JPS6337719A - Multiband oscillation circuit - Google Patents

Abstract

PURPOSE:To reduce the number of components of an oscillation circuit, to reduce the assembly space of the components, and to reduce the size of a tuner by using a varactor diode for plural bands in common. CONSTITUTION:Only the VHF-band component of a signal arriving a terminal 2 is passed through an input filter and selected and tuned to the frequency of a desired station by a VHF single tuning circuit 17; and the signal is amplified by an RF amplifying circuit 19 to a specific level, and then given specific selectivity by a double tuning circuit 20 and supplied to a mixer circuit 23. Then the signal is frequency-converted with a frequency from an oscillator 22 and outputted to a terminal 14. Then, a signal arriving at a terminal 1 is supplied to a single tuning circuit 18 and selected and tuned to the frequency of a desired station, and then the signal is supplied to a UHF double tuning circuit 21 through an RF amplifying circuit 19 to have specific selectivity characteristics; and the signal si frequencyconverted by a mixer 23 and outputted to a terminal 14. Thus, the variable capacity element is used for the VHF and UHF bands in common, so the number of the components is decreased and the tuner itself is reducible in size.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an oscillation circuit for a tuner, and more particularly to a multi-band oscillation circuit in which a single oscillation circuit can oscillate multiple bands.

<Summary of the Invention> The present invention provides an oscillation circuit for a multi-band tuner in which a capacitor and a heath connected between the collector and emitter of an oscillation transistor, and an inductance connected between the collectors are switched between bands, and a plurality of variable capacitance diodes are connected. By making the frequency band common, the number of parts in the oscillation circuit is reduced, and the space for assembling the parts is reduced, thereby making the tuner more compact.

<Prior Art> FIG. 4 shows a block diagram of a conventional superheterodyne tuner that receives VHF and UHF bands. ■
and 2 indicate input terminals for UHF and VHF bands. 3 is an input tuning circuit, 4 is an RF amplification circuit (high frequency amplification circuit), 5
numeral 6 is an oscillator circuit, and numeral 7 is a mixer circuit, each of which receives the UHF band.

8 is an input filter circuit, 9 is an input single tuning circuit, 10 is R
F increasing circuit, 11 is a double tuning circuit, 12 is an oscillator, and 13
are mixer circuits that receive the VHF band.

14 is an IF signal output terminal from the mixer circuit 13.

15 is VHF band and UHF band (hereinafter simply referred to as U・■)
It is a switching circuit.

When receiving a VHF band signal, 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 outputted from the terminal 14 as an IF multiplied signal of 58.75 Mllz. .

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 in the mixer circuit 7, and the mixed output is an IF multiplied signal 56.7
5 MHz) is amplified by the mixer circuit 13 via the U/■ switching circuit 15 and then output to the terminal 14. U・■
The switching circuit 15 switches the I from the UHF mixer only when receiving UHF.
It is turned on so as to supply the F-fold signal to the VHF mixer 13.

<Problems to be Solved by the Invention> In the conventional oscillation circuit described above, after configuring dedicated oscillation circuits 6 and 12 for U and Due to duplication,
There is a problem that a large number of parts are required.

Furthermore, since the assembly of the oscillation circuit into the tuner case requires space for the assembly of the U and ■ re-oscillation circuits, there is a problem that the tuner becomes large.

Furthermore, since there are a large number of parts, there is also the problem that the amplifier becomes costly.

The present invention aims to solve the various problems of the related art.

Means for Solving the Problems〉 The multi-band oscillation circuit according to the present invention switches between bands the capacitor connected between the collector and emitter of the oscillation transistor, and the inductance connected between the base and collector. It has a configuration in which capacitor diodes, generator transistors, etc. are common to multiple bands.

<Embodiment> FIG. 1 shows a circuit block diagram of a multi-band tuner including an oscillation circuit according to an embodiment of the present invention. Components that are the same as those in FIG. 4 are given the same reference numerals, and their explanations will be omitted.

16 is an input filter; 17 is a VHF single tuning circuit; 18 is a UHF single tuning circuit;
20 is a VHF double tuning circuit, 21 is a UHF double tuning circuit, 2
2 represents a U/■ shared oscillator, and 23 represents a U/■ shared mixer circuit.

C1 is a variable capacitor for tuning of the tuning circuits 17 and 18 for both UV and UV. C, , C, are variable capacitors of the dual tuning circuit 20 and 21 shared by U and ■.

The reception of VHF band will be explained. The signal entering terminal 2 is filtered through an input filter, allowing only VHF band signals to pass through.
After being selectively tuned to the frequency of a desired station in the HF single tuning circuit 17 and amplified to a predetermined level in the RF amplification circuit 19, it is given a predetermined selectivity characteristic in the double tuning circuit 2o and is supplied to the mixer circuit 23. is frequency-converted with the frequency from the oscillator 22 at 22, and the frequency-converted IF output signal is sent to terminal 1.
Output to 4.

Next, reception of the UHF signal will be explained. The signal entering the terminal 1 is supplied to the single tuning circuit 18, selectively tuned to the frequency of the desired station, and then sent to the U via the RF amplification circuit 19.
The signal is supplied to the HF double tuning circuit 21, given a predetermined selectivity characteristic, and then supplied to the subsequent circuit. The mixer circuit 23 performs frequency conversion in the same manner as described above, and outputs the IF multiplied signal to the terminal 14.

In this way, input tuning circuit 24.25 inter-stage tuning circuit 26.2
7 and in the oscillator 22, which will be described in detail later, the variable capacitance element is shared by U and V, so the number of components can be eliminated and the tuner itself can be made smaller.

Next, a specific circuit diagram of FIG. 1 is shown in FIG. 2.

It should be noted that in FIG. 2, the components other than the oscillation circuit 22 are irrelevant to the embodiment of the present invention, so their explanation will be omitted.

The oscillation circuit 22 is a Kolbitz type oscillation circuit, C2 is a transistor for oscillation, C2Q, C:l◎ is a capacitor connected between the collector and emitter of transistor Q, and Cal and C34 are connected between the base and emitter. capacitor, L! l L za and L! 5 is a coil and inductor selectively connected between the base and collector, C3'l is a capacitor for AC grounding the collector, LL& is an inductor for adjustment, and LZ'? denotes an inductor for stabilizing oscillation, and D V a and DV denote variable capacitance diodes for varying the oscillation frequency and for AFC, respectively. DI,,D,, are U・to which voltage is supplied from the VH terminal.
■A switching diode that turns on when receiving VHF band. DI? is a diode for switching between low and high bands when receiving VHF band.

The oscillation operation in the VHF band will be explained. During low band oscillation, a voltage is applied from the VL terminal to the diodes D, . . . , D, through the diode D4, and these are turned on. Then, a capacitance of C1° is added to the capacitance of the C collector-emitter capacitors. Also, the base
The emitter-to-emitter capacitance is the series capacitance of capacitors C31 and C34. And between the base and the collector there is an AC coil L2:1. L24 is connected. Low-band oscillation is performed with this circuit configuration, and the oscillation frequency can be varied by V.
This is done by applying a variable voltage from the T terminal to the variable capacitance diode DV4.

The difference in oscillation operation in the high band of the VHF band from that in low band oscillation is that the diode DISI DI
The switching voltage supplied to 6 is connected from terminal VH to diode D
, and that the voltage that turns on the diode DI7 is supplied from the terminal VH. Is the coil Lza the diode Dl? Since it is short-circuited, the oscillation coil is only LZ3. Note that the inductance component of Lt4 is very small and can be ignored for the VHF band.

Next, the oscillation operation in the UHF band will be explained. There is no switching voltage supply for the diodes D Is-'-=D +7, so they are turned off. Then, the collector-emitter capacitance is CZ? The capacitance between the base and emitter is Czs* 034 is connected in series with the terminal capacitance 1i (approximately IPF) of diode DI6 in the off state, and CIO is connected in parallel with diode DI&, and their combined capacitance is less than PF. It has a small capacity. Also, the base
The inductance component connected between the collectors is an inductor [)zs. In such a configuration, the oscillation frequency is varied by varying the capacitance of the variable capacitance diode DV4.

Furthermore, during UHF band oscillation, coil Lffi3+L2
4, the diode DIlk is off and the impedance is very large for the UHF band, so there is no effect.

The oscillation outputs of U and ■ are supplied to the next stage mixer circuit 23 via the coupling capacitor Cn&.

Note that the capacitor C3m is for DC cut. Power supply voltage to transistor Qt is always supplied from terminal B.

As described above, the oscillation circuit 22 includes a diode Dis.

[)+1. The configuration is such that the collector-emitter and base-emitter capacitors of the oscillation transistor are switched by turning on and off, and the inductance between the collector and base is also switched, so the oscillation of U and ■ can be switched with a simple configuration, and the oscillation element can be switched. It has the advantage of being able to be used for both purposes, reducing the number of parts and the space required to assemble the parts.

FIG. 3 shows a modification of the oscillation circuit 22. In FIG. Components that are the same as those in FIG. 2 are given the same reference numerals, and their explanations will be omitted. The oscillator circuit of FIG. 3 is designated by the reference numeral 22'. The difference from the oscillation circuit shown in FIG. 2 is that the oscillation output is taken out, and the oscillation output such as VHF is taken out from the coil 28 which is inductively coupled to the coil LZ3 (output terminal 29). Further, an oscillation output such as UHF is taken out by an inductor L2Q inductively coupled to the inductor Lzs (output terminal 30).

In this way, the method of extracting the oscillation output by inductive coupling separately for U and ■ is such that the oscillation circuit 2γ is able to absorb the effects of changes in impedance, etc. due to changes in temperature characteristics, etc., in the mixer circuit 23 connected to the next stage of this oscillation circuit. This has the advantage that the oscillation frequency is stable.

<Effects of the Invention> The multi-band oscillation circuit according to the present invention described above includes the oscillation transistor Q22 and the variable capacitance diode D for varying the oscillation frequency.
V4. Variable capacitance diode DVS for AFC, capacitor Czq* C31 for configuring the Corvitz oscillation circuit
1C34+ C371 and resistances for myas R,,R
, etc. are all used in common during oscillation in the VHF band and UHF band, and in this respect, a significant reduction in the number of parts has been achieved.

This also helps reduce the cost of the large tuner.

In addition, coupled with the drastic reduction in the number of parts, there is no need to assemble the UV oscillation circuit separately as in the past, and it can be assembled in one place, saving space when assembling parts. The width can be reduced to a large extent, making it possible to realize a compact tuner.

[Brief explanation 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 concrete block diagram of the block diagram of FIG. 1 including an oscillation circuit according to an embodiment of the present invention. 3 is a circuit diagram of a modification of the oscillation circuit of FIG. 2, and FIG. 4 is a circuit block diagram of a conventional multiband tuner. 22...Oscillation circuit, Q2...Oscillation transistor,
D V 4...Capacitance diode for variable oscillation frequency, D
V,...AFC variable capacitance diode IS~1)
tt...Switching diode, L23+L
24...Coil, Lzs~L2? ...inductor,
C29~C3B...Capacitor.

Claims (1)

[Claims] A Kolbitz type oscillator circuit for a multi-band tuner receiving first and second bands, comprising: a capacitor and a first switch interdiode connected in alternating current between the collector and emitter of an oscillation transistor; , a coil and a second switching diode connected in alternating current between the base and collector of the oscillation transistor, and a resonant line and a variable capacitance diode connected in alternating current between the base and collector of the oscillation transistor, A multiband oscillator circuit configured such that the first and second switching diodes are closed when receiving the first band, and the first and second switching diodes are opened when receiving the second band. .