US5045859A — Phase reference navigation system and method

Claim 1

Independent Claim 228 words

A navigation system comprising antenna means having n elements for radiating a plurality of fixed beams of RF energy in respective different predetermined angular directions; means for supplying RF energy to said antenna means to cause RF radiation therefrom; means for impressing upon each radiated beam a variable signal having a phase corresponding to the predetermined angular direction of the beam; and means for combining at a receiver the variable signals of first and second ones of the beams to form a resultant signal having a phase which varies as a function of angle between phases corresponding to the predetermined angular directions of the first and second beams and wherein said impressing means comprises means for generating first and second subcarriers of different frequencies; first means for modulating the first and second RF beams with the first and second subcarriers, respectively; and second means for modulating each subcarrier with the variable signal and wherein the first modulating means comprises means for modulating the RF energy radiated by each beam with a reference signal which has a phase that is constant with angular direction, and means for delaying the subcarriers which are supplied to at least n-1 of said elements so that the variable signal on each subcarrier has a phase relative to the reference signal that corresponds to the angular direction of the beam radiated by that element.

Claim 2

Dependent Claim 228 words

A navigation system comprising antenna means having n elements for radiating a plurality of fixed beams of RF energy in respective different predetermined angular directions; means for supplying RF energy to said antenna means to cause RF radiation therefrom; means for impressing upon each radiated beam a variable signal having a phase corresponding to the predetermined angular direction of the beam; and means for combining at a receiver the variable signals of first and second ones of the beams to form a resultant signal having a phase which varies as a function of angle between phases corresponding to the predetermined angular directions of the first and second beams and wherein said impressing means comprises means for generating first and second subcarriers of different frequencies; first means for modulating the first and second RF beams with the first and second subcarriers, respectively; and second means for modulating each subcarrier with the variable signal and wherein the first modulating means comprises means for modulating the RF energy radiated by each beam with a reference signal which has a phase that is constant with angular direction, and means for delaying the subcarriers which are supplied to at least n-1 of said elements so that the variable signal on each subcarrier has a phase relative to the reference signal that corresponds to the angular direction of the beam radiated by that element.

Claim 3

Dependent Claim 40 words

The system of claim 1, wherein said first means for modulating amplitude modulates the first and second RF beams with the first and second subcarriers, respectively, and said second means for modulating frequency modulates each subcarrier with the variable signal.

Claim 4

Dependent Claim 66 words

The system of claim 2, wherein the generating means comprises first and second variable frequency oscillators for generating the first and second subcarriers; and the second modulating means comprises means for shifting the frequency of the variable oscillators at the frequency of the variable signal; and further comprising means for supplying the shifted frequencies from the variable frequency oscillators to said elements for the RF beams.

Claim 5

Dependent Claim 23 words

The system of claim 3, wherein the delaying means comprises a delay line for delaying the frequency modulated subcarrier supplied to each element.

Claim 6

Dependent Claim 42 words

The system of claim 1, wherein said combining means comprises means for forming the vector sum of the variable signals so that the resultant signal has a phase which varies as a function of the amplitudes of the first and second subcarriers.

Claim 7

Dependent Claim 72 words

The system of claim 1, wherein the antenna means comprises an antenna array having a plurality of antenna elements, one for each beam of RF energy, each antenna element having a narrow beamwidth radiation pattern, the elements being arranged such that the radiation patterns of adjacent elements cross over one another at a predetermined power level, and such that the radiation patterns of the plurality of elements cover a predetermined angular sector.

Claim 8

Dependent Claim 226 words

A navigation system comprising a plurality of antenna elements, there being n antenna elements, each element having a radiation pattern with a predetermined beamwidth and the elements being arranged to have different beamwidth directions of orientation with the patterns of adjacent elements overlapping; means for supplying RF energy to the antenna elements so that each element radiates a fixed beam of RF energy in its predetermined direction of orientation; first means for modulating the RF energy supplied to a first group of antenna elements with a first subcarrier of a first frequency, and for modulating the RF energy supplied to a second group of antenna elements with a second subcarrier of a second frequency, the first and second groups of antenna elements alternating with one another such that the RF energy radiated by adjacent antenna elements is modulated by said first and second subcarriers of different frequencies; and second means for modulating the first and second subcarriers with a variable signal, and further comprising means to impress a reference signal upon the RF energy supplied to each antenna element, which reference signal has the same phase at each antenna element, and wherein the phase of the variable signal at each antenna element relative to the reference signal is adjusted to have a value corresponding to the angular orientation of the element relative to a reference direction.

Claim 9

Dependent Claim 226 words

A navigation system comprising a plurality of antenna elements, there being n antenna elements, each element having a radiation pattern with a predetermined beamwidth and the elements being arranged to have different beamwidth directions of orientation with the patterns of adjacent elements overlapping; means for supplying RF energy to the antenna elements so that each element radiates a fixed beam of RF energy in its predetermined direction of orientation; first means for modulating the RF energy supplied to a first group of antenna elements with a first subcarrier of a first frequency, and for modulating the RF energy supplied to a second group of antenna elements with a second subcarrier of a second frequency, the first and second groups of antenna elements alternating with one another such that the RF energy radiated by adjacent antenna elements is modulated by said first and second subcarriers of different frequencies; and second means for modulating the first and second subcarriers with a variable signal, and further comprising means to impress a reference signal upon the RF energy supplied to each antenna element, which reference signal has the same phase at each antenna element, and wherein the phase of the variable signal at each antenna element relative to the reference signal is adjusted to have a value corresponding to the angular orientation of the element relative to a reference direction.

