US 2803750 A
Description (OCR text may contain errors)
Aug. 20, 1957 A. H. ABDEL DAYEM SYNCHRONIZED MICROWAVE GENERATOR Filed J an. 4. 1954 SCILLATOR.
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United States Patent Q SYNCHRONIZED MICROWAVE GENERATCR Aly Hassen Abdel Dayem, Alexandria, Egypt, assignor to Patelhold Patentverwertungs- & Electra-Holding A.-G., Glarus, Switzerland, a joint-stock company Application January 4, 1954, Serial No. 402,082
11 Claims. (Cl. 250-36) The present invention relates to a synchronized micro- Wave generator which is particularly suitable for amplification of frequency modulated microwave signals, but which may also be used as transmitter for amplitude modulated or pulse modulated signals with great carrier frequency stability.
The microwave generator in accordance with the present invention is characterized in that it contains two microwave oscillators which are connected by means of a directional coupler with the synchronizing signal source on the one hand, and with the output circuit of the generator, on the other. In connection therewith the directional coupler prevents a coupling between the synchronizing signal source and the output circuit. The oscillators may be of any suitable construction. It is only necessary that the oscillations which are produced therebe may be synchronized by means of a synchronizing signal connected to the output thereof.
An object of the invention is to provide a network for coupling a plurality of microwave oscillators to a commonsynchronizing source and to a common output circuit in such manner that there can be no transfer of energy between the several oscillators or between the synchronizing source and the output circuit. A further object is to provide a network of the type stated in which the waves produced by the several oscillators neutralize each other at the point where the synchronizing signal is injected into the network, and thus have no back effect upon the synchronizing source. A further object is to provide a network of the type stated in which variations in the impedance of the output circuit can have no disturbing effect upon the several oscillators.
Further objects and advantages in accordance with the present invention will become more obvious from the following description when taken in connection with the accompanying drawing wherein- Fig. 1 shows schematically one embodiment of the present invention;
Fig. 2 shows a directional coupler which may be used in connection with the present invention; and
Fig. 3 shows a further modified embodiment in accordance with the present invention.
Referring now more particularly to Fig. 1 of the drawing reference numerals O1 and Oz designate two microwave oscillators, which are preferably constructed identically. The oscillators O and 02 are connected by lines L1 and L2 with points 1 and 2 lying on a directional coupler of the so-called hybrid-ring type. Depending on the particular structure of the generator, this ring may be formed as a closed concentric line or as a closed symmetric line. The coupling points 1 and 2 lie a distance of a half wavelength apart from each other, as measured along the circumference of the ring and the output circuit of the generators is connected at point 3 of the ring which is spaced a distance of a quarter wavelength from point 1 and three-quarters of a wavelength from point 2. The synchronizing signal is injected into the arrangement at point 4, which is in the center be tween points 1 and 2, so that points 1 and 2 are each spaced a quarter wavelength from such point 4.
In order to facilitate understanding of the operation, it must be remembered, that transmission of energy between two points of the ring can only take place if such points are spaced apart a quarter wavelength or an odd number of quarter wavelengths from one another. Only when the waves which depart from the first point arrive in phase at the second point 2 will there be an energy transfer. A transmission of energy can never take place between two points which are spaced apart a half wavelength or a multiple of a half wavelength because the waves which emanate from the first point arrive in out of phase relationship at the second point.
Referring now to the particular embodiment of the present invention, it becomes obvious that in the arrangement of Fig. 1, a transmission of energy is possible from the two oscillators to the output circuit as well as between the synchronizing signal source and each of the oscillators. However, it is not possible to transfer energy between the synchronizing signal source and the output circuit, and it is also impossible to have any transfer between the oscillators themselves.
In order for the energy at the output circuit to be the sum of the two oscillators O and 02, .it is necessary that the waves at points 1 and 2 be of opposite phase, as point 2 is a half wavelength nearer the output circuit than point 1. On the other hand, the waves produced by the synchronizing signal source are in phase at points 1 and 2. By making the length l of line L2 a quarter wavelength or an odd number n of quarter wavelengths longer than the length I of line L1, the waves of oscillator 02 lag the waves produced by oscillator 01 by a quarter wavelength or by an odd number of quarter wavelengths. The waves travel through the longer line L2 in which they are subjected to an additional phase displacement, so that at point 2 the necessary phase difference of with respect to the oscillations at point 1 is obtained. The waves produced by the two oscillators thus are additive at point 3 of the ring which is connected with the output circuit of the generator. On the other hand, the waves produced by the two oscillators O and O2 arrive at point 4, i. e. the point at which the synchronizing signal is injected, in opposite phase. Under the assumption that the frequencies and the amplitudes of the produced oscillations are equal, there is no back effect of the oscillator waves on the synchronizing signal source. This is a second advantage in accordance with the present invention. The frequencies of the produced oscillations are by force of the: synchronization identical. The amplitudes of the two oscillations are not greatly different from each other since they are produced by oscillators of the same construction; it is furthermore possible by any well known device 5, which may permit adjustment of the amplitude of at least one of the oscillators, for example oscillator 02, to assimilate the amplitudes of the two oscillators.
If the microwave generator is built as a high frequency waveguide oscillator, then instead of the hybrid-ring, a hollow-tube directional coupler comprising adjacent parallel tubes with an apertured wall in common type may be used, as shown in Fig. 2. In a directional coupler of this type, it is known that no energy is transmitted along the paths indicated by the dotted arrows, while transfer of energy is possible in all other directions. If now the oscillators, the output circuit and the signal source are connected to corresponding points 1 to 4, which correspond to the same points in Fig. 1, then the hollow-tube directional coupler operates functionally analogous to the hybrid-ring. A further description of the operational effect of such arrangement is therefore not believed necessary and is accordingly dispensed with.
In connection with the use of the arrangement of the present invention as an amplifier for frequency modulated waves, the signal .whichs isttobeamplified. is injected as a synchronizing. signal ..at-point 4 of the arrangement. The.frequencies-,of-.-the waves produced by theoscillators O1 and Oz followthatof the synchronizing.signal, and the amplified signal w-ill-. appear at the output 3 .of the arrangement, which, forexarnple maybe connected to a transmitter.v antenna-or a --furtherampl-ifierstage. Changes in the. loading of the amplifier, such as are caused, for.example,"gby changes in the. antenna impedance within the. used frequency range, have no effect on the amplification derived. from oscillators O1 and .02. This is a third advantageinaccordance with ,the present invention. 7 As the reflected load variation which is caused by mis-matching theirnpedanceszis. applied equally to the two oscillators, .,themis match and its influence on the operation of the oscillators-is reduced.
For use ,of the arrangement is accordance with the present invention as a transmitter-for amplitude modulated orimpulse modulated signals, the-waves produced by the two oscillators are simultaneously modulated in amplitude orsin the-rhythm, ofthe pulses. A wave of the carrierfrequency isuused asa synchronizing signal. Consequently, this frequency is kept substantially constant even with highdegrees of -modulation. In connection therewith it should be mentioned that the use of the. so-called lockedtransrnitters for'purposes of stabilizing. the carrier frequency of an amplitude modulated microwave oscillator. isknown. However such known arrangements do not produce'the particular advantages, which are offered by the presentinvention.
A further possibleuse of the so .far described invention, as shown in'Fig. 3, resides in forming each oscillator of two part oscillators.
