fed back to the integrating means in the first stage via the second delay means for delaying the input by the same number of sampling periods as the first delay means, and the output from the quantizing means In the frequency characteristic of the quantization noise of the quantized signal, a plurality of bands where the quantization noise is small are formed between the frequency 0 and the frequency fs / 2 at the turn-back position sandwiching the band where the quantization noise is large. It is not characterized by Rukoto.

Further, in the delta-sigma modulation apparatus according to the present invention, the first delay means and the second delay means are delay means for delaying only two sampling periods by cascading two delay elements that delay one sampling period. And in the frequency characteristics of the quantization noise of the quantized signal output from the quantization means, a band where the quantization noise is reduced is formed in a band near the frequency 0 and a band near the frequency fs / 2. Features.

Further, in the delta-sigma modulation apparatus according to the present invention, the first delay means and the second delay means are connected by four delay devices that delay one sampling period , and delay means that delays four sampling periods. Yes, in the frequency characteristics of the quantization noise of the quantized signal output from the quantization means, the quantization noise is small in a band near frequency 0, a band near frequency fs / 4, and a band near frequency fs / 2. A band is formed.

  The delta-sigma modulation apparatus of the present invention includes a plurality of integrating means each including a first delay means for delaying an output by a plurality of sampling periods and an adding means for adding an output from the delay means to an input, The output from the adding means for adding the outputs from the means is quantized by the quantizing means based on the sampling frequency fs and modulated into a quantized signal, and the input is delayed by the same number of sampling periods as the first delay means. In the frequency characteristic of the quantization noise of the quantized signal output from the quantizing means, a plurality of signals are output by negatively feeding back the output from the quantizing means via the delay means. Can be formed in a frequency band apart from the band where the quantization noise that can be superimposed on each other is small. That a plurality of each can be superimposed with different signals in the band, an effect that a plurality of signals can be created quantized signals multiplexed. Further, the band where the quantization noise formed by the delta-sigma modulation apparatus of the present invention is small is the folding position sandwiching the band where the quantization noise is large, that is, fs * k / N (N is a natural number, k is Since each frequency band is an integer in the range of 0 ≦ k <(N + 1) / 2), it is possible to superimpose a plurality of signals having the same amount of data. Furthermore, when creating a dip by increasing integration means for partial negative feedback, it is necessary to redesign the coefficients for stabilization. In the delta-sigma modulation device of the present invention, the first delay means and Since only the delay time in the second delay means is changed, the coefficient designed by the conventional method can be used as it is, and the design is easy.

  Furthermore, in the delta-sigma modulation apparatus of the present invention, the first delay means for delaying the input by a plurality of sampling periods and the second delay means using a structure in which a plurality of delay means for delaying by one sampling period are connected in cascade. With this configuration, it is possible to appropriately set the number of bands in which the quantization noise to be formed is small by simply overlapping a plurality of delay means for delaying by one sampling period, and there is an effect that the design is easy. .

  Furthermore, in the delta-sigma modulation device of the present invention, the first delay means and the second delay means that are delayed by two sampling periods are used, and the frequency characteristics of the quantization noise of the quantized signal output from the quantizing means are used. By forming a band in which the quantization noise is small in a band near the frequency 0 and a band near the frequency fs / 2, it is represented by only binary values that are repetitions of “+1, −1”. By using only a square-wave carrier signal, there is an effect that the signal superimposed on the band where the quantization noise near the frequency fs / 2 is small can be easily frequency-shifted.

  Furthermore, in the delta-sigma modulation apparatus of the present invention, the first delay means and the second delay means that are delayed by four sampling periods are used, and the frequency characteristics of the quantization noise of the quantized signal output from the quantizing means are used. It is a repetition of “+1, −1” by forming a band in which quantization noise is reduced in a band near frequency 0, a band near frequency fs / 4, and a band near frequency fs / 2. By simply using a square-wave carrier signal represented by only binary values, a signal superimposed on a band where the quantization noise in the vicinity of the frequency fs / 2 is small can be easily shifted in frequency, and “+1, +1, By using only a square wave carrier signal represented by only binary values that are repetitions of −1 and −1 ″, a signal superimposed on a band in which quantization noise near the frequency fs / 4 is small is used. Simply an effect that can be frequency-shifted.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing an electrical configuration of an embodiment of a delta-sigma modulation apparatus according to the present invention, FIG. 2 is a block diagram showing a configuration example of a delay device shown in FIG. 1, and FIG. FIG. 4 is a graph showing frequency characteristics of quantization noise distribution in the embodiment of the delta-sigma modulation apparatus according to the present invention, FIG. 4 is a block diagram modeling a delta-sigma modulation circuit, and FIG. FIG. 6 is an explanatory diagram for explaining the frequency characteristics of the quantization noise distribution of the quantized signal output from the delta sigma modulation circuit shown in FIG. 6, and FIG. 6 shows a second-order delta using a delay device that is delayed by two sampling periods. FIG. 7 is a block diagram modeling the sigma modulator, and FIG. 7 is a graph showing the frequency characteristics of the quantization noise distribution of the quantized signal output from the second-order delta sigma modulator shown in FIG.

  Referring to FIG. 1, the delta-sigma modulation apparatus 1 according to the present embodiment has N types (N is an integer) of analog signals or digital signals represented by multiple bits input as input signals X to the input terminal P1. An n-th order (n: integer greater than or equal to 1) delta-sigma modulation circuit that converts a quantized signal into a signal represented by a representative value of the signal and outputs the converted quantized signal as an output signal Y from an output terminal P2. .., Fan connected in cascade with each other, and multipliers Aa1 to Aan interposed in front of each of the integration elements Fa1 to Fan, respectively. Each of the integration elements Fa1 to Fan delays the output by m sampling periods (Ts: 1 / sampling frequency fs) (m: an integer equal to or greater than 2), and outputs from the delay devices Da1 to Dan are input. Are added to the input signal from the previous stage, and the previous output signal is added to the input signal from the previous stage for the m sampling period, and the output signal to the next stage is added. Is created.

  An analog signal or a multi-bit digital signal input as the input signal X to the input terminal P1 is input to the first-stage integration element Fa1 via the adder Cb and the first-stage multiplier Aa1. The outputs of the integration elements Fa1 to Fa (n−1) are respectively input to the integration elements Fa2 to Fan of the next stage via the multipliers Aa2 to Aan, and the outputs from the integration elements Fa1 to Fan are added to the adder Cc. Are added to each other and input to the quantizer 10. The quantizer 10 has a function of converting an input signal into a quantized signal into a signal represented by different representative values of N types (N is an integer). In this embodiment, the quantizer 10 The signal is converted into a signal (1-bit signal) represented by two types (+1 and −1) of representative values. Specifically, the output from the adder Cc is compared with a predetermined value, for example, 0 level for each sampling frequency fs, and when the output from the adder Cc is a predetermined value, for example, 0 level or more, the output terminal P2 The output signal Y to “1” is “1”, and is “−1” when it is less than a predetermined value. Further, the output signal Y from the quantizer 10 is negatively fed to the adder Cb interposed in the preceding stage of the first-stage multiplier Aa1 through the delayer Db and the multiplier Ab delayed by m sampling periods. It has been returned.

  As the delay elements Da1 to Dan of the integration elements Fa1,..., Fan and the delay element Db of the negative feedback loop, for example, as shown in FIG. 2, m delay elements D that delay the output by one sampling period are cascaded. A connected one can be used.

  FIG. 16 shows a conventional delta-sigma modulation circuit using a delay device D that delays the output by one sampling period instead of the delay devices Da1 to Dan of the integration elements Fa1,..., Fan and the delay device Db of the negative feedback loop. As shown, the noise shaping effect peculiar to the delta sigma modulation circuit that shifts the quantization noise to the high frequency band side is provided, but the delta sigma modulation device 1 of the present embodiment is shown in FIGS. As shown in c), a plurality of bands where the quantization noise is reduced on the frequency distribution are formed. FIG. 3 (a) shows the frequency characteristics of the quantization noise distribution when two delay devices D are connected in cascade and delay devices Da1 to Dan and delay device Db that are delayed by two sampling periods are used. A band in which new quantization noise is reduced is formed in the vicinity of the frequency fs / 2, and two bands in which the quantization noise is reduced are formed at a position folded at the frequency fs / 4. FIG. 3B shows the frequency characteristics of the quantization noise distribution in the case of using the delay units Da1 to Dan and the delay unit Db that are delayed by 3 sampling periods in which three delay units D are connected in cascade. A band in which new quantization noise is reduced is formed in the vicinity of the frequency fs / 3, and a band in which two quantization noises are reduced is formed at a position folded at the frequency fs / 6. FIG. 3C shows the frequency characteristics of the quantization noise distribution in the case of using delay units Da1 to Dan and a delay unit Db that are delayed by 4 sampling periods in which four delay units D are connected in cascade. In the vicinity of the frequency fs / 4 and in the vicinity of the frequency fs / 2, a band in which a new quantization noise is reduced is formed, and three quantizations are provided at the positions where the frequency fs / 8 and the frequency fs / 4 are folded. A band where noise is reduced is formed. In this way, m = 2n delay devices D are connected in cascade, delay devices Da1 to Dan and delay devices Db that are delayed by 2n sampling cycles, or m = 2n + 1 delay devices D are connected in cascade, 2n + 1 sampling cycles By using the delay devices Da1 to Dan and the delay device Dbm = 2n + 1 sample delay devices that are delayed by a certain amount, the band where the quantization noise is small on the frequency distribution is the folding position sandwiching the band where the quantization noise is large, That is, n + 1 locations are formed in the frequency band of fs * k / N (N is a natural number and k is an integer in the range of 0 ≦ k <(N + 1) / 2).

