Signal generator analog channel structure and method for reducing signal ground noise

Abstract

The invention belongs to the technical field of electronic test instruments, and particularly relates to a signal generator analog channel structure and method for reducing signal floor noise, and the structure is sequentially connected with a first-stage amplification unit, a first attenuation network, a second-stage amplification unit, a second attenuation network and a power amplification unit along a signal transmission direction. Wherein the second-stage amplification unit adopts N operational amplifiers (N is greater than or equal to 2) which are arranged in parallel, and the noise density of the input reference voltage is remarkably reduced by utilizing the synchronous amplification effect of the parallel operational amplifiers on signals and the averaging effect on internal noise. In addition, each attenuation network adopts a passive resistance network controlled by a relay, so that nonlinear distortion and power supply noise introduced by an active switch are avoided. Through the synergistic effect of preceding-stage high-gain distribution, parallel operational amplifier noise reduction and relay passive attenuation, the overall bottom noise of an analog channel is effectively reduced, and the signal-to-noise ratio during small signal output is remarkably improved.

Description

Technical Field

[0001] This application relates to the field of signal generator technology, and in particular to a signal generator analog channel structure and a method for reducing signal noise floor. Background Technology

[0002] Signal generators are widely used in biomedicine, communications, aerospace, and other fields to provide accurate and highly stable test signals. Most current analog channels in signal generators employ an operational amplifier combined with a passive resistor attenuation network. The main technical problem with this structure is that, even with a reduced signal amplitude, the noise floor remains high when outputting small signals, resulting in a suboptimal signal-to-noise ratio.

[0003] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art.

[0004] Application content In view of at least one of the above technical problems, this application provides a signal generator analog channel structure and a method for reducing signal noise floor, which solves the problem in the prior art that when the signal amplitude is reduced, the noise floor is still high, resulting in an unsatisfactory signal-to-noise ratio.

[0005] In one aspect, a signal generator analog channel structure for reducing signal noise floor is provided. The analog channel structure includes a first-stage amplification unit, a second-stage amplification unit, and a power amplification unit connected sequentially along the signal transmission direction. The second-stage amplification unit includes N operational amplifiers connected in parallel, where N is greater than or equal to 2 and is an integer. The analog channel structure also includes multiple passive resistor attenuators. One passive resistor attenuator is connected between the first-stage amplification unit and the second-stage amplification unit, and multiple passive resistor attenuators are connected between the second-stage amplification unit and the power amplification unit. Each passive resistor attenuator is configured to be turned on or off by a switching unit.

[0006] This signal generator employs a simulated channel structure. By using N operational amplifiers connected in parallel in the second-stage amplification unit, and leveraging the coherent amplification and incoherent averaging of internal thermal noise by multiple operational amplifiers, it achieves a significant reduction in the input reference voltage noise density, effectively improving the system's signal-to-noise ratio compared to a single operational amplifier. Passive resistor attenuators, controlled by switching units, are configured between the first and second-stage amplification units and between the second stage and the power amplification unit, ensuring extremely high spectral purity of the output signal. Furthermore, this distributed passive attenuation architecture between stages and the final stage enables flexible matching and wide-range control of the output amplitude. This allows the signal generator system to prevent saturation distortion during large signal transmission while maintaining an extremely low noise floor when outputting small signals.

[0007] In some possible implementations, three passive resistor attenuators are connected between the second-stage amplification unit and the power amplification unit.

[0008] In some possible implementations, the gains of the three passive resistor attenuators are set to -10dB, -10dB, and -20dB, respectively.

[0009] In some possible implementations, the first input terminals of N parallel op-amps are connected to a passive resistor attenuator, the second input terminals of the N parallel op-amps are grounded, and the output terminals of the N parallel op-amps are connected to another passive resistor attenuator.

[0010] In some possible implementations, decoupling capacitors are connected to the power supply terminals of the op-amp to filter out power supply noise.

[0011] In some possible implementations, the switching unit includes a relay, which is configured such that when the relay is activated, the signal is attenuated by a passive resistor attenuator before flowing into the next stage.

[0012] In some possible implementations, the switching unit includes a driving circuit connected to a relay. The driving circuit includes a switching transistor and a freewheeling diode. The collector and emitter of the switching transistor are connected to the relay, respectively. The base of the switching transistor is used to receive the driving signal. The freewheeling diode is connected in parallel to the collector and emitter of the switching transistor.

[0013] In some possible implementations, the gain of the first-stage amplifier unit is greater than the gain of the second-stage amplifier unit.

[0014] In some possible implementations, the gain of the first-stage amplifier unit is +14dB, and the gain of the second-stage amplifier unit is +10dB.

[0015] Secondly, a method for reducing signal noise floor implemented by a signal generator analog channel structure for reducing signal noise floor is provided, comprising the following steps: Step S100: The filtered signal is amplified by the first stage amplification unit. The first stage amplification unit is a low noise figure amplifier and is set to high gain. Step S200: Selectively attenuate the signal using a passive resistor attenuator with a gain of -6dB. Step S300: The signal is amplified in the second stage by the second stage amplification unit. The input signal is synchronously amplified by N parallel operational amplifiers, so that the output signal power increases while the internal noise power of the uncorrelated operational amplifiers is averaged, thereby reducing the noise density of the input reference voltage and improving the signal-to-noise ratio. In step S400, the signal is selectively attenuated by multiple passive resistor attenuators, and then finally conditioned and output by a power amplification unit.

[0016] The present application will be further described below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a structural diagram of the analog channel structure of the signal generator provided in an embodiment of this application; Figure 2 A circuit diagram of two operational amplifiers connected in parallel is provided for one embodiment; Figure 3 This is a circuit diagram of the switching unit provided in this embodiment; Figure 4 This embodiment provides a circuit diagram of a passive resistor attenuator. Detailed Implementation

[0019] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0020] Most current analog channels for signal generators employ an operational amplifier combined with a passive resistor attenuation network. The main technical problem with this structure is that, even with a reduced signal amplitude when outputting a small signal, the noise floor remains high, resulting in a suboptimal signal-to-noise ratio. Based on these technical issues, this application provides a signal generator analog channel structure that reduces the signal noise floor.

[0021] The following section provides a detailed introduction to the analog channel structure of a signal generator for reducing signal noise floor.

[0022] Figure 1 This is a structural diagram of the analog channel structure of the signal generator provided in an embodiment of this application. Figure 1 As shown, one embodiment provides a signal generator analog channel structure for reducing signal noise floor, including a digital-to-analog conversion unit 100, a filtering unit 200, a first-stage amplification unit 300, a second-stage amplification unit 500, a power amplification unit 600, and a passive resistor attenuator 400. This signal generator analog channel structure solves the problem of excessively high noise floor and poor signal-to-noise ratio caused by the limitations of traditional attenuation and amplification architectures when outputting small signals in existing signal generators.

[0023] The analog channel structure includes a digital-to-analog converter unit 100, a filter unit 200, a first-stage amplifier unit 300, a second-stage amplifier unit 500, and a power amplifier unit 600 connected sequentially along the signal transmission direction. The second-stage amplifier unit 500 includes N operational amplifiers connected in parallel, where N is greater than or equal to 2 and is an integer. The analog channel structure also includes multiple passive resistor attenuators 400. One passive resistor attenuator 400 is connected between the first-stage amplifier unit 300 and the second-stage amplifier unit 500, and multiple passive resistor attenuators 400 are connected between the second-stage amplifier unit 500 and the power amplifier unit 600. Each passive resistor attenuator 400 is configured to be controlled to be turned on or off by a switching unit.

[0024] The analog channel structure refers to the entire hardware link from which the signal is output from the digital-to-analog converter, and after being conditioned by filtering, amplification, attenuation, etc., it is finally output to the port.

[0025] The first-stage amplification unit 300 is specifically a low-noise operational amplifier.

[0026] A passive resistor attenuator 400 refers to an attenuation network composed of passive components, excluding active components such as transistors. The passive resistor attenuator 400 is primarily used to linearly reduce signal amplitude without introducing power supply noise or nonlinear distortion common in active components.

[0027] The power amplifier unit 600 is specifically a power amplifier.

[0028] In operation, the input signal is first pre-amplified by the first-stage amplification unit 300 to increase the signal level, making it significantly higher than the noise floor of subsequent circuits. Then, according to the user-defined output amplitude requirements, the control system selectively activates each stage of the passive resistor attenuator 400 via a switching unit. When the signal enters the second-stage amplification unit 500, N parallel operational amplifiers process the signal simultaneously. Because the signals are coherent, the power of the parallel signal increases in a ratio of N... 2 The noise increases; however, the thermal noise and shot noise inside the op-amp are random and uncorrelated, and their noise power increases only by N. Finally, the signal is output through the final stage power amplifier unit 600. When a very small signal needs to be output, the switching unit operates, connecting multiple attenuators in series with the circuit, which significantly attenuates the signal amplitude. At the same time, due to the low-noise amplification and parallel noise reduction technology used in the front stage, the output noise floor is suppressed to an extremely low level.

[0029] The analog channel structure of the signal generator provided in this embodiment achieves a significant reduction in the input reference voltage noise density by setting N operational amplifiers in parallel in the second-stage amplification unit 500. This is achieved by utilizing the coherent amplification of the signal by multiple operational amplifiers and the incoherent averaging of internal thermal noise. Compared with a single operational amplifier, this effectively improves the signal-to-noise ratio of the system. By configuring passive resistor attenuators 400, which are controlled to be turned on or off by a switching unit, between the first-stage and second-stage amplification units 500 and between the second-stage and power amplification unit 600, extremely high spectral purity of the output signal is ensured. At the same time, through this distributed passive attenuation architecture between stages and the final stage, flexible matching and wide-range control of the output amplitude are achieved. This allows the signal generator system to prevent saturation distortion during large signal transmission and maintain an extremely low noise floor level when outputting small signals.

[0030] In some embodiments, three passive resistor attenuators 400 are connected between the second-stage amplification unit 500 and the power amplification unit 600. Specifically, the gains of the three passive resistor attenuators 400 are set to -10dB, -10dB, and -20dB, respectively.

[0031] Understandably, the signal generator system can control the switching of these three passive resistor attenuators 400 based on the target output amplitude. For example, switching on only the first one results in a 10dB attenuation. Switching on the first two results in a 20dB attenuation. Switching on all three results in a 40dB attenuation.

[0032] Thus, by setting the attenuation levels to -10, -10, and -20dB, and combining this with relay switching, an extremely wide dynamic range can be covered, enabling the signal generator to output both large volt-level signals and small microvolt-level signals. Furthermore, placing the large attenuation (e.g., -20dB) in the later stages and using step-by-step attenuation avoids the impedance matching difficulties and excessive resistor thermal noise problems associated with single-stage large attenuation. Step-by-step attenuation helps maintain constant impedance at each stage and reduces signal reflection.

[0033] Furthermore, the gain of the first-stage amplifier unit 300 is +14dB. The gain of the passive resistor attenuator 400 between the first-stage amplifier unit 300 and the second-stage amplifier unit 500 is -6dB. The gain of the power amplifier unit 600 is +15dB.

[0034] The three passive resistor attenuators 400 mentioned above, combined with the passive resistor attenuator 400 with a gain of -6dB located between the first-stage amplification unit 300 and the second-stage amplification unit 500, enable the system to achieve a large-range precision attenuation from 0dB to tens ofdB.

[0035] In some embodiments, the first input terminals of N parallel operational amplifiers are connected to a passive resistor attenuator 400, the second input terminals of the N parallel operational amplifiers are grounded, and the output terminals of the N parallel operational amplifiers are connected to another passive resistor attenuator 400.

[0036] Figure 2 A circuit diagram of two operational amplifiers connected in parallel is provided for one embodiment. For example... Figure 2 As shown, the operational amplifiers can specifically be operational amplifiers U2 and U3, and the specific structures of operational amplifiers U2 and U3 and their connections with other devices can be found in [reference needed]. Figure 2 This will not be elaborated upon here.

[0037] like Figure 2 As shown, the non-inverting inputs of the two operational amplifiers share the voltage signal from the previous stage. Each operational amplifier is connected to ground via a gain-setting resistor, or directly to its own output in unity-gain buffer mode. The outputs of each operational amplifier are connected in series with a small balancing resistor to form the overall output of the second-stage amplification unit 500. Through this connection of the outputs, the DC offset voltages between the two operational amplifiers tend to be averaged, thereby reducing the overall DC error of the output.

[0038] The second-stage amplifier unit 500 employs a parallel operational structure, which significantly improves the signal-to-noise ratio and reduces voltage noise density. Understandably, when N equals 2, assuming the gain of a single operational amplifier is G and the input signal is S... IN The external input noise is N IN Output signal S OUT =SIN *G, Total Output Noise N OUT = N IN *G+N AMPL1 , where N AMPL1 This refers to the output reference noise caused by the operational amplifier itself. Since SNR equals the output RMS signal power divided by the output RMS noise power, the signal-to-noise ratio (SNR) of a single operational amplifier is... (one) For: SNR (one) =(S OUT ) 2 / (N OUT ) 2 =(S IN *G) 2 / ((N IN *G) 2 +(N) AMPL1 ) 2 Assuming the external noise input power is minimized, the formula simplifies to: SNR (one) =(S IN *G) 2 / (N) AMPL1 ) 2 .

