US2268844A - Steerable antenna system - Google Patents

Description

jan 6, 1942 F. A. POLKINGHORN 226,44;

' STEERABLE ANTENNA SYSTEM Filed Feb. 17, 1940 2 Sheets-Sheet l ADJUSTABLE DE L A y #24ML ATOR DE VICE PHASE SPL/7' TE l? PHASE JPL/T'TEI? /M/ENTOR E A. POL/f/A/GHORA/ ATTnDA/EV Jam., 6, 1942. F. A. POLKINGHORN 2,2%,344

S TEERABLE ANTENNA S YS TEM comme@ PHASE smi /A/L/EA/Ton FA. POL/(INGHOR/V Patented Jan. 6, 1942 seras ,caen

T @ENCE STEERABLE ANTENNA SYSTEM Application February 17, 1940, Serial No. 319,394

7 Claims.

This invention relates to phase control circuits and more particularly to multichannel phase control circuits especially adapted for use in systems having a plurality of input circuits and one or more output circuits.

As disclosed in Patent 2,041,600, H. T. Friis, May 19, 1936, highly eicient radio reception or transmission may be secured utilizing an array comprising a plurality of antenna units connected through adjustable individual phase shifters to the receiver. In this system or method the phases o'f the antenna currents are adjusted for the purpose of aligning the maximum directive lobe of the array with the optimum direction of vtransmission or'reception, and it has been suggested that a phase shifter of the type illustrated by Fig. 1 of Patent 2,147,728, W. T. Wintringham, February 21, 1939, and comprising a variable condenser and a phase splitting network included between each antenna unit and associated condenser, be employed in order to secure an accurate phase and amplitude control and a constant uniform loss in the phase shifter with adjustment of phase. Thus, in a large practical receiving system comprising sixteen antenna units and sixteen phase shifting variable condensers, sixteen phase splitting networks would be utilized. 'If reception is desired over several paths or diversity branches a group of sixteen condensers is required for each diversity branch and several conde'nsers, one for each diversity branch, may be connected to the output terminals of the phase splitting network associated with each unit. It now appears desirable to simplify greatly the phase control arrangement described above and particularly to achieve a substantial reduction in cost, both in initial and maintenance expense, for multichannel control circuits used in a multiunit steerable array, hereinafter referred' to simply as MUSA, comprising a large number of antenna units. More particularly it appears desirable to employ a minimum number of networks in receiving systems comprising a given plurality of antenna units or input circuits and a different plurality of diversity branches cr output circuits.

It is one object of this invention to control the phase relation of several currents in a simple and economical manner.

It is another object of this invention to utilize a minimum amount of equipment for adjusting or controlling, without change of amplitude, the phase relation of several currents.

It is still another object of this invention to steer or adjust for optimum operation one or more directive characteristics of a multiunit antennaarray without attenuating upon change of adjustment the antenna currents, and utilizing a minimum amountof equipment.

It is a further object of this invention to 'control, in a transmission system included between a plurality of input circuits or energy sources and a plurality of outputnircuits or load devices and comprising a plurality of distinct transmission paths, the phase relation of the currents in an eiicient and inexpensive manner.

According to this invention, in a system having a plurality of input circuits and one or more output circuits vand employing phase control circuits of the type described above, a minimum number of networks may be utilized when the number of input 'circuits exceeds the number of output circuits, by including a phase combining network between each output circuit and a separate set of condensers connected to the input circuits; and, when the number of output circuits is greater than the number of input circuits, by connecting a phase splitting network between each input circuit anda separate set of condensers connected to the output circuits. When the number of input circuits and the number of output circuits are equal either arrangement may be utilized. Thus, in a four-angle diversity MUSA system comprising sixteen antenna units and sixty-four control condensers, four control networks may be employed instead of sixteen as previously suggested.

The invention will be more fully understood from a perusal of the following specification taken in conjunction with the drawings in which like reference characters denote elements of similar function and in which:

Fig, 1 illustrates a-two-angle diversity, threeunit MUSA system arranged in accordance with prior art suggestions;

Fig. 2 illustrates a two-diversity, three-unit MUSA system constructed in accordance with the invention; and

Fig. 3 illustrates an embodiment of the invention as incorporated in a large MUSA system.

Referring to Fig. 1, reference numerals I designate antenna-counterpoise units which may each have a directive characteristic or a nondirective characteristic and which together constitute an array for receiving an incoming signal over the two diversity paths or branches A and B, the units being spaced along the array axis 2. Each unit is coupled through input transformer 3 or 4 or 5, to the input terminals 6 and `l of a phase splitting network having four `2| through the receiver 39.

cuits 3, 4` and 5 are connected to the two outputy eachr antenna and the associated transformer 3, Iy Reference numerals 24 designate phasecontrolvariable condensers for diversity branch A, eachof these condensers having a rotor v25 and four stator plates 26, 21, 28 and 29 which are connected, respectively, to network terminals,

I0, and rI2 through conductors 30. VA similar set of Vthree condensers 3|, one foreach input circuit, is provided for. diversity branch B, the

32 to thestators of the condenser 24 and to the sion channels as the system of Fig. 1,` it will be i seen that in accordance with the invention the connections for each variable condenser are reversed with respect to those in the system of Fig. 1, and that instead of phase splitting networks, one for each input circuit, phase combining networks, one for each output circuit, are utilized.

The phase combining networks 42 are the samein construction as the phase splittingnetwork 8 of Fig. 1. Thus considering each diversity branch or output circuit and the three condensers therefor, the input circuits 3, 4 and 5 are each con-r nected to the rotors 25 and the stators are constators ofy each being connected by conductors four terminals-of the network 8 associated with the samefinput circuit or antenna. of condensers 24 and 3| and the associated phase splitting network constitutes a distinct phase control circuit.

The rotors 25 of condenser 24 for diversity branch A are connected` together by conductor y33 and through adjustable `delay device 34 to the input terminal or circuit 35 vby means of con-- ductorsSBf; and the. rotors 25 of condensers 3| together and directly connected to output terminal 3.1. `Therctors for the condensers in each Thus, each rnected through a single combining network to the output circuit; whereas in Fig. `l, the input circuitsare connected through separate splitting ,Y networks tothe stators and the rotors are connected to the output circuit. It maybe noted herethat each condenser and associated network, as used in the systems of Figs. 1 `and 2, constitute a passive network, and, as is known, the

`output and input .terminals of such a network` `may be-interchanged. More particularly, referring to Fig. `2, the secondary windings of transformers 3, 4 and 5 are each connected by a conductor-40 to the rotors 25 of a condenser and a condenser 3 I; and the stators 2B and 21, 28 and f 29` of. rthe three condensers in each diversity groupare connected by the conductors, re-

f for diversity branch B are similarly connected spectivelyto the terminals 9, I0, and |2fof a network` 42, each network comprising condensers I3 and v|4condensers I5 and I6, coils I1 and- III diversity branch arer preferably unicontrolled through graded gears, in accordance with the disclosure in ther above-mentioned Friis patent,

as indicated schematically by line 38. The outf put terminals 35 and 31 are connected to ground Hence, input circircuits 35 and 31 through a six-channel transmission system each including a phase control condenser. It should be noted that the phase control networks are directly associated with the input circuits, and that the number of networks is equal to the number of input circuits and greater than the number of output circuits.

