RF attitude measurement system and method

A system for tracking the attitude of a rotating projectile, comprising:

• a transmit system mounted on the projectile, the system including first and second linearly polarized transmit antennas spaced apart by a distance d on the projectile, a first transmitter coupled to the first antenna for transmitting a first transmit signal at a first frequency, a second transmitter coupled to the second antenna for transmitting a second transmit signal at a second frequency, wherein said first frequency is different from said second frequency, and said first transmit signal and said second transmit signal are in phase coherency;
• a receiver system located on the projectile's launch platform, the receiver system including a linearly polarized receive antenna system for receiving said first transmit signal and said second transmit signal, a first receiver section for receiving and downconverting said first transmit signal to provide a first receiver signal, and a second receiver section for receiving and downconverting said second transmit signal to provide a second receiver signal;
• a sampler that samples the first and second receiver signals approximately ninety degrees out of phase to provide third and fourth receiver signals;
• and
• a processor responsive to said first, second, third and fourth receiver signals for calculating a roll angle, a pitch angle and a yaw angle.

A system for controlling a rotating projectile launched from a platform onto a target, comprising:

• A launch platform for launching a rotating projectile towards a target, said platform comprising a tracking antenna for tracking the projectile to maintain a line of sight;
• a projectile having a flight control mechanism mounted thereon, and a command receiver for controlling deployment of the flight control mechanism in response to command signals;
• a transmit system mounted on the projectile, the system including first and second linearly polarized transmit antennas spaced apart by a distance d′ on the projectile and third and fourth transmit antennas spaced apart by a distance d″ on the projectile, first and second transmitters coupled to the first and second transmit antennas for transmitting first and second transmit signals in phase coherency at first and second different frequencies, third and fourth transmitters coupled to the third and fourth transmit antennas for transmitting third and fourth transmit signals in phase coherency at third and fourth different frequencies;
• a receiver system located on the launch platform, the receiver system including a linearly polarized receive antenna system and receiver sections for receiving and downconverting said first, second, third and fourth transmit signals to provide first, second, third and fourth receiver signals;
• and
• a flight controller responsive to said receiver system for controlling the projectile in flight, the flight controller adapted to calculate a roll angle, a yaw angle and a pitch angle of said projectile while in flight from said first, second, third and fourth receiver signals and generate a command signal at an appropriate time in dependence on said roll, yaw and pitch angles, said flight controller further including a command transmitter for transmitting said command signal to said projectile.

A system for controlling a rotating projectile launched from a platform onto a target, comprising:

• A launch platform for launching a rotating projectile towards a target, said platform comprising a tracking antenna for tracking the projectile to maintain a line of sight;
• a projectile having a flight control mechanism mounted thereon, and a command receiver for controlling deployment of the flight control mechanism in response to command signals;
• a transmit system mounted on the projectile, the system including first and second linearly polarized transmit antennas spaced apart by a distance d on the projectile, a first transmitter coupled to the first antenna for transmitting a first transmit signal at a first frequency, a second transmitter coupled to the second antenna for transmitting a second transmit signal at a second frequency, wherein said first frequency is different from said second frequency, and said first transmit signal and said second transmit signal are in phase coherency;
• a receiver system located on the projectile's launch platform, the receiver system including a linearly polarized receive antenna system for receiving said first transmit signal and said second transmit signal, a first receiver section for receiving and downconverting said first transmit signal to provide a first receiver signal, and a second receiver section for receiving and downconverting said second transmit signal to provide a second receiver signal, and a sampler that samples the first and second receiver signals approximately ninety degrees out of phase to provide third and fourth receiver signals;
• and
• a flight controller responsive to said receiver system for controlling the projectile in flight, the flight controller adapted to calculate a roll angle, a yaw angle and a pitch angle of said projectile while in flight from said first, second, third and fourth receiver signals and generate a command signal at an appropriate time in dependence on said roll, yaw and pitch angles, said flight controller further including a command transmitter for transmitting said command signal to said projectile.

A method for tracking the attitude of a rotating projectile, comprising:

• transmitting first and second linearly polarized transmit signals in phase coherency at first and second different frequencies from positions spaced apart by a distance d′ on the projectile;
• transmitting third and fourth linearly polarized transmit signals in phase coherency at third and fourth different frequencies from positions spaced apart by a distance d″ on the projectile;
• receiving and downconverting said first, second, third and fourth transmit signals at the projectile's launch platform to provide first, second, third and fourth receiver signals;
• and
• processing said first, second, third and fourth receiver signals to calculate a roll angle, a pitch angle and a yaw angle.