US 2756331 A
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Filed April 14, 1954 .DaFDOVIT- INVENTORS HARRY R. FOSTER ELMO E. CRUMP anni@ ATTORNEY July 24, 1956 RMB ld N mlldm m. N mQIIEIJmN QUTTHMQ voallll vrw MII-n o url Tllb n United States Patent() SYSTEM FOR OBTAINING HIGH FREQUENCIES Harry R. Foster, Lake Valhalla, and Elmo E. Crump, West Caldwell, N. J.
Application April 14, 1954, Serial No. 423,200
11 Claims. (Cl. Z50-36) This invention relates to a new type of signal generator whose frequency can be very accurately controlled for use in electronic work. In our patent application, Serial No. 266,498, led January 15, 1952, for a Crystal Control Decade Oscillator, there is shown and described a system which is found to be far superior to oscillators of the heterodyne or beat frequency system or the resistancecondenser feedback system. As stated in the application above mentioned we found that both types of instruments made according to the systems just mentioned are accurate to only about per cent and that their stability is only about lo() as good as the arrangement set forth in our said application. From our further study and tests we have found that as of today greater accuracyis needed than at the time our pending vapplication Was filed and from our study of the various problems involved we have now been able to get a continuous frequency coverage from 100 megacycle to 500 megacycle in discrete steps.
- One'reason why the Decalator system of our pending application will not reach into the 100 to 500 megacycle range is that from the practical standpoint crystals are not available to work in this range of frequency consequently in our present system we start at a relatively low frequency, to 11 megacycle and generate the higher frequencies in the manner shown in our drawing wherein,
Figure l is a diagrammatic view of one arrangement of our present invention.
Figure 2 is a modiiication which may be utilized in connection with Figure 1.
Figure 3 shows a further modied arrangement which may be also used in connection with Figure l.
ln the different views wherein like numbers refer to corresponding parts #l is an oscillator which includes 10 separate quartz crystals controlled by the switches S-1 and S-Z. These crystals being arranged in 10 kilocycle steps as tabulated in the drawing. These crystals can be pulled in tive l kilocycle steps down and five 1 kilocycle steps up. While the switches S-l and S-2 are shown individually it is preferable that they be mounted so as to operate simultaneously in connection with any one of the individual crystals. The switch S-2 is electrically connected to switch S-3 which controls the operation of the condensers and impedance coils adapted to be associated with the crystals, it being understood that a condenser, connected in parallel with a crystal, acts to lower its frequency while a reactance coil so connected will raise the frequency while a series connection will act in reverse order and the selection of one of the methods of connection is influenced by the frequency range being used. The buffer amplifier B will pass 4 to 4.1 megacycles and this serves to isolate the oscillator A from the modulator E.
C is a crystal control oscillator which has 10 separate quartz crystals connected thereto through the switch S-4, these crystals being distributed in 100 kilocycle steps from 6 to 6.9 megacycles as tabulated in the drawing. The crystals are pulled in ten 100 cycle steps up in frequency. The switch S-S is preferably connected to operate simul- 2,756,331 Patented July 27 4, 1956 ICC taneously with the switch S-4 so that each crystal may be properly brought into circuit. Switch S-5 is connected to the switch S-6 which controls the adjustable condensers connected thereto. The operation of the condensers being the same as previously described. Oscillator 2 is connected to a buffer amplifier to isolate the oscillator C from the modulator E which is connected to a band pass filter F which in turn is connected to the harmonic generator or multiplier G that is connected to the band pass filter H of the range given thereon and this lter is connected to the tuned selective amplifier I which delivers the nally selected frequency to the output circuit. In Figure 2 we have shown a harmonic generator which may be connected to the band pass filter F and a mixer connected between the elements G and H. 'I'his particular harmonic generator can be adjusted to multiply the frequencies between l0 and l1 megacycles by 10, 20, 30 or 40 thereby supplying a greater range of frequencies which may be mixed with the multiplier G and the lter H. In Figure 3 we have shown a generator for supplying a` source of power for the purpose of increasing the energy of the lO-ll megacycles components by any number between l00 and 400. This energy being connected to a mixer inserted and connected between the units G and H whereby the mixer will heterodjme the components coming from the lter unit F.
` We have found that this system lls a long-felt want'in signal sources wherein high stability and high frequency accuracy is obtained. The output being held to the full crystal stability of plus or minus 0.005%, stated in another way 'the crystals'are operated Within a frequency range where their stability is steady and accurate and then this frequency is passed through a lter and then raised'to a higher frequency by a harmonic generator or multiplier, as for example, suppose the input to the harmonic generator is 10.615 megacycles. The output would conetc., up to the highest harmonic that falls within the spectrum of interest, i. e., 47th harmonic=498.905 megacycles, which frequency is way beyond the scope of any crystal of which we are familiar with and then ltered and ampliiied to the high frequencies desired.
While we have shown in Figure 1 the block diagrams lettered E-I it is to be understood that these cover the necessary range to get a certain output result. For example, the band pass filter H has band passes of at least less than l0 megacycles wide at any particular frequency between -500 megacycles and in the same way the tuned selective amplier I would take care of approximately 10 megacycles steps coming from the filter H. Also it is to be understood that a l0 megacycles oscillator with a multiplier may be used to bring the same up to the 100-500 megacycles range, these multipliers, therefore may be in the order of 2, 3, 4 or 5 and mixed together with the output of the harmonic generator or multiplier G. In the arrangements indicated in Figs. 2 and 3 we get a further output result as heretofore defined. By way of illustration suppose 10.5 megacycles is coming from the band pass filter F assuming the multiplier n of Fig. 2 is 30 then there would be delivered the 30th harmonic or 315 megacycles which would enhance all the harmonics around the 315 megacycles range.
Having thus described our invention, what we claim is:
l. A crystal controlled oscillator system as herein described, comprising two oscillators identiiied herein as A and C, each connected to switches having at least ten contact steps selectively connected to their respective connected to a buffer amplifier and thenboth amplifiers connected to a double balanced modulator which is connected` to a band pass lterl of the order of 10-11 megacycles which is connected to a harmonic generatorY that is connected to a band pass iilter of the order of 100-500 megacycles which in turn is connected to a tuned selective amplifier of the order of 100-500 megacycles that delivers the output from said oscillators.
2. An oscillator system as set forth in claim 1, further defined inthat eachV of the said oscillators is arrangedv in decade steps such as dened in the ten steps associated withthe said oscillators.
3. An oscillator system as set forth in claim 1, further defined in that each of the said'oscillators is arranged in decade steps such as dened'in the ten steps associated with the "said' oscillators, and further defined in that the frequencies tabulated beside oscillator A may be ad- ]usted down or up in ve steps of `1 kilocycle each for example down to 4.090 megacycles or up to 4.100 megacycles.
4. An oscillator system as set forth in claim 1, further dened in that. each of the said oscillators is arranged in decade steps such as dened in the ten steps associated with the said oscillators, and further defined in that the frequencies tabulated beside oscillator C may be adjusted'in'decade steps of' 100 klocycles. 5. An oscillator system as set forth in claim 1*,.further defined in that each of the said oscillators is arranged in decade steps such as dened in the ten steps associated with the said oscillators, and further defined in that the frequencies tabulated beside oscillator C may be adjusted in: decade steps of 100 kilocycles, and further defined in that reactive elements may be switched in series with the crystals whereby the frequency steps may be of the order 'of 100 cycles. n
6. An oscillator system as set forth in claim 1, further dened'in that the double balanced modulator is arranged to give the sum of the input frequencies.
7. An oscillator system as set forth in claim 1, further dened in that the harmonic generator delivers energy distributed at all multiples of the iilter 10-11 megacycles input thereto.
8. A crystal controlled double oscillator system as set forth inV claim 1 further defined in that the selective changes are such asto give ten thousand discrete frequency settings in steps of 100 cycles between ten `and eleven megacyles.
9. An oscillatorsystem as defined herein which comprises a multiplier chain including a pair of oscillators connected by decade switches to crystals and suitable reactances, buffers, modulators,` filter, amplifier and other Vassociated parts, whereby a complex spectrum from 100 to 500 megacycles can be obtained at a high degree of accuracy in the output. "101 A crystal controlled oscillator system as setY forth in claim 1 further dened in that a mixer is connected between the multiplier and band pass lter of the order of 100-500 megacycles and a harmonic generator is connected between said mixerl and the 10-11 megacycles band pass filter. p
1'1. A crystal controlled oscillator system as set forth in claim 1 further defined that a mixer is connected betweenv the multiplier and band pass filter of the order of 100-500 megacycles and a separately excited generator having a multiplying power of 100-400 is connected to the mixer.
References C'tedin the iile of this patent UNITED STATES PATENTS