Integral-Differential Modulation Device and Integral-Differential Modulation Method

Abstract

An integration-differentiation modulation device includes a detection circuit and an integration-differentiation modulator. The detection circuit is used to detect an input signal to generate a detection signal, and compare the detection signal with a threshold value to generate a control signal. The integration-differentiation modulator is coupled to the detection circuit. The integration-differentiation modulator is used to store a plurality of noise transfer functions, select one of the noise transfer functions according to the control signal, and convert the input signal into an output signal according to the selected noise transfer function.

Description

Technical Field

[0001] The present invention application relates to a digital-to-analog converter (DAC) or an analog-to-digital converter (ADC), and particularly to a sigma-delta modulation device and a sigma-delta modulation method. Background Art

[0002] Sigma-delta modulators are commonly used in digital-to-analog converters (DACs) and analog-to-digital converters (ADCs). The stability of a sigma-delta modulator is limited by the magnitude of the input signal (e.g., the magnitude of the signal amplitude), and an overly large input signal will cause instability.

[0003] Therefore, how to design a sigma-delta modulator that simultaneously has a sufficiently large input upper limit and a good dynamic range is an important topic in this field. Summary of the Invention

[0004] One technical solution of the present invention application is about a sigma-delta modulation device, which includes a detection circuit and a sigma-delta modulator. The detection circuit is used to detect an input signal to generate a detection signal, and compare the detection signal with a threshold value to generate a control signal. The sigma-delta modulator is coupled to the detection circuit. The sigma-delta modulator is used to store a plurality of noise transfer functions, select one function from the noise transfer functions according to the control signal, and convert the input signal into an output signal according to the selected noise transfer function.

[0005] Another technical solution of the present invention application is about a sigma-delta modulation method, which is applicable to a sigma-delta modulation device. The sigma-delta modulation device includes a sigma-delta modulator. The sigma-delta modulator is used to store a plurality of noise transfer functions. The sigma-delta modulation method includes: detecting an input signal of the sigma-delta modulator to generate a detection signal; comparing the detection signal with a threshold value to generate a control signal; selecting one function from the noise transfer functions according to the control signal; and converting the input signal into an output signal according to the selected noise transfer function.

[0006] In summary, by detecting the change in the magnitude of specific parameters of the input signal to generate corresponding control signals to dynamically switch different noise transfer functions, the sigma-delta modulator can maintain a good dynamic range and stability. Brief Description of the Drawings

[0007] Figure 1Schematic diagram of the total harmonic distortion plus noise of the integrator-differentiator modulator versus the amplitude of the input signal.

[0008] Figure 2 Schematic diagram of an integrator-differentiator modulation device according to an embodiment of the present invention application.

[0009] Figure 3 Schematic diagram of the total harmonic distortion plus noise of multiple noise transfer functions according to an embodiment of the present invention application versus the amplitude of the input signal.

[0010] Figure 4 Flowchart of an interface connection method according to an embodiment of the present invention application.

[0011] Symbol description:

[0012] 100: Integrator-differentiator modulation device

[0013] 120: Detection circuit

[0014] 121: Envelope detector

[0015] 122: Comparison circuit

[0016] 140: Integrator-differentiator modulator

[0017] Din: Input signal

[0018] Dout: Output signal

[0019] DS: Detection signal

[0020] TH: Amplitude threshold

[0021] CS: Control signal

[0022] Fa, Fb: Noise transfer function

[0023] T0, Ta, Tb: Total harmonic distortion plus noise

[0024] lim0, lim1, lim2: Input upper limit

[0025] 400: Integrator-differentiator modulation method

[0026] S410~S440: Operations Detailed implementation

[0027] The following is a detailed description of the embodiments in conjunction with the accompanying drawings. However, the specific embodiments described are only used to explain the present invention and do not limit the present invention application. The description of the structure and operation is not used to limit the execution order. Any structure recombined by components that produces a device with equivalent functions belongs to the scope covered by the present invention application.

[0028] Reference Figure 1 。 Figure 1 It is a schematic diagram of the relationship between the total harmonic distortion plus noise (THD+N) of an integrator-differentiator modulator and the amplitude of the input signal. As Figure 1 shown, when the amplitude of the input signal (in decibels (dB)) does not exceed the value lim0, the total harmonic distortion plus noise (in decibels (dB)) is approximately T0, and its change is relatively stable. When the amplitude of the input signal exceeds the value lim0, the total harmonic distortion plus noise will increase sharply. That is to say, when the amplitude of the input signal received by the integrator-differentiator modulator is greater than the value lim0, the proportion of harmonic and noise components in the output signal generated by the integrator-differentiator modulator will increase significantly. That is, when the amplitude of the input signal is greater than a specific value, the output signal will be greatly distorted relative to the input signal.

[0029] In other words, the upper limit value of the amplitude of the input signal that the integrator-differentiator modulator can stably process and generate a relatively accurate output signal is called the input upper limit (i.e., the value lim0). As Figure 1 shown, when the amplitude of the input signal exceeds the input upper limit lim0, the total harmonic distortion plus noise of its output signal will increase significantly. That is to say, when the input signal exceeds this input upper limit lim0, the substantial content of the output signal will be masked by distortion and noise. Generally speaking, the higher the input upper limit that an ideal integrator-differentiator modulator can achieve, the better.

[0030] On the other hand, when no input signal is input (the amplitude of the input signal is zero), the intensity of the total harmonic distortion plus noise output at this time is also called the background noise. As Figure 1 shown in the example, the signal intensity of the background noise of this integrator-differentiator modulator is T0. Generally speaking, the intensity difference between the maximum effective output of the integrator-differentiator modulator (for example, the maximum signal output intensity without obvious distortion, not shown in the figure) and the background noise (such as the signal intensity T0) is called the dynamic range. Simply put, the dynamic range can also be understood as the signal intensity difference between the minimum output intensity and the maximum output intensity of the integrator-differentiator modulator. Generally speaking, the larger the dynamic range that an ideal integrator-differentiator modulator can achieve, the better.

[0031] Please refer to Figure 2 。 Figure 2 It is a schematic diagram of an integrator-differentiator modulation device 100 according to an embodiment of the content of the present invention application. The integrator-differentiator modulation device 100 can be used for digital-to-analog converters (DACs) and analog-to-digital converters (ADCs). As Figure 2As shown, the integrator-differentiator modulation device 100 includes a detection circuit 120 and an integrator-differentiator modulator 140. Structurally, the integrator-differentiator modulator 140 is coupled to the detection circuit 120.

[0032] In some embodiments, the detection circuit 120 includes an envelope detector 121 and a comparison circuit 122. Specifically, the envelope detector 121 is coupled to the comparison circuit 122. The comparison circuit 122 is coupled to the integrator-differentiator modulator 140. In practice, the comparison circuit 120 can be implemented by an operational amplifier or other circuits with the function of judging voltage magnitude. It should be noted that Figure 2 the detection circuit 120 shown is only an example for convenience of explanation and is not intended to limit the present invention. Those of ordinary skill in the art can adjust or add other components according to actual needs.

[0033] In operation, in one embodiment, the detection circuit 120 is used to detect the input signal Din to generate a detection signal DS, and compare the detection signal DS with an amplitude threshold TH to generate a control signal CS. The integrator-differentiator modulator 140 is used to store a plurality of noise transfer functions, select one of the plurality of noise transfer functions according to the control signal CS, and convert the input signal Din into an output signal Dout according to this noise transfer function. In the above embodiment, the detection circuit 120 compares the amplitude of the detection signal DS with the amplitude threshold TH to generate the control signal CS, but the present application is not limited thereto. In another embodiment, the detection circuit 120 can compare other signal parameters of the detection signal DS (such as the pulse duration length of the signal, the duty cycle of the signal, etc.) with the corresponding thresholds to generate the control signal CS. In subsequent embodiments, for the sake of simplicity in description, the comparison of the amplitude of the detection signal DS with the amplitude threshold TH is mainly used as an example.

[0034] Specifically, the envelope detector 121 in the detection circuit 120 is used to receive the input signal Din, detect the amplitude change of the input signal Din to generate the detection signal DS, and then output the detection signal DS to the comparison circuit 122. The comparison circuit 122 in the detection circuit 120 is used to receive the detection signal DS, compare the detection signal DS with the amplitude threshold TH to generate the control signal CS, and then output the control signal CS to the integrator-differentiator modulator 140.

[0035] Among them, the integrator-differentiator modulator 140 performs noise shaping on quantization noise through a noise transfer function, shifting the quantization noise towards the high-frequency band to reduce the impact caused by quantization noise in the integrator-differentiator modulator 140, thereby improving the quality of the output signal Dout.

[0036] Furthermore, the integrator-differentiator modulator 140 can store more than one noise transfer function with different functional mapping relationships. Please refer to Figure 3 . Figure 3 FIG. is a schematic diagram of the relationship between the total harmonic distortion plus noise of multiple noise transfer functions Fa and Fb according to an embodiment of the present invention application content with respect to the amplitude of the input signal. In some embodiments, the integrator-differentiator modulator 140 stores two different noise transfer functions Fa and Fb. However, these two noise transfer functions Fa and Fb are only exemplary for convenience of explanation and are not used to limit the present invention. That is, in other some embodiments, the integrator-differentiator modulator 140 can store more than two noise transfer functions with different functional mapping relationships.

[0037] As Figure 3 shown, the noise transfer function Fa has an input upper limit lim1. When the amplitude of the input signal is lower than lim1, the value of the total harmonic distortion plus noise of the noise transfer function Fa is relatively stably maintained near Ta (hereinafter referred to as the stable value of the total harmonic distortion plus noise of the noise transfer function Fa). On the other hand, the noise transfer function Fb has an input upper limit lim2. When the amplitude of the input signal is lower than lim2, the value of the total harmonic distortion plus noise of the noise transfer function Fb is relatively stably maintained near Tb (hereinafter referred to as the stable value of the total harmonic distortion plus noise of the noise transfer function Fb). Among them, the input upper limit lim1 of the noise transfer function Fa is less than the input upper limit lim2 of the noise transfer function Fb, and the stable value of the total harmonic distortion plus noise Ta of the noise transfer function Fa is less than the stable value of the total harmonic distortion plus noise Tb of the noise transfer function Fa. In other words, the noise transfer function Fa has better (lower value) total harmonic distortion plus noise, but its input upper limit lim1 is lower. Generally, when the intensity of the input signal and the output signal of the integrator-differentiator modulator 140 are positively correlated, when the intensity of the input signal of the integrator-differentiator modulator 140 is greater, the intensity of the corresponding output signal is also greater. Therefore, if the integrator-differentiator modulator 140 uses the noise transfer function Fa with a lower input upper limit lim1, the maximum value of the effective output signal of the integrator-differentiator modulator 140 will correspondingly decrease, resulting in a narrower dynamic range of the integrator-differentiator modulator 140.

[0038] On the other hand, the noise transfer function Fb has a poor (higher value) total harmonic distortion plus noise, but its input upper limit lim2 is higher. Therefore, when the noise transfer function Fb adopted by the integrator-differentiator modulator 140 has a higher input upper limit lim2, the maximum value of the effective output signal of the integrator-differentiator modulator 140 will correspondingly increase, making the dynamic range of the integrator-differentiator modulator 140 wider.

[0039] In this embodiment, the amplitude threshold TH can be set to be less than or equal to the input upper limit lim1 of the noise transfer function Fa, but the present invention application is not limited thereto. In this case, when the amplitude of the detection signal DS generated according to the input signal Din is not greater than the amplitude threshold TH, the comparison circuit 122 is used to generate a first control signal, so that the integrator-differentiator modulator 140 selects the noise transfer function Fa according to the first control signal to obtain a better (lower value) total harmonic distortion plus noise Ta. On the contrary, when the amplitude of the detection signal DS is greater than the amplitude threshold TH, the comparison circuit 122 is used to generate a second control signal, so that the integrator-differentiator modulator 140 selects the noise transfer function Fb according to the second control signal to increase the upper limit of the input signal amplitude allowable by the integrator-differentiator modulator 140 (that is, it is converted from the input upper limit lim1 corresponding to the noise transfer function Fa to the input upper limit lim2 corresponding to the noise transfer function Fb).

[0040] That is, when the amplitude of the detection signal DS is less than the input upper limit lim1, the integrator-differentiator modulator 140 selects the noise transfer function Fa with a relatively small stable value of total harmonic distortion plus noise (that is, Ta); when the amplitude of the detection signal DS is greater than the input upper limit lim1 (in this case, if the noise transfer function Fa continues to be used, it will cause significant distortion), the integrator-differentiator modulator 140 selects the noise transfer function Fb with a relatively large stable value of total harmonic distortion plus noise (that is, Tb) but still without distortion. In this way, since different noise transfer functions (such as Fa and Fb) have different input upper limits (such as lim1 and lim2) and total harmonic distortion plus noise (such as Ta and Tb), therefore, by switching different noise transfer functions, the integrator-differentiator modulator 140 can dynamically select a good dynamic range and maintain signal stability according to the amplitude change of the input signal Din.

[0041] Reference Figure 4 。 Figure 4 FIG. 400 is a flowchart of an integrator-differentiator modulation method according to an embodiment of the present invention application. Specifically, the integrator-differentiator modulation method 400 is applied to the integrator-differentiator modulation device 100. For the sake of convenience and clear description, the following integrator-differentiator modulation method 400 is coordinated with Figure 2 and Figure 3The following describes the illustrated embodiments, but is not limited thereto. Any person skilled in the art can make various modifications and adjustments without departing from the spirit and scope of the content of the present invention application. For example, Figure 4 As shown, the integral-differential modulation method 400 includes operations S410, S420, S430, and S440.

[0042] First, in operation S410, the input signal Din of the integral-differential modulator 140 is detected to generate a detection signal DS. Specifically, the envelope detector 121 detects the amplitude change of the input signal Din to generate the detection signal DS.

[0043] Next, in operation S420, the detection signal DS is compared with an amplitude threshold TH to generate a control signal CS. Specifically, the comparison circuit 122 compares the detection signal DS and the amplitude threshold TH. When the amplitude of the detection signal DS is not greater than the amplitude threshold TH, the comparison circuit 122 generates a first control signal. Conversely, when the amplitude of the detection signal DS is greater than the amplitude threshold TH, the comparison circuit 122 generates a second control signal.

[0044] Next, in operation S430, one of the plurality of noise transfer functions Fa, Fb is selected according to the control signal CS. Specifically, the integral-differential modulator 140 selects one from the plurality of noise transfer functions Fa, Fb stored in the integral-differential modulator 140 according to the control signal generated by the comparison circuit 122. For example, the integral-differential modulator 140 selects the noise transfer function Fa according to the first control signal, or selects the noise transfer function Fb according to the second control signal.

[0045] It should be noted that in other partial embodiments, the integral-differential modulator 140 can adjust the parameters of the noise transfer function stored in the integral-differential modulator 140 according to the control signal generated by the comparison circuit 122 to switch to use noise transfer functions with different performances, thereby weighing the input upper limit and the total harmonic distortion plus noise.

[0046] Next, in operation S440, the input signal Din is converted into an output signal Dout according to the selected noise transfer function. Specifically, the integral-differential modulator 140 converts the input signal Din into the output signal Dout according to the noise transfer function selected in operation S430.

[0047] Next, Figure 3 The noise transfer functions Fa and Fb in the embodiments are only examples. In other embodiments, if a plurality of noise transfer functions with different input upper limits and total harmonic distortion plus noise stability values are selected, the integral-differential modulator 140 can have a relatively Figure 3The wider dynamic range shown in the embodiments can be selected, which can further reduce the distortion probability of the integrator-differentiator modulator 140.

