Rotor tip synthetic aperture radar

Claim 2

A rotor tip synthetic aperture radar comprising: a rotor operable to rotate; a first receiver positioned at a first location in said rotor for receiving target reflected microwave signals; a transmitter positioned at a second location including means for generating and transmitting microwave signals towards a target; said first receiver including means for amplifying said received microwave signals and for retransmitting said amplified microwave signals to a second receiver positioned at said second location; said second receiver including means for extracting information from said amplified microwave signals; first means for generating a pilot signal having a first predetermined frequency positioned at said second location and for transmitting said pilot signal to a second means positioned at said first location for receiving said pilot signal, multiplying its frequency and retransmitting said multiplied pilot signal to said second location; third means at said second location for receiving and multiplying the frequency of said received pilot signal to provide a first signal; fourth means for mixing said first signal with a second predetermined frequency to provide a second signal; and fifth means for mixing said second signal with said amplified microwave signals received by said second receiver to cancel first order doppler frequency shifts of said amplified microwave signals in passing from said first location to said second location.

Claim 3

The rotor tip synthetic aperture radar of claim 1 wherein said first means for generating a pilot signal includes means for generating a coherent pilot signal with respect to the transmitted microwave signals.

Claim 4

The rotor tip synthetic aperture radar of claim 1 wherein said second location is within the cab of a helicopter.

Claim 5

The rotor tip synthetic aperture radar of claim 1 wherein said second position is on a mast mounted on the hub which rotates and supports the rotor.

Claim 6

The rotor tip synthetic aperture radar of claim 1 wherein said first predetermined frequency is 1 GHz.

Claim 7

The rotor tip synthetic aperture radar of claim 1 wherein said multiplied pilot signal has a frequency of 2 GHz.

Claim 8

The rotor tip synthetic aperture radar of claim 1 wherein said transmitted microwave signals are at 16 GHz.

Claim 9

The synthetic aperture radar of claim 1 wherein said third means for receiving and multiplying includes multiplying by 4.

Claim 10

The synthetic aperture radar of claim 1 wherein said fourth means for mixing with a predetermined frequency includes mixing with a predetermined frequency of 7 GHz.

Claim 11

A bistatic synthetic aperture radar comprising: a first receiver for receiving target reflected microwave signals; a transmitter for generating and transmitting microwave signals towards a target; said first receiver spaced apart from said transmitter at first and second locations respectively and including means for moving said first receiver at said first location with respect to said transmitter at said second location; said first receiver including means for amplifying said received microwave signals and for retransmitting said amplified microwave signals to a second receiver positioned at said second location; said second receiver including means for extracting information from said amplified microwave signals; first means for generating a pilot signal having a first predetermined frequency positioned at said second location and for transmitting said pilot signal to a second means positioned at said first location for receiving said pilot signal, multiplying its frequency and retransmitting said multiplied pilot signal to said second location; third means at said second location for receiving and multiplying the frequency of said received pilot signal to provide a first signal; fourth means for mixing said first signal with a second predetermined frequency to provide a second signal; and fifth means for mixing said second signal with said amplified microwave signals received by said second receiver to cancel first order doppler frequency shifts of said amplified microwave signals in passing from said first location to said second location.

Claim 12

A bistatic synthetic aperture radar comprising: a first receiver for receiving target reflected microwave signals; a transmitter for generating and transmitting microwave signals towards a target; said first receiver spaced apart from said transmitter at first and second locations respectively and including means for moving said first receiver at said first location with respect to said transmitter at said second location; said first receiver including means for amplifying said received microwave signals and for retransmitting said amplified microwave signals to a second receiver positioned at said second location; said second receiver including means for extracting information from said amplified microwave signals; first means for generating a pilot signal having a first predetermined frequency positioned at said second location and for transmitting said pilot signal to a second means positioned at said first location for receiving said pilot signal, multiplying its frequency and retransmitting said multiplied pilot signal to said second location; third means at said second location for receiving and multiplying the frequency of said received pilot signal to provide a first signal; fourth means for mixing said first signal with a second predetermined frequency to provide a second signal; and fifth means for mixing said second signal with said amplified microwave signals received by said second receiver to cancel first order doppler frequency shifts of said amplified microwave signals in passing from said first location to said second location.

Claim 13

A helicopter rotor tip synthetic aperture radar system which provides compensation for doppler frequency signal shifts arising from relative movement between rotor tip mounted receiver means which receives target reflected radar signals, and helicopter mounted radar signal generation and transmitter means which are remote from the rotor tip, wherein relay transmission means are included at the rotor tip for relaying target reflected signals from the rotor tip to a relay receiver disposed on the helicopter remote from the rotor with a doppler frequency shift imposed on this relayed target reflected signal, and wherein pilot signal generating and transmitter/receiver means are disposed on the helicopter remote from the rotor, which pilot signal is of a predetermined frequency and is transmitted to and received at the rotor tip, with frequency multiplying means provided at the rotor tip for multiplying the pilot signal, which multiplied pilot signal is retransmitted back to the pilot signal receiver means remote from the rotor and mixed with a doppler frequency shift compensation signal to thereby cancel the doppler frequency shift signal.

Claim 14

A helicopter rotor tip synthetic aperture radar system which provides compensation for doppler frequency signal shifts arising from relative movement between rotor tip mounted receiver means which receives target reflected radar signals, and helicopter mounted radar signal generation and transmitter means which are remote from the rotor tip, wherein relay transmission means are included at the rotor tip for relaying target reflected signals from the rotor tip to a relay receiver disposed on the helicopter remote from the rotor with a doppler frequency shift imposed on this relayed target reflected signal, and wherein pilot signal generating and transmitter/receiver means are disposed on the helicopter remote from the rotor, which pilot signal is of a predetermined frequency and is transmitted to and received at the rotor tip, with frequency multiplying means provided at the rotor tip for multiplying the pilot signal, which multiplied pilot signal is retransmitted back to the pilot signal receiver means remote from the rotor and mixed with a doppler frequency shift compensation signal to thereby cancel the doppler frequency shift signal.