WO2006035109A1 - Method and apparatus for calibration of horizontal and vertical channels in a dual polarized weather radar - Google Patents

Method and apparatus for calibration of horizontal and vertical channels in a dual polarized weather radar Download PDF

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Publication number
WO2006035109A1
WO2006035109A1 PCT/FI2005/000414 FI2005000414W WO2006035109A1 WO 2006035109 A1 WO2006035109 A1 WO 2006035109A1 FI 2005000414 W FI2005000414 W FI 2005000414W WO 2006035109 A1 WO2006035109 A1 WO 2006035109A1
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WO
WIPO (PCT)
Prior art keywords
radar
feed
calibration
combination
signal
Prior art date
Application number
PCT/FI2005/000414
Other languages
French (fr)
Inventor
Pentti Karhunen
Henry Andersson
Juha Salmivaara
Original Assignee
Vaisala Oyj
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Publication date
Application filed by Vaisala Oyj filed Critical Vaisala Oyj
Publication of WO2006035109A1 publication Critical patent/WO2006035109A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/95—Radar or analogous systems specially adapted for specific applications for meteorological use
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/024—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using polarisation effects
    • G01S7/025—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using polarisation effects involving the transmission of linearly polarised waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4004—Means for monitoring or calibrating of parts of a radar system
    • G01S7/4017—Means for monitoring or calibrating of parts of a radar system of HF systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4004—Means for monitoring or calibrating of parts of a radar system
    • G01S7/4026—Antenna boresight
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4004—Means for monitoring or calibrating of parts of a radar system
    • G01S7/4026—Antenna boresight
    • G01S7/403—Antenna boresight in azimuth, i.e. in the horizontal plane
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4004—Means for monitoring or calibrating of parts of a radar system
    • G01S7/4026—Antenna boresight
    • G01S7/4034—Antenna boresight in elevation, i.e. in the vertical plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Definitions

