US2238438A - Electrical network - Google Patents

Electrical network Download PDF

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Publication number
US2238438A
US2238438A US12451A US1245135A US2238438A US 2238438 A US2238438 A US 2238438A US 12451 A US12451 A US 12451A US 1245135 A US1245135 A US 1245135A US 2238438 A US2238438 A US 2238438A
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US
United States
Prior art keywords
impedance
line
network
loop
frequency
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US12451A
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English (en)
Inventor
Alford Andrew
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mackay Radio & Telegraph Co
MACKAY RADIO AND TELEGRAPH Co
Original Assignee
Mackay Radio & Telegraph Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mackay Radio & Telegraph Co filed Critical Mackay Radio & Telegraph Co
Priority to US12451A priority Critical patent/US2238438A/en
Priority to NL76769A priority patent/NL43581C/xx
Priority to GB7648/36A priority patent/GB457911A/en
Priority to FR806803D priority patent/FR806803A/fr
Application granted granted Critical
Publication of US2238438A publication Critical patent/US2238438A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B11/00—Communication cables or conductors
    • H01B11/18—Coaxial cables; Analogous cables having more than one inner conductor within a common outer conductor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K5/00—Arrangement or mounting of internal-combustion or jet-propulsion units
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60Y—INDEXING SCHEME RELATING TO ASPECTS CROSS-CUTTING VEHICLE TECHNOLOGY
    • B60Y2200/00—Type of vehicle
    • B60Y2200/10—Road Vehicles
    • B60Y2200/12—Motorcycles, Trikes; Quads; Scooters

Definitions

  • This invention relates to new and useful improvements in electrical networks and particularly in networks adapted for use with radio antenna circuits.
  • the main object of the present invention is to provide an impedance matching device for a transmission line interconnecting a high frequency radio transmitter and an antenna operable on more than one-frequency.
  • variable condensers and induction coils or switching devices for selecting a suitable inductance or capacitance are usually employed.
  • the electrical constants of the network may be varied to suit the current frequency employed.
  • Fig. l illustrates a network associated with a transmission line and capable of matching a load impedance to a surge impedance at one frequency, and presenting a substantially infinite impedance at another predetermined frequency;
  • Fig. 2 shows two such 'impedances bridged across the transmission line
  • Fig. 3 shows a concentric conductor arranged to perform the functions of the network shown in Fig. 1;
  • Fig 4 shows a modification of Fig. l
  • Fig. 5 is the concentric conductor equivalent of Fig. 4;
  • Fig. 6 shows another modification of Fig. 1;
  • Fig is the concentric conductor equivalent of Fig. 6; v
  • Fig. 8 is a third modication of the arrangement shown in Fig. 1;
  • Fig, 9 is the concentric conductor equivalent of Fig. 8.
  • Fig. 10 is a variant of Fig. 2;
  • Figs. 11 and 11A are two modifications of Fig. 2 in which two transmitters are connected with the transmission line through two branches;
  • Fig. 12 illustrates the application of Fig. 1l to a system using three transmitters
  • Figs. 13 and '14 illustrate the application of Figs. l and 2 to networks for a system through Awhich currents of three frequencies :are transradio transmitting or receiving station, i. e., at
  • inductances o f the required values can be easily fashioned out of material that is usually in stock and without the necessity of employing other tools or personnel than is available at such stations.
  • Fig. 15 is a modification of Fig. 14 and an extension of Fig. 10 -to a three frequency system;
  • Fig. 16 is a modiiication of Fig. 1;
  • Fig. 17 showsl the application of Fig. 16 to a v three frequency system;
  • Fig. 18 shows a four frequency system in which the networks of Figs. 16 and 17 are used.
  • Figs. 19 and 20 are graphs for facilitating the calculation of values.
  • a network consisting of a two-wire transmission line T, with a loop of wire ACEFDB bridged across it, and a loop of wire bridged across this loop at points CD.
  • the distance from AB to CD is Q, from CD to EF, S, and from CD to GH, P.
  • High frequency alternating current is fed to the transmission line at
  • ZAB be the impedance at AB at some frequency f. This impedance may be expressed in terms of the surge or wave impedance of the line zo, wavelength )t and the lengths of the various parts of the network shown in Fig, 1.
  • section CDEF (looking into the section from above) is izo tan s.
  • the m-Y pedance of section CDGH (looking from- CD to-A wards GH) is izo tan p.
  • the impedance of the two sections in parallel is given by l l l l tan s+tan p) .,tans.tanp jzotan s-i-tan p
  • the network of Fig. 1, will, therefore, at frequency f1 offer any desired value of reactance, and at the same time with P and Q chosen as above present an infinite impedance at frequency fz.
  • the network may, in accordance with the present invention, be used at two different frequencies as an impedance matching means between the transmission line supplying a load having an arbitrary impedance.
  • the network may be precomputed to perform said function without the necessity of varying its constants by switching means or the like when the frequency of the alternating current is changed. It will perform its function when both frequencies are simultaneously impressed on the Itransmission line.
  • a'transmission line to a load in accordance with the present invention two networkslike the one shown in Fig. 1 may be employed.
  • Fig. 2 in which a high frequency radio transmitter is connected with annantenna by means of the transmission line T.
  • Thel two networks are joined to the transmission line at A1131 and at AzBz. ⁇
  • the frequency f1 is impressed on the line then, with both networks removed, waves will be reflected from the antenna if the impedance of the latter is not equal to the surge impedance of the line.
  • a standing wave pattern will result from the interference of waves traveling towards and away from the antenna so Vthat at certain points on the line currents of large and at other asesinas poiitsicurrehtsof small amplitude will be observed'. ⁇ There willbe placesof maximum and minimum currents.
  • l The location of junction A1B1 will be chosen withY reference toa point at which minimum cur,- renty occurs on the line. Let l1 be the distance between lsaid point and the ratio of Vminimumand the line section between the tenna. If the transmission line is short, q1 will be the ratio of minimum-maximum current all along the line with networks I and II in Fig. '2 removed.
  • the ratio of minimum-maximum currents will varyA along the line, and in this case the' ratio should bel determined inthe neighborhood ofthe proposed locationl of the juncture. If the line were cut at the pointwhere maximum current occurs and the impedance looking into the section of the line connected tothe load is measured, the impedance will be found to be a pure resistance ofsome value R1. If theKline were cut at a pointa quarter wave length away (towards the transmitter), i. e., where the current is minimum, the impedance (looking towards the load) will also appear to be a pure resistance ofmsome value R2.; f .v ,Y In accordance with the. law applicable to quarter wavetransformer R1, R2 and zo (the surge impedance of the line) are related in the following manner:
  • Equation 13 enables us to find the two possible vplaces vfor the juncture A1-B1 at Which the matching networkI must be connected to the line;
  • vEquation 14 gives the Value of the impedand the network I is to match the .impedance at frequency f1, the length of the free Vend Siv will be given by Mirco, nl
  • Fig. 3 illustrates a modification of the network illustrated in Fig. 1.
  • a concentric tube type of transmission line is used in which a conductor is centrally located within and insulated from a tube 3
  • ance matching network instead of loops of wire consists of concentric conductors 32, 33 and 34, 35. 32 and 33 are bridged across 36 and 3
  • n and Mmust in the formulae be multiplied by the ratio of the actual velocity to the Velocity of light.
  • Fig.:5 shows a concentric conductor arrangement and bears the same relationship to Fig. 4 as Fig. 3 bears to Fig. ⁇ 1.
  • Fig. 7 is the concentric conductor counterpart of Fig. 6.
  • Fig. 8 shows a matching network consisting of two open-ended pairs of wires AaEs and BsFa, and CsGa and DaHs.
  • the lengths of these openended pairs of wires P8 and Sa and other values are determinedin accordance with the theory applicable toV Fig. ⁇ 4 together with Equation 16.
  • Fig. 9 shows a network built up'of concentric conductors in the manner of Fig. 8.
  • Fig. 10 shows a simplified arrangement which can perform the same function as the arrangement shown in Fig. 2. These two arrangements, howevenare not equivalent. While network I in Fig. 2 has innite impedance and therefore does not disturb the line at wave length A2, network I .in Fig, 10 has a nite impedance at A2 and changes the state of standing waves along the portion of the transmission line between the junction A12B12 and the ltransmitter'. Consequently,
  • network 11 P10 is made and M and M.
  • Networks III11-V11 are bridged across branches 50 and 5
  • V11 is a loop of wire not? in length and bridged across 50 at any convenient point other than Y NIL? or multiple thereof, .from JJ. At wave length M this loop actsas a'short across the Aline'and prevents the currents of this wave length from distur-hing the normal operation of T1.
  • 11111 is a loop of wire in length, also bridged across 5
  • V111 is a loop of wire bridged across 50 between T1 and V11. This network is used to match theY surge impedance of the line coming from fthe transmitter T1 to the impedance of the section of the line disturbedv owing to the presence of V11,
  • Equation 13A the distance between :acurrent maximum and the juncture of V111 measured towards T1 is given by Equation 13A.
  • VSince the impedance. rlooking into a closed loop is mi 7.20amhk kA13 and B13 to 5
  • Fig. 11A shows a modication of Fig. 11 in Awhich the transmission line extensions A50, 5
  • the extension 50' is bridgedrby a horizontal 'l loop at a distance of n from the junction of thev main transmission line.
  • the loop At a distance of from the junction with 50, the loop is bridged by a vertical loop Y in length. Therefore, the junction of 50 and the loop will be effectively short-circuited at wave lengthl M.
  • the free end S1111 is adjusted so that the impedance of the network -is infinite at wavelength M.
  • Fig. 11 may be used also when more than two transmitters are associated with the line. .An arrangement for three transmitters is shown in Fig. 12. l
  • the networks 112, 1112 and 11112 bridged across the line T12 function in vthe same manner as'the networks of Figs. 13 and 14. Three transmitters TM, TM and TM arer connected with T14 through branches
  • 04 short circuit the line
  • the positioning values and function of these loops are the same as those discussed in connection with Fig. 11.
  • the network can ,be constructed so as to match impedance where currents of more thanltwo fre- ,i quencies are transmitted.
  • Fig. 13 illustrates such network by means of Vwhich lines carrying three frequencies can be accommodated.
  • a loop of wire 60 is bridged across the transmission line T13 atV AnBia. ⁇
  • the distance from where n can be either zero or any'integral whole number. The choice of n depends upon the valueof M in comparison with M. This section must he long enough to permit the of a loop at 63, 64 at a distance connection frOm A13B13.
  • Thev free" end S13 fof loop-60 is Vmade of such length that the impedance looking into the loop at A13B13 with loop lll removed is innite atV wave length k2. At M it is innite owing to the length of loops 8i! and 66.
  • Loop 'lil bridged across 56 at 63, Gli is in length from 63, 64 to 1l, 12.
  • Loop l5 bridged across '10,at 1I, 12 is from B13 and A13 as mentioned above) because the impedance at 63, 64 looking towards 6l, 62 had been made zero for M. by the adjustment of S13. On this account, the addition of network 1i), 'I5 does not disturb the functioning. of 60, 80.
  • the impedance at A13B13 is therefore innite at M.
  • junction points A13B13 may be precomputed substantially along the lines discussed in connection with Figs; 1 and 2.
  • Fig. le illustrates three networks likethe one shown in Fig. 13 connected with a transmission line T14 through which a transmitter is connectedrwith an antenna.
  • the network 114 is adjusted Yto match the impedance of the line at wave length M and have lnnite impedance at 12 and M. Similarly, H11 matches at M and 11114 at A3 and present innite impedance at the other two frequencies. All considerations applicable to Fig. 2 and. also Fig, 13 apply here also. Y Y Y
  • Fig. 15 isl a modification of Fig. Maand the network disclosed therein performs the same function as the one disclosed in the former.
  • the transmission line T15 may be used for three ldifferent frequencies.
  • the network 11115 is like the network shown in Figs. 13 and. 14'.
  • the sections or networks may also be constructed in the manner illustrated inV Figs. 16-18.
  • the method of generating sections explained in connection with these figures is particularly' applicable to the use of triple, quadruple, etc., sections, as well as to double sections.
  • the impedance element shown in Fig. 16 is so proportioned that looking into itA at 283, it is of infinite impedance at M aswell as at M. This is accomplished by making loop portion 20D-20
  • E61-2M is the loop zee-zes is at i2, effectively short-cir cuited at 291.
  • Section 20a-,201 being aassyis From this it fouows that the length sis of loop 2o 1 203 is equal to 1f the ioop of Fig. 1e is made' longer and the cross connection moved from 203 to 205 then, as shown in Fig. 1'7, by connecting a 2 loop across points 293, the network will not only appear at 200 as an infinite impedance when current of M and x2. wave lengths flow, but the impedance at B may be made to have any prescribed value at wavelength A3 and thus may be employed to match impedances at this wavelength.
  • the network may be made to have infinite impedance at M, A2 and )o and match the load to the surge impedance at M.
  • Fig. 18 illustrates the'use of fixed networks 11s-IVN; constructed as explained in connection with Figs. 16 and 17 and permanently bridged across the transmission line Tia to match the antenna load impedance to the surge impedance when currents of M, Az, as, M wavelengths are impressed upon the line.
  • each impedance together with the line conductors between it and the antenna are used as the sole impedance matching means.
  • No adjustable or specially built and protected devices need be provided and the construction and installation may be effected by the usual operating personnel of a radio station. Charts or graphs may be prepared for ready reference in the construction of net-V works herein described.
  • Fig. 19 shows, for example, a curve useful in selecting proper values for a network like the one illustrated in Fig. 16.
  • the numbers in the first vertical column represent values of S in degrees for the end section 20
  • the abscissa is calibrated for calculate be p 180 M degrees, nd corresponding S from Fig. 19 in degrecs and make loop Z i-2E33 of length with ' one shown in Fig. 4.
  • the auxiliary angle u as well as values of 19:0 may be readily obtained from by means of. Fig. 20.
  • the straight line oP is provided for this purpose.
  • the actual calculation of p from i consists of looking up iny the right colurn of Fig. 20, marked v Mk2): T
  • a transmission line two sources of alternating current of different frequencies, connections between said sources and one end of the line, a load connected to the other end of the line, fixed impedance devices permanently bridged across various sections of said line, each substantially matching the load impedance to the surge when current of a different frequency is impressed on the line, and presenting ⁇ substantially infinite .impedance at other frequencies, impedance devices permanently bridged across the first connection between the iirst source and the line effectively short-circuiting the connection at the frequency of the second source, compensating for the short-circuiting action of impedance devices bridged across the second connection, and preventing the reflection of waves into the first source, and impedance devices permanently bridged .across the connection between the second source and the line effectively shortcircuiting the other connection at the frequency of the first source, compensating for the presence Y of the impedance devices across the first connection, and preventing the reection of waves into the second source.
  • a transmission line two sources of high frequency alternating current of different frequencies, connections between said sources and one end of the line, a load connected to the other end of the line, a fixed impedance device permanently bridged across one section of said line substantially matching the load impedance to the surge impedance when current of one frequency is impressed on the line, and presenting substantially infinite impedance at the other frequency, a second fixed impedance device lpermanently bridged across another section of said line substantially matching the load impedance to the ,surge impedance when current of the other frequency is impressed on the line and presenting substantially innite'impedance at said one frequency, a third fixed impedance device permanently bridged across the connection between the rst source and the line effectively short-circuiting the connection at the frequency of the second source, compensating for the short-circuiting action of the fourth impedance device and preventing the reiiection of waves into the rst source, and a fourth fixed impedance device permanently bridged across the connection between the
  • a first transmitter of one frequency a second transmitter of another frequency, a main transmission line, an antenna connected to said main line, a two-conductor line connecting each transmitter to said transmission line, vand an impedance circuit in shunt across each of said two-conductor lines, each of said impedance circuits being constructed and arranged to provide at its point of connection to its twoconductor line, a high impedance to the flow of energy in its associated two-conductor line of the frequency of its associated transmitter and a low impedance to the flow of energy in its associated line of the frequency of the other transmitter, the shunt impedance circuit across one two-conductor line being located from the junction of said one two-conductor line with the main transmission line ardistance equal to an odd multiple of onequarter of the wave generated by the transmitter connected to the other two-wire line, said other shunt impedance circuit being located from the junction of said other two-conductor line with the main transmission line a distance equal to an odd multiple of one-quarter of

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  • Variable-Direction Aerials And Aerial Arrays (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)
  • Control Of Conveyors (AREA)
US12451A 1935-03-22 1935-03-22 Electrical network Expired - Lifetime US2238438A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US12451A US2238438A (en) 1935-03-22 1935-03-22 Electrical network
NL76769A NL43581C (OSRAM) 1935-03-22 1936-02-28
GB7648/36A GB457911A (en) 1935-03-22 1936-03-13 Electrical impedance networks
FR806803D FR806803A (fr) 1935-03-22 1936-03-20 Perfectionnements aux réseaux de transmission d'ondes électriques

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US12451A US2238438A (en) 1935-03-22 1935-03-22 Electrical network

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US2238438A true US2238438A (en) 1941-04-15

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US12451A Expired - Lifetime US2238438A (en) 1935-03-22 1935-03-22 Electrical network

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US (1) US2238438A (OSRAM)
FR (1) FR806803A (OSRAM)
GB (1) GB457911A (OSRAM)
NL (1) NL43581C (OSRAM)

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2473448A (en) * 1945-04-18 1949-06-14 Foster F Rieke Oscillator
US2485029A (en) * 1944-08-30 1949-10-18 Philco Corp Frequency stabilizer for oscillators
US2485031A (en) * 1944-08-30 1949-10-18 Philco Corp High-frequency transmission system
US2510022A (en) * 1944-03-15 1950-05-30 Rca Corp Band-pass signal transmission system
US2539680A (en) * 1945-11-26 1951-01-30 Rca Corp Ultra high frequency antenna
US2543973A (en) * 1946-06-27 1951-03-06 United Air Lines Inc Plural-frequency coupling unit
US2546147A (en) * 1945-08-29 1951-03-27 Lawrence W Boothby Frequency distinguishing device
US2548672A (en) * 1947-12-05 1951-04-10 Bell Telephone Labor Inc Multiresonant wave-guide structure
US2558749A (en) * 1941-05-17 1951-07-03 Sperry Corp High-frequency impedance transformer
US2570579A (en) * 1946-12-06 1951-10-09 Rca Corp Transmission line system
US2575471A (en) * 1950-04-13 1951-11-20 Philco Corp Vehicular antenna system
US2591982A (en) * 1941-07-30 1952-04-08 Hartford Nat Bank & Trust Co Superheterodyne receiver for very short waves
US2593474A (en) * 1944-10-03 1952-04-22 Us Sec War Antenna matching section
US2650304A (en) * 1949-09-10 1953-08-25 Motorola Inc Television antenna
US2650303A (en) * 1949-07-01 1953-08-25 Motorola Inc High-frequency loop antenna system
US2705307A (en) * 1946-02-01 1955-03-29 Nyswander R Edson Double slug tuner
US2708238A (en) * 1954-04-09 1955-05-10 Silverman Emanuel Television wave trap and the like
US2725537A (en) * 1941-01-28 1955-11-29 Wilmer L Barrow Adjustable ultra-high-frequency impedance device
US2794174A (en) * 1952-05-08 1957-05-28 Itt Microwave transmission systems and impedance matching devices therefor
US2809355A (en) * 1953-10-09 1957-10-08 Continental Electronics Mfg Dissipative load
US2938209A (en) * 1956-12-10 1960-05-24 Brueckmann Helmut Antenna curtain array with coupling network
US3068428A (en) * 1955-06-16 1962-12-11 Andrew Alford Diplexing unit
US3922683A (en) * 1974-06-24 1975-11-25 Hazeltine Corp Three frequency band antenna
US4725792A (en) * 1986-03-28 1988-02-16 Rca Corporation Wideband balun realized by equal-power divider and short circuit stubs

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE969386C (de) * 1941-01-01 1958-05-29 Pintsch Bamag Ag Frequenzabhaengiger Blindwiderstand fuer ultrakurze Wellen
BE509377A (OSRAM) * 1951-02-26
DE1027341B (de) * 1952-01-17 1958-04-03 Rohde & Schwarz Oberwellenfilter fuer Sender sehr hoher Frequenzen
DE1260648B (de) * 1957-05-31 1968-02-08 Siemens Ag Durchstimmbare Weichenfilteranordnung fuer sehr kurze elektromagnetische Wellen

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2725537A (en) * 1941-01-28 1955-11-29 Wilmer L Barrow Adjustable ultra-high-frequency impedance device
US2558749A (en) * 1941-05-17 1951-07-03 Sperry Corp High-frequency impedance transformer
US2591982A (en) * 1941-07-30 1952-04-08 Hartford Nat Bank & Trust Co Superheterodyne receiver for very short waves
US2510022A (en) * 1944-03-15 1950-05-30 Rca Corp Band-pass signal transmission system
US2485029A (en) * 1944-08-30 1949-10-18 Philco Corp Frequency stabilizer for oscillators
US2485031A (en) * 1944-08-30 1949-10-18 Philco Corp High-frequency transmission system
US2593474A (en) * 1944-10-03 1952-04-22 Us Sec War Antenna matching section
US2473448A (en) * 1945-04-18 1949-06-14 Foster F Rieke Oscillator
US2546147A (en) * 1945-08-29 1951-03-27 Lawrence W Boothby Frequency distinguishing device
US2539680A (en) * 1945-11-26 1951-01-30 Rca Corp Ultra high frequency antenna
US2705307A (en) * 1946-02-01 1955-03-29 Nyswander R Edson Double slug tuner
US2543973A (en) * 1946-06-27 1951-03-06 United Air Lines Inc Plural-frequency coupling unit
US2570579A (en) * 1946-12-06 1951-10-09 Rca Corp Transmission line system
US2548672A (en) * 1947-12-05 1951-04-10 Bell Telephone Labor Inc Multiresonant wave-guide structure
US2650303A (en) * 1949-07-01 1953-08-25 Motorola Inc High-frequency loop antenna system
US2650304A (en) * 1949-09-10 1953-08-25 Motorola Inc Television antenna
US2575471A (en) * 1950-04-13 1951-11-20 Philco Corp Vehicular antenna system
US2794174A (en) * 1952-05-08 1957-05-28 Itt Microwave transmission systems and impedance matching devices therefor
US2809355A (en) * 1953-10-09 1957-10-08 Continental Electronics Mfg Dissipative load
US2708238A (en) * 1954-04-09 1955-05-10 Silverman Emanuel Television wave trap and the like
US3068428A (en) * 1955-06-16 1962-12-11 Andrew Alford Diplexing unit
US2938209A (en) * 1956-12-10 1960-05-24 Brueckmann Helmut Antenna curtain array with coupling network
US3922683A (en) * 1974-06-24 1975-11-25 Hazeltine Corp Three frequency band antenna
US4725792A (en) * 1986-03-28 1988-02-16 Rca Corporation Wideband balun realized by equal-power divider and short circuit stubs

Also Published As

Publication number Publication date
GB457911A (en) 1936-12-08
NL43581C (OSRAM) 1938-07-15
FR806803A (fr) 1936-12-26

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