The reference-numeral R identifies the directional coupler which forms the basis.of the arrangement already describedabove. The two oscillators O1 and 02 are connected thereto by lines L1 and L2 the respective lengths l, l of which ditter by an odd number n of quarter wavelengths. Both oscillators are constructed identically, so that it is only necessary to describe one of the oscillators in detail, namely oscillator 01. It consists of two preferably identically constructed part oscillators Oi'and 01":Which are connected with points a and b of thedirectional coupler R by lines A and B which are of equal length [2. The outlet point 0 of the directional coupler liesa quarter wavelength from points a and b, asmeasured along the ring of the directional coupler. If the two'part oscillators operate in phase or cophasially, then the sum of the waves produced by the two partoscillators appears at outlet point 0. This sum ofthe waves is then transmitted via line L1 to the directional coupler R0 of-the microwave generator. On the other hand, a part of the synchronizing signal is conducted to the oscillator 01 over the same line, this signal being derived from the synchronizing signal source connected to point..4 of thedirectional coupler R0. The directional coupler R vdistributes this signalcophasially to the two part oscillators O1 and 01" so that the same, as assumed above, actually operate cophasially.
The symmetry in the manner of operation of the two part oscillators is enhanced if a refiectionless matched impedance W is connected to the fourth point of the directional coupler R1, i. e. to the point d. The provision of this impedance offers the further advantage that-with stoppage of one of the part oscillators a definite load impedance is provided for the other part oscillator.
The adjustment and monitoring of the microwave generator may be done in a particularly advantageous manner by providing ameter M for measuring the high frequency energy in the impedance W since the value thereof reaches a minimum with proper operation of the system.
It is further possible to provide a further, sub-division in such manner that each part oscillator 01' and O1" is formed of a plurality of oscillators. As the foregoing considerations and descriptions are equally applicable to such case, a further detailed description is not necessary.
If the microwave generator is constructedaas a waveguide-type,'then thedirectional coupler is used in place of the hybrid rings, as has been'indicated already above. The directional coupler'permits the operation of the microwave generators over a considerably larger'frequency band than is possible with ring typedirectional couplers. However, the band width of the latter is sufficient for all practically used .modulating types with a given carrier frequency.
1. A synchronizing microwave-generator comprising two substantially identical microwave oscillatorshaving substantially the same operating frequencies, a synchronizing signal source, a common output circuit-for said oscillators, .anddirectional coupler means for coupling said oscillators individually with said source and jointly with said outputcircuit.
2. Microwave generator according to claim 1' wherein the'transmission lines connecting said'oscillatorswith'said directional couplerditfer byan oddnumberof'quarte-r wavelengths.
3.v Microwavegenerator :accordingto claim 1 wherein said directional coupler is a hybrid ring.
.4. Microwave generator. according to-claim 1 wherein said directional coupler comprises adjacent parallel tubes having a common. aperturedwall.
5. Microwave generator according to claim 1 further comrising means for'varying.theamplitude-of at-least one of said: oscillators to assimilatethe amplitudes of said oscillators.
.6. A synchronizing microwave generator comprising two microwave generators each of which includestwo microwave oscillators, a directional coupler for-each generator, each ofsaid. directional couplers having'an outlet point therein, transmission lines connecting the microwave oscillators of each generator to the directional coupler thereof.at points spaced from the outlet point thereof by an odd number of quarter wavelengths, an output circuit, .a synchronizing signal source, a main directional coupler having said outputcireuit and said synchronizing :signal .source connected thereto at points spaced apart by a half wavelength, transmission lines which difier in length by an odd number of quarter wavelengths connecting the output points of the directional couplers of said generators to points onsaidmain .directional coupler spaced a quarter wavelength from the points of connection of both said synchronizing signal source and said output circuit.
7. Microwavegenerator according to claim'6 wherein said directional couplers are formed as hybrid rings.
8. Microwavegenerator according to claim 6 wherein said directional couplers are formed as wave .guide couplers.
9. Microwave generator according to claim 6 wherein each oscillator consists of aplurality of oscillators.
10. Microwave generator according to claim6 wherein a matched impedance is connected to each directional coupler of said generators.
11. Microwave generator according to claim 10, in combination with means for measuring the energy in said impedance.
References Cited in the'fileof this patent UNITED STATES PATENTS 1,889,083 Wintringham 'Nov. 29, 1932 2,436,828 :Ring Mar. 2, 1948 2,445,895 Tyrrell- July.2 7 1948 2,568,090 Riblet Sept. 18, 1951