US2231079A - Phasing network - Google Patents

Description

Feb. 11, 1941. e. LONGO PHASING NETWORK Filed June 9, 1939 Zinnentor @usiawe Longo Patented Feb. 11, 1941 UNITED STATES PATENT OFFICE Application .lune 9, 1939, Serial No. 278,243

In France October 11 1938 8 Claims. (01. 178-44) The invention relates to a system or method for the radiation of -modulated radio-electric waves and apparatus for carrying out the functions of the system.

An essential object of the invention is to render more economical the functioning of the transmitter; for this reason, it is particularly applicable to radio broadcasting stations.

It is known that the radiation of modulated waves is particularly ineificient, above all if the percentage of modulation should be able to at tain 100 percent, because of the great variations in the instantaneous power radiated as compared to the average power. This new system eliminates these variations; the power radiated is at all times equal to the average power.

The invention will be described by referring to the accompanying drawing in which Figure 1 is a diagrammatic representation of an antenna array; Figure 2 is a schematic diagram of one embodiment of the invention; Figure 3 is a diagram of the phase splitting network used in the invention; and Figure 4 is a schematic diagram of another embodiment of the invention. Similar reference numerals have been used to indicate similar elements.

In the system of the invention, the radiation is effected through five antennas, preferably vertical, one of which is a central antenna, corresponding to the usual antenna, and four are peripheral antenna-s, identical to each other, arranged at the corners of a square, the center of which is occupied by the first antenn'a. In Fig. 1, the circle A0 represents the outline of the central antenna on the ground, the circles A1, A2, A3, A4 the outlines of the peripheral antennas. The distance I of each of the peripheral antennas from the central antenna is preferably small compared to the wave length A ofthe transmitter--for example, of the order of It is desirable, at least for the application of the system to radio broadcasting, that the field given by the series of four peripheral antennas present a distribution in height (the field diagram in the vertical plane) practically equal to the distribution in height of the field given by the central antenna. If this central antenna is constituted, as in many modern stations, by a mast antenna of great height, the said resultant may be easily obtained by giving to the peripheral antennas a suitable height, lower than that of the mast; these peripheral antennas may be conveniently supported by the mast itself.

The central antenna A0 (Fig. 2) is intended to emit the single carrier wave; it should thus be energized by a current of high frequency and constant amplitude. As, moreover, the field caused by the series of the four peripheral antennas has no action on the current in the central antenna, the excitation of this antenna demands a power at all times constant, and con- 10 sequently the antenna may be excited by a thermionic tube (or a series of tubes) So operating as class C amplifiers.

The two pairs of peripheral antennas aligned with the central antenna, that is to say, the antennas A1 and A3 of the one part, and the antennas A2 and A4 of the other part, are excited separately, the first pair by a tube (or a series of tubes) S, and the other pair by a tube (or series of tubes) S, the tubes being identical to each other and identically coupled to the respective antennas. The two antennas coupled to the same tube are excited in a fashion entirely symmetrical, that is to say, in such manner that the current in one of the antennas is at the same time equal and opposite to the current in the other. The tubes S and S" preferably operate in class B and in linear fashion; the voltage for the excitation of their control grids may be obtained in the manner described below. 30

Let 6 be the voltage of the acoustic current which should modulate the wave emitted by the station, at any time whatsoever; this voltage may be represented by a sum of sinusoidal terms, and therefore, with the customary notations,

By means of the arrangement above described, or by any other process, the voltage e must be transformed into the two voltages e and e" having the following expression:

8'=KE en sin (9n t-Bn);

e":KZ en cos (on t-Bn) Where K is any constant. Let

be the effective value of e, and E0 the limit value that E should never go beyond during the operai tion of the transmitter.

Let 0; be the pulsation of high frequency of the transmitter, through the voltage e of the one part and the voltage 6 of the other part; the oscillation of pulsation w is modulated sepa- 55 tube S".

rately with the carrier suppressed in such man ner as to obtain two voltages.

Kie sin wt The effective average values of these currents are equal to each other and proportional to E; let

Kie" sin wt E be this effective average common value, I1 being then always invariable during the operation of the station.

If Iobe the effective invariable value of the current in the central antenna, this current should be in the form,

that is to say, in quadrature with the current in the peripheral antennas.

The wave emitted by the series of five antennas is modulated according to the voltage of the acoustic current; in order that the relation between the rate of modulation and the effective Voltage E of the acoustic current may have the proper value, the value of the relation may be conveniently regulated, once for all times, as

Under these conditions, the wave emitted by p I the transmitter in any vertical plane which passes 45 through the central antenna does not diifer in any way from the wave which would be emitted by a'station of the ordinary type; but the instantaneous value of the modulation of the emitted wave, contrary to that which arrives for ordinary stations, varies from one vertical plane to the other according to the law that the instantaneous power of the radiation is always equal to the average power.

The system permits of employing a number of peripheral antennas different from four, always symmetrically arranged with regard to the central antenna, the currents in the antennas being modulated according to the polyphase symmetrical systems, in a manner similar to the preceding one and easy to determine. In any case, the corresponding transformation of the acoustic current of modulation may be obtained by the arrangement described above.

In the arrangement of antennas just described, the carrier wave of the radiation is produced by the central antenna and the waves of the two' side bands by the peripheral antennas. Other arrangements may also be realized; for example,

the same postion as before, and may be fed in the same manner with regard to their particular current; but the tube Sc (through connections that will be perceived immediately), in place of feeding the central antenna, feeds the series of peripheral antennas in parallel; thus the current of constant amplitude which produces the carrier wave, uniformly distributed in the peripheral antennas, is added in each antenna to the particular current thereof.

The device of this system may find applica tions among radio beacons and analogous arrangements. If the current of modulation is constituted by a single sinusoidal term of frequency f, the amplitude of the wave emitted presents a maximum in a vertical plane which turns around the central antenna at an angular constant speed 21rf.

It will be seen that what is essential in the system is the form and spatial arrangement defined above (or equivalent form and arrangement) of the antenna currents; naturally, any manner of furnishing the currents to the antennas may be employed. What follows is the description of the arrangement for efiecting the transformation of the modulation current which, as has been seen above, is necessary to the functioning of the system.

The fundamental element of the arrangement is represented by a double row of elementary impedances, as, for example, the two rows F1 and P: (Fig. 3); each elementary impedance is formed by a resistor 1', an inductor U1 and a capacitor C'1 in series; a certain number or" these elementary impedances 1", U1, Ci, etc.(which may also be called simple circuits) arranged in parallel, compose one row P'i; the two ranges Pi, P'z are arranged in series between two input terminals B1 and B2. Between the two rows P1, Pz, a resistor r is inserted; a terminal B is connected to the midpoint of the resistor 1" which is an output terminal of the double row. Two or more of these double rows P'i, P'z, P"1, P": suitably joined, constitute the essential part of the arrangement.

Each double row of simple circuits should present the following characteristics Let N be the total number of simple circuits which compose the double range. The resistors r of each of these circuits have the same value in all the circuits; on the other hand, the value of the inductors Li, etc., and that of the capacitors Ci, etc., vary from one circuit to another in the manner explained below.

Going from the circuit, the inductor of which has the highest value, and successively in the order of decreasing inductances, each circuit is distinguished by an order number The circuits having the odd order munbers compose the range P'1; the others, the range Pz.

If L9 be the value of the inductor and C9 that of the capacitor of the generic circuit the order number of which is 9; a being a positive number conveniently chosen, it is necessary that, between the values L9 and C9 of the one part, and, of the other part, the values L10 and C10 of the inductor and capacitor of the successive circuit, the following fundamental relation be satisfied, whatever may be 9 from 1 to N-l:

1 =fi= L10 C10 n The result is that the relation a C0 is an independent constant of 9.

