Communications: radio wave antennas – Antennas – Measuring signal energy
Reexamination Certificate
2000-06-01
2001-12-11
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Measuring signal energy
C343S713000, C340S903000, C342S174000
Reexamination Certificate
active
06329952
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a test system used to align the boresite of a radar antenna. More particularly, the present invention relates to a test system that is used to align the boresite of an automotive radar system antenna with a mechanical reference (e.g., the thrust vector) from a vehicle on which the radar is mounted.
2. Description of the Related Art
Recently, manufacturers have begun producing radar systems for automobiles. Such systems have been used in combination with a vehicle cruise control to form an automotive radar system. An automotive radar system transmits a signal from an antenna typically located in the grill area of an automobile. The presence of and distance to an object from the automotive radar antenna is determined from the signal reflected by the object. If an object is detected in the path of the vehicle, wheel braking or engine deceleration is applied by the automotive radar system to maintain a desired distance from the object and to prevent the vehicle from striking the object.
To assure proper performance of a automotive radar system, the device must be regularly tested. During testing, proper alignment of the automotive radar antenna boresite angle with a mechanical reference line, such as a thrust vector of the vehicle which identifies the forward direction of travel of the vehicle, must be achieved. An automotive radar antenna boresite may become misaligned due to vehicle vibrations, vehicle collisions, or other factors. The boresite angle must be properly aligned to prevent the radar system from encountering false or inaccurate readings from signals received from vehicles in adjacent lanes, and to ensure proper detection of vehicles or objects in the immediate lane.
To align the boresite of the automotive radar antenna for FM-CW and Pulse modulated radar systems, a Doppler shifted signal is not generally required for the radar. A passive trihedral target reflector may be used for testing and mechanically aligned at a point in space along the vehicle thrust vector. With the trihedral target so aligned, the position and orientation of the antenna are set to maximize the energy reflected back to the automotive radar from the trihedral target.
Frequency shift keying (FSK) modulated radars require a Doppler shift in order for the radar to respond. To align the FSK radar along the vehicle thrust vector, either the vehicle must be moving relative to a trihedral target, or the target moving, and the antenna aligned to maximize reflected energy.
U.S. Pat. Application Ser. No. 09/252,492 discloses use of interferometers in combination with a transponder to perform alignment. The interferometers enable a display reading to be provided from the transponder so that an operator can align the boresite of the automotive antenna with the thrust vector of a vehicle using the display. The transponder also provides a return signal to the automotive radar to simulate an object at a desired distance from the automotive radar. The transponder can provide a Doppler shift enabling FSK modulated, as well as other types of modulated radar signals to be tested.
SUMMARY OF THE INVENTION
In accordance with the present invention, a transponder attached to a laser alignment fixture is used to align an automotive radar antenna boresite with the thrust vector of the vehicle. Reflectors are attached to the alignment fixture for initial alignment using two laser beams. The transponder verifies the performance of the automotive radar by simulating a target radar return at a desired distance. A reading from the automotive radar processor is used by an operator, for final alignment, so interferometer antennas and associated display in the transponder are not needed.
To align the automotive radar, the transponder is first positioned along the thrust vector of the automobile using a first laser beam aligned perpendicular to a wheel axle. The first laser beam is aligned when transmitted from a fixture attached to the wheel axle onto a first piece of reflective material attached to the alignment fixture supporting the transponder.
To further align the transponder antenna with the centerline of the automotive radar antenna, a second laser, aligned with a centerline of the automotive radar antenna, is provided to remove azimuth and elevation translation errors (&Dgr;x) and (&Dgr;y) between the transponder antenna and the automotive radar antenna. The second laser beam is aligned when transmitted from the vehicle near the automotive radar antenna onto a second piece of reflective material attached to the alignment fixture supporting the transponder.
The transponder provides a return signal in response to the automotive radar signal used to zero an angle (&agr;) between the electrical boresite of the automotive radar antenna and the boresite of the transponder antenna. The angle (&agr;) between the boresite of the automotive radar antenna and the transponder antenna is set to zero by adjusting the automotive radar antenna position until a signal processor provided in the automotive radar indicates the angle a is zero.
In the transponder, the RF signal from the automotive radar is downconverted to an IF signal. The IF signal is then delayed a desired amount and then upconverted for retransmission to the automotive radar. The retransmitted signal enables the transponder to simulate a target spaced a desired distance from the automotive radar. A Doppler offset can be provided during upconversion of the IF signal to simulate a target moving at a desired rate of speed relative to the automotive radar. Such a Doppler shift enables a FSK modulated automotive radar system to be tested along with other systems.
REFERENCES:
patent: 4041494 (1977-08-01), Ewen et al.
patent: 5111210 (1992-05-01), Morse
patent: 5313213 (1994-05-01), Neumann et al.
patent: 5314037 (1994-05-01), Shaw et al.
patent: 5646612 (1997-07-01), Byon
patent: 5977906 (1999-11-01), Ameen et al.
patent: PCT/DE97/02828 (1997-12-01), None
patent: 197 07 590 A1 (1998-09-01), None
patent: 9300071 (1995-04-01), None
Anritsu Company
Fliesler Dubb Meyer & Lovejoy LLP
Nguyen Hoang
Wong Don
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