  Next, the frequency characteristic of the quantization noise distribution in the delta sigma modulation apparatus 1 of the present embodiment is verified using the block diagram shown in FIG. 4 that models the delta sigma modulation circuit. In FIG. 4, G corresponds to the integration elements Fa1,..., Fan, H corresponds to the delay device Db, and the quantizer 10 is added with a uniform noise N in each band.

  In the model shown in FIG. 4, the transfer function Q of the noise N can be expressed by Q = G / (1 + GH), and the transfer function P of the input signal x can be expressed by P = 1 / (1 + GH), where P = 1. In this case, G = 1 / Q and H = 1-Q.

Here, in the first-order delta-sigma modulation circuit, the frequency characteristic of the quantization noise distribution shifted to the high frequency band side as shown in FIG. 5A can be expressed by Q = (1-Z ⁻¹ ). , G = 1 / (1-Z ⁻¹ ), H = Z ⁻¹ , and instead of the delay elements Da1 to Dan of the integration elements Fa1,... This corresponds to a conventional delta-sigma modulation circuit using a delay device D that is delayed by a delay time.

On the other hand, in the first-order delta-sigma modulation circuit, a quantization noise distribution in which a band in which the quantization noise is small is formed in a low frequency band and a band near the frequency fs / 2 as shown in FIG. Can be expressed by Q = (1-Z ⁻¹ ) (1 + Z ⁻¹ ), G = 1 / (1-Z ⁻² ), H = Z ⁻² , and two delay devices D Corresponds to the first-order delta-sigma modulation apparatus 1 of the present embodiment using delay units Da1 to Dan and a delay unit Db that are delayed by two sampling periods.

Further, in the second-order delta-sigma modulation circuit, the frequency of the quantization noise distribution in which a band in which the quantization noise is small is formed between the low frequency band and the band near the frequency fs / 2 as shown in FIG. The characteristic can be represented by Q = (1-Z- ¹ ) ² (1 + Z- ¹ ) ² , G = 1 / (1-Z- ² ) ² , H = 1- (1-Z- ² ) ^2. This corresponds to the second-order delta-sigma modulation apparatus 1 in the present embodiment using the delay devices Da1 to Dan and the delay device Db that are delayed by two sampling periods, in which two delay devices D are connected in cascade.

  The second-order delta-sigma modulation apparatus 1 can be modeled as shown in FIG. 6, and the frequency characteristic of the quantization noise distribution simulated using the model shown in FIG. 6 and the sampling frequency fs = 2.8 MHz is As shown in FIG. 7, it was demonstrated that a band in which the quantization noise is small is formed in the low frequency (0) band and the band in the vicinity of the frequency fs / 2 = 1.4 MHz.

Next, the seventh-order delta-sigma modulation apparatus 2 in the present embodiment will be described in detail with reference to FIGS.
FIG. 8 is a block diagram showing the configuration of the 7th-order delta-sigma modulation apparatus in this embodiment, and FIG. 9 shows the quantization of the quantized signal output from the 7th-order delta-sigma modulation apparatus shown in FIG. It is a graph which shows the frequency characteristic of noise distribution.

  Referring to FIG. 8, the delta sigma modulation apparatus 2 includes seven integration elements Fa1,..., Fa7 connected in cascade with each other, and multipliers Aa1 to Aa7 interposed in front of the integration elements Fa1 to Fa7, respectively. have. Each of the integration elements Fa1 to Fa7 adds a delay device that delays the output by m sampling periods (Ts: 1 / sample frequency fs) (m: an integer equal to or greater than 2), and adds the output from the delay device to the input for output. Therefore, the previous output signal is added to the input signal from the preceding stage by the m sampling period, and the output signal to the next stage is created.

