Патент USA US2405174код для вставки
: A. ALFORD 2,495,174 TRANSMI S S ION CONTROL. NETWORK Filed May 27,} 1942 , 5 . ~_/J_\_. 5x, _ _ YlNVENTOR' ' BY Patented Aug. 6, 1946 2,405,174 UNITED STATES PATENT OFFICE} 2,405,174 ( TRANSMISSIGN CONTROL NETWORK Andrew Alford, New York, N. Y., assig'nor to Mackay Radio and Telegraph Company, New York, N. Y., a corporation of Delaware Application May 27, 1942, Serial No. 444,660 4 Claims. (Cl. 178-44) 1 This invention relates to high frequency trans mission systems and more particularly to im 2 line 2, to a load impedance 3 which is made sub stantially equal to thecharacteristic impedance pedance matching networks for high frequency of line 2, In such a transmission line there will lines. be no standing waves. If, then, a conductor 4 It is often necessary to provide high frequency is coupled to the line it is found that standing ‘lines with networks or the like in order that the waves are produced on the line, as shown at 5. line may be matched in impedance with a load. The conductor has a characteristic impedance A number of such systems have been proposed of Z0’ and a length 1. With such a relationship such as short sections of transmission line, it is found that the spacing of the conductor commonly called building-out sections, or other 10 from the standing waves maximum, Imax is given networks coupled to the line. In many cases it by the value P. Since such a network is capable is found that the known forms of networks may of producing standing waves in a matched line, be undesirable because of the difficulty of apply it is clear that a similar network applied in a ing them to installations already existing or be transmission line normally having standing cause of their size or position. 15 waves of the same Imax to Imin ratio as the waves It is an object of my invention to provide an 5, and spaced the same distance P from the Imax impedance adjusting network which is readily position will serve to match the frequency of the applied to any transmission line and which is line to the load in accordance with the reci relatively small and light so that it will not add procity theorem. materially to the weight or wind resistance of a 20 In Fig. 1A is shown such a system in which line when applied thereto. the source I is connected over a transmission According to a feature of my invention the line 2 to a load 3a, the line normally having stated objects may be achieved by coupling to standing waves as indicated at 5a. The network the transmission line a conductor of given char 4 of length Z and characteristic impedance Z0’ acteristic impedance value, the length being de 25 serves to match the impedance of the line as il termined by the characteristic impedance of the lustrated in this ?gure. It can be seen that this line and the standing wave ratio in the line and form of network will readily serve to secure im the position along the line being determined by pedance match in most transmission lines if the the selected length and the characteristic im proper dimensions and position are chosen. Fur pedance of the line. thermore, since the network is of small vertical A better understanding of my invention and dimension it will exert very little bending stress the objects and features thereby will be had by on the line during high winds or the like, and is, the particular description thereof made with ref therefore, particularly Well suited for use on open erence to the accompanying drawing in which wire high frequency transmission lines which Figs. 1 and 1A are diagrams used to explain 35 are exposed to the weather. the principles of my invention; In order properly to select the desired network Figs. 2 and 3 are curves showing characteris of dimension to satisfy the impedance matching tics of networks used in myjnvention; requirement, it is possible to provide curves to Fig. 4 illustrates one form of my invention ap aid in its selection. Such curves are illustrated plied to a line feeding an antenna. 40 in Figs. 2 and 3. ' Fig. 5 illustrates a further modi?cation of my In Fig. 2 is shown a family of curves, repre invention; and senting different values of the ratio of charac Fig, 6 illustrates still another form of my in teristic impedance Z0v of the line to the charac vention. teristic Z0’ of these networks, plotted with the The conventional forms of impedance match 45 length of the units in electrical degrees against ing networks are often cumbersome, particularly the standing wave ratio Q, that is when used on high frequency supply leads to radio antenna. I have discovered that an im pedance matching may be achieved by use of a simpler network consisting of a relatively long 50 Fig. 3 then shows a set of curves for determining narrow conductive arrangement fastened to the the spacing P, the spacing 'P being shown in conductors, In Fig. 1 the effect of the network is demon electrical degrees plotted against the length Z in electrical degrees. strated. In this arrangement a high frequency When it is desired to apply a network to match source I is shown connected over a transmission 55 a given standing wave ratio in a line, the curves 3 2,405,174 4 length of the units may be determined by the of Fig. 2 are ?rst consulted. Assume, for exam ple, the standing wave ratio is 3. It is seen that number of loops added to the line, so that the proper adjustment and length can be easily made there are three sets of networks which will be satisfactory depending upon the characteristic in the ?eld. While the impedance of such networks as impedance of the networks which it is desired to use. The characteristic impedance of the net shown at 61, 62, may be calculated, this calcula tion is quite involved and it is often more feas work may be readily calculated for any ?at metal ible to ?nd the impedance thereof by experiment. objects of the type illustrated in Fig. 1 or for The impedance of such networks may be deter metal rod forms such as shown in Fig. 5. Ac cordingly, the desired width of plate or diameter 10 mined by use of the arrangement similar to that shown in Fig. 1. Since the standing wave ratio of rod is found by calculation and the length is on the line which is created by the unit networks then determined by reference to Fig. 2. We will assume ?rst that curve 22 is chosen. It will be can be readily measured, and the characteristic seen that this requires a network having a length impedance Z0 is known, the characteristic im of substantially 60 electrical degrees. Turning pedance of any unit of length I may be readily then to Fig. 3, the length Z found from Fig. 2 calculated after taking the measurements from is laid out on the horizontal axis, and the spac the known functions. In order to secure the required data loops of a particular size may be ing P can'then be determined from this. In the given example it is found that the spacing P must strung on a matched impedance line such as then be made of the order of 2.5 degrees from shown in Fig. 1, and the information as to the standing wave ratio produced thereby determined the current maximum. It is clear that any desired, impedance match for different lengths of network having a given ing network may be secured from a family of looping dimension. Thus, a family of curves curves as shown in Figs. 2 and 3. While only similar to those shown in Fig. 2 may be readily