Cascade continuous-time sigma-delta modulator with anti-out-of-band overshoot

Abstract

The application relates to the technical field of integrated circuits, and discloses a cascade continuous-time Sigma-Delta modulator capable of resisting out-of-band overshoot, which comprises a first-stage modulator comprising a first-stage integrator and a first-stage quantizer; a second-stage modulator comprising a second-stage integrator and a second-stage quantizer; a first adder used for adding outputs of the first-stage quantizer and the second-stage quantizer in a digital domain and outputting an output signal of the cascade continuous-time Sigma-Delta modulator; a second adder, an input end of which is respectively coupled to an inverted signal of the output signal and an input signal, and an output end of which is coupled to an input end of the first-stage integrator, so as to form a first feedback path; and a third adder, an input end of which is respectively coupled to the inverted signal of the output signal, an inverted signal of the input signal and an output end of the first-stage integrator, so as to form a second feedback path. The double-feedback structure makes the signal transfer function of the modulator have a roll-off characteristic in the out-of-band, thereby effectively suppressing the out-of-band overshoot.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, and in particular to a cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot. Background Technology

[0002] This section is intended to provide background or context for understanding the implementation of this application and is for reference only. It should not be construed as an admission by the applicant that this section pertains to prior art that was disclosed before the filing date of this application.

[0003] Sigma-Delta (Σ-Δ) modulators are key structures for achieving high-resolution analog-to-digital conversion using oversampling and noise shaping techniques. They are widely used in audio signal processing, high-precision data acquisition, communication systems, and RF receivers. Based on the integrator structure, Sigma-Delta modulators can be divided into discrete-time and continuous-time types. Continuous-time Sigma-Delta modulators, in particular, offer advantages such as low power consumption, strong clock jitter resistance, and high bandwidth utilization, making them an important implementation for high-performance analog-to-digital converters (ADCs).

[0004] In the design of high-order continuous-time Sigma-Delta modulators, a multi-stage cascaded structure is typically employed to achieve higher noise shaping order while maintaining system stability. This structure connects multiple low-order modulation loops sequentially to obtain equivalent high-order noise shaping performance. Traditional cascaded Sigma-Delta modulators require filters in the digital domain to cancel the quantization noise generated by the preceding modulators, thereby achieving high-order noise shaping. However, in practical circuits, due to non-ideal factors such as the finite gain of analog integrators, component mismatch, and clock jitter, the analog domain noise transfer function and the digital filter transfer function cannot be perfectly matched, leading to quantization noise leakage and reducing the modulator's signal-to-noise ratio and linearity.

[0005] Furthermore, for continuous-time Sigma-Delta modulators, their signal transfer function (STF) typically exhibits overshoot at out-of-band frequencies. When the input signal frequency is high, out-of-band overshoot can cause saturation in the modulator output, and in severe cases, even lead to loop instability, thereby limiting the maximum swing of the input signal and the system dynamic range. Existing improvement methods mainly focus on optimizing the noise cancellation path or adjusting the feedback topology. Most schemes can reduce quantization noise leakage, but they cannot effectively suppress the out-of-band overshoot problem of continuous-time modulators.

[0006] Therefore, how to reduce the out-of-band overshoot effect of continuous-time Sigma-Delta modulators while maintaining the high precision and stability of the cascaded structure has become a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] The purpose of this application is to provide a cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot, aiming to solve the problems of out-of-band overshoot and easy output saturation of the signal transfer function (STF) in existing continuous-time cascaded Sigma-Delta modulators under high-frequency input conditions. Although traditional cascaded structures can achieve high-order noise shaping, they rely on digital filters to cancel quantization noise in the preceding stage, resulting in drawbacks such as structural complexity, difficulty in transfer function matching, and noise leakage. This invention proposes a cascaded continuous-time Sigma-Delta modulator with a dual-feedback path structure, which achieves out-of-band overshoot suppression and quantization noise cancellation through analog domain structure improvements, thereby improving the linearity, stability, and adaptability of the modulator.

