US2459799A - Spurious response computer - Google Patents

Description

Jan. 25, 1949.

W T. DOYLE SPURIOUS RESPONSE COMPUTER Filed Aug. 21, 1947 SPURIOUS RESPONSE COMPUTER INVEN TOR. William 2' 00 Earl R. 80%: flaw Attorney Patented Jan. 25, 1949 2,459,799 SPURIOUS RESPONSE COMPUTER William T. Doyle, Albertson, N. Y., and Earl R. Baker, Delta, 0010.

Application August 21, 1947, Serial No. 769,967

4 Claims. (01. 235-83) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 3'70 0. G. 757) This invention relates to calculator-sand more particularly to a computer for aiding a radio listener in distinguishing between true responses and spurious responses.

There are many situations, in the art of radio signaling, where it is desired to know the exact frequency of an incoming radio signal. In the simplest type of equipment using only tuned radio frequency stages, the incoming signal is detected at only one point in the receiver tuning gamut. Such simple receivers, however, when designed to amplify sufliciently a very weak .signal, are very large and bulky, and are relatively diflicult to operate and use. As a consequence, it has long been a practice to employ superheterodyne receivers which utilize a local oscillator to generate a local signal which is mixed with the incoming signal to produce an intermediate frequency. The intermediate frequency may be easily amplified, and then rectified to obtain the desired modulating intelligence.

Use of a local oscillator, while solving the amplification problem, introduces a new problem in the form of spurious responses, which arise from the presence in the locally generated signal of numerous harmonics. Such harmonics, as well as the oscillator fundamental, mix, both above and below, with the incoming signal to produce the intermediate frequency to which the receiver is tuned. Thu-s, as an example, for an oscillator in which all harmonics up to the fifth are strong enough to produce a detectable output, there are, for a single given incoming signal, ten responses appearing at ten different points on the receiver tuning scale. The receiver operator is faced with the problem of determining which one of these ten responses is the true signal, 1. e, the result of mixing with the proper oscillator harmonic (generally the first or fundamental), and in the proper manner. Whi e the diiiiculty can be lessened by insertin R. F. tuning sta es in front of the mixer, very strong signals will pass through the R. F. stages in spite of anti-tuning in such stages. The receiver operator must, therefore, be prepared to cope with a plurality of responses to the same signal, only one of which is the true response.

It is an object of this invention to provide a computer, by means of which the true response may be quickly discerned from among a plurality of radio responses received.

It is another object of this invention to provide a computer by which the true frequency of a signal may be quickly and accurately calculated from any two responses to that signal, whether or not the true signal is among the two above mentioned responses.

It is another object of this invention to provide a calculator which will quickly indicate where all spurious responses may be expected from a predetermined incoming signal.

An example of such a calculator constructs for use with a particular heterodyne receiver will now be described. From this description the principles of the calculator will be readily understood and it will be manifest how similar calculators may be constructed for any given superheterodyne receiver. In the equations to be set up below, the following nomenclature will be employed:

f-fundamental frequency of local oscillator.

s-frequency of incoming signal.

R-scale reading on receiver (oscillator) tuning dial.

aany integer from 1 through 5, representing the ordinal of a particular harmonic of the local oscillator.

With this condition the reading R coincides with the actual frequency 3 of the incoming signal.

Inasmuch, however, as the incoming signal may in fact mix either above or below the local oscillator, and inasmuch as it may mix 'with any harmonic of the local oscillator from the first to the fifth, a receiver response will be obtained whenever the local oscillator is tuned so that the following relation is fulfilled:

Expressed in terms of dial reading R rather than oscillator frequency this equation becomes:

s=a/2(R 30) 5530 (First equation) Conversely, solving for dial reading R, the equation becomes:

R=2/a(s:30) +30 (Second equation) Basically, the calculator of this invention is designed to solve the last two equations set forth above. In the construction of the calculator, a

iilerent calculating member is employed for each harmonic of theoscillator up to five, higher harmonics-Being of insufficient strength to proona pin l6. means for solving a different equation, depending duce detectable responses. For each harmonic, a pair iof scales is laid out on a common scale member." .One of these scales represents the signal cf teqiiency, s; the other represents the dial reading, Observation of the two equations underconsideration shows that there are two values of s for each R, and two values of R for each s. A cursor is mounted to slide along the twoscales on the scale member. To solve the first equation, a first single index is marked on the cursor, registering with the dial read ing scale. Cooperative with this index is 'a first pair of indices which register with the signal frequency scale. Thus by setting the single index opposite a given dial reading, R, the two signals, s," which could produce that response are found, in'so far as any given oscillator har-- monic. a, is concerned. This corresponds to a solution of the first equation with a held constant.

It ispreferred in the practice of this invention to employ the same cursor in the solution of the second equation. To this end a second single index is marked on the cursor registering with the signal frequency scale. Cooperating with this index is a second pair of indices which register with the dial reading scale. With this set of indices, the second equation may be solved, for any given value of a from one to five, it being understood that there are five such scale members, each independently cooperative with the cursor., 7

The computer may be conveniently constructed of a plurality of disks of decreasing diameters laid one on top of the others and pivotally mounted at the disk centers. Each disk contains a pair of scales, corresponding to a predetermined harmonic from one to five, one of each. pair representing dial reading, R, the other representing signal frequency, 3.

The cursor is preferably diametrically disposed across the disks and pivotally mounted thereon at the disk centers. To avoid confusion, the indices for solving the first equation are marked so that the single index, registering with the dial reading scale, occupies one radius of the diametral cursor, while the double indices, which register with the signal frequency scale, occupy the other radius of the cursor. This disposition of the cooperating indices permits of a, series of slots in one radius of the cursor which register respectively withthe five 'dial reading scales, and a series of slots in the other radius of the cursor which register with the five signal frequency. scales. On the edge of each slot are marked the appropriate indices.

Solution of the second equation is conveniently provided .by marking the single index on the slots registering with the signal frequency scales and the double indices on the slots registering with the dial reading scales.

A particular calculator constructed in accordance with the teaching of this invention will now be described with reference to the accompanying drawing, wherein:

Fig. l is a flat view of one side of the calculator, and

Fig. 2 is an edge view of thecalculator taken along line 22 of Fig. 1.

In the drawing there is shown a plurality of flatdisks ll, [2, l3, l4, and I5, of progressively decreasing diameters, placed-one on top of the others, and pivotally mounted at their centers Each of the disks represents the on the oscillator harmonic, a, involved. The

equations where a equals one are solved on the inner disk 55, with higher harmonics proceeding outwardly to the outer. disk 2%, as indicated by the harmonic numerals l'i, which are marked on a diametral cursor l8 pivoted to the disks by the pin IS.

The visible edge of each of the disks 5 it thru [5 has marked thereon a pair of complementary scales. The other of these scales, for example the scale 2! on the disk H, represents the signal frequency 8, in the above mentioned equations. The inner of the circular scales, for example scale 22 on the disk ii, reading R on the tuning dial of the receiver.

For solving the second of the equations, the cursor I8 is provided with an arcuate slot 23 registering with the scale 2i. At the outer edge of the slot 23 is placed an index in the form of radial, single headed arrow 24. In the opposite radius of the cursor l8 are cut a pair of arcuate slots 25 and 26, each registering with the dial reading scale 22. If desired, the slots 25 and 28 could be joined into a single arcuate slot, this being merely a matter of design appearance. Double indices in the form of single headed arrows 2? 28 are provided at the inner edge of the slots 25 and 26, respectively. The double indices 2? and 28, which register with the dial reading scale 22, are used in cooperation with the single index 24, which registers with the signal frequency scale 2!, to provide a solution for the second equation, for a given oscillator harmonic, in this case the fifth.

In a similar manner the arrows Zia, 21 21c, and EM cooperate with the corresponding arrows of the series represented by the numerals 28 and 24 to give a solution for the fourth, third, second, and first (fundamental) harmonics, respectively, of the oscillator, by cooperating with the respective disks 12, I3, [4, and i5.

Solution of the first equation is efiected in fundamentally the same manner, except that a single index 3| is provided opposite only one of the dial reading scales, namely, the scale for the second harmonic on the disk It. Instead of providing single indices opposite each of the dial reading scales, means are provided for lining up the several disks H thru Hi. This means assumes the form of radial lines 32, marked across the scales of each of the disks. When the radial lines 32 are aligned as shown in'Fig. 1, all of the dial reading scales 22 occupy the same angular position, and the single index 3i may then be used for each of the disks ll thru 15.

To distinguish the indices which solve the second equation from those which solve the first equation, the former are provided with single heads, as mentioned above, while the latter have double heads as seen in the double headed arrow 3!. On the upper radius of the cursor is, each of the slots 2-3 has marked on the edge thereof double indices in the form of pairs of double headed arrows, represented by the arrows 33 and 34, cooperating with the signal frequency scale 2! of the fifth harmonic disk ii. The double headed arrows 33 and 34 cooperate with the double headed arrow 3! in the solution of the first equation, in the same manner as the single headed arrows 2'! and 23 cooperate with the single headed arrow 24 in the solution of the second equation.

The particular computer shown in Fig. 1 is designed for use with a receiver having the properties discussed above; namely, one designed to have the second harmonic of the oscillator mix 30 megacycles below the incoming signal.

Ksgshow'xrin Fig. 2; the calculator may conveniently be made double faced; with the reverse sidesmarked for" use with a receiver-- l'raving different properties than those discussed hereinbef'ore. In this case; the reverse cursor 4i, used with the reverse face; is preferably securedat each end to the obve'se cursor ifi by suitable means such as gimlet eyes 42 Use or the computer A first example of using the computer of the instant invention willgnow'ber described. Assume that responses to a particular signal have been obtained on the" receiver at" the 440 megacycle point, and at the 410 megacycle point. The dial reading scales ofieachcflthedisks H'thru h": are first adjusted by aligning the radial lines 32. Clamping the disks together with. one hand, the operator rotates the cursor l8 until the double headed arrow 3i is opposite the 440 figure on the dial'reading, scale of the disk M, as shown in Fig. l. All"s'ign'als which could'produce this response are then found opposite the ten double headed arrows, exemplified by the numerals 33 and 34. These signals are noted by the operator as:

H5 545 235 I90 380 850 44!! 995 585 L055 The cursor is then turned until the double headed arrow 3| is opposite M9 on the dial reading scale. The ten signal frequencies which could cause this response are then noted as:

I60 600 220 I30 350 190 M0 920 540 980 Comparison of the two lists of signals shows that only one signal frequency, namely 790, is common to the two dial readings. The true frequency of the response is thus found to be 790 megacycles.

Now, assume that it is desired to know all the dial reading points at which responses from the 790 megacycle signal might be detected. Each of the disks I! through 15 is rotated until the several arrows 24 are opposite the 790 point on the signal frequency scales 2|. The inner scale, on disk i5, does not extend as far as 790 megacycles, thereby indicating that the oscillator fundamental can not be brought within 30 megacycles of the incoming signal, and hence cannot produce a response on the receiver dial. The eight responses are found opposite the single headed arrows 21, 21a, 21b, and 210, and the corresponding arrows represented generally by the numeral 28. These responses are found to These are the eight points on the dial where the 790 megacycle signal can be received. Seven of these will be spurious responses, only the 790 reading being genuine.

The frequency separation in megacycles between an upper mixing and a lower mixing for any given harmonic is given by the several lar disks of 6. numerals 44, marked on the cursor l8 adjacent the harmonic dish to which the figure applies.

In determining the true signal frequency from. a set of any two response readings as outlined in the first example above, it is essential that the ngs represent an upper mix i and a lower ng of the with an oscill tor harmonic. If both readings result from an upper mixing or if both readings result from lower mixing, the solution will be ambiguous in that there will be two frequencies appearing in both lists, either of which could have caused that particular set of responses. In this event it is necessary to obtain. further responses to the same signal until a response is obtained which is the result of a that tbeen proi ded a computer whereby the true si type of superheterodyne receiver. It will be understood that various modifications and changes may be made in this invention without departing from the spirit and scope thereof as set forth in the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

l. A calculator comprisin a plurality of members mounted for movement relative to each other, each of said members having a pair of complementary scales marked thereon, and a cursor mounted for movement across members having a series of single indices thereon cooperative, respectively, with the first of each of said pairs of scales, and a series of pairs of indices thereon cooperative with the second of each of said pairs of scales.

2. A calculator comprising a plurality of circu-- progressively decreasing diameters pivotally mounted concentrically for relative rotation each with respect to the others, pairs of circular scales marked adjacent the edges of each disk, a cursor disposed diametrically across the faces of said disks pivotally mounted on the axis of said disks, said cursor having a first series of single indices marked thereon, cooperative with the first of said pairs of scales, and a first series of spaced, double indices marked thereon cooperative with the second of said pairs of scales.

3. A calculator comprising a plurality of circular disks of progressively decreasing diameters pivotally mounted concentrical for relative rotation each with respect to the others, pa'rs of circular scales merited adjacent the edges of each disk, a cursor di posed diametrically across the faces of said disizs pivotally mounted on the axis of said disks, cursor having a first series of single indices marked thereon cooperative with the first of said pairs of scales, a first series of spaced, double indices marked thereon cooperative with the second of said pairs of scales, a second single index marked thereon cooperative with the second of said pairs of scales, a second series of double indices marked thereon cooperative with. the first of said pairs of scales, and radia lines On said disks by means of which said disks be placed in a predetermined relative position.

4. A calculator comprising a plurality of circular disks of progressively decreasing diameters pivotally mounted concentrically for relative rotation each with respect to the others, pairs of circular scales marked adjacent the edges of each disk, a cursor disposed diametrically across the faces of said disks pivotally mounted on the axis of said disks, said cursor having a first plurality of arcuate slots cut therethru on one radius thereof, said slots registering, respectively, with the first of each of said pairs of scales, and a second plurality of arcuate slots cut therethru on the other radius thereof, said last mentioned slots registering, respectively, with the second of each of said pairs of scales, a first series of single indices marked on said cursor at the edges of said first pllu'ality of slots cooperative with the first of said pairs of scales, a first series of spaced double indices marked on said cursor at the edges of said second plurality of slots cooperativewith the second of said pairs of scales, a second, single index marked on said cursor at the edge of one of said second plurality of slots cooperative with the second of said pairs of scales, a second series of spaced double indices marked on said cursor at the edges of said first plurality of slots, cooperative with the first of said pairs of scales, and a series of radial index lines marked across said scales for use in arranging said disks in a predetermined relative position.

WILLIAM T. DOYLE. EARL R. BAKER.

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

UNITED STATES PATENTS Number Name Date 1,429,264 Wright Sept. 19, 1922 1,520,105 Bicknell Dec. 23, 1924 1,780,078 Hite Oct. 28, 1930 2,048,819 Russ July 28, 1936

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