DESC:FORM – 2

THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(SEE SECTION 10, RULE 13)

ANTENNA POSITIONING SYSTEM AND METHOD THEREFOR

BHARAT ELECTRONICS LIMITED
WITH ADDRESS:
OUTER RING ROAD, NAGAVARA, BANGALORE 560045, KARNATAKA, INDIA

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

TECHNICAL FIELD
[0001] The present invention relates to antenna positioning/pointing.
BACKGROUND
[0002] Access to communication services such as data and voice at all times and in all places has now become a necessity. At places without any terrestrial communication infrastructure, satellite based communication systems are the only mode of accessing communication services. Previously, communication was largely stationary between communication stations and there was no concept of communication on the move. However, increasing demand for mobile applications covering land, maritime, and aeronautical environments has pushed the development of Satellite/Satcom On The Move Terminals. The basic principle behind Satcom On The Move is that a vehicle equipped with a satellite antenna establishes communication with a satellite and maintains that communication while the vehicle is moving. For such applications, the mobility of ground terminals on the vehicle and the positioning of the antenna at a desired angle presents a significant challenge in complying with the requirements of pointing accuracy.
[0003] United States Patent 6195060 mentions an antenna positioner control system and related method, where servomotors of the antenna are driven and controlled through current acceleration loops, tachometer rate loops, elevation position loops. US6195060 thus refers to an open loop method which uses the known position of the satellite to orient the antenna and to reorient the antenna based on its current heading.
[0004] There is therefore felt a need of an invention which solves the above defined problems and provides an effective method for positioning the antenna at a desired angle, stabilize the antenna and track the satellite to maintain the communication link with the satellite without any break while on the move.