[0008] The first aspect of this application discloses a cascaded continuous-time Sigma-Delta modulator resistant to out-of-band overshoot, comprising:

[0009] The first-stage modulator includes a first-stage integrator and a first-stage quantizer coupled in sequence.

[0010] The second-stage modulator includes a second-stage integrator and a second-stage quantizer coupled in sequence.

[0011] The first adder, whose input is coupled to the output of the first-stage quantizer and the output of the second-stage quantizer, is used to add the output signals of the first-stage modulator and the second-stage modulator in the digital domain and output the output signal of the cascaded continuous-time Sigma-Delta modulator.

[0012] A second adder, the inputs of which are respectively coupled to the inverted output signal of the cascaded continuous-time Sigma-Delta modulator to form a first feedback path, the second adder adds the inverted output signal of the cascaded continuous-time Sigma-Delta modulator and the input signal of the cascaded continuous-time Sigma-Delta modulator, and outputs the sum to the input of the first-stage integrator; and

[0013] The third adder has its input terminals coupled to the inverted output signals of the cascaded continuous-time Sigma-Delta modulator to form a second feedback path. The third adder adds the inverted output signals of the cascaded continuous-time Sigma-Delta modulator, the inverted input signals of the cascaded continuous-time Sigma-Delta modulator, and the output signal of the first-stage integrator, and outputs the sum to the input terminal of the second-stage integrator.

[0014] In a preferred embodiment, the signal transfer function of the cascaded continuous-time Sigma-Delta modulator is H1. H2=1 / (s 2 τ1τ2), where H1 is the transfer function of the first-stage integrator, τ1 is the time constant of the first-stage integrator, H2 is the transfer function of the second-stage integrator, τ2 is the time constant of the second-stage integrator, and s is the Laplace operator.

[0015] In a preferred embodiment, the first-stage integrator includes a first operational amplifier, a first resistor, and a first capacitor;

[0016] The positive input terminal of the first operational amplifier is grounded, the first capacitor is coupled between the negative input terminal and the output terminal of the first operational amplifier, the first resistor is connected in series with the negative input terminal of the first operational amplifier, and the time constant τ1 of the first stage integrator is 1 / R1C1, where R1 is the resistance value of the first resistor and C1 is the capacitance value of the first capacitor.

[0017] In a preferred embodiment, the second-stage integrator includes a second operational amplifier, a second resistor, and a second capacitor;

[0018] The positive input terminal of the second operational amplifier is grounded, the second capacitor is coupled between the negative input terminal and the output terminal of the second operational amplifier, the second resistor is connected in series with the negative input terminal of the second operational amplifier, and the time constant of the second integrator is τ2=1 / R2C2, where R2 is the resistance value of the second resistor and C2 is the capacitance value of the second capacitor.

[0019] In a preferred embodiment, the signal transfer function of the cascaded continuous-time Sigma-Delta modulator has a roll-off characteristic in the high-frequency band to suppress out-of-band overshoot of the input signal in the high-frequency band.

[0020] In a preferred embodiment, the transfer function of the first-stage integrator is equal to the transfer function of the second-stage integrator.

[0021] In a preferred embodiment, the first-stage integrator and the second-stage integrator are continuous-time integrators.

[0022] In a preferred embodiment, the input signal is a differential signal, and the inverted signal of the input signal is the one that reverses the phase of the differential signal.

[0023] Compared with the prior art, this application has at least the following beneficial effects:

[0024] In the embodiments of this application, by introducing two feedback path paths in the continuous-time cascaded Sigma-Delta modulator, the dual feedback path structure enables the STF to roll off naturally outside the band, effectively preventing output saturation caused by high-frequency input, suppressing STF out-of-band overshoot, and improving the linearity and dynamic range of the modulator.

[0025] Furthermore, quantization noise cancellation is achieved through an analog domain feedback path structure, eliminating the need for digital filters and avoiding noise leakage caused by digital filter matching errors. Multi-stage quantization noise structural cancellation ensures the modulator remains stable under high-order noise shaping, significantly improving the signal-to-noise ratio and resolution.

[0026] Furthermore, it is effective for any noise transfer function and any order of Sigma-Delta modulator without relying on integrator transfer function matching, thus adapting to different processes and structures, resulting in stronger system robustness and improved system stability and design adaptability.

[0027] Furthermore, this application has a simple structure, requires no additional digital filtering module, facilitates system integration and application expansion, and can be directly applied to high-precision analog-to-digital conversion, audio signal acquisition and radio frequency receiving systems.

[0028] In summary, this invention effectively suppresses out-of-band overshoot while achieving high-order noise shaping in continuous-time Sigma-Delta modulators, thereby improving signal accuracy and system stability. It has significant technological innovation and application value.

[0029] The various technical features disclosed in the above-described invention, the various technical features disclosed in the following embodiments and examples, and the various technical features disclosed in the accompanying drawings can be freely combined to form various new technical solutions (all of which should be considered as having been recorded in this specification), unless such a combination of technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed. Features C and D are equivalent technical means that serve the same function, and technically only one needs to be used; it is impossible to use both simultaneously. Feature E can be technically combined with feature C. Therefore, the solution A+B+C+D should not be considered as having been recorded because it is technically infeasible, while the solution A+B+C+E should be considered as having been recorded. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. It should be understood that the accompanying drawings described below are merely some implementation examples of the present invention, and those skilled in the art can obtain other implementation examples based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of a cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot according to one embodiment of this application.

[0032] Figure 2 This is a schematic diagram of the structure of the first-stage integrator according to one embodiment of this application.

[0033] Figure 3 This is a schematic diagram of the structure of the second-stage integrator according to one embodiment of this application. Detailed Implementation

[0034] In the following description, many technical details are presented to help the reader better understand this application. However, those skilled in the art will understand that the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0036] The first embodiment of this application relates to a cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot, the structure of which is as follows: Figure 1As shown, the Sigma-Delta modulator includes a first-stage modulator and a second-stage modulator. The first-stage modulator includes a first-stage integrator 101 and a first-stage quantizer 102 coupled in sequence. The second-stage modulator includes a second-stage integrator 103 and a second-stage quantizer 104 coupled in sequence. The transfer function of the first-stage integrator 101 in the first-stage modulator is H1, the output signal of the first-stage quantizer (Q1) 102 in the first-stage modulator is V1, and the quantization noise is E1. The transfer function of the second-stage integrator 103 in the second-stage modulator is H2, the output signal of the second-stage quantizer (Q2) 104 in the second-stage modulator is V2, and the quantization noise is E2. in It is the input signal of the Sigma-Delta modulator, V out This is the output signal of the Sigma-Delta modulator. Input signal V in and output signal V out It is a differential signal, that is, the input signal V in Including V inn and V inp Output signal V out Including V outn and V outp For the sake of simplicity, only one end is shown in the diagram.

[0037] The Sigma-Delta modulator further includes a first adder 105, a second adder 106, and a third adder 107. The second adder 106 outputs V... x1 It is the input signal of the first-stage integrator 101101 in the first-stage modulator loop, and the V output of the third adder 107. x2 It is the input signal of the second-stage integrator 103103 in the second-stage modulator loop.

[0038] The input terminals of the first adder 105 are coupled to the output terminals of the first-stage quantizer 102 and the second-stage quantizer 104, respectively. The first adder 105 receives the output signal V1 of the first-stage modulator and the output signal V2 of the second-stage modulator, respectively, and adds them in the digital domain to obtain and output the output signal V of the cascaded continuous-time Sigma-Delta modulator. out The output of the first adder 105 is coupled to the input of the second adder 106 and the input of the third adder 107, respectively, forming two feedback paths.

[0039] The input terminals of the second adder 106 are respectively coupled to the output signal V of a cascaded continuous-time Sigma-Delta modulator. out The inverted signal and the input signal V of the cascaded continuous-time Sigma-Delta modulatorin The output of the second adder 106 is coupled to the input of the first-stage integrator 101. The second adder 106 is used to convert the output signal V... out The inverted signal and the input signal V in The output V after addition x1 To the input terminal of the first-stage integrator 101.

[0040] The inputs of the third adder 107 are respectively coupled to the output signals V of a cascaded continuous-time Sigma-Delta modulator. out The inverted signal, the input signal V of the cascaded continuous-time Sigma-Delta modulator in The inverted signal and the output signal V of the first-stage integrator 101 x1 Used to output signal V out The inverted signal, the input signal V in The inverted signal and signal V x1 The sum produces a V. x2 To the input terminal of the second-stage integrator 103.

[0041] It is understandable that the input signal V in It is a differential signal, and the input signal V in The inverted signal is the phase of the reversed differential signal; for example, a pair of differential signals V can be used to reverse the phase of the differential signal. inn and V inp The correspondence is reversed and then connected to the input of the third adder 107. Output signal V out It is a differential signal, and the output signal V out The inverted signal is the phase of the reversed differential signal; for example, a pair of differential signals V can be used to reverse the phase of the differential signal. outn and V outp After the correspondence is reversed, it is connected to the input of the second adder 106 and the input of the third adder 107.

[0042] The first-stage integrator 101 is a continuous-time integrator. (The structural reference for the first-stage integrator 101 is...) Figure 2 As shown. The first-stage integrator 101 includes a first operational amplifier 201, a first resistor 202, and a first capacitor 203. The positive input terminal of the first operational amplifier 201 is grounded. The first capacitor 203 is coupled between the negative input terminal and the output terminal of the first operational amplifier 201. The first resistor 202 is connected in series with the negative input terminal of the first operational amplifier 201. The time constant τ1 of the first-stage integrator 101 is 1 / R1C1, where R1 is the resistance value of the first resistor 202, and C1 is the capacitance value of the first capacitor 203. The negative input terminal of the first operational amplifier 201 is coupled to the output signal V of the third adder 107. x2 The integral result Vout1 is obtained and output to the first-stage quantizer 102.

[0043] The second-stage integrator 103 is a continuous-time integrator. (The structural reference for the second-stage integrator 103 is...) Figure 3 As shown. The second-stage integrator 103 includes a second operational amplifier 201', a second resistor 202', and a second capacitor 203'. The positive input terminal of the second operational amplifier 201' is grounded. The second capacitor 203' is coupled between the negative input terminal and the output terminal of the second operational amplifier 201'. The second resistor 202' is connected in series with the negative input terminal of the second operational amplifier 201'. The time constant τ2 of the second-stage integrator 103 is 1 / R2C2, where R2 is the resistance value of the second resistor 202' and C2 is the capacitance value of the second capacitor 203'. The negative input terminal of the second operational amplifier 201' is coupled to the output signal V of the second adder 106. x2 The integral result Vout2 is obtained and output to the second-stage quantizer 104.

[0044] The signal transfer function of a cascaded continuous-time Sigma-Delta modulator is H1 H2=1 / (s 2 τ1τ2), where H1 is the transfer function of the first-stage integrator 101, τ1 is the time constant of the first-stage integrator 101, H2 is the transfer function of the second-stage integrator 103, τ2 is the time constant of the second-stage integrator 103, and s is the Laplace operator. The transfer function H1 of the first-stage integrator 101 and the transfer function H2 of the second-stage integrator 103 can be equal. The signal transfer function H1 of the cascaded continuous-time Sigma-Delta modulator. H2 has a roll-off characteristic in the high-frequency band to suppress out-of-band overshoot of the input signal in the high-frequency band.

[0045] To better understand the technical solution of this application, a specific example is provided below. The details listed in this example are mainly for ease of understanding and are not intended to limit the scope of protection of this application.

[0046] Compared to a single-loop high-order Sigma-Delta modulator, a cascaded Sigma-Delta modulator uses multiple low-order noise shaping loops instead of a single high-order noise shaping loop, improving loop stability while achieving the same noise shaping effect. Taking a two-stage cascade as an example, common cascaded Sigma-Delta modulators require a digital filter to cancel the analog noise transfer function of the first-stage modulator loop, thus ensuring that the modulator's noise transfer function only includes the high-order noise shaping effect.

