Low-frequency low-noise tuning amplification system

Abstract

The invention discloses a low-frequency low-noise tuning amplification system, which relates to the technical field of low-frequency communication and comprises a control isolation driving circuit, a controllable attenuator group, a single-tuned filter and a low-noise amplifier, the input end of the control isolation driving circuit is connected with a control signal, the first output end of the control isolation driving circuit is connected with the first input end of the single tuned filter through the controllable attenuator group, and the control isolation driving circuit is used for carrying out signal attenuation on the first path of control signal to obtain an attenuated control signal; the second output end of the control isolation driving circuit is connected with the second input end of the single tuned filter; the single tuned filter is used for isolating the attenuated control signal and performing gain amplification, and performing gain amplification according to the second path of control signal to obtain a tuned output signal; and the low-noise amplifier is used for amplifying the tuned output signal. According to the invention, through the controllable attenuator, amplification saturation when signals and noise are too large is prevented; the single tuned filter has signal amplification gain and out-of-band rejection capability, so that the anti-interference performance of the low-frequency receiving front end is effectively improved; the digital control signal is isolated by controlling the isolation drive circuit, the influence of noise introduced by an external digital circuit is eliminated, and the anti-interference capability is improved.

Description

Technical Field

[0001] The present application relates to the field of computational electromagnetics, and more specifically, to a low-frequency and low-noise tuned amplification system. Background Art

[0002] Low-frequency (10kHz-100kHz) radio has a longer wavelength (3000m-30000m) and has good transmission and diffraction capabilities. At the same time, low-frequency radio exhibits low signal attenuation and propagates in the "ground-ionosphere waveguide". The propagation is reliable and stable, making it suitable for long-distance communications and communications through water and the ground.

[0003] However, low-frequency channels have the characteristics of severe noise interference, weak signals, and narrow available frequency bands. Low-frequency reception is easily affected by lightning noise and surrounding electrical interference. In order to adapt to signal reception in complex environments, tuned filters are generally used in engineering to suppress out-of-band interference and harmonics. The tuned filter selects the center frequency of the filter according to the preset communication frequency, thereby achieving signal frequency selective reception. The circuit noise of the active tuned filter is large, and it is easy to introduce external power supply noise interference. The passive filter composed of passive components has a low background noise and is suitable for low-frequency reception with weak signals and severe interference. The passive double-tuned filter circuit is usually designed to be complex, large in size, and difficult to debug and maintain.

[0004] In order to maintain the anti-interference performance of low-frequency reception and reduce the complexity of the low-frequency receiving circuit, the present invention proposes a low-frequency low-noise tuning and amplification module with pre-attenuation, single tuning filtering, control isolation drive, and low-noise amplification to achieve narrow-band filtering with frequency selectivity and ensure the anti-interference ability and low-noise performance of low-frequency reception. Summary of the invention

[0005] In response to at least one defect or improvement need of the prior art, the present invention provides a low-frequency, low-noise tuned amplification system, which solves the defects of the prior art and designs a controllable attenuator composed of a passive resistor network to achieve narrow-band filtering with frequency selectivity, thereby ensuring the anti-interference capability and low-noise performance of low-frequency reception.

[0006] To achieve the above object, according to a first aspect of the present invention, there is provided a low-frequency low-noise tuned amplifier system, comprising: a control isolation drive circuit, a controllable attenuator group, a single tuned filter and a low noise amplifier;

[0007] The control signal is connected to the input end of the control isolation drive circuit, and the first output end of the control isolation drive circuit is connected to the first input end of the single tuned filter through a controllable attenuator group, so as to obtain an attenuated control signal after performing signal attenuation on the first control signal; the second output end of the control isolation drive circuit is connected to the second input end of the single tuned filter;

[0008] The single tuned filter is used to isolate and gain-amplify the attenuated control signal, and to gain-amplify the second control signal to obtain a tuned output signal;

[0009] The input end of the low noise amplifier is connected to the output end of the single tuned filter for amplifying the tuned output signal.