  An analog signal or a multi-bit digital signal input as the input signal X to the input terminal P1 is input to the first stage integration element Fa1 via the adder Cb and the first stage multiplier Aa1. Input to the integration element Fa1 of the stage, and outputs of the integration elements Fa1 to Fa6 are respectively input to the integration elements Fa2 to Fa7 of the next stage via the multipliers Aa2 to Aa7, and are output from the integration elements Fa1 to Fa7. Are added to each other by the adder Cc and then input to the quantizer 10. The quantizer 10 compares the output from the adder Cc with a predetermined value, for example, 0 level for each sampling frequency fs, and outputs an output terminal when the output from the adder Cc is a predetermined value, for example, 0 level or more. The output signal Y to P2 is “1”, and is “−1” when it is less than a predetermined value. Further, the output signal Y from the quantizer 10 is negatively fed to the adder Cb interposed in the preceding stage of the first-stage multiplier Aa1 through the delayer Db and the multiplier Ab delayed by m sampling periods. It has been returned.

  Further, adders Cd1 to Cd3 are interposed in front of the integration elements Fa2, Fa4, and Fa6, respectively, and delay elements Dc1 to Dc3 in which outputs of the integration elements Fa3, Fa5, and Fa7 are delayed by m sampling periods and multiplications. Three partial negative feedback loops are respectively fed back to the adders Cd1 to Cd3 interposed in the preceding stage of the first-stage multiplier Aa1 through the units Ac1 to Ac3, respectively.

  FIG. 9 shows the quantization noise of the delta-sigma modulation apparatus 2 using four delay devices D connected in cascade and using delay devices Da1 to Dan, a delay device Db, and delay devices Dc1, Dc2, and Dc3 that are delayed by four sampling periods. The frequency characteristics of the distribution are shown, and a band in which new quantization noise is reduced is formed in the vicinity of the frequency fs / 4 and in the vicinity of the frequency fs / 2, and each band is turned back at the frequency fs / 8 and the frequency fs / 4. A band where the quantization noise is reduced at three positions is formed at three positions, and three rising and falling edges of the quantization noise distribution in each band where the quantization noise is reduced by three partial negative feedback loops. Each dip is formed. The shape of the dip can be changed by appropriately selecting the multiplication coefficients of the multipliers Aa1 to Aa7, the multipliers Ab and Ac1 to Ac3, and the width of each band where the quantization noise that becomes the effective frequency band is reduced. The dynamic range within the band can be set as appropriate.

Next, a signal multiplexing apparatus that multiplexes signals using the delta-sigma modulation apparatus 1 of the present embodiment will be described in detail with reference to FIGS.
FIG. 10 is a block diagram showing a configuration of a signal multiplexing apparatus that multiplexes signals using the embodiment of the delta-sigma modulation apparatus according to the present invention, and FIG. 11 is a block diagram of the multiplexing modulation apparatus shown in FIG. FIG. 12 is an explanatory diagram for explaining the multiplexed modulation operation, FIG. 12 is an explanatory diagram for explaining the demultiplexing and demodulating operation in the demultiplexing apparatus shown in FIG. 10, and FIGS. 13 and 14 are shown in FIG. It is a block diagram which shows the structure of other embodiment of a multiplexing modulation apparatus.

Referring to FIG. 10, a signal multiplexing apparatus 3 that multiplexes signals using the delta-sigma modulation apparatus 1 of the present embodiment has four input signals X _{1 to} X ₄ respectively input to input terminals P 11 to P 14. Is multiplexed and modulated into a quantized signal, and a multiplexed modulation device 4 that outputs the modulated quantized signal and a quantized signal in which the four input signals X _{1 to} X ₄ are multiplexed are separated and demodulated, and an output terminal An output signal Y ₁ corresponding to the input signal X ₁ is output from P 21, an output signal Y ₂ corresponding to the input signal X ₂ is output from the output terminal P 22, and an output signal Y ₃ corresponding to the input signal X ₃ is output from the output terminal P 23. becomes an output signal Y ₄ corresponding from the terminal P24 to the input signal X ₄ from separating demodulator 5 for outputting each line something with the output quantized signal from the multiplexing modulator 4 by the processing unit 6 It makes is configured to four input signals X ₁ to X ₄ which are multiplexed can be performed collectively processed.

