Radiometer based on quasi-optical feed network and transmission loss test method thereof

Abstract

The invention discloses a radiometer based on a quasi-optical feed network and a test method of transmission loss of the radiometer. The radiometer comprises a reflector antenna system, the quasi-optical feed network and a direct mixing receiver which are arranged in sequence. The reflector antenna system is used for receiving a terahertz radiation signal and feeding the received terahertz radiation signal into the quasi-optical feed network; the quasi-optical feed network sequentially performs polarization separation and frequency separation on the terahertz radiation signal to obtain a plurality of radio frequency signals, and transmits the plurality of radio frequency signals to the direct frequency mixing receiver; the radio-frequency signal comprises a high-frequency signal and a low-frequency signal; by arranging the quasi-optical feed network, the transmission loss of the whole radiometer is calculated, errors caused by step-by-step testing are avoided, and the transmission loss of the quasi-optical feed network can be accurately measured; the technical problem that in the prior art, a vector network analyzer cannot accurately measure the transmission loss of the whole link when measuring the transmission loss step by step is solved.

Description

Technical Field

[0001] The invention belongs to the field of space microwave remote sensing, and in particular relates to a radiometer based on a quasi-optical feeding network and a test method for transmission loss thereof. Background Art

[0002] With the demand for full-band integrated observation of radiometers, traditional radiometers have problems such as defocusing and layout difficulties when sharing reflective surfaces in multiple frequency bands. The radiometer system based on quasi-optical feed network has become an emerging payload technology in the field of satellite-borne microwave remote sensing, and is also a hot spot and direction for research on key radiometer technologies in recent years. At present, the measurement of transmission loss of quasi-optical feed network mainly uses vector network analyzer to complete the test of key components, and then estimates the transmission loss index of quasi-optical feed network through simulation calculation. However, this method cannot measure the transmission damage of ellipsoid mirrors, reflectors and installation errors, and cannot complete the transmission loss measurement of the entire link. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a radiometer based on a quasi-optical feeding network and a test method for its transmission loss, so as to solve the technical problem that the vector network analyzer in the prior art cannot accurately measure the transmission loss of the entire link by measuring the transmission loss in steps.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0005] A radiometer based on a quasi-optical feeding network comprises a reflector antenna system, a quasi-optical feeding network and a direct mixing receiver which are arranged in sequence;

[0006] The reflector antenna system is used to receive a terahertz radiation signal and feed the received terahertz radiation signal into a quasi-optical feeding network;

[0007] The quasi-optical feeding network sequentially performs polarization separation and frequency separation on the terahertz radiation signal to obtain a plurality of radio frequency signals, and transmits the plurality of radio frequency signals to a direct mixing receiver;

[0008] The radio frequency signal includes a high frequency signal and a low frequency signal;

[0009] The direct mixing receiver is used to mix the received multiple radio frequency signals, and then perform intermediate frequency filtering, amplification and square law detection in sequence, output voltages corresponding to the multiple radio frequency signals, and transmit them to external data acquisition and processing equipment.

[0010] The quasi-optical feeding network comprises a polarization wire grid and a plurality of branches, each branch comprising a frequency selective surface, an ellipsoidal mirror, a plane mirror and a feed horn arranged in sequence;

[0011] The polarization wire grid is used to perform polarization separation on the terahertz radiation signal;

[0012] The frequency selective surface is used to divide the frequency of the terahertz radiation signal after polarization separation to obtain a high-frequency signal and a low-frequency signal;

[0013] The ellipsoid mirror and the plane mirror are used to jointly change the transmission paths of the high-frequency signal and the low-frequency signal so that they enter the feed horn;

[0014] The feed horn is used to be connected to a direct mixing receiver and send a high frequency signal and a low frequency signal to the direct mixing receiver.

[0015] A method for testing transmission loss, based on the radiometer based on the quasi-optical feeder network and the radiometer for testing, specifically comprises the following steps:

[0016] Step 1: Use the radiometer based on the quasi-optical feeder network to test the hot load and the cold load respectively, and record the output voltage V of the radiometer based on the quasi-optical feeder network respectively. Hot and V Cold , and obtain the voltage ratio Y;

[0017]

[0018] Step 2: Obtain the noise temperature T of the radiometer based on the quasi-optical feed network according to the following formula: sys , K;

[0019]

[0020] in:

[0021] T hot and T cold Represents the standard temperature measurement value of heating load and cooling load, K;

[0022] Step 3: Use the radiometer to test the hot load and the cold load respectively, and record the output voltage V of the radiometer respectively. REC_Hot and V REC_Cold , and get the voltage ratio Y REC ;

[0023]

[0024] The radiometer comprises a reflector antenna system and a receiver arranged in sequence;

[0025] The reflector antenna system is used to receive the terahertz radiation signal and send the received terahertz radiation signal to the receiver;

[0026] The receiver is used to perform intermediate frequency filtering, amplification and square-law detection on the received terahertz radiation signal in sequence, output a corresponding voltage, and transmit it to an external data acquisition and processing device;

[0027] Step 4: According to formula (4), the noise temperature T of the direct mixing receiver is obtained: REC , K;

[0028]

[0029] Step 5: Calculate the transmission loss L' of the quasi-optical feeder network according to formula (5), dB;

[0030]

[0031] L'=10log 10 (L) (6)

[0032] in:

[0033] T A is the radiation temperature of the heat load, K;

[0034] η is the emissivity of the radiant temperature of the heat load;

[0035] T p is the ambient temperature, K.

[0036] Compared with the prior art, the present invention has the following beneficial technical effects:

[0037] (I) In the present invention, a quasi-optical feeding network is set up to calculate the transmission loss of the entire radiometer, thereby avoiding the error caused by step-by-step testing and accurately measuring the transmission loss of the quasi-optical feeding network; and solving the technical problem in the prior art that the vector network analyzer cannot accurately measure the transmission loss of the entire link by measuring the transmission loss step by step.

[0038] (II) Compared with the traditional step-by-step test error model construction, the present invention can more simply establish a model of transmission loss in each frequency band, which is helpful for estimating network indicators; this method can use system calibration equipment to quickly and efficiently complete the test of the quasi-optical feeding network.

[0039] (III) The transmission loss test of the radiometer based on the quasi-optical feed network is one of the key technologies for the index test of the radiometer system based on the quasi-optical feed network. It can directly measure the transmission loss of the entire quasi-optical feed network link, and provide a basis for the design and index evaluation of the radiometer based on the quasi-optical feed network. It is a practical test method for the transmission loss of the quasi-optical feed network. This method is simple to implement and has high reliability. It can be used for satellite-borne multi-channel, integrated, and integrated radiometer systems, and has broad market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a receiving principle block diagram of the quasi-optical feeding network radiometer in the present invention;

[0041] Figure 2 It is a principle block diagram of the noise temperature test of the present invention;

[0042] Figure 3 The block diagram of the noise temperature test principle of the terahertz direct mixing receiver is shown in the figure.

[0043] The specific contents of the present invention are further explained in detail below in conjunction with embodiments. DETAILED DESCRIPTION

[0044] It should be noted that, unless otherwise specified, all components in the present invention are components known in the art.

[0045] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0046] The present invention provides a radiometer based on a quasi-optical feeding network, comprising a reflector antenna system, a quasi-optical feeding network and a direct mixing receiver which are arranged in sequence;

[0047] The reflector antenna system is used for receiving the terahertz radiation signal and feeding the received terahertz radiation signal into the quasi-optical feeding network;

[0048] The quasi-optical feeding network sequentially performs polarization separation and frequency separation on the terahertz radiation signal to obtain a plurality of radio frequency signals, and transmits the plurality of radio frequency signals to a direct mixing receiver;

[0049] Radio frequency signals include high frequency signals and low frequency signals;

[0050] The direct mixing receiver is used to mix multiple received RF signals, and then perform intermediate frequency filtering, amplification and square-law detection in sequence, output voltages corresponding to the multiple RF signals, and transmit them to external data acquisition and processing equipment.

