Method for the calibration of an FM/CW type radio altimeter, and radio altimeter designed for the implementation of this method
AssigneeThomson-CSF
InventorFabrice Orlandi
Life of this patent
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Abstract
A radio altimeter using a linear oscillator to transmit a saw-toothed signal comprises, in addition to this first oscillator, a second linear oscillator to transmit, in synchronism with the first linear oscillator, another saw-toothed signal with a given saw-tooth duration Td. The plateau of the sawteeth of the two saw-toothed signals are at a distance from each other equal to a value f. The test consists in obtaining a height h′ by beats between the two saw-toothed signals and computing a standard height he=f.c.Td/dF.2 where c is the speed of light and dF the duration of each saw-tooth of the other signal. Application to all FM/CW radio altimeters.
Claims12
A method of calibration designed for an FM/CW type radio altimeter, comprising:
- injecting an auxiliary saw-toothed signal with a given saw-tooth slope, Td/dF, into a link between a receiving antenna and a mixer, sawteeth of the auxiliary saw-toothed signal being synchronous with sawteeth of a signal produced by a linear oscillator, with a plateau of the sawteeth of the auxiliary saw-toothed signal being offset with respect to a plateau of the sawteeth of the linear oscillator signal by a frequency f,
- obtaining, by modifying at least one of a duration of modulation of the sawteeth of the linear oscillator signal and a bandwidth dF of the linear oscillator signal, a beat at the frequency f between the sawteeth of the linear oscillator signal and the sawteeth of the auxiliary saw-toothed signal so that a processing device gives a measured height h′;
- and
- comparing the measured height h′ with a standard height h obtained by computation according to a formula h=f*c*Td/(dF*2), in which is the speed of light.
An FM/CW type radio altimeter comprising:
- a control device;
- a linear oscillator;
- first coupling elements to couple the linear oscillator to a transmitting antenna;
- a mixer circuit with a first input coupled to the linear oscillator, and a second input;
- an auxiliary linear oscillator, the auxiliary oscillator being controlled by the control device;
- a directional coupler to couple a receiving antenna and an output of the auxiliary linear oscillator to the second input of the mixer circuit;
- and
- a processing device to process output signals from the mixer circuit.
Dependencies are inferred from the claim text.