Multiplexing modulator 4 modulates a delta-sigma modulator 1a for modulating an input signal X ₁ that is input to the input terminal P11 to the quantized signal, the input signal X ₂ which is input to the input terminal P12 to the quantized signal a delta-sigma modulator 1b, modulates the input signal X ₃ input to the input terminal P13 and the delta-sigma modulator 1c for modulating the quantized signal, an input signal X ₄ inputted to the input terminal P14 to the quantized signal The delta-sigma modulation device 1d, the multiplier Ad2 that phase-frequency modulates the output from the delta-sigma modulation device 1b using the carrier signal, and the phase-frequency modulation of the output from the delta-sigma modulation device 1c using the carrier signal A multiplier Ad3, a multiplier Ad4 for frequency-modulating the output from the delta-sigma modulation apparatus 1d using the carrier signal, and the delta-sigma modulation apparatus 1 The output from a, the output from the delta-sigma modulation device 1b phase-frequency modulated by the multiplier Ad2, the output from the delta-sigma modulation device 1c phase-frequency modulated by the multiplier Ad3, and the frequency modulated by the multiplier Ad4 The adder Ce for adding the outputs from the delta sigma modulator 1d and the delta sigma modulator 1e for modulating the multi-bit signal output from the adder Ce into a quantized signal.

The delta-sigma modulators 1a to 1d use delay units Da1 to Dan and a delay unit Db, which are delayed by four sampling periods, in which four delay units D are connected in cascade, and an output quantized signal is shown in FIG. 3 (c), which has frequency characteristics of a quantization noise distribution in which bands near the frequency 0, near the frequency fs / 4, and around the frequency fs / 2 are formed with a band in which the quantization noise is small. As shown in FIG. 11, the input signals X _{1 to} X ₄ are superimposed on a band near the frequency 0. The input signals X _{1 to} X ₄ are band-limited within (fs / 2) / 3 by a band-limiting low-pass filter (not shown) provided in the previous stage of the delta-sigma modulators 1a to 1d.

The multiplier Ad2 uses the carrier signal having the frequency fs / 4 modulated by the sin signal, so that the input signal X superimposed on the quantized signal output from the delta-sigma modulation device 1b as shown in FIG. ₂ is phase-modulated and frequency-shifted to the frequency fs / 4.

The multiplier Ad3 uses the carrier signal with the frequency fs / 4 modulated by the cos signal, and as shown in FIG. 11, the input signal X superimposed on the quantized signal output from the delta-sigma modulation device 1c. _3, causes the phase modulated component orthogonal to the input signal X _2, which is phase-modulated based on the sin signal, is frequency shifted to a frequency fs / 4.

Multiplier Ad4, by using the carrier signal of a frequency fs / 2, as shown in FIG. 11, the input signal X ₄ superimposed on the quantized signal outputted from the delta sigma modulator 1d, the frequency fs / Frequency shift to 2.

Adder Ce is the output from the delta-sigma modulator 1a, the input signal X ₁ is superimposed on the band in which quantization noise around frequency 0 is small, the input signal X ₂ is a frequency that is phase-modulated based on sin signal the output from the multiplier Ad2 to fs / 4 near the quantization noise is superimposed on a small becomes bands, the input signal X ₃ phase-modulated becomes a frequency fs / 4 near the quantization noise small based on the cos signal the output from the multiplier Ad3 superimposed on the band, the input signal X ₄ is a frequency fs / 2 near the quantization noise is added to the output from the multiplier Ad4 superimposed on the small becomes bands.

The delta sigma modulation device 1e uses delay units Da1 to Dan and a delay unit Db that are connected by four delay units D and are delayed by four sampling periods. The multi-bit output from the adder Ce by performing delta-sigma modulation, as shown in FIG. 11, the band quantization noise is small near zero input signal X ₁ frequency, and the input signal X _2, which is phase-modulated based on sin signal, cos signal based on the phase-modulated, orthogonalized input signal X ₃ and the frequency fs / 4 near the quantization noise to the input signal X ₂ is the small becomes band, the input signal X ₄ is in the vicinity of the frequency fs / 2 A quantized signal superimposed on each band where the quantization noise is small is output.

Thus, the output of the delta-sigma modulator. 1e, four input signals X ₁ to X ₄ is a quantized signal that is a digital signal multiplexed, hardly affected by the transmission line, an advantage that a strong error have. Further, by performing the processing (amplification, etc.) to the quantized signal by the processing unit 6, it makes it possible to collectively process the four input signals X ₁ to X ₄ which are multiplexed.

  The demodulator 5 is a multiplier Ae2 and a multiplier Ae3 that phase / frequency modulate the output of the delta sigma modulator 1e using the carrier signal, and a multiplier that frequency modulates the output of the delta sigma modulator 1e using the carrier signal. And a low-pass filter (LBP) 51a to 51d that passes only a low-frequency band near the frequency 0 as a baseband as an analog signal.

Multiplier Ae2, by using the carrier signal of a frequency fs / 4 which is modulated by the sin signal, an input signal X ₁ to X ₄ which are superimposed on the quantized signal outputted from the delta sigma modulator 1e, a phase Modulate and frequency shift. Thus, the output from the multiplier Ae2, as shown in FIG. 12, the band input signals X ₂ becomes the quantization noise around frequency 0 is small, the input signal X ₄ input signals X ₁ and the frequency fs / band quantization noise is small in the vicinity of 4, the input signal X ₂ frequency fs / 2 near the quantization noise is respectively superimposed quantized signal into small becomes bands.

Multiplier Ae3, by using the carrier signal of a frequency fs / 4 modulated by cos signal, an input signal X ₁ to X ₄ which are superimposed on the quantized signal outputted from the delta sigma modulator 1e, a phase Modulate and frequency shift. Thus, the output from the multiplier Ae3, as shown in FIG. 12, the band input signals X ₃ becomes the quantization noise around frequency 0 is small, the input signal X ₄ input signals X ₁ and the frequency fs / band quantization noise is small in the vicinity of 4, the input signal X ₃ frequency fs / 2 near the quantization noise is respectively superimposed quantized signal into small becomes bands.

Multiplier Ae4, by using the carrier signal of a frequency fs / 2, the input signal X ₁ to X ₄ which are superimposed on the quantized signal outputted from the delta sigma modulator 1e, is frequency shifted. Thus, the output from the multiplier Ae4, as shown in FIG. 12, the band quantization noise is small near zero input signal X ₄ frequency, the input signal X ₂ and the input signal X ₃ and the frequency fs / band quantization noise is small in the vicinity of 4, the input signal X ₁ frequency fs / 2 near the quantization noise is respectively superimposed quantized signal into small becomes bands.

The low-pass filter (LBP) 51a passes only the band near the frequency 0 in the output of the delta sigma modulation device 1e as an analog signal, so that the input signal X _{1 is} output from the output of the delta sigma modulation device 1e as shown in FIG. extracting only as an analog signal, outputted from the output terminal P21 as an output signal Y _1.

A low-pass filter (LBP) 51b are only band around zero frequency at the output of the multiplier Ae2 by passing an analog signal, as shown in FIG. 12, the analog signal only input signals X ₂ from the output of the multiplier Ae2 extraction as outputs from the output terminal P22 as an output signal _{Y 2.}

A low-pass filter (LBP) 51c are only band around zero frequency at the output of the multiplier Ae3 by passing an analog signal, as shown in FIG. 12, the analog signal only the input signal X ₃ from the output of the multiplier Ae3 extraction as outputs from the output terminal P23 as an output signal _{Y 3.}

A low-pass filter (LBP) 51d is only band around zero frequency at the output of the multiplier Ae4 by passing an analog signal, as shown in FIG. 12, the analog signal only the input signal X ₄ from the output of the multiplier Ae4 extraction as outputs from the output terminal P23 as an output signal _{Y 4.}

As described above, 4 is multiplexed into the quantized signal output from the multiplex modulation device 4 by the separation and demodulation device 5 having a simple configuration including the multipliers Ae2 to Ae4 and the low pass filters (LBP) 51a to 51d. The two input signals X _{1 to} X ₄ can be easily separated.

For multiplexing the input signals X _{1 to} X ₄ , as shown in FIG. 14, a multiplexing modulation device 41 in which the delta sigma modulation devices 1 a to 1 d are omitted from the configuration of the multiplexing modulation device 4 may be used. . That is, multiplexing modulator 41, the input signal X ₂ that is input to the input terminal P12 by using the carrier signal multiplier Ad2 for phase and frequency modulation, the input signal inputted to the input terminal P13 using a carrier signal a multiplier Ad3 the X ₃ phase and frequency modulation, the input signal _{X 4} is input to the input terminal P14 by using the carrier signal multiplier Ad3 frequency modulating an input signal _X 1 that is input to the input terminal P11, an adder Ce for adding an input signal X ₄ which are frequency-modulated by the phase and frequency modulated input signal X ₃ and multiplier Ad4 by phase and frequency modulated input signals X _2, multiplier Ad3 by a multiplier Ad2, The delta-sigma modulation device 1e that modulates the multi-bit signal output from the adder Ce into a quantized signal, as shown in FIG. No. The X ₁ to X ₄ is added in a state that does not modulate the quantized signal, and is configured to modulate the multiplexed quantized signal by delta-sigma modulator 1e.

Also, the multiplexing of the input signals _X 1 to X _4, as shown in FIG. 15, in place of the delta-sigma modulator 1a~1d in the configuration of the multiplexing modulator 4, an input signal _X 1 to X ₄ each The conventional delta-sigma modulation circuits 20a to 20d that modulate to quantized signals and the frequency characteristics of the quantization noise distribution in the quantized signals output from the delta-sigma modulation circuits 20a to 20d are output from the delta-sigma modulation devices 1a to 1d. Alternatively, a multiplex modulation device 42 including filters 51a to 51d processed so as to have the same frequency characteristics as the quantization noise distribution in the quantized signal to be generated may be used.

Further, in the present embodiment, delay devices Da1 to Dan and delay device Db, which are connected by four delay devices D in cascade and are delayed by four sampling periods, are used, and the vicinity of frequency 0, the vicinity of frequency fs / 4, The four input signals X _{1 to} X ₄ are multiplexed by the delta-sigma modulators _{1 a to 1} e having the frequency characteristics of the quantization noise distribution in which the bands where the quantization noise is small are formed at three locations near the frequency fs / 2. However, it is possible to arbitrarily set the number of bands in which the quantization noise in the frequency characteristic of the quantization noise distribution is small by changing the number of cascade connections of the delay devices D. The number of input signals to be multiplexed by being superimposed on a band with a small can be set arbitrarily.

Furthermore, in the present embodiment, the _two signals of the input signals X ₂ and X ₃ that are orthogonalized in a band where the quantization noise near the frequency fs / 4 is reduced are superimposed, but the frequency fs / 4 is used. band quantization noise is small in the vicinity, without performing the phase modulation, may be to superimpose only the input signal X _2.

  As described above, according to the present embodiment, the delay devices Da1 to Dan that delay the output by a plurality of sampling periods and the adders Ca1 to Can that add the outputs from the delay devices Da1 to Dan to the input are provided. A plurality of integration elements Fa1 to Fan are connected in cascade, and the output from the adder Cc that adds the outputs from the integration elements Fa1 to Fan is quantized by the quantizer 10 based on the sampling frequency fs and modulated into a quantized signal. The output from the quantizer 10 is negatively fed back to the first-stage integral element Fa1 via the delay device Db that delays the input by the same number of sampling periods as the delay devices Da1 to Dan. Quantization noise capable of superimposing a plurality of signals in the frequency characteristics of the quantization noise of the quantized signal output from 10 Since multiple bands can be formed in separate frequency bands, different signals can be superimposed on multiple bands where quantization noise is small, and multiple signals are multiplexed. The effect is that it can be created. Further, the band where the quantization noise formed by the delta-sigma modulation apparatus of the present invention is small is the folding position sandwiching the band where the quantization noise is large, that is, fs * k / N (N is a natural number, k is Therefore, it is possible to superimpose a plurality of signals having the same amount of data, respectively, since the frequency band is an integer in the range of 0 ≦ k <(N + 1) / 2. Further, when the dip is created by increasing the integral elements for partial negative feedback, it is necessary to redesign the coefficient for stabilization. In the delta-sigma modulation device of the present invention, the delay units Da1 to Dan, Db Therefore, the coefficient designed by the conventional method can be used as it is, and the design is easy.

  Furthermore, according to the present embodiment, the delay units Da1 to Dan, Db that delay the input by a plurality of sampling periods are configured so that a plurality of delay elements that are delayed by one sampling period are connected in cascade. By simply overlapping a plurality of delay devices that are delayed by one sampling period, the number of bands in which the formed quantization noise is reduced can be set as appropriate, and the design is easy.

  Furthermore, according to the present embodiment, the delay devices Da1 to Dan, Db that are delayed by two sampling periods are used, and the frequency characteristic of the quantization noise of the quantized signal output from the quantizer 10 is a band near frequency 0. And a band in the vicinity of the frequency fs / 2 so as to form a band in which the quantization noise is small, so that a square-wave carrier signal represented by only binary values that are repetitions of “+1, −1”. By simply using, it is possible to easily shift the frequency of a signal superimposed in a band where the quantization noise near the frequency fs / 2 is small.

  Furthermore, according to the present embodiment, the delay units Da1 to Dan and Db that are delayed by four sampling periods are used, and the frequency characteristic of the quantization noise of the quantized signal output from the quantizer 10 is a band near frequency 0. And a band near the frequency fs / 4 and a band near the frequency fs / 2 are formed so as to form a band where the quantization noise is small. By simply using a square wave carrier signal, a signal superimposed on a band where the quantization noise in the vicinity of the frequency fs / 2 is small can be easily shifted in frequency, and "+1, +1, -1, -1" The signal superimposed on the band where the quantization noise near the frequency fs / 4 is small is simply frequency-shifted only by using a square-wave carrier signal represented by only binary values that are repetitions of " An effect that theft can be.

  Note that the present invention is not limited to the above-described embodiments, and it is obvious that the embodiments can be appropriately changed within the scope of the technical idea of the present invention. In addition, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a suitable number, position, shape, and the like in practicing the present invention. In each figure, the same numerals are given to the same component.

It is a block diagram which shows the electric constitution of embodiment of the delta-sigma modulation apparatus which concerns on this invention. It is a block diagram which shows the structural example of the delay device shown in FIG. It is a graph which shows the frequency characteristic of quantization noise distribution in embodiment of the delta-sigma modulation apparatus which concerns on this invention. It is the block diagram which modeled the delta-sigma modulation circuit. FIG. 5 is an explanatory diagram for explaining frequency characteristics of a quantization noise distribution of a quantized signal output from the delta sigma modulation circuit shown in FIG. 4. It is the block diagram which modeled the 2nd-order delta-sigma modulation apparatus using the delay device delayed only 2 sampling periods. It is a graph which shows the frequency characteristic of the quantization noise distribution of the quantization signal output from the secondary delta-sigma modulation apparatus shown in FIG. It is a block diagram which shows the structure of the 7th-order delta-sigma modulation apparatus in this Embodiment. It is a graph which shows the frequency characteristic of the quantization noise distribution of the quantization signal output from the 7th-order delta-sigma modulation apparatus shown in FIG. It is a block diagram which shows the structure of the signal multiplexing apparatus which multiplexes a signal using Embodiment of the delta-sigma modulation apparatus which concerns on this invention. It is explanatory drawing for demonstrating the multiplexing modulation operation | movement in the multiplexing modulation apparatus shown in FIG. It is explanatory drawing for demonstrating the separation-demodulation operation | movement in the separation-demodulation apparatus shown in FIG. It is a block diagram which shows the structure of other embodiment of the multiplexing modulation apparatus shown in FIG. It is a block diagram which shows the structure of other embodiment of the multiplexing modulation apparatus shown in FIG. It is a block diagram which shows the structure of the conventional delta-sigma modulation circuit. It is a graph which shows the frequency characteristic of the quantization noise distribution of the quantization signal output from the conventional delta-sigma modulation circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a-1e, 2 Delta-sigma modulator 3 Signal multiplexer 4, 41, 42 Multiplex modulator 43a-43d Filter 5 Separation demodulator 51a-51d Low-pass filter (LBP)
6 Processing Device 10 Quantizer P1-P4 Input Terminal X Input Signal Y Output Signal Aa1-Aan, Ab, Ac1-Ac3, Ad2-Ad4, Ae2-Ae4 Multipliers Ca1-Can, Cb, Cc, Cd1-Cd3, Ce adder D1~D4, Da1~Dan, Db, Dc1~Dc3 delayer F1~Fn, Fa1~Fan integral element P11~P14 input P21~P24 output terminal X ₁ to X ₄ input signals Y ₁ to Y ₄ output signal 20, 20a-20d Conventional delta-sigma modulation circuit

Claims (3)

Vertical and continue a plurality of connected integrating means, and adding means for adding outputs from each integrating means, quantizing means for outputting a quantized signal by quantizing the basis the output from the adding means to the sampling frequency A negative feedback loop that negatively feeds back the output from the quantizing means to the integrating means in the first stage, and a delta-sigma modulation device that modulates an input signal input to the integrating means in the first stage into the quantized signal. There,
A plurality of delay units that delay one sampling period are connected in cascade , and a plurality of the integration units are configured to delay the output by a sampling period corresponding to the number of the delay units ;
Adding means for adding the output from the first delay means to the input respectively ;
In the negative feedback loop, the same number of the delay devices as the first delay means are connected in cascade, and the quantization is performed via the second delay means for delaying the input by the same number of sampling periods as the first delay means. The output from the means is negatively fed back to the integrating means in the first stage , and quantization noise is present between the frequency 0 and the frequency fs / 2 in the frequency characteristic of the quantization noise of the quantized signal output from the quantization means. delta-sigma modulator according to claim Rukoto is more formed sandwiched folding located between the band of small consisting band quantization noise becomes large.   The first delay means and the second delay means are delay means for delaying only two sampling periods by cascading two delay devices for delaying by one sampling period,
  In the frequency characteristic of the quantization noise of the quantization signal output from the quantization means, a band where the quantization noise is small is formed in a band near the frequency 0 and a band near the frequency fs / 2. The delta-sigma modulation device according to claim 1.   The first delay means and the second delay means are delay means for delaying only four sampling periods by cascading four delay devices that delay one sampling period,
  In the frequency characteristic of the quantization noise of the quantized signal output from the quantization means, a band in which the quantization noise is reduced to a band near frequency 0, a band near frequency fs / 4, and a band near frequency fs / 2. The delta-sigma modulation device according to claim 1, wherein:

Images