[0047] However, the analog noise transfer function depends on factors such as the finite operational amplifier gain of the integrator and the matching of passive components in the circuit, which alters the ideal noise transfer function. Consequently, it cannot completely cancel out the transfer function of the digital filter, resulting in noise leakage and degrading the modulator's performance.

[0048] Furthermore, for traditional feedforward continuous-time Sigma-Delta modulators, their out-of-band signal transfer function (STF) exhibits overshoot, leading to modulator output saturation when the input is high frequency.

[0049] This invention provides a cascaded continuous-time Sigma-Delta modulator with dual feedback paths. By adding two feedback paths to the cascaded Sigma-Delta modulator loop, the input transfer function of the modulator exhibits a roll-off when the input signal is at a high frequency, thus resisting out-of-band overshoot. Furthermore, it achieves high-order noise shaping without the need for digital filters and eliminates the need for transfer function matching between two filter stages, resulting in better adaptability. The orders of the two modulator stages can be arbitrarily selected.

[0050] Taking a two-stage cascaded Sigma-Delta modulator as an example, the core idea of ​​this invention is to introduce a feedback path from the output of the first-stage modulator to the cascaded first-stage integrator; unlike the traditional cascaded structure, a feedback path from the output of the second-stage modulator to the cascaded second-stage integrator is introduced; and the output of the first-stage integrator of the cascaded modulator is introduced to the input of the cascaded second-stage integrator, thus transforming the input signal V... in Invert the input connected to the cascaded second-stage integrator.

[0051] refer to Figure 1 As shown, the above-mentioned technical problem is solved through the following features:

[0052] 1. Output signal V out As the first feedback path, it feeds back to the cascaded first-stage integrator 101.

[0053] 2. Introduce a feedback path in the second-stage modulator to the cascaded second-stage integrator 103.

[0054] 3. The output of the first-stage integrator 101 of the cascaded modulator is introduced into the input of the second-stage integrator 103 of the cascaded modulator.

[0055] 4. Input signal V in After being inverted, it is connected to the input of the cascaded second-stage integrator 103.

[0056] 5. The output V1 of the first-stage quantizer 102 and the output V2 of the second-stage quantizer 104 are added in the digital domain to obtain the final output V of the cascaded Sigma-Delta. out .

[0057] The system's final output V out The derivation process is shown in the following formulas (1) and (2):

[0058] (1)

[0059] (2)

[0060] Substituting formula (2) into formula (1), we obtain the following formula (3):

[0061] (3)

[0062] Simplifying formula (3), we get the following formula (4):

[0063] (4)

[0064] If the transfer functions of the two cascaded integrators are equal, that is, the transfer function H1 of the first integrator = the transfer function H2 of the second integrator, we can obtain the following formula (5):

[0065] (5)

[0066] For a Sigma-Delta modulator, its noise transfer function (NTF) is given by the following formula (6):

[0067] (6)

[0068] Where H is the transfer function of the integrator.

[0069] Formula (5) can be rewritten as formula (7):

[0070] (7)

[0071] As can be seen from formula (7), the output V of the Sigma-Delta modulator out It is divided into two parts, one part is the input signal V in ×STF, the other part is the sum of the quantization noise E1 of the first-stage quantizer 102 and the quantization noise E2 of the second-stage quantizer 104, which has undergone two stages of noise shaping (NTF1×NTF2). Thus, we obtain the following formula (8):

[0072] (8)

[0073] The transfer function of a continuous-time integrator is typically... , τ1 and τ2 are the time constants of the two-stage integrator.

[0074] From the above calculation process, it can be found that there exists a signal transfer function (STF) of H1H2=1 / (s 2 The filtering function of τ1τ2) reduces the out-of-band overshoot of the input signal at high frequencies.

[0075] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, if it refers to performing an action according to an element, it means performing the action at least according to that element, including two cases: performing the action only according to that element, and performing the action according to that element and other elements. Expressions such as "multiple," "repeatedly," and "various" include two, two times, two kinds, and more than two, more than two times, and more than two kinds.

