Continuous wave doppler system with suppression of ground clutter
First Claim
1. A Doppler signal system comprising at least one fixed transmitter, a moving platform having first and second antennas mounted thereon and spaced apart from each other on said platform to receive signals transmitted from said transmitter and reflected from moving targets and reflected from fixed structure, and a discriminator operable to distinguish target signals reflected from moving targets from clutter signals in response to the phase difference between Doppler signals received by said first and second antennas being not substantially equal to a phase difference value determined to be the phase difference for clutter signals, said phase difference value for clutter signals being determined from a predetermined function expressing said phase difference value as a linear variation with the Doppler frequency of said signals.
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Abstract
In a continuous wave Doppler system in which a fixed transmitter transmits a continuous wave signal to be reflected by moving targets and by fixed structure, an aircraft receives the reflective signals at two spaced apart antennas. The signals reflected from moving targets are distinguished from ground clutter reflected from fixed structure by the phase difference between the Doppler signals receive by the two antennas. The signals reflected from moving targets are distinguished from the ground clutter in response to the phase difference between the Doppler signals received by the two antennas being not equal to a phase difference value determined to be the phase difference for clutter signals. The phase difference value for clutter signals is determined from a function expressing the phase difference value as a linear variation with the Doppler frequency of the signals.
22 Citations
13 Claims
- 1. A Doppler signal system comprising at least one fixed transmitter, a moving platform having first and second antennas mounted thereon and spaced apart from each other on said platform to receive signals transmitted from said transmitter and reflected from moving targets and reflected from fixed structure, and a discriminator operable to distinguish target signals reflected from moving targets from clutter signals in response to the phase difference between Doppler signals received by said first and second antennas being not substantially equal to a phase difference value determined to be the phase difference for clutter signals, said phase difference value for clutter signals being determined from a predetermined function expressing said phase difference value as a linear variation with the Doppler frequency of said signals.
- 9. A method of distinguishing Doppler signals reflected from moving targets from clutter signals comprising receiving reflected signals with two antennas on a platform spaced apart along an axis generally parallel to the motion of said platform, and determining that signals are reflected from moving targets in response to the phase difference between the signals received by said antennas being not substantially equal to a phase difference value determined to be the difference for clutter signals, the phase difference value for clutter signals being determined from a predetermined function expressing said phase difference value as a linear variation with the Doppler frequency of said signals.
Specification