[0010] Further, the single tuned filter comprises: a tuning transformer group, a compensation capacitor group and a tuning capacitor group;

[0011] The tuning transformer group includes a first relay group, which is used to control the on / off state of relays in the first relay group to select the tuning frequency and perform gain amplification;

[0012] The tuning capacitor group includes a binary capacitor group and a second relay group, which is used to control the on / off state of the relays in the second relay group to control the binary capacitor group to cooperate with the tuning transformer group to select the tuning frequency;

[0013] The compensation capacitor group is used to compensate for parasitic capacitance and inductance in the circuit.

[0014] Furthermore, the first relay group includes at least two groups of parallel relay branches, and the relay branches include a transformer and three relays.

[0015] Furthermore, the transformer includes an adjustment rod, and the adjustment rod is used to adjust the inductance.

[0016] Furthermore, the compensation capacitor group device includes at least two groups of parallel capacitance branches, and the capacitance branches include fixed capacitors and adjustable capacitors;

[0017] The fixed capacitor is used to compensate for parasitic capacitance and inductance in the circuit;

[0018] The adjustable capacitor is used to fine-tune the compensation capacitance.

[0019] Furthermore, the controllable attenuator group includes:

[0020] At least one set of attenuators and relays connected in series;

[0021] The relay is connected to the first output terminal of the control isolation drive circuit and is used to select the attenuation frequency;

[0022] The attenuator is connected to the first input end of the single-tuned filter and is used for performing signal attenuation on the first control signal to obtain an attenuated control signal.

[0023] Furthermore, the low noise amplifier is a common-gate common-source low noise amplifier circuit.

[0024] Furthermore, the control isolation driving circuit includes an AC photoelectric coupling chip and a driving chip;

[0025] The AC photoelectric coupling chip is used to isolate the control signal and generate an isolated control signal.

[0026] The driving chip is used to receive the isolation control signal and generate a relay control signal.

[0027] Furthermore, it also includes: a power supply voltage stabilizing circuit;

[0028] The power supply voltage stabilizing circuit is connected to the isolation driving circuit to maintain the stability of the power supply voltage and suppress the harmonic interference introduced by the power supply.

[0029] Furthermore, the power supply voltage stabilization circuit includes: a parallel buck linear voltage stabilizer, a filter capacitor group and a resistor connected in parallel with each other.

[0030] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0031] (1) The present invention provides a low-frequency, low-noise tuned amplification system that constructs a controllable attenuator composed of a passive resistor network to prevent amplification saturation when the signal and noise are too large; a passive single-tuned filter composed of a tuning transformer group and a tuning capacitor group has both signal amplification gain and out-of-band suppression capabilities, effectively improving the anti-interference performance of the low-frequency receiving front end; a common-gate common-source low-noise amplifier with amplification gain is used to reduce voltage noise and has excellent sensitivity performance; a digital control signal is isolated by controlling an isolation drive circuit to eliminate the influence of noise introduced by an external digital circuit, thereby improving the anti-interference capability.

[0032] (2) The power supply voltage of the present invention is kept stable through the power supply voltage stabilization circuit, while suppressing the harmonic interference introduced by the power supply. A low-frequency low-noise tuned amplifier module with pre-attenuation, single tuned filtering, control isolation drive, and low-noise amplification is designed to achieve frequency-selective narrowband filtering, ensuring the anti-interference ability and low-noise performance of low-frequency reception. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1One of the structural schematic diagrams of an optional low-frequency low-noise tuned amplification system provided in an embodiment of the present application;

[0035] Figure 2 A second structural schematic diagram of an optional low-frequency low-noise tuned amplifier system provided in an embodiment of the present application;

[0036] Figure 3 A schematic diagram of the structure of an optional controllable attenuator provided in an embodiment of the present application;

[0037] Figure 4 A schematic diagram of the structure of an optional single-tuned filter provided in an embodiment of the present application;

[0038] Figure 5 A schematic diagram of the structure of an optional low noise amplifier provided in an embodiment of the present application;

[0039] Figure 6 A schematic diagram of the structure of an optional control isolation drive circuit provided in an embodiment of the present application;

[0040] Figure 7 A schematic diagram of the structure of an optional power supply voltage stabilization circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] The terms "first", "second", "third", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0043] According to one aspect of the embodiments of the present application, a low-frequency low-noise tuned amplifier system is provided. Figure 1-7 The low-frequency, low-noise tuned amplification system provided by an embodiment of the present application is described.

[0044] Figure 1is one of the structural schematic diagrams of an optional low-frequency low-noise tuned amplification system provided in an embodiment of the present application, such as Figure 1 As shown, the system includes: a control isolation drive circuit, a controllable attenuator group, a single tuned filter and a low noise amplifier;

[0045] The input end of the control isolation drive circuit is connected to the control signal, and the first output end of the control isolation drive circuit is connected to the first input end of the single tuned filter through a controllable attenuator group, so as to obtain an attenuated control signal after attenuation of the first control signal; the second output end of the control isolation drive circuit is connected to the second input end of the single tuned filter.

[0046] The single tuned filter is used to isolate and gain-amplify the attenuated control signal, and to gain-amplify the second control signal to obtain a tuned output signal.

[0047] The input end of the low noise amplifier is connected to the output end of the single tuned filter for amplifying the tuned output signal.

[0048] Further, the single tuned filter comprises: a tuning transformer group, a compensation capacitor group and a tuning capacitor group;

[0049] The tuning transformer group includes a first relay group, which is used to control the on / off state of relays in the first relay group to select the tuning frequency and perform gain amplification;

[0050] The tuning capacitor group includes a binary capacitor group and a second relay group, which is used to control the on / off state of the relays in the second relay group to control the binary capacitor group to cooperate with the tuning transformer group to select the tuning frequency;

[0051] Compensation capacitor group is used to compensate for parasitic capacitance and inductance in the circuit.

[0052] In one embodiment, the first relay group includes at least two relay branches connected in parallel, and the relay branches include a transformer and three relays.

[0053] The transformer includes an adjusting rod, and the adjusting rod is used to adjust the inductance.

[0054] Further, the compensation capacitor group device includes at least two groups of parallel capacitance branches, and the capacitance branches include fixed capacitors and adjustable capacitors;

[0055] Fixed capacitors are used to compensate for parasitic capacitance and inductance in the circuit;

[0056] Adjustable capacitor, used to fine-tune the compensation capacitance.

[0057] In a preferred embodiment, the tuned transformer provides a voltage gain of 35.6 dB (60 times), the low noise amplifier provides a voltage gain of 40 dB, the insertion loss of the single tuned filter is about 15.6 dB, and the total gain of the present invention is 60 dB.

[0058] The single tuned filter consists of a tuning transformer group, a tuning capacitor group and a compensation filter group. The input impedance of the tuned filter is 50 ohms, the 3dB bandwidth is the communication center frequency * 1.5%, the 30dB bandwidth is the communication center frequency * 12%, the gain is 20dB, and the tuning step is 100Hz.

[0059] The tuning transformer group is composed of 5 transformers and 15 relays. The tuning frequency ranges of the 5 transformers are 10kHz-16kHz, 16.1kHz-25.6kHz, 25.7kHz-41kHz, 41.1kHz-65.5kHz, and 65.6kHz-100kHz, respectively. The tuning transformer group selects the tuning frequency range of the present invention through relays. The input impedance of the five transformers is 50 ohms, the primary-to-secondary turns ratio is 1:60, and the input-to-output voltage ratio is 1:60, and a voltage gain of 35.6dB (60 times) can be provided. Each transformer is designed with an adjustment rod, which can fine-tune the inductance of the transformer.

[0060] The tuning capacitor group is composed of 8 fixed capacitors and 8 relays. The tuning capacitor group selects the tuning frequency of the present invention through the relays. The 8 fixed capacitors constitute a binary capacitor group, which is controlled by 8 relays and cooperates with the tuning transformer group to select the tuning frequency. The tuning step is 100Hz, which takes into account the requirements of tuning accuracy and debugging complexity.

[0061] The compensation capacitor group consists of 5 fixed capacitors and 5 adjustable capacitors. The 5 fixed capacitors compensate for the parasitic capacitance and inductance in the circuit, and the 5 adjustable capacitors can fine-tune the compensation capacitance.

[0062] Optional, controllable attenuator set includes:

[0063] at least one set of attenuators and relays connected in series;

[0064] The relay is connected to the first output terminal of the control isolation drive circuit and is used to select the attenuation frequency;

[0065] The attenuator is connected to the first input end of the single-tuned filter and is used for performing signal attenuation on the first control signal to obtain an attenuated control signal.

[0066] In a preferred embodiment, the controllable attenuator group is composed of a 10dB attenuator, a 20dB attenuator and four relays, wherein the 10dB attenuator and the 20dB attenuator are composed of a resistor network. The controllable attenuator selects four-speed attenuation (0dB, 10dB, 20dB, 30dB) through the relay, and attenuates the signal and noise when they are too large to prevent the module from being amplified and saturated at the back end.

[0067] Optionally, the low noise amplifier is a common-gate common-source low noise amplifier circuit.

[0068] In a preferred embodiment, the low noise amplifier is composed of two junction N-channel field effect transistors 2SK170, one triode 3DX6D, etc. The low noise amplifier is a common gate common source low noise amplifier circuit, which amplifies the signal by 40dB and has the characteristics of high input impedance and low noise source resistance.

[0069] Optionally, the control isolation drive circuit includes an AC photoelectric coupling chip and a drive chip;

[0070] The AC optocoupler chip is used to isolate the control signal and generate an isolated control signal.

[0071] The driver chip is used to receive the isolation control signal and generate the relay control signal.

[0072] In a preferred embodiment, the low-frequency low-noise tuned amplifier system further includes: a power supply voltage stabilizing circuit; the power supply voltage stabilizing circuit is connected to the isolation drive circuit to maintain the stability of the power supply voltage and suppress harmonic interference introduced by the power supply.

[0073] Optionally, the power supply voltage stabilization circuit includes: a parallel buck linear voltage regulator, a filter capacitor group and a resistor connected in parallel with each other.

[0074] The following is described with a specific embodiment:

[0075] Figure 2 This is a second structural diagram of an optional low-frequency low-noise tuned amplifier system provided in an embodiment of the present application, such as Figure 2 As shown, the present invention provides a low-frequency low-noise tuned amplification system, including: a control isolation drive circuit, a controllable attenuator group, a single tuned filter and a low noise amplifier. In this embodiment, the gain of the present invention is 60dB, with four levels of controllable attenuation (0dB, 10dB, 20dB, 30dB), and the equivalent input noise voltage of the present invention is not more than 1.3nV / Hz1 / 2.

[0076] The bandwidth of the present invention is the communication center frequency*1.5% (for example, when the communication center frequency is 10kHz, the bandwidth is 150Hz, and when the communication center frequency is 100kHz, the bandwidth is 1.5kHz). The present invention can filter out-of-band signals that deviate from the communication center frequency*0.75%, and the filtering capacity of the far-end frequency (6% deviating from the communication center frequency) reaches 30dB, which can effectively suppress interference outside the working frequency.

[0077] The tuning transformer of the present invention provides a voltage gain of 35.6 dB (60 times), the low noise amplifier provides a voltage gain of 40 dB, the tuning filter insertion loss is about 15.6 dB, and the total gain of the present invention is 60 dB.

[0078] The specific implementation parameters are as follows:

[0079] 6.1 Controllable attenuator group

[0080] The controllable attenuator group consists of a 10dB attenuator, a 20dB attenuator and four relays, where the 10dB attenuator and the 20dB attenuator are composed of a resistor network, such as Figure 3 The controllable attenuator selects four levels of attenuation (0dB, 10dB, 20dB, 30dB) through the relay. When the signal and noise are too large, they are attenuated to prevent the module's rear-end amplification saturation.

[0081] The 10dB attenuator is a resistor network composed of resistors R1, R2, and R3, which can attenuate the signal by 10dB. The 20dB attenuator is a resistor network composed of resistors R4, R5, and R6, which can attenuate the signal by 20dB.

[0082] The control signal IO-01 controls relays K1 and K2. When the control signal IO-01 is at a high level, a 10dB attenuator is connected to the signal path to attenuate the signal by 10dB.

[0083] The control signal IO-02 controls relays K3 and K4. When the control signal IO-01 is at a high level, a 10dB attenuator is connected to the signal path to attenuate the signal by 10dB.

[0084] The main device parameters of the controllable attenuator group are:

[0085] The resistance value of R1 is 100Ω, with an accuracy of 1%; the resistance value of R2 is 75Ω, with an accuracy of 1%; the resistance value of R3 is 100Ω, with an accuracy of 1%; the resistance value of R4 is 62Ω, with an accuracy of 1%; the resistance value of R5 is 220Ω, with an accuracy of 1%; the resistance value of R6 is 62Ω, with an accuracy of 1%.

[0086] K1~K4 are HF49FD / -12 single-pole single-throw relays with a power supply voltage of 12V.

[0087] 6.2 Single-tuned filter

[0088] The single tuned filter consists of a tuning transformer group, a tuning capacitor group and a compensation filter group, such as Figure 4 As shown, the input impedance of the tuning filter is 50 ohms, the 3dB bandwidth is the communication center frequency * 1.5%, the 30dB bandwidth is the communication center frequency * 12%, the gain is 20dB, and the tuning step is 100Hz.

[0089] 6.2.1 Tuning transformer group

[0090] The tuning transformer group is composed of 5 transformers and 15 relays. The tuning frequency ranges of the 5 transformers (T1, T2, T3, T4, and T5) are 10kHz-16kHz, 16.1kHz-25.6kHz, 25.7kHz-41kHz, 41.1kHz-65.5kHz, and 65.6kHz-100kHz, respectively. The tuning transformer group selects the tuning frequency range of the present invention through 15 relays (K5-K19). Each transformer has an input impedance of 50 ohms, a primary-to-secondary turns ratio of 1:60, an input-to-output voltage ratio of 1:60, and can provide a voltage gain of 35.6dB (60 times).

[0091] The tuning transformer can isolate the attenuator output signal (OUT1+, OUT1-) and supports both single-ended input and differential input modes. Each transformer is designed with an adjustment rod to fine-tune the inductance of the transformer.

[0092] The control signal IO-03 controls relays K5, K6, and K7. When the control signal IO-03 is at a high level, the transformer T1 is connected to the signal path, and the tuning frequency range is 10kHz-16kHz.

[0093] The control signal IO-04 controls relays K8, K9, and K10. When the control signal IO-04 is at a high level, the transformer T2 is connected to the signal path, and the tuning frequency range is 16.1kHz-25.6kHz.

[0094] The control signal IO-05 controls relays K11, K12, and K13. When the control signal IO-05 is at a high level, the transformer T3 is connected to the signal path, and the tuning frequency range is 25.7kHz-41kHz.

[0095] The control signal IO-06 controls relays K14, K15, and K16. When the control signal IO-06 is at a high level, the transformer T4 is connected to the signal path, and the tuning frequency range is 41.1kHz-65.5kHz.

[0096] The control signal IO-07 controls relays K17, K18, and K19. When the control signal IO-07 is at a high level, the transformer T5 is connected to the signal path, and the tuning frequency range is 65.6kHz-100kHz.

[0097] The main device parameters of the tuned transformer group are:

[0098] The primary inductance L11 of T1 is 233.4uH, and the secondary inductance L12 is 840mH. The primary inductance L21 of T2 is 86.4uH, and the secondary inductance L22 is 312mH. The primary inductance L31 of T3 is 34.8uH, and the secondary inductance L32 is 126mH. The primary inductance L41 of T4 is 13.2uH, and the secondary inductance L42 is 48mH. The primary inductance L51 of T5 is 4.2uH, and the secondary inductance L52 is 15mH.

[0099] K5~K19 are HF49FD / -12 single-pole single-throw relays with a power supply voltage of 12V.

[0100] 6.2.2 Tuning capacitor bank

[0101] The tuning capacitor group is composed of 8 fixed capacitors (C1, C2, C3, C4, C5, C6, C7, C8) and 8 relays (K20, K21, K22, K23, K24, K25, K26, K27). The tuning capacitor group selects the tuning frequency of the present invention through the relay. The 8 fixed capacitors constitute a binary capacitor group, which is controlled by 8 relays and cooperates with the tuning transformer group to select the tuning frequency. The tuning step is 100Hz, which takes into account the requirements of tuning accuracy and debugging complexity.

[0102] The control signal IO-08 controls the relay K20. When the control signal IO-08 is at a high level, the fixed capacitor C1 is connected to the signal path.

[0103] The control signal IO-09 controls the relay K20. When the control signal IO-09 is at a high level, the fixed capacitor C2 is connected to the signal path.

[0104] The control signal IO-010 controls the relay K20. When the control signal IO-010 is at a high level, the fixed capacitor C3 is connected to the signal path.

[0105] The control signal IO-011 controls the relay K20. When the control signal IO-011 is at a high level, the fixed capacitor C4 is connected to the signal path.

[0106] The control signal IO-012 controls the relay K20. When the control signal IO-012 is at a high level, the fixed capacitor C5 is connected to the signal path.

[0107] The control signal IO-013 controls the relay K20. When the control signal IO-013 is at a high level, the fixed capacitor C6 is connected to the signal path.

[0108] The control signal IO-014 controls the relay K20. When the control signal IO-014 is at a high level, the fixed capacitor C7 is connected to the signal path.

[0109] The control signal IO-015 controls the relay K20. When the control signal IO-015 is at a high level, the fixed capacitor C8 is connected to the signal path.

[0110] The main device parameters of the tuning capacitor bank are:

[0111] C1 is a mica capacitor with a capacitance of 1pF and an accuracy of 1%; C2 is a mica capacitor with a capacitance of 2pF and an accuracy of 1%; C3 is a mica capacitor with a capacitance of 4pF and an accuracy of 1%; C4 is a mica capacitor with a capacitance of 8pF and an accuracy of 1%; C5 is a mica capacitor with a capacitance of 16pF and an accuracy of 1%; C6 is a mica capacitor with a capacitance of 32pF and an accuracy of 1%; C7 is a mica capacitor with a capacitance of 64pF and an accuracy of 1%; C8 is a mica capacitor with a capacitance of 128pF and an accuracy of 1%.

[0112] K20~K27 are HF49FD / -12 single-pole single-throw relays with a power supply voltage of 12V.

[0113] 6.2.3 Compensation capacitor bank

[0114] The compensation capacitor group consists of 5 fixed capacitors (C9, C10, C11, C12, C13) and 5 adjustable capacitors (C14, C15, C16, C17, C18) to compensate for the parasitic capacitance and inductance in the circuit. The 5 adjustable capacitors can fine-tune the compensation capacitance.

[0115] C9 and C14 compensate for the tuning frequency range of 10kHz-16kHz. C10 and C15 compensate for the tuning frequency range of 16.1kHz-25.6kHz. C11 and C16 compensate for the tuning frequency range of 25.7kHz-41kHz. C12 and C17 compensate for the tuning frequency range of 41.1kHz-65.5kHz. C3 and C18 compensate for the tuning frequency range of 65.6kHz-100kHz.

[0116] The main device parameters of the compensation capacitor bank are:

[0117] C9, C10, C11, C12, and C13 are all mica capacitors with a capacitance of 51pF and an accuracy of 1%; C14, C15, C16, C17, and C18 are all adjustable capacitors with a maximum capacitance of 100pF.

[0118] 6.2.4 Tuning truth table

[0119] The tuning true values ​​of the highest and lowest frequencies in each tuning range are shown in the following table. In each tuning range, the larger the tuning capacitance, the lower the tuning frequency, and the smaller the tuning capacitance, the higher the tuning frequency.

[0120]

[0121] 6.3 Low Noise Amplifier

[0122] The low noise amplifier is composed of two field effect tubes 2SK170, one transistor 3DX6D, etc. Figure 5 The low noise amplifier is a common-gate common-source low noise amplifier circuit, which amplifies the signal by 40dB and has the characteristics of high input impedance and low noise source resistance.

[0123] Diodes D1 and D2 are connected in parallel at the input end to provide a discharge circuit for large signals to prevent damage to the amplifier circuit.

[0124] 2SK170 is a junction N-channel field effect transistor with ultra-low noise and high input impedance, providing amplification gain for low noise amplifiers. Transistor 3DX6D is an NPN transistor, providing current drive for low noise amplifiers.

[0125] The main device parameters of the low noise amplifier are:

[0126] Q1 and Q2 are junction N-channel field effect transistors with a noise voltage of 0.95nV / Hz1 / 2 (1kHz-100kHz) and a gate leakage current of -1nA; Q3 is a silicon low-frequency, low-noise, low-power NPN transistor 3DX6D; D1 and D2 are voltage-stabilizing diodes 1N5818.

[0127] The capacitance of C19, C019, C20 and C020 are all 4.7uF; the capacitance of C21 is 0.1uF.

[0128] The resistance value of R7 is 3kΩ, with an accuracy of 1%; the resistance value of R8 is 200kΩ, with an accuracy of 1%; the resistance value of R9 is 9kΩ, with an accuracy of 1%; the resistance value of R10 is 25kΩ, with an accuracy of 1%; R11 is an adjustable resistor with a maximum resistance of 10kΩ; the resistance value of R12 is 200Ω, with an accuracy of 1%; the resistance value of R13 is 1kΩ, with an accuracy of 1%; the resistance value of R14 is 200kΩ, with an accuracy of 1%; the resistance value of R15 is 9kΩ, with an accuracy of 1%; the resistance value of R16 is 2.5kΩ, with an accuracy of 1%.

[0129] 6.4 Control isolation drive circuit

[0130] The control isolation drive circuit is composed of 15 AC photoelectric coupling chips (U1~U15), 3 Darlington tube driver chips (U16~U18), etc. Figure 6 shown.

[0131] The control isolation drive circuit first isolates 15 digital control signals (IO1 to IO15) to generate 15 isolation control signals (IO-1 to IO-15).

[0132] Then, the driving capability of the isolated control signal (IO-1 to IO-15) is improved through the driver chip to generate a relay control signal (IO-01 to IO-015).

[0133] The main device parameters of the control isolation drive circuit are:

[0134] U1~U15 are all single-channel AC optocoupler chips PS2805-1, and U16~U18 are all seven-channel Darlington tube driver chips MC1413.

[0135] The resistance values ​​of R17~R61 are all 1kΩ.

[0136] 6.5 Power supply voltage regulator circuit

[0137] The power supply voltage stabilization circuit consists of a voltage stabilizer (U19), filter capacitors (C23-C28), resistors (R62, R63), etc. Figure 7 As shown, the power supply voltage regulator circuit can ensure the stability of the power supply voltage and effectively suppress the harmonic interference introduced by the power supply. The power input POWER voltage range of the present invention is +15V to +37V, and the voltage regulator converts the power input voltage into the voltage +12V required by other circuits of the present invention.

[0138] The main device parameters of the power supply voltage regulator circuit are, for example:

[0139] U19 is a step-down linear regulator LM317.

[0140] The resistance value of R62 is 1KΩ, and the resistance value of R63 is 8.6KΩ.

[0141] The capacitance values ​​of C23, C25 and C27 are all 0.01uF; the capacitance values ​​of C24, C26 and C28 are all 100uF.

[0142] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

[0143] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0144] The above is only an exemplary embodiment of the present disclosure, and the scope of the present disclosure cannot be limited thereto. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure here, those skilled in the art will easily think of the implementation scheme of the present disclosure. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the technical field not recorded in the present disclosure. The description and examples are regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

[0145] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0146] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-frequency, low-noise tuned amplifier system, characterized in that: include: Controls isolated drive circuits, controllable attenuator banks, single tuned filters and low noise amplifiers; The control signal is connected to the input end of the control isolation drive circuit, and the first output end of the control isolation drive circuit is connected to the first input end of the single tuned filter through a controllable attenuator group, so as to obtain an attenuated control signal after performing signal attenuation on the first control signal; the second output end of the control isolation drive circuit is connected to the second input end of the single tuned filter; The single tuned filter is used to isolate and gain-amplify the attenuated control signal, and to gain-amplify the second control signal to obtain a tuned output signal; The input end of the low noise amplifier is connected to the output end of the single tuned filter for amplifying the tuned output signal.

2. The low-frequency, low-noise tuned amplifier system according to claim 1, characterized in that: The single tuned filter comprises: a tuning transformer group, a compensation capacitor group and a tuning capacitor group; The tuning transformer group includes a first relay group, which is used to control the on / off state of relays in the first relay group to select the tuning frequency and perform gain amplification; The tuning capacitor group includes a binary capacitor group and a second relay group, which is used to control the on / off state of the relays in the second relay group to control the binary capacitor group to cooperate with the tuning transformer group to select the tuning frequency; The compensation capacitor group is used to compensate for parasitic capacitance and inductance in the circuit.

3. The low-frequency, low-noise tuned amplifier system according to claim 2, characterized in that: The first relay group includes at least two groups of relay branches connected in parallel, and the relay branches include a transformer and three relays.

4. The low-frequency, low-noise tuned amplifier system according to claim 3, characterized in that: The transformer comprises an adjusting rod, and the adjusting rod is used to adjust the inductance.

5. The low-frequency, low-noise tuned amplifier system according to claim 2, characterized in that: The compensation capacitor group device includes at least two groups of parallel capacitance branches, and the capacitance branches include fixed capacitors and adjustable capacitors; The fixed capacitor is used to compensate for parasitic capacitance and inductance in the circuit; The adjustable capacitor is used to fine-tune the compensation capacitance.

6. The low-frequency, low-noise tuned amplifier system according to claim 1, characterized in that: The controllable attenuator group comprises: at least one set of attenuators and relays connected in series; The relay is connected to the first output terminal of the control isolation drive circuit and is used to select the attenuation frequency; The attenuator is connected to the first input end of the single-tuned filter and is used for performing signal attenuation on the first control signal to obtain an attenuated control signal.

7. The low-frequency, low-noise tuned amplifier system according to claim 1, characterized in that: The low noise amplifier is a common-gate common-source low noise amplifier circuit.

8. The low-frequency, low-noise tuned amplifier system according to claim 1, characterized in that: The control isolation driving circuit includes an AC photoelectric coupling chip and a driving chip; The AC photoelectric coupling chip is used to isolate the control signal and generate an isolated control signal. The driving chip is used to receive the isolation control signal and generate a relay control signal.

9. The low-frequency, low-noise tuned amplifier system according to claim 1, characterized in that: Also includes: Power supply voltage stabilizing circuit; The power supply voltage stabilization circuit is connected to the isolation drive circuit to maintain the stability of the power supply voltage and suppress the harmonic interference introduced by the power supply.

10. The low-frequency, low-noise tuned amplifier system according to claim 9, characterized in that: The power supply voltage stabilization circuit comprises: a parallel buck linear voltage stabilizer, a filter capacitor group and a resistor which are connected in parallel with each other.

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