JPS61192131A - Tuner - Google Patents

Abstract

PURPOSE:To provide the high eliminating capability to cross modulation, secon dary intermodulation disturbance and tertiary intermodulation disturbance by using a double-balanced mixing circuit comprising 4 diodes for a VHF mixer, using a single-balanced mixer comprising two diodes for a UHF mixer and providing an intermediate frequency amplifier between an intermediate frequency filter at the output of the single balanced mixing circuit and a signal switching circuit. CONSTITUTION:The double-balanced mixing circuit 17 comprising 4 diodes is used for a VHF mixer and the single-balanced mixing circuit comprising 2 diodes is used for the UHF mixer, and the output of the said two mixing circuits is provided with inpedent intermediate frequency passing filters 11, 19, each filter output signal passes through a signal switching circuit 12 comprising 1 circuit 2 contacts and is given to a common intermediate frequency amplifier 20.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a tuner for single-super television.

BACKGROUND ART FIG. 10 shows a basic functional block diagram of a conventional tuner. In the figure, 1 is an antenna input terminal, 2 is a distributor, 3.4 is a 0-input tuning circuit for VHF and UHF bands, and 5.
6 is the same RF amplifier and has RF input terminals 5a and 6a. 7 and 8 are also interstage double-tuned circuits, 9 is a mixing circuit, 10 is an oscillation circuit, 11 is an intermediate frequency passing P-wave device, 12
is a signal switching circuit, 13 is a mixing circuit (IF amplifier circuit), 1
4 is an oscillation circuit, 16 is an output tuning circuit, and 16 is an intermediate frequency output terminal.

Problems to be Solved by the Invention To explain this problem particularly from the perspective of interference rejection ability, firstly, VHF mixers have conventionally used bipolar transistors, MOSFETs, and even monolithic IC multipliers. However, these are all caused by adjacent intermodulation interference and second-order intermodulation interference due to mixer second-order distortion.
IM2), third-order intermodulation interference due to third-order distortion ()Ms)
However, sufficient performance could not be obtained.

Second, bipolar transistors, diodes, and the like have been conventionally used in UHF mixers, but these also have the same performance problems as the VHF mixers.

Thirdly, regarding RF amplifiers, both UHF and VHF require improvement in distortion characteristics, especially IMs.

In recent years, the market demand for improved performance of tuners against the above interference has been increasing, and with the background of laws being enacted as exemplified by the new FTZ standard in Germany, it is possible to The development of a tuner with the ability to eliminate interference has been awaited.

The present invention has been made in view of the above circumstances.

Means for Solving the Problems In order to solve the above problems, the present invention provides a singles-/
This is a double-balanced type electronic tuner for television that uses a double-balanced mixing circuit consisting of four diodes for the mixer in the UHF section, and a single-balanced mixer consisting of two diodes for the mixer in the UHF section. It was there.

In addition, independent intermediate frequency passing F wave filters are provided at the outputs of the two mixing circuits, and after passing the output signals of each filter through a signal switching circuit with one circuit and two contacts, a common intermediate frequency amplifier circuit is provided. In addition, independent emitter holocou circuits are provided in front of the RF signal input terminals of the two mixing circuits. A local oscillation output amplifier is provided.

Further, an intermediate frequency amplifier is provided between the output intermediate frequency F-wave generator of the single-balanced mixing circuit and the signal switching circuit. Further, a gain control circuit made of a PIN diode is provided at the first stage of the antenna input terminal, and then connected to the UHF/VHF distribution circuit.

Function: This configuration provides high rejection capability against adjacent cross-modulation, IM2, and IMs interference.Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Note that the same parts as in FIG. 10 are given the same numbers.

The embodiment shown in FIG. 1 uses a double-balanced mixer circuit 17 consisting of four diodes for the VHF mixer, and a single-balanced mixer circuit 17 consisting of two diodes for the UHF mixer. Independent intermediate frequency passing F-wave filters 11 and 19 are provided at the outputs of the two mixing circuits, and after passing the respective filter output signals through a signal switching circuit 12 with one circuit and two contacts, a common intermediate frequency amplifier is provided. This is an example in which it is combined with 20. 21 is an oscillation circuit. In the embodiment shown in FIG. 2, independent emitter hollow circuits 22 are provided in front of the RF signal input terminals of the double-balanced mixing circuit 17 and the single-balanced mixing circuit 18, respectively. In the embodiment shown in FIG. 3, independent amplifiers 24 are provided in front of the local oscillation signal input terminals of the double balanced mixing circuit 17 and the single balanced mixing circuit 18. This is an example in which .25 is provided.

