JPS5934199Y2 - Electronic tuning tuner device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an electronic tuning tuner device used in a television receiver.

Generally, an electronic tuning tuner that selects a channel by applying a tuning voltage to the diode using a variable capacity diode is provided with a band switching means for switching the reception band (high channel, low channel).

This band switching means is configured not only to switch the filter characteristics of the signal path but also to switch the constant related to the oscillation frequency of the local oscillation circuit.

When changing the constant of the local oscillation circuit, it is usually done by turning on and off a switching diode.

However, the oscillation output of the oscillation circuit. Because of the series resistance of the switching diode, etc.

High channels tend to be lower than low channels.

For this reason, the oscillation voltages that optimize various performances including gain do not match between the high channel and the low channel.

For example, in terms of profits. If the oscillation voltage is set with priority given to the high channel with low gain, the oscillation voltage will be too high in the low channel, and there is a risk that unnecessary radiation will increase.

In order to compensate for these drawbacks, a circuit as shown in FIG. 1 has been devised, but this results in a complicated structure and an increase in the number of parts.

In FIG. 1, 2 is an oscillation section including an oscillation transistor 20, and 1 is a mixing circuit.

Reference numeral 10 denotes a variable capacitance diode, whose capacitance is varied by a tuning voltage supplied from a tuning voltage input terminal 17 via a resistor 14, and the oscillation frequency of the oscillation circuit can be changed.

Further, 9 is a switching diode which is turned on when the switching terminal 15 is grounded (high channel reception).
It turns off when a positive voltage is supplied to the switching terminal 15 (low channel reception).

Further, 16 is a switching current supply terminal.

Therefore, when the switching diode 9 is turned on during high channel reception, the coil 5 and the variable capacity diode 10 mainly serve as a load for the oscillation transistor 20.
A local oscillator voltage is injected into the input terminal of the mixing circuit 1 through the vessels 3 and 4.

Furthermore, during low channel reception, the switching diode 9 is cut off, so the coil 6 and the variable capacitance diode 10 mainly constitute a tank circuit, and the injected voltage is injected into the input terminal of the mixing circuit 10 through only the capacitor 3.

That is, switching is performed using a switching diode so that the injection capacitance when receiving a high channel is larger than that of a low channel.

However, as mentioned above, this method is complicated and requires two volumes, 3 and 4.

Note that 7 and 8 are capacitors for setting the time constant, 19 is a coupling capacitor,
12, 13, and 14 are resistors, and 21 is a received signal input terminal.

This idea was made in view of the points mentioned above.
It is an object of the present invention to provide an electronic tuning tuner device that can reduce the number of parts, simplify the structure, and stabilize the oscillation voltage.

Embodiments of this invention will be described in detail below with reference to the drawings.

That is, in FIG. 2, 25 is an input terminal to which a television introduced from an antenna is applied via a high frequency amplification circuit (not shown), and the input signal is guided to a mixing circuit 26.

This input terminal 25 is connected to one electrode of a capacitor #27 that introduces the oscillation output into the mixing circuit.

The other electrode of this container 27 is grounded via a series circuit of a coil 28 and a capacitor 29.

The connection point between the coil 28 and the capacitor 29 is connected to the resistor 3.
0 to a switching terminal 31 for applying a switching voltage for binding switching.

Further, the connection point between the coil 28 and the capacitor 27 is connected to one terminal of the coil 33 and one electrode of the capacitor 35 through a switching diode 32 in the opposite direction, and is further connected to the oscillation circuit 37 through a coupling capacitor 36. It is connected to the base of the constituent oscillation transistor 38.

The other terminal of the coil 33 is grounded via a capacitor 34, and the other electrode of the capacitor 35 is grounded via a variable capacitance diode 39.

The connection point between the capacitor 35 and the variable capacity diode 39 is connected via a resistor 40 to a tuning voltage input terminal 41 to which a tuning voltage is applied.

Further, one terminal of the coil 33 is connected to a terminal 46 of a block resistor device 45.