Claim 10

Dependent Claim 31 words

The system of claim 7, wherein said reference direction is North, and the phase of the variable signal at each antenna element corresponds to the azimuth bearing of the antenna element.

Claim 11

Dependent Claim 82 words

The system of claim 7, wherein the supplying means comprises means for dividing RF energy from a common source equally among the antenna elements so that each antenna element radiates the same amount of RF energy, and wherein the antenna elements are arranged such that the radiation patterns of adjacent elements cross over one another at substantially a half-power point and such that the peak of each radiation pattern is located at substantially a null of the radiation patterns of adjacent elements.

Claim 12

Dependent Claim 113 words

The system of claim 7, further comprising means for receiving the RF energy radiated by first and second adjacent antenna elements and for demodulating the first and second subcarriers to recover the variable signals; means for combining the variable signals to produce a resultant signal having a phase which varies continuously as a function of angle from the predetermined direction of orientation of the first one of said adjacent antenna elements to the predetermined direction of orientation of the second one of said adjacent antenna elements; and means for comparing the phase of the resultant signal with the phase of a reference signal to determine the direction of orientation of the receiving means.

Claim 13

Dependent Claim 47 words

The system of claim 10, wherein the first and second subcarriers are frequency modulated by the variable signals, and the demodulating means comprises filter means for separating the first and second subcarriers, and first and second frequency demodulators for demodulating the subcarriers to recover the variable signals.

Claim 14

Dependent Claim 59 words

The system of claim 11, wherein the combining means comprises means for forming a vector sum of the variable signals to produce the resultant signal, and wherein said comparing means comprises a phase comparator for comparing the phases of the resultant signal and the reference signal to determine the bearing of the receiving means relative to the antenna elements.

Claim 15

Dependent Claim 51 words

The system of claim 7, wherein the system is arranged to cover a predetermined angular sector, and wherein the system comprises third means for modulating the RF energy emitted by antenna elements at sides of said sector with a predetermined clearance frequency to provide a flag alarm signal at a receiver.

Claim 16

Dependent Claim 185 words

A navigation method comprising radiating a plurality of fixed beams of RF energy in different predetermined angular directions; impressing upon each beam, as it is radiated, a variable signal having a phase corresponding to the predetermined angular direction of such beam; and combining at a receiver the variable signals of first and second ones of the beams to form a resultant signal having a phase which varies as a function of angle between the predetermined angular directions of the first and second beams and further comprising generating first and second subcarriers of different frequencies; modulating the first and second subcarriers with first and second variable signals respectively; and modulating the first and second RF beams respectively with the first and second subcarriers, having the first and second variable signals thereon and further comprising modulating each of the RF beams with a reference signal having a phase which is constant with angular direction, and adjusting the phases of the variable signals such that the phase of each variable signal relative to the reference signal has a value corresponding to the angular direction of its associated beam.

Claim 17

Dependent Claim 185 words

A navigation method comprising radiating a plurality of fixed beams of RF energy in different predetermined angular directions; impressing upon each beam, as it is radiated, a variable signal having a phase corresponding to the predetermined angular direction of such beam; and combining at a receiver the variable signals of first and second ones of the beams to form a resultant signal having a phase which varies as a function of angle between the predetermined angular directions of the first and second beams and further comprising generating first and second subcarriers of different frequencies; modulating the first and second subcarriers with first and second variable signals respectively; and modulating the first and second RF beams respectively with the first and second subcarriers, having the first and second variable signals thereon and further comprising modulating each of the RF beams with a reference signal having a phase which is constant with angular direction, and adjusting the phases of the variable signals such that the phase of each variable signal relative to the reference signal has a value corresponding to the angular direction of its associated beam.

Claim 18

Dependent Claim 26 words

The method of claim 14, wherein the first and second variable signals are identical in frequency and are frequency modulated onto the first and second subcarriers.

Claim 19

Dependent Claim 72 words

The method of claim 15, wherein the first and second subcarriers are generated by respective first and second variable frequency oscillators, and wherein the variable phase signals are impressed upon the RF beams by shifting the frequencies of the first and second oscillators using a common modulating signal and time delaying the outputs of the variable frequency oscillators by different amounts corresponding to the angular directions of the first and second beams.

Claim 20

Dependent Claim 38 words

The method of claim 16, wherein the plurality of fixed beams is arranged to cover 360°, and wherein the variable signals are adjust such that a phase difference of 2π relative to the reference signal corresponds to 360°.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1994-09-02	1995-03-04	1995-09-03	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1998-09-02	1999-03-04	1999-09-03	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2002-09-02	2003-03-04	2003-09-03	$7700.00	Window Closed / Lapsed

Phase reference navigation system and method

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