Keeping mobile satellite TV antennas pointing in the right direction
Watching satellite TV at home is nothing remarkable, watching it in the back of a car on the road or boat at sea is. Keeping the antenna ('dish') of a satellite TV receiver pointing in the right part of the sky when its attached to your house is easy, your house usually stays in one place. Moving vehicles however can rotate in pitch, yaw and roll quite quickly and the antenna must be constantly driven to the same point in the sky regardless of the vehicle attitude, and quite accurately unless you like a fuzzy picture.
So how does the antenna know where to point?
By attaching gyroscopes which measure angular speed the antenna can determine the direction and velocity of vehicle rotation very accurately, allowing the azimuth and elevation servo-loops in the receiver to back this motion off. ALTHERIS' CRS03 single-axis angular rate gyroscopes are ideally suited to the job.
CRS03 contains a tiny solid state vibrating silicon ring which, through the magic of what's called the coriolis force principle, is able to detect very precisely the direction and speed of rotation and provide an analogue voltage feedback signal into the antenna servo loops. Smaller than a cubic inch and weighing less than an ounce, CRS03 can be attached to the latest slim antennas.
There are other gyros available on the open market, so why is CRS03 used so extensively in this application? Quite simply because its performance and affordability are unrivalled. Simpler vibrating mass or tuning fork gyros are prone to drift unpredictably with temperature and emit spurious output due to bumps, shocks and vibration. This translates to costly work by customers to compensate for these inaccuracies in their factory and also rectifying field failures due to the gyro. With its patented balanced vibrating ring design, and double closed loop control, the CRS03 gyro exhibits very little thermal drift, and when it does, it does it predictably. CRS03 is also immune to road vibration and shock.
