JPH0113466Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a tuner device in which the tuning voltage of a tuning circuit and a local oscillator is controlled by a PLL circuit in an electronically tuned combination tuner. By selectively switching the output of the oscillator using a switching diode and outputting a local oscillation signal, the output terminal of the local oscillator is reduced to one, thereby providing a tuner device with a small and simple configuration. With the goal.

For combination tuners with built-in electronically tuned multi-band tuners, the tuning voltage of those multi-band tuners is based on the output of the local oscillator.
In a conventional tuner device controlled by a PLL circuit, the number of output terminals of each local oscillator is the same as the number of multiband tuners, that is, the number of local oscillators. Since such a tuner has a large number of output terminals, the shape of the tuner device cannot be made compact, and it has various problems such as being complicated, requiring a large number of assembly steps, and being expensive.

This invention eliminates such conventional problems,
An embodiment of the present invention will be described below. 1st
The figure shows a partial block diagram of a tuner circuit according to an embodiment of the present invention. The dotted line 1 indicates a combination tuner that includes three tuners T ₁ , T ₂ , and T ₃ . Tuners _T1 to _T3 have different bands, and each tuner has an input tuning circuit.
A ₁ to ₃ , RF amplification circuits B ₁ to ₃ , double tuning circuits C ₁ to ₃ , and local oscillators D ₁ to ₃ . E ₁ to _{E 3} indicate power terminals supplied to each tuner. Note that the antenna terminal and IF output terminal of each tuner are not shown.
Tuners T ₁ and T ₂ are for the VHF band, and T ₃ is for the UHF band. L ₁ , L ₂ and L ₃ represent output coils that output the oscillation signals of the local oscillators D ₁ to D ₃ . The coils L ₁ to _{L 3} are tuning coils of the tuning circuit of each local oscillator, and therefore also serve as output coils for oscillation signals. By using both coils in this way, the number of parts is reduced and the configuration is simplified.

L ₁₁ , L ₁₂ , and L ₁₃ represent coupling coils corresponding to the respective output coils L ₁ , L ₂ , and L ₃ . R ₁ , R ₂ , and R ₃ are the output levels of the local oscillation output terminals P, respectively.
This is a level adjustment resistor to keep the outputs of D ₁ , D ₂ , and D ₃ constant. D ₁ , D ₂ , D ₃ are power supply terminals
E indicates a diode that is turned on (turned on) by the power supplies ₁ to ₃ . Resistors R ₁₁ , R ₁₂ , R ₁₃ are each diode D ₁
This is a current limiting resistor to allow an appropriate current to flow through ~ ₃ .

Power is selectively supplied to the power terminals E ₁ to E ₃ only to one tuner in a desired band. The tuner to which power is supplied enters a tuning reception state, and the oscillation signal of the local oscillator is output to the output coil. At this time, the power supply simultaneously turns on one of the diodes. Then, the oscillation signal induced in the coupled coil is output to the output terminal P. The signal appearing at the output terminal P in this manner is divided into an appropriate frequency by the frequency divider 2 and then supplied to the phase comparator 5. Next, the frequency from the reference oscillator 3 is set to a desired frequency by a programmable divider 4, and is supplied to a phase comparator 5, where it is compared with the frequency-divided signal, and the comparison output is converted into a direct current by a filter 6, and the terminal V _T
supplied to Then, the DC voltage input to V _T is supplied to the variable capacitance diode as the tuning voltage of the input tuning circuit, double tuning circuit, and local oscillation circuit of the tuner that is receiving the selected channel. By supplying power to an arbitrary tuner in this manner, it is possible to bring the arbitrary tuner into a tuning reception state and supply a tuning voltage to that tuner.

Capacitors C ₁ to ₃ are connected to each coupling coil L ₁₁ , L ₁₂ ,
This is a capacitor for flowing the output signal current induced into _L13 .

Next, FIG. 2 shows a perspective view of a specific coupled arrangement state of the output coils L ₁ to _{L 3} and coupling coils L ₁₁ , L ₁₂ , and L ₁₃ according to the present invention. The same parts as in FIG. 1 are given the same reference numerals. As can be seen in the figure, lead terminals of resistors R ₁ and R ₂ are used for output coils L ₁ and L ₂ , and coupling coils L ₁₁ and L ₁₂ are used. Further, a coaxial resonator transmission line is used for the output coil L ₃ of the UHF band tuner T ₃ , and a resistor R ₃ is arranged in parallel with this. In the case of resistor R ₃ , the frequency is high because it is in the UHF band, and the resistor body is used as a coupling coil. In this way, by using the resistor lead wire or itself as a coupling coil, the number of parts is reduced.

As mentioned above, in the tuner local oscillator output switching circuit according to the present invention, a diode is connected in series to the power supply of each tuner, and a coupling coil is provided at the connection point to be coupled to each oscillator, so that the output side of the diode is connected to a single oscillator. Since it is configured to be connected to the output terminal, it is not necessary to have the same number of output terminals as the local oscillation circuit as in the past, and the number of output terminals can be minimized to one.As a result, a simple and compact tuner can be obtained. , and was able to realize an inexpensive tuner.

[Brief explanation of the drawing]

FIG. 1 shows a switching circuit for a local oscillator of a tuner according to an embodiment of the present invention, and FIG. 2 is a perspective view showing the specific arrangement of an output coil and a feed coil according to the present invention. T ₁ ~ ₃ ... Tuner, E ₁ ~ ₃ ... Power terminal, D ₁
~ ₃ ...Local oscillator, _L1 ~ ₃ ...Local oscillation signal output coil, _L11 , _L12 , _L13 ...Coupling coil, _R1 ~ ₃ ...
...Resistor, D ₁ to ₃ ... Diode, P ... Output terminal, 1 ... Combination tuner.

Claims (1)

[Scope of utility model registration request] After dividing the frequency of the local oscillator and comparing it with the reference frequency, the tuning circuit and the PLL circuit of the tuner circuit that controls the tuning frequency of the local oscillator have a plurality of divided frequency bands. A plurality of tuners each having a local oscillator, a plurality of tuners housed in a single housing, a plurality of power supplies respectively supplied to the plurality of tuners, and each local oscillator for extracting signals from the plurality of local oscillators. a coupling element inductively coupled to the oscillator; a switching diode having one end connected in series to one end of each coupling element; the other end of each coupling element being connected to the corresponding power supply; and one output terminal to which each end is connected, the power is supplied only to the tuner that is receiving internal selection among the plurality of tuners, and the power that is receiving the selection is switched via the coupling element. By being coupled to the diode, the diode becomes conductive, and this conduction outputs the local oscillation signal being tuned for reception to the output terminal, and this output signal is passed through a phase comparator and a filter to select the reception station. A local oscillator switching circuit for a tuner, characterized in that the circuit supplies power to a tuning circuit and a local oscillation circuit inside the tuner.