Next, the block resistance device 45 will be explained.

The block resistor device 45 is, for example, a plurality of printed resistors provided on an insulating substrate and provided with terminals 46, 47, 48° 49.

The terminal 46 is connected to a terminal 49 via a resistor 50.

This resistor 50 functions to limit the current flowing through the switching diode 32.

Further, the resistors 51 and 52 are bias resistors of the mixing circuit 26, the terminal 48 is connected to the base of the transistor Tr1 forming the mixing circuit, and the terminal 47 is also connected to the base of the transistor Tr2 forming the mixing circuit. has been done.

The present invention is constructed as described above, and has resistors 50 and 51.
A floating receptacle 53 formed in the lead wire portion is utilized.

First, during high channel reception, the switching diode 32 is conductive, so the capacitor 27 and the floating capacitor 53
The injection capacitance is the sum of the above, and since the switching diode 32 is cut off during low channel reception, only the floating chamber 53 becomes the injection capacitance.

Strictly speaking, when receiving a high channel, the series connection of the interelectrode capacitance of the switching diode 32 and capacitor #27 is added to the floating capacitor 53, but in any case, the injected capacitance when receiving a low channel is It is very easy to make the signal smaller than when receiving high channels.

According to this idea, first, the block resistor device has the advantage of being able to incorporate many elements and can be constructed in a small size, so the entire block resistance device can be made small and utilizes a floating container. This also reduces the number of parts.

It should be noted that the present invention is not limited to the above embodiments, but
A configuration as shown in the figure may be used.

The same parts as in FIG. 2 will be described with the same reference numerals.In this embodiment, the part for setting the stray capacitance has been changed compared to the previous embodiment.

That is, one terminal of the coil 33 is directly connected to the input terminal of the mixing circuit 26 via a capacitor 55, and one terminal of the coil 28 is connected to a current supply terminal via a resistor 50 in a resistor device 45. 49.

In this case as well, stray capacitance 56 occurs and the same effect as in the previous embodiment can be obtained.

As explained above, according to this invention, by using the stray capacitance between the terminals of the resistor in the block resistor device, it is possible to achieve low channel reception and noise with only one injection capacitance.
Since the local injection container can be changed when receiving a low channel, it is possible to reduce the difference between the local voltage when receiving a low channel and the local voltage when receiving a low channel. This makes it possible to eliminate deviations in the specific performance of tuners in channels and high channels.

In order to achieve this, it is possible to provide an electronically tuned tuner device that reduces the number of parts and has a simpler and more compact structure.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional electronic tuning tuner device, Fig. 2 is a circuit diagram showing an embodiment of the electronic tuning tuner device of the present invention, and Fig. 3 is a circuit diagram showing another embodiment of the invention. It is. 26... Mixing circuit, 27... Capacity, 31... Switching terminal, 2B, 33... Coil, 32...
Switching diode, 38... Oscillation transistor, 39... Variable capacitance diode, 45... Block resistor device, 50.51.52... Resistor, 53.56.
... Stray capacitance.

Claims (1)

[Scope of utility model registration request] A local oscillation circuit device includes a switching diode for switching low channel and high channel bands between at least two tuning coils, and outputs are selectively taken out from both terminals of the diode; A mixing circuit connected to one end of the diode of the oscillation circuit device via a capacitor, a resistor for supplying a bias voltage to the active elements constituting the mixing circuit, and a resistor for supplying the bias voltage to one end of the switching diode. and a block resistor device formed on the same insulating substrate, and when receiving a high channel when the switching diode is on, the stray capacitance between the resistors and the capacitor are interposed between the local oscillation circuit device and the mixing circuit. , when receiving the low channel when the diode is off, by intervening only one of the capacitance components, the injection capacitance for receiving the low channel is made smaller than the injection capacitance for receiving the i channel, and the output of the oscillation circuit is An electronic tuning tuner device, characterized in that the electronic tuning tuner device is configured to supply the mixing circuit with: