US2498076A - Wide-range sweeping oscillator - Google Patents

Description

Feb. 2l, 1950 H, R FQSTER 2,498,076

WIDE-RANGE SWEEPING oscILLAToR v Filed Sept. 24, 1947 300 j '-500 SYN.

OUT. +500 -300 INVEN TOR.

ATToREY Patented Feb. 2l., 1950 UNITED OFFICE Harry R. Foster, East Grange, N. J., assignor to Ohmega Laboratories, Fine Brook, N. J., a partnership Application September 24, i947, Serial No. 775,826

(Cl. E50-36) l2 Claims. -1

This invention relates to means for obtaining a testing apparatus which can be used for various purposes such as servicing a standard A.M. radio broadcast or a television receiver, video and other amplifiers or other equipment requiring the use of a frequency having a sweep much wider than anything heretofore used or available.

It is the principal object of my invention to provide an apparatus which will cover an enormous spectrum extending from just above the audio range to over 500 megacycles and by means of additional adjustments the spectrum may be extended to 1,000 megacycles or higher wherein at various parts of this spectrum a frequency sweep of 30 megacycles or over may be obtained.

A further object is to provide an apparatus having a sweep output that will cover successively each color television frequency band.

A still further object is to provide a megasweep apparatus for field as well as laboratory and research work use which is small, (the front panel with all regular adjustments available thereon being only 15 x 9) so it can be conveniently carried by one person.

Other objects will be discerned by one skilled in this particular field. In order to illustrate the manner in which the objects are obtained, reference is made to the annexed drawing where- 1n,

Figure 1 illustrates diagrammatically the circuit of my new and improved circuit together with a plan view of the wave guides and wave meter used in Connection therewith and forming part of the circuit.

Figure 2 is a sectional view on the line 2 2 of one of the wave guides and also showing a cross section through the wave meter.

Figure 3 is a sectional view on the line 3-3 of Figure 1.

Figure 4 is a fragmentary View showing the crystal detector, which is only diagrammatically illustrated in Figure 1.

In Figure l the resistances used in the circuit are numbered RI to R20, while the condensers are designated as CI to C8, and the potentiometers are numbered PI to P5. OI and O2 are reiiex oscillators of the Klystron type which are adapted to operate at approximately 10,000 megacycles. The tube V3 is one that is adapted to deliver a saw tooth wave form potential to the tube OI by way of the potentiometer P4, condenser Cl, and switch S I. While the voltage supplied by the tube V3 is used to vary the frequency of the oscillator OI it also simultaneously supplies the voltage to the X axis of an oscilloscope which is connected to the terminals syn. and out. One of these terminals, Va may be a variable voltage supplied thereto by the potentiometer P4 or a fixed voltage supplied by way of switch S2, either voltage may be used to drive the X axis of the oscilloscope. rlhe switch SI is supplied with a toggle type spring I so that after the switch is thrown to the upper position into engagement with the contacts 2 and released, spring I will cause it to automatically return to the normal closed position as indicated. The function of the switch SI will be later referred to. v

The oscillator OI is provided with a wave guide 3, and the output lead 4 of this tube` extends a substantial distance by way of an insulator 5 into its wave guide as indicated in Figure 2. The output lead 6 of the oscillator tube O2 is positioned in an insulator l located in wave guide 8. The two wave guides 3 and 8 are preferably fastened together to a mounting panel 9 carrying the resistances, condensers, potentiometers, etc., making up the circuit. The upper part of the wave guide 3 has a slot therein to receive a relatively fixed or padding attenuator I0, which may be of suitable insulating material such as Bakelite, that is carried by a stud Il fastened to the panel 9. The wave guide 8 carries within its interior an adjustable attenuator I2 which may be of any suitable material such as Bakelite, fastened by a screw I3 to an insulating stud I4. Around the stud I' is positioned an expansible spring I5 held in place by a washer i6 that is held to the upper end of the stud I 4 in a satisfactory manner as by a cotter pin. With this arrangement the spring i5 normally holds the attenuator I2 against the inner edge wall of the wave guide 8. An adjusting screw Il carried by a support member i8 has an operating knob or holder I9 at one end so when it is turned the stud I4 is moved inwardly to cause the attenuator I2 to move away from the inner wall of the wave guide 8 for purposes which will be later referred to. Both of the adjacent walls of the wave guides 3 and 8 are provided with a plurality of holes 20 which act as a directional coupler means to which reference will be later made. The extremity of the wave guide 8 opposite the insulator l that receives the tube output lead 6 has a slot 2I therein to receive a triangularly shaped card 22 of insulating material therein. The attenuators I0, I2 and card 22 are treated on their surfaces with a thin layer of resistance material such as carbon for purposes which will be later described. Mounted on the wave guide 3 is a wave meter 23 which includes a block 24 having a graduated hub 25 Which supports a tubular member 25 that is internally threaded to receive a threaded stud 21 carried by an operating cylinder 28 which in turn is calibrated into a hundred divisions to cooperate with the calibrations on the hub 25. Preferably the member 26 has a plurality of slots 29 and a groove at one end to receive a spring 3Q that applies a contracting force to the split ends of the member 26 so as to insure that the micrometer adjustment of the cylinder 28 will be positive and accurate. Extending from the threaded stud 2'1 is a rod 3| which forms a coaxial cavity tuning member with the tubular member 32 carried by the block 24 which is fastened by screws 33 through the top surface of the Wave guide 3. Positioned within the block 26 is a tube 34 for receiving the rod 3l and near the inner end of the tube 34 is located a pin 35 that extends through a clearance hole 36 in the block 24 into the chamber of the wave guide 3. The purpose of this pin and other circuit parts will be later referred to in the operation of the structure.

Mounted adjacent the wave meter, and at the extremity of the wave guide 3 is a detector 3l, preferably of the crystal type and shown in arssembled position in Figure 4 and diagrammatically in Figure l. The detectoris connected to the wave output terminalWO and also to a decoupling monitor circuit including the resistors Ri and RilI and condensers C and C6 which are connected through a resistor R9`to a D; C. microampere meter MA which serves 'to indicate the arrival of energy at the detector, as well as at the output terminal WO, it being understood that the monitor circuit picks up a D. C. component vout of the detector circuit. In the operation of the mega-sweep apparatus' after current has been turned on, it energiz'es the circuits; the potentiometer Pl is adjusted to one of its maximum positions and the attenuat'or l2 is set to lits minimum posi-tion, i.- e., with all the spring tension on the stud i4 at' a minimum. Then, the switch Sl is turned'to engage theco-ntacts 2, and the potentiometer Pl is given a peaking adjustment until the current in the meter MA reaches'the maximum. This peaking assures that the repeller voltage fof oscillator G2 is set for operation in the proper manner. While the switch Si is held in engagement with the contacts 2` it short circuits the resistance R9. The micrometer or cylinder 23 on the wavemeter is adjusted until there is a dip in the lcurrent reading on the ammeter MA. This reading is a measure of the' frequency Iof the oscillator O2l.

Oscillator Ol' is setby 'rst peaking the D.- C. current from the detector by means of? the lpeak-- ing potentiometer P3. Small frequency shifts may 'also-be made by the potentiometer P2;

The output frequencyv on the sweep circuit is determined by the difference i-n 'frequency be-l tween the two oscillators O2 and Ol. Thisv difference in frequency may be set at any ydesired value by obtaining the immediatereading assocfiated with oscillator O2 as described, and setting oscillator Ol to a frequency which would give a dip on the meter with a micrometer read-ing which corresponds to the desired frequency.

The complete tuning procedurebriely Iout-lined above is necessary only when the sweep apparatus is shifted to a new frequency region in the Vcarrier band.

The energy from the signal oscillator O2 is passed to waveguide S and past the adjustable or variable attenuator l2 which absorbs, 'more or less, energy depending on its adjustment in its wave guide. After passing the attenuato i2 the energy passes through the directional coupler comprising one or more holes 20, into the wave guide 3. Any energy that is not passed through the coupler 2D is received and dissipated on the card terminator 22 which as heretofore explained is covered with an energy absorption material suchasnely powdered carbon, so that these waves of energy are not thrown back in the wave guide so they will not interfere with the passage of the waves through the coupler 20.

The energy from the oscillator OI which is passed through the lead 4 and the wave guide 3, is frequency modulated by a variable voltage from the saw tooth type tube V3 that is applied to the repeller member of the tube Ol. The energy is passed from the lead 4 past the relatively fixed or padding attenuator I0 onto the detector 37, being mixed with the waves coming from the wave guide-3.

Since the wave meter 23 is positioned directly before the detector the frequency of both oscillators is measured by this co-axial cavity type absorbtion wave meter. It is well understood that when two different frequenciesv are mixed in a non-iinear device such as a crystal detector the frequency difference is obtained and this difference is what is passed on to the wave output WO. It is important to keep in mind that in order to obtain a constant signal output, the larger signal, which in this case comes from the oscillator Ol is the one that is frequency modulated, even though its output may vary in amplitude the output signal will not vary, due to the fact that as in most detectors the output amplitude depends on the small signal. Also, when the local oscillator is frequency modulated an' undesired result of this is that amplitude modulation is obtained. This is the reason that the output voltage amplitude is made dependent upon the signal oscillator.

By the use ofthe lcircuits and apparatus described I have obtained a mega-sweep means for obtaining the objects heretofore set forth as well as others all of which I have found from practical experience to be highly useful.

I prefer to have an apparatus that will deliver substantially a constant output which will only give a true response of an electrical network or amplifier'. In some special cases in order'to obtain a greater frequency sweep .both the tubes Ol and O2 may be frequency modulated. But, so far as present day equipment is concerned I prefer to only modulate one oscillator in order to tobtain a substantially constant current outpu I claim:

l.. A radio structure including two ultra-high frequency oscillators, a wave guide for each oscillator with means for taking the energy output ofr each oscillator to its guide, means for passing the energy of certain Aof the Waves from one guide into ythe other, a detector preferably of the crystal' an attenuator located therein, the attenuator on said other wave guide being mounted in a relatively xed position while the other attenuator is mounted for quick adjustment in the said one wave guide.

4. A radio structure as set forth in claim 1 further characterized in that said means for passing waves from one wave guide into the other, comprises a directional coupler consisting of at least one opening through the adjacent side walls of the guides.

5. A radio structure as set forth in claim 1 further characterized in that each wave guide has an attenuator located therein, the attenuator on said other wave guide being mounted in a relatively fixed position while th-e other attenuator is mounted for quick adjustment in said one wave guide, said means for passing waves from one wave guide into the other comprising a directional coupler consisting of at least one opening through the adjacent side Walls of the guides and means located at the end of the wave guide having the quick adjustable attenuator and opposite thereto for absorbing the energy waves that do not pass through the directional coupler.

6. A radio structure as set forth in claim 1 further characterized in that each wave guide has an attenuator located therein, the attenuator on said other wave guide being mounted in a relatively xed position while the other attenuator is mounted for quick adjustment in said one wave guide, said means for passing waves from one wave guide into the other comprising a directional coupler consisting of at least one opening through the adjacent side walls of the guides and a triangularly shaped termination card having energy absorbtion material thereon located in a slot in the end of the wave guide having the quick adjustable attenuator and opposite thereto, one apex of the triangularly shaped card being pointed toward the adjustable attenuator.

7. A radio structure having an output terminal and including a signal oscillator and a variable voltage frequency modulated oscillator, a wave guide for each oscillator with means for connecting the output terminal of each oscillator into one end of its wave guide, a detector preferably of the crystal type positioned at the opposite end of the guide having the output terminal of the modulated oscillator, an attenuator in this guide between the said terminal and the detector, an adjustable attenuator in the other wave guide near the signal oscillator terminal; a directional coupler between the two wave guides on similar sides of their attenuators, and a wave meter having members forming a co-axial cavity carried by the guide having the detector, a pick up pin extending from the inner member of the co-axial cavity into the wave guide.

8. A radio structure as set forth in claim 7 further characterized in that a decoupling monitor circuit is connected to the detector for taking a direct current component from the detector circuit and a direct current micro-ampere meter is used for utilizing the direct current component to indicate the arrival of energy at the crystal and output terminal of the structure.

9. A wide-range sweeping apparatus including two ultra high frequency oscillators with means for giving each an adjustment for maximum output energy, a wave guide for each oscillator and each guide having a terminal to receive the output of its associated oscillator, means for applying a saw tooth type voltage to one of said oscillators for modulating its frequency, the guide connected to the modulated oscillator having a detector preferably of the crystal type and also carrying thereon a co-axial wave meter located directly before the detector, wave coupler means common to both guides, an attenuator for each guide, the one in the guide associated with the non-modulated oscillator being adjustable.

10. A wide-range sweeping apparatus including two ultra high frequency reflex oscillators, a wave guide connected to each oscillator with their output terminals positioned in one end of their respective guides, means for frequency modulating the output of one of said oscillators, a detector located in the wave guide receiving the modulated output at the end opposite the wave receiving end, a cavity type wave meter positioned over the guide carrying the detector and having a reception pin located so as to absorb energy from said wave guide carrying the detector, the two f wave guides being interconnected by wave coupling means and attenuator devices for both wave guides.

11. A wide-range sweeping apparatus including two ultra high frequency reflex oscillators, a wave guide connected to each oscillator with their output terminals positioned in one end of their respective guides, means for frequency modulating the energy of at least one of said oscillators, a detector located in one of the wave guides that receives the frequency modulated energy, the detector being located at the end of the guide opposite the energy receiving end, and a cavity type wave meter positioned on the guide carrying the detector and having means for absorbing energy from said guide, the two wave guides being interconnected by wave coupling means.

12. A wide range sweeping oscillating apparatus including two ultra high frequency oscillators with means for controlling the action thereof, said means including impedance devices, at least some of which are adjustable and also including an electron tube which will deliver a characteristic voltage to one of said oscillators to vary its output frequency, a wave guide connected to the output terminal of this one oscillator, a wave guide connected to the output terminal of the other oscillator, a directional coupler means for passing the waves from the last mentioned guide into the first mentioned guide, a detector carried by this rst guide and connected to the wave output terminal of the apparatus and an adjustable wave meter also carried by the rst guide for the purpose described.

HARRY R. FOSTER.

REFERENCES CITED The following references are of record in the le of this patent:

UNTIED STATES PATENTS Number Name Date 2,253,589 Southworth Aug. 26, 1941 2,296,962 Tuniek Sept. 29, 1942 2,423,526 Sontheimer July 8, 1947

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