[0051] In the above technical scheme, a quasi-optical feeding network is set up to calculate the transmission loss of the entire radiometer, thereby avoiding the error caused by step-by-step testing and accurately measuring the transmission loss of the quasi-optical feeding network; thereby solving the technical problem in the prior art that the vector network analyzer cannot accurately measure the transmission loss of the entire link by measuring the transmission loss in steps.

[0052] The quasi-optical feeding network includes a polarization wire grid and a plurality of branches, each branch including a frequency selective surface, an ellipsoid mirror, a plane mirror and a feed horn arranged in sequence;

[0053] Polarization wire grid is used to perform polarization separation on terahertz radiation signals;

[0054] The frequency selective surface is used to divide the frequency of the terahertz radiation signal after polarization separation to obtain a high-frequency signal and a low-frequency signal;

[0055] The ellipsoid mirror and the plane mirror are used to jointly change the transmission paths of the high-frequency signal and the low-frequency signal so that they enter the feed horn;

[0056] The feed horn is used to be connected to a direct mixing receiver and send high frequency signals and low frequency signals to the direct mixing receiver.

[0057] In the above technical solution, see Figure 1 The polarization wire grid in the first unit is used to polarize the terahertz signal received by the terahertz reflector antenna. The H-polarized wave is divided into two branches, high and low frequency, through the frequency selective surface. The high frequency branch separates the 664GHz signal, and the 664GHz_H signal passes through the ellipsoid mirror and the plane mirror and is fed into the 664GHz feed horn. The low frequency branch separates the 243GHz signal, and the 243GHz_H signal passes through the ellipsoid mirror and the plane mirror and is fed into the 243GHz feed horn. The V polarized wave is divided into two branches, high and low frequency, by the frequency selective surface. The high frequency branch separates out a 664 GHz signal, and the 664 GHz_V signal passes through the ellipsoidal mirror and the plane mirror and is fed into the 664 GHz feed horn. The low frequency branch passes through the three frequency selective surfaces in the three units behind in turn, and separates out 448 GHz, 325 GHz, 243 GHz and 183 GHz signals in turn. Each signal passes through the ellipsoidal mirror and the plane mirror respectively and is transmitted to the feed horn of each frequency band. The waveguide connection between the feed horn and the direct mixing receiver also reduces transmission loss.

[0058] A transmission loss testing method is based on a radiometer based on a quasi-optical feed network, and specifically includes the following steps:

[0059] Step 1: Use a radiometer based on a quasi-optical feed network to test the hot load and cold load respectively, and record the output voltage V of the radiometer based on the quasi-optical feed network respectively. Hot and V Cold , and obtain the voltage ratio Y;

[0060]

[0061] Step 2: Obtain the noise temperature T of the radiometer based on the quasi-optical feed network according to the following formula: sys , K;

[0062]

[0063] in:

[0064] T hot and T cold Represents the standard temperature measurement value of heating load and cooling load, K;

[0065] Step 3: Use a radiometer to test the hot load and cold load respectively, and record the output voltage V of the radiometer respectively. REC_Hot and V REC_Cold , and get the voltage ratio Y REC ;

[0066]

[0067] The radiometer includes a reflector antenna system and a receiver arranged in sequence;

[0068] The reflector antenna system is used to receive the terahertz radiation signal and send the received terahertz radiation signal to the receiver;

[0069] The receiver is used to perform intermediate frequency filtering, amplification and square-law detection on the received terahertz radiation signal in sequence, output the corresponding voltage, and transmit it to the external data acquisition and processing equipment;

[0070] Step 4: According to formula (4), the noise temperature T of the direct mixing receiver is obtained: REC , K;

[0071]

[0072] Step 5: Calculate the transmission loss L' of the quasi-optical feeder network according to formula (5), dB;

[0073]

[0074] L'=10log 10 (L) (6)

[0075] in:

[0076] T A is the radiation temperature of the heat load, K;

[0077] η is the emissivity of the radiant temperature of the heat load;

[0078] T p is the ambient temperature, K.

[0079] In the above technical scheme, the transmission loss test of the radiometer based on the quasi-optical feed network is one of the key technologies for the index test of the radiometer system based on the quasi-optical feed network. It can directly measure the transmission loss of the entire quasi-optical feed network link, and provide a basis for the design and index evaluation of the radiometer based on the quasi-optical feed network. It is a practical test method for the transmission loss of the quasi-optical feed network. This method is simple to implement and has high reliability. It can be used for satellite-borne multi-channel, integrated, and integrated radiometer systems, and has broad market application prospects.

Claims

1. A radiometer based on a quasi-optical feed network, characterized in that: It includes a reflector antenna system, a quasi-optical feed network and a direct mixing receiver which are arranged in sequence; The reflector antenna system is used to receive a terahertz radiation signal and feed the received terahertz radiation signal into a quasi-optical feeding network; The quasi-optical feeding network sequentially performs polarization separation and frequency separation on the terahertz radiation signal to obtain a plurality of radio frequency signals, and transmits the plurality of radio frequency signals to a direct mixing receiver; The radio frequency signal includes a high frequency signal and a low frequency signal; The direct mixing receiver is used to mix the received multiple radio frequency signals, and then perform intermediate frequency filtering, amplification and square law detection in sequence, output voltages corresponding to the multiple radio frequency signals, and transmit them to external data acquisition and processing equipment.

2. The radiometer based on a quasi-optical feed network as claimed in claim 1, characterized in that: The quasi-optical feeding network comprises a polarization wire grid and a plurality of branches, each branch comprising a frequency selective surface, an ellipsoidal mirror, a plane mirror and a feed horn arranged in sequence; The polarization wire grid is used to perform polarization separation on the terahertz radiation signal; The frequency selective surface is used to divide the frequency of the terahertz radiation signal after polarization separation to obtain a high-frequency signal and a low-frequency signal; The ellipsoid mirror and the plane mirror are used to jointly change the transmission paths of the high-frequency signal and the low-frequency signal so that they enter the feed horn; The feed horn is used to be connected to a direct mixing receiver and send a high frequency signal and a low frequency signal to the direct mixing receiver.

3. A transmission loss testing method, characterized in that: The method is based on the test of the radiometer based on the quasi-optical feeding network according to any one of claims 1 to 2, and specifically comprises the following steps: Step 1: Use the radiometer based on the quasi-optical feeder network as described in any one of claims 1 to 2 to test the hot load and the cold load respectively, and record the output voltage V of the radiometer based on the quasi-optical feeder network respectively. Hot and V Cold , and obtain the voltage ratio Y; Step 2: Obtain the noise temperature T of the radiometer based on the quasi-optical feed network according to the following formula: sys , K; in: T hot and T cold Represents the standard temperature measurement value of heating load and cooling load, K; Step 3: Use a radiometer to test the hot load and the cold load respectively, and record the output voltage V of the radiometer respectively. REC_Hot and V REC_Cold , and get the voltage ratio Y REC ; The said device comprises a reflector antenna system and a receiver arranged in sequence; The reflector antenna system is used to receive the terahertz radiation signal and send the received terahertz radiation signal to the receiver; The receiver is used to perform intermediate frequency filtering, amplification and square-law detection on the received terahertz radiation signal in sequence, output a corresponding voltage, and transmit it to an external data acquisition and processing device; Step 4: According to formula (4), the noise temperature T of the direct mixing receiver is obtained: REC , K; Step 5: Calculate the transmission loss L' of the quasi-optical feeder network according to formula (5), dB; L'=10log 10 (L) (6) in: T A is the radiation temperature of the heat load, K; η is the emissivity of the radiant temperature of the heat load; T p is the ambient temperature, K.

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