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Determining Transmitted Frequency With Moving Receiver

IP.com Disclosure Number: IPCOM000034717D
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Cheng, SM: AUTHOR [+2]

Abstract

The frequency of a stationary transmitter can be computed at a single moving receiver platform from the linear velocity of the rotated receiving antenna and the difference between the detected maximum and minimum frequencies. This capability enables determination of platform motion from the Doppler shift in signal for passive navigation or for locating the transmitter. In Fig. 1, signals from stationary transmitter 1 are detected by rotating antenna 2 on moving platform 3, such as an aircraft. Platform 3 moves at radial velocity VR relative to the transmitter 1 and antenna 2 has a linear velocity VL . When antenna 2 rotates, the detected frequency varies sinusoidally. When moving directly toward transmitter 1, the detected received frequency will be maximum (Image Omitted) where c is the speed of light.

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Determining Transmitted Frequency With Moving Receiver

The frequency of a stationary transmitter can be computed at a single moving receiver platform from the linear velocity of the rotated receiving antenna and the difference between the detected maximum and minimum frequencies. This capability enables determination of platform motion from the Doppler shift in signal for passive navigation or for locating the transmitter. In Fig. 1, signals from stationary transmitter 1 are detected by rotating antenna 2 on moving platform 3, such as an aircraft. Platform 3 moves at radial velocity VR relative to the transmitter 1 and antenna 2 has a linear velocity VL . When antenna 2 rotates, the detected frequency varies sinusoidally. When moving directly toward transmitter 1, the detected received frequency will be maximum

(Image Omitted)

where c is the speed of light. When antenna 2 rotates directly away from the transmitter, the detected frequency will be minimum Subtracting equation (2) from (1) yields For an airborne platform, the antenna is electrically rotated and a receiver arrangement is schematically illustrated in Fig. 2. Three fixed, non-colinear antennas 4 are carried on platform 5, and each feeds a respective coherent receiver 6 and an analog-to-digital converter 7. Converters 7 supply their outputs to digital signal processing computer 8. The signal processor modifies phase and amplitude of the receiver outputs before summing them, creating an electrically rota...