The embodiment shown in FIG. 4 is an embodiment in which an intermediate frequency amplifier 26 is provided between the intermediate frequency p-wave generator 11 of the single-balanced mixing circuit 18 and the signal switching circuit 12.

In the embodiment shown in FIG. 5, after providing a gain control circuit 27 made of a PIN diode at the first stage of the antenna input terminal 1,
6 to 9 show specific circuits of main parts, and FIG. 6 shows a double-balanced type circuit consisting of four diodes 28. 031 is an RF signal input terminal, 32 is a local oscillation input terminal, and 33 is an intermediate frequency output terminal. Figure 7 shows a single-balanced type circuit consisting of two diodes 34. A mixing circuit is shown, where 36 is a grounding capacitor and 36 is a balun.

FIG. 8 shows an embodiment of the emitter follower circuit 22 of the VHF section, and 37 is a VHF power supply terminal.

FIG. 9 shows an embodiment of the emitter follower circuit 23 and the intermediate frequency passing F wave device 11 in the UHF section.

As mentioned above, VHF/lJ)! By using a balanced mixing circuit for each F mixer, it is possible to realize a mixing circuit that has sufficient performance against the adjacent cross modulation and IM2 and IM3 interference, which have been problems in the past.
By providing a common intermediate frequency amplifier for F, it is possible to realize a circuit design with an optimal high interference rejection ability as an intermediate frequency amplifier.

Furthermore, by providing the emitter follower circuit,
The low RF input impedance of the balanced mixing circuit can be converted to a high level, the selectivity between stages can be improved, and the performance against image interference can be secured to be equal to or higher than that of the conventional one, and the local oscillation amplifier is provided. By ensuring a high injection level essential for a diode balanced mixed circuit, it is possible to maintain a mixed circuit with high interference rejection ability, and furthermore, the output By providing an intermediate frequency amplifier between the signal switching circuit and the signal switching circuit, it is possible to correct the lack of gain (approximately 5 dB) in the UHF section, and to realize a tuner having the same gain for UHF and VHF.

Furthermore, by providing a gain control circuit consisting of a PIN diode at the first stage of the antenna input terminal, the distortion characteristics of IM3, which was a problem with RF amplifiers, have been improved, resulting in a TV tuner with excellent interference rejection ability. be able to.

Effects of the Invention As described above, according to the present invention, adjacent cross modulation, IM2,
It is possible to provide sufficient performance against IM3 interference.

[Brief explanation of the drawing]

1 to 6 are block diagrams showing the configuration of a tuner according to an embodiment of the present invention, FIG. 6 is a circuit diagram of a diode double-balanced mixed circuit of the same block, and FIG. 7 is a diode single-balanced mixed circuit of the same block. The circuit diagram of the mixed circuit, Figure 8, is the same (
The circuit diagram of the emitter follower circuit on the VHF side, Figure 9, is the same (the circuit diagram of the emitter follower circuit on the UHF side, Figure 10)
The figure is a block diagram of a conventional tuner. 1...Antenna input terminal, 2...Distributor, 6゜6...RF amplifier circuit, 11.19...
...Intermediate frequency passing F wave device, 12... Signal switching circuit, 17... Double balanced mixing circuit, 18.
...Single balanced mixing circuit, 20...Intermediate frequency amplifier, 22.23...Emitter follower
Circuit, 24.25...Amplifier, 26...
・Intermediate frequency amplifier, 2]...Gain control circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 6
Fig. 31 Fig. 7 i8 Fig. 9

Claims (6)

[Claims] (1) A single super system, in which a double-balanced mixer consisting of four diodes was used as the mixer in the VHF section, and a single-balanced mixer consisting of two diodes was used in the mixer in the UHF section. tuner. (2) In addition to providing independent intermediate frequency pass filters for the outputs of the two mixing circuits, the output signals of each filter are passed through a signal switching circuit with one circuit and two contacts, and then sent to a common intermediate frequency amplifier. A tuner according to claim 1, as combined. (3) The tuner according to claim 1, wherein independent emitter follower circuits are provided in front of the RF signal input terminals of each of the double balanced mixing circuit and the single balanced mixing circuit. (4) The tuner according to claim 1, wherein independent amplifiers are provided in front of the local oscillation signal input terminals of each of the double-balanced mixing circuit and the single-balanced mixing circuit. (5) The tuner according to claim 1, wherein an intermediