WO2009047557A1 - Receiver equalisation - Google Patents

Receiver equalisation Download PDF

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Publication number
WO2009047557A1
WO2009047557A1 PCT/GB2008/050916 GB2008050916W WO2009047557A1 WO 2009047557 A1 WO2009047557 A1 WO 2009047557A1 GB 2008050916 W GB2008050916 W GB 2008050916W WO 2009047557 A1 WO2009047557 A1 WO 2009047557A1
Authority
WO
WIPO (PCT)
Prior art keywords
array
receiver
output
equalisation
waveform
Prior art date
Application number
PCT/GB2008/050916
Other languages
French (fr)
Inventor
James Alexander Hill
Original Assignee
Bae Systems Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB0719941A external-priority patent/GB0719941D0/en
Application filed by Bae Systems Plc filed Critical Bae Systems Plc
Priority to EP08806732A priority Critical patent/EP2201402A1/en
Priority to AU2008309377A priority patent/AU2008309377A1/en
Priority to US12/301,539 priority patent/US20100182191A1/en
Publication of WO2009047557A1 publication Critical patent/WO2009047557A1/en

Links

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
    • 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
    • G01S7/4021—Means for monitoring or calibrating of parts of a radar system of receivers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
    • H01Q3/267—Phased-array testing or checking devices
    • 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
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S2013/0236—Special technical features
    • G01S2013/0245—Radar with phased array antenna
    • G01S2013/0254—Active array antenna
    • 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
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S2013/0236—Special technical features
    • G01S2013/0272—Multifunction radar

Definitions

  • the present invention relates to a method of receiver equalisation. More specifically, the present invention relates to a method of receiver equalisation in multi-function radar apparatus.
  • the performance of adaptive beam forming relies on the knowledge of the characteristics of the sub-arrays from which the beams are formed. It is therefore essential that the phase, gain and delay parameters of each sub-array are well known.
  • the present invention provides a method of receiver equalisation comprising the steps of: passing a known RF pulse through an array of receivers; comparing an output of the array with a reference output of the array; and calculating a correction waveform to be applied to the output of the array antenna.
  • Figure 1 is a diagram showing the process of the preferred embodiment of the present invention
  • Figure 2 is a diagram showing the movement of the process of the preferred embodiment of the present invention between the time and frequency domains.
  • each sub-array receiver is matched to a set of standard predetermined characteristics. This is done by an on-line equalisation process to ensure that this matching remains effective with time.
  • the process involves the injection, at the front end of the sub-array receiver system, an expanded RF pulse which is passed through the receivers and is digitally sampled.
  • the received pulse is compared in the frequency domain with the required response and a set of correction weights are computed. These weights are then digitally applied to all received signals.
  • a phased array antenna 10 is communicatively connected to a receiver path 20, that is to say the path from the receiving antenna through any analogue signal processing, where digitisation occurs.
  • the phased array antenna 10 can be any array type transmitter/receiver arrangement using phased on adaptive arrays, mobile communications antenna and the like.
  • the digitised signal is then communicated from the receiver path 20 to an equalisation module 30 to be corrected for any corruption of the pure received RF pulse that is induced by passing the signal through the receiver path 20.
  • This module is where the comparison of the known waveform and the reference waveform is carried out to produce the correction waveform which is subsequently applied to the data passing through the system that is corrected.
  • pulse compression module 40 which is a common signal processing function that is well known by skilled persons and will not be described in detail here.
  • the pulse compression module 40 Once the data has been output from the pulse compression module 40, it is supplied to any signal processing software 50 that is used to process the information gathered from the antenna array.
  • the receiver array of the radar to be calibrated is fed with a known swept waveform which covers the full bandwidth of the radar's 10 transmitted pulses across all frequencies.
  • the design of the swept pulse is chosen to provide enough resolution across the frequency range in the correction data, to enable it to be applied to any of the systems specified sampling rates.
  • the radar passes the output x of this known waveform to the receiver path 20, where it is digitised.
  • the equalisation module 30 compares the digitised output of the receiver array with a copy of the known waveform which was injected at the start of the process. This information is used to compute a correction waveform for use during the correction phase: Reference waveform
  • the calibration phase is carried out on start-up of the radar apparatus, then at increasing time intervals of, for example, 5 minutes then 30 minutes then every 2 hours after to allow for the radar apparatus to reach operational temperatures and received radar data to remain optimally corrected during this period. Calibration is required over the thermal range of the system as this can have a significant impact on the characteristic of the RF and analogue signal paths through the array prior to the data being digitised.
  • the antenna array 10 receives the radar returns as normal, transmits these to the receiver path 20, which digitises the radar returns and passes them onto the equalisation module 30.
  • the correction waveform as determined in the calibration phase is applied to the digitised radar return, which is then passed on to the pulse compression module 40 and then, in turn, to the radar software 50 for processing.
  • the preferred embodiment of the invention converts the radar return from the time domain to the frequency domain to - A - enable the radar return to be processed more easily, this is not strictly necessary however simplifies the implementation of the equalisation process in hardware terms.
  • the radar return is converted from the time domain to the frequency domain using a fast Fourier transform 200 before being passed to the equalisation module 210 where either the calibration or operation phase described above is carried out.
  • the signal Once the signal has been corrected in the operation phase, it is passed to the pulse compression module and other saturation processing functions while still in the frequency domain before being converted back to the time domain by an inverse fast Fourier transform 230 and then passed to the radar software 240.

Abstract

The present invention relates to a method of receiver equalisation. More specifically, the present invention relates to a method of receiver equalisation in multi-function radar apparatus. The present invention provides a method of receiver equalisation comprising the steps of: passing a known RF pulse through a receiver array; comparing an output of the receiver array with a reference output of thatarray; and calculating a correction waveform to be applied to the output of the array antennaat all times required during normal radar operation.

Description

RECEIVER EQUALISATION
The present invention relates to a method of receiver equalisation. More specifically, the present invention relates to a method of receiver equalisation in multi-function radar apparatus.
The performance of adaptive beam forming relies on the knowledge of the characteristics of the sub-arrays from which the beams are formed. It is therefore essential that the phase, gain and delay parameters of each sub-array are well known. The present invention provides a method of receiver equalisation comprising the steps of: passing a known RF pulse through an array of receivers; comparing an output of the array with a reference output of the array; and calculating a correction waveform to be applied to the output of the array antenna. Specific embodiments of the invention will now be described, by way of example only and with reference to the accompanying drawings that have like reference numerals, wherein :-
Figure 1 is a diagram showing the process of the preferred embodiment of the present invention; and Figure 2 is a diagram showing the movement of the process of the preferred embodiment of the present invention between the time and frequency domains.
The specific embodiment will now be described with reference to Figures 1 to 2:
To aid the knowledge of the phase, gain and delay parameters of each sub-array, each sub-array receiver is matched to a set of standard predetermined characteristics. This is done by an on-line equalisation process to ensure that this matching remains effective with time.
In this invention, the process involves the injection, at the front end of the sub-array receiver system, an expanded RF pulse which is passed through the receivers and is digitally sampled. The received pulse is compared in the frequency domain with the required response and a set of correction weights are computed. These weights are then digitally applied to all received signals.
In Figure 1 , there is shown the process of the preferred embodiment of the invention. A phased array antenna 10 is communicatively connected to a receiver path 20, that is to say the path from the receiving antenna through any analogue signal processing, where digitisation occurs. The phased array antenna 10, as an alternative, can be any array type transmitter/receiver arrangement using phased on adaptive arrays, mobile communications antenna and the like.
The digitised signal is then communicated from the receiver path 20 to an equalisation module 30 to be corrected for any corruption of the pure received RF pulse that is induced by passing the signal through the receiver path 20. This module is where the comparison of the known waveform and the reference waveform is carried out to produce the correction waveform which is subsequently applied to the data passing through the system that is corrected.
After passing through the equalisation module 30, the corrected data is sent to pulse compression module 40, which is a common signal processing function that is well known by skilled persons and will not be described in detail here.
Once the data has been output from the pulse compression module 40, it is supplied to any signal processing software 50 that is used to process the information gathered from the antenna array.
There are two modes of operation - the calibration phase and the operation phase.
In the calibration phase, the receiver array of the radar to be calibrated is fed with a known swept waveform which covers the full bandwidth of the radar's 10 transmitted pulses across all frequencies. The design of the swept pulse is chosen to provide enough resolution across the frequency range in the correction data, to enable it to be applied to any of the systems specified sampling rates. This allows for the correction data calculated during the calibration stage to be mathematically manipulated via decimation or interpolation, if required, and then to be re-applied to the operational data at any of the systems sampling rates in real time. Hence this covers the full bandwidth of the system during normal operation. The radar passes the output x of this known waveform to the receiver path 20, where it is digitised. At this point the known waveform has passed through the RF and analogue sections of the antenna array. The characteristic of these paths is then captured in the waveform in the form and can be detected by the computations in the calibration process. As these characteristics can differ over the frequency range, a full picture of the response of the system is determined and output to the equalisation module 30. The equalisation module 30 compares the digitised output of the receiver array with a copy of the known waveform which was injected at the start of the process. This information is used to compute a correction waveform for use during the correction phase: Reference waveform
Input waveform = Correction waveform
The calibration phase is carried out on start-up of the radar apparatus, then at increasing time intervals of, for example, 5 minutes then 30 minutes then every 2 hours after to allow for the radar apparatus to reach operational temperatures and received radar data to remain optimally corrected during this period. Calibration is required over the thermal range of the system as this can have a significant impact on the characteristic of the RF and analogue signal paths through the array prior to the data being digitised.
In the operation phase, the antenna array 10 receives the radar returns as normal, transmits these to the receiver path 20, which digitises the radar returns and passes them onto the equalisation module 30. The correction waveform as determined in the calibration phase is applied to the digitised radar return, which is then passed on to the pulse compression module 40 and then, in turn, to the radar software 50 for processing. Referring now to Figure 2, the preferred embodiment of the invention converts the radar return from the time domain to the frequency domain to - A - enable the radar return to be processed more easily, this is not strictly necessary however simplifies the implementation of the equalisation process in hardware terms. The radar return is converted from the time domain to the frequency domain using a fast Fourier transform 200 before being passed to the equalisation module 210 where either the calibration or operation phase described above is carried out. Once the signal has been corrected in the operation phase, it is passed to the pulse compression module and other saturation processing functions while still in the frequency domain before being converted back to the time domain by an inverse fast Fourier transform 230 and then passed to the radar software 240.
It should be noted by the skilled person that it is not necessary to convert the radar return into the frequency domain, as the processing can be implemented in hardware or software in either the frequency or time domain as necessary. The method employed in the preferred embodiment described herein is relatively cost-effective with respect to the physical hardware requirements, such as the area required on a hardware board, for example. It will be appreciated by the skilled reader that the principles of the invention above could be implemented all or partly using software. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

