Patent Publication Number: US-2003222814-A1

Title: Global radiolocalization system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001] The present invention is based in the Spanish application for patent no. P200201304 dated Jun. 3, 2002, that is priority. The following patents are related with this invention:  
       [0002] EP0810449 improves the measures of the GPS with the Loran-C.  
       [0003] U.S. Pat. No. 6,032,902 about non-geostatationary constellations of satellites.  
       [0004] GB2380626, a terrestrial base sends a synchronization signal to a geostationary satellite, this geostationary satellite sends again said signal to some satellites placed on middle orbits, and these last satellites send again the signal the terrestrial base to correct the initial signal.  
       BACKGROUND OF THE INVENTION  
       [0005] The hyperbolical navigation systems Loran and Omega are adapted the satellite navigation according the new tecniques about the process of the digital signals.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006] The satellites R 1 , R 2  y R 3  are provided with radiostations to send the digital signals F 1 , F 2  y F 3  on the frecuencies f 1 , f 2  y f 3 . Each satellite is placed on an orbit of radius equal to the geostationary satellites, having the plane of the satellite orbit an angle less that 90° and more that 9° regarding the equator of the earth. In this case, the movement of the satellite in relation with the earth is shows as a regular movement as a “8”, raising/falling between +/− a maximal latitude (maximal latitude of the satellite), around an average meridian (longitude of the satellite). The three signals F 1 , F 2  y F 3  are synchronized, each signal having the following fields:  
       [0007] IE emission identifier,  
       [0008] IT emitter geography coordinates,  
       [0009] T emitter local time,  
       [0010] RS emitter delay of synchronization,  
       [0011] IR emission delay.  
       [0012] The global emision time of the signal from Ri is:  
       
         TEi=Ti+RSi+IRi  
       
       [0013] A satellite j is synchronized by j by calculating  
       
         RSj=Ti+RSi+IRi+|ITi−ITj|/c−tji  
       
       [0014] being:  
       [0015] |ITi-ITj|: distance between Ri and Rj,  
       [0016] t 21 : time of arrival of the signal Fi from Si to Sj, this time being measured with the clock of Sj (Sj local time).  
       [0017] A mobile X receives the signals F 1 , F 2  y F 3  at the times tx 1 , tx 2  y tx 3  (X local time) obtaining (IT 1 ,TE 1 ), (IT 2 ,TE 2 ) y (IT 3 ,TE 3 ). The distances between X and R 1 , R 2  and R 3  are:  
         dxi =( txi+RSx−TEi )/ c  ( i= 1, 2, 3),  
       [0018] RSx: the delay of synchronization of X (unknown)  
       [0019] being the distance differences:  
         dxi−dxj =( txi−txj )/ c −( TEi−TEj )/ c  ( i y j= 1, 2, 3).  
       [0020] Each Ri, Rj and dxi-dxj defines a revolution hyperboloid Hij. X is located near said Hij.  
       [0021] X measures its altitude Hx regarding the sea top (for example with a altimeter).  
       [0022] The center of the earth and the radius of the earth+Hx define a sphere Ex. X is located near said Ex.  
       [0023] With three signals are obtained 3.2/(1.2)=3 hyperboloids, having the next equation systems:  
       [0024] H 12 , H 23 , Ex.  
       [0025] H 23 , H 31 , Ex,  
       [0026] H 12 , H 31 , Ex,  
       [0027] another solution could be the center of a tangent sphere of minimal radius to the four surfaces H 12 , H 23 , H 31 , Ex. Total solutions 4.  
       [0028] With four signals are obtained 4.3/(1.2)=6 hyperboloids, having the next equation systems:  
                                                      H12, H12, H34,               . . .   (6.5.4)/(1.2.3)=20,           H12, H23, Ex,           . . .   (6.5)/(1.2)=15,           tangent spheres:   7.6.5.41(1.2.3.4)=35           Total solutions 70.                      
 
       [0029] Each solutions is an valuation of the position of X. The average of said valuation is a better valuation of X.  
       [0030] It is possible to obtain more that a solution for each equation system (also it is possible no solution). For each equation system, to pick up the correct solution is need having in account the sign of the dxi-dxj  
       [0031] if dxi-dxj&lt;0, the correct solution is more near Ri that Rj,  
       [0032] if dxi-dxk&lt;0, the correct solution is more near Ri that Rk,  
       [0033] . . .  
       [0034] Knowing X its position, X can synchronizes itself as a satellite Si, according the equation  
       
         RSx=Ti+RSi+IRi+|ITi−ITx|/c−txi,  
       
       [0035] from this point to lost the synchronization X can obtain distances to the satellites Ri, changing the hyperboloids by spheres.  
       [0036] Each signal Fi is obtained by sequencing the parallel bits of IEi, . . . , IRi with a pulse clock of period TM. The field T is obtained from a pulse clock of period TT, being TM&gt;&gt;TT.  
       TT                 is                 a                 fraction                   2   m                   of                 TM                     (     m   &gt;   1     )     .                   
 
       [0037] This binary signal Fi is amplified, modulated in the frequency fi and emitted.  
       [0038] Each receiver (Rj or X) tunes the frequency fi, this signal, demodulated and amplified, returns the signal Fi, then being sampled by a clock of period TM.  
       [0039] The range of time between the start time of IEi and the sampling time is measured for subtract of TEi. By this, being 10 the two last bits of IEi, a clock counter RRj is actuated by the pulses TT, being started by the penultimate bit of IEi and being stoped by the last bit of IEi. The pulses TT actuate the counter RRj through an AND door, being other entry of said door the signal Fi.  
       [0040] A receiver delay RRRj could be regarded.  
       [0041] So, the signal Fi enters in Sj or X at the time  
         TEi+|ITi−ITj|/c −( TM−RRj ) in global time  
       [0042] or  
       tj2+RRRj int local time (in Sj or X)  
       [0043] o similarly:  
       TEi+|ITi−ITj|/c in global time  
         tij=tj 2 +RRRj +( TM−RRj ) in local time (in Sj or X).  
       [0044] Also, the process of the signal Fi could be made for a computer provided with a modem for receiving (in Si and X) and another modem for emitting (in Si) if the internal clock of the computer could produce pulses of period TT and the receiving modem could measure RRj. By this, the receiving modem is modified by adding a counter RRjk and a serial port to receive the pusles TT from the computer. The counter is actuated by the pulses TT and the signal Fi through an AND door, starting with the pulses TM of the modem. The value RRjk is transmited the computer through a parallel port.  
       [0045] Between the 9° Nort and the maximal latitude of the satellites ever must be three satellites to be visible the Nort Pole. Three more satellites are need between the 9° South and the minimal latitude of the satellite (=-the maximal latitude), three more between the minimal and the maximal latitude raising and three more between the minimal and the maximal latitude falling. A suitable maximal latitude would be the intermediate latitude between 18° and 90°=54°.  
       [0046] A structure could be four constellation of satellites, each constellation comprising three/four equidistant satellites in longitude, all the satellites of the same constellation having the same latituded at each time. The constellations are intercalated in the way which all the satellites are equidistant in longitude.  
       [0047] Each satellite emittes a signal, and said satellite receives another signal from the satellite more near in longitude.  
       [0048] Any satellites could be synchronized by terrestrial radiostations.  
       [0049] If the case is 3 satellites/constellation (total 12 satellites) 12 frequencies are need, if the case is 4 satellites/constellation (total 16 satellites), 16/2=8 frequencies are need because for each satellite there is another satellite symmetrical regarding the earth center.  
       [0050] Ending, it is possible which all or some satellites j could be radiorepeater of a signal Fjt from a terrestrial radiostation t. In this case, the terrestrial radiostation sends the satellite the fields IE, . . . IR, according the next:  
       [0051] ΔT: transit time of the radiolocalization signal from the terrestrial radiostation  
       [0052] t to the satellite radiorepeater j,  
       [0053] Rj(T): function to obtain the satellite position j at the time T,  
       [0054] ΔT is calculates according to:  
       | Rj ( Tt+ΔT )− ITt|=c.ΔT    
       [0055] the fields IT y T are calculated according to:  
         ITj=Rj ( Tt+ΔT ) Tj=Tt+ΔT.    
       [0056] The terrestrial radiostation could be sincronized with the radiolocalization signal from the satellites, o with syncrhonizing signals from another terrestrain radiostation, in this last case, the syncrhonizing signals are also radiolocalization signal, and so could be used.  
       [0057] The previous paragraph permits to use comunication and television satellites for radiolocalization.  
     
