JPH0515548U - Satellite TV tuner - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the isolation between two input terminals of a satellite broadcast receiving tuner equipped with two high frequency input terminals. [Construction] In a satellite broadcast receiving tuner having two high-frequency input terminals, a Pin diode is provided in series with a signal line so that a power supply voltage to each high-frequency amplifier of a two-input system is supplied through the Pin diode. Configure

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a satellite broadcast tuner, and more particularly to a satellite broadcast tuner capable of favorably isolating two input signals.

[0002]

[Prior Art]

 In recent years, satellite broadcasting services using geostationary satellites such as broadcasting satellites and communication satellites are rapidly advancing in various countries around the world, and various services from conventional television broadcasting to high-definition broadcasting are planned. Corresponding to this, satellite broadcast receivers are required to have multiple input terminals.

FIG. 4 shows a conventional example of an input circuit in a satellite broadcast tuner of this type. In the figure, reference numerals 1 and 2 denote choke coils which supply power to the high frequency amplifier circuits 3 and 4 from constant voltage power supplies 9 and 10 and drive switching diodes 5 and 6 via resistors 14 and 15. .. In the figure, 7 and 8 are high frequency input terminals of two systems, and 11 is an output terminal of the high frequency input circuit.

[0004]

[Problems to be solved by the device]

 In the above conventional device, when an operating voltage is applied from the constant voltage power supplies 9 and 10 to the high frequency amplification circuits 3 and 4, the high frequency amplification circuits 3 and 4 are in the (ON, OFF) or (OFF, ON) state. The circuit operates normally including the switching diodes 5 and 6.

However, in this circuit, signal leakage from the high frequency input terminals 7 to 8 and 8 to 7 occurs, and the input isolation in the high frequency signal cannot be sufficiently performed. This is because the reverse transmission characteristic from the output on the non-selected (OFF) side to the input does not drop significantly due to one stage of the switching diode and one stage of the high frequency amplifier circuit.

[0006]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention includes first and second high frequency amplifiers for two input signals, respectively, and switches the operation of the first and second high frequency amplifiers according to the switching of the input. In the satellite broadcast receiving tuner having the above high frequency input circuit, a Pin diode inserted in series to the signal line of each of the first and second high frequency amplifiers is provided, and the power source of each high frequency amplifier is set to the Pin diode. The signal is supplied via the above-mentioned structure so that two input signals are isolated.

Further, a plurality of the above-mentioned Pin diodes are provided in series.

[0008]

[Action]

 With the above configuration, the reverse transfer characteristic from the output side to the input side when the high frequency amplifier is not selected is attenuated by the amount by inserting the Pin diode in series, and as a result, the input between the respective input terminals is attenuated. You can earn isolation. Further, the drive power source for the additional Pin diode provided in series and the drive power source for the high frequency amplifier circuit can be made common.

[0009]

【Example】

 FIG. 2 is a circuit diagram of a main part of an embodiment of the present invention. In the figure, the parts corresponding to those of the conventional example shown in FIG. 2 is different from FIG. 4 shown as a conventional example in that the capacitors directly inserted in the signal line in FIG. 4 are deleted and the resistors 14 and 15 for supplying the drive voltage to the switching diodes 5 and 6 are removed. Instead, Pin diodes 12 and 13 are provided in series in each of the two signal lines, and high frequency amplifiers 3 and 4 are provided from the constant voltage power supplies 9 and 10 via the choke coils 1 and 2 and the Pin diodes 12 and 13, respectively. Is to supply power to.

Therefore, when the high-frequency amplifier 3 or 4 is not selected, the reverse transfer characteristic from the output side to the input side of this input system is lowered by the amount corresponding to the insertion of the Pin diode 12 or 13. It is possible to obtain input isolation between terminals 7 and 8.

FIG. 3 shows another embodiment of the present invention in which the same Pin diodes 12-1 and 13-1 are inserted in series with the Pin diodes 12 and 13 in FIG. According to this embodiment, since two Pin diodes are inserted in series, the attenuation of the reverse transfer characteristic from the output side to the input side becomes larger than that shown in FIG. The input isolation can be further improved.

In this embodiment, two Pin diodes are inserted in series, but a plurality of Pin diodes may be provided as needed.

In the embodiment of the present invention shown in FIGS. 2 and 3, the driving power supplies 9 and 10 for the Pin diodes 12, 12-1 and 13, 13-1 inserted in series in the signal line and the high frequency amplifier 3 are used. The drive power sources of 4 and 4 are shared to simplify the circuit configuration, and FIG. 1 illustrates the circuit configuration as the basis thereof.

[0014]

[Effect of the device]

 Since the present invention has the above-mentioned structure, the isolation between two inputs in a satellite broadcast receiving tuner having a high frequency can be greatly improved with a simple structure. In addition, since the drive power supply for the Pin diode and the drive power supply for the high frequency amplifier provided in the signal line are made common, the circuit configuration is simple and the applied voltage is reduced to the operating voltage of the high frequency amplifier by utilizing the voltage drop of the Pin diode. Can be done.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a basic configuration of an embodiment of the present invention.

FIG. 2 is a circuit diagram of a main part of an embodiment of the present invention.

FIG. 3 is a circuit diagram of a main part of another embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional example.

[Explanation of symbols]

 3,3 High frequency amplifier 5,6 Switching diode 9,10 Constant voltage power supply 12, 12-1, 13, 13-1 Pin diode

Claims (2)

[Scope of utility model registration request] 1. A first high frequency amplifier and a second high frequency amplifier are provided for two input signals respectively, and the first high frequency amplifier is provided in response to switching of the input.
And a satellite broadcast receiving tuner having a high-frequency input circuit adapted to switch the operation of the second high-frequency amplifier, wherein Pin diodes inserted in series are provided in the signal lines of the first and second high-frequency amplifiers, respectively. A tuner for satellite broadcast reception, characterized in that power is supplied to each high-frequency amplifier through the Pin diode to isolate two input signals. 2. The satellite broadcast receiving tuner according to claim 1, wherein a plurality of Pin diodes inserted in series are provided in series in the signal lines of the first and second high-frequency amplifiers, respectively. A tuner for satellite broadcasting.