FM radar system

Claim 2

An FM radar system for measuring a range, a direction, and a relative speed to a target comprising: at least one pair of antennas, each antenna of each pair having substantially the same directivity, each antenna being set to radiate beams in a slightly different direction from the beams radiated by the other antenna, and each antenna being set to receive return beams, said return beams comprising beams originally radiated by the antenna and then reflected by a target; a first signal distributing means for distributing an FM signal having a frequency varying with time to each of said antennas successively and repeatedly; means for successively and repeatedly generating beat signals, said beat signal generating means having a first and second set of input terminals, said first set of input terminals being adapted to receive a signal indicative of said return beam; a second signal distributing means for distributing a reference FM signal to said second set of input terminals of said beat signal generating means, the reference FM signal having a different frequency from that of said FM signal, and the difference being caused by shifting both frequencies by different amounts or delaying both signals by different amounts; means for detecting at least one of the frequencies of said generated beat signal and separating it into two parts, one part being caused by Doppler shift and the other part being caused by a propagation delay time of said return beams, and converting the first part to a relative speed to said target and the second part to a range to said target respectively; and a means for detecting a ratio of levels of beat signals and converting the ratio to a direction to said target.

Claim 3

An FM radar system for measuring a range, a direction, and a relative speed to a target comprising: at least one pair of antennas, each antenna of each pair having substantially the same directivity, each antenna being set to radiate beams in a slightly different direction from the beams radiated by the other antenna, and each antenna being set to receive return beams, said return beams comprising beams originally radiated from the antenna and then reflected by a target; a first signal distributing means for distributing an FM signal to each of said antennas successively and repeatedly, the FM signal having a frequency varying with time during a first half period and being fixed to a constant value during a following half period; means for successively and repeatedly generating beat signals, said beat signal generating means having a first and second set of input terminals, said first set of input terminals being adapted to receive a signal indicative of said return beam; a second signal distributing means for distributing a reference FM signal to said second set of input terminals of said beat signal generating means, the reference FM signal having a different frequency from that of said FM signal, and the difference being caused by shifting both frequencies by different amounts or delaying both signals by different amounts; means for detecting at least one of the frequencies of said generated beat signals during said first period and converting it to a range to said target; means for detecting at least one of said generated beat signals during said second period and converting it to a relative speed to said target; and means for detecting a ratio of levels of the beat signals and converting the ratio to a direction to said target.

Claim 4

An FM radar system according to claims 1 - 3 wherein said first signal distributing means includes a first up-converter to shift up the frequency of a low frequency FM signal to a first value; and said second signal distributing means includes a second up-converter to shift up the frequency of a second low frequency FM signal to a second value being different from said first value.

Claim 5

An FM radar system according to claims 1 - 3 wherein one of said first and second signal distributing means includes a means for delaying a signal to be distributed by a different amount.

Claim 6

An FM radar system according to claims 1 - 5 wherein each of said first and second signal distributing means includes a pair of frequency multipliers and a switching means for distributing FM signals to said frequency multipliers successively.

Claim 7

An FM radar system according to claims 1 - 6 wherein the FM radar system includes two pairs of antennas, one being set for detecting a direction of a target in a horizontal plane and the other being set for detecting a direction of a target in a perpendicular plane.