CN112327029A

CN112327029A - Oscilloscope simulation channel device based on double impedance transformation network

Info

Publication number: CN112327029A
Application number: CN202011254101.3A
Authority: CN
Inventors: 周立功; 杜少平
Original assignee: Guangzhou Zhiyuan Electronics Co Ltd
Current assignee: Guangzhou Zhiyuan Electronics Co Ltd
Priority date: 2020-11-11
Filing date: 2020-11-11
Publication date: 2021-02-05

Abstract

The embodiment of the application discloses oscilloscope simulation channel device based on double impedance transformation network, the device includes: the first mechanical relay is connected with the seventh mechanical relay, the second mechanical relay is connected with the input end of the first attenuation network, the output end of the first attenuation network is connected with the third mechanical relay and the fourth mechanical relay, the third mechanical relay is connected with the fifth mechanical relay, the fourth mechanical relay is connected with the input end of the second attenuation network, the output end of the second attenuation network is connected with the sixth mechanical relay, and the fifth mechanical relay and the sixth mechanical relay are connected with the eighth mechanical relay; the seventh mechanical relay and the eighth mechanical relay are connected with the positive input end of the first operational amplifier, the output end of the first operational amplifier is connected with the input end of the first impedance transformation network and the input end of the second impedance transformation network, and the output end of the first impedance transformation network and the output end of the second impedance transformation network are connected with the analog switch.

Description

Oscilloscope simulation channel device based on double impedance transformation network

Technical Field

The embodiment of the application relates to the technical field of analog channels, in particular to an oscilloscope analog channel device based on a double impedance transformation network.

Background

In an oscilloscope or the like, an analog channel has the functions of signal matching, attenuation, amplification and the like, and is used for converting an input signal into a voltage signal suitable for ADC conversion. The measurement gear of the oscilloscope is wide, and ranges from 2mV/div to 10V/div. The difference is 5000 times. The oscilloscope generally has two stages of passive attenuation networks to properly attenuate signals, so as to realize such a large measurement gear.

In a traditional analog channel structure, a switch adopts a mechanical relay, and the mechanical relay has the following problems: 1) mechanical relays have a large capacitance, typically one switch has a capacitance of 1.5 pF. If the oscilloscope is in the low voltage gear, the signal need can reach impedance transformation network through four switches, has increased 6 pF's electric capacity in other words, to the input capacitance of the ordinary tens pF of oscilloscope, the influence of 6 pF's electric capacity to the oscilloscope can not vary in a small amount. 2) The switch pieces of the mechanical relay are long in length, each having a length of 1 cm. If the oscilloscope is in a small voltage gear, signals can reach the impedance transformation network only through four switches, the length of 4 switches is 4cm, the VSWR of the oscilloscope with the bandwidth of 500MHz and higher can be seriously degraded due to the transmission line, and meanwhile, the bandwidth can be influenced. 3) The mechanical structure of the mechanical relay can cause the mechanical relay to have serious antenna effect, noise is increased, and the operation condition of a simulation channel at a small voltage gear is influenced. 4) The isolation of the mechanical relay to high frequency is not enough, and is only about 27dB at 500MHz, so that when the attenuation multiple is more than or close to 26dB (20 times), partial signals can leak from the input end, and the signals are overshot and uneven.

But because the oscilloscope must ensure that no gear is damaged under mains input, a mechanical relay must be used. Therefore, the structure of the analog channel needs to be modified to reduce the influence of the mechanical relay on the working state of the oscilloscope.

Disclosure of Invention

The embodiment of the application provides an oscilloscope simulation channel device based on a double impedance transformation network, which can reduce the influence of a mechanical relay on the working state of an oscilloscope and improve the reliability of the oscilloscope.

In a first aspect, an embodiment of the present application provides an oscilloscope analog channel apparatus based on a double impedance transformation network, including: first to eighth mechanical relay, first decay network, second decay network, first impedance transformation network, second impedance transformation network, first operational amplifier and analog switch, wherein:

the signal input end is connected with a first mechanical relay and a second mechanical relay, and the first mechanical relay is connected with a seventh mechanical relay;

the second mechanical relay is connected with the input end of the first attenuation network, the output end of the first attenuation network is connected with a third mechanical relay and a fourth mechanical relay, the third mechanical relay is connected with a fifth mechanical relay, the fourth mechanical relay is connected with the input end of the second attenuation network, the output end of the second attenuation network is connected with a sixth mechanical relay, and the fifth mechanical relay and the sixth mechanical relay are connected with an eighth mechanical relay;

the seventh mechanical relay and the eighth mechanical relay are connected with a positive input end of the first operational amplifier, an output end of the first operational amplifier is connected with an input end of the first impedance transformation network and an input end of the second impedance transformation network, and an output end of the first impedance transformation network and an output end of the second impedance transformation network are connected with a signal output end through the analog switch.

Further, the first mechanical relay is connected with the input end of the first impedance transformation network through a first capacitor, and the fifth mechanical relay and the sixth mechanical relay are connected with the input end of the second impedance transformation network through a second capacitor; wherein a high frequency component of the ac signal input to the signal input terminal propagates backward through the first mechanical relay and the first impedance transforming network, or propagates backward through the fifth mechanical relay or the sixth mechanical relay and the second impedance transforming network, and a low frequency component of the ac signal input to the signal input terminal propagates backward through the seventh mechanical relay or the eighth mechanical relay and the first operational amplifier.

Further, a first resistor is configured between the first mechanical relay and the seventh mechanical relay, a positive input end of the first operational amplifier is grounded through a second resistor, and a resistance value of the first resistor is 700K Ω to 1M Ω; when the oscilloscope works in a low-voltage gear, the first mechanical relay is switched on, the second mechanical relay is switched off, the seventh mechanical relay is switched on, the eighth mechanical relay is switched off, the analog switch between the output end of the first impedance transformation network and the signal output end is switched on, and the analog switch between the output end of the second impedance transformation network and the signal output end is switched off.

Further, a third resistor is arranged between the fifth mechanical relay and the eighth mechanical relay; when the oscilloscope works at a high-voltage gear, the first mechanical relay is switched off, the second mechanical relay is switched on, the third mechanical relay and the fifth mechanical relay are switched on, the fourth mechanical relay and the sixth mechanical relay are switched off, or the fourth mechanical relay and the sixth mechanical relay are switched on, the third mechanical relay and the fifth mechanical relay are switched off, the seventh mechanical relay is switched off, the eighth mechanical relay is switched on, the analog switch between the output end of the first impedance transformation network and the signal output end is switched off, and the analog switch between the output end of the second impedance transformation network and the signal output end is switched on.

Furthermore, the negative input end of the first operational amplifier and the output end of the first operational amplifier are grounded through a first digital potentiometer, the negative input end of the first operational amplifier is connected with a direct current bias signal adjusting end through a second digital potentiometer, and the direct current bias signal adjusting end is connected with the signal output end through the second digital potentiometer and a fourth resistor.

Further, the device further comprises a control module, wherein the control module is connected with the analog switch, the control module is connected with a first enabling port of the first impedance transformation network, and the control module is used for outputting a control signal, controlling the gating mode of the analog switch and controlling the working state of the first impedance transformation network.

Further, the control module is connected to a second enable port of the second impedance transformation network through an inverter, and the control module is configured to output a control signal to control a working state of the second impedance transformation network.

Further, the analog switch includes a radio frequency switch, a voltage follower circuit and a circuit for controlling the radio frequency switch to be turned on, wherein:

the first impedance transformation network is connected with a first signal Input end of the radio frequency switch through a THRU Input port of the analog switch, the second impedance transformation network is connected with a second signal Input end of the radio frequency switch through an ATTen Input port of the analog switch, an RFC port of the radio frequency switch is connected with the voltage following circuit and the signal output end, the control module is connected with the control radio frequency switch conducting circuit, and the control radio frequency switch conducting circuit is connected with a control signal Input end of the radio frequency switch;

the voltage follower circuit is used for generating a power supply MMIC _ P and a power supply MMIC _ N which follow the direct current and low-frequency voltage changes; and the control radio frequency switch conducting circuit is used for sending a switch signal to the radio frequency switch according to the control signal.

Further, the voltage follower circuit includes a second operational amplifier, a third operational amplifier, first to fourth transistors, fifth to seventh resistors, and a third capacitor, wherein:

the RFC port of the radio frequency switch is connected with a fifth resistor, the fifth resistor is connected with the third capacitor and the positive input end of the second operational amplifier, the third capacitor is grounded, the output end of the second operational amplifier is connected with the base electrode of the first triode and the base electrode of the second triode, the emitter of the first triode and the emitter of the second triode are connected with the power supply MMIC _ P, the negative input end of the second operational amplifier and the sixth resistor, the sixth resistor is connected with the seventh resistor and the positive input end of the third operational amplifier, the output end of the third operational amplifier is connected with the base electrode of the third triode and the base electrode of the fourth triode, an emitter electrode of the third triode and an emitter electrode of the fourth triode are connected with the power supply MMIC _ N and a negative electrode input end of the third operational amplifier;

the collector electrodes of the first triode and the third triode are connected with a positive-voltage power supply, the collector electrodes of the second triode and the fourth triode are connected with a negative-voltage power supply, and the seventh resistor is connected with the negative-voltage power supply;

wherein a differential mode voltage between the power supply MMIC _ P and the power supply MMIC _ N is constant.

Further, the rf switch turn-on control circuit includes a first diode, a second diode, eighth to twelfth resistors, a fourth operational amplifier, a fifth operational amplifier, and a fourth capacitor, wherein:

the control module is connected with the eighth resistor, the eighth resistor is connected with the ninth resistor, the negative input end of the fourth operational amplifier and the positive input end of the fifth operational amplifier, the ninth resistor is connected with the power MMIC _ N, the first diode and the second diode are connected in parallel, the positive electrode of the first diode and the negative electrode of the second diode are grounded, the negative electrode of the first diode and the positive electrode of the second diode are connected with the tenth resistor, the eleventh resistor, the positive input end of the fourth operational amplifier and the negative input end of the fifth operational amplifier, the tenth resistor is connected with the power MMIC _ P, the eleventh resistor is connected with the power MMIC _ N, the output end of the fourth operational amplifier is connected with the first control signal input end of the radio frequency switch, and the output end of the fifth operational amplifier is connected with the second control signal input end of the radio frequency switch, the signal ground of the radio frequency switch is connected with the twelfth resistor and the fourth capacitor, the fourth capacitor is grounded, and the twelfth resistor is connected with the power supply MMIC _ P;

and the positive power supply end of the fourth operational amplifier and the positive power supply end of the fifth operational amplifier are connected with the power supply MMIC _ P, and the negative power supply end of the fourth operational amplifier and the negative power supply end of the fifth operational amplifier are connected with the power supply MMIC _ N.

The signal input end of the first mechanical relay is connected with the second mechanical relay, and the first mechanical relay is connected with the seventh mechanical relay; the second mechanical relay is connected with the input end of the first attenuation network, the output end of the first attenuation network is connected with a third mechanical relay and a fourth mechanical relay, the third mechanical relay is connected with a fifth mechanical relay, the fourth mechanical relay is connected with the input end of the second attenuation network, the output end of the second attenuation network is connected with a sixth mechanical relay, and the fifth mechanical relay and the sixth mechanical relay are connected with an eighth mechanical relay; the seventh mechanical relay and the eighth mechanical relay are connected with a positive input end of the first operational amplifier, an output end of the first operational amplifier is connected with an input end of the first impedance transformation network and an input end of the second impedance transformation network, and an output end of the first impedance transformation network and an output end of the second impedance transformation network are connected with a signal output end through the analog switch. Through the technical means, the two impedance transformation networks are adopted to separate and process the direct-through signals and the attenuated signals, and the adverse effect brought by the mechanical relay is reduced to the maximum extent.

Drawings

Fig. 1 is a schematic structural diagram of an oscilloscope analog channel device of a double impedance transformation network according to an embodiment of the present application;

FIG. 2 is a schematic diagram of an analog switch according to an embodiment of the present disclosure;

in the figure, 11 is a signal input terminal, 12 is a control module, 13 is a signal output terminal, 14 is a dc bias signal adjustment terminal, 21 is an rf switch, 22 is a control rf switch conducting circuit, 23 is a voltage follower circuit, K1 is a first mechanical relay, K2 is a second mechanical relay, K3 is a third mechanical relay, K4 is a fourth mechanical relay, K5 is a fifth mechanical relay, K6 is a sixth mechanical relay, K7 is a seventh mechanical relay, K8 is an eighth mechanical relay, K9 is an analog switch, R1 is a first resistor, R2 is a second resistor, R3 is a third resistor, R4 is a fourth resistor, R5 is a fifth resistor, R6 is a sixth resistor, R7 is a seventh resistor, R8 is an eighth resistor, R9 is a ninth resistor, R10 is a tenth resistor, R11 is an eleventh resistor, R11 is a twelfth resistor, R12 is a twelfth resistor, R599 is a digital potentiometer, c1 is a first capacitor, C2 is a second capacitor, C3 is a third capacitor, C4 is a fourth capacitor, D1 is a first diode, D2 is a second diode, Q1 is a first triode, Q2 is a second triode, Q3 is a third triode, Q4 is a fourth triode, MMIC _ P is a power supply MMIC _ P, MMIC _ N is a power supply MMIC _ N, U0 is an inverter, U1 is a first operational amplifier, U2 is a second operational amplifier, U3 is a third operational amplifier, U4 is a fourth operational amplifier, U5 is a fifth operational amplifier, U6 is a sixth operational amplifier, ATT1 is a first attenuation network, ATT2 is a second attenuation network, BUF1 is a first impedance transformation network, BUF2 is a second impedance transformation network, VCC is a positive voltage power supply, and VEE is a negative voltage supply.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, specific embodiments of the present application will be described in detail with reference to the accompanying drawings. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not limiting of the application. It should be further noted that, for the convenience of description, only some but not all of the relevant portions of the present application are shown in the drawings. Before discussing exemplary embodiments in more detail, it should be noted that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although a flowchart may describe the operations (or steps) as a sequential process, many of the operations can be performed in parallel, concurrently or simultaneously. In addition, the order of the operations may be re-arranged. The process may be terminated when its operations are completed, but may have additional steps not included in the figure. The processes may correspond to methods, functions, procedures, subroutines, and the like.

The oscilloscope simulation channel device of the double impedance transformation network aims to be connected with a first mechanical relay and a second mechanical relay through signal input ends, and the first mechanical relay is connected with a seventh mechanical relay; the second mechanical relay is connected with the input end of the first attenuation network, the output end of the first attenuation network is connected with a third mechanical relay and a fourth mechanical relay, the third mechanical relay is connected with a fifth mechanical relay, the fourth mechanical relay is connected with the input end of the second attenuation network, the output end of the second attenuation network is connected with a sixth mechanical relay, and the fifth mechanical relay and the sixth mechanical relay are connected with an eighth mechanical relay; the seventh mechanical relay and the eighth mechanical relay are connected with a positive input end of the first operational amplifier, an output end of the first operational amplifier is connected with an input end of the first impedance transformation network and an input end of the second impedance transformation network, and an output end of the first impedance transformation network and an output end of the second impedance transformation network are connected with a signal output end through the analog switch. For traditional oscilloscope simulation channel device, the signal need can reach impedance transformation network through four switches, has increased 6 pF's electric capacity in other words, to the input capacitance of the general tens pF of oscilloscope, the influence of 6 pF's electric capacity to oscilloscope can not vary in a small amount. Based on this, the oscilloscope analog channel device of the double impedance transformation network provided by the embodiment of the application. The problem of mechanical relay to oscilloscope operating condition influence is solved.

The first embodiment is as follows:

fig. 1 is a schematic structural diagram of an oscilloscope analog channel apparatus of a double impedance transformation network according to an embodiment of the present application. Referring to fig. 1, an oscilloscope analog channel apparatus of a double impedance transformation network includes: first to eighth mechanical relays, a first attenuation network ATT1, a second attenuation network ATT2, a first impedance transformation network BUF1, a second impedance transformation network BUF2, a first operational amplifier U1 and an analog switch K9, wherein:

the signal input end 11 is connected with a first mechanical relay K1 and a second mechanical relay K2, and the first mechanical relay K1 is connected with a seventh mechanical relay K7; the second mechanical relay K2 is connected with the input end of the first attenuation network ATT1, the output end of the first attenuation network ATT1 is connected with a third mechanical relay K3 and a fourth mechanical relay K4, the third mechanical relay K3 is connected with a fifth mechanical relay K5, the fourth mechanical relay K4 is connected with the input end of the second attenuation network ATT2, the output end of the second attenuation network ATT2 is connected with the sixth mechanical relay K6, and the fifth mechanical relay K5 and the sixth mechanical relay K6 are connected with the eighth mechanical relay K8; the seventh mechanical relay K7 and the eighth mechanical relay K8 are connected with a positive input end of the first operational amplifier U1, an output end of the first operational amplifier U1 is connected with an input end of the first impedance transformation network BUF1 and an input end of the second impedance transformation network BUF2, and an output end of the first impedance transformation network BUF1 and an output end of the second impedance transformation network BUF2 are connected with a signal output end 13 through the analog switch K9.

Specifically, in one embodiment, the first mechanical relay K1 is connected to the input terminal of the first impedance transformation network BUF1 through a first capacitor C1, and the fifth mechanical relay K5 and the sixth mechanical relay K6 are connected to the input terminal of the second impedance transformation network BUF2 through a second capacitor C2; wherein a high frequency component of the ac signal inputted from the signal input terminal 11 is propagated backward through the first mechanical relay K1 and the first impedance transforming network BUF1, or through the fifth mechanical relay K5 or the sixth mechanical relay K6 and the second impedance transforming network BUF2, and a low frequency component of the ac signal inputted from the signal input terminal 11 or the dc signal is propagated backward through the seventh mechanical relay K7 or the eighth mechanical relay K8 and the first operational amplifier U1.

Illustratively, after the ac signal and the dc signal are transmitted from the signal input terminal 11, since the first capacitor C1 and the second capacitor C2 isolate the low frequency component of the ac signal from the dc signal, only the high frequency component of the ac signal propagates directly back through the first capacitor C1 or the second capacitor C2 and the first impedance transforming network BUF1 or the second impedance transforming network BUF 2. The low frequency component of the AC signal and the DC signal are transmitted backward from the first impedance transforming network BUF1 or the second impedance transforming network BUF2 after passing through the first operational amplifier U1. Through setting up first electric capacity C1 and second electric capacity C2, keep apart the high frequency component of alternating current signal and the low frequency component and the direct current signal of alternating current signal, carry out signal propagation by different propagation channel, guaranteed low frequency precision and high frequency bandwidth performance simultaneously.

Specifically, in one embodiment, a first resistor R1 is disposed between the first mechanical relay K1 and the seventh mechanical relay K7, a positive input terminal of the first operational amplifier U1 is grounded through a second resistor R2, and a resistance value of the first resistor R1 is 700K Ω to 1M Ω; when the oscilloscope works in a low-voltage gear, the first mechanical relay K1 is switched on, the second mechanical relay K2 is switched off, the seventh mechanical relay K7 is switched on, the eighth mechanical relay K8 is switched off, the analog switch K9 between the output end of the first impedance transformation network BUF1 and the signal output end 13 is switched on, and the analog switch K9 between the output end of the second impedance transformation network BUF2 and the signal output end 13 is switched off.

Illustratively, when the oscilloscope operates in a small-voltage gear, the first mechanical relay K1 is turned on, the second mechanical relay K2 is turned off, the seventh mechanical relay K7 is turned on, the eighth mechanical relay K8 is turned off, the seventh mechanical relay K7 connects the first resistor R1 and the second resistor R2 together, and the analog switch K9 connects the output end of the first impedance transformation network BUF1 to the signal output end 13. At this time, the signal input by the signal input terminal 11 is transmitted to the impedance transformation network composed of the first operational amplifier U1 and the first impedance transformation network BUF1 only through the first mechanical relay K1 and the seventh mechanical relay K7, and since the resistance value of the first resistor R1 is high and is between 700K Ω and 1M Ω, the capacitance of the seventh mechanical relay K7 can be ignored, and the impedance transformation network has good reverse isolation, and the circuit behind the impedance transformation network cannot be monitored by the signal input terminal 11. Based on this, the capacitance generated by only one mechanical relay is increased from the signal input end 11 to the signal output end 13, which is reduced by about 4.5pF compared with the traditional oscilloscope analog channel device, and the VSWR and the introduced noise are greatly reduced because of less mechanical relay switches.

Specifically, in one embodiment, a third resistor R3 is arranged between the fifth mechanical relay K5 and the sixth mechanical relay K6 and the eighth mechanical relay K8; when the oscilloscope works in a high-voltage gear, the first mechanical relay K1 is switched off, the second mechanical relay K2 is switched on, the third mechanical relay K3 and the fifth mechanical relay K5 are switched on, the fourth mechanical relay K4 and the sixth mechanical relay K6 are switched off, or the fourth mechanical relay K4 and the sixth mechanical relay K6 are switched on, the third mechanical relay K3 and the fifth mechanical relay K5 are switched off, the seventh mechanical relay K7 is switched off, the eighth mechanical relay K8 is switched on, the analog switch K9 between the output end of the first impedance transformation network BUF1 and the signal output end 13 is switched off, and the analog switch K9 between the output end of the second impedance transformation network BUF2 and the signal output end 13 is switched on.

Illustratively, when the oscilloscope operates in a large voltage gear, the first mechanical relay K1 is switched off, the second mechanical relay K2 is switched on, the seventh mechanical relay K7 is switched off, the eighth mechanical relay K8 is switched on, the eighth mechanical relay K8 connects the third resistor R3 and the second resistor R2 together, and the analog switch K9 connects the output end of the second impedance transformation network BUF2 to the signal output end 13. At this time, the signal input by the signal input terminal 11 enters the attenuation network only after passing through the second mechanical relay K2, and the large attenuation multiple of the attenuation network can greatly reduce the capacitance and VSWR of the subsequent stage, so that the small capacitance and the small VSWR can be realized under the large-voltage gear.

Specifically, in one embodiment, the negative input terminal of the first operational amplifier U1 and the output terminal of the first operational amplifier U1 are grounded through a first digital potentiometer R1A, the negative input terminal of the first operational amplifier U1 is connected to the dc bias signal adjusting terminal 14 through a second digital potentiometer R2A, and the dc bias signal adjusting terminal 14 is connected to the signal output terminal 13 through the second digital potentiometer R2A and a fourth resistor R4.

Illustratively, since the high-frequency component of the alternating current signal is different from the low-frequency component of the alternating current signal and the transmission channel of the direct current signal, and the channel gain is also different, in order to ensure the consistency of the direct current, the low-frequency and the high-frequency gains, by connecting a first digital potentiometer R1A in parallel to the ground in the feedback loop of the first operational amplifier circuit U1, and connecting a second digital potentiometer R2A in series between the negative input end of the first operational amplifier U1 and the direct current bias signal adjusting end 14, the gain coefficient of the first operational amplifier U1 is adjusted by changing the resistance values of the first digital potentiometer R1A and the second digital potentiometer R2A, so as to achieve the consistency of the direct current, the low-frequency and the high-frequency gains, thereby improving the measurement accuracy.

Specifically, in an embodiment, the apparatus further includes a control module 12, the control module 12 is connected to the analog switch K9, the control module 12 is connected to a first enable port of the first impedance transforming network BUF1, and the control module 12 is configured to output a control signal, control a gating mode of the analog switch K9, and control an operating state of the first impedance transforming network BUF 1.

Specifically, in one embodiment, the control module 12 is connected to the second enable port of the second impedance transforming network BUF2 through an inverter U0, and the control module 12 is configured to output a control signal to control the operating state of the second impedance transforming network BUF 2.

Illustratively, the control signal output end of the control module 12 is connected with the analog switch K9 and the first impedance transformation network BUF1, the control signal output end of the control module 12 is connected with the second impedance transformation network BUF2 through the inverter U0, when the control signal output by the control module 12 is at a high level, the analog switch K9 between the output end of the first impedance transformation network BUF1 and the signal output end is turned on, the analog switch K9 between the output end of the second impedance transformation network BUF2 and the signal output end 13 is turned off, the first impedance transformation network BUF1 is turned on, and the second impedance transformation network BUF2 is turned off. When the control signal output by the control module 12 is at a low level, the analog switch K9 between the output end of the first impedance transformation network BUF1 and the signal output end 13 is turned off, the analog switch K9 between the output end of the second impedance transformation network BUF2 and the signal output end 13 is turned on, the first impedance transformation network BUF1 is turned off, and the second impedance transformation network BUF2 is turned on. Through the inverter U0, the working states of three devices are controlled by one control signal at the same time, and the two impedance transformation networks are in a power-off state when not used through the control signal, so that the isolation between the through network and the attenuation network is improved.

Specifically, referring to fig. 2, fig. 2 is a schematic structural diagram of an analog switch K9 according to an embodiment of the present application. The analog switch K9 includes an rf switch 21, a voltage follower circuit 23 and a control rf switch conducting circuit 22, wherein:

the first impedance transformation network BUF1 is connected to the first signal Input terminal of the radio frequency switch 21 through the THRU Input port of the analog switch K9, the second impedance transformation network BUF2 is connected to the second signal Input terminal of the radio frequency switch 21 through the ATTen Input port of the analog switch K9, the RFC port of the radio frequency switch 21 is connected to the voltage follower circuit 23 and the signal output terminal 13, the control module 12 is connected to the control radio frequency switch turn-on circuit 22, and the control radio frequency switch turn-on circuit 22 is connected to the control signal Input terminal of the radio frequency switch 21; the voltage follower circuit 23 is configured to generate a power MMIC _ P and a power MMIC _ N that follow the dc and low-frequency voltage variations; the control rf switch conducting circuit 22 is configured to send a switch signal to the rf switch 21 according to the control signal.

Illustratively, a signal transmitted by the first impedance transformation network BUF1 is Input into the radio frequency switch 21 through the THRU Input port, or a signal transmitted by the second impedance transformation network BUF2 is Input into the radio frequency switch 21 through the ATTen Input port, and is selected by the radio frequency switch 21, and the signal is transmitted to the RFC port of the radio frequency switch 21 and finally transmitted to the signal output terminal 13. Since the rf switch 21 cannot directly input an excessively high dc level, which obviously does not meet the usage requirement of the oscilloscope, an analog switch K9 with a function of dynamically adjusting the control level according to the signal dc level is formed by the voltage follower circuit 23 and the control rf switch conducting circuit 22.

Specifically, in one embodiment, the voltage follower circuit 23 includes a second operational amplifier U2, a third operational amplifier U3, first to fourth transistors, fifth to seventh resistors, and a third capacitor C3, wherein:

the RFC port of the radio frequency switch 21 is connected with a fifth resistor R5, the fifth resistor R5 is connected with the third capacitor C3 and the positive input end of a second operational amplifier U2, the third capacitor C3 is grounded, the output end of the second operational amplifier U3 is connected with the base electrode of the first triode Q1 and the base electrode of the second triode Q2, the emitter of the first transistor Q1 and the emitter of the second transistor Q2 are connected to the power MMIC _ P, the negative input of the second operational amplifier U2 and the sixth resistor R6, the sixth resistor R6 is connected to the seventh resistor R7 and the positive input terminal of the third operational amplifier U3, the output end of the third operational amplifier U3 is connected with the base electrode of the third triode Q3 and the base electrode of the fourth triode Q4, the emitter electrode of the third triode Q3 and the emitter electrode of the fourth triode Q4 are connected with the negative input end of the power supply MMIC _ N and the third operational amplifier U3; the collectors of the first triode Q1 and the third triode Q3 are connected with a positive voltage power supply VCC, the collectors of the second triode Q2 and the fourth triode Q1 are connected with a negative voltage power supply VEE, and the seventh resistor R7 is connected with the negative voltage power supply VEE; wherein a differential mode voltage between the power supply MMIC _ P and the power supply MMIC _ N is constant.

Specifically, in one embodiment, the rf switch on control circuit 22 includes a first diode D1, a second diode D2, eighth to twelfth resistors, a fourth operational amplifier U4, a fifth operational amplifier U5, and a fourth capacitor C4, wherein:

the control module 12 is connected to the eighth resistor R8, the eighth resistor R8 is connected to the ninth resistor R9, the negative input terminal of the fourth operational amplifier U4 and the positive input terminal of the fifth operational amplifier U5, the ninth resistor R9 is connected to the MMIC _ N, the first diode D1 and the second diode D2 are connected in parallel, the positive electrode of the first diode D1 and the negative electrode of the second diode D2 are grounded, the negative electrode of the first diode D1 and the positive electrode of the second diode D2 are connected to the tenth resistor R10, the eleventh resistor R11, the positive input terminal of the fourth operational amplifier U4 and the negative input terminal of the fifth operational amplifier U5, the tenth resistor R10 is connected to the MMIC _ P, the eleventh resistor R11 is connected to the power MMIC _ N, the output terminal of the fourth operational amplifier U4 is connected to the first control signal input terminal of the radio frequency switch 21, the output end of the fifth operational amplifier U5 is connected to the second control signal input end of the radio frequency switch 21, the signal ground of the radio frequency switch 21 is connected to the twelfth resistor R12 and the fourth capacitor C4, the fourth capacitor is connected to the ground C4, and the twelfth resistor R12 is connected to the power supply MMIC _ P; the positive power supply end of the fourth operational amplifier U4 and the positive power supply end of the fifth operational amplifier U5 are connected to the power supply MMIC _ P, and the negative power supply end of the fourth operational amplifier U4 and the negative power supply end of the fifth operational amplifier U5 are connected to the power supply MMIC _ N.

Illustratively, after the signal is output from the rf switch 21, the signal is sampled by the fifth resistor R5, and since the resistance value of the fifth resistor R5 is high and is between 50K and 500K, the quality of the signal is not affected. The signal passes through a low-pass filter consisting of a fifth resistor R5 and a third capacitor C3, high-frequency signals are filtered out, only direct current and partial low-frequency signals are reserved, and the cut-off frequency is determined by the fifth resistor R5 and the third capacitor C3. The dc and low frequency signals extracted through the fifth resistor R5 and the third capacitor C3 form a power MMIC _ P that varies with the voltage variation of the dc and low frequency signals through a buffer network formed by the second operational amplifier U2, the first transistor Q1, and the second transistor Q2. And the power supply MMIC _ P passes through the sixth resistor R6 and the seventh resistor R7 and then forms a first voltage division network with the negative voltage power supply VEE. The voltage generated by the first voltage division network passes through a buffer network formed by the third operational amplifier U3, the third triode Q3 and the fourth triode Q4 to form a power supply MMIC _ N which always keeps a fixed voltage difference with the power supply MMIC _ P, and the voltage difference is determined by the sixth resistor R6, the seventh resistor R7 and the negative voltage power supply VEE. At this time, the power supply MMIC _ P and the power supply MMIC _ N have fixed differential mode voltages, and have the same common mode voltage as the direct current and low frequency signal voltages of the signal output terminal 13. The power supply MMIC _ P serves as a positive power supply for the fourth operational amplifier U4 and the fifth operational amplifier U5, and the power supply MMIC _ N serves as a negative power supply for the fourth operational amplifier U4 and the fifth operational amplifier U5.

Further, the control signal input by the control module 12 passes through the eighth resistor R8 and the ninth resistor R9, and then forms a second voltage division network with the power MMIC _ N, and a voltage generated by the second voltage division network is input to the negative input terminal of the fourth operational amplifier U4 and the positive input terminal of the fifth operational amplifier U5. After passing through a tenth resistor R10 and an eleventh resistor R11, the power supply MMIC _ P and the power supply MMIC _ N form a third voltage division network, and the voltage generated by the third voltage division network is clamped by a first diode D1 and a second diode D2 to be about +/-0.7V. The voltage generated by the voltage divider network is then input to the positive input terminal of the fourth operational amplifier U4 and the negative input terminal of the fifth operational amplifier U5. The output end of the fourth operational amplifier U4 is connected to the first control signal input end of the RF switch 21, and the output end of the fifth operational amplifier U5 is connected to the second control signal input end of the RF switch 21.

Specifically, the fourth operational amplifier U4 and the fifth operational amplifier U5 are mainly used for comparing the voltages of the negative input terminal and the positive input terminal, that is, comparing the voltage generated by the second voltage division network with the voltage generated by the third voltage division network. When the control signal is a high-level signal, the voltage of the negative input end of the fourth operational amplifier U4 is greater than the voltage of the positive input end, and the fourth operational amplifier U4 sends a low-level control signal to the second control signal input end of the radio frequency switch 21, so that the analog switch K9 between the output end of the second impedance transformation network BUF2 and the signal output end 13 is turned off; the voltage of the positive Input end of the fifth operational amplifier U5 is greater than the voltage of the negative Input end, the fifth operational amplifier U5 sends a high-level control signal to the first control signal Input end of the radio frequency switch 21, since the positive power supply and the negative power supply of the fifth operational amplifier U5 are the power supply MMIC _ P and the power supply MMIC _ N, respectively, the difference between the power supply MMIC _ P and the power supply MMIC _ N is greater than the power supply MMIC _ P, that is, the high-level control signal voltage output by the fifth operational amplifier U5 is greater than the power supply MMIC _ P, and the voltage Input by the THRU Input port is around the power supply MMIC _ P, based on which the analog switch K9 between the output end of the first impedance transformation network BUF1 and the signal output end 13 is turned on. Similarly, when the control signal is a low level signal, the voltage at the positive input terminal of the fourth operational amplifier U4 is greater than the voltage at the negative input terminal, and the fourth operational amplifier U4 sends a high level control signal to the second control signal input terminal of the rf switch 21, so that the analog switch K9 between the output terminal of the second impedance transforming network BUF2 and the signal output terminal 13 is turned on. The voltage of the negative input end of the fifth operational amplifier U5 is greater than that of the positive input end, and the fifth operational amplifier U5 sends a low-level control signal to the first control signal input end of the radio frequency switch 21, so that the analog switch K9 between the output end of the first impedance transformation network BUF1 and the signal output end 13 is turned off. In this embodiment, the voltage follower circuit 23 and the rf switch on-state control circuit 22 are adopted to realize a following mechanism in which the voltage of the control signal of the rf switch 21 changes with the voltage of the signal input to the rf switch 21, so as to solve the problem that the rf switch 21 cannot input a large dc signal.

Further, the power supply MMIC _ P raises the level reference for the rf switch 21 by inputting the signal ground of the rf switch 21 through the twelfth resistor R12. And the signal ground of the radio frequency switch 21 is grounded through a fourth capacitor C4, and the fourth capacitor C4 provides a high-frequency low-resistance return path for the radio frequency switch 21.

