US3689926A - Radio direction-finding method and a device for implementing said method - Google Patents

Radio direction-finding method and a device for implementing said method Download PDF

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US3689926A
US3689926A US838943A US3689926DA US3689926A US 3689926 A US3689926 A US 3689926A US 838943 A US838943 A US 838943A US 3689926D A US3689926D A US 3689926DA US 3689926 A US3689926 A US 3689926A
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signal
phase
signals
finding
value
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Etienne Honore
Emile Torcheaux
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Societe dEtude et dApplication des Techniques Nouvelles NeoTec
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S1/00—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith
    • G01S1/02—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith using radio waves
    • G01S1/08—Systems for determining direction or position line
    • G01S1/20—Systems for determining direction or position line using a comparison of transit time of synchronised signals transmitted from non-directional antennas or antenna systems spaced apart, i.e. path-difference systems
    • G01S1/30—Systems for determining direction or position line using a comparison of transit time of synchronised signals transmitted from non-directional antennas or antenna systems spaced apart, i.e. path-difference systems the synchronised signals being continuous waves or intermittent trains of continuous waves, the intermittency not being for the purpose of determining direction or position line and the transit times being compared by measuring the phase difference
    • G01S1/304—Analogous systems in which a beat frequency, obtained by heterodyning the signals, is compared in phase with a reference signal obtained by heterodyning the signals in a fixed reference point and transmitted therefrom, e.g. LORAC (long range accuracy) or TORAN systems

Definitions

  • PATENTEDSEP 5 I972 SHEET OSUF 12 .mtmanw 5:912 3.689.926 SHEEI 014 OF 12 an Fl Fl Fl Fl R PATENTEDSE'P 51912 SHEET USUF 12 H mm h h m @E dvq a b PATENTEDSEP 51972 sum 08 0F 12 C INPUT CLOCK PATENTEDSEP smz sum user 1 PATENTEUSEP 51912 3.689.926 sum mar 12 Fig.17
  • PATENTEUSEP 5 m2 SHEET 11 [1F 12 PATENTEUSEP 5:912
  • the present invention relates to a method of radio position-finding and to a device for implementing said method.
  • radio position-finding is a technique of obtaining a navigational fix by means of which a vehicle, in particular a ship, can determine its position by means of radio signals received by the equipment which it carries.
  • This method of obtaining a fix thus requires the installation of a transmitter system (fixed transmitters) for said signals, as well as the installation of a receiver system (receiver apparatus) on board the vehicle, the combination of the system of the transmitted signals and the positions of the respective transmitters being such that the receiver apparatus can deduce the position of the vehicle from the signals which it receives.
  • the phases of the received signals are employed in order to deduce the positional information (French Pat. No. 790,386).
  • total phase of a sinusoidal signal varying with time tin accordance with the law A sin (211' ft where f is the frequency of the signal and s the phase at an instant of origin (t :0), will be used to designate the value I; (2mg
  • the total phase can be split into any whole number of revolutions of Zn (whole phase) and into a fraction of 211 (partial phase):
  • the partial phase is equal to the instantaneous phase (21rft t ).
  • the total phase-shift will designate the difference between the total phases of the two signals considered from the same time origin.
  • the total phase-shift can be split into a whole part (multiple of 21:) and a fractional part (partial phase-shift).
  • the system of electrical signals forming a transmission chain is made up of two groups of three signals each.
  • Each group comprises two high-frequency radio signals each produced by a different transmitter and having closely adjacent frequencies differing from one another by a value which corresponds to an audio frequency, and an HP radio frequency of different value, this being referred to as the reference frequency and being modulated by said audio frequency.
  • the two first high-frequency radio signals are mixed in order to produce an audio frequency positionfinding signal, and the reference radio signal is demodulated in order to obtain an audio frequency I reference signal, the total phase-shift between the two audio signals being proportional to the difference between the distances from the vehicle to the two transmitters producing the two first high-frequency signals with the consequence that the location of the locus of the total phase-shift points associated with a group of signals is constituted by a hyperbola of which the two transmitters form the foci, the locus associated with the other group being a similar hyperbola; the point of intersection between these two hyperbolae thus defines the position of the vehicle.
  • the radio reference signal is produced by one of the two transmitters which furnish the first I-IF radio signals.
  • the HF frequency of the position-finding signal produced by the other transmitter is thus termed the characteristic frequency.
  • the total phase-shift between the audio frequency position-finding and reference signals is likewise proportional to the characteristic frequency in each of the groups of signals. Since this characteristic frequency is fairly high, the total phase-shift expressed in radians exceeds 2n and therefore comprises a whole part and a fractional part.
  • phase meters only indicate the partial phase-shift of course, that is to say the fractional part of the total phase-shift, so that there is a certain indeterminacy in the position of the vehicle; in other words, knowledge of the partial phase-shift does not simply define one hyperbola but rather a family of hyperbolae, the vehicle being located upon just one of them. Similarly, the other group of signals likewise produces another family of hyperbolae.
  • a channel corresponds to the distance between two successive hyperbolae of one and the same family between which the phase undergoes a shift of 211' and the width of such a channel is inversely proportional to the characteristic frequency of the family.
  • This ambiguity can be overcome in a simple manner by providing, upon a chart depicting the position-finding zone, at least one point where the whole part of the total phase-shift is known through a direct determination. All that is necessary then is for the vehicle to pass through this point and for the navigator to record at that instant, on a counter, the known value of the whole part of the total phase-shift.
  • This counter will then count from said instant, either counting up or counting off (adding or subtracting), the number of times that the partial phase-shift reaches the value 2n.
  • the counter will therefore always record the real value of the whole part of the total phase-shift.
  • This is referred to as coupled operation.
  • This system means that the vehicle or vessel etc., must pass through a determinate point before it is possible to obtain a fix. Moreover, any accidental interruption in radio reception (transmitter or receiver breakdown) or fault in the operation of the counter, will falsify the recorded value so that it will be necessary to return to the known point.
  • a second family of hyperbolae is used, these hyperbolae having the same foci as the first and having a different characteristic frequency, that is to say channels of different width.
  • said width will be slightly different from that of the first family of hyperbolae so that the pieces of information supplied by these two families of curves can be used in the same manner as a vernier.
  • a third family of curves can be defined the channels of which have a width proportional to the difference between the characteristic frequencies.
  • the present invention overcomes these drawbacks by providing a radio position-finding method in which the design of the device used to implement it, combined with the exploitation of purely electronic means, makes it possible to utilize any frequency and to achieve fully automatic exploitation of the system of pieces of information supplied by the radio positionfinding signals, thus enabling direct recording and display to be effected without any ambiguity in terms of the location of the vehicle.
  • FIG. 1 illustrates a transmitter system of the single signal kind
  • FIG. 2 illustrates a transmitter system of the twosignal kind, with a reference facility
  • FIG. 3 illustrates the block diagram of a receiver in accordance with the invention for receiving a single signal transmission
  • FIG. 4 illustrates a detail of part of the receiver of FIG. 3, and FIG. 4a illustrates the wave forms of the signals occurring in this part of the receiver;
  • FIG. 5 illustrates the detail of another part of the receiver of FIG. 3
  • FIG. 6 illustrates the detail of a third part of the receiver of FIG. 3 and FIG. 6a and 6b illustrate the wave forms of the signals appearing in this part of the receiver, respectively in the case of a theoretical embodiment and in that of a practical embodiment;
  • FIG. 7a to 7d illustrate the block diagram of a receiver in accordance with the invention, for receiving a two-signal transmission
  • FIGS. 3a to 8d and 9a to 9d show respective embodiments of a phase detector for producing k' k differences, with operation diagrams thereof;
  • FIG. 10 illustrates a variant of the embodiments of FIGS. 8a and 9a
  • FIG. 11 illustrates a preferential embodiment of a unit
  • FIGS. 12a and 12b are respectively a detailed view of FIG. 11 and a corresponding operation diagram
  • FIG. 13 illustrates a simplified embodiment of a unit
  • FIGS. 14 and 15 illustrate variant embodiments of the device of FIG. 3;
  • FIG. 16 illustrates the block diagram of a receiver of the two signal type
  • FIG. 17 illustrates an embodiment of receiver according to FIG. 3, comprising means for providing the velocity information
  • FIG. 18 illustrates a read-out device for the x quantity
  • FIG. 19 illustrates an embodiment of a timing device for use in a receiver according to the invention.
  • the invention will be explained in terms of two types of transmission: transmission using the single signal principle and transmission using the two-signal principle.
  • the chief difference between these types of transmission resides in the fact that the audio frequency positionfinding signals obtained in the singlesignal system, are stable in frequency and phase which makes it possible to process them successively; however, in the case of the two-signal system, it is necessary to process the signals in pairs since they are unstable.
  • the transmitter arrangement corresponding to a group of signals comprises three transmitters A, B and C.
  • Transmitter A produces a high-frequency signal of frequency F,, modulated by a low-frequency reference signal f while transmitter B produces a high-frequency signal of frequency F 1 and transmitter C produces a high-frequency signal of frequency F 1 +f,,.
  • the signals are received at a known fixed point D.
  • the HF signal produced by A is demodulated in order to obtain an audio frequency for reference purpose, and the doublet system F F +f is mixed in order to obtain an audio frequency referred to as a position-finding signal.
  • the audio frequency reference and position-finding signals are compared with one another and as a result one of the transmitters B, C is controlled in order two keep said to audio frequency signals in phase.
  • the result is that the frequency difference f, of the doublet system of high-frequency signals produced by the transmitters B and C, will always be strictly equal to the frequency f of the audio frequency signal modulating the high-frequency signal produced by A.
  • a high-stability for example 10'
  • each group of signals likewise three transmitters A, B and C, are used.
  • the transmitters B, C' produce a doublet of signals, of frequency F and F +fo, which is received at a known fixed location D close to A.
  • the doublet F F, +f, is mixed in order to obtain an audio frequency f which is transmitted to the transmitter A where it is employed to modulate an HF carrier of frequency F the audio frequency signal thus transmitted being the reference signal.
  • the audio frequency reference signal always has the same frequency f as the audio frequency position-finding signal, but the stability of this frequency 1, of the reference signal is poorer than in the case of the single signal system.
  • each of these phases can be determined only in terms of its partial value, that is to say somewhere between 0 and Zn; there is thus a certain undetermined factor.
  • the coefficients k cannot be determined except for a certain constant (this is in addition to the indeterminacy of the number of complete revolutions or cycles), because of the arbitrary choice of the time origin.
  • the constant K is proportional to the frequency F or F f ⁇ , in accordance with the transmission characteristics, as a detailed calculation will illustrate.
  • the coefficient K corresponding to the audio frequency reference signal, has the value 0.
  • e will vary a little as the distance of the vehicle from the transmitter producing the reference signal varies, but this variation would have to reach a value of 3,750 km (in the case where f, Hz) in order for s to vary by 2rr.
  • lt can therefore be assumed that in the geographical range envisaged, the phase of the reference signal does not vary, hence the term reference.
  • the reference signal can be transmitted from any point, for example from one of the transmitters B or C (in other words, in the case of FIG. 1, A coincides with B or C), since its phase does not depend upon the location of the transmitter.
  • the characteristic frequency of the group will be that of the RF signal produced by transmitter C (F f0) and K will be proportional to F +f
  • the characteristic frequency of the group will be F
  • the characteristic frequency of the group may be made equal to F 1 or F +f it being understood of course that one is then neglecting the variations in a difference between the correcting terms applied to k and k these terms respectively taking the form:
  • D 0,, D represent the respective distances of the vehicle from the points A, B and C;
  • c represents the velocity of light
  • k k that is to say the partial phase-shift between the two audio frequency signals at the known fixed point hereinbefore defined.
  • x represents the difference in the distances between M and the two transmitters of the doublet system.
  • the quantity x can be expressed in any desired unit and all that is necessary is that the element which records or displays it shall be able to do so in a manner which indicates its total possible variation. Its total possible variation is equivalent to its variation between the two transmitters of the doublet system.
  • phase difference e e is constant when x is constant, that is to say that the phase difference is constant around a hyperbola having the two transmitters of the doublet as its foci. If s Q, is known, it is therefore possible to situate the vehicle on such a hyperbola; if there are three other signals available, transmitted by two other transmitters in order to establish another hyperbola, then the point of intersection between the two hyperbolae will represent the position of the vehicle.
  • F 2 is chosen to be close to F, in order to obtain a family of hyperbolae exhibiting channels of slightly different width to the width of the channels associated with the earlier family.
  • F is chosen at 310 kHz so that a channel corresponds to a variation of about 970 meters in x.
  • phase-shifts This difference between the phase-shifts is itself a phase-shift and will not amount to a full revolution or cycle until x has undergone a variation of 30 km. There is still an ambiguity but this can be removed by a different measurement, for example by taking a sight with a sextant.
  • the different signals are processed in a sequential manner.
  • the apparatus processes simultaneously each pair of audio frequency position-finding and reference signals of one and the same group, in other words, it handles them as an inseparable pair; in other words, the k, values are then variables as a function of time and this means that the phase 6 of the signal taken on its own, conveys no sense. It is only the phase-shift between the two signals of the same pair when considered simultaneously, that conveys any sense since the coefficients k, of the two signals are rigidly linked with one another, In the twosignal case, therefore, it is exclusively the measurement of the phase-shift between the audio frequency position-finding and reference signals, which provides any useful information.
  • phaseshift between the audio frequency reference and position-finding signals of one and the same pair can be written:
  • a difference detector 3 memories d, 5 and 6 for coefficients k,,, k and k a memory 7 for a quantity x; a control unit 8 which supplies a local signal of the same audio frequency as the signals applied to the input 2, and which is applied to the second input 9 of the interval detector 3; and units Ill and 11 for producing a quantity y and a memory 12 for storing same.
  • the first audio frequency position-finding signal of phase and characteristic frequency 6 k, k x; F, 300 kHz the second audio frequency positionfinding signal of phase and characteristic frequen- Cy 2 k2+K2x; F2: kHz.
  • sequence will be employed to designate the time interval devoted to the processing of each signal: each cycle of the receiving programme obviously contains a certain number of sequences and at least as many as there are signals to be processed.
