Passive range and angle measurement system and method
First Claim
Patent Images
1. A method of determining range from a moving platform to an emitter comprising the steps of:
- (a) receiving a RF signal from the emitter;
(b) counting a number of phase reversals of the received RF signal during a period of time;
(c) measuring a Doppler frequency during the period of time; and
(d) determining the range to the emitter based on both the number of phase reversals counted in step (b) and the Doppler frequency measured in step (c).
3 Assignments
0 Petitions
Accused Products
Abstract
A method determines range from a moving platform to an emitter. The method receives a RF signal from the emitter; counts a number of phase reversals of the received RF signal during a period of time; measures a Doppler frequency during the period of time; and determines the range to the emitter based on both the number of counted phase reversals and the measured Doppler frequency.
-
Citations
20 Claims
-
1. A method of determining range from a moving platform to an emitter comprising the steps of:
-
(a) receiving a RF signal from the emitter;
(b) counting a number of phase reversals of the received RF signal during a period of time;
(c) measuring a Doppler frequency during the period of time; and
(d) determining the range to the emitter based on both the number of phase reversals counted in step (b) and the Doppler frequency measured in step (c). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
step (b) includes counting the number of phase reversals of the received RF signal during the period of time the moving platform traverses a distance. -
3. The method of claim 2 further including the step of:
-
(e) measuring the distance traversed by the moving platform during the period of time; and
step (d) includes determining the range to the emitter based on the number of phase reversals counted in step (b), the Doppler frequency measured in step (c) and the distance measured in step (e).
-
-
4. The method of claim 3 wherein
measuring the distance includes obtaining geographic position data at each end of the distance traversed by the moving platform, using one of an inertial navigation system (INS), a Global Positioning System (GPS), and a combination of an INS and GPS. -
5. The method of claim 3 wherein step (d) includes
forming a first triangle having (i) a first side being a function of the distance traversed by the moving platform, (ii) a second side being a function of the counted number of phase reversals of the received RF signal, and (iii) a third side being a function of a Law of Cosines, in which an angle α - between the first side and the second side is a function of the measured Doppler frequency, and
determining the range to the emitter using the formed first triangle.
- between the first side and the second side is a function of the measured Doppler frequency, and
-
6. The method of claim 5 wherein step (d) includes
forming an equilateral triangle in which (i) a base of the equilateral triangle is the third side of the first triangle, and (ii) two equal sides of the equilateral triangle, each side denoted by R, are a function of the angle α - , and
determining the range to the emitter includes combining a side R of the equilateral triangle and the second side of the first triangle.
- , and
-
7. The method of claim 3 wherein
measuring the distance includes measuring the distance during a predetermined period of time having a value ranging between 1 second and 20 seconds. -
8. The method of claim 3 wherein
step (c) of measuring the Doppler frequency includes measuring variations in the Doppler frequency during the period of time, the variations denoted by Δ - fd,
in which 1/Δ
fd is approximately a width between 3 dB power points of a main lobe of an autocorrelation function of the Doppler frequency.
- fd,
-
9. The method of claim 2 wherein
receiving the RF signal includes receiving one of a pulsed Doppler signal and a CW signal. -
10. The method of claim 2 further including the steps of:
-
(e) mixing the received RF signal with an oscillator signal to produce an intermediate frequency (IF) signal;
(f) converting the IF signal into a digital signal;
(g) storing the digital signal in a memory; and
(h) providing the digital signal for counting the number of phase reversals in step (b).
-
-
11. The method of claim 10 wherein
step (e) includes mixing the received RF signal with a numerically controlled oscillator (NCO) signal to produce a phase coherent IF signal.
-
-
12. A method of determining range from a moving platform to an emitter comprising the steps of:
-
(a) receiving a RF signal from the emitter during a period of time the moving platform traverses a distance, the distance denoted by b;
(b) determining a carrier wavelength, λ
, of the RF signal;
(c) counting a number of phase reversals of the received RF signal during the period of time, the number denoted by N;
(d) determining a range differential, Δ
R, between the moving platform and the emitter during the period of time, in which - View Dependent Claims (13, 14, 15)
-
-
16. An apparatus, installed onboard a moving platform, for determining range from the moving platform to an emitter comprising
a receiver for receiving a RF signal from the emitter, an analog to digital converter (ADC) for converting the received RF signal into a digital signal, a memory for storing the digital signal provided by the ADC, and a processor coupled to the memory for extracting the stored digital signal, and (a) counting a number of phase reversals of the digital signal during a period of time, (b) measuring a Doppler frequency during the period of time, and (c) determining the range to the emitter using both the counted number of phase reversals and the measured Doppler frequency.
Specification