  • the invention relates to a method according to the preamble of claim 1 for calibration of horizontal (H) and vertical (V) channels in a dual polarized weather radar.
  • the invention relates also to an apparatus for calibration of H- and V- channels in a dual polarized weather radar.
  • the goal of the invention is accomplished by using a secondary feed and placing it typically in the center of the antenna dish opposite to the primary feed of the radar antenna.
  • a low power signal on the radar's operating frequency is fed to the secondary feed and transmitted towards the primary feed.
  • This calibration signal is received normally by H- and V-channels of the radar receiver and differences observed between the channels are used as calibration information for actual weather echoes.
  • the high power transmission from the primary feed can also be used for calibration and the secondary feed used as receiving antenna. More specifically, the method according to the invention is characterized by what is stated in the characterizing part of claim 1.
  • the invention offers significant benefits over conventional techniques.
  • the invention improves calibration accuracy of the radar and enables calibration in real time during normal operation. Real time calibration makes it possible to calibrate more often, which increases the overall accuracy of the measurement system. Further, also possible device defects can be effectively indicated.
  • Figure 1 shows a basic configuration of a dual polarized weather radar in accordance with the prior art.
  • Figure 2 shows as a block diagram a first calibration arrangement in accordance with the invention using a secondary feed.
  • Figure 3 shows as a block diagram a second calibration arrangement in accordance with the invention.
  • Figure 4 shows as a block diagram a third calibration arrangement in accordance with the invention.
  • a dual polarized weather radar comprises the following elements: An amplifier unit comprising typically an exiter 2 and a power amplifier 3. The system is synchronized by a master oscillator 1 connected to exciter 2. On transmission a signal phase locked to the radar's master oscillator 1 and on the radar's operating frequency is formed in the exciter 2, amplified by power amplifier 3. In magnetron type radars exciter 2 is not used but the amplifier 3 acts as an oscillator.
  • Power amplifier 3 output is connected to at least one of the duplexers 7 by a polarizer 6, that splits the signal into horizontal (H) and vertical (V) components. Depending on mode of operation of the radar, the H- and V-components are sent alternately (in turns) or simultaneously.
  • duplexers 7 From duplexers 7 the H- and V-components of the signal are fed to orthomode feed 9 and directed to atmosphere by dish reflector 8.
  • H- and V-components are separated by the orthomode feed 9 and directed by duplexers 7 to H-channel 4 and V-channel 5 of radar receiver, both of the receivers 4 and 5 having an output for the detected signal for further processing.
  • Figure 2 shows as a block diagram of the calibration arrangement using a secondary feed 10 according to the invention placed in center of the antenna dish 8.
  • the secondary feed 10 is linearly polarized in a plane forming an angle of 45 degrees with the plane of polarization of the orthomode primary feed 9.
  • the difference between the planes of polarizartion causes the calibration signal to be split into horizontal and vertical components in the primary orthomode feed 9.
  • a low power calibration signal on the radar's operating frequency locked to the master oscillator of the radar system is fed from exciter 2 to secondary feed 10 and transmitted towards the primary feed 9.
  • the low power calibration signal can be pulsed and its pulse repetition frequency can be chosen to be same as pulse repetition frequency of the radar's high power transmission but continuous wave signal can as well be used if high power transmission is blocked during calibration.
  • the calibration signals are received by H- and V-channels 4, 5 of the radar receiver as in normal operation of the radar and differences between the channels are observed.
  • FIG. 3 shows as a block diagram of the calibration arrangement for transmission paths of the radar using a secondary feed 10 placed in center of the antenna dish 8.
  • polarizer 6 is used to transmit alternately on H- and V-channels of the radar.
  • the secondary feed 10 is linearly polarized in a plane forming an angle of 45 degrees with the plane of polarization of the orthomode primary feed 9.
  • the difference between the planes of polarization enables the secondary feed 10 to receive both H- and V-components of radar transmission.
  • the secondary feed 10 may also be circularly polarized which enables it to receive both polarizations from the primary feed 9.
  • the signal from the secondary feed is directed to duplexer 12 and then to calibration receiver 11 locked to the radar's master oscillator. Reception of both H-and V-polarizations is done alternately during normal operation of the radar. Differences between the channels are used as calibration information for actual weather echoes.
  • FIG. 4 shows as a block diagram of the calibration arrangement for transmission paths of the radar using a secondary feed 10 placed in center of the antenna dish 8.
  • polarizer 6 is used to transmit either alternately or simultaneously on H- and V-channels of the radar.
  • the secondary feed 10 is linearly polarized in a plane aligned with the plane of polarization of the orthomode primary feed 9.
  • a RF switch 13 is placed between the secondary feed 10 and the duplexer 12.
  • the RF switch is used to choose H- or V- feed points of the secondary feed.
  • the signal from the RF switch is directed to duplexer 12 and then to calibration receiver 11 locked to the radar's master oscillator. Reception of both H-and V-polarizations is done alternately during normal operation of the radar using the RF switch. Differences between the channels are used as calibration information for actual weather echoes. Common signal path from the RF switch to the receiver eliminates measurement errors between the polarization channels.
  • the secondary feed 10 may be linearly polarized in a plane forming an angle of 45 degrees with the plane of polarization of the orthomode primary feed 9.
  • the difference between the planes of polarization can split the calibration signal into H- and V-components in the primary orthomode feed 9.
  • the secondary feed 10 may also be circularly polarized in which case the transmission also contains H- and V-components.
  • Polarization of the secondary feed may also be aligned with polarization of the orthomode feed 9 if alternate mode of operation is adopted.
  • a low power calibration signal on the radar's operating frequency locked to the master oscillator of the radar system is fed from exciter 2 to secondary feed 10 and transmitted towards the primary feed 9.
  • the low power calibration signal is pulsed and its pulse repetition frequency is same as pulse repetition frequency of the radar's high power transmission.
  • the calibration signals are received by H- and V-channels 4, 5 of the radar receiver as part of normal operation of the radar and differences between the channels observed.
  • the secondary feed 10 is linearly polarized in a plane forming an angle of 45 degrees with the plane of polarization of the orthomode primary feed 9.
  • the secondary feed 10 may also be circularly polarized which enables it to receive both polarizations from the primary feed 9.
  • Polarzation of the secondary feed may also be aligned with polarization of the orthomode feed 9 if alternate mode of operation is adopted.
  • a coaxial cable or wave guide is used to feed calibration signal from exciter 2 to secondary feed 10.

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

The present invention relates to a method and apparatus for calibration of horizontal (H) and vertical (V) channels in a dual polarized weather radar. The goal of the invention is accomplished by placing an secondary feed (10) in center of the antenna dish (8) opposite to the primary feed (9) of the radar antenna. A low power signal on the radar's operating frequency is fed to the secondary feed (10) and transmitted towards the primary feed. The calibration signal is received normally by H- and V-channels (4), (5) of the radar receiver and differences observed between the channels are used as calibration information for actual weather echoes. The secondary antenna can also be used for reception of the high power signal of the radar to calibrate the transmission channels of the radar.

Description

Method and apparatus for calibration of horizontal and vertical channels in a dual polarized weather radar
The invention relates to a method according to the preamble of claim 1 for calibration of horizontal (H) and vertical (V) channels in a dual polarized weather radar.
The invention relates also to an apparatus for calibration of H- and V- channels in a dual polarized weather radar.
In the prior art solutions the calibration is performed manually by feeding signals from a signal generator into the system using wave guide directional couplers or directing the radar towards a fixed target. These prior art systems do not allow easy real time calibration, which may be necessary during normal operation in changing environmental surroundings. Especially rapidly changing temperatures may cause errors in the measuring system.
It is an object of the present invention to overcome the drawbacks of the above-described techniques and to provide an entirely novel type of method and apparatus for calibration of H- and V- channels in a dual polarized weather radar in real time.
The goal of the invention is accomplished by using a secondary feed and placing it typically in the center of the antenna dish opposite to the primary feed of the radar antenna. A low power signal on the radar's operating frequency is fed to the secondary feed and transmitted towards the primary feed.
This calibration signal is received normally by H- and V-channels of the radar receiver and differences observed between the channels are used as calibration information for actual weather echoes.
The high power transmission from the primary feed can also be used for calibration and the secondary feed used as receiving antenna. More specifically, the method according to the invention is characterized by what is stated in the characterizing part of claim 1.
Furthermore, the apparatus according to the invention is characterized by what is stated in the characterizing part of claim 16.
The invention offers significant benefits over conventional techniques.
The invention improves calibration accuracy of the radar and enables calibration in real time during normal operation. Real time calibration makes it possible to calibrate more often, which increases the overall accuracy of the measurement system. Further, also possible device defects can be effectively indicated.
In the following the invention is described in greater detail with the help of exemplifying embodiments illustrated in the appended drawings in which,
Figure 1 shows a basic configuration of a dual polarized weather radar in accordance with the prior art.
Figure 2 shows as a block diagram a first calibration arrangement in accordance with the invention using a secondary feed.
Figure 3 shows as a block diagram a second calibration arrangement in accordance with the invention.
Figure 4 shows as a block diagram a third calibration arrangement in accordance with the invention.
According to figure 1, a dual polarized weather radar comprises the following elements: An amplifier unit comprising typically an exiter 2 and a power amplifier 3. The system is synchronized by a master oscillator 1 connected to exciter 2. On transmission a signal phase locked to the radar's master oscillator 1 and on the radar's operating frequency is formed in the exciter 2, amplified by power amplifier 3. In magnetron type radars exciter 2 is not used but the amplifier 3 acts as an oscillator.
Power amplifier 3 output is connected to at least one of the duplexers 7 by a polarizer 6, that splits the signal into horizontal (H) and vertical (V) components. Depending on mode of operation of the radar, the H- and V-components are sent alternately (in turns) or simultaneously.
From duplexers 7 the H- and V-components of the signal are fed to orthomode feed 9 and directed to atmosphere by dish reflector 8.
On reception the H- and V-components are separated by the orthomode feed 9 and directed by duplexers 7 to H-channel 4 and V-channel 5 of radar receiver, both of the receivers 4 and 5 having an output for the detected signal for further processing.
Figure 2 shows as a block diagram of the calibration arrangement using a secondary feed 10 according to the invention placed in center of the antenna dish 8.
The secondary feed 10 is linearly polarized in a plane forming an angle of 45 degrees with the plane of polarization of the orthomode primary feed 9.
The difference between the planes of polarizartion causes the calibration signal to be split into horizontal and vertical components in the primary orthomode feed 9.
A low power calibration signal on the radar's operating frequency locked to the master oscillator of the radar system is fed from exciter 2 to secondary feed 10 and transmitted towards the primary feed 9.
The low power calibration signal can be pulsed and its pulse repetition frequency can be chosen to be same as pulse repetition frequency of the radar's high power transmission but continuous wave signal can as well be used if high power transmission is blocked during calibration.
When pulsed calibration signal is used transmission of calibration and high power signals are synchronized so that the calibration signal is received instead of atmospheric echo on a chosen range gate on which a strong atmospheric echo is not present.
The calibration signals are received by H- and V-channels 4, 5 of the radar receiver as in normal operation of the radar and differences between the channels are observed.
Differences between the channels are used as calibration information for actual weather echoes.
Figure 3 shows as a block diagram of the calibration arrangement for transmission paths of the radar using a secondary feed 10 placed in center of the antenna dish 8. In this embodiment polarizer 6 is used to transmit alternately on H- and V-channels of the radar.
The secondary feed 10 is linearly polarized in a plane forming an angle of 45 degrees with the plane of polarization of the orthomode primary feed 9.
The difference between the planes of polarization enables the secondary feed 10 to receive both H- and V-components of radar transmission.
The secondary feed 10 may also be circularly polarized which enables it to receive both polarizations from the primary feed 9.
The signal from the secondary feed is directed to duplexer 12 and then to calibration receiver 11 locked to the radar's master oscillator. Reception of both H-and V-polarizations is done alternately during normal operation of the radar. Differences between the channels are used as calibration information for actual weather echoes.
Method explained in figure 2 can be used simultaneously with the method of figure 3 by connecting low power signal from exciter 2 to secondary feed 10 through duplexer 12. Essential for the invention is the correct placing of the secondary feed 10. It should have a direct connection without reflections to the primary feed 9 and therefore it is advantageous that the secondary feed 10 is positioned typically in the centre of the dish 8 and typically opposite to the primary feed 9. Further, for the system and method is important that the signal from or into the secondary feed is synchronized with and connected directly or undirectly to the master oscillator 1 of the system.
Figure 4 shows as a block diagram of the calibration arrangement for transmission paths of the radar using a secondary feed 10 placed in center of the antenna dish 8. In this embodiment polarizer 6 is used to transmit either alternately or simultaneously on H- and V-channels of the radar.
The secondary feed 10 is linearly polarized in a plane aligned with the plane of polarization of the orthomode primary feed 9.
A RF switch 13 is placed between the secondary feed 10 and the duplexer 12. The RF switch is used to choose H- or V- feed points of the secondary feed.
The signal from the RF switch is directed to duplexer 12 and then to calibration receiver 11 locked to the radar's master oscillator. Reception of both H-and V-polarizations is done alternately during normal operation of the radar using the RF switch. Differences between the channels are used as calibration information for actual weather echoes. Common signal path from the RF switch to the receiver eliminates measurement errors between the polarization channels.
By connecting low power signal from exciter 2 to secondary feed 10 through duplexer 12 and RF switch the arrangement described in figure 4 can also be used to calibrate receiving paths of the radar. Then the RF switch is used to transmit H- and V-polarizations alternatively from the secondary feed 10. By using pulsed transmission both tranmission and receiving paths can be measured simultaneously. he following alternative preferred embodiments of the invention:
- The secondary feed 10 may be linearly polarized in a plane forming an angle of 45 degrees with the plane of polarization of the orthomode primary feed 9.
- the difference between the planes of polarization can split the calibration signal into H- and V-components in the primary orthomode feed 9.
- the secondary feed 10 may also be circularly polarized in which case the transmission also contains H- and V-components.
- Polarization of the secondary feed may also be aligned with polarization of the orthomode feed 9 if alternate mode of operation is adopted.
- A low power calibration signal on the radar's operating frequency locked to the master oscillator of the radar system is fed from exciter 2 to secondary feed 10 and transmitted towards the primary feed 9.
— The low power calibration signal is pulsed and its pulse repetition frequency is same as pulse repetition frequency of the radar's high power transmission.
- Transmision of calibration and high power transmission are synchronized so that the calibration signal is received instead of atmospheric echo on chosen range gate on which a strong atmospheric echo is not present.
- The calibration signals are received by H- and V-channels 4, 5 of the radar receiver as part of normal operation of the radar and differences between the channels observed.
- Differences between the channels are used as calibration information for actual weather echoes.
- Continuous wave transmission of the calibration signal can as well be used if high power transmission is blocked during calibration.
e apparatus there are following options according to the invention:
- The secondary feed 10 is linearly polarized in a plane forming an angle of 45 degrees with the plane of polarization of the orthomode primary feed 9.
- The secondary feed 10 may also be circularly polarized which enables it to receive both polarizations from the primary feed 9.
Polarzation of the secondary feed may also be aligned with polarization of the orthomode feed 9 if alternate mode of operation is adopted.
- A coaxial cable or wave guide is used to feed calibration signal from exciter 2 to secondary feed 10.

