US 4,489,327 A · Direction finding

Abstract

A direction finding system has two antennas with response patterns at 90.degree.. A sense antenna 14 is mounted to produce a sense output dependent on the received radio signal but independent of its bearing. A commutating and combining arrangement receives the antenna outputs and produces a sequence of control signals each of which represents a respective one of the following: the North-South output, the East-West output, the sum of the NS and EW outputs, the difference between the NS and EW outputs, the sum of the NS and sense outputs, and the sum of the EW and sense outputs. A receiver produces an output having a magnitude dependent on any amplitude modulation on the received radio signal but independent of its bearing. A data processing unit (a) compares particular pairs of the control signals which are not dependent on the sense antenna output to produce a bearing output dependent on the bearing of the received radio signal but independent of its sense, (b) compares the values of specific pairs of the control signals, one of each such pair being a control signal not dependent on the sense antenna output and the other being a control signal dependent on the sense antenna output, to determine the sense of the bearing, and represented by the said bearing outputs, and (c) uses the output of the receiver to render the values of the control signals independent of any amplitude modulation.

Claims11

Dependent claims

A direction finding system for assessing the bearing of a received radio signal, comprising

first and second fixed antenna arrangements having response patterns arranged substantially at 90.degree. to each other and defining a first set of perpendicular axes for receiving the said radio signal,
a single radio receiver,
signal processing means operative to produce a first output representing the radio signal as received by the first antenna arrangement during a first time period, operative to produce a second output representing the radio signal as received by the second antenna arrangement during a second time period, operative to produce a third output representing the sum of selected proportions of the first and second outputs during a third time period, and operative to produce a fourth output representing the difference of selected proportions of the first and second outputs during a fourth time period, and
output means operative to produce the ratio of the first and second outputs to derive a first set of four bearing angle values relative to said first set of axes, and operative to produce the ratio of the third and fourth outputs to derive a second set of four bearing angle values relative to a second set of perpendicular axes shifted by a selected angle relative to said first set of axes, whereby two of the bearing angle values of the first set coincide in space with two of the bearing angle values of the second set, such that the bearing of said received radio signal is one of said coincident bearing angle values.

1 more element

A direction finding system for assessing the bearing of a received radio signal, comprising:

first and second antenna arrangements having their response patterns mutually shifted by substantially 90.degree. whereby to produce first and second outputs each having a magnitude dependent on any amplitude modulation on the received radio signal and on its bearing with respect to the response pattern of a respective one of the antenna arrangements;
a sense antenna arrangement operative to produce a third output dependent on the received radio signal but independent of its bearing,
a commutating and combining arrangement connected to receive the first, second and third outputs and operative to produce a sequence of control signals each of which represents a respective one of the following:
the first output, the second output, the sum of the first and second outputs, the difference between the first and second outputs, the difference between the first and second outputs, the sum of the first and third outputs, and the sum of the second and third outputs;
means responsive to the first and second outputs to produce a fourth output having a magnitude dependent on any amplitude modulation on the received radio signal but independent of its bearing;
and
signal processing means responsive to the fourth output and the said control signals and comprising first means operative to compare particular pairs of the control signals which are not dependent on the said third output whereby to produce a bearing output dependent on the bearing of the received radio signal but independent of its sense, second means operative to compare the values of specific pairs of the control signals, one of each such pair being a control signal not dependent on the said third output and the other thereof being a control signal dependent on the said third output, whereby to determine the sense of the bearing represented by the said bearing output, and third means responsive to the said fourth output to render the values of the said control signals independent of any amplitude modulation.

4 more elements

Dependencies are inferred from the claim text.

Direction finding

Life of this patent

Direction finding

Life of this patent

Abstract

Claims11