Патент USA US3032759код для вставки
May 1, 1962 RT. HART 7 3,032,751 DATA TRANSMISSION SYSTEM FOR TELEMETERING Filed Dec. 14, 1960 MIXER l2 DATAf INFO (fl + f2) 0R 2 (fl-f2) FILTER / fl AND (f|+f2) OR REFERENCE ,5 fl AND (f|"f2) F/G / (fl'l' f2) OR (f|-f2)} = MIXER 2/ FILTER f2 f2 FILTER DATA OUT 24 \25 27 26 / f| 4% REF OUT 0.0. e /\ _ l DATA: _______C_.>| 1/ i | REFERENCE f‘ \l______; I' 27: PHASE POLAR'TY L____J‘ (26 3/ F/G‘ 3 INVEN TOR. ROBERT 7.’ HART BY AGENTS 3,032,751 Patented May 1, 1962 2 _ The basis of the telemetering system of the present 3,032,751 'I‘ELEMETERlNG invention resides in the combination at the transmitting DATA TRANSMISSION SYSTEM FOR station of a reference and data signal to produce a third Robert T. Hart, Richardson, Tern, assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation of these three signals over the transmission medium (wire or radio). The receiving station is adapated to separate the transmitted signals to regain the data signal in its of Iowa Filed Dec. 14, 1960, Ser. No. 75,760 5 Claims. (Cl. 340-198) Signal and the subsequent transmission of a selected pair original form. With reference to FIGURE 1, the trans mitting station is seen to comprise a reference signal This invention relates generally to data transmission 10 source 11 designated at frequency h. The transmitting and more particularly to a data transmission system for telemetering. The art of telemetering encompasses the transmission of information de?ning numerous conditions such as tem perature, velocity, shaft position, etc. The transmission of information may be through wire means or a transmis sion medium such as radio vwaves. Unlike communica tion systems for voice and other types of communication data, a telemetering system ofttimes necessitates that a station further comprises a second frequency source 10 in the form of a data information signal f2. It is to be understood that the intelligence to be transmitted will be imposed on the data information signal f2 such that the 15 intelligence may be regained by a comparison between the data information signal f2 and the reference signal f1. Each of the signal sources ]‘1 and f2 is applied to a mixer 12. The reference signal fl is applied to mixer 12 through connector 13 and additionally to the output line comparison or exacting reference be transmitted along 20 15. Mixer 12 develops outputs in the form of (fl-H2) and (f1—-f2), either of which may be selectively passed with the transmission data in order that the receiving by a band-pass ?lter 14 to the output line 15. Depend means may re-create the transmitted intelligence. For ing then upon the choice of ?lter 14, the output line 15 example, a telemetering system may involve the trans is impressed with a composite signal which may be either mission of a signal which may be in the form of a very low frequency alternating-current signal or, perhaps, a 25 A and (f1+f2) or )‘1 and (f1—;f2). Thus, the transmis sion consists of the reference signal f1 together with the direct-current signal and such information may be mean sum of the reference and data signals or the difference ingless unless the reference with respect to which the between the reference and data signals; the latter being data signal was created or measured is precisely recreated selected by band-pass ?lter 14. The output line 15 may at the receiving station. A commonly employed tech nique for re-creating a reference at the receiving station 30 be considered to connect to the transmission medium which might be a wire or a radio transmitting and receiv is the generation of a like reference at the receiving sta ing system. The system is independent of this medium tion with a synchronizing signal being transmitted to and, therefore, no speci?c illustration thereof is included obtain a system of automatic frequency control at the in the drawings. receiver. In such systems, however, errors may be in FIGURE 2 represents the receiving station of the pres troduced due to synchronization drift and phase shift and 35 ent invention where the transmitted combination signal amplitude variations which may be introduced by the (illustrated as input 15’) is applied to an ampli?er 16. transmission medium. Such errors may be inevitable It is to be understood that should the transmission medium whether the transmission medium be a direct wire or a be radio, the functional representation of FIGURES 1 radio transmission medium. The present invention has and 2 would include conventional transmitting and re an object therefore of providing a telemetering system ceiving equipment (not illustrated). The receiving sta of high versatility which exhibits less dependence upon tion of FIGURE 2 functions to re-create the data and the transmission medium in maintaining accuracy by in reference signal in their original form and this is accom corporating a common reference at the transmitting and plished by a selective ?ltering and mixing scheme as fol receiving ends of the system rather than by re-creating 45 lows. Output from ampli?er 16, which may be expressed a reference at the receiving end. as either ]‘1 and (fl-H2) or f1 and (f1—f2) (as deter A further object of the present invention is the provi mined by the bandpass action of ?lter 14 of FIGURE 1), sion of a telemetering technique wherein the relationship is applied through parallel channels 17 and 18 to ?lters 19 between data and reference signals is a constant and is and 20 respectively. Filter 19 is a band-pass ?lter with independent of the constants of the transmission medium. the same characteristic as ?lter 14 of FIGURE 1. Filter Still a further object of the present invention is the 19, as illustrated, passes either (fl-H2) or (fr-f2). Fil provision of a telemetering system relatively noncomplex ter 20 passes only the reference frequency f1 and passes as compared to known systems with a decided improve signal f1 to the reference output line 26. The reference ment in accuracy and versatility. signal 1‘, from ?lter 20 is additionally applied through The present invention features a unique signal mixing scheme whereby the reference signal may be exactly re 55 connector 23 to a mixer 21. The output from ?lter 19 produced at the receiver in a manner such that the data signal may vary either in phase or amplitude with re spect to the reference due to the maintenance of a pre cise amplitude-phase relationship between the data and reference signals throughout the system. These and other objects and features of the present in vention will be apparent from a reading of the following description in conjunction with the accompanying draw is applied as a second input to mixer ‘21. Mixer 21 develops an output 24 which is a re-creation of the data information signal 1‘; and the fa component is selectively passed by a further band-pass ?lter 25 to the data output 27. With further reference to FIGURE 2, an AGC regu lator is associated with the reference signal ]‘1 and is com mon to both channels 17 and 18. The f1 reference out put from ?lter 20 is seen to be connected through con ings in which: FIGURE 1 is a functional block diagram of the trans 65 nector 27 to the regulator 28. The output 29 from regu later 28 is applied to ampli?er 16. Thus, the system pro mitting station of the system, vides a constant amplitude reference signal by maintain *‘WFIGURE 2 is a functional block diagram of the re ing the gain of the system constant. The relationship be ceiving station of the system, and tween the data and reference signals is, therefore, a con FIGURE 3 is a functional diagram of an embodiment of the systems of FIGURES 1 and 2 wherein a shaft posi 70 stant relationship and is not dependent upon the constants of the transmission medium. tion may be precisely telemetered as a function of phase The operation of the system might be further illus shift between reference and data signals. 3,032,751 3 trated by a speci?c example. From an analysis of the mixing scheme, it is apparent that the reference signal f1 and the data signal f2 may be chosen as being equal, wherein (f1+f2)=2f1=2f2 and (fr-)3) is equal to zero. Thus, one might choose f1=f2=l500 c.p.s., where (f1-i-f2)\=30O0 c.p.s. and (f1—f2)=O. With this choice of frequencies, ?lter 14 of FIGURE 1 would pass mer-ated above have been operated with highly satisfac tory results and have exhibited greater accuracy and less dependence upon the transmission medium than known systems. The present invention is seen to provide a telemetering system employing a unique application of known ele ments in a less complex and more accurate system and (fl-H2) or 3000 c.p.s. and two signals would be trans which exhibits less dependence upon the transmission mitted through the transmission medium; 1500 c.p.s. medium by the novel incorporation of a common refer reference and 3000 c.p.s. containing the data information 10 ence at both the transmitting and receiving stations. f2. In this example, a single 3000 c.p.s. voice channel Although this invention has been described with re would provide su?icient bandwidth. At the receiving spect to a particular embodiment thereof, it is not to be station of FIGURE 2, the 1500 c.p.s. reference signal and so limited as changes might be made therein which are the 3000 c.p.s. signal containing the data signal are am within the true scope of the invention as de?ned in pli?ed in the gain stabilized ampli?er 16. Filter 19 would 15 the appended claims. pass (fl-H2) or the 3000 c.p.s. signal, while ?lter 20 would pass the 1500 cps. reference signal f1. Mixer 2;’: would develop an output (f1+]‘2)-f1=f2, which would I claim: 1. A data transmission system comprising a signal transmitting source and a signal receiving source, said be selectively passed by ?lter 25 to produce the original transmitting receiving sources being separated through a f2 data signal at exactly the same frequency as that at the transmitting station ‘and with amplitude and phase linearity limited only by the mixers and associated am transmit medium, means for generating at said transmit ting source a reference signal f1 and a data signal f2, said data system being variable in a predetermined manner with respect to said reference signal, mixing means re As previously discussed, the data signal f2 may be varied ceiving said reference signal f1 and said data signal f2, pli?er capabilities. either in a phase or an amplitude relationship with re 25 a ?rst band-pass ?lter receiving the output from said mix spect to the reference signal. FIGURE 3 illustrates an ing means and selectively passing a predetermined mixing embodiment of the telemetering system wherein the sys tem may be incorporated to develop a direct-current volt age output proportional to the phase displacement be tween the reference signal fl and the data signal f2 as a function, for example, of a shaft rotation at the re ceiving station. With reference to FIGURE 3, the input data signal f2 might ‘be developed from an electromechani cal resolver 32. Reference signal fl is applied as a refer ence input 11 to the circuitry of FIGURE 1 and is applied additionally to the rotor 32:: of the resolver 32. Stator winding 32c of resolver 32 then develops a signal f2 at ‘the h frequency but displaced in phase by an angle ¢ with respect thereto. The outputs 26 and 27 from the product of f1 and f2, the output from said ?rst band-pass ?lter and said reference signal applied through said trans mission medium to said receiving means; said receiving means comprising second and third band-pass ?lters re ceiving said transmitted signals and selectively passing said mixing product and said reference signal respectively, a second mixing means receiving the outputs from said second and third band-pass ?lters, a fourth band-pass ?l ter receiving the output from said second mixing means and selectively passing said data frequency component f2, whereby the outputs from said second and fourth ?l ters correspond respectively in frequency and phase to said signal f1 and data signal f2 developed in said trans receiving circuitry of FIGURE 2 would then be respec 40 mitting source. tively the reference signal f1 and the data signal 54¢. 2. A data transmission system comprising means for These signals are applied to a phase discriminator oil to develop a direct-current voltage output 31 with magni tude proportional to the phase shift </>. Phase shift qb, in turn, would be proportional to an angular mechanical input 34 representing, ‘for example, a shaft rotation of the generating a reference signal and a data signal, said data signal ‘being variable with respect to said reference sig nal, means for combining said reference» signals to pro duce the sum thereof and difference therebetween, means for selecting one of said sum and difference signals for resolver rotor 32a through an angle 6 with respect to the transmission through a medium to a receiving means; said rotor 320. receiving means comprising ?rst and second selective ?l The versatility of the telemetering system of the pres tering means to respectively pass said reference signal ent invention enables a wide variation in system opera and said selected signal, mixing means receiving the out tion. For example, at the transmitting station of FIG 50 puts from said first and second ?ltering means, third ?l URE 1, a direct-current voltage might be developed in— tering means receiving the output from said mixing means dicative of some parameter to be telemetered such as, and passing the component thereof corresponding to said for example, a temperature or a pressure. This direct current voltage might be fed to a chopper to produce a data signal. 3. A data transmission system as de?ned in claim 2 reference signal h of 1500 c.-p.s. and the data signal might 55 further including automatic gain regulating means receiv then be developed as an output of either 1500 c.p.s. vari ing the output from said ?rst ?ltering means, said regu able phase or a variable amplitude as the station de manded. Still a further telemetering situation to which the pres ent system is readily adaptable might be one wherein an alternating-current signal of a lower frequency is to be accurately relayed from the transmitting station to the receiving station. This signal could be applied to a chopper to convert to 1500 c.p.s. information and, at lating means connected to and controlling the amplitude of said reference signal and said selected signal as ap plied to said receiving means. 4. A data transmission system as de?ned in claim 3 wherein said reference signal and said data signal are equal in frequency, said selected signal equally the sum of said reference and data signals, said ?rst ?ltering means selectively passing said reference signal and said second the receiving station, a direct-current voltage might be 65 ?ltering means selectively passing the sum of said ref developed from. the 1500 c.p.s. data signal and a lower erence signal and said data signal, said third ?ltering frequency signal might be re-created by using an addi means selectively passing said data signal. tional chopper. The lower frequency alternating-current 5. A data transmission system as de?ned in claim 4 signal could then be recovered at the receiving station. including data signal developing means for producing a Although the speci?c examples illustrated herein were 70 data signal f2 equal to ii Let’), the outputs of said ?rst and based upon the selection of a 1500 c.p.s. reference and second ?lters being applied to phase discriminating means, data signal, it is to be emphasized that the system lends said phase discriminator means adapted to provide a itself to a wide variation in choices of frequencies f1 and direct-current voltage output proportional to the data phase shift angle 45. f2 consistent with the frequency separation capabilities of the various band-pass ?lters. Each of the schemesvenu 75 No references cited.