Antenna beam pointing method for satellite mobile communications system

• US 5,241,319 A
• Filed: 04/19/1991
• Issued: 08/31/1993
• Est. Priority Date: 04/19/1990
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Shimizu, Ryuji
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US07/687,729
• Time in Patent Office: 865 Days
• Field of Search: 342/352, 342/357, 342/358, 342/359, 342/77, 342/76, 342/75
• US Class Current: 342/358
• CPC Class Codes: H01Q 1/3275 mounted on a horizontal surface of the vehicle, e.g. on roof, hood, trunk
• CPC Class Codes: H01Q 3/02 using mechanical movement of antenna or antenna system as a whole
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays

Abstract

A method for tracking a satellite in a land mobile satellite communications system is disclosed. A rate gyro is provided for use in the event that an automatic satellite tracking is prevented. The satellite is automatically tracked using a receive signal level if the receive signal level equals or exceeds a threshold. An output of the rate gyro is constantly compensated while automatically tracking the satellite. When the receive signal level falls below the threshold and the automatic satellite tracking becomes unable, the satellite is tracked using the compensated output of the rate gyro.

Claims

1. A method for tracking a satellite used in a land mobile satellite communications system, a rate gyro being used if an automatic satellite tracking is prevented, said method comprising the steps of:

(a) automatically tracking the satellite responsive to a receive signal level if the receive signal level equals or exceeds a threshold, said threshold indicating a signal level below which automatic satellite tracking cannot be carried out;

(b) compensating for first and second rate gyro output factors while automatically tracking the satellite, said first rate gyro output factor being a voltage offset factor by which a voltage offset of the rate gyro output is corrected, and said second rate gyro output factor being a scale factor for converting the rate gyro output into a rate gyro indicating an antenna angular velocity, said rate gyro being compensated in response to said first rate gyro output factor; and

(c) tracking the satellite using the output of the rate gyro if the receive signal level falls below the threshold indicating that the automatic satellite tracking is unable.

2. A method as claimed in claim 1, where in step (b) includes the steps of:

(d) acquiring an output of a counter, the output of the counter indicating an antenna angular position;

(e) determining an antenna angular velocity in response to the output of the counter;

(f) changing a value of said first rate gyro output factor to be equal to the rate gyro output if the antenna angular velocity is detected zero; and

(g) determining a value of said second rate gyro output factor in response to said antenna angular velocity, said rate gyro output and said first rate gyro output factor.

3. A method for tracking a satellite used in a land mobile satellite communications system, a rate gyro being used if an automatic satellite tracking is prevented, said method comprising the steps of:

(a) automatically tracking the satellite by using the receive signal level if the receive signal level equals or exceeds a threshold;

(b) acquiring an output of a counter while automatically tracking the satellite, the output of the counter indicating an antenna angular position;

(c) determining an antenna angular velocity by using the output of the counter obtained at step (b);

(d) setting a value of a first rate gyro output factor to be equal to the rate gyro output if the antenna angular velocity is detected zero, said first rate gyro output factor being a voltage offset factor by which a voltage offset of the rate gyro output is corrected; and

(e) determining a value of a second rate gyro output factor using said antenna angular velocity, said rate gyro output and said first rate gyro output factor, said second rate gyro output factor being a scale factor for converting the rate gyro output, compensated for by said first rate gyro output factor, into a rate gyro indicating antenna angular velocity.