Transmitter location system for frequencies below HF

• US 5,073,784 A
• Filed: 04/26/1972
• Issued: 12/17/1991
• Est. Priority Date: 04/26/1972
• Status: Expired due to Term

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Westfall, Wallace D.
• Primary Examiner(s): Wallace, Linda J.
• Application Number:
  US05/249,443
• Time in Patent Office: 7,174 Days
• Field of Search: 343/112 R, 343/113 R, 342/147, 342/444, 342/450, 342/465
• US Class Current: 342/465
• CPC Class Codes: G01S 11/04 using angle measurements

Abstract

Differential phase measurement techniques and apparatus for accurately loing unknown transmitters over great distances at radio frequencies below HF. A network of separated, time- and phase-synchronized, pairs of receiving stations having vertical whip antennas and having a known base-line geometry with respect to each other are used to accurately measure VLF phase differentials. The measured phase differences are compared against theoretical calculated values to provide highly accurate transmitter location information.

Claims

1. Apparatus for locating unknown transmitters over great distances at a frequency f below HF comprising:

a plurality of separated time synchronized receiver sites,

each of said sites comprising a local station and a remote station separated a known baseline distance Δ

R with respect to each other;

receiver means at said remote station and said local station for producing a remote IF output and a local IF output, respectively, in response to received signals from an unknown transmitter having a bearing θ and

a range D measured from the center of said baseline distance;

data link means for coupling said remote output to said local station;

phase comparator means at said local station for measuring the phase difference between said remote output and said local output, wherein said phase difference is related to said bearing; and

,

calibration means at each of said stations for phase synchronizing said stations with respect to each other whereby signals received from a transmitter located at a point equidistant from said stations produces a zero phase difference measurement at the output of said phase comparator.

2. A method for locating unknown transmitters over great distances at a frequency f below HF comprising the steps of:

receiving signals transmitted by an unknown transmitter at different separated and time-synchronized pairs of local and remote receiver stations;

phase synchronizing each of said pairs to produce zero phase differential when signals are received from a transmitter located equidistant from said local and remote stations; and

,

measuring the phase difference between signals received at said stations whereby said phase difference is directly proportional to the cosine of the bearing from the midpoint of a line between said stations to said unknown transmitter.