  • the receiver Stored in its memory 4, the receiver contains a coefficient k, representative 'of a phase.
  • the control unit applies to the other input 9 of said same detector a local reference signal of phase 4),, k, and frequency identical to the reference frequency (for example 80 l-lz).
  • the control unit applies to the other input g of this detector a local signal of phase ii, k, K, x (k', being the coefficient which represents a phase and which is stored in the memory 5) and of the same frequency as the first audio frequency position-finding signal (e.g. 80 Hz).
  • the difference detector 3 compares the phases of the audio frequency position-finding and local signals. If it determines a phase difference of 41 then the latter is used to more or less completely correct the value of k in the memory 5.
  • control unit will establish a new local signal on the basis of this corrected k value, and indeed until in other words The same procedure is gone through during each reception cycle, in respect of the second audio frequency position-finding signal, so that if k, is the coefficient representing a phase and stored in the memory 6, ultimately the following will result:
  • the error made by storing k instead of k provides us with information on the error made by storing x instead of x. This arises from the fact that the stored k, and x values are used to produce a local signal which is in phase with the audio frequency position-finding signal, and that an error in one of the elements affects the other element.
  • the values of the quantities k are known with the exception of a constant which is a function of the arbitrarily chosen time origin.
  • a constant which is a function of the arbitrarily chosen time origin.
  • the product K, (x x) which is homogeneous at a phase and therefore at an angle may be substantially greater than 2nand comprise a certain number of full revolutions so that the equation:
  • fractional part of K (x x' the term fractional part being intended to convey a fractional part of a revolution thus, if 8, is expressed in radians, a quantity between and Zn.
  • the coefficients should be simple ones (in most cases they will be equal to +1, 0 or l) in order not to excessively increase the value of the probable difference in the final result; they are fixed by design considerations.
  • the coefficients a should be selected in such fashion that the unknown constant affecting each 8, value is eliminated and that A, is known without any uncertainty than that of the whole number of 271' values (ambiguity).
  • This operation is effected with a sensitivity factor 2, 01,, K, which is the weaker the larger the difference at x can be made; thus, a rough position for x will be obtained, making it possible to considerably reduce the value of the difference x x.
  • the operation will be repeated by selecting other coefficients 01,, in order to improve the sensitivity factor 2, a,, K, and thus obtain a more accurate position for x.
  • the A, values can be regarded as linear combinations with whole number coefficients, of the k, values and, in practice, the quantities A, will be produced directly from the coefficients k,.
  • FIG. 3 a unit 10 has been illustrated, in which a quantity A, is generated such that The differences k, k, and k, k, are completely determined since a common time origin is taken for the k, values and likewise for the k, values (taking into account these differences, brings about the elimination of the unknown constants involved in the determination of the k, and k, values).
  • A1 k g k in other words A, represents the difference between the two coefficients k, and k, stored in the memories 5 and 6.
  • A is used to influence x in such a way as to reduce A, to zero and thus to cancel out the difference x x.
  • k, and k are influenced in proportions such that the (,5, functions determined by the control, are not modified; in other words, it has been assumed that the vehicle is at a standstill (therefore 6, constants) so that at all times we have s, d), and therefore up, 0. Because of the fact that x tends towards x, the 8, quantities tend towards 0 or, in other words, the k, coefficients tend towards their real value k,.
  • the sensitivity factor of this correction of x is (K, K,) this corresponding to correction channels having a width of 15 km (on the base line) starting from the hypothesis made earlier in which F, 300 kHz and F 310 kHz.
  • the sensitivity factor of this new correction is K corresponding to channels having a width of 500 meters (on the base line) and always based on the hypothesis that F 300 kHz; the determination is thus a much more accurate one than the foregoing one.
  • the receiver may also be arranged to process other HF signals (for example F 350 kHz) enabling a third audio frequency position-finding signal to be produced and thus making it possible to obtain a quantity A ergo which would enable an intermediate mean sensitivity factor correction (K K to be effected, corresponding to channel widths bass of 3 km (on the base line).
  • other HF signals for example F 350 kHz
  • K K intermediate mean sensitivity factor correction
  • the receiver comprises, additionally, a velocity memory or store 12, the content v of which represents in magnitude and sign the velocity of the variation in the unknown x, which variation is due to the movement of the vehicle.
  • This velocity information is supplied to the store through the medium of the differences 11:, coming from the phase difference detector 3.
  • the store 12 produces a continuous variation in the content x of the store 7.
  • the value v stored in the store 12 truly corresponds to the real velocity of the vehicle, then the variation in x will follow that in x and consequently the difference x x, and therefore the quantities 8, and A will' that corresponding to the highest sensitivity (A in the case of FIG. 3), in order to influence not x but the v value stored in the velocity store 12, this through the agency of the link 13. In other words, as soon as x' commences to diverge from x, the quantity A taken will adopt a value other than zero. It will then immediately influence the content of the velocity memory in the desired sense, so that x varies more rapidly or more slowly, as the case may be.
  • the mode of operation of the receiver is as follows:
  • the A value of the fine regulating system (A is employed to more accurately determine the x value thus produced, x then being furnished in the form of a number; a determinate and unambiguous hyperbola (the hyperbola on which the vehicle is located).
  • the value v stored in the velocity memory is make 0.
  • the differences #1 are used to determine said v value (velocity taken into account).
  • the intersection ofwhich with the first determines the position of the vehicle, it is of course possible to employ a second receiver identical to the one just described.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Fittings On The Vehicle Exterior For Carrying Loads, And Devices For Holding Or Mounting Articles (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)
US838943A 1968-07-05 1969-07-03 Radio direction-finding method and a device for implementing said method Expired - Lifetime US3689926A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3754260A (en) * 1971-12-02 1973-08-21 Beukers Labor Inc Loran-c third cycle identification through the use of omega
FR2500168A1 (fr) * 1981-02-16 1982-08-20 Juzhnoe Proizv Obiedin Phasemetre numerique d'asservissement
FR2500171A1 (fr) * 1981-02-13 1982-08-20 Mlr Electronique Procede de radio-localisation par determination de phases d'ondes electromagnetiques et dispsositif recepteur pour la mise en oeuvre de ce procede
US4492963A (en) * 1983-10-05 1985-01-08 Eg&G, Inc. Method and apparatus for determining lane count error in a radio navigational system
EP0159844A3 (en) * 1984-04-19 1986-08-20 Cubic Western Data Multi-frequency lane identification system
US20030066345A1 (en) * 1997-01-02 2003-04-10 Kuo-Wei H. Chen A system and method of transmitting position data

