US3544903A

US3544903A - Variable inductor band changing for vhf-uhf tuner

Info

Publication number: US3544903A
Application number: US662916A
Authority: US
Inventors: Yoishi Sakamoto
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1966-08-30
Filing date: 1967-08-24
Publication date: 1970-12-01
Anticipated expiration: 1987-12-01
Also published as: NL6711910A; DE1791256A1; DE1791255C3; DE1791256C3; DE1791256B2; DE1791255B2; NL151864B; GB1201385A; DE1791255A1

Description

VARIABLE INDUCTOR BAND CHANGING FOR VHF-UHF TUNER Filed Aug. 24. 1967 YOICHI SAKAMOTO l0 Sheets-Sheet 1 Dec. 1, 1970 3 m 0 LP, Wa I WIT M 1 .ill:ll w v| Tm wt" w 4 n gt T SW1 ..n k m m a L mm m J w VIIIHHHUHUIIIIIIIIIHHHIIIM q 2 5 25 m F0 .3. w m 1/ I. 5/ E! r. wlwl 3 6 J 3% M ;W L 7 2 i. U 9.. w

INVENTOR yOIcHI Jmm/wm ATTORNEYS 1970 YOICHI SAKAMOTO 3,544,9031

VARIABLE INDUCTOR BAND CHANGING FOR VHF-UHF TUNER l0 Sheets-Sheet 2 Filed Aug. 24, 1967 I NVENTOR yOI CHI JHAAIIDTO ATTORNEYS 1970 YOICHI SAKAMOTO 3,

VARIABLE INDUCTOR 'BAND CHANGING FOR VHF-UHF TUNER Filed Aug. 24, 1967 10 Sheets-Sheet 5 /0 Y I EVE/EEAPPL/ED VOLTAGE w 2 MUQEBWQVG FIG 4 INVENTOR YDICH/ JAKRNOTO 5; m5 [Cy L14. e %Ww ATTORNEYS 1970 YOICHI SAKAMOTO 3,544,903

VARIABLE INDUCTOR BAND CHANGING FOR VHF-UHF TUNER Filed Aug. 24, 1967 10 Sheets-Sheet 4.

FREULE AMPL/F/ER FREQUENCY-- INVENTOR yolcm mm/10m ATTORNEYS 1 YOICHI SAKAMOTO 3,54

VARIABLE INDUCTOR BAND CHANGING FOR VHF-UHF TUNER Filed Aug. 24, 1967 10 Sheets-Sheet 6 INVENTOR yolol-ll .m lfH/ID r0 ATTORNEY S I970 YOICHI SAKAMOTO 3,54

VARIABLE INDUCTOR BAND CHANGING FOR VHF-UHF TUNER Filed Aug. 24, 1967 10' Sheets-Sheet 7 TUNER INVENTOR y fil JHKHHDTO OJ. m BY Maw 521E ATTORNEYS 1970 YOICHI SAKAMOTO ,9 3

VARIABLE INDUCTOR BAND CHANGING FOR VHF'UHF TUNER i0 Sheets-Sheet 8 Filed Aug. 24, 1967 INVENTOR 1970 YOICHI SAKAMOTO 3,544,903

VARIABLE INDUGTOR BAND CHA NGING FOR VHF-UHF TUNER Filed 1967 1o Sheets-Sheet 1o "F/G. 20 H FIG 2/ 6 m q A Q h R \1 \m k 85 b 35% 1 m I '5 W Q 1% //VTERMED/ATE g ED/A7E FREQUE/VcY g Qg FREQ/ENC) Q 91 E 8 P76. 22

A OFF OFF 4 OFF 19mm 1 I I z i i I: i //vTER/vE0/ATE mum 1mm mum 1mm! IHHH gfigg f l E OUTPUTOF 6 W WWW E 2 i OUTPUT 0 1 1 SWEEP C/RCU/T I 1 I D 2 INVENTOR 'ymcm Jmmnmo ATTORNEYS United States Patent 3,544,903 VARIABLE INDUCTOR BAND CHANGING FOR V TUNER Yoishi Sakamoto, Toyonaka-shi, Japan, assignor to Matsushita Electric Industrial Co., Ltd., Osaka, Japan, a corporation of Japan Filed Aug. 24, 1967, Ser. No. 662,916 Claims priority, application Japan, Aug. 30, 1966, 41/57,750; Sept. 2, 1966, 41/58,426; Dec. 28, 1966, 42/247; Jan. 19, 1967, 42/4,284; Jan. 26, 1967, 42/5,527; Jan. 27, 1967, 42/11,507; Mar. 1, 1967, 42/115,530; Apr. 14, 1967, 42/24,128

Int. Cl. H03j 5/02 US. Cl. 325-459 5 Claims ABSTRACT OF THE DISCLOSURE A tuner using variable capacitance diodes as elements for changing the tuning and oscillation and which is adapted to effect the desired selection of television broadcast by applying different voltages to the variable capacitance diodes.

This invention relates to a tuner for television use.

The television tuners presently available are so designed as to effect channel selection by switching channel selecting coils corresponding to the frequencies assigned to respective broadcasting stations by means of a turret switch or disk turret switch. In this case, it goes without saying that the number of the band selecting coils to be provided in a television receiver should be at least equal to that of the broadcasting stations. Besides, it is also required that such coils be incorporated in the tuning circuit, local oscillator circuit, etc. of such receiver. Therefore, the number of contacts needed to switch these coils becomes as large as 50 to 100. Inevitably, this limits the life of such contact portions in spite of a careful design and fabrication of the latter. At present, a majority of trouble of a television receiver is that of the tuner due to malfunction of such contacts.

In view of this, an attempt has been made to improve the performance of such tuner through the use of contacts formed of a precious metal which is relatively free from abrasion. However, it would be impossible to completely eliminate the trouble of a tuner without resorting to means for basically solving the contact problem.

In the tuner circuit according to the present invention, variable capacitance diodes of which the capacitance is varied by changing a voltage applied thereto are used as tuning and oscillation variable elements of such circuit.

Thus, the most important object of this invention is to provide an arrangement capable of receiving any desired television broadcast by changing a voltage applied to the variable capacitance diodes.

The ratio of the minimum frequency to the maximum frequency used in television broadcast is 90:222 in the Japanese system and 542216 in the United States system. Therefore, if it is desired to receive the over-all television broadcast frequency hand through variations in capacitance of variable capacitance diodes alone, then the ratio of the miminum capacitance to the maximum capacitance of such a diode becomes 1/90 :1/222 1:1/6.1 in

3,544,903 Patented Dec. 1, 1970 ice the Japanese system and 1/54 :1/216 1:1/16 in the US. system, since the resonance frequency is defined by zwfd (1 and the following relation is derived therefrom Japanese system:

Channels 1 to 3, mc. to 108 mc.; Lower band Channels 4 to 12, me. to 222 mc.; Higher band American system:

Channels 2 to 6, 54 mc. to 88 mc.; Lower band Channels 7 to 13, 174 mc. to 216 mc.; Higher band Then, the ratios of the maximum to the minimum capacitance of a variable capacitance diode become as follows:

Japanese system:

Lower band; 1/90 :1/108 1:1/1.44 Higher band; 1/170 :1/222 1:1/1.7 American system:

Lower band; 1/54 :1/88 l:/2.65 Higher band; 1/174 :1/126 1:1/1.54

These values may be readily be attained.

In accordance with an object of this invention, therefore, variable capacitance diodes are used as tuning and oscillation variable elements of the tuner circuit, and the lower band of the entire television broadcast frequency band, for example, is received by changing a voltage applied to the variable capacitance diodes and when a channel within the higher band is to be selected, the inductances of coils constituting the tuning and oscillator circuits of the tuner circuit together with said variable capacitance diodes are electrically changed to select any desired channel within the higher band, thereby making it possible to selectively receive all the television broadcast.

Other objects, features and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings.

FIG. 1 is a circuit diagram illustrating the tuner circuit according to an embodiment of this invention;

FIG. 2 is a circuit diagram showing the tuner circuit according to a second embodiment of this invention;

FIG. 3 is a circuit diagram showing the tuner circuit according to a third embodiment of this invention;

FIG. 4 is a view illustrating the voltage-current characteristic of a variable capacitance diode;

FIG. 5 is a circuit diagram showing the tuner circuit according to a fourth embodiment of this invention;

FIG. 6 is a view illustrating the relations between reverse applied voltage and capacitance of a variable capacitance diode;

FIG. 9 is a view illustrating the discriminating action;

FIG. 10 is a circuit diagram showing the tuner circuit according to a further embodiment of this invention;

FIG. 11 is a circuit diagram showing a further embodiment wherein the tuner circuit is divided into a higher band tuner and a lower band tuner;

FIGS. 12a and 12b are frequency characteristic diagrams for explaining the operation of the tuner circuit of FIG. 10;

FIG. 13 is a view showing the frequency vs. reactance characteristic of the circuit 704 shown in FIG. 11;

FIG. 14 is a view showing the frequency vs. reactance characteristic of the circuit 704" shown in FIG. 11;

FIG. 15 is a circuit diagram illustrating still another embodiment of this invention;

FIG. 16 is a schematic circuit diagram showing an example of high frequency tuning circuit incorporated in the conventional selecting circuit;

FIGS. 17 and 18 show the high frequency tuning circuits according to this invention;

FIG. 19 shows a still further embodiment of this invention;

FIG. 20 shows the intermediate frequency vs. output voltage characteristic of the frequency discriminator circuit incorporated in the arrangement of FIG. 19;

FIG. 21 illustrates the characteristic of the intermediate frequency amplifier provided in the arrangement of FIG. 19; and

FIG. 22 is a view illustrating the operation of the circuit as shown in FIG. 19.

Referring to FIG. 1 of the drawings, the reference numeral 12 represents an input terminal, and 13 a tuning coil wound on a magnetic core which is magnetized by a D.C. current. The coil 13 constitutes, together with a variable capacitance diode 14, a single-resonance circuit of which the output is applied to an amplifier transistor 16 through a capacitor 15. Between the collector and the emitter of the amplifier transistor 16 is provided a doubletuning circuit consisting of coils 17 and 18 similar to the coil 13 and

variable capacitance diodes

19 and 20. The output of the double-tuning circuit is applied to a mixer transistor 21 to which is simultaneously supplied the output of a local oscillator circuit 22. Thus, a video intermediate frequency signal is obtained at the collector of the transistor 21.

The reference numeral 23 denotes a variable power source which is connected with a variable capacitance diode 28 of the local oscillator circuit 22 and said

variable capacitance diodes

20, 19 and 14 through resistors 24, 25, 26 and 27, respectively.

A power source 30 is connected with the

respective coils

13, 17 and 18 and a similar coil 29 of the local oscillator circuit through a switch 31 by which the power source is turned on and off.

Capacitors 32, 33, 34, 35, 36, 37 and 38 and coils 39, 40, 41 and 42 serve to electrically isolate the

respective coils

13, 17, 18 and 29 from each other.

Description will now be made of the operation of the circuit as illustrated in FIG. 1. When the switch 31 is opened, no power is supplied to the

respective coils

13, 17, 18 and 29, so that each of these coils will have a high impedance because of its high permeability with a result that the circuit becomes ready for operation in the lower band. In such a state, if a signal arrives at the input terminal, it will be single-tuned by means of the coil 13 and the variable capacitance diode 14, and then the resultant tuned frequency signal will be amplified by the transistor 16 of which the output will in turn be doubletuned by means of the double-tuning circuit so as to be supplied to the mixer transistor 21. At the sametime, the output of the local oscillator circuit will be supplied to the base of said mixer transistor 21. Thus, a video intermediate frequency signal will be obtained at the collector of the transistor 21.

By changing the voltage of the power source 23 to change the capacitance of each

variable capacitance diode

14, 19, 20 and 28, the tuned frequencies of the singletuning circuit and double-tuning circuit and the frequency of oscillation of the local oscillator circuit 22 are correspondingly changed, so that the selection within the lower band becomes possible.

Closing the switch 31 for the power source 30 causes an energizing current to flow through each of the

coils

13, 17, 18 and 29 so that these coils are magnetized in accordance with the fiat portion of the BH curve, with a result that the values of ,u. of these coils and, hence, their impedances are decreased. This results in the selection of the higher band. By changing the voltage of the power source 23 to change the capacitances of the variable capacitance diodes, it is possible to achieve the selection within the higher band.

As described above, the switching operation for the higher and lower bands is current-wise effected by virtue of the non-linearity of magnetization of a magnetic material provided in the tuning and oscillation coils, and the selection within each band is voltage-wise efiected by means of the variable capacitance diodes for the purpose of electrically selecting a desired channel. Thus, the band switching operation between the higher and lower bands can be performed by applying or interrupting a D.C. magnetic field to a core formed of a magnetic material with a remarkable non-linearity of magnetization to change the permeability ,u. of the core and thereby change the inductance of the coil.

In FIG. 2 there is illustrated another embodiment of this invention wherein the band switching operation between the higher and lower bands is effected through displacement of a magnetic material such as high frequency ferrite or the like. The tuner circuit comprises a tuning circuit 101, a double-tuning circuit 102 and a local oscillator circuit 121. The circuit 101 includes a series connectron of two

coils

107 and 108 and a variable capacitance diode 103 connected thereacross. The circuit 102 contains a series connection of two coils 109 and 110 and a variable capacitance diode 104 connected thereacross, and a series connection of coils 111 and 112 and a variable capacitance diode 105 connected thereacross. The circuit 103 comprises a series connection of coils 113 and 114 and a variable capacitance diode 106 connected thereacross. Magnetic members 115 are associated with the

COllS

108, 110, 112 and 114 through a cam or plunger mechanism, respectively. If the magnetic members 115 are inserted into or placed close to the

coils

108, 110, 112 and 114, the inductance of each coil is increased to a value suitable for selection of the lower band, while if the magnetic members 115 are retracted or spaced apart from the

coils

108, 110, 112 and 114, the inductance of each coil is decreased to a value suitable for selection of the higher band. Thus, the band switching operation between the higher and lower bands can readily be performed. By applying a voltage different from a power source to the variable capacitance diodes 103, 104, 105 and 106 through

resistors

116, 117, 118 and 119, respectively, it is possible to achieve the selection within each band.

FIG. 3 shows the case where coils forming the tuning circuit and oscillator circuit of the tuner circuit together with variable capacitance diodes are divided into two portions, a diode is coupled to the intermediate point between the two divided portions of each coil, and one of the divided portions of each coil is connected and disconnected through the associated diode, thereby effecting the band switching operation between the higher and lower band. Detailed explanation will now be made with reference to FIG. 3, wherein the reference numeral 201 represents a high frequency tuned amplifier circuit, 202 a double-tuning circuit, 203 a local oscillator circuit and 204 a mixer circuit. The output of the high frequency tuned amplifier circuit 201 is applied to the double-tuning circuit 202 the output of which is in turn mixed with the output of the local oscillator circuit in the mixer circuit 204 so that an intermediate frequency signal is produced.

The

reference numerals

205, 206 and 207 represent transistors constituting the high frequency tuned amplifier circuit 201, mixer circuit 204 and local oscillator circuit 203, respectively. The

reference numerals

208, 209, 210 and 211 denote variable capacitance diodes connected in the

respective circuits

201, 202 and 203 and the

variable capacitance diodes

208, 209, 210 and 211 constitute tuning circuits or LC oscillator circuits together with

inductors

213 and 214, 215 and 216, 217 and 218 and 219 and 220.

Thus, by changing the value of a power source 12 applied to the variable capacitance diodes 208, 209 210 and 211, the capacitance of each of these diodes is changed, so that the receiving condition of each circuit is varied.

Diodes

221, 222, 223 and 224 have their cathodes grounded and their anodes connected with

power source

226 or 227 through the connection points of the

inductors

213 and 214, 215 and 216, 217 and 218 and 219 and 220 of the

circuits

201, 202 and 203 and a switch 225 respectively. Normally, it is possible to construct a circuit which is adapted for conduction or non-conduction by applying a positive or negative voltage across the terminals of a diode. Assume that a channel in the higher band is desired to be received. By bringing the movable contact of the switch 225 into engagement with the contact a, a DC. current is caused to flow through each of the

diodes

221, 222, 223 and 224. Thus, suitable selection of the values of

resistors

227, 228, 229 and 230 causes the value of dV/dl to be close to zero at the operating point of each of the

diodes

221, 222, 223, 224 as illustrated in FIG. 4, with the result that these diodes become conductive so as to cause the ends of

coils

213, 215, 217 and 219 to be grounded. From this, it will be noted that in an attempt to receive a channel within the higher band, the

inductors

213, 215, 217 and 219 are used while the

other inductors

214, 216, 218 and 220 are shorted so that the latter inductors appear as if they were absent. In this way, any channel within the higher bands can be selected by changing the voltage of a variable voltage source 212 while the switch 225 is being engaged with the contact a.

In order to receive a channel within the lower band, the switch 225 is switched to the contact b so that a negative voltage is applied to the cathodes of the

diodes

221, 222, 223 and 224. This substantially prevents a current flow through the

diodes

221, 222, 223 and 224 and thus a voltage substantially equal to that of the power source 227 is applied to these diodes so that the diodes become non-conductive but they have a slight barrier capacitance, which is substantially negligible. Hence, the tuning in ductances of the high frequency amplifier circuit 201, tuning circuit portion 309, interstate tuning circuit porresented by the sum of the inductance of the inductors 213 and 214, that of 215 and 216, that of 217 and 218 and that of 219 and 220, respectively. In such a state, any channel within the lower band can be selected by changing the voltage of the variable voltage source 212.

FIG. illustrates a further embodiment of this invention which is adapted for switching the higher and lower bands. Description will now be made of the embodiment shown in this figure, wherein the

reference numerals

301, 302, and 303 denote a high frequency amplifier transistor, mixer transistor and a local oscillator transistor, respectively, and the

reference numerals

304, 305, 306 and 307 represent channel selecting variable capacitance diodes provided in an input tuning circuit portion 308, inter-stage tuning circuit portion 309, interstate tuning circuit portion 310 and local oscillator circuit, respectively. The inductance element portion of said input tuning circuit 308 is composed of a series connection of coils 308a and 308b. Similarly, the inductance element portion of the interstage tuning circuit portion 309 is formed by a series connection of coils 309a and 30% that of the inter-stage tuning circuit portion 310 by a series connection of coils 310a and 310b, and that of the local oscillator circuit portion 311 by a series connection of coils 311a and 311b. The

reference numerals

312, 313, 314 and 315 represent band switching variable capacitance diodes connected in parallel with said coils 3081), 309b, 3101; and 311b, respectively. A voltage E of a DC. voltage source 317 and a voltage E of a DC. voltage source 318 superimposed upon the voltage E are selectively applied to the

diodes

312, 313, 314 and 315 as reverse voltage through a band change-over switch 316.

The reference numeral 319 denotes a variable DC voltage source to apply a desired reverse voltage to said channel selecting variable capacitance diodes to achieve channel selection.

The characters X, Y and Z in FIG. 6 show three different types of dependence of barrier capacitance upon applied voltage of a variable capacitance diode as a reverse voltage is applied thereto. The variable capacitance diodes utilized in this invention may take any one of these three types of characteristic.

Description will now be made of the channel selecting operation. Assume that a channel within the lower band is to be received. Then, the switch 316 is switched to the contact a, so that a high reverse voltage of (EH-E is applied to the

variable capacitance diodes

312, 313, 314 and 315, with the result that their barrier capacitances are greatly decreased. If the value of (E +E is previously adjusted so that each of such barrier capacitances represents a minimum value, the parallel impedance circuits formed by the variable capacitance diode 312 and coil 308b variable capacitance diode 313 and coil 30% variable capacitance diode 314 and coil 310b, and variable capacitance diode 315 and coil 311b are regarded as being inductive. Since these parallel impedance circuits are connected in series with the coils 308a, 309a, 310a and 311a (it is assumed that their inductance values are L L L and L respectively), the tuning inductance values of the input tuning circuit portion 308, inter-stage tuning cir cuit portion 309, inter-stage tuning circuit portion 310 and local oscillator circuit portion 311 become approximately L +L L -i-L L +L and L +L respectively, where L L L and L are the inductance values of the coils 308b, 3091), 31011 and 311b. Thus, the tuning inductances assume values suitable for the operation within the lower band. In such a state, therefore, desired channel selection can be achieved by changing the voltage of the DC. volt age source 319 to change the reverse voltage applied to the

variable capacitance diodes

304, 305, 306 and 307, so that any desired channel within the lower band can be received.

In an attempt to receive a channel within the higher band, the switch 316 is switched to the contact b, so that only a low reverse voltage E from the DC. voltage source 317 is applied to the

variable capacitance diodes

312, 313, 314 and 315. As a result, the barrier capacitances of these diodes are greatly increased. In this case, if the voltage E is adjusted so that each of such barrier capacitances represent amaximurn value, the parallel impedance circuits formed respectively by the variable capacitance diode 312 and coil 308b, variable capacitance diode 313 and coil 30%, variable capacitance diode 314 and coil 31011, and variable capacitance diode 315 and coil 311b become capacitive, and the tuning inductances in the input tuning circuit portion 308, inter-stage tuning circuit portion 309', inter-stage tuning circuit portion 310 and local oscillator circuit portion 311 become substantially equal to the inductances L L L and L, of the coils 308a, 309a, 310a and 311a, respectively. Thus the tuning inductances assume values suitable for the operation within the higher band.

In such a state, therefore, channel selection can be achieved by changing the voltage of DC. voltage source 319 so as to change the reverse voltage applied to the

variable capacitance diodes

304, 305, 306 and 307, so that any desired channel within the higher band can be received.

Although, in the embodiment of FIG. 5, the mechanical switch 316 was used as means for switching the reverse voltage applied to the

variable capacitance diodes

312, 313, 314 and 315, use may equally be made of an electronic switch such as gate circuit. Furthermore, the DC. voltage applied to the

variable capacitance diodes

304, 305, 306 and 307 may be a voltage divided by means of a potentiometer or a sweep voltage such as saw-tooth voltage. Obviously, the inter-stages may be single-tuning circuits rather than double-tuning circuits, and the active elements maybe vacuum tubes rather than transistors.

In the foregoing, description has been made of the embodiments adapted for switching the higher and lower bands. In this case, a variation in the control voltage applied to the variable capacitance diodes inevitably leads to a drift in the frequency of local oscillation. Furthermore, variations in the capacitance of such diodes with temperature cannot be neglected. This makes it impossible to achieve perfect selection of a desired channel. In order to achieve such perfect selection, therefore, the control voltage applied to the variable capacitance diodes should be automatically controlled to an optimum value.

FIG. 7 shows a circuit diagram of a channel selecting device using variable capacitance diodes as tuning changing elements. In this figure, the reference numeral 401 indicates a high frequency amplifier circuit, 402 a doubletuning circuit, 403 a mixer circuit, and 404 a local oscillator circuit.

The

reference numerals

405, 406 and 407 represent a high frequency amplifier transistor, a mixer transistor and a local oscillator transistor, respectively, and the

reference numerals

408, 409, 410 and 4.11 denote variable capacitance diodes serving as channel selection changing elements included in the respective circuits above, respectively.

The reference numeral 412 represents a power source for applying a voltage to the

variable capacitance diodes

408, 409, 410 and 411.

The reference numeral 413 denotes a constant voltage diode, 414 a temperature-dependent resistor for compensating for the temperature characteristics of the variable capacitance diodes, and 415 a control voltage circuit for applying a different voltage to the respective

variable capacitance diodes

408, 409, 410 and 411 depending upon the channel to be selected. By turning on and off switches S to S the voltage applied to the

variable capacitance diodes

408, 409, 410 and 411 is varied to change the capacitances of these diodes so that any desired channel can be selected.

Thus, any variations in voltage of the power source 412 and in capacitance of the variable capacitance diodes with temperature can be compensated by means of the constant voltage diode 413 and temperature-dependent resistor 414, so that a fairly suitable voltage can be applied to the

variable capacitance diodes

408, 409, 410 and 411. However, perfect correction cannot be effected due to aging of each component, influence of temperature characteristics, changes in temperature characteristics of capacitance of the variable capacitance diodes depending upon applied voltage, and the like. Thus, an accurate voltage can hardly be applied to the variable capacitance diodes, which makes it difficult to achieve accurate selection of a desired channel.

FIG. 8 shows an arrangement adapted for eliminating the afore-mentioned drawbacks. First, description will be made of the point where the arrangement of FIG. 8 differs from that of FIG. 7. The circuit of FIG. 8 is characterized in that a frequency discriminator 517 is inserted between the output terminal 518 of an intermediate frequency amplifier 516 connected with the output terminal of a mixer circuit 503 and the connection point between a variable capacitance diode 511 and a resistor 519 connected in series with each other.

Thus, an intermediate frequency signal taken out of the mixer circuit 503 is amplified in the intermediate frequency amplifier 516 and part of the output of the amplifier is supplied to the frequency discriminator 517.

A control voltage represented by a curve a of FIG. 9 is applied in suitable polarity from the frequency discriminator 517 to the connection point between the variable capacitance diode 511 and the resistor 519.

On the other hand, the frequency of oscillation of the local oscillator circuit is controlled in accordance with such a characteristic as represented by a curve 11 of FIG. 9. Thus, the automatic control loop becomes stable at the intersection between the curves a and b or at the frequency indicated by A, so that normal video and sound broadcast can be received.

Further description will now be made of the operation of the circuit as shown in FIG. 8. If it is desired to receive a certain channel, one of the switches S to S of the voltage control circuit (potentiometer) 515 is turned on so that a control voltage most suitable for the reception of said certain channel is applied to the respective variable capacitance diodes 508, 509, 510 and 511 thus achieving the selection of the desired channel.

Even if the voltage of the power source 512 is changed, suitable reception can equally be achieved.

That is, if the voltage of the power source is decreased, the voltage applied to the respective variable capacitance diodes is correspondingly decreased, so that the capacitance of, for example, the variable capacitance diode 511 is increased to cause the frequency of oscillation to be decreased.

Such decrease in the frequency of the local oscillation leads to decrease in the intermediate frequency so that the output frequency of the intermediate frequency amplifier 516 is likewise decreased, with the result that an input frequency fed back to the frequency discriminator 517 is also decreased.

Consequently, the output voltage of the discriminator 517 is decreased, as illustrated in FIG. 9.. With such decrease in the output of the frequency discriminator 517, the voltage applied to the variable capacitance diode 511 is increased.

The increase in the applied voltage leads to decrease in the capacitance of the variable capacitance diode 511, thus increasing the frequency of local oscillation to a predetermined constant value.

In this way, variations in the voltage of the power source can be compensated.

FIG. 10 shows an arrangement in which no frequency discriminator circuit described above is provided and a control voltage for fine adjustment is applied directly from a part of an audio intermediate frequency amplifier 618 to the variable capacitance diode of the local oscillator circuit. The video IF amplifier circuit 616 is so designed as to have a frequency response shown in FIG. 12a, where the abscissa and the ordinate represent frequency and reciprocal of the amplification degree. A portion of the video IF amplifier circuit 616 is then fed to the junction 620 between the variable capacitance diode 611 via the audio IF amplifier circuit 618. The diode 611 constitutes the resonant element of the local oscillator circuit 604. Due to the frequency characteristics of the video IF amplifier circuit 616 as shown in FIG. 12a, the input control voltage to the junction 620 is such as is shown by a curve a in FIG. 1211. Meanwhile, characteristic line b of FIG. 12b represents the output of the local oscillator circuit 604 with respect to the oscillation frequency of the circuit, so that at the intersection point A between the curve a and line b the operation of the local oscillator circuit 604 is stabilized. Thus, a similar effect can be produced without providing any frequency discriminator circuit described above.

In FIG. 11, there is shown an arrangement in which the tuner circuit is divided into two sections, or a higher band tuner and a lower band tuner.

In the case where the tuner is divided into a higher band one and a lower band one as described above, the mixer circuit can be used in common with respect to both of the higher and lower band tuners. However, such common use of the mixer circuit causes the higher and lower band tuners to have an electrically adverse effect upon each other since they are electrically connected with each other through a certain means.

Hence, when a channel within the higher band is selected by means of the higher band tuner, for example, the lower band tuner will disturb the normal function of the higher band tuner. This problem can effectively be solved by the arrangement of FIG. 11, wherein the reference numeral 701 represents a higher band tuner, 702 a lower band tuner, and 703 an input terminal associated with both of the higher and lower band tuners.

Description will now be made of the composition of the higher band tuner 701 which comprises a high frequency input circuit 704, a high frequency tuned amplifier circuit 705, a local oscillator circuit 706 and a mixer circuit 707. A radio wave received at the input circuit 704 is tuned and amplified in the high frequency tuned amplifier circuit 705 so that a predetermined television signal is produced which is in turn mixed with a signal produced by the local oscillator circuit 706. Thus, an intermediate frequency is obtained at a terminal 708.

On the other hand, the lower band tuner 702 is so designed that a signal entering a high frequency input circuit 709 is amplified in a high frequency tuned amplifier circuit 710 and then supplied to a mixer circuit 707 together with the output of a local oscillator circuit 711. Thus, an intermediate frequency is obtained at the terminal 7 08.

A power source is always supplied to the mixer circuit 707 through a terminal 712, and it is selectively supplied to the higher band tuner 701 and the lower band tuner 702 by switching a change-over switch 713 to a terminal L or H.

When a certain channel within the higher band is to be received with the power source switched to the terminal H, if a channel signal in the lower band is mingled with the signal in the higher band tuner, the signal is transmitted from a tuning circuit 714 of the high frequency tuned amplifier circuit 705 of the higher band tuner 701 to a tuning circuit 715 of the high frequency tuned amplifier 710 of the lower band tuner 702 which is rendered inoperative, so that it is also tuned in the tuning circuit 715 since the tuning circuit 714 is coupled to the tuning circuit 715 on the input side of the mixer circuit 707. Thus, an undesirable phenomenon as interference occurs in the mixer circuit 707. In order to prevent such phenomenon, a higher band pass filter circuit 7 04' which is adapted to greatly attenuate the lower band signal is provided in the input circuit of the higher baud tuner 701. The frequency vs. reactance characteristic of the circuit 704' is as shown in FIG. 13, and this circuit is designed so that the frequency foo corresponding to the pole point is selected to be in the neighborhood of the center of the lower band and the frequency f corresponding to the zero point is selected to be in the neighborhood of the center of the higher band. Thus, the filter circuit 704' functions as a two-terminal circuit which represents a low impedance with respect to the higher band and a high impedance with respect to the lower band.

In this way, any signal within the lower band is cut off so that any desired signal within the higher band can be obtained, thus preventing interference due to the fact that the lower band tuner operates during the selection of a channel within the higher band. In addition, since the circuit arrangement described above represents a high impedance with respect to the lower band, substantially no loss is caused on the input side of the high frequency 10 amplifier circuit 710 of the lower band tuner when a desired channel within the lower band is to be received, so that deterioration in the gain and negative feedback performance can -be prevented.

A circuit 704" inserted in the input circuit 709 of the lower band tuner 702 has such a frequency vs. reactance characteristic as shown in FIG. 14, wherein the frequency foo corresponding to the pole point is selected to be in the vicinity of the center of the higher band and the frequency corresponding to the zero point is selected in the neighborhood of the center of the lower band. The function of the circuit 704 is quite similar to that of the circuit 704, except that the higher band is changed to the lower band.

By switching the switch 713 to the terminal H to render the higher band tuner 701 operative, as shown in the drawing, the power source is supplied to the high frequency tuned amplifier circuit 705 and the local oscillator circuit 706. In this case, the mixer circuit 707 is always fed with the power source from the power source terminal 712. Thus, any channel within the higher band (4 to 12 channels in the Japanese system) can be selected by applying a variable voltage from a terminal 722 to

variable capacitance diodes

716, 717 and 718.

Similarly, any channel within the lower band (1 to 3 channels) can be selected by switching the change-over switch 713 to the terminal L.

As described above, the mixer circuit can be used in common, and the causes for interference between the higher and lower band tuners can be eliminated, resulting in a reduced loss of the inputs to the higher and lower band tuners. In this way, it is possible to develop a tuner of an improved performance.

FIG. 15 shows the case where the channel selecting operation of a television receiver of this type is effected on a remote control basis at a position remote from the receiver. An example will be described with reference to FIG. 15, wherein the reference numeral 801 represents a tuner portion of the television receiver, and 'D D and D are channel selecting variable capacitance diodes incorporated in the input circuit, inter-stage circuit and local oscillator circuit included in the tuner 801, respectively, these diodes being shown as being taken out of the tuner portion for the illustrative purpose. E is a power source for selecting a desired channel, and E and E, are power sources which are applied to the tuner 801 to effect the channel switching operation between the higher and lower bands. Although in this figure, E and E are shown as being of opposite polarities, they may be of a single polarity when the tuner is such as is shown in FIG. 5.

The reference numeral 802 denotes a connector adapted to connect the respective lead wires from a controller 803 to the television set, and P to P are connection terminals provided in the connector #802. All the above elements are incorporated in the television set.

The controller 803 consists of a variable resistor 804 divided into two sections and a switch 805. The both terminals of the power source E are connected with fixed

contacts

806 and 807 of the variable resistor 804 through the contacts P and P of the connector 802 and

suitable resistors

808 and 809 respectively, and a slide contact 810 of the variable resistor 804 is connected with the variable capacitance diodes D D and D through of the variable resistor 804 over the fixed contacts 806 from the left to the right (as viewed in the drawing), so that the barrier capacitances of these diodes are decreased. Thus, the channel received by the tuner is gradually changed from a lower one to a higher one.

Such change-over is required because the television broadcast band is divided into two segments or more, for example, a higher one and a lower one (1 to 3 channels and 4 to 12. channels).

To meet such requirement, there is provided the switch 805. The switch 805 is actuated in interlocking relationship with the slide contact 810 and designed so that it assures the position b when the slide contact 810 slides on the fixed contacts 806 while it assumes the position a when the slide contact 810 slides on the fixed contacts 807.

When the switch is placed in engagement with the contact a, a positive voltage is applied from the power source E to the tuner through the contacts P and P so that the tuner is made ready to receive any channel in the higher band by driving switching elements such as diodes, while when the switch is brought into engagement with the contact b, a negative voltage is applied from the power source E to the tuner 801 through the contacts P and P so that the tuner is made ready to receive any channel in the lower band.

In the foregoing, the polarities of the power sources E and E have been fixed for the sake of explanation, but this is not by way of limitation. It is to be noted that it is only required that, any power sources to ensure the desired band switching operation of the tuner be connected with the latter.

Furthermore, the band switching circuit provided in the tuner may take any form.

Alternatively, the switch 805 may be mounted on a shaft common to that of the variable resistor 804 so that the switch may be operated through forward or backward movement of the shaft. In this case the switch 805 may be provided with increased terminals and another power source may be provided in addition to the power sources E and E to control a UHF tuner. Thus, it may be possible to achieve remote control with respect to the entire VHF-UHF channels.

In the foregoing, description has been made of tuners using a channel selecting arrangement wherein the television broadcast frequency band is divided into the higher band and the lower hand because of the limitation of the capacitance variation range of variable capacitance diodes used as tuning and oscillation changing elements. However, such band division increases the manufacturing cost. Therefore, it is desired that the channel selection be achieved without dividing the television broadcast band into the higher band and the lower band. However, it is impossible to further expand the capacitance variation range of the presently available variable capacitance diodes due to their characteristics. Now, description will be made of an arrangement wherein use is made of variable capacitance diodes of which the characteristic is left as it is but the television broadcast band is not divided into the higher band and the lower band. In the conventional channel selecting device of this type, its high frequency tuning circuit is constructed as shown in FIG. 16. That is, a variable capacitance diode 902 is connected in parallel with an inductance 901 to form a parallel resonance circuit which is adapted to perform tuning operation.

With such arrangement, the capacitance variation range C -C of the variable capacitance diode 912 is given by where C is the distributed capacitance of the circuit, and f and f represent the upper and lower limits of the required tuning frequency range, respectively.

As will be seen from the Equation 1, the distributed capacitance C serves to decrease the value of f /f and in order to maintain f /f at a constant value, it is required that the capacitance variation range C C be increased.

Therefore, the arrangement of FIG. 16 requires a very wide capacitance variation range of the variable capacitance diode 902. However, it is impossible to ensure the tuning operation with respect to television waves of a wide frequency range by means of a single variable capacitance diode, which will be understood from the characteristics of the commercially available variable capacitance diodes.

For this reason, a tuning arrangement wherein the television band is divided into the higher band and the lower band has been used, as described above.

In accordance with this invention, there is provided an arrangement wherein the capacitance variation ratio of a variable capacitance diode is effectively utilized without any further improvements in the characteristic relating to the capacitance variation range of the variable capacitance diode and the tuning operation is performed without dividing the television band into the higher band and the lower band.

An example of this arrangement according to the present invention will now be described with reference to FIGS. 17 and 18. As shown in FIG. 17, a series resonance circuit is formed by a capacitor 904, a tuning coil 905, and a variable capacitance diode 906, and this circuit functions as a tuning circuit so that a tuned signal is taken out from a coil 907 representing a suitable impedance.

In this case, the variable capacitance diode 906 can directly be connected with the tuning coil 905 and a dis tributed capacitance C which is in parallel with the diode 906 is negligible as compared with the capacitance ratio of the diode 906 since the distributed capacitance is separated by the inductance of the tuning coil 905.

Assume that the capacitance of the condenser 904 is C then the composite capacitance C of the condenser 904 and the distributed capacitance C is given by the following Equation 2.

Hence, a tuned frequency f is given by CC c'+ c (3 where C is the capacitance of the variable capacitance diode 6. The upper and lower limits f and f of the tuned frequency are as follows:

1 f fi 1 fmin min c'+o.... From Equations 4 and 5 is derived the following relation:

1 1 max 2 arin i Normally, it is possible that C is several pf. or larger, C to 20 pf. and C several pf. or less. Therefore, Equation 6 can be changed as follows:

f min min Comparison of Equation 7 with Equation 1 shows that the effect of C can be neglected.

FIG. 18 shows an arrangement wherein one end of a variable capacitance diode 909 is high frequency-wise grounded and the other end thereof is connected with a tuning circuit 910 and a capacitor 911 is coupled with the other end of the tuning coil 910.

E is a power source from which a different voltage is applied to the variable capacitance diode 909.

The operation of the arrangement shown in FIG. 18 Wlll now be described. A signal appearing at a terminal 908 is delivered to a series resonance circuit formed by the variable capacitance diode 909, tuning coil 910 and condenser 911 through the tuning coil 910, and the signal thus tuned is taken out from a terminal 912 of the series resonance circuit.

Thus, the following effect can be produced.

In the Iapanses television system, the center frequency of the lowest channel is 93 mc., and that of the highest channel is 219 me. From this, the following result can be Since variable capacitance diodes of which the ratio of the maximum to the minimum capacitance is approximately max have recently been developed, it is possible to realize Equation 7. That is, in the conventional VHF tuners using variable capacitance diodes, the switching operation between the higher band and the lower band was performed through the use of a switch or other means. In accordance with this embodiment of the present invention, however, the entire VHF television channels can be selected without performing such switching operation.

In the American system, the lower band is in the range of 54 me. to 88 mc., the center frequencies of the highest and lowest channels being 85 mc. and 57 me. respectively,

and hence fmax 2 .2 frnin 2 Therefore, from Equation 7, it will be seen that the ratio of the maximum to the minimum capacitance of variable capacitance diodes in use may be about 2.2

( limax antu If the distributed capacitance C amounts to 4 pf. or more, the influence by the distributed capacitance is no longer negligible. Since the minimum value C of the variable capacitance diode is normally nearly 6 pf., the maximum value C is calculated from Thus, assuming that C =4 pf., (C /C )=3.0. When a conventional variable capacitance diode of (C /C )=3.0 is more expensive of min and that other technical problems will arise from the expanding of the range of voltage applied to the variable capacitance diode to achieve IUBX 0min 3.0

then arrangement of FIG. 18 will become useful. In the case where an applied voltage must be decreased to a low value, the rate of change of the junction capacitance of the variable capacitance diode with respect to voltage will become so high that cross-modulation and other disturbance due to the presence of non-linear elements will inevitably occur. In accordance with the present invention, the range of voltage required for the necessary capacitance variation range can be made narrow as compared with that in the conventional circuits, thereby eliminating the disturbance stemming from the attainment of said variation range.

In the foregoing, description has been made of the method of receiving the entire television broadcast signal band including the higher and lower bands and the method of applying a channel selection control voltage. Now, description will be made of a channel selecting arrangement wherein said methods are automatically carried out. FIG. 19 shows an example of such arrangement, wherein the reference numeral 1001 denotes a tuner including a high frequency tuned amplifier circuit 1002, a mixer circuit 1003 and a local oscillator circuit 1004. Variable selecting, tuning and oscillating elements of this tuner 1001 are composed of variable capacitance diodes. By changing a voltage applied to these variable capacitance diodes to change the capacitance values of the latter, the tuning and oscillating conditions of the high frequency tuned amplifier circuit 1002 and the local oscillator circuit 1004 incorporated in the tuner are so varied as to select a desired television broadcast channel.

In the tuner 1001, a frequency tuned in the high frequency tuned amplifier circuit 1001 and a frequency produced by the local oscillator circuit 1004 are supplied to the mixer circuit 1003 to be converted into an intermediate frequency which is in turn supplied to an intermediate frequency amplifier circuit 1005 having such a characteristic as shown in FIG. 21.

The reference numeral 1006 represents a detector circuit which is adapted to detect the intermediate frequency signal. The latter signal ispartially supplied to a frequency discriminator circuit 1007 prior to being delivered to the detector circuit 1006. The frequency-discriminator circuit 1007 is so designed as to provide an output voltage corresponding to the intermediate frequency, as shown in FIG. 20. That is, if the intermediate frequency is deviated from a reference point A, there is produced a DC output voltage corresponding to the deviation, which is in turn supplied to a trigger circuit 1009 through a gatecircuit 1008.

The trigger circuit 1009 is designed so that it operates to produce a pulse-like output voltage if the output voltage of the frequency discriminator circuit 1007 is deviated from the set reference point A by any small amount.

Such pulse-like output voltage is also produced by turning on a switch 1010 of the trigger circuit 1009 whereby a sweep circuit 1011 is controlled.

Closing the switch 1010 causes the trigger circuit 1009 to produce the pulse-like output voltage by which the sweep circuit 1011 is operated.

This sweep circuit 1011 has its voltage successively varied with time and the output of which is applied to the variable capacitance diodes serving as the variable tuning element and oscillation frequency changing element included in the high frequency tuning circuit 1002 and local oscillator circuit 1004 constituting the tuner 1001. If each of the variable capacitance diodes is controlled by the output voltage of the sweep circuit 1011 so as to possess a capacitance value suitable to receive certain television broadcast, such broadcast can be received, and the signal thus received is delivered to the intermediate frequency amplifier 1005 thorugh the mixer 1003 and then to the frequency discriminator circuit 1007.

In case the intermediate frequency which has arrived at the frequency discriminator circuit 1007 is a normal one, then the output voltage of the discriminator has the value corresponding to the point A of FIG. 20, so that the output voltage applied to the trigger circuit 1009 becomes zero.

As a result, the trigger circuit 1009 is prevented from producing any output voltage so that the output voltage of the sweep circuit 1011 may be maintained at a constant value, thereby making it possible to receive a desired television broadcast signal.

Such conditions are illustrated in FIGS. 22A, B, C and D. FIG. 22A shows the opening and closing conditions of the switch 1010. If the switch 1010 is temporarily turned on, the trigger circuit 1009 operates to render the sweep circuit 1011 operative. FIG. 22C illustrates the resulting output waveform, and FIG. 22D shows the output voltage waveform obtained from the trigger circuit 1009 of the sweep circuit 1011. The output voltage of the sweep circuit 1011 is successively increased in a stepped manner and it is returned to the original state when the entire channel or the lower "band is received.

Although the output voltage of the sweep circuit 1011 is kept constant during reception, when the frequency of local oscillation is drifted due to variations in the values of the variable capacitance diodes and other components incorporated in the tuner 1001 and variations in the power source voltage, a small output voltage is produced to auto-- matically control the drifted local oscillation to the normal frequency, and it depends upon the deviation of the intermediate frequency arriving at the frequency discriminator circuit 1007.

Since a television signal carrier wave consists of a video carrier wave and an audio carrier wave, the aforementioned arrangement will have such a disadvantage that the automatic tuning circuit tends to be tuned to the audio carrier wave even if it is desired to control the automatic tuning circuit with the aid of the video carrier wave. Obviously, the tuning should be effected with respect to either one of these carrier waves.

To this end, the synchronizing signals are separated by a synchronizing signal separator circuit 1012 and rectified by a rectifier circuit 1013 so as to be supplied to the gate circuit 1008 so that the gate circuit 1008 may be opened to pass a signal from the discriminator 1007 while receiving an input signal from the rectifier circuit 1013. The signal delivered from the freqeuncy discriminator circuit 1007 to the trigger circuit 1009 can be limited to the video signal component, thereby preventing any erroneous tuning operation from being caused by the audio carrier wave.

Furthermore, a flip-flop circuit 1014 is driven by virtue of the repetition of the saw-tooth wave voltage produced by the sweep circuit 1011.

For example, the flip-flop circuit 1014 may be driven in such a manner that the circuit produces a positive output or a negative output each time odd numbered sawtooth portions of the saw-tooth wave output are applied thereto from the sweep circuit 1011.

A gate circuit 1015 is operated by the output of the flipflop circuit 1014 to change the voltage of a power source 1016 which is applied to the tuner 1001, thereby performing the switching operation between the higher and lower bands of the VHF band. 1

By combining the sweep output with the output of a multi-vibrator (not shown), it is possible to develop this arrangement into a three-band system including one UHF band and two VHF bands. Although, in the foregoing, description has been made of the case where the frequency discriminator circuit 1007 is used, use can equally be made of any other circuit which is so designed as to produce an output voltage corresponding to the deviation of the intermediate frequency.

As described above, in accordance with this invention, the intermediate frequency carrier wave is frequency-discriminated, and the resulting output is supplied to the trigger circuit through the gate circuit which is operated by the synchronizing signals. Then the sweep circuit is controlled by the trigger signal provided by the trigger circuit, and the output voltage of the sweep circuit is applied to the variable capacitance diodes of the tuner to effect automatic channel selection. In the conventional television receiver, such automatic selection was technically very difficult to achieve because of the fact that the television carrier consists of two types of carrier waves, or a video carrier wave and audio carrier wave. In accordance with this invention, however, such difficulties can effectively be removed by using a gate circuit which is so designed as to be operated by synchronizing signals,

thus making it possible to achieve automatic television channel selection.

In addition, if the freqeuncy of local oscillation is drifted due to variations in the values of the variable capacitance diodes and other components incorporated in the tuner and variations in the power source voltage, such drift is automatically compensated so that the local oscillation has the normal frequency by suitably adjusting the operating point with respect to the discrimination of the intermediate frequency and that of the trigger circuit.

What is claimed is:

1. A tuner comprising: a high frequency amplifier circuit having a tuned circuit, the tuned circuit elements of which are constituted by variable capacitance diodes; a local oscillator circuit having a resonant circuit, the resonant circuit elements of which are constituted by variable capacitance diodes; a mixer circuit for mixing the output of said high frequency amplifier circuit with the output of said local oscillator circuit; and a control voltage source means for supplying a control voltage to each of said variable capacitance diodes to change the tuned and resonant frequencies; each of said tuned circuit and resonant circuit including a first inductor coil, a second inductor coil coupled with said first inductor coil to increase the total inductance of the coils, a switching means connected in parallel with said second inductor coil and an electric potential source of a single polarity; said switching means serving to apply a potential from said potential source of a single polarity to said second inductor coil to selectively change the effective inductance of said second inductor coil, whereby change-over of the tuner is effected between a relatively higher freqeuncy band and a relatively lower frequency band.

2. A tuner as set forth in claim 1, wherein said first and second inductor coils are directly coupled with each other and said switching means comprises another variable capacitance diode connected to the connection point of said coils and to said electric potential source so as to be supplied with two different potentials of a single polarity through a switch.

3. A tuner as set forth in claim 1, wherein said first and second inductor coils are coupled with each other through a magnetic core constituting a magnetic path between said coils, and said switching means comprises a switch in parallel-with said second inductor coil to selectively make the latter inoperative.

4. A tuner as set forth in claim 1, further comprising a remote control means comprising a band selection switch connected through lead wires with said second inductor coils for effecting the change of the effective inductance of each said second inductor coil and a variable resistor for the channel selection interlocked with said band selection switch.

5. A tuner comprising: a high frequency amplifier circuit having at least one tuned circuit, the tuned circuit elements of which are constituted by variable capacitance diodes; a local oscillator circuit having a resonant circuit, the resonant circuit elements of which are constituted by variable at least one capacitance diode; a mixer circuit for mixing the output of said high frequency amplifier circuit with the output of said local oscillator circuit; a frequency discriminator circuit for monitoring the output of said high frequency amplifier circuit; a gate circuit operable to conduct the output of said frequency discriminator circuit in response to a synchronizing signal; a trigger circuit driven by the output of said gate circuit; a sweep circuit controlled by the output of said trigger circuit and connected with said high frequency amplifier circuit and said local oscillator circuit to apply as a control voltage the output voltage of the sweep circuit to and vary the capacitance of each of said variable capacitance diodes in said high frequency amplifier circuit and in said local oscilaltor circuit to change the tuned and resonant frequencies; and a flip-flop circuit operative in response to blanking pulses from said sweep circuit, the output of 17 18 said flip-flop circuit being fed to said high frequency 3,130,264 4/1964 Dietz 1785.8 amplifier and to said local oscillator circuit, whereby the 3,264,566 -8/ 1966 Kaufman et al 325465 change-over of the tuner is effected between a relatively 3,309,613 3/1967 Bell 325-462X lower frequency band and a relatively higher frequency 3,354,397 11/1967 Wittig 325-459 band and the tuner is automatically tuned to a desired 3,390,228 6/1968 Bell 33416X channel. 5

R f ct d RICHARD MURRAY, Primary Examiner e erences 1 e B. V. SAFOUREK, A t t E UNITED STATES PATENTS an Xammer 2,601,384 6/1952 Goodrich, Jr. 33416X 10 2,745,961 5/1956 Pan 325458X 325463, 464; 334-12, 15

3,010,015 11/1961 Pepperberg 33412X UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 544, 903 Dated December I 1970 Yoichi SAKAMOTO Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The inventor 5 name should read Yoighi SAKAMO IO not Yoighi.

In the priority claims, the following errors should be correct The 6th priority should read:

January 27, 1967 4217562 not January 27, 1967 42111507;

Two Japanese applications are missing from the claim and shou] be added as follows:

May 23, 1967 42/33222 and February 10, 1967 42/11507.

Signed and sealed this 26th day of October 1971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Acting Commissioner of Patent Attesting Officer