US2148039A - Coupling system for multiple wave band circuits - Google Patents

Description

Feb. 21, 1939. l J, Q RE|D ET AL COUPLING SYSTEM FOR- MULTIPLE WAVE BAND CIRCUITS Bmaentor Feb. 21,1939. J. D, REID ET A. I 2,148,039

COUPLING SYSTEM FOR MULTIPLE WAVE BAND CIRCUITS Filed April 27, 1957 2 Sheets-Sheet 2 Patented Feb. 21, 1939 UNITED STATES PATENT oFFlcr.Y

CUPLING SYSTEM FOR MULTIPLE WAVE BAND CIRCUITS Delaware Application April 27, 1937, Serial No. 139,122

6 Claims.

The present invention relates to multiple wave band receivers, and more particularly to high frequency interstage coupling systems therefor. It has for its primary object to provide an improved interstage coupling system for the high frequency amplifier circuits of a multiple wave band receiver.

It is a further object of the present invention to provide simplified compound coupling means 10 in a system of the above character, wherein two primary windings, resonant at different frequencies, are rendered effective as compound coupling means in conjunction with one or more tuned secondary windings.

It is also a further object of the invention to provide a compound coupling system for the higher frequency tuning bands of a multiple wave band receiver, wherein a low distributed capacity provided by one primary winding may be utilized to tune a second primary winding, whereby said second primary winding may function in two differing wave bands to provide improved energy transfer at the high frequency end of each wave band.

It is also an object of the present invention to provide a high frequency interstage coupling means for wave band change apparatus and the like, wherein two `primary windings are included v in series in the output circuit of an amplier tube and are coupled to two diiiering secondary windings, and wherein the series connection pro-f vides a low distributed capacity of one primary winding in connection with the second primary winding, without requiring the high frequency circuit connections to be broken therebetween in wave band changing.

It is also a still further object of the present invention to provide a switching arrangement for the high frequency tuning bands of a multiple wave band receiver, wherein the secondary windings of adjacent tuning bands are operated in parallel in the highest frequency band, thereby minimizing switching connections.

It is also an object of the invention to simplify the switching arrangement and to provide a more effective energy transfer between primary and secondary circuits for the ultra high frequency tuning ranges of a multiple wave band receiver.

A multiple wave band tuning system to which the coupling system of the present invention particularly relates is shown, described and claimed in an application of John D. Reid, Serial No. 118,631, for Multiple wave band receivers, filed December 31, 1936. The present application relates particularly to the specific circuits and means employed in the C and D bands for resonating the compound primary windings, and the use of the shunt connected compound secondary windings as referred to in that application.

The invention will, however, be better under- 5 stood from the following description, when considered in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings, Figure 1 is a schematic circuit 10 diagram of a radio frequency amplifier switching system embodying the invention, and

Figures 2 and 3 are similar schematic circuit diagrams showing the connections provided by the switching system of Fig. 1 in two high frel5 quency tuning bands.

Referring to Fig. 1, the circuit includes coils 5, ii, 'I, 8, 9 and IIl forming an inductance unit for tuning Lthrough four differing wave bands by means of a common variable tuning capacitor 20 section I I, in connection with the rst detector I2 of a superheterodyne receiver which is arranged Y to receive amplified high frequency signals from a radiofrequency amplifier tube indicated at I3.

The coil' system provides a band tunable or 25 multiple wave coupling means between the radio frequency amplifier tube I3 and the first detector I2, and may be considered as the radio frequency tuning means of the receiver. A separate coil unit comprising a primary winding I4 and a sec- 30 ondary winding I5 is provided for the fifth and highest frequency-tuning range.

The tuning ranges referred to may include such HX, A, HBH, NCH D covering a frequency range in each bandas in- 35 dicated below:

l i Kilocycles X band 410 A band 530- 1800 B band 1800- 6500 40 fC band T A 6500-22000 D band 22000-60000 connections are such that the winding i0 is in- 50A cluded permanently `in theanode circuit I6 of the amplifier I3 adjacent to the anode thereof and is connected in series with the highest frequency band` primary winding I4 through a lead I1. The anode circuit, including the series windings, 55

receives anode potential through a lead |8, the highest inductance winding 5, and a connecting lead I9.

The coils 6 to 9, inclusive, are arranged to form, each in turn, the main secondary windings for the X, A, B and C bands, as indicated by the letters adjacent to the coil sections, and are connected in series, with the winding 9 connected at its high potential end 20 to the grid circuit 2| of the detector |2 and to the stator of the tuning capacitor Coupling with the grid is provided by a coupling capacitor 22 and a grid resistor 23. By this arrangement the tuning capacitor is connected permanently to the high potential terminal of the coil 9 which is the C band secondary, and to the grid circuit of the detector. without switching connections.

The end terminals of the series connected coils or windings and the junctions between the coils are connected to a band change switch section at spaced fixed contacts 25 to 29, inclusive, as indicated. Further spaced fixed contacts are provided on the switch as indicated at 30, 3| and 32. A .grounded capacitor 33 is connected with the switch contact 30 and a series of grounded trimmer capacitors 34, 35, 36 and 3l are connected with the switch contacts 32. The contacts 3| in the switch are not connected in circuit. The low potential terminal 38 of the coil 6 and the contact 25 are coupled to the high potential end of the coil 5 and the lead I9 through a coupling capacitor 39.

The switch is preferably of the rotary type, and is provided, in addition to the xed contacts referred to, with three fixed Contact strips or elongated contact elements 40, 4| and 42, which are located in spaced relation to the fixed contacts to provide the arrangement schematically illustrated, whereby certain bridging connections may be made between the fixed contacts by three movable contact elements in a series of steps. The first is a bridging contact 43 which is movable along the grounded contact 4|, to provide a bridging ground connection with the fixed contacts 25 to 28, progressively to the C band position shown, wherein the low frequency endof the C band coil or secondary 9 and the adjacent terminal end of the B band coil 8 are` connected to ground. In the next position, for the D band, bridging connection is made between the contact 40 and the contact 29 to connect the D band secondary I5 in parallel with the secondary 9.

'I'he second movable bridging contact element is indicated at -45 and, in the C band position shown, provides a bridging connection between the terminal 29 and one of the terminals 32, for connecting the trimmer capacitor 34 in parallel with the secondary coil 9 to adjust the tuning at the high frequency yend of the C band.

The third movable connection comprises a bridging element v47, for short circuiting the coils 6 and 1, whereby they are ineffective to absorb energy or to resonate in the "C band tuning range, and for bridging the terminals 30 and 42, whereby the capacitor 33 is connected substantially in shunt with the coil 8 to provide proper response in the C band as the low frequency pr"- mary of a compound coupling for the plate circuit I6 of the radio frequency amplifier |3 and the C band secondary coil 9, as will hereinafter be described. The contact 42 is also connected to the anode circuit between the coils |0 and. |4 with the lead through a bypass capacitor 48 and a lead 49, whereby the series anode circuit connection, including the primary I4 for the D band,

is bypassed to place the winding 8 or B band secondary in series with the winding |0. The latter is in inductive coupling relation to the secondary 9 and provides a high frequency primary in conjunction with the winding 8 as the low frequency primary for the C band tuning range.

The switch connections established for the C band tuning are indicated more clearly in Fig. 2 in which the same reference characters are applied to like parts, as in Fig, 1.

Referring to Fig. 2, along with Fig. 1, the C band primary circuit outlined is also connected with a shunt path through the coil I4, the lead I9 and the capacitor 39. This path has a relatively high impedance, as the X band primary coil 5 is of relatively high inductance and is in series with the primary coil |4 which also has an appreciable inductance effective in the C band range. In the main primary circuit, the bypass capacitor 48 is of relatively high capacity and low reactance; for example, it may have a capacity value of .01 microfarad. Therefore, the desired primary circuit is obtained for the windings |0 and 8 without additional switching contacts to make and break additional circuits.

The plate capacity of the R. F. amplifier tube |3 and other stray distributed anode circuit capacity is indicated at 5|. The trimmer capacitor 33 is connected in shunt with the coil 8 as the low frequency primary and is preferably tuned to substantially 4800 kc. for the C band covering a range of 6500 to 22,000 kc., as indicated. The low frequency primary is therefore resonated below the tuning range of the secondary 9.

The distributed capacity 5| is in series with the capacity value provided by the capacitor 33, and since the latter is relatively high with respect to the plate capacity 5|, the plate capacity 5| is effectively connected in shunt relation to the high frequency primary winding l0 and serves to tune it, in the present example, to substantially 40,000 kcs., which is above the C band tuning range.

The use of a compound coupling of this type is effective to increase the gain through the coupling circuit at both ends of the tuning range, since the high frequency and the low frequency responseof the primary windings 8 and l0 is effective to raise the overall response of the coupling system ends of the tuning range.

It has been found that at least one of the primary windings may be maintained in circuit and utilized in at least two higher frequency tuning bands without switching. It has been found also that that high frequency primary winding |0 is best adapted for this use, and therefore is maintained in circuit adjacent to the anode for both the C and D bands. The D band is higher in frequency, and in order to resonate the high frequency primary I0 above the D band, a differing capacity is provided in series with it and is provided by a suitable low frequency primary such as the primary winding 4 which is caused to be effective for the D band, in the series anode circuit, by a simple switching operation involving only opening the connection through the bypass capacitor 48 and short circuiting the low frequency primary for the C band, coil 8 to provide the circuit shown in Fig. 3, to which reference may be made along with Figs. 1 and 2. Except for the circuit connection change for the D band, tuning the circuit is the same as shown in Fig. 3 and the same reference numerals are applied.

The low frequency primary coil 4 for the D band is provided with a Yrelatively low distributed capacity and is tunable thereby to substantially 1900 kcs. or below the D band, and the low distributed capacity then becomes the controlling capacity in tuning the high frequency primary I0, since the low distributed capacity of the coil I4 is lower than the tube capacity 5 I with which it is effectively in series. The high frequency primary III operates in both the C and the D bands, resonating at a frequency above the C band in series with the primary 8 and its shunt capacity 33, and as shown in Fig, 3 it resonates at a still higher frequency above the D band when placed in series with the low distributed capacity of the primary coil I4. In the present example the distributed capacity of the coil I 4 is sufficient to tune the coil I to substantially 90,000 kcs. or well above the D band which covers the range of 22,000 t0 60,000 kCS.

In the circuit of Fig. 3, the winding 5 is effective as a choke coil, as in the C band. Howeventhe bypass capacitor 39, while offering appreciable impedance at 4800 kos., is of relatively low impedance at 19,000 kcs and serves as part of the low impedance path to ground from the lead I9, as indicated.

By comparing the circuits in Fig. 1 and Fig. 3, it will be seen that the two secondary windings I5 and 9 are connected in parallel when the conductor i3 reaches the contacts 29 and 40. The conductor d1 grounds the contact 28 and also the contacts 25, Z6 and 21.

Since the coil 9 is of relatively high inductance with respect to the coil I5, parallel operation in the D band has been found to be permissible and at the same time permits compound coupling whereby energy is supplied from the primary winding I0 to the coil 9 and from the coil I4 to the coil I5 for the D band operation. By this arrangement the tuning capacitor I I and the tube input circuit ZI may be maintained permanently connected with the major portion of the tuning inductance unit and likewise necessity for switching the high frequency primary l0 is eliminated.

` This winding is closely associated with the winding 0 and remains in circuit throughout the switching operations for the various bands, thus preventing change in distributed capacity at the sensitive high frequency end of the tuned circuit.

While the coupling system of the present invention has been shown and described in its application to a radio frequency amplifier stage in the C and D band ranges, it may be provided in other multiple wave band apparatus between ultra high frequency circuits in a similar manner and in other high frequency and ultra high frequency tuning ranges.

We claim as our invention:

1. In a tunable high frequency multiple wave band amplifier, the combination of means providing compound inductive interstage coupling between certain of the signal conveying circuits thereofand including a coupling winding having low distributed capacity and resonant at a frequency below a predetermined tuning band, a second coupling winding, and means for connecting said windings effectively in series whereby the distributed capacity of the first winding is effective to tune the second coupling winding to a frequency above said tuning band,

2. In a high frequency multiple wave band amplifier, the combination of two signal circuits, means providing compound inductive coupling between said circuits including two coupling windings connected in series in one circuit and resonant at different frequencies, a third coupling winding having a low distributed capacity, and means for selectively connecting said third winding in series with one of said first-named windings to the exclusion of the other whereby said distributed capacity is effective to resonate said one winding to a higher frequency.

3. In a high frequency interstage coupling system for multiple wave band amplifiers and the like, the combination of two primary windings, resonant at different frequencies above and below a predetermined wave band, a secondary winding tunable through said wave band and coupled to receive signal energy from said high and low frequency primary windings jointly, and means for resonating the high frequency primary winding at a frequency above a predetermined higher frequency tuning band comprising a second low frequency primary winding, said second low frequency primary winding having a low distributed capacity effective to resonate said high frequency primary winding above said higher frequency tuning band.

4. In a high frequency interstage coupling system for multiple wave band amplifiers and the like, the combination of two primary windings, resonant at different frequencies above and below a predetermined wave band, a secondary winding tunable through said wave band and coupled to receive signal energy from said `high and low frequency primary windings jointly, and means for resonating the high frequency primary winding at a frequency above a predetermined higher frequency band comprising a second low frequency primary winding resonant below said higher frequency band and connected in series with said high frequency primary winding, said second low frequency primary winding having a low distributed capacity effective to resonate said high frequency primary winding above said higher frequency band, a higher frequency Secondary winding tunable through said higher frequency band coupled with said second low frequency primary to receive signal energy therefrom, and switching means for rendering the rst low frequency primary ineffective as a coupling means and for connecting said secondary windings in parallel.

5. In a multiple Wave band receiver, the combination with a radio frequency amplifier, of an interstage tunable coupling means therefor comprising an output anode circuit for said amplier, a primary winding permanently connected in circuit therewith at the high potential end of the anode circuit to provide a high frequency primary winding for said interstage coupling means, a pair of low frequency primary windings, and means for selectively connecting said lastnamed windings serially in circuit with the `firstnamed winding and the anode capacity of said tube, the distributed capacity of one of said second-named primary windings being of a value lower than the anode capacity and effective to tune the high frequency primary winding to a predetermined high frequency when connected in circuit therewith.

6. In a multiple wave band receiver, a combination with the radio frequency amplifier, of an interstage tunable coupling means therefor comprising an output anode circuit for said amplifier, a primary winding permanently connected in circuit therewith at the high potential end of the anode circuit to provide a high frequency primary winding for said interstage coupling means, a pair of low frequency primary windings, and means for selectively connecting said lastnamed windings serially in circuit with the vfirstnamed winding and the anode capacity of said tube, the distributed capacity of one of said second-named primary windings being of a value lower than said anode capacity and effective to tune the high frequency primary winding to a predetermined high frequency when connected in circuit therewith, a pair of secondary windings one coupled with each of said low frequency and high frequency primary windings, a second tube having a grid circuit, a variable tuning capacitor, circuit means permanently connecting said capacitor and grid circuit with one of said secondary windings, and means for connecting said secondary windings in parallel conjointly operable with said first-named selecting means.

JOHN D. REID.

LOREN R. KIRKWOOD.

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