System for realizing low-noise adjustable amplification of small voltage signal

Abstract

The invention relates to a system for realizing low-noise adjustable amplification of small voltage signals, which comprises a voltage adjustable amplification circuit, a second-order low-pass filter and a voltage follower circuit, the voltage adjustable amplification circuit receives signal input, the output end of the voltage adjustable amplification circuit is connected with the second-order low-pass filter, and the voltage follower circuit is connected with the second-order low-pass filter. The output end of the second-order low-pass filter is connected with the voltage follower circuit, the output end of the voltage follower circuit is connected with a post-stage acquisition system, the voltage adjustable amplification circuit is used for amplifying voltage signals, the second-order low-pass filter is used for selecting passband cut-off frequency to filter, and the voltage follower circuit is used for isolating noise between a front stage and a rear stage. And the voltage passing through the voltage follower is sent to a post-stage data acquisition system. By adopting the system for realizing the low-noise adjustable amplification of the small-voltage signal, the signals with different sizes can be amplified to be close to the same order of magnitude, the noise interference is reduced, and the problem that the weak small signal cannot be accurately measured in a severe environment is effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency power measurement, in particular to the field of small voltage signal detection, and specifically refers to a system for realizing low-noise adjustable amplification of small voltage signals. Background Art

[0002] In the measurement of RF power, integrated detection chips are often used. The detector outputs a voltage signal, and the effective output voltage signal is 10mV-1.5V. The voltage output by the detector needs to be sent to the ADC for detection. In order to improve the detection accuracy of the ADC, the voltage signal needs to be adjusted to a suitable range, that is, an adjustable amplifier circuit that amplifies small voltages and does not amplify large voltages. At the same time, each amplifier circuit needs to have the characteristics of high stability and high linearity. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a system for realizing low-noise adjustable amplification of small voltage signals which has the advantages of simple operation, good accuracy and a wide range of applications.

[0004] In order to achieve the above object, the system for realizing low-noise adjustable amplification of small voltage signals of the present invention is as follows:

[0005] The system for realizing low-noise adjustable amplification of small voltage signals has the following main features: the system comprises an adjustable voltage amplifier circuit, a second-order low-pass filter, and a voltage follower circuit; the adjustable voltage amplifier circuit receives a signal input; the output end of the adjustable voltage amplifier circuit is connected to the second-order low-pass filter; the output end of the second-order low-pass filter is connected to the voltage follower circuit; the output end of the voltage follower circuit is connected to a post-stage data acquisition system; the adjustable voltage amplifier circuit is used to amplify the voltage signal; the second-order low-pass filter is used to select a passband cutoff frequency for filtering; the voltage follower circuit is used to isolate noise between the front and rear stages, and send the voltage passing through the voltage follower to the post-stage data acquisition system.

[0006] Preferably, the voltage adjustable amplifier circuit includes a first operational amplifier, a first resistor, a third resistor and an adjustable gain unit, the non-phase input terminal of the first operational amplifier is connected to the third resistor, the inverting input terminal of the first operational amplifier is connected to the first resistor, and the adjustable gain unit is connected between the inverting input terminal and the output terminal of the first operational amplifier; the adjustable gain unit includes a multiplexing switch and an insertion resistor, and the multiplexing switch and the insertion resistor are connected in series.

[0007] Preferably, the voltage adjustable amplifier circuit amplifies the voltage signal, specifically:

[0008] The actual magnification A is calculated according to the following formula:

[0009]

[0010] Among them, R x is the resistance actually inserted into the circuit, R 内 is the internal resistance of the multiplexer switch.

[0011] Preferably, the second-order low-pass filter includes a second operational amplifier, a fourth resistor, a fifth resistor, a sixth resistor, a first capacitor, a second capacitor and a peripheral resistor, the fifth resistor and the sixth resistor are connected in series, the sixth resistor is connected to the non-inverting input terminal of the second operational amplifier, the fourth resistor is connected to the inverting amplifier of the second operational amplifier, the other end of the fourth resistor is grounded, the first capacitor is connected between the node between the fifth resistor and the sixth resistor and the output terminal of the second operational amplifier, one end of the second capacitor is connected to the non-inverting input terminal of the second operational amplifier, and the other end is grounded, and the peripheral resistor is connected between the inverting input terminal and the output terminal of the second operational amplifier.

[0012] The system for realizing low-noise adjustable amplification of small voltage signals of the present invention is adopted, and the hardware circuit design of adjustable voltage amplification, filtering and isolation is provided, so that signals of different sizes can be amplified to the same order of magnitude, and noise interference is reduced, and the problem of inaccurate measurement of weak signals in harsh environments is effectively solved. The measurement system can be widely used in analog acquisition circuits with high requirements for stability and measurement accuracy, and can accurately measure the changes of voltage signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The present invention is a schematic diagram of the structure of a system for realizing low-noise adjustable amplification of small voltage signals.

[0014] Figure 2 The present invention is a schematic structural diagram of a common-direction proportional amplifier circuit for realizing low-noise adjustable amplification of a small voltage signal in a system.

[0015] Figure 3 The present invention is a schematic diagram of the structure of a second-order low-pass filter circuit of a system for realizing low-noise adjustable amplification of a small voltage signal.

[0016] Figure 4 The present invention is a schematic diagram of the structure of a voltage follower circuit of a system for realizing low-noise adjustable amplification of a small voltage signal. DETAILED DESCRIPTION

[0017] In order to more clearly describe the technical content of the present invention, further description is given below in conjunction with specific embodiments.

[0018] The system for realizing low-noise adjustable amplification of small voltage signals of the present invention comprises a voltage adjustable amplifier circuit, a second-order low-pass filter, and a voltage follower circuit. The voltage adjustable amplifier circuit receives a signal input, the output end of the voltage adjustable amplifier circuit is connected to the second-order low-pass filter, the output end of the second-order low-pass filter is connected to the voltage follower circuit, the output end of the voltage follower circuit is connected to a post-stage data acquisition system, the voltage adjustable amplifier circuit is used to amplify the voltage signal, the second-order low-pass filter is used to select a passband cutoff frequency for filtering, and the voltage follower circuit is used to isolate noise between the front and rear stages, and send the voltage passing through the voltage follower to the post-stage data acquisition system.

[0019] As a preferred embodiment of the present invention, the voltage adjustable amplifier circuit includes a first operational amplifier, a first resistor, a third resistor and an adjustable gain unit, the non-phase input terminal of the first operational amplifier is connected to the third resistor, the inverting input terminal of the first operational amplifier is connected to the first resistor, and the adjustable gain unit is connected between the inverting input terminal and the output terminal of the first operational amplifier; the adjustable gain unit includes a multiplexing switch and an insertion resistor, and the multiplexing switch and the insertion resistor are connected in series.

[0020] As a preferred embodiment of the present invention, the voltage adjustable amplifier circuit amplifies the voltage signal, specifically:

[0021] The actual magnification A is calculated according to the following formula:

[0022]

[0023] Among them, R x is the resistance actually inserted into the circuit, R 内 is the internal resistance of the multiplexer switch.

[0024] As a preferred embodiment of the present invention, the second-order low-pass filter includes a second operational amplifier, a fourth resistor, a fifth resistor, a sixth resistor, a first capacitor, a second capacitor and a peripheral resistor, the fifth resistor and the sixth resistor are connected in series, the sixth resistor is connected to the non-inverting input terminal of the second operational amplifier, the fourth resistor is connected to the inverting amplifier of the second operational amplifier, the other end of the fourth resistor is grounded, the first capacitor is connected between the node between the fifth resistor and the sixth resistor and the output terminal of the second operational amplifier, one end of the second capacitor is connected to the non-inverting input terminal of the second operational amplifier, and the other end is grounded, and the peripheral resistor is connected between the inverting input terminal and the output terminal of the second operational amplifier.

[0025] Power detection is widely used in general-purpose measuring instruments. The power detection range, resolution and accuracy play a key role in the performance of the instrument. This patent is aimed at the requirements of large-scale, high-precision and high-stability output power monitoring of vector signal generators. A low-noise variable gain application for the detector output voltage signal is designed to achieve high stability and high linearity of voltage signal measurement.

[0026] In a specific embodiment of the present invention, an adjustable amplification circuit for a voltage signal is provided, which can cover a wide range of voltage changes, stabilize the final voltage output within a suitable range for subsequent measurement, and has the characteristics of high stability and high linearity. The amplification and measurement circuit uses an operational amplifier with different resistors to adjust the gain, and configures a first-order low-pass filter and a voltage follower circuit to achieve different proportions of amplification of signals with different voltage values. The system block diagram is shown in FIG. Figure 1 shown.

[0027] For tiny signals, especially at the microvolt level, it is necessary to reduce the introduction and interference of noise as much as possible in circuit design. The internal transistors of the operational amplifier will bring shot noise, and the internal resistors will also bring thermal noise. When selecting devices, you should pay attention to choosing low-noise devices. Because the circuit needs to be powered by an external power supply, it is necessary to reduce the power supply ripple and stray signals as much as possible to further improve the reliability of the system.

[0028] 1. Voltage adjustable amplifier circuit

[0029] The output voltage signal is positive, and the voltage entering the subsequent ADC detection is usually also positive, so it is necessary to use a proportional amplifier circuit to amplify the voltage signal. Figure 2 shown.

[0030] Input and output voltage relationship:

[0031]

[0032] It can be seen from formula 1 that the voltage amplification factor is determined by the ratio of R2 to R1. At this time, due to the determination of R1 and R2, the circuit amplification factor is fixed.

[0033] In the circuit design requirements, it is necessary to realize different magnification selection of input signals, and a single resistor cannot achieve this requirement. In the actual design circuit, R2 is replaced by a multi-way analog switch with resistors of different resistance values ​​to realize the adjustable magnification selection of the circuit.

[0034] The actual magnification A is calculated as:

[0035]

[0036] R xis the resistance actually inserted into the circuit, and R is the internal resistance of the multiplexer switch.

[0037] The internal resistance of each path of the multiplexer switch cannot be ignored. In practice, a multiplexer switch with smaller internal resistance can be selected.

[0038] 2. Second-order low-pass filter

[0039] The device power supply in the preamplifier circuit will introduce high-frequency spurious signals, which need to be filtered out by selecting a reasonable passband cutoff frequency through a filter. The second-order active low-pass filter is composed of two independent energy storage capacitors, external resistors and an operational amplifier, such as Figure 3 shown.

[0040] Design a second-order low-pass filter with a cutoff frequency of f and an equivalent quality factor of Q.

[0041]

[0042] Where s = jw,

[0043] By designing appropriate parameters to deduce the values ​​of circuit components, high-frequency noise can be filtered out during the low-pass filtering process.

[0044] 3. Voltage follower circuit

[0045] In order to reduce the impact of environmental noise on the measurement circuit, it is often necessary to add a voltage follower circuit between the measured circuit and the measurement circuit to ensure the accuracy of the measurement result. The circuit diagram is shown in the figure. Figure 4 shown.

[0046] The voltage follower circuit can effectively isolate the noise between the front and rear stages, and ensure that the voltage signals are basically consistent. The voltage passing through the follower is sent to the rear data acquisition system to complete the amplification and detection of small signals.

[0047] The specific implementation scheme of this embodiment can refer to the relevant description in the above embodiment, which will not be repeated here.

[0048] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0049] It should be noted that, in the description of the present invention, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "plurality" refers to at least two.

[0050] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0051] The system for realizing low-noise adjustable amplification of small voltage signals of the present invention is adopted, and the hardware circuit design of adjustable voltage amplification, filtering and isolation is provided, so that signals of different sizes can be amplified to the same order of magnitude, and noise interference is reduced, and the problem of inaccurate measurement of weak signals in harsh environments is effectively solved. The measurement system can be widely used in analog acquisition circuits with high requirements for stability and measurement accuracy, and can accurately measure the changes of voltage signals.

[0052] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A system for realizing low-noise adjustable amplification of small voltage signals, characterized in that: The system includes a voltage-adjustable amplifier circuit, a second-order low-pass filter, and a voltage follower circuit. The voltage-adjustable amplifier circuit receives a signal input, the output end of the voltage-adjustable amplifier circuit is connected to the second-order low-pass filter, the output end of the second-order low-pass filter is connected to the voltage follower circuit, and the output end of the voltage follower circuit is connected to a post-stage data acquisition system. The voltage-adjustable amplifier circuit is used to amplify the voltage signal, the second-order low-pass filter is used to select the passband cutoff frequency for filtering, and the voltage follower circuit is used to isolate noise between the front and rear stages, and send the voltage passing through the voltage follower to the post-stage data acquisition system.

2. The system for realizing low-noise adjustable amplification of small voltage signals according to claim 1, characterized in that: The voltage adjustable amplifier circuit includes a first operational amplifier, a first resistor, a third resistor and an adjustable gain unit, the non-phase input terminal of the first operational amplifier is connected to the third resistor, the inverting input terminal of the first operational amplifier is connected to the first resistor, and the adjustable gain unit is connected between the inverting input terminal and the output terminal of the first operational amplifier; the adjustable gain unit includes a multiplexing switch and an insertion resistor, and the multiplexing switch and the insertion resistor are connected in series.

3. The system for realizing low-noise adjustable amplification of small voltage signals according to claim 2, characterized in that: The voltage adjustable amplifier circuit amplifies the voltage signal, specifically: The actual magnification A is calculated according to the following formula: Among them, R x is the actual resistance inserted into the circuit, R 内 is the internal resistance of the multiplexer switch.

4. The system for realizing low-noise adjustable amplification of small voltage signals according to claim 1, characterized in that: The second-order low-pass filter includes a second operational amplifier, a fourth resistor, a fifth resistor, a sixth resistor, a first capacitor, a second capacitor and a peripheral resistor. The fifth resistor and the sixth resistor are connected in series, the sixth resistor is connected to the non-inverting input terminal of the second operational amplifier, the fourth resistor is connected to the inverting amplifier of the second operational amplifier, the other end of the fourth resistor is grounded, the first capacitor is connected between the node between the fifth resistor and the sixth resistor and the output terminal of the second operational amplifier, one end of the second capacitor is connected to the non-inverting input terminal of the second operational amplifier, and the other end is grounded, and the peripheral resistor is connected between the inverting input terminal and the output terminal of the second operational amplifier.

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