[0076] The term “coupled to” and its derivatives may be used in this document. “Coupled” can mean two or more elements in direct physical or electrical contact. However, “coupled” can also mean two or more elements in indirect contact with each other, but still cooperating or interacting with each other, and can mean one or more other elements coupled or connected between elements referred to as being coupled to each other.

[0077] All references to this specification are considered to be incorporated integrally into the disclosure of this application so that they can serve as the basis for modifications if necessary. Furthermore, it should be understood that the above descriptions are merely preferred embodiments of this specification and are not intended to limit the scope of protection of this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments of this specification should be included within the scope of protection of one or more embodiments of this specification.

Claims

1. A cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot, characterized in that, include: The first-stage modulator includes a first-stage integrator and a first-stage quantizer coupled in sequence. The second-stage modulator includes a second-stage integrator and a second-stage quantizer coupled in sequence. The first adder, whose input is coupled to the output of the first-stage quantizer and the output of the second-stage quantizer, is used to add the output signals of the first-stage modulator and the second-stage modulator in the digital domain and output the output signal of the cascaded continuous-time Sigma-Delta modulator. The second adder has its input terminals coupled to the inverted signals of the output signals of the cascaded continuous-time Sigma-Delta modulator to form a first feedback path. The second adder adds the inverted signals of the output signals of the cascaded continuous-time Sigma-Delta modulator and the input signals of the cascaded continuous-time Sigma-Delta modulator and outputs the result to the input terminal of the first-stage integrator. as well as The third adder has its input terminals coupled to the inverted output signal of the cascaded continuous-time Sigma-Delta modulator to form a second feedback path. The third adder adds the inverted output signal of the cascaded continuous-time Sigma-Delta modulator, the inverted input signal of the cascaded continuous-time Sigma-Delta modulator, and the output signal of the first-stage integrator, and outputs the sum to the input terminal of the second-stage integrator. The signal transfer function of the cascaded continuous-time Sigma-Delta modulator is H1. H 2， Where H1 is the transfer function of the first-stage integrator and H2 is the transfer function of the second-stage integrator.

2. The cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot as described in claim 1, characterized in that, The signal transfer function of the cascaded continuous-time Sigma-Delta modulator is H1. H2=1 / (s 2 τ1τ2), where τ1 is the time constant of the first-stage integrator, τ2 is the time constant of the second-stage integrator, and s is the Laplace operator.

3. The cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot as described in claim 2, characterized in that, The first-stage integrator includes a first operational amplifier, a first resistor, and a first capacitor; The positive input terminal of the first operational amplifier is grounded, the first capacitor is coupled between the negative input terminal and the output terminal of the first operational amplifier, the first resistor is connected in series with the negative input terminal of the first operational amplifier, and the time constant τ1 of the first stage integrator is 1 / R1C1, where R1 is the resistance value of the first resistor and C1 is the capacitance value of the first capacitor.

4. The cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot as described in claim 2, characterized in that, The second-stage integrator includes a second operational amplifier, a second resistor, and a second capacitor; The positive input terminal of the second operational amplifier is grounded, the second capacitor is coupled between the negative input terminal and the output terminal of the second operational amplifier, the second resistor is connected in series with the negative input terminal of the second operational amplifier, and the time constant of the second integrator is τ2=1 / R2C2, where R2 is the resistance value of the second resistor and C2 is the capacitance value of the second capacitor.

5. The cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot as described in claim 1, characterized in that, The signal transfer function of the cascaded continuous-time Sigma-Delta modulator has a roll-off characteristic in the high-frequency band to suppress out-of-band overshoot of the input signal in the high-frequency band.

6. The cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot as described in claim 1, characterized in that, The transfer function of the first-stage integrator is equal to the transfer function of the second-stage integrator.

7. The cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot as described in claim 1, characterized in that, The first-stage integrator and the second-stage integrator are continuous-time integrators.

8. The cascaded continuous-time Sigma-Delta modulator with anti-out-of-band overshoot as described in claim 1, wherein the input signal is a differential signal, and the inverted signal of the input signal is the phase inverted signal of the differential signal.

Images