plotted experimentally. Likewise, the spacing P a few curves have been shown it is readily ap parent that the number of curves which may be may be determined at the same time and a set provided is substantially in?nite, and, therefore, of experimental curves similar in type to that the variety of networks that can be provided in shown in ‘Fig. 3 may be plotted. When it is de accordance with my invention is also in?nite. sired to match the impedance of a transmission One advantage of the ?at sheet-like network 30 line, the standing wave ratio of the line may be is that it may be readily applied and adjusted ?rst measured and the desired length of loop net experimentally without reference to the curves. work may be derived from the sets of curves in In Fig. 4. is illustrated an arrangement in which a similar manner to that previously described. transmission line 48 is coupled to a dipole an When this has once been determined all that is tenna 4|. Matching sections 42, 43 are provided necessary is to fasten the conductor forming the in each of the lines. If these sections are found loops to the transmission line at one point and to be too short, additional sections 44, 45 may be proceed to make the number of intermediate loops hung on the ends thereof. Further, if the sec necessary to produce the desired length of net~ tions 42, 43 are found to be too long they may work. It is, therefore, seen that this particular be readily trimmed oif, being made of light sheet 40 form of network arrangement shown in Fig. 6 is readily applicable to transmission lines in the metal. ' In Fig. 5 is illustrated how another form of ?eld and may be applied by any attendant who is network comprising sections of line 52, 55 of in charge of the transmission lines. different diameter than the conductors of line 13!} While I have disclosed speci?c apparatus for may be applied to the line. The impedance of 45 accomplishing this result in accordance with my the line sections may be readily calculated and invention, it should be distinctly understood that they may be applied to the line by use of the these are given merely by way of example, and diagrams of Figs. '2 and 3 or similar diagrams not as limitations. In fact, ‘any desired form calculated for this form of conductor. - of impedance network can be used so long as While the solid metal arrangements shown in ’ the conductor is chosen with respect to the unit Fig. 4 may be provided to secure the desired im impedance value and taking into consideration pedance matching, such elements may be unde the characteristic impedance of the line, the standing wave ratio of the line and the proper sirable on outside lines due to the wind resistance. position determined by this characteristic im It is therefore clear that in place of solid metal sheets as shown therein wire screening or netting 55 pedance and the selected length. What is claimed is: may be used. Although sheets of screening or thin metal 1. In a high frequency transmission the com bination comprising a high frequency transmit may be provided for achieving the impedance ting line complete in itself for transmitting en matching as described above, it is often desir ergy to a load, a separate readily applied im~ able to build up units in the ?eld out of wire pedance matching network comprising conduc loops. In Fig. 6 is shown a form of network ap plied to a transmission line 46 connected to an tive means having a given characteristic imped ance connected to a conductor of said line antenna 4!, in ‘which each of the units BI, 52 throughout substantially the entire length of said comprises a plurality of small loops of wire fas tened to the transmitting conductor. If desired 65 conductive means, said conductive means hav ing an overall length determined from the selec these wire loops may be reinforced by a third tion of a characteristic among those existing be wire 63, 64, as shown. Such a construction is tween standing wave ratio in said transmission preferable to the netting or screening since the line and network lengths, for different ratios be openings are much larger and do not facilitate the formation of sheets of sleet. The impedance 70 tween characteristic impedance of said line and of networks including approximately said given matching with such networks as shown in 63, 764 characteristic impedance, and said conductive can be accomplished in a similar manner to that means having a position along said line with re described above. In addition, however, the net spect to the standing wave maximum of standing work such as shown at ‘El, 62, has the additional advantage overthe use of the sheets in that the 75. waves in said line determined by the selection of 5 2,405,174 6 one among the existing characteristics between network lengths and positions for di?erent ratios between the characteristic impedance of said line and of networks including approximately said given characteristic impedance. 2. An impedance matching network according existing characteristics between network lengths and positions for different ratios between the characteristic impedance of said line and of net K u to claim 1 wherein said conductive means com prises a metal sheet fastened to said conductor. 3. In a high frequency transmission the com works including approximately said given char acteristic impedance. 4. A high frequency transmission line system comprising a high frequency transmitting line including an impedance matching network com prising conductive mea-ns having a given charac bination comprising a two~conductor high fre 10 teristic impedance connected to a conductor of quency transmitting line complete in itself for said line, said conductive means having an over transmitting energy to a load, a separate readily all length determined from the selection of a applied impedance matching network compris characteristic among those existing between ing conductive means connected to each conduc standing wave ratio in said transmission line and tor of the line throughout substantially the en network lengths, for di?erent ratios between tire length of said conductive means, said con ductive means de?ning a predetermined area in the plane of said conductor and having a given characteristic impedance and an overall length determined from the selection of a characteristic characteristic impedance of said line and of net works including approximately said given char acteristic impedance, and said conductive means having a position along said line with respect to the standing wave maximum of standing Waves in said line determined by the selection of one among the existing characteristics between net work lengths and positions for different ratios between the characteristic impedance of said line among those existing between standing wave ra tio in said transmitting line and network lengths for different ratios between characteristic im pedance of said line and of networks including approximately said given characteristic imped ance, and said conductive means having a posi tion along said line with respect to the stand ing wave maximum of standing waves in said line determined by the selection of ‘one among the 25 and of networks including approximately said given characteristic impedance, said conductive means comprising a series of looped wires each terminating at said conductor. ANDREW ALFORD.