GB2169145A - Method of providing a scanning radio beam - Google Patents

Abstract

A transmitting aerial array is end fed with an energy pulse having a duration shorter than the transit time of the pulse along the array, whereby with an arcuate or preferably circular array azimuth scanning can be obtained. <IMAGE>

Description

SPECIFICATION Method of providing a scanning radio beam This invention relates two a method of providing a scanning radio beam as used,forexample, in primary and secondary radar, optical radar, anti sea clutter radar, ECCM radar, and navigation aids.

Known methods of providing electronic beam scanning includefrequencyscanning using a dispersive antenna such as a slotted waveguide array as described in Chapter 4, Volume 2 of "Microwave Scanning Antennas" by R. C. Hansen; phase scanning as described in Chapter 3, Volume 2 ofthe above mentioned book; methods using a multiport array feeding a matrix as described at pages 11-66 and 11-67 of"Radar Handbook" (McGraw Hill 1970) edited by M.

I. Skolnok; methods using a combination offastand slow frequency scanning to scan in both range and azimuth, in which methods the beam steering function is intimately related to the ranging function.

These known methods suffer from the disadvan tagesthatthey require the use of complex and thus expensive apparatus for transmitting the radio beam, and that the size of the apparatus required limits the possibilities for use of the apparatus.

According to this invention there is provided a method of providing a scanning radio beam, in which a transmitting aerial array is end fed with an energy pulse having a duration shorterthanthetransittime of the pulse along the array.

The method of this invention has the advantage that it provides a very high speed scanning electron bunch which produces a beam, of azimuth width appropriate for use in a high resolution marine radar system, and such use will now be described byway of example with reference to the drawing which diagrammatically illustrates an aerial array mounted around a ship's funnel.

The drawing illustrates a fixed aerial array circular in plan constituted by an end fed slotted waveguide fixed aroundthefunnel of a ship well clear of deck superstructure and proud of the bridge etc.

Assuming a funnel diameter of 30feetthen the aerial will have a length of about 30 metres.

The waveguide is end fed as illustrated with a 10 nanosecond pulse supplied from a standard pulse generator arrangement, which pulse will cover only a tenth ofthe length ofthe aerial at any instant as it passes along the aerial. Thus, at any instant the aerial apertureisfilledwith onlya 3 metre iliumination,this being roughly equivalent at a wavelength of 3 cms (1 OG Hz) to a 1 degreebeamwidth.

The aerial thus transmits a very high speed rotating electron beam.

The radiating efficiency of the aerial array has to be relatively low to allow sufficient pulse power to be left to illuminate the last few metres of the aerial array along which the pulse passes. Thus, as illustrated in the drawing the aerial array is arranged with its feed end at the port bow direction ofthe ship such that maximum poweristransmittedforward of the ship.

Otherwise, by the use ofthe known expedient of suitably inclined slots the radiation power along the length of the aerial array can be set to give substantial- ly constant power.

Many different forms of conventional receiver aerial arrays can be used for the method ofthis invention, described above, for example a plurality of separate receiver horns circumferentially spaced aboutthe ship's funnel, with range and bearing being determined in known manner.

1. A method of providing a scanning radio beam, in which a transmitting aerial array is end fed with an energy pulse having a duration shorter than the transit time ofthe pulse along the array.

2. A method as claimed in Claim 1, in which the aerial array is circular.

3. A method as claimed in Claim 1 or Claim 2, in which the aerial array is constituted by a slotted waveguide.

4. A method of providing a scanning radio beam, substantially as hereinbefore described with refer ence to the drawing.

5. Apparatus for providing a scanning radio beam, comprising a fixed end fed aerial array, and means to feed to the array an energy pulse having a duration shorter than the transit time of the pulse along the array.

6. Apparatus as claimed in Claim 5, in which the aerial array is circular in plan.

7. Apparatus as claimed in Claim 5 or Claim 6, in which the aerial array is constituted by a slotted waveguide.

8. A marine radar system substantially as hereinbefore described with reference to the drawing.

Amendments to the claims have been filed, and have the following effect: Claims 1 to 6 above have been deleted.

New claims 1 to 6 have been filed.

CLAIMS 1. A method of providing a scanning radio beam, in which a curved transmitting aerial array is end fed with an energy pulse having a duration shorter than thetransittime ofthe pulsealong the array.

2. A method as claimed in Claim 1, in which the aerial array is circular.

3. A method as claimed in Claim 1 or Claim 2, in which the aerial array is constituted by a slotted waveguide.

4. A method of providing a scanning radio beam, substantially as herein before described with referpence to the drawing.

5. Apparatus for providing a scanning radio beam, comprising a fixed end fed curved aerial array, and means to feed to the array an energy pulse having a duration shorter than the transit time of the pulse along the array.

6. Apparatus as claimed in Claim 5, in which the aerial array is circular in plan.

The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Method of providing a scanning radio beam This invention relates two a method of providing a scanning radio beam as used,forexample, in primary and secondary radar, optical radar, anti sea clutter radar, ECCM radar, and navigation aids. Known methods of providing electronic beam scanning includefrequencyscanning using a dispersive antenna such as a slotted waveguide array as described in Chapter 4, Volume 2 of "Microwave Scanning Antennas" by R. C. Hansen; phase scanning as described in Chapter 3, Volume 2 ofthe above mentioned book; methods using a multiport array feeding a matrix as described at pages 11-66 and 11-67 of"Radar Handbook" (McGraw Hill 1970) edited by M. I. Skolnok; methods using a combination offastand slow frequency scanning to scan in both range and azimuth, in which methods the beam steering function is intimately related to the ranging function. These known methods suffer from the disadvan tagesthatthey require the use of complex and thus expensive apparatus for transmitting the radio beam, and that the size of the apparatus required limits the possibilities for use of the apparatus. According to this invention there is provided a method of providing a scanning radio beam, in which a transmitting aerial array is end fed with an energy pulse having a duration shorterthanthetransittime of the pulse along the array. The method of this invention has the advantage that it provides a very high speed scanning electron bunch which produces a beam, of azimuth width appropriate for use in a high resolution marine radar system, and such use will now be described byway of example with reference to the drawing which diagrammatically illustrates an aerial array mounted around a ship's funnel. The drawing illustrates a fixed aerial array circular in plan constituted by an end fed slotted waveguide fixed aroundthefunnel of a ship well clear of deck superstructure and proud of the bridge etc. Assuming a funnel diameter of 30feetthen the aerial will have a length of about 30 metres. The waveguide is end fed as illustrated with a 10 nanosecond pulse supplied from a standard pulse generator arrangement, which pulse will cover only a tenth ofthe length ofthe aerial at any instant as it passes along the aerial. Thus, at any instant the aerial apertureisfilledwith onlya 3 metre iliumination,this being roughly equivalent at a wavelength of 3 cms (1 OG Hz) to a 1 degreebeamwidth. The aerial thus transmits a very high speed rotating electron beam. The radiating efficiency of the aerial array has to be relatively low to allow sufficient pulse power to be left to illuminate the last few metres of the aerial array along which the pulse passes. Thus, as illustrated in the drawing the aerial array is arranged with its feed end at the port bow direction ofthe ship such that maximum poweristransmittedforward of the ship. Otherwise, by the use ofthe known expedient of suitably inclined slots the radiation power along the length of the aerial array can be set to give substantial- ly constant power. Many different forms of conventional receiver aerial arrays can be used for the method ofthis invention, described above, for example a plurality of separate receiver horns circumferentially spaced aboutthe ship's funnel, with range and bearing being determined in known manner. CLAIMS

1. A method of providing a scanning radio beam, in which a transmitting aerial array is end fed with an energy pulse having a duration shorter than the transit time ofthe pulse along the array.

2. A method as claimed in Claim 1, in which the aerial array is circular.

3. A method as claimed in Claim 1 or Claim 2, in which the aerial array is constituted by a slotted waveguide.

4. A method of providing a scanning radio beam, substantially as hereinbefore described with refer ence to the drawing.

5. Apparatus for providing a scanning radio beam, comprising a fixed end fed aerial array, and means to feed to the array an energy pulse having a duration shorter than the transit time of the pulse along the array.

6. Apparatus as claimed in Claim 5, in which the aerial array is circular in plan.

The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.

6. Apparatus as claimed in Claim 5, in which the aerial array is circular in plan.

7. Apparatus as claimed in Claim 5 or Claim 6, in which the aerial array is constituted by a slotted waveguide.

8. A marine radar system substantially as hereinbefore described with reference to the drawing.

Amendments to the claims have been filed, and have the following effect: Claims 1 to 6 above have been deleted.

New claims 1 to 6 have been filed.

1. A method of providing a scanning radio beam, in which a curved transmitting aerial array is end fed with an energy pulse having a duration shorter than thetransittime ofthe pulsealong the array.

2. A method as claimed in Claim 1, in which the aerial array is circular.

3. A method as claimed in Claim 1 or Claim 2, in which the aerial array is constituted by a slotted waveguide.

4. A method of providing a scanning radio beam, substantially as herein before described with referpence to the drawing.

5. Apparatus for providing a scanning radio beam, comprising a fixed end fed curved aerial array, and means to feed to the array an energy pulse having a duration shorter than the transit time of the pulse along the array.