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3214759A (en) * 1962-04-19 1965-10-26 Seismograph Service Corp Apparatus for providing lane identifi, cation in hyperbolic position finding systems

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3214759A (en) * 1962-04-19 1965-10-26 Seismograph Service Corp Apparatus for providing lane identifi, cation in hyperbolic position finding systems

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3754260A (en) * 1971-12-02 1973-08-21 Beukers Labor Inc Loran-c third cycle identification through the use of omega
FR2500171A1 (fr) * 1981-02-13 1982-08-20 Mlr Electronique Procede de radio-localisation par determination de phases d'ondes electromagnetiques et dispsositif recepteur pour la mise en oeuvre de ce procede
EP0059138A1 (fr) * 1981-02-13 1982-09-01 M.L.R. Electronique Procédé de radio-localisation par détermination de phases d'ondes électromagnétiques et dispositif récepteur pour la mise en oeuvre de ce procédé
US4547777A (en) * 1981-02-13 1985-10-15 M.L.R. Electronique Method of radio-position-finding through determination of phases of electromagnetic waves and receiving device for practicing the method
FR2500168A1 (fr) * 1981-02-16 1982-08-20 Juzhnoe Proizv Obiedin Phasemetre numerique d'asservissement
US4492963A (en) * 1983-10-05 1985-01-08 Eg&G, Inc. Method and apparatus for determining lane count error in a radio navigational system
EP0159844A3 (en) * 1984-04-19 1986-08-20 Cubic Western Data Multi-frequency lane identification system
US20030066345A1 (en) * 1997-01-02 2003-04-10 Kuo-Wei H. Chen A system and method of transmitting position data
US6968737B2 (en) 1997-01-02 2005-11-29 Lucent Technologies Inc. Position determining system using transmitted position information

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FR1586676A (OSRAM) 1970-02-27

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