Claims

Claims:
1. A method for calibration of at least two polarized channels in a dual polarized weather radar which method - a radar signal is formed in an amplifier unit (2, 3) controlled by a master oscillator
(D,
- the radar signal is split to at least two components (H, V) having different polarities,
- these signal components are sent to atmosphere by a primary feed (9) and an reflector (8),
- the signals reflected from the atmosphere are received by the primary feed (9) with help of the reflector (8), characterized in that during or in-between the normal operation
- an input signal is fed to a secondary feed (10) located in vicinity of the primary feed (9) and this signal is received directly by the primary feed (9) and used for calibration purposes e.g, for compensating for the difference between the channels (H, V).
2. A method according to claim 1, characterized in that the calibration signal is received by orthomode primary feed (9) of the radar and passed to H- and V-channels (4), (5) of the radar receiver, and differences observed between the channels are used as calibration information for actual weather echoes.
3. A method according to claim 1 or 2, characterized in that the secondary feed (10) is linearly polarized in a plane forming an angle of 45 degrees with the plane of polarization of the orthomode primary feed (9).
4. A method according to any preceding claim or their combination, characterized in that the difference between the planes of polarization causes the calibration signal to be split into H- and V-components in the primary orthomode feed (9).
5. A method according to any preceding claim or their combination, characterized in that the secondary feed (10) is circularly polarized whereby the transmission also contains H- and V-components.
6. A method according to any preceding claim or their combination, characterized in that low power calibration signal on the radar's operating frequency locked to the master oscillator of the radar system is fed from exciter (2) to secondary feed (10) and transmitted towards the primary feed (9).
7. A method according to any preceding claim or their combination, characterized in that the low power calibration signal is pulsed and its pulse repetition frequency is same as pulse repetition frequency of the radar's high power transmission.
8. A method according to any preceding claim or their combination, characterized in that transmission of calibration and high power transmission are synchronized so that the calibration signal is received instead of atmospheric echo on chosen range gate on which a strong atmospheric echo is not present.
9. A method according to any preceding claim or their combination, characterized in that polarization of the secondary feed (10) is aligned with polarization of the orthomode feed
(9) if alternate mode of operation is adopted.
10. A method according to any preceding claim or their combination, characterized in that continuous wave transmission of the calibration signal can as well be used if high power transmission is blocked during calibration.
11. A method according to any preceding claim or their combination, characterized in that a polarizer (6) is used to transmit using alternately H- and V-channels of the radar.
12. A method according to any preceding claim or their combination, characterized in that the difference between the planes of polarization enables the secondary feed (10) to receive both H- and V-components of radar transmission.
13. A method according to any preceding claim or their combination, characterized in that the signal from the secondary feed is directed to duplexer (12) and then to calibration receiver (11) locked to the radar's master oscillator.
14. A method according to any preceding claim or their combination, characterized in that reception of both H-and V-polarizations is done alternately during normal operation of the radar.
15. A method according to any preceding claim or their combination, characterized in that it is used at simultaneously with this method by connecting low power signal from exciter (2) to secondary feed (10) through duplexer (12).
16. An apparatus for calibration of different channels in a dual polarized weather radar, which apparatus comprises
- an amplifier unit (2, 3) for forming a radar signal - a master oscillator (1) for controlling functioning of the radar
- means for spotting the radar signal to at least two components (H, V) having different polarities,
- primary feed (9) and reflector (8) for sending and receiving these signal components to and from atmosphere, characterized in that the apparatus comprises
- a secondary feed (10) located in vicinity of the primary feed (9), and
- means for feeding a calibration signal to the secondary feed (10) for calibrating the system.
17. An apparatus according to any preceding claim or their combination, characterized in that the secondary feed (10) is located in the center of the antenna dish (8).
18. An apparatus according to any preceding claim or their combination, characterized in that polarization of the secondary feed (10) is aligned with polarization of the orthomode feed (9) if alternate mode of operation is adopted.
19. An apparatus according to any preceding claim or their combination, characterized in that the secondary feed (10) is linearly polarized in a plane forming an angle of 45 degrees with the plane of polarization of the orthomode primary feed (9).
20. An apparatus according to any preceding claim or their combination, characterized in the secondary feed (10) may also be circularly polarized in which case the transmission also contains H- and V-components.
21. An apparatus according to any preceding claim or their combination, characterized in a coaxial cable or wave guide is used to direct signal from secondary feed (10) to calibration receiver (11) through a duplexer (12).
22. An apparatus according to any preceding claim or their combination, characterized in that the secondary feed (10) is located in center of the antenna dish (8).
PCT/FI2005/000414 2004-09-30 2005-09-28 Method and apparatus for calibration of horizontal and vertical channels in a dual polarized weather radar WO2006035109A1 (en)

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FI20041269 2004-09-30
FI20041269A FI116987B (en) 2004-09-30 2004-09-30 Method and apparatus for calibrating horizontal and vertical channels in a double-polarized weather radar

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US7495599B2 (en) * 2005-05-23 2009-02-24 Vaisala Oyj Simultaneous dual polarization radar system with pedestal mounted receiver
EP2240795A1 (en) * 2007-12-07 2010-10-20 Baron Services, Inc. An improved system and method for dual polarization radar with automatic built-in test equipment and calibration
US8004458B2 (en) 2007-03-13 2011-08-23 Baron Services, Inc. Means for dual polarization radar with automatic built-in test equipment and calibration
CN103399306A (en) * 2013-08-03 2013-11-20 张鹿平 Method for reducing radar feed line loss and improving two-path feed line consistency
EP2799898A1 (en) * 2013-05-02 2014-11-05 Selex ES GmbH Weather radar
CN109946662A (en) * 2019-05-06 2019-06-28 成都远望科技有限责任公司 Calibration System in a kind of phased array weather radar machine
US10495787B2 (en) 2016-06-16 2019-12-03 I.M. Systems Group, Inc. Integrated weather projection systems, methods, and apparatuses
CN113109771A (en) * 2021-03-18 2021-07-13 中国气象局气象探测中心 Calibration device for calibrator and weather radar echo intensity true value calibration method
CN115113156A (en) * 2022-08-26 2022-09-27 中国人民解放军国防科技大学 Calibration method and system for dual-polarized phased array meteorological radar
US11495892B2 (en) 2020-04-30 2022-11-08 The Regents Of The University Of Michigan Polarization-independent spatial power divider for a two-port millimeter-wave antenna

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US10495787B2 (en) 2016-06-16 2019-12-03 I.M. Systems Group, Inc. Integrated weather projection systems, methods, and apparatuses
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CN109946662A (en) * 2019-05-06 2019-06-28 成都远望科技有限责任公司 Calibration System in a kind of phased array weather radar machine
CN109946662B (en) * 2019-05-06 2023-09-26 成都远望科技有限责任公司 Phased array weather radar built-in calibration system
US11495892B2 (en) 2020-04-30 2022-11-08 The Regents Of The University Of Michigan Polarization-independent spatial power divider for a two-port millimeter-wave antenna
CN113109771B (en) * 2021-03-18 2023-06-06 中国气象局气象探测中心 Calibration device for calibration instrument and true value calibration method for weather radar echo intensity
CN113109771A (en) * 2021-03-18 2021-07-13 中国气象局气象探测中心 Calibration device for calibrator and weather radar echo intensity true value calibration method
CN115113156A (en) * 2022-08-26 2022-09-27 中国人民解放军国防科技大学 Calibration method and system for dual-polarized phased array meteorological radar

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