Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Radar mounted on and controls land vehicle
Reexamination Certificate
2000-07-31
2002-08-06
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Return signal controls external device
Radar mounted on and controls land vehicle
C342S073000, C342S074000, C342S081000, C342S368000
Reexamination Certificate
active
06429803
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a device which is adapted to be positioned in the path of a beam of electromagnetic radiation propagating in free space which changes characteristics of the beam. The invention is particularly, but not exclusively, concerned with microwave devices.
The term microwave refers to the part of the electromagnetic spectrum substantially in the frequency range 0.2 to 300 GHz. It includes that part of the spectrum referred to as millimetre wave (having a frequency in the range 30 to 300 GHz).
It is known from EP 0505040 to steer the direction of a microwave beam using a scanning device that comprises a body of ferrite material having a first magnetic coil along a first side of the body and a second magnetic coil along a second, opposite, side of the body. Each coil generates a magnetic field which passes through faces of the body. The device is configured such that magnetic field from each coil passes through the body in opposite directions. This causes a gradient in magnetisation across the body. The direction of the beam leaving the device is perpendicular to the gradient in the magnetic field across the body. Therefore the degree of deflection of the beam is controlled by the gradient in the magnetisation.
One application for such a device is in a control system for automatic or semi-automatic control of a vehicle. Such a control system comprises a radar system to determine location and speed of a vehicle relative to other vehicles and other objects or features, for example roadside furniture. This enables the control system to operate the vehicle automatically in cruise control and collision avoidance modes.
The radar system uses a microwave beam of narrow beam width having a half-power (3 dB) beam width of 2° to 4°. A narrow beam width is used in order that, when reflected from other vehicles, a relatively strong usable signal is available for processing. Furthermore, a narrow beam width is necessary for angular location of obstacles. Whilst a narrow beam width is useful for vehicle speeds which are normal for road travel, for example 15 to 100 km/hour, it is less useful for manoeuvring a vehicle at lower speeds, for example when parking, reversing, negotiating obstacles and the like. Because the beam width is narrow it provides wide coverage at some distance from the vehicle but at distances close to the vehicle, there are blind spots on either side of the beam. Obstacles in the blind spots will not be detected which may be hazardous if the vehicle is under automatic control. Furthermore, at low speeds, or when the vehicle is stationary, it is relatively easy for pedestrians or other vehicles to move into the blind spots and become hazards to an automatically controlled vehicle. Although it is possible to use a beam steering device such as the one described above to scan the beam horizontally from side to side to search for hazards, beam steering cannot scan beams through large angles and blind spots will still be present. For these reasons it has been proposed that certain control systems disable their radar detection means when the vehicle is stationary or moving at slow speed. The control systems activate again when the vehicle moves off from stationary and reaches a pre-determined speed or when the vehicle accelerates to the pre-determined speed.
SUMMARY OF THE INVENTION
According to a first aspect the invention provides a device for changing the divergence of a beam of electromagnetic radiation comprising a body having an electromagnetic aperture for the beam and magnetic means arranged to generate a magnetic gradient across the body which acts on the beam as it passes through the body, characterised in that the magnetic means acts on the electromagnetic aperture such that there is a differential phase delay over the electromagnetic aperture from a centre region to a periphery region of the electromagnetic aperture.
Preferably the magnitude of the phase delay in the central region may be greater than the magnitude of the phase delay at the periphery region. Alternatively, the magnitude of the phase delay in the central region may be less than the magnitude of the phase delay at the periphery region.
The aperture may comprise at least one sub-aperture induced by activation of the magnetic means. Each sub-aperture may have a boundary defined by the magnetic means.
According to a second aspect the invention provides a device for changing the divergence of a beam of electromagnetic radiation comprising a body having an electromagnetic aperture for the beam and magnetic means arranged to generate a magnetic gradient across the body arranged to act on the beam as it passes through the body characterised in that the magnetic means comprises at least one element, a sub-aperture associated with each element and each element defines a boundary of its associated of sub-aperture, and the magnetic means acts on the electromagnetic aperture such that there is a differential phase delay over the electromagnetic aperture from a centre region to a periphery region of the electromagnetic aperture
28
.
Preferably the magnetic means may be arranged to induce variations in the magnitude of magnetisation present across the aperture. The magnetic means may be arranged to induce variations in the magnitude of magnetisation present across each sub-aperture. For example, looking at a graph of magnetisation across the aperture or each sub-aperture there may be “kinks”, whether peaks or troughs, associated with each element of the magnetic means which is generating magnetic field. This applies whether an average value of gradient in magnetisation across the aperture has a positive or negative non-zero value or is zero. It may be these kinks which define the boundaries of the sub-apertures.
Preferably the magnetic means comprises one or more elongate sources of magnetic field. If there are a plurality of elongate sources, these may be disposed parallel to one another. Most preferably the magnetic means is one or more paths for carrying electric current. Conveniently the or each path is a metal wire. If there are a plurality of paths, current may travel in each path in a direction substantially parallel to the other paths. Alternatively current in some paths may travel in one direction and current in other paths may travel in an opposite direction. Current may travel in opposite directions in adjacent paths. Different amounts of current may be carried by adjacent paths.
Preferably the current carried by the or each path may be altered so as to change the magnitude of the magnetic field generated by the magnetic means and thus the magnetisation induced in the body. The current carried by the or each path may be switched on and off which may switch the beam between a wider beam width and a narrower beam width. Alternatively, the current may be varied in value between on and off states. As a result the degree of kinking in magnetisation across the aperture may be altered and the degree to which the device diverges or converges the beam (that is focusses or defocusses the beam) may also be altered. Individual paths (or groups of individual paths) may be controlled separately. For example, they may be switched on and off and varied independently of one another.
If the device is to diverge the beam in both azimuth and elevation directions, the magnetic means may be in the form of a grid comprising a first set of one or more elongate sources of magnetic field and a second set of one or more elongate sources of magnetic field in which the first set is orientated at an angle of greater than 0° relative to the second set. Preferably the first and second sets are orientated at 90° to each other. The magnitude of the magnetic field of the first and second sets of sources of magnetic field may be independently controllable in order to broaden the beam independently in azimuth and elevation directions.
The beam of radiation may be microwave radiation or may be millimeter wavelength radiation. Most preferably the beam of radiation is generated by a radar system.
BAE Systems Electronics Limited
Gregory Bernarr E.
Kirschstein et al.
LandOfFree
Magnetic beam deflection devices does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic beam deflection devices, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic beam deflection devices will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2913761