Direct detection type high-sensitivity millimeter wave and terahertz radiometer and its working method

Abstract

The present invention relates to the technical field of millimeter-wave and terahertz direct detection radiometers, and provides a direct detection high-sensitivity millimeter-wave and terahertz radiometer and its working method, including a chopper switch, and an antenna, a first low-noise amplifier, and a second low-noise amplifier connected in sequence; the chopper switch is connected to the connection line between the first low-noise amplifier and the second low-noise amplifier, and is used to chop the millimeter-wave and terahertz signals amplified by the first low-noise amplifier. It not only has a small deterioration of the overall noise of the radiometer, but also can effectively suppress the noise impact brought by the devices after the chopper modulation circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of millimeter-wave and terahertz direct detection radiometers, and particularly relates to a direct detection high-sensitivity millimeter-wave and terahertz radiometer and its working method. Background Art

[0002] The statements in this part only provide background technologies related to the present invention, and do not necessarily constitute prior art.

[0003] In the electromagnetic spectrum, millimeter-wave and terahertz wave electromagnetic spectra are in the electromagnetic spectrum between microwaves and infrared rays. Due to their special spectral positions, millimeter-wave and terahertz waves simultaneously have the advantages of microwaves and light waves. Compared with microwaves, millimeter-wave and terahertz waves have higher frequencies and shorter wavelengths. Millimeter-wave and terahertz systems are more likely to obtain higher resolutions and larger information capacities. Compared with light waves, the stronger penetration ability enables millimeter-wave and terahertz waves to be applied in rainy and foggy weather, smoky battlefields and other extreme conditions. Millimeter-wave and terahertz waves have lower photon energies and can be applied to non-destructive detection of biological tissues. According to the blackbody theory, substances in nature can radiate millimeter-wave and terahertz "near-noise" signals. By detecting these "near-noise" signals, the observation of substances can be realized, and then it can be applied in fields such as meteorological remote sensing, environmental detection, and human body security inspection.

[0004] The millimeter-wave and terahertz radiometer itself does not emit energy outward. By improving its temperature sensitivity index, the detection of millimeter-wave and terahertz "near-noise" signals radiated by substances can be realized, and then the observation of substances can be realized. Therefore, the temperature sensitivity index is the core technical index of the millimeter-wave and terahertz radiometer, and there are many limitations and technical bottlenecks in its improvement. The direct detection millimeter-wave and terahertz radiometer is one of the categories. It uses millimeter-wave and terahertz low-noise amplifiers, detectors, integrating amplifiers, etc. to achieve full-power detection. It has technical characteristics such as simple structure and easy integration of multiple channels, and has received extensive attention from experts and scholars in the field, and certain progress has been made and certain applications have been obtained.

[0005] According to the working principle of traditional direct detection radiometers, the temperature sensitivity index of the radiometer mainly depends on the technical indexes of core devices such as the noise figure, gain stability, bandwidth, and the integration time. When the technical indexes of the core devices are determined, the longer the integration time, the smaller the temperature sensitivity, and the stronger the detection ability of the radiometer. However, the problem is that the detection time is sacrificed, and the application requirements with higher real-time performance cannot be met. At the same time, the improvement of the noise figure, gain stability, bandwidth and other indexes of existing direct detection radiometers is greatly affected by basic devices such as low-noise amplifiers and detectors. There are not only "bottlenecks" in performance improvement, but also higher costs. Summary of the Invention

[0006] To solve the deficiencies of the prior art, the present invention provides a direct detection type high-sensitivity millimeter wave and terahertz radiometer and its working method. The chopper modulation circuit is placed after the low-noise amplifier, which not only has a small impact on the overall noise deterioration of the radiometer, but also can effectively suppress the noise influence brought by the devices after the chopper modulation circuit.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a direct detection type high-sensitivity millimeter wave and terahertz radiometer.

[0009] The direct detection type high-sensitivity millimeter wave and terahertz radiometer includes a chopper switch, and an antenna, a first low-noise amplifier, and a second low-noise amplifier connected in sequence.

[0010] The chopper switch is connected to the connection line between the first low-noise amplifier and the second low-noise amplifier, and is used to chop the millimeter wave and terahertz signals amplified by the first low-noise amplifier.

[0011] Further, it further includes a chopper switch drive signal generator;

[0012] The chopper switch drive signal generator is connected to the chopper switch.

[0013] Further, the chopper switch drive signal generator is used to generate a drive signal to control the chopping frequency of the chopper switch.

[0014] Further, it further includes a detector connected to the second low-noise amplifier;

[0015] The detector is used to detect the signal amplified by the second low-noise amplifier.

[0016] Further, it further includes a filter connected to the detector;

[0017] The filter is used to filter the signal detected by the detector, and filter out the DC and low-frequency signals below the modulation frequency.

[0018] Further, it further includes a differential video amplifier connected to the filter;

[0019] The differential video amplifier amplifies the signal output by the filter.

[0020] Further, it further includes a bias power supply;

[0021] The bias power supply provides a bias power supply for active devices.

[0022] Further, the first low-noise amplifier is a broadband low-noise amplifier.

[0023] Further, one end of the chopper switch is connected to the connection line between the first low-noise amplifier and the second low-noise amplifier, and the other end is grounded.

[0024] The second aspect of the present invention provides a working method for a direct detection type high-sensitivity millimeter-wave and terahertz radiometer, including the following steps:

[0025] The millimeter-wave and terahertz signals are received by the antenna, amplified by the first low-noise amplifier, the amplified millimeter-wave and terahertz signals are chopped by the chopper switch, and the chopped signals are further amplified by the second low-noise amplifier.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] For the direct detection type high-sensitivity millimeter-wave and terahertz radiometer of the present invention, the chopper modulation technology is introduced into the circuit design of the millimeter-wave and terahertz direct detection radiometer. Considering that the chopper modulation circuit has a certain insertion loss, if it is directly placed at the first stage of the direct detection radiometer, it will deteriorate the noise figure of the radiometer, and further deteriorate the temperature sensitivity index of the radiometer. The introduced chopper modulation circuit cannot meet the requirement of optimizing the temperature sensitivity index of the radiometer. Therefore, the chopper modulation circuit is placed after the first-stage low-noise amplifier of the millimeter-wave and terahertz direct detection radiometer. The noise figure introduced by the chopper modulation circuit has little impact on the temperature sensitivity index of the radiometer. At the same time, the chopper modulation circuit can reduce the influence of environmental radio frequency noise, heat exchange device flicker noise (1 / f), etc., thereby improving the sensitivity index of the radiometer, laying a solid foundation for the detection of millimeter-wave and terahertz "near-noise" signals radiated by substances in nature.

[0028] For the direct detection type high-sensitivity millimeter-wave and terahertz radiometer of the present invention, the chopper modulation circuit is placed after the low-noise amplifier of the direct detection radiometer. It not only has little deterioration on the overall noise of the radiometer, but also can effectively suppress the noise influence brought by the devices after the chopper modulation circuit. By reasonably selecting the modulation frequency of the chopper and cooperating with appropriate filtering, the improvement of the temperature sensitivity index of the millimeter-wave and terahertz direct detection radiometer can be achieved. Description of the Drawings

[0029] The specification drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0030] Figure 1 It is the internal structure diagram of the direct detection type high-sensitivity millimeter-wave and terahertz radiometer of Embodiment 1 of the present invention. Detailed Embodiments

[0031] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0032] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] In the case of no conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0035] Embodiment 1

[0036] Embodiment 1 of the present invention provides a direct detection type high-sensitivity millimeter wave and terahertz radiometer, as Figure 1 shown, which includes a bias power supply 109, a chopper modulation circuit, and an antenna 101, a first low-noise amplifier 102, a second low-noise amplifier 105, a detector 106, a filter 107, and a differential video amplifier 108 that are connected in sequence.

[0037] Among them, both the first low-noise amplifier 102 and the second low-noise amplifier 105 are broadband low-noise amplifiers. The first low-noise amplifier 102 and the second low-noise amplifier 105 require the same bandwidth, and the noise figure required by the first low-noise amplifier 102 is smaller than that of the second low-noise amplifier 105.

[0038] The filter 107 is a high-pass filter for filtering out DC and low-frequency signals below the modulation frequency.

[0039] The chopper modulation circuit includes a chopper switch 103 and a chopper switch drive signal generator 104. The chopper switch 103 is connected to the connection line between the first low-noise amplifier 102 and the second low-noise amplifier 103 and is connected to the chopper switch drive signal generator 104. The chopper switch 103 also needs to be grounded.

[0040] The bias power supply 109 is respectively connected to the first low-noise amplifier 102, the chopper switch 103, the chopper switch drive signal generator 104, the second low-noise amplifier 105, and the differential video amplifier 108 for providing bias power for each active device.

[0041] The millimeter-wave and terahertz signals of the blackbody radiation of the substance are received by the antenna 101, amplified by the first low-noise amplifier 102, the amplified signal is chopped by the chopper switch 103, the chopped signal is further amplified by the second low-noise amplifier 105, the signal amplified by the second low-noise amplifier 105 is detected by the detector 106, the detected signal is filtered by the filter 107, after filtering out the DC and low-frequency signals below the modulation frequency, it is amplified by the differential video amplifier 108, and 2-channel differential voltages are output.

[0042] Among them, the chopper switch driving signal generator 104 is used to generate a driving signal to control the chopping frequency of the chopper switch 103.

[0043] In this embodiment, the chopper modulation technology is introduced into the circuit design of the millimeter-wave and terahertz direct detection radiometer. Considering that the chopper modulation circuit has a certain insertion loss, if it is directly placed at the first stage of the direct detection radiometer, it will deteriorate the noise figure of the radiometer, and further deteriorate the temperature sensitivity index of the radiometer. The introduced chopper modulation circuit cannot meet the requirement of optimizing the temperature sensitivity index of the radiometer. Therefore, in this embodiment, the chopper modulation circuit is placed after the first-stage low-noise amplifier of the millimeter-wave and terahertz direct detection radiometer. The noise figure introduced by the chopper modulation circuit has little impact on the temperature sensitivity index of the radiometer. At the same time, the chopper modulation circuit can reduce the influence of environmental radio frequency noise, heat exchange device flicker noise (1 / f), etc., thereby improving the sensitivity index of the radiometer, laying a solid foundation for the detection of millimeter-wave and terahertz "near-noise" signals radiated by substances in nature.

[0044] Embodiment 2

[0045] Embodiment 2 of the present invention provides a working method of a direct detection type high-sensitivity millimeter-wave and terahertz radiometer, including the following steps:

[0046] The millimeter-wave and terahertz signals of the blackbody radiation of the substance are received by the antenna 101, amplified by the first low-noise amplifier 102, the amplified signal is chopped by the chopper switch 103, the chopped signal is further amplified by the second low-noise amplifier 105, the signal amplified by the second low-noise amplifier 105 is detected by the detector 106, the detected signal is filtered by the filter 107, after filtering out the DC and low-frequency signals below the modulation frequency, it is amplified by the differential video amplifier 108, and 2-channel differential voltages are output.

[0047] Among them, the chopper switch 103 controls the chopping frequency through the driving signal generated by the chopper switch driving signal generator 104.

[0048] By reasonably selecting the modulation frequency of the chopper (i.e., the chopper composed of the chopper switch drive signal generator 104 and the chopper switch 103), and cooperating with appropriate filtering to filter out the DC and low-frequency signals below the modulation frequency, the temperature sensitivity of the millimeter-wave and terahertz direct detection radiometer can be improved.

[0049] In this embodiment, the chopper modulation technology is introduced into the circuit design of the millimeter-wave and terahertz direct detection radiometer. Considering that there is a certain insertion loss in the chopper modulation circuit, if it is directly placed in the first stage of the direct detection radiometer, it will deteriorate the noise figure of the radiometer, and further deteriorate the temperature sensitivity index of the radiometer. The introduced chopper modulation circuit cannot meet the requirement of optimizing the temperature sensitivity index of the radiometer. Therefore, in this embodiment, the chopper modulation circuit is placed after the first-stage low-noise amplifier of the millimeter-wave and terahertz direct detection radiometer. The noise figure introduced by the chopper modulation circuit has little impact on the temperature sensitivity index of the radiometer. At the same time, the chopper modulation circuit can reduce the influence of environmental radio frequency noise, heat exchange device flicker noise (1 / f), etc., thereby improving the sensitivity index of the radiometer, laying a solid foundation for the detection of millimeter-wave and terahertz "near-noise" signals radiated by substances in nature.

[0050] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Direct detection type high-sensitivity millimeter wave and terahertz radiometer, characterized in that: It includes a chopper switch, as well as an antenna, a first low-noise amplifier, and a second low-noise amplifier connected in sequence; The chopper switch is connected to the connection line between the first low-noise amplifier and the second low-noise amplifier, and is used to chop the millimeter-wave and terahertz signals amplified by the first low-noise amplifier; The direct detection type high-sensitivity millimeter-wave and terahertz radiometer further includes a chopper switch drive signal generator; The chopper switch drive signal generator is connected to the chopper switch; The chopper switch drive signal generator is used to generate a drive signal to control the chopping frequency of the chopper switch; It is amplified by the first low-noise amplifier, and the amplified millimeter-wave and terahertz signals are chopped by the chopper switch.

2. The direct detection type high-sensitivity millimeter wave and terahertz radiometer according to claim 1, wherein: It further includes a detector connected to the second low-noise amplifier; The detector is used to detect the signal amplified by the second low-noise amplifier.

3. The direct detection type high-sensitivity millimeter wave and terahertz radiometer according to claim 2, characterized in that: It further includes a filter connected to the detector; The filter is used to filter the signal detected by the detector to filter out the DC and low-frequency signals below the modulation frequency.

4. The direct detection type high-sensitivity millimeter wave and terahertz radiometer according to claim 3, characterized in that: It further includes a differential video amplifier connected to the filter; The differential video amplifier amplifies the signal output by the filter.

5. The direct detection type high-sensitivity millimeter wave and terahertz radiometer according to claim 1, characterized in that: It further includes a bias power supply; The bias power supply provides a bias power supply for the active devices.

6. The direct detection type high-sensitivity millimeter wave and terahertz radiometer according to claim 1, characterized in that: The first low-noise amplifier is a broadband low-noise amplifier.

7. The direct detection type high-sensitivity millimeter wave and terahertz radiometer according to claim 1, characterized in that: One end of the chopper switch is connected to the connection line between the first low-noise amplifier and the second low-noise amplifier, and the other end is grounded.

8. Method for operating a direct detection type high-sensitivity millimeter wave and terahertz radiometer, using the direct detection type high-sensitivity millimeter wave and terahertz radiometer according to any one of claims 1-7, characterized in that: It includes the following steps: The millimeter-wave and terahertz signals are received by the antenna, amplified by the first low-noise amplifier, the amplified millimeter-wave and terahertz signals are chopped by the chopper switch, and the chopped signals are further amplified by the second low-noise amplifier.

Images