Direction-finding method for determining the incident direction of a high-frequency electromagnetic signal

• US 6,313,795 B1
• Filed: 10/13/1998
• Issued: 11/06/2001
• Est. Priority Date: 10/10/1997
• Status: Expired due to Term

• Current Assignee: Daimler-Benz Aerospace AG (Mercedes-Benz Group AG)
• Original Assignee: Daimler-Benz Aerospace AG (Mercedes-Benz Group AG)
• Inventors: Schuster, Manfred, Herrmann, Franz
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/170,201
• Time in Patent Office: 1,120 Days
• Field of Search: 342/442, 342/433, 342/56, 342/156
• US Class Current: 342/442
• CPC Class Codes: G01S 3/48 the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured

Abstract

A direction-finding method for determining an incident angle of a high-frequency electromagnetic signal in a system including at least two receiving antennas spaced apart by a known distance. the antenna output signals of the at least two receiving antennas are converted, together (in accordance with a multiplexing procedure) or individually, into the frequency domain through a Fourier transformation, followed by a conversion into an IF range and an A/D conversion. In this range, the phase difference between the output signals is determined and the signal frequency of the incident wave is determined through a phase-sequence analysis. The incident angle of the incident wave is determined from the phase difference and the signal frequency.

Claims

1. A direction-finding method for determining an incident direction of a high-frequency electromagnetic signal with respect to a predeterminable primary direction of an antenna arrangement including at least two receiving antennas spaced apart by a known distance (D) for receiving the incident signal, the method including steps of:

(a) converting output signal of each antenna into an intermediate-frequency signal having a predeterminable intermediate frequency;

(b) converting the intermediate-frequency signals into a corresponding digital signals;

(c) converting the digital signals into the frequency domain through a Fourier transformation;

(d) measuring a phase-difference in the frequency domain between the frequency domain signals associated with the antennas yielding a phase difference (Δ

φ

);

(e) performing a phase-sequence analysis in the frequency domain for determining phase differences for temporally-successive Fourier intervals continuously within a predeterminable measuring period;

(f) determining from the phase differences of step (e) an estimated value for signal frequency (f) within the discrete Fourier spectrum; and

(g) determining an incident angle (e) from the phase difference (Δ

φ

) and the signal frequency (f) according to the formula;

2. The direction-finding method as defined in claim 1, further including:

supplying the output signals of the antennas to an analysis channel comprising at least an antenna change-over switch for switching the output signals of the antennas, with the antenna change-over switch being switched between the antennas following each Fourier interval, using as a measure the temporal length of the Fourier intervals; and

wherein;

step (a) includes switching the antenna signals into the predeterminable intermediate-frequency range with a mixer disposed downstream of the antenna change-over switch;

Step (b) includes converting the intermediate-frequency signals into the corresponding digital signals with the use of an analog/digital converter disposed downstream of the mixer; and

step (c) includes with the use of a Fourier transformer disposed downstream of the analog/digital converter.

3. The direction-finding method as defined in claim 1, including coupling each antenna to an associated analysis channel, respectively comprising at least a mixer for converting the antenna output signal into the predeterminable intermediate-frequency range according to step (a), an analog/digital converter disposed downstream of the mixer for converting the intermediate-frequency signals into the corresponding digital signals according to step (b), and a Fourier transformer disposed downstream of the analog/digital converter for converting the digital signals into the frequency domain according to step (c);

and wherein

the measuring of step (d) comprises measuring the phase difference (Δ

φ

) between the output signals of the Fourier transformers associated with each antenna.

4. The direction-finding method as defined in claim 3, wherein step (e) includes performing the phase-sequence analysis in only one analysis channel after the Fourier transformation for determining the signal frequency (f) that is used to determine the incident angle.

5. The direction-finding method as defined in claim 3, wherein step (e) includes performing the phase-sequence analysis for determining a signal frequency in each analysis channel after the Fourier transformation;

and further including averaging the signal frequencies determined in each analysis channel in a predeterminable fashion, resulting in an average signal frequency (f) which is used to determine the incident angle.

6. The direction-finding method as defined in claim 1, wherein step (c) includes using a Fast-Fourier transformation at least when incident signals are in a high-frequency or extremely-high-frequency range.

7. The direction-finding method as defined in claim 1, utilized for simultaneous direction finding in which incident directions of at least two different incident waves are determined essentially simultaneously.