Claims
1 . A method of receiver equalisation comprising the steps of: passing a known RF pulse through a receiver array of an antenna; comparing an output of the receiver array with a reference output of the array; and calculating a correction waveform to be applied to the output of the array.
2. A method according to claim 1 wherein the known swept RF waveform covering the operational bandwidth of the array antenna is utilised.
3. A method according to any previous claim wherein the output of the receiver array is digitised before being compared to the reference output of the receiver array.
4. A method according to any previous claim wherein the output of the receiver array is fast Fourier transformed into the frequency domain before being compared to the reference output of the receiver array.
5. A method as substantially hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.
6. An apparatus as substantially hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.
PCT/GB2008/050916 2007-10-12 2008-10-07 Receiver equalisation WO2009047557A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP08806732A EP2201402A1 (en) 2007-10-12 2008-10-07 Receiver equalisation
AU2008309377A AU2008309377A1 (en) 2007-10-12 2008-10-07 Receiver equalisation
US12/301,539 US20100182191A1 (en) 2007-10-12 2008-10-07 Receiver equalisation

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP07270059.4 2007-10-12
GB0719941.7 2007-10-12
GB0719941A GB0719941D0 (en) 2007-10-12 2007-10-12 Receiver equalisation
EP07270059 2007-10-12

Publications (1)

Publication Number Publication Date
WO2009047557A1 true WO2009047557A1 (en) 2009-04-16

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2008/050916 WO2009047557A1 (en) 2007-10-12 2008-10-07 Receiver equalisation

Country Status (4)

Country Link
US (1) US20100182191A1 (en)
EP (1) EP2201402A1 (en)
AU (1) AU2008309377A1 (en)
WO (1) WO2009047557A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2473663A (en) * 2009-09-21 2011-03-23 Cambridge Consultants Radar

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6659400B2 (en) * 2016-02-24 2020-03-04 株式会社東芝 Signal processing device, radar device, and method of setting radar device

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5499031A (en) * 1989-09-28 1996-03-12 The Marconi Company Limited Distributed receiver system for antenna array
US6157343A (en) * 1996-09-09 2000-12-05 Telefonaktiebolaget Lm Ericsson Antenna array calibration
US20040178951A1 (en) * 2002-03-13 2004-09-16 Tony Ponsford System and method for spectral generation in radar
US20050140546A1 (en) * 2003-12-27 2005-06-30 Hyeong-Geun Park Transmitting and receiving apparatus and method in adaptive array antenna system capable of real-time error calibration

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4901082A (en) * 1988-11-17 1990-02-13 Grumman Aerospace Corporation Adaptive waveform radar
FR2829638B1 (en) * 2001-09-07 2003-12-12 Thales Sa METHOD AND DEVICE FOR ANTI-INTERFERENCE, IN RECEPTION, OF A BROADBAND RADIOELECTRIC SIGNAL
FR2845218B1 (en) * 2002-09-27 2004-11-05 Thales Sa METHOD AND DEVICE FOR SCALE-EQUALIZATION OF A RECEPTION SYSTEM
GB0327041D0 (en) * 2003-11-21 2003-12-24 Roke Manor Research Apparatus and methods

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5499031A (en) * 1989-09-28 1996-03-12 The Marconi Company Limited Distributed receiver system for antenna array
US6157343A (en) * 1996-09-09 2000-12-05 Telefonaktiebolaget Lm Ericsson Antenna array calibration
US20040178951A1 (en) * 2002-03-13 2004-09-16 Tony Ponsford System and method for spectral generation in radar
US20050140546A1 (en) * 2003-12-27 2005-06-30 Hyeong-Geun Park Transmitting and receiving apparatus and method in adaptive array antenna system capable of real-time error calibration

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2473663A (en) * 2009-09-21 2011-03-23 Cambridge Consultants Radar
GB2473663B (en) * 2009-09-21 2016-11-23 Aveillant Ltd Radar Receiver

Also Published As

Publication number Publication date
AU2008309377A1 (en) 2009-04-16
EP2201402A1 (en) 2010-06-30
US20100182191A1 (en) 2010-07-22

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