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
     [0058]FIG. 1. Signals from the radiolocalization system.  
     [0059]FIG. 2. Geometrical problem to obtain a hyperboloid.  
     [0060]FIG. 3. Synchronization circuit of a satellite.  
     [0061]FIG. 4. Formation circuit of the satellite signal.  
     [0062]FIG. 5. Data captator circuit of a mobile.  
     [0063]FIG. 6. Pulses divider circuit.  
     [0064]FIG. 7. Signal identifier circuit.  
     [0065]FIG. 8. Basic comparator circuit.  
     [0066]FIG. 9. The computer-controlled system.  
     [0067]FIG. 10. Satellite sky projection.  
     [0068]FIG. 11. The movement of the satellite regarding the earth.  
     [0069]FIG. 12. Satellite fleet with 3 satellites/constellation.  
     [0070]FIG. 13. Signals from the radiolocalization system for radiorepeater satellites.  
     [0071] The representation of the logical doors are as following:  
     [0072] AND: triangle with several entrances and one exit,  
     [0073] OR: semicircle with several entrances and one exit,  
     [0074] NOT: triangle with one entrance and one exit, 
    
    
     DETAILED DESCRIPTION OF THE INVENTION AND FIGURES  
     [0075]FIG. 1. Signals from the radiolocalization system.  
     [0076] The terrestrial radiostation R 0  emits the synchronization signal F 0  (as a radiolocalization signal) and the satellites R 1 , R 2  y R 3  emit the radiolocalization signals F 1 , F 2  y F 3 . R 1  continually receives the signal F 0  being used as one synchronization signal, R 2  continually receives the signal F 1  being used as one synchronization signal, likewise R 3  continually receives the signal F 2  as synchronization signal and successively . . .  
     [0077] The mobile X to obtain its position, successively selects the frequencies of the signal F 1 , F 2  y F 3 , obtaining the hyperboloids H 12 , H 13 , . . .  
     [0078]FIG. 2. Geometrical problem to obtain a hyperboloid.  
     [0079] O is the earth center.  
     [0080] R 1  (r 1 ,l 1 ,L 1 ) (known)  
     [0081] R 2  (r 2 ,l 2 ,L 2 ) (known)  
     [0082] X (rx,lx,Lx) (unknown)  
     [0083] r: radius from O, l: latitude, L: longitude (geographical coordinates).  
     [0084] According the cosine theorem of the spherical geometry  
     [0085] cosD1=sinl1.sinlx+cosl1.coslx.cos(L1-Lx)  
     [0086] cosD2=sinl2.sinlx+cosl2.coslx.cos(L2-Lx)  
     [0087] While according the cosine theorem of the plane geometry  
               d1   2     =       r1   2     +     rx   2     -       2   ·   r1   ·   rx   ·   cos                   D1                     d2   2     =       r2   2     +     rx   2     -       2   ·   r2   ·   rx   ·   cos                   D2                           
 
     [0088] Being known d 1 -d 2 , subtracting the d 1  and d 2  of the previous ecuations, the hyperboloid ecuation H 12  is obtained.  
     [0089]FIG. 3. Synchronization circuit of a satellite.  
     [0090] The satellite Rj receives the synchronization signal from the satellite Ri through a radio-receiver  1  and a demodulator  2 , giving Fi which enters a signal identifier circuit  8  and a sampling circuit  9 .  
     [0091] The puse RS 1  from a cumputer  10  informs that the system is ready to receive data. RS 1  is changed into RS through the circuit  6 . This RS performs the following jobs:  
     [0092] starting the signal identifier circuit  8  and the sampling circuit  9 ,  
     [0093] fixing the record of Tj y ITj in the record Tj 2  y ITj 2  with the circuits  12 , each Tj 2  y ITj 2  is constant until new RS.  
     [0094] Each circuit  12  is a set of parallel links between for example the memory devices Tj and Tj 2 . These memory devices Tj 2  could be flip-flop DELAY type, being the input clock of said flip-flop the pulse RS.  
     [0095] The identifier circuit  8  verifies that the initial bits of Fi match with a record IE. By this a sampling signal TM is used. If nom-verification, a signal RS 0  is sent the circuit  6  which emits the pulse RS, re-starting the proccess. If verification, a signal CCC is sent. This identifier circuit has a counter RRj controlled by the two last bits of IEi ( 10 ). This counter uses the clock signal TT. Also, this identifier circuit is started by the pulse signal RS.  
     [0096] The sampling circuit  9  is controled by the sampling signal TM which only acts if the signal CCC=1 (by the AND door  11 ). This sampling circuit changes the serial bits of Fi (IT, T, RS and IR) into the parallel bits of the records ITi, Ti, RSi and IRi, then the sampling circuit emits a signal to inform the computer  10  that a set of data is ready.  
     [0097] The computer  10  obtains RSj with the value of the records ITi, Ti, RSi, IRi, RRj, Tj 2 , ITj 2  and RRRj:  
       RSj=Ti+RSi+IRi+|ITi−ITj 2 |/c −( Tj 2 +RRj+RRRj )  
     [0098] TM could be obtained from TT according the circuit  3 , being  4  the clock of the pulses TT and  5  an pulses divider circuit.  
     [0099]FIG. 4. Formation circuit of the satellite signal.  
     [0100] The satellite j emits the signal Fj thruogh a modulator  14  and an emitter  15 , being obtained Fj from the sequencer  13 .  
     [0101] A signal RS 0 B from said sequencer  13  informs that the system is ready to send a new set of data, being changed this signal RS 0 b in a pulse RSB through the circuit  24 . This pulse RSB fixes the record Tj, ITj y RSj on the record Tj 3 , ITj 3  and RSj 3  by mean of the 12, each Tj 3 , ITj 3  and RSj 3  is constant until new pulse RSB.  
     [0102] The pulse RSB also starting the sequencer  13 , begining to transform the parallel record IE, ITj 3 , Tj 3 , RSj 3  and IRj into the serial signal Fj.  
     [0103]FIG. 5. Data captator circuit of a mobile.  
     [0104] This circuit is very similar the circuit of the FIG. 3, being the differences:  
     [0105] the demodulator  25  is controlled by the pulses RS, changing the tuner frequency,  
     [0106] a computer  26  obtains the essential data set of each measure (tix, TEi,ITi), storing said data set into the computer memory,  
     [0107] ITx 2  is not an input data of the computer  26 , being a input data the altimeter Hx.  
     [0108] The computer  25  stores the data sets until said computer reaches the neccessary number of measures to calculate the position of X.  
     [0109]FIG. 6. Pulses divider circuit.  
     [0110] The m less significant bits of a counter which is actuates by the signal TT (for example the record Tj of the FIG. 3) are entered an AND door. The exit of said AND door is the pulse signal TM:  
       TT   =     TM   /     2   m                     
 
     [0111]FIG. 7. Signal identifier circuit.  
     [0112] The field IE has n bits, the last two bits ever are 10.  
     [0113] The bites IE 1 , . . . , IEn are identified with the basic comparator circuits CI 1 , . . . , CIn. Each CIk receives its IEk, the sampling signal TM, a signal CCCk- 1  from the previous basic comparator circuit CIk- 1  informing which the previous IEk- 1  has been identified, and the pulse RS. Each DIk giving the signal CCCk if IEk has been identified or RS 0 k if IEk has not been identified.  
     [0114] All the RS 01 , . . . , RS 0 n enter an OR door, exiting the only non identification signal RS 0  (circuit  23 ).  
     [0115] The record RRj are actuated by the pulses TT, but only when CCCn-1=1, Fi=1 and CCCn=0 (see AND door  17 ).  
     [0116]FIG. 8. Basic comparator circuit.  
     [0117] When CCCk-1=1, an AND door  18  permits the signal Fi to access the comparator  19 . If the exit of the comparator is 1, when one pulse TM actuates an AND door  20 , a flip-flop  22  changes its outlet 0 for 1. Due the AND door  21  the flip-flop  22  is started when the pulse RS.  
     [0118] The flip-flop is a JK type, T mode.  
     [0119]FIG. 9. The computer-controlled system.  
     [0120] All the said records (excepted RRj) could be memory variables of a computer  29 .  
     [0121] At the begining of the proccess, the computer defines a numerical array RRMM, dimension len(IEi)=n, to contain the data from the record RRM of a modem  31 .  
     [0122] Fi enters the modem  31 , being re-sends the computer  29  through the serial port  27 . Also Fi and TT from the computer through a second serial port  30  enter an AND door  26 , while the outlet of said AND door  26  actuates the counter RRM. This counter RRM is started by the signal TM of the modem. Fulthermore, the signal TM sends RRM to a parallel port  28 , then the computer shifts the array RRMM, inputing RRM at RRMM(1).  
     [0123] The computer makes the signal Fj according the valures of the devices IEj, . . . , Irj, being connected said devices to a local network  32 .  
     [0124] When the modem informs te computer  29  which one bit will be transmited  
     [0125] the computer receives the bit by the serial port,  
     [0126] the computer puts the last bits in the memory variables IEi, . . . , IRi,  
     [0127] if IEi=IEj there is a correct set of data, calculating RRj=min(RRMM(1), . . . , RRMM(len(IEi)),  
     [0128] if IEi⋄IEj the computer waits another bit from the modem, starting a new cycle.  
     [0129] So the function of the identifier circuit has been performed by a sentece type  
     [0130] IF IEi⋄IEj (to receive other bit) ELSE (to continue calculation).  
     [0131] Furthermore, the modem would be modified to change its frequency of modulation-demodulation continuosly into a fixed bandwidth, according with computer orders.  
     [0132] A specific port could be designed, having said port the performances of the two serial port and the parallel port.  
     [0133]FIG. 10. Satellite sky projection.  
     [0134] The FIG. 10 shows the geometrical spherical problem. The satellite S on the orbit OS being its radius regarding the earth center equal that the geostationary satellites, the intersection of the OS with the ecuator plane EC is an fixed axe OS-EC and the angle of the planes OS and EC is a fixed angle I less that 90°. Having in account said performances, easyly can be calculated the latitude LAT and longitude LON of the satellite regarding the sky sphere in at time, solving the spherical triangle characterized by the angles I, wt and 90°, being w=360°/24h.  
     [0135] Said sky coordinates are changed terrestrial coordinates by the ecuations:  
     [0136] Terrestrial LAT=Sky LAT  
     [0137] Terrestrial LON=Sky LON-wt  
     [0138]FIG. 11. The movement of the satellite regarding the earth.  
     [0139] A simple proyection is used:  
     [0140] x=terrestrial longitude  
     [0141] y=terrestrial latitude.  
     [0142] The movement of the satellite looks as a regular movement as a “8”, raising/falling between +/− a maximal latitude (maximal latitude of the satellite), around an average meridian (longitude of the satellite)  
     [0143]FIG. 12. Satellite fleet with 3 satellites/constellation.  
     [0144] At the time that the first satellite is at its maximal latitude:  
                                                               Satellite   Constelatiòn   Latitude   Longitude   Sense                                                                1   A   54   0   South           2   B   0   30   South           3   C   −54   60   Nort           4   D   0   90   Nort           5   A   54   120   South           6   B   0   150   South           7   C   −54   180   Nort           8   D   0   210   Nort           9   A   54   240   South           10   B   0   270   South           11   C   −54   300   Nort           12   D   0   330   Nort                      
 
     [0145]FIG. 13. Signals from the radiolocalization system for radiorepeater satellites.  
     [0146] This figure shows the terrestrial radiostation R 0  feeding the satellites R 1  and signals R 3  with the signals F 10  and F 30 , while the satellite R 3  syncrhonizes the terrestrial radiostation R 4  with the repeater signal F 30 .  
     [0147] Naturally, the synchronization circuits and the formation of signal circuits are into the trial radiostation.