In summary, the embodiment of the present application is connected to the first mechanical relay K1 and the second mechanical relay K2 through the signal input terminal 11, and the first mechanical relay K1 is connected to the seventh mechanical relay K7; the second mechanical relay K2 is connected with the input end of the first attenuation network ATT1, the output end of the first attenuation network ATT1 is connected with a third mechanical relay K3 and a fourth mechanical relay K4, the third mechanical relay K3 is connected with a fifth mechanical relay K5, the fourth mechanical relay K4 is connected with the input end of the second attenuation network ATT2, the output end of the second attenuation network ATT2 is connected with the sixth mechanical relay K6, and the fifth mechanical relay K5 and the sixth mechanical relay K6 are connected with the eighth mechanical relay K8; the seventh mechanical relay K7 and the eighth mechanical relay K8 are connected with a positive input end of the first operational amplifier U1, an output end of the first operational amplifier U1 is connected with an input end of the first impedance transformation network BUF1 and an input end of the second impedance transformation network BUF2, and an output end of the first impedance transformation network BUF1 and an output end of the second impedance transformation network BUF2 are connected with a signal output end 13 through the analog switch K9. Through the technical means, the two impedance transformation networks are adopted to separate and process the direct-through signals and the attenuated signals, and the adverse effect brought by the mechanical relay is reduced to the maximum extent.

The foregoing is considered as illustrative of the preferred embodiments of the invention and the technical principles employed. The present application is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present application has been described in more detail with reference to the above embodiments, the present application is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present application, and the scope of the present application is determined by the scope of the claims.

Claims

1. An oscilloscope simulation channel device based on a double impedance transformation network is characterized by comprising: first to eighth mechanical relay, first decay network, second decay network, first impedance transformation network, second impedance transformation network, first operational amplifier and analog switch, wherein:

2. The apparatus of claim 1, wherein the first mechanical relay is connected to the input of the first impedance transforming network by a first capacitance, and the fifth mechanical relay and the sixth mechanical relay are connected to the input of the second impedance transforming network by a second capacitance; wherein a high frequency component of the ac signal input to the signal input terminal propagates backward through the first mechanical relay and the first impedance transforming network, or propagates backward through the fifth mechanical relay or the sixth mechanical relay and the second impedance transforming network, and a low frequency component of the ac signal input to the signal input terminal propagates backward through the seventh mechanical relay or the eighth mechanical relay and the first operational amplifier.

3. The apparatus of claim 1, wherein a first resistor is disposed between the first mechanical relay and the seventh mechanical relay, the positive input terminal of the first operational amplifier is grounded through a second resistor, and a resistance value of the first resistor is 700K Ω to 1M Ω; when the oscilloscope works in a low-voltage gear, the first mechanical relay is switched on, the second mechanical relay is switched off, the seventh mechanical relay is switched on, the eighth mechanical relay is switched off, the analog switch between the output end of the first impedance transformation network and the signal output end is switched on, and the analog switch between the output end of the second impedance transformation network and the signal output end is switched off.

4. The apparatus of claim 3, wherein a third resistor is configured between the fifth and sixth mechanical relays and the eighth mechanical relay; when the oscilloscope works at a high-voltage gear, the first mechanical relay is switched off, the second mechanical relay is switched on, the third mechanical relay and the fifth mechanical relay are switched on, the fourth mechanical relay and the sixth mechanical relay are switched off, or the fourth mechanical relay and the sixth mechanical relay are switched on, the third mechanical relay and the fifth mechanical relay are switched off, the seventh mechanical relay is switched off, the eighth mechanical relay is switched on, the analog switch between the output end of the first impedance transformation network and the signal output end is switched off, and the analog switch between the output end of the second impedance transformation network and the signal output end is switched on.

5. The apparatus of claim 1, wherein the negative input terminal of the first operational amplifier and the output terminal of the first operational amplifier are grounded through a first digital potentiometer, the negative input terminal of the first operational amplifier is connected to a dc bias signal adjusting terminal through a second digital potentiometer, and the dc bias signal adjusting terminal is connected to the signal output terminal through the second digital potentiometer and a fourth resistor.

6. The apparatus of claim 2, further comprising a control module, wherein the control module is connected to the analog switch, the control module is connected to the first enable port of the first impedance transforming network, and the control module is configured to output a control signal to control a gating mode of the analog switch and control an operating state of the first impedance transforming network.

7. The apparatus of claim 6, wherein the control module is connected to the second enable port of the second impedance transforming network through an inverter, and the control module is configured to output a control signal to control the operating state of the second impedance transforming network.

8. The apparatus of claim 6, wherein the analog switch comprises an RF switch, a voltage follower circuit, and a control RF switch turn-on circuit, wherein:

9. The apparatus of claim 8, wherein the voltage follower circuit comprises a second operational amplifier, a third operational amplifier, first to fourth transistors, fifth to seventh resistors, and a third capacitor, wherein:

10. The apparatus of claim 8, wherein the control rf switch turn-on circuit comprises a first diode, a second diode, eighth to twelfth resistors, a fourth operational amplifier, a fifth operational amplifier, and a fourth capacitor, wherein: