JPH07120966B2 - Multi-band oscillator circuit - Google Patents

Description

The present invention relates to a tuner oscillator circuit, and more particularly to a multi-band oscillator circuit capable of oscillating a plurality of bands with a single oscillator circuit.

<Summary of the Invention> In the oscillation circuit of a multi-band tuner, the present invention switches a capacitor connected between the collector and the emitter of an oscillating transistor and an inductance connected between the base and the collector between bands, and includes a plurality of variable capacitance diodes. The tuner is downsized by reducing the number of parts of the oscillator circuit by making it common to the band and the assembling space of parts.

<Prior Art> FIG. 4 is a block diagram of a conventional super-heterodyne tuner that receives VHF and UHF bands. 1 and 2
Input terminals for UHF and VHF bands are shown. 3 is an input tuning circuit, 4
Is an RF amplification circuit (high frequency amplification circuit), 5 is a double tuning circuit, 6
Is an oscillator and 7 is a mixer circuit, each of which is a circuit for receiving the UHF band.

Reference numeral 8 is an input filter circuit, 9 is an input single tuning circuit, 10 is an RF amplification circuit, 11 is a double tuning circuit, 12 is an oscillator and 13 is a mixer circuit for receiving the VHF band respectively.

Reference numeral 14 is an IF signal output terminal from the mixer circuit 13. 15 is VH
It is an F-band and UHF-band (hereinafter simply referred to as U / V) switching circuit.

When receiving a signal in the VHF band, the signal from the double tuning circuit 11 and the oscillation frequency of the oscillator 12 are mixed in the mixer circuit 13, and the output is output from the terminal 14 as an IF signal of 58.75 MHz.

On the other hand, when receiving the UHF band, the selection signal from the double tuning circuit 5 and the oscillation frequency signal from the oscillator 6 are mixed by the mixer circuit 7, and the IF signal (56.75 MHz) that is the mixed output is U · V. After being amplified by the mixer circuit 13 via the switching circuit 15, it is output to the terminal 14. The U / V switching circuit 15 is turned on so as to supply the IF signal from the UHF mixer to the VHF mixer 13 only when receiving the UHF.

<Problems to be Solved by the Invention> In the above-described conventional oscillation circuit, the oscillation circuit dedicated to each of U and V is used.
After the components 6 and 12 are formed, they are required for each oscillation circuit such as an oscillating transistor and a variable capacitance diode, and they are duplicated. Therefore, there is a problem that a large number of parts are required.

Further, assembling the oscillation circuit in the tuner case requires a space for assembling both the U and V oscillation circuits, which causes a problem that the tuner becomes large. Also, because of the large number of parts,
There is also the problem of increased costs.

SUMMARY OF THE INVENTION The present invention aims to solve various problems in the related art.

<Means for Solving Problems> A multi-band oscillation circuit according to the present invention is a Colpitts-type oscillation circuit of a multi-band tuner that receives first and second bands, and is connected between an emitter of an oscillation transistor and ground. Circuit of a charged capacitor and a first switching diode, a second switching diode connected between the base and the emitter of the oscillation transistor, and a coil connected between one end of the second switching diode and ground. And a series circuit of a variable capacitance diode and a resonance line connected between the base of the oscillation transistor and the ground, and the first and second switching diodes are closed during reception of the first band, and the first and second switching diodes are closed. The first diode and the second diode are opened at the time of receiving the second band.

<Embodiment> FIG. 1 is a circuit block diagram of a multi-band tuner including an oscillation circuit according to an embodiment of the present invention. The same components as those in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted.

16 is an input filter, 17 is a VHF single tuning circuit, 18 is a UHF single tuning circuit, 19 is VHF, UHF common (hereinafter simply referred to as U / V common) RF
Enlargement circuit (high-frequency amplification circuit), 20 is VHF double tuning circuit, 21
Is a UHF double-tuned circuit, 22 is a U / V shared oscillator, and 23 is a U / V
Shared mixer circuits are shown respectively.

C ₁ is a tuning variable capacitor for the tuning circuits 17 and 18 for both U and V. C ₁ and C ₃ are variable capacitors of the double tuning circuits 20 and 21 for both U and V.

The time of reception in the VHF band will be described. Only the signal in the VHF band passes through the input filter of the signal coming into the terminal 2, is selectively tuned to the desired station frequency in the VHF single tuning circuit 17, and is then amplified to a predetermined level in the RF amplification circuit 19. , A predetermined selectivity characteristic is given by the double tuning circuit 20 and is supplied to the mixer circuit 23.
And the frequency from the oscillator 22 is frequency-converted, and the frequency-converted IF output signal is output to the terminal 14.

Next, reception of the UHF signal will be described. The signal input to the terminal 1 is supplied to the single tuning circuit 18, selectively tuned to the frequency of the desired station, and then supplied to the UHF double tuning circuit 21 via the RF amplification circuit 19 to have a predetermined selectivity characteristic. Is supplied to the subsequent circuit. The frequency is converted in the mixer circuit 23 in the same manner as described above, and the IF signal is output to the terminal 14.

As described above, the VHF single tuning circuit 17 and the UHF single tuning circuit 18 which are the input tuning circuits, the VHF double tuning circuit 20 and the UHF double tuning circuit 21 which are the interstage tuning circuits, and the oscillator 22 which will be described in detail later, use the variable capacitance element U. -Since it is shared by V, the number of parts can be eliminated and the tuner itself can be made smaller.

Next, a concrete circuit diagram of FIG. 1 is shown in FIG. The second
In the figure, the parts other than the oscillator circuit 22 are irrelevant to the embodiment of the present invention, and thus the description thereof is omitted.

The oscillating circuit 22 is a Colpitts type oscillating circuit. Q ₂ is an oscillating transistor, C ₂₉ and C ₃₀ are capacitors connected between the collector and emitter of the transistor Q ₂ , and C ₃₁ and C ₃₄ are between the base and emitter. Capacitor, L ₂₃ , L ₂₄ and L ₂₅ are coils and inductors that are selectively connected between the base and collector, C ₃₇ is a capacitor for AC grounding the collector, L ₂₆ is an inductor for adjustment , L ₂₇ is an inductor for stabilizing the oscillation, and DV ₄ and DV ₅ are variable capacitance diodes for varying the oscillation frequency and for the AFC, respectively. D ₁₅ , D ₁₆ is VH
This is a diode for switching between U and V, which is supplied with voltage from the terminal, and turns on when receiving VHF band. D ₁₇ is a diode for switching between the low band and the high band when receiving in the VHF band.

The oscillation operation in the VHF band will be described. Diode D ₁₅ via the diode D ₄ of the VL pin during the low band oscillator, D
_A voltage is applied to ₁₆ to turn them on. Then, the capacitance of C ₃₀ is added to the capacitance of the capacitor C ₂₉ between the collector and the emitter. Also, the capacitance between the base and the emitter is the series capacitance of capacitors C ₃₁ and C ₃₄ . And the base
The coils L ₂₃ and L ₂₄ are connected in an alternating current manner between the collectors.
Low-band oscillation is performed with such a circuit configuration, and the oscillation frequency is changed by applying a variable voltage from the VT terminal to the variable capacitance diode DV ₄ .

The difference in the oscillation operation in the high band of the VHF band from that in the low band oscillation is that the switching voltage supplied to the diodes D ₁₅ and D ₁₆ is performed from the terminal VH via the diode D ₅ and the diode D ₁₇ The point to turn on the voltage is supplied from the terminal VH. Coil L ₂₄ is diode D
_Since it is short-circuited by _{17, the} only coil for oscillation is L ₂₃ . The inductance component of L ₂₅ is very small for the VHF band and can be ignored.

Next, the oscillation operation in the UHF band will be described. Diode D ₁₅
Since the switching voltages are no longer supplied to ~ D ₁₇ , they are turned off. Then, the collector-emitter capacitance is C
Only _29, the capacitance between the base and emitter is C ₃₁ and C _34, and the capacitance between the terminals of the diode D ₁₆ in the off state (about IPF) is connected in series, and the capacitance between the diode D ₁₆ and C _{70 is} connected in parallel.
The combined capacity of these is smaller than PF. The inductance component connected between the base and the collector is the inductor L ₂₅ . In such a configuration, the oscillation frequency is changed by changing the capacitance of the variable capacitance diode DV ₄ .

In still during oscillation of the UHF band, the coil L _23, L ₂₄ diode
Since D ₁₆ is off and the impedance is extremely high for the UHF band, there is no effect.

The oscillation outputs of U and V are supplied to the mixer circuit 23 of the next stage via the coupling capacitor C ₃₆ .

The capacitor C ₃₈ is for cutting direct current. The power supply voltage to the transistor Q ₂ is always supplied from the terminal B.

As described above, the oscillation circuit 22 is configured to switch the collector-emitter and base-emitter capacitors of the oscillation transistor by switching the diodes D ₁₅ and D _{16 on} and off, and to switch the collector-base inductance.
It has the advantages that it can switch between U and V oscillations with a simple structure, can also serve as an oscillation element, and can reduce the number of parts and the assembly space for parts.

FIG. 3 shows a modification of the oscillator circuit 22. The same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. The oscillator circuit of FIG. 3 is designated by the reference numeral 22 '. The difference from the oscillation circuit of FIG. 2 is the extraction of the oscillation output, and the oscillation output of VHF or the like is extracted from the coil L ₂₈ inductively coupled to the coil L ₂₃ .
(Output terminal 29). The oscillation output of UHF or the like is taken out by an inductor L ₂₉ which is inductively coupled to the inductor L ₂₅ (output terminal 30).

In this way, the method of extracting the oscillation output by inductive coupling separately for U and V is a mixer circuit connected to the next stage of this oscillation circuit.
There is an advantage in that the oscillation circuit 22 'is less susceptible to changes in impedance and the like due to changes in temperature characteristics and the like in 23, and the oscillation frequency is stable.

<Effects of the Invention> The multi-band oscillator circuit according to the present invention described above includes the oscillation transistor Q ₂ and the variable capacitance diodes DV ₄ and A for varying the oscillation frequency.
Variable capacitance diode DV ₅ for FC, each element of the capacitor _{C 29, C 31, C 34} , C 37, and a bias resistor R _5, R ₆ or the like for constituting the Colpitts oscillation circuit of the VHF band and UHF band All of them are shared during oscillation, and in this respect a great reduction in the number of parts has been achieved. Moreover, the cost of a large tuner is reduced by this fact.

Also, combined with the drastic reduction in the number of parts, it is not necessary to assemble the U and V oscillator circuits separately as in the conventional system, but they can be assembled in one place, so the space for assembling parts is vast. Can be reduced to a small tuner.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a multi-band tuner to which an oscillation circuit according to an embodiment of the present invention is applied, and FIG. 2 is a block diagram of FIG. 1 including the oscillation circuit according to an embodiment of the present invention. FIG. 3 is a circuit diagram showing a modification of the oscillation circuit of FIG. 2, and FIG. 4 is a circuit block diagram of a conventional multi-band tuner. 22 …… Oscillation circuit, Q ₂ …… Oscillation transistor, DV ₄ ……
Oscillation frequency variable capacitance diode, DV ₅ …… AFC variable capacitance diode, D _{15 to} D ₁₇ …… Switching diode, L ₂₃ , L ₂₄ …… Coil, L ₂₅ 〜 L ₂₇ …… Inductor, C ₂₉
~ C ₃₈ …… Capacitor.

Claims (1)

[Claims] 1. A Colpitts type oscillation circuit of a multi-band tuner for receiving first and second bands, wherein a series circuit of a capacitor connected between an emitter of an oscillation transistor and ground and a first switching diode, A second switching diode connected between the base and the emitter of the oscillation transistor, a coil connected between one end of the second switching diode and the ground, and a resonance connected between the base of the oscillation transistor and the ground. A line and a series circuit of variable capacitance diodes, wherein the first and second switching diodes are closed during reception of the first band, and the first and second diodes are opened during reception of the second band. A multiband oscillator circuit configured as described above.