Line scan radar antenna using a single motor

• US 4,041,500 A
• Filed: 05/12/1976
• Issued: 08/09/1977
• Est. Priority Date: 05/12/1976
• Status: Expired due to Term

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Lapp, Roger H.
• Primary Examiner(s): Lieberman, Eli
• Application Number:
  US05/685,866
• Time in Patent Office: 454 Days
• Field of Search: 343/761, 343/763, 343/765, 343/766, 343/839, 343/781 P
• US Class Current: 343/761
• CPC Class Codes: H01Q 19/19 comprising one main concave reflecting surface associated with an auxiliary reflecting surface
• CPC Class Codes: H01Q 3/20 wherein the primary active element is fixed and the reflecting device is movable

Abstract

According to the present invention, radar rays are reflected off a rotatingecondary reflector which is both tilted with respect to and synchronously translated, in simple harmonic motion, in a direction transverse to the axis of rotation of the secondary reflector. The combined effect of the tilting and translating of the secondary reflector is to produce a line scan when the rays from the secondary reflector are reflected off a primary reflector.

Claims

1. A line scan radar antenna comprising:

a secondary reflector,

a motor,

a shaft coupling the motor to the secondary reflector, the axis of the shaft forming an angle α

with the axis of symmetry of the secondary reflector,

means affixed to the shaft for translating the shaft in a direction transverse to the axis of the shaft in response to the rotation of the motor and secondary reflector, and

a primary reflector which receives radar rays reflected off the secondary reflector and reflects them in a line scan.

2. A line scan radar antenna as defined in claim 1, wherein the translating means comprises:

a weight attached to the shaft and

a flat spring operably coupled to the shaft such that rotation of the shaft with the attached weight periodically flexes and unflexes the flat spring.

3. A line scan radar antenna as defined in claim 2 further comprising:

an attaching member which attaches the weight to the shaft,

radial adjustment means operably connected to the weight and the attaching member, permitting the weight to be moved radially toward and away from the shaft,

axial adjustment means connected to the attaching member and the shaft, permitting the attaching member with the attached weight to be moved axially along the shaft, and

phase difference adjustment means connected to the attaching member and the shaft permitting the weight and attaching member to be adjusted in rotational position with respect to the secondary reflector.

4. A line scan radar antenna as defined in claim 3, wherein:

the radial adjustment means comprises a collar means affixed to said weight, said means being slidable and stoppable along the attaching member, and

the axial adjustment means comprises a set screw arrangement slidable and stoppable along the shaft.

5. A line scan radar antenna as defined in claim 1 wherein the secondary reflector and primary reflector are curved.

6. A line scan radar antenna as defined in claim 1 wherein said translating means is affixed to the shaft so that said transverse direction is horizontal.

7. A method of line scanning a radar antenna comprising the steps:

rotating the shaft of a motor,

affixing a secondary reflector to the end of the shaft,

tilting the axis of symmetry of the secondary reflector to an angle α

with the axis of the shaft,

translating the secondary reflector in oscillatory fashion in a direction transverse to the direction of the shaft axis,

synchronizing the secondary reflector translation with the shaft rotation,

reflecting a radar ray off the tilted, rotating secondary reflector, to obtain a reflector ray which scans in a direction perpendicular to the transverse direction,

limiting the amount of translation to that required to cancel the angular displacement of the radar ray in the direction transverse to the shaft axis due to the tilt of the secondary reflector,

reflecting the ray from the secondary reflector into a primary reflector, and

reflecting a line scan pattern from the primary reflector.

8. A method of line scanning a radar antenna as defined in claim 7 wherein the translation of the secondary reflector comprises the steps:

attaching a weight to the rotating shaft,

coupling a flat spring to the shaft,

flexing the flat spring in response to the rotational position of the attached weight, and

translating the shaft and affixed secondary reflector in a direction transverse to the shaft axis in response to the flexion of the flat spring.

9. A method of line scanning a radar antenna as defined in claim 8, comprising the further steps:

positioning the direction of the transverse to the shaft axis to be horizontal, and

orienting the primary reflector and secondary reflector to produce a vertical line scan.

10. A method of line scanning a radar antenna as defined in claim 8, comprising the further steps:

selectively moving the weight radially toward and away from the shaft to control the magnitude of flat spring flexion and thus the magnitude of translation of the secondary reflector, and

sliding the weight axially along the shaft to control the torsional flexion of the flat spring and adjusting the weight in rotational position about the shaft to control the phase of translation of the flat spring.