Let fm be the lowest frequency of the band of frequencies that the arrangement is intended to cover, and fur the highest; this band is not necessarily a band of acoustic frequencies, but may be of any kind whatever.

Let

fm E On the contrary, the geometric averages /f1 fn and. \/fm fM should be, in a sense otherwise very large, of the same order of greatness.

The manner of realizing the arrangement may be deducted from the following generic example: Let two double ranges of simple circuits P1 and P2 of the one part, and. P"1 and P"2 of the other part (Fig. 3) each be constituted in the manner just described; the values of N, a, R, r will be the same for the two double ranges. Let Us and C's be the values of the inductor and the capacitor of the circuit 9 of the first double range, L"9 and C"9 the corresponding values for the circuit 9 of the other double range; s being any number lower in absolute value than unity, the second fundamental relation following should be satisfied, whatever 9 from Z to n may be:

LI9 !g rams- The two double ranges are disposed in parallel between the terminals B1 and B2. To these terminals is applied any source capable of developing between the terminals themselves the voltage which actuates the arrangement; the action of the source should be symmetrical, in such manner that the voltage at one of the terminals (with regard to ground) will be at all times equal and opposite to the voltage at the other terminal. For

- example, as in the schematic diagram (see Fig. 3),

there may be connected to the said terminals the secondary T2 of a transformer, the primary T1 of which is controlled in the ordinary suitable c=Ea sin (21rf,,t-,,) If the values of all the elements in operation, are suitable, there are developed at the output terminals B and B", respectively, the voltages (K being a constant) K26 sin (ZW'fnt-Bn) and K2611. sin (27rfnt-Bn+a) where the phase difference a, the same for all the terms, has the value a=81r.

From this example, which brings to light the essential propriety of the double ranges of simple circuits, one may easily deduce the manner of realizing the arrangement in all concrete cases, according to the results to be attained.

In particular, the arrangement applicable to a radiation circuit should, as has been seen, transform the voltage e into the two Voltages e and e" already defined, for all the terms the phase diiference of which has the value It is evident that this arrangement may be the same as has just been described and the diagram of which is represented in Fig. 3; it is sufiicient, naturally, to give to s the value s=1/2.

For this value of s the impedance presented by the two double ranges in parallel is quite independent of the frequency; consequently, the internal resistance of the source may be, from this point of view, of any value.

It is evident, as shown in Fig. 4, that the transformer T1 T2 may be replaced by two identical thermionic tubes ll, i2 symmetrically controlled (push pull), the anode of one of the tubes being connected to the terminal B1 and the anode of the other to the terminal B2. A resistance of suitable value may be disposed between 131 and B2 (and be thus in parallel with the two double ranges), the continuous anode voltage of the two tubes being applied to the middle of this resistance. The output terminals B, B" are connected to balanced modulators 13, M which suppress the carrier and apply the currents of side band frequency to the antennas A1 A3 and A2 A4, respectively. The carrier is applied uniformly to the four antennas but in quadrature phase with respect to the sideband currents.

The most suitable values for the different elements of the arrangement may be found with the aid of general theories of radio-electricity. The following figures are given by way of example and are not to be taken as absolute.

The value to take for make N =14.

The values of 1m and N being fixed, there will be known, after what has been said above, the order of magnitude of all the inductors and capacitors; in order to learn the exact values it is sufiicient to fix the value of a single inductor or capacitor, for example, the value of U1, which is the largest inductance, one could make The value of resistance R (which represents the total ohmic resistance of the circuit, comprising here that of the inductance coil) and the value of r depend upon and upon ,u; it is suitable to make R= ohms r 0.127R ohms The capacitors of the simple circuit which occupy the first place in each of the four ranges; that is to say, the capacitors C'1, C"1, C'z, C"2, should be extremely large, and therefore difiicult to realize. From the practical point of view, it is important to observe that an increase in the value, as large as is wished, of the above capacitors from their theoretical values, has only a negligible influence on the precision of the results given by the arrangement; consequently, the said capacitors may be eliminated (and also, eventually, the capacitor 0'3, and even C"3) in reducing the corresponding circuits to only the inductors in series with the resistors.

It is apparent that, among other possibilities, the arrangement may be realized in a manner to give, for each sinusoidal term of the control voltage, a polyphased symmetrical system of voltages having any number of phases. For example, in order to obtain a triphased system, it is necessary t to dispose, in parallel between the terminals B1 and B2, three double ranges constituted in the fashion already indicated, and the values of N, R, r being the same for the three double ranges. The second fundamental relation may be generalized in an apparent manner; by calling, respectively, L's, L9, L" '9 the inductors and C's, C"9, C" '9 the capacitors of the circuit 9 in each of the three double ranges. It is necessary to have, whatever 9 may be.

Farm rende The arrangement may undergo several modifications, each to perceive, either in the manner of feeding through a source the essential part of the arrangement, or in the constitution and disposition of the elementary impedances and the ranges of impedances; in particular, in the order in which the constituent elements of each simple circuit are disposed.

The phasing network of the present application may be used in conjunction with a system for radiating modulated waves or in any system in'which single phase currents are converted into two-phase currents having a similar phase shift over a wide band of frequencies. While the present application claims the phasing network, a copending application Serial No. 278,242, filed June 9, 1939, entitled System of radiation of modulated radio-electric waves, claims the system as a whole.

I claim as my invention:

1. A phasing circuit including the combination of a plurality of simple circuits, at least some of said simple circuits including serially connected capacitors and inductors, said simple circuits being connected in four series-parallel rows, Where L'1, L'z, L"1, L": represent said inductors and 0'1, 0'2, -C"1, 0"2 represent said capacitors having the relation where a is a constant and Li, 0'1 and L'z, C'z represent serially connected rows, and the relation in which L"1, C"1 and L"2, C": represent respectively the other serially connected rows, and in which where s is a constant less than unity and input and output connections to said rows, whereby single phase currents applied to the input are derived as two phase output currents having quadrature relation over a band of frequencies.

2. A phasing network for deriving two phase currents of substantially quadrature phase from single phase currents covering a range of frequency including four rows of a plurality of parallel simple circuits each responsive to a difierent resonant frequency, means for connecting two of said rows in series and said two series rows in parallel, said simple circuits being arranged so that the responsive resonant frequencies form geometric progressions in each row, and input connections to said parallel rows and output connections between said series rows and a point of invariable potentia] with respect to said input connections.

3. A network of the character of claim 2 in which each of said simple circuits includes a resistor.

4. In a network of the character of claim 2 a push-pull thermionic amplifier having its anode circuits connected to said input connections.

5. A phasing network including a plurality of simple circuits each resonant to a different frequency, said simple circuits being connectedin parallel and arranged in four series-parallel rows and arranged so that the resonant frequencies form geometric progressions in each row, means for impressing single phase currents of a band of frequencies on said network so that two of said rows present resistive characteristics and two of said rows present respectively reactive characteristics of opposite sign.

6. A network of the character of claim 5 further characterized by having a resonant frequency range greater than the range of the applied frequencies whereby throughout the applied range'two phase currents of substantially quadrature phase relationship may be derived.

'7. A phasing network including a plurality of circuits, each of said circuits including resistive and reactive elements, said circuits being connected in parallel, means for connecting in seriesparallel four groups of such plurality of circuits, said groups covering difierent and overlapping bands of frequencies and further arranged to form geometric progressions as to the resonant frequency of the circuits in each group.

8. In a network of the character of claim '7, means for applying currents of single phase and variable frequency to said network, and means for deriving from said network two currents of substantially quadrature phase irrespective of the frequency of said applied currents.

GUSTAVE LONGO.

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