[0039] When a second operational amplifier is connected in parallel (i.e., the number in parallel is 2), the signals are correlated, and the voltages are added; however, the internal noise of the operational amplifier is uncorrelated, and the power is added. SNR (two) =(2S IN *G) 2 / ((2N IN *G) 2 +(√2((N AMPL1 ) 2 +(N AMPL2 ) 2 )))=(2S IN *G) 2 / ((2N IN *G) 2 +(√2N AMPL2 ) 2 ) = (S IN *G) 2 / ((N IN *G) 2 +0.5*(N AMPL2 Similarly, assuming the external input noise power is minimized, the formula simplifies to SNR. (two) =(S IN *G) 2 / (0.5*(N AMPL2Therefore, paralleling amplifiers improves the SNR and reduces the voltage noise density. For N amplifiers in parallel, the amplifier noise power is reduced by N, the input reference voltage noise density is reduced by √N, and the parallel structure also has the advantages of reducing output offset error and improving load capacity.

[0040] In some embodiments, a decoupling capacitor is connected to the power supply terminal of the operational amplifier to filter out power supply noise.

[0041] Understandably, when an operational amplifier outputs high-frequency, high-current signals, the parasitic inductance on the power supply line can cause a voltage drop. At this time, the decoupling capacitor quickly replenishes the charge to the operational amplifier, maintaining a stable power supply voltage. Simultaneously, the decoupling capacitor filters out any switching noise that may exist on the power supply line, preventing it from entering the operational amplifier and being amplified.

[0042] Thus, decoupling capacitors can prevent power supply noise from coupling into the signal path and prevent op-amp self-oscillation caused by power supply fluctuations.

[0043] like Figure 2 As shown, the decoupling capacitors can specifically be capacitors C28, C29, C30, C31, C1, C2, C19, and C20. For the specific structures of capacitors C28, C29, C30, C31, C1, C2, C19, and C20 and their connection relationships with other devices, please refer to [reference needed]. Figure 2 This will not be elaborated upon here.

[0044] Figure 3 This is a circuit diagram of the switching unit provided in this embodiment. Figure 4 This is a circuit diagram of a passive resistor attenuator provided in this embodiment. Figure 3 and Figure 4 As shown, in some embodiments, the switching unit includes a relay, which is configured such that when the relay is activated, the signal is attenuated by a passive resistor attenuator 400 before flowing into the next stage.

[0045] A relay is an electrical control device that uses the principle of electromagnetism to control the opening and closing of a high-voltage / high-current circuit through low voltage / small current.

[0046] like Figure 3 As shown, a relay may include a coil. When the coil is not energized, the signal is output directly from the relay's input terminal through the relay's DC path. When the coil is energized, the relay is connected to a passive resistor attenuator 400, and the signal is attenuated by the passive resistor attenuator 400 before flowing into the next stage.

[0047] The relay can specifically be referred to as relay K1, and the specific structure of relay K1 and its connection relationship with other devices are detailed in [reference needed]. Figure 3 This will not be elaborated upon here.

[0048] like Figure 3 As shown, in some embodiments, the switching unit includes a driving circuit connected to a relay. The driving circuit includes a switching transistor and a freewheeling diode. The collector and emitter of the switching transistor are respectively connected to the relay. The base of the switching transistor is used to receive the driving signal. The freewheeling diode is connected in parallel to the collector and emitter of the switching transistor.

[0049] When a passive resistor attenuator 400 is connected, the drive signal is high, the switching transistor is saturated and conducting, current flows through the relay coil, generating a magnetic field that attracts the armature, the relay contacts actuate, and the signal flows through the attenuation network. When the drive signal is low, the switching transistor is cut off. At this time, the current in the relay coil cannot change abruptly, generating an extremely high reverse induced electromotive force. This reverse electromotive force is dissipated through a freewheeling diode forming a loop, thereby clamping the collector voltage of the switching transistor to approximately +0.7V of the power supply voltage.

[0050] The switching transistor can be specifically a transistor Q1, and for the specific structure of transistor Q1 and its connection relationship with other devices, please refer to [reference needed]. Figure 3 This will not be elaborated upon here.

[0051] The freewheeling diode can specifically be diode D1, and please refer to the following for the specific structure of diode D1 and its connection relationship with other devices. Figure 3 This will not be elaborated upon here.

[0052] In some embodiments, the gain of the first-stage amplification unit 300 is greater than the gain of the second-stage amplification unit 500.

[0053] Specifically, the gain of the first-stage amplifier unit 300 is +14dB, and the gain of the second-stage amplifier unit 500 is +10dB.

[0054] To reduce the overall output noise of the analog channel, the analog channel structure of this signal generator is designed based on the noise figure formula of a multi-stage cascaded amplifier: F = F1 + ((F2-1) / G1) + ((F3-1) / G1G2) + ((F4-1) / G1G2G3) + ... From the above formula, it can be seen that to make the overall noise figure F low, the noise figure F1 of the first-stage amplifier unit 300 must be as low as possible, and the gain G1 of the first-stage amplifier unit 300 must be sufficiently large. Therefore, in this embodiment, a low-noise operational amplifier is selected as the first stage, and the gain is set to a relatively high +14dB to effectively suppress the impact of subsequent stage noise on the overall system.

[0055] Thus, by setting the gain of the first-stage amplifier unit 300 to +14dB, which is greater than the +10dB of the second-stage amplifier unit 500, the impact of noise introduced by subsequent circuits on the overall output noise floor is effectively suppressed. Furthermore, the allocation of +14dB and +10dB is not arbitrary, but rather takes into account the gain-bandwidth product of the operational amplifier and signal swing limitations. If the gain of the first-stage amplifier unit 300 is too high, it may cause clipping distortion when a large signal is input; if it is too low, it cannot effectively suppress noise in subsequent stages. The values ​​in this embodiment achieve an optimal balance between noise floor control and dynamic range.

[0056] Secondly, a method for reducing signal noise floor implemented by a signal generator analog channel structure for reducing signal noise floor is provided, comprising the following steps: Step S100: The filtered signal is amplified by the first-stage amplification unit 300. The first-stage amplification unit 300 is a low-noise-figure amplifier and is set to high gain. In step S100, the signal is filtered and then enters the first-stage amplification unit 300. This step utilizes a low-noise-figure amplifier for high-gain (e.g., +14dB) amplification. This step establishes a high signal-to-noise ratio benchmark for the system.

[0057] Step S200: Selectively attenuate the signal using a passive resistor attenuator 400, the gain of which is -6dB. In step S200, the signal passes through a -6dB passive resistor attenuator 400. This step is used to fine-tune the signal amplitude and serves as inter-stage isolation and impedance matching to prevent mutual load pulling between the first and second stages.

[0058] In step S300, the signal is amplified in the second stage by the second stage amplification unit 500. The input signal is synchronously amplified by N parallel operational amplifiers, which increases the output signal power while averaging the internal noise power of the uncorrelated operational amplifiers, thereby reducing the noise density of the input reference voltage and improving the signal-to-noise ratio. In step S300, the signal enters the second-stage amplification unit 500. In this step, N parallel operational amplifiers synchronously amplify the input signal. Physically, the signal voltages are superimposed in phase, while the background noise inside the operational amplifiers is randomly superimposed.

[0059] In step S400, the signal is selectively attenuated by multiple passive resistor attenuators 400, and then finally conditioned and output by the power amplification unit 600.

[0060] In step S400, the amplified signal enters a passive resistor attenuator network 400 consisting of -10dB, -10dB, and -20dB resistors for selective attenuation. Finally, it is amplified by a power amplifier to enhance its driving capability before being output. This step ensures that the final output signal retains the high purity obtained from the previous stage processing while meeting the amplitude requirements.

[0061] In the description of the embodiments of this application, unless otherwise stated, " / " means "or", for example, A / B can mean A or B; "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0062] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0063] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0064] The terms "coupled," "connected," or "connected" in the instruction manual include both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a connection made through an electrically conductive medium, which may have parasitic inductance or capacitance. An indirect connection may also include connections made through other active or passive devices to achieve the same or similar functional purpose, such as connections made through circuits or components such as switches or follower circuits.

[0065] In the detailed description of this specification, reference is made to the accompanying drawings, which form a part thereof, wherein like reference numerals always denote like parts, and wherein exemplary embodiments are shown by way of example that may be implemented. It should be understood that other embodiments may be utilized, and structural or logical changes may be made, without departing from the scope of this application. Therefore, the following detailed description should not be considered limiting.

[0066] The various operations in the specification may be described sequentially as multiple discrete actions or operations in a manner most conducive to understanding the claimed subject matter. However, the order of description should not be construed as implying that these operations must be sequentially related. Specifically, these operations may not be performed in the order presented. The described operations may be performed in a different order than in the described embodiments. Various additional operations may be performed in additional embodiments and / or the described operations may be omitted.

[0067] Various components and devices may be referred to or shown in the singular (e.g., “MOS transistor”, “transistor”, “switch”, etc.) in this document, but only for the convenience of discussion, and any element referred to in the singular may include multiple such elements as taught herein.

[0068] The above are merely preferred embodiments of this application and do not constitute any limitation on this application. Any person skilled in the art can make many possible variations and modifications to the technical solution of this application, or modify it into equivalent embodiments, without departing from the scope of the technical solution of this application. Therefore, all equivalent changes made based on the shape, structure, and principle of this application without departing from the content of the technical solution of this application should be covered within the protection scope of this application.

Claims

1. A signal generator analog channel structure for reducing signal noise floor, characterized in that, The analog channel structure includes a first-stage amplification unit, a second-stage amplification unit, and a power amplification unit connected sequentially along the signal transmission direction. The second-stage amplification unit includes N operational amplifiers connected in parallel, where N is greater than or equal to 2 and is an integer; The analog channel structure also includes multiple passive resistor attenuators. One passive resistor attenuator is connected between the first-stage amplification unit and the second-stage amplification unit, and multiple passive resistor attenuators are connected between the second-stage amplification unit and the power amplification unit. Each passive resistor attenuator is configured to be controlled to be turned on or off by a switching unit.

2. The analog channel structure for reducing signal noise floor of the signal generator according to claim 1, characterized in that, Three passive resistor attenuators are connected between the second-stage amplification unit and the power amplification unit.

3. The analog channel structure for reducing signal noise floor of the signal generator according to claim 2, characterized in that, The gains of the three passive resistor attenuators are set to -10dB, -10dB, and -20dB, respectively.

4. The analog channel structure for reducing signal noise floor of the signal generator according to claim 1, characterized in that, The first input terminals of the N parallel operational amplifiers are all connected to the passive resistor attenuator, the second input terminals of the N parallel operational amplifiers are grounded, and the output terminals of the N parallel operational amplifiers are all connected to another passive resistor attenuator.

5. The analog channel structure for reducing signal noise floor of the signal generator according to claim 4, characterized in that, The operational amplifier has a decoupling capacitor connected to its power supply terminal to filter out power supply noise.

6. The analog channel structure for reducing signal noise floor of a signal generator according to claim 1, characterized in that, The switching unit includes a relay, which is configured such that when the relay is activated, the signal is attenuated by the passive resistor attenuator before flowing into the next stage.

7. The analog channel structure for reducing signal noise floor of a signal generator according to claim 6, characterized in that, The switching unit includes a driving circuit connected to the relay. The driving circuit includes a switching transistor and a freewheeling diode. The collector and emitter of the switching transistor are respectively connected to the relay. The base of the switching transistor is used to receive the driving signal. The freewheeling diode is connected in parallel to the collector and emitter of the switching transistor.

8. The analog channel structure for reducing signal noise floor according to claim 1, characterized in that, The gain of the first-stage amplifier unit is greater than the gain of the second-stage amplifier unit.

9. The analog channel structure for reducing signal noise floor according to claim 8, characterized in that, The gain of the first stage amplifier unit is +14dB, and the gain of the second stage amplifier unit is +10dB.

10. A method implemented using the signal generator analog channel structure for reducing signal noise floor as described in claim 1, characterized in that, Includes the following steps: Step S100: The filtered signal is amplified by the first stage amplification unit. The first stage amplification unit is a low noise figure amplifier and is set to high gain. Step S200: Selectively attenuate the signal using a passive resistor attenuator with a gain of -6dB. Step S300: The signal is amplified in the second stage by the second stage amplification unit. The input signal is synchronously amplified by N parallel operational amplifiers, so that the output signal power increases while the internal noise power of the uncorrelated operational amplifiers is averaged, thereby reducing the noise density of the input reference voltage and improving the signal-to-noise ratio. In step S400, the signal is selectively attenuated by multiple passive resistor attenuators, and then finally conditioned and output by a power amplification unit.

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