SUMMARY
[0005] This summary is provided to introduce concepts of the invention related to an antenna positioning system and method therefor, as disclosed herein. This summary is neither intended to identify essential features of the invention as per the present invention nor is it intended for use in determining or limiting the scope of the invention as per the present invention.
[0006] In accordance with an exemplary implementation of the present invention, there is provided an antenna positioning system for satellite tracking. The system comprises: a GPS unit configured to detect a location of an antenna; an inertial measurement unit in communication with the GPS unit, configured to detect an inertial position of a platform having the antenna mounted thereon; a radio frequency (RF) receiver configured to detect signal strength of an RF signal received by the antenna from a satellite; a motor control unit configured to control angular displacement of the antenna; and an antenna control unit in communication with the inertial measurement unit, the RF receiver and the motor control unit, the antenna control unit configured to: determine an initial angular position for the antenna corresponding to the location of the antenna and the inertial position of the platform, and communicate the initial angular position to the motor control unit for angularly displacing the antenna to the initial angular position; and determine a subsequent angular position for the antenna corresponding to the RF signal strength of a threshold value, and communicate the subsequent angular position to the motor control unit for angularly displacing the antenna to the subsequent angular position.
[0007] In an embodiment, the system includes a pedestal position sensor configured to detect the position of a pedestal of the antenna along an azimuth axis and an altitude axis; and the antenna control unit is configured to determine the angular positions for the antenna corresponding to the position of the pedestal.
[0008] In an embodiment, the RF receiver is configured to periodically detect signal strength of the RF signal received by the antenna from the satellite; and the antenna control unit is configured to periodically determine subsequent angular positions for the antenna corresponding to RF signal strength of the threshold value, and periodically communicate the subsequent angular positions to the motor control unit for angularly displacing the antenna to the subsequent angular positions, for tracking the satellite.
[0009] In accordance with another exemplary implementation of the present invention, there is provided a method for positioning an antenna for satellite tracking. The method comprises: detecting, by a GPS unit, a location of the antenna, and by an inertial measurement unit, an inertial position of a platform having the antenna mounted thereon; determining, by an antenna control unit, an initial angular position for the antenna corresponding to the location of the antenna and the inertial position of the platform; angularly displacing, by a motor control unit, the antenna to the initial angular position; detecting, by a radio frequency (RF) receiver, signal strength of an RF signal received by the antenna from a satellite; determining, by the antenna control unit, a subsequent angular position for the antenna corresponding to the RF signal strength of a threshold value; and angularly displacing, by the motor control unit, the antenna to the subsequent angular position.
[0010] In an embodiment, the location of the antenna includes a latitude and a longitude of the antenna, the inertial position of the platform includes Pitch, Roll and Yaw of the platform, the initial angular position includes an azimuth angle and an altitude angle for the antenna, and the subsequent angular position includes an azimuth angle and an altitude angle of the antenna.
[0011] In an embodiment, the steps of determining the angular positions for the antenna include detecting, by a pedestal position sensor, the position of a pedestal of the antenna along an azimuth axis and an altitude axis.
[0012] In an embodiment, the method includes periodically repeating the steps onwards from detecting the signal strength of the RF signal received by the antenna from the satellite, for tracking the satellite.
[0013] In an embodiment, the RF signal strength is detected by angularly displacing the pedestal of the antenna.
[0014] In an embodiment, the method, after the step of angularly displacing the antenna to the initial angular position, includes the step of selectively detecting either, the signal strength of the RF signal received by the antenna from the satellite, or the location of the antenna and the inertial position of the platform.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[0015] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and modules.
[0016] Figure 1 illustrates a block diagram depicting an antenna positioning system, according to an exemplary implementation of the present invention.
[0017] Figure 2 illustrates a flow chart depicting the steps involved in implementing an antenna positioning method by the antenna positioning system illustrated in Figure 1.
[0018] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative methods embodying the principles of the present invention. Similarly, it will be appreciated that any flow charts, flow diagrams, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.
DETAILED DESCRIPTION
[0019] The various embodiments of the present invention describe about an antenna positioning system and a method therefor.
[0020] In the following description, for purpose of explanation, specific details are set forth in order to provide an understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these details. One skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into a number of systems.
[0021] However, the systems and methods are not limited to the specific embodiments described herein. Further, structures and devices shown in the figures are illustrative of exemplary embodiments of the present invention and are meant to avoid obscuring of the present invention.
[0022] It should be noted that the description merely illustrates the principles of the present invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present invention. Furthermore, all examples recited herein are principally intended expressly to be only for explanatory purposes to help the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.
[0023] The main consideration in designing the antenna positioning system was how to acquire the satellite and then keep tracking it. To achieve the same, the antenna positioning system is designed to implement the hybrid method involving three tracking modes namely open loop, closed loop and combination of both open and closed loops i.e. hybrid.
[0024] Open loop tracking involves orienting an antenna in the direction of the satellite without incorporating any RF signal strength measurements for controlling the orientation. Closed-loop tracking incorporates RF signal strength feedback measurements for controlling the orientation.
[0025] Referring to figure 1, a block diagram depicting the antenna positioning system for satellite tracking, according to an exemplary implementation of the present invention, is illustrated. The antenna positioning system (100) comprises an antenna control unit (101), a motor control unit (102), an inertial measurement unit (IMU) (103), a GPS unit (104) and a radio frequency (RF) receiver (106). The GPS unit (104) is configured to detect a location of an antenna (105) in terms of latitude and longitude of the antenna. The inertial measurement unit (103) is in communication with the GPS unit (104) and is configured to detect an inertial position or attitude of a platform having the antenna (105) mounted thereon. The platform can be a vehicle such as truck, van or any other similar commercial vehicle whose inertial position or attitude in terms of Pitch, Roll and Yaw is detected by the IMU (103) by means of hemispherical resonating gyroscopic (HRG) sensors included in the IMU. The RF receiver (106) is configured to detect signal strength of an RF signal received by the antenna (105) from a satellite. The motor control unit (102) is configured to control angular displacement of the antenna (105).
[0026] The antenna control unit (101) is in communication with the inertial measurement unit (103), the RF receiver (106) and the motor control unit (102). The antenna control unit (101) governs the motion of a servo-mechanical pedestal (not particularly shown) in the antenna (105). Data from a pedestal position sensor (not particularly shown) regarding the position of the pedestal along an azimuth axis and an altitude axis as well as data from the inertial measurement unit (IMU) (103) regarding the inertial state of a platform/vehicle on which the antenna (105) the mounted and the location of the antenna detected by the GPS unit (104), are input to the antenna control unit (101) which computes and determines an initial angular position in terms of azimuth and altitude angles for the antenna (105) based on the data. The antenna control unit (101) provides position command(s) based on the initial angular position to the motor control unit (102) which in turn outputs voltage(s) that drive a plurality of DC motors, such as azimuth motor, elevation motor, and the like, in the pedestal to angularly displace pedestal and hence the antenna (105) to the initial angular position.
[0027] Further, the antenna control unit (101) also interfaces RF signal strength measurement received from the RF receiver (106) which is used for positioning the antenna (105). Typically, the RF signal strength is measured by moving the servo-mechanical pedestal minimally in left/right/up/down directions through very fine degrees of adjustment, and stopping when maximum RF signal strength is detected, i.e. when the RF signal strength is at or above a predefined threshold value. The antenna control unit (101) determines a subsequent angular position in terms of azimuth and altitude angles for the antenna (105) when the RF signal strength is above the predefined threshold value, and provides position commands based on the subsequent angular position to the motor control unit (102) which in turn outputs voltage(s) that drive the DC motors to angularly displace the pedestal and hence the antenna (105) to the subsequent angular position. The voltage outputs to the pedestal motors are governed by feedback control loops may be open or closed loops or combination of both the loops, that are implemented as a part of the overall positioning strategy through the hybrid tracking method.
[0028] Typically, the RF receiver (106) periodically detects the RF signal strength, and the antenna control unit (101) periodically determines a subsequent angular position in terms of azimuth and altitude angles for the antenna (105) when the RF signal strength is above the predefined threshold value, and periodically provides position commands based on the subsequent angular position to the motor control unit (102) which in turn outputs voltage(s) that drive the DC motors to angularly displace the pedestal and hence the antenna (105) to the subsequent angular position, for tracking the satellite.
[0029] In open loop tracking mode, the antenna control unit (101) uses satellite information regarding the known position of the satellite to orient the antenna (105) and to re-orient the antenna (105) based on its current heading. IMU (103) measurements are used to steer the antenna (105) to a new position.
[0030] In closed loop tracking mode, the antenna (105) seeks the orientation that maximizes the receiver signal (RF based step scan feedback). This requires scanning of the antenna across the sky. Scanning is accomplished through step tracking by the antenna control unit (101).
[0031] In hybrid tracking mode, the antenna control unit (101) uses both open loop and closed loop mode. In hybrid mode, the antenna (105) is first aligned to the satellite using the open loop mode and then closed loop mode i.e. step tracking is used to track the satellite.
[0032] A flow chart depicting the steps involved in implementing the antenna positioning method by the antenna positioning system (100) is illustrated in figure 2. The antenna positioning is done in three stages. First stage is tracking which is done through an inner loop that provides feedback of the position of the motors detected by the pedestal position sensors. Second stage is stabilization which is done through an outer loop and involves use of the IMU (103) which measures the vehicle disturbance i.e. roll, pitch and yaw on the basis of data received from the GPS unit (104). IMU (103) provides feedback to the antenna control unit (101) which compensates the disturbances and computes new values of angular positions in terms of azimuth and elevation angles for the antenna. Third stage is positioning where RF signal strength is used to determine subsequent angular positions in terms of azimuth and elevation angles to orient the antenna in the direction the subsequent angular position where the RF signal strength is maximum.
[0033] Thus, the antenna positioning method implemented by the antenna positioning system (100) includes the steps of detecting the location of the antenna (105) and an inertial position of the platform/vehicle having the antenna (105) mounted thereon, determining the initial angular position for the antenna (105) corresponding to the location of the antenna and the inertial position of the platform/vehicle, angularly displacing the antenna (105) to the initial angular position, detecting signal strength of the RF signal received by the antenna (105) from the satellite, determining the subsequent angular position for the antenna (105) corresponding to the RF signal strength of the threshold value, angularly displacing the antenna (105) to the subsequent angular position.
[0034] The method, after angularly displacing the antenna (105) to the initial angular position, involves selecting either the step of detecting the signal strength of the RF signal received by the antenna (105) from the satellite or the step of detecting the location of the antenna (105) and the inertial position of the platform/vehicle.
[0035] The method includes repeating the steps of, detecting signal strength of the RF signal received by the antenna (105) from the satellite, determining the subsequent angular position for the antenna (105) corresponding to the RF signal strength of the threshold value, angularly displacing the antenna (105) to the subsequent angular position, for tracking the satellite.
[0036] In accordance with the method, the location of the antenna (105) includes latitude and longitude of the antenna, the inertial position of the platform includes Pitch, Roll and Yaw of the platform/vehicle, and the initial as well as subsequent angular positions include azimuth and altitude angles for the antenna (105).
[0037] In accordance with the method, the steps of determining the angular positions for the antenna (105) include detecting the position of the pedestal of the antenna (105) along azimuth axis and altitude axis.
[0038] In accordance with the method, the RF signal strength is detected by angularly displacing the servo-mechanical pedestal of the antenna (105) minimally in left/right/up/down directions through very fine degrees of adjustment.
[0039] In an exemplary aspect, it was observed that by implementing the antenna positioning method without the RF feedback i.e. with only open loop, the positioning accuracy achieved was +/- 0.5 deg during cross country drive. However, by implementing the antenna positioning method with RF feedback in addition to the open loop, the positioning accuracy achieved was less than +/- 0.2 deg.
[0040] Thus, at least some of the technically advanced aspects of the antenna positioning system and method according to the present invention are as follows:
the antenna positioning system implements a hybrid method for satellite tracking involving both open loop and closed loop tracking modes for dynamically orienting and positioning the antenna in the direction of the satellite;
the hybrid method for satellite tracking implemented by the antenna positioning system includes open loop tracking with periodic closed loop updates to correct for drifting of the inertial system;
the antenna positioning system combines the use of hemispherical resonating gyroscopic (HRG) sensors with RF based step scan feedback, wherein the gyros compensate for fast vehicle motion (open loop), the lower bandwidth RF tracking corrects for the low rate/DC drift errors associated with the ephemeris and gyro sensors (closed loop); and
the hybrid method for satellite tracking implemented by the antenna positioning system, combines the two tracking modes to minimize the tracking scan-loss and to maintain the pointing accuracy.
[0041] Thus, the antenna positioning system and method in accordance with the present invention performs the complex task of not only positioning the antenna to the desired angle and stabilizing the antenna by cancelling out the disturbance caused by motion of the platform/vehicle but also additionally uses RF Signal strength to maintain the communication link with the satellite without any break while on the move.
[0042] The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the invention
,CLAIMS:WE CLAIM:

1. An antenna positioning system (100) for satellite tracking, the system (100) comprising:
a GPS unit (104) configured to detect a location of an antenna (105);
an inertial measurement unit (103) in communication with said GPS unit (104), configured to detect an inertial position of a platform having said antenna (105) mounted thereon;
a radio frequency (RF) receiver (106) configured to detect signal strength of an RF signal received by said antenna (105) from a satellite;
a motor control unit (102) configured to control angular displacement of said antenna (105); and
an antenna control unit (101) in communication with said inertial measurement unit (103), said RF receiver (106) and said motor control unit (102), said antenna control unit (101) configured to:
determine an initial angular position for said antenna (105) corresponding to the location of said antenna and the inertial position of said platform, and communicate said initial angular position to said motor control unit (102) for angularly displacing said antenna to the initial angular position; and
determine a subsequent angular position for said antenna (105) corresponding to the RF signal strength of a threshold value, and communicate said subsequent angular position to said motor control unit (102) for angularly displacing said antenna to the subsequent angular position.

2. The antenna positioning system as claimed in claim 1, wherein,
said system includes a pedestal position sensor configured to detect the position of a pedestal of said antenna (105) along an azimuth axis and an altitude axis; and
said antenna control unit (101) is configured to determine said angular positions for said antenna (105) corresponding to the position of said pedestal.

3. The antenna positioning system as claimed in claim 10, wherein,
said RF receiver (106) is configured to periodically detect signal strength of the RF signal received by said antenna (105) from said satellite; and
said antenna control unit (101) is configured to periodically determine subsequent angular positions for said antenna (105) corresponding to RF signal strength of the threshold value, and
periodically communicate said subsequent angular positions to said motor control unit (102) for angularly displacing said antenna to the subsequent angular positions, for tracking said satellite.

4. A method for positioning an antenna (105) for satellite tracking, the method comprising:
detecting, by a GPS unit (104), a location of the antenna (105), and by an inertial measurement unit (103), an inertial position of a platform having the antenna (105) mounted thereon;
determining, by an antenna control unit (101), an initial angular position for the antenna (105) corresponding to the location of the antenna and the inertial position of the platform;
angularly displacing, by a motor control unit (102), the antenna (105) to the initial angular position;
detecting, by a radio frequency (RF) receiver (106), signal strength of an RF signal received by the antenna (105) from a satellite;
determining, by the antenna control unit (101), a subsequent angular position for the antenna (105) corresponding to the RF signal strength of a threshold value; and
angularly displacing, by the motor control unit (102), the antenna (105) to the subsequent angular position.

5. The method for positioning the antenna as claimed in claim 4, wherein the location of the antenna (105) includes a latitude and a longitude of the antenna.

6. The method for positioning the antenna as claimed in claim 4, wherein the inertial position of the platform includes Pitch, Roll and Yaw of the platform.

7. The method for positioning the antenna as claimed in claim 4, wherein the initial angular position includes an azimuth angle and an altitude angle for the antenna (105).

8. The method for positioning the antenna as claimed in claim 4, wherein the subsequent angular position includes an azimuth angle and an altitude angle of the antenna (105).

9. The method for positioning the antenna as claimed in claim 4, wherein the steps of determining said angular positions for the antenna (105) include detecting, by a pedestal position sensor, the position of a pedestal of the antenna (105) along an azimuth axis and an altitude axis.

10. The method for positioning the antenna as claimed in claim 4, wherein the method includes periodically repeating the steps onwards from detecting the signal strength of the RF signal received by the antenna (105) from the satellite, for tracking the satellite.

11. The method for positioning the antenna as claimed in claims 4 to 10, wherein the RF signal strength is detected by angularly displacing the pedestal of the antenna (105).

12. The method for positioning the antenna as claimed in claims 4 to 11, wherein the method, after the step of angularly displacing the antenna (105) to the initial angular position, includes the step of selectively detecting either,
the signal strength of the RF signal received by the antenna (105) from the satellite, or
the location of the antenna (105) and the inertial position of the platform.

Dated this 22nd day of March, 2019

FOR BHARAT ELECTRONICS LIMITED

(By their Agent)

D. MANOJ KUMAR (IN/PA-2110)
KRISHNA & SAURASTRI ASSOCIATES LLP