[0048] It should be understood that the purpose of the present invention application is to measure whether the input signal may cause system instability and dynamically provide a better noise transfer function. In the foregoing embodiments, it mainly detects the amplitude of the input signal and compares it with a specific threshold, which belongs to a relatively direct judgment method, but the present invention application is not limited thereto. In some embodiments, other indicators (such as energy, etc.) of the input signal can be detected to indirectly achieve the same purpose.

[0049] Although the methods disclosed herein are shown and described as a series of steps or events, it should be understood that the order of these steps or events shown should not be construed in a limiting sense. For example, some steps may occur in a different order and / or occur simultaneously with other steps or events other than those shown and / or described herein. Additionally, when implementing one or more of the technical solutions or embodiments described herein, not all of the steps shown here are necessary. Furthermore, one or more of the steps herein may be performed in one or more separate steps and / or phases.

[0050] In summary, by detecting the change in the amplitude of the input signal Din to generate a corresponding control signal to dynamically switch different noise transfer functions (such as Fa and Fb), the integrator-differentiator modulator 140 can maintain a good dynamic range and stability.

[0051] Although the content of the present invention application has been disclosed as above through specific embodiments, it is not intended to limit the content of the present invention application. Those of ordinary skill in the art should be able to make various modifications or adjustments without departing from the concept and scope of the content of the present invention application. Therefore, the protection scope of the content of the present invention application shall be subject to the scope defined by the claims.

Claims

1. An integral-differential modulation device, characterized in that, The integral-differential modulation device includes: a detection circuit for detecting an input signal to generate a detection signal, and comparing the detection signal with a threshold value to generate a control signal; and an integral-differential modulator coupled to the detection circuit for storing a plurality of noise transfer functions, selecting one of the plurality of noise transfer functions according to the control signal, and converting the input signal into an output signal according to the selected function among the plurality of noise transfer functions; The detection circuit includes: an envelope detector for receiving the input signal and detecting the amplitude change of the input signal to generate the detection signal; and a comparison circuit for receiving the detection signal and comparing the detection signal with the threshold value to generate the control signal; wherein when the detection signal is not greater than the threshold value, the comparison circuit is used to generate a first control signal, and when the detection signal is greater than the threshold value, the comparison circuit is used to generate a second control signal; the integral-differential modulator is used to select a first noise transfer function according to the first control signal and select a second noise transfer function according to the second control signal; a first input upper limit value of the first noise transfer function is less than a second input upper limit of the second noise transfer function, and a first total harmonic distortion plus noise of the first noise transfer function is less than a second total harmonic distortion plus noise of the second noise transfer function.

2. An integral-differential modulation method, characterized in that, The integral-differential modulation method is applicable to an integral-differential modulation device, the integral-differential modulation device includes an integral-differential modulator, the integral-differential modulator is used to store a plurality of noise transfer functions, and the integral-differential modulation method includes: detecting an input signal of the integral-differential modulator to generate a detection signal; comparing the detection signal with a threshold value to generate a control signal; selecting one of the plurality of noise transfer functions according to the control signal; and converting the input signal into an output signal according to the selected function among the plurality of noise transfer functions; wherein generating the detection signal includes: detecting the amplitude change of the input signal by an envelope detector to generate the detection signal; generating the control signal includes: comparing the detection signal with the threshold value by a comparison circuit; when the detection signal is not greater than the threshold value, the comparison circuit generates a first control signal; and when the detection signal is greater than the threshold value, the comparison circuit generates a second control signal; the integral-differential modulation method further includes: the integral-differential modulator selects a first noise transfer function according to the first control signal; and the integral-differential modulator selects a second noise transfer function according to the second control signal, wherein a first input upper limit value of the first noise transfer function is less than a second input upper limit of the second noise transfer function, and a first total harmonic distortion plus noise of the first noise transfer function is less than a second total harmonic distortion plus noise of the second noise transfer function.

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