In operation, the components of a desired wave as received Iover the two paths A and B on the several antennas are conveyed through transformers 3, 4 and 5 to the input terminals 6 and I of each of the three networks 8. As explained in the Friis patent mentioned above, the components intercepted by adjacent units differ in phase by an amount related to the wave arrival angle A or B. Since the network 8 is in effect a quadrature phase shifter, each network functions to impress quadrature potentials `on the four stator plates of each condenser 24 and 3| associated therewith, whereby the potential impressed on the condenser rotor 25 mayvhave any phase and is determined solely by the rotor position. As ordinarily used therotors 25 of condensers 24 are simultaneously adjusted so as to secure thereon in-phase potentials for waves having the incoming direction A; and the rotors 25 of condenser 3| are similarly adjusted to secure in-phase potentials for components following direction B. Delay device 34 is then adjusted for the purpose of rendering the output potentials or the currents for the two branches in phase agreement on terminals 35 and 37.

Referring now to Fig. 2 which illustrates a multi-channel system having the same number of input circuits, output circuits and transmisand a resistance I9. The output terminals 43 and v|4of eachv network 42 are connected to the receiver 39 by line 45, a delay device'34 being included in branch A between the phase combiningnetwork 42 and the receiver 39. Thus, as in the system` of Fig. 1 the transmission system comprises six channels and each condenser and associated network constitute a phase control circuit. f

In operation, out-of-phase wave components received over each of paths A and B by the antenna units are impressed on the rotors 25 of the condensers 24 and on the rotors of condensers 3|. The rotors of condensers 24 and the rotors of condensers 3| are adjusted so that in-phase potentials are secured, respectively, for directions A and B on the output terminals of the respective network 42. More specifically, the rotors 25 of condensers 24 are adjusted so that the out-ofphase potentials impressed thereon by the antenna units produce in-phase potentials on the output terminals 43 and 44 of the network for waves having the direction A and the rotors 24 of condensers 3| are adjusted to secure in-phase output potentials for a wave having direction B. As in the circuit of Fig. 1, the delay circuit 34 is then adjusted so that the energies received over branches A and B are rendered in phase agreement before being supplied to the receiver 39. In a sense, in the system of Fig. 1, each rotor selects from the phase splitter terminals a properly phased potential whereas, in the system of Fig.` 2, each rotor impresses on the phase combiner terminals properly phased potentials.

It is therefore apparent that, in accordance with the invention, a reduction in the number of networks required is realized, the number being equal to either the number of input circuits or the number of output circuits, whichever is smaller. Comparing the prior art system of Fig. 1 with applicants system, Fig. 2, each system having three input and two output circuits, three networks are used in the prior art arrangement whereas only two networks are employed in applicants system. Ordinarily in steerable antenna, systems of the type referred to above the number of input circuits exceeds the number of output circuits, and, in accordance with the invention, a considerable economical saving is effected.

Fig. 3 illustrates a large practical MUSA system especially suited for transoceanic communication and designed for four-angle diversity reception. The system comprises sixteen highly unidirectional rhombic antennas 5| spaced along the array axis 52 and connected each through a transformer 53 to the rotors 25 of Ifour condensers 54, 55, 56 and 5l, each of the four condensers being included in a different diversity branch. Thus, sixteen -condensers 54 are provided for branch A, sixteen condensers 55 for branch B, sixteen condensers 56 for branch C and sixteen condnsers 51 for branch D. As in Fig. 2, the stators 26, 21, 28 and 29 for the condensers for each branch are connected by conductors 4| in parallel and to the four terminals of a phase combining network 42 one of which is provided `for each branch. The output terminals 43 and 44 of all networks, except the network 2 for branch D, are connected by lines 45 through a separate delay device 34 to the input terminals of receiver 39. The network l2 for branch D is directly connected to the receiver 39. If desired, one of the sets of sixteen condensers and associated network may be used for monitoring purposes instead of for service reception, as disclosed in Patent 2,173,858 of N. J. Pierce and F. A. Polkinghorn, granted September 26, 1939.

The directive operation of the MUSA system of Fig. 3 is fully explained in the Friis patent. Moreover, in vie-w of the discussion given above in connection with Fig. 2, the operation of the phase control multichannel system of Fig. 3 is believed to be apparent. It should be noted that while sixteen input circuits or antenna units, four output circuits or branches and sixty-four variable condensers are utilized only four control networks are employed, whereas if the arrangement illustrated by Fig. 1 were utilized, sixteen networks, each relatively expensive both in structural cost and installation cost, would be required. It may be added that, as described in the abovementioned patent of Pierce-Polkinghorn, the receiver 39 in network 52 may be located at the center of the array and the two halves of the array may, if desired, be separately or jointly used. In this case each subarray of eight antenna units would require four phase combining networks, and for the whole system, a saving of eight networks would be realized as compared to the prior art arrangement. It should be added also that the invention is equally suited for use in transmitting and receiving systems and may be used i'n MUSA systems arranged for directive steering in a plurality of planes.

Although the invention has been described in connection with certain embodiments, it should be understood that it is not to be limited to the embodiments described since other apparatus may be successfully employed without exceeding the scope of the invention. Thus, the number of stator plates in each variable phase shifting condenser may be other than four, as for example, eight; and again, instead of a variable condenser a variable inductance may be satisfactorily employed in each phase control circuit.

What is claimed is:

1. In an electrical system, a plurality of energy sources each connected through a separate transmission channel to a load circuit and means for adjusting with uniform loss the phase relation of the currents in said channels, said means comprising a variable phase splitter included in each channel for deriving from the channel current two sets of opposite phase components, and a common phase combiner included between all of said phase splitters and said load circuit and, comprising a phase shifter for changing the phase relation between the two sets of components in each channel.

2. In a radio system, an antenna array comprising a plurality of antenna units, a translation device, a set of adjustable phase changers each having a constant loss with adjustment, each changer comprising an individual variable condenser having a rotor connected to a diierent antenna unit and four stator plates, a common@ quadrature phase shifter connected to the translation device and having four terminals each connected to a different set of corresponding stator plates.

3. In an angle diversity radio receiving system, a multiunit steerable antenna array, a receiver and a set of adjustable phase changers for each diversity branch, each changer having uniform loss with adjustment and each set comprising a separate variable condenser connected to each unit and a common quadrature phase shifter included between the receiver and said Condensers.

4. In a radio receiving system, a multiunit antenna array, a receiver and means for obtaining a plurality of steerable and independent space factor directive characteristics included between said array and said receiver, said means comprising a plurality of sets of variable reactances, one set for each characteristic, each reactance in each set being connected to a different antenna unit, and a plurality of phase combining networks, a different one for each characteristic, each network being connected between the receiver and all the reactances of the associated set of condensers.

5. In a radio system, a steerable antenna array comprising a plurality of antenna units connected through separate transmission channels to a receiver, and means for adjusting without change of attenuation the phase relation of the antenna currents included in said channels, said means comprising a plurality of variable condensers, each having a rotor and a plurality of stator plates, said units being connected to separate rotors and the corresponding stator plates being connected together, and a phase combining network having four terminals each connected to a different set of corresponding stator plates, and said receiver being coupled to said network.

6. A method of securing, in a radio system comprising a multiunit antenna array, a plurality of steerable space factor characteristics for receiving energy over diverse paths, utilizing a separate variable reactance between each unit and the receiver for each diversity path, which comprises the step of including a network between each unit and the reactances connected thereto when the number of paths exceeds the number of units, including a network between the reactances for one path and the receiver when the number of units is greater than the number of paths, and including the network between each unit and the associated reactances or between the reactances for one path and the receiver when the units and paths are equal in number.

7. A method of receiving radio energy over a first given plurality of paths, utilizing an array connected theretowhen the rst given plurality is larger than the second given plurality, and including a network between the receiver and the corresponding condensers utilized for the same path when the second given plurality exceeds the rst given plurality, whereby each condenser and associated network constitute an independent phase control circuit and a minimum of networks is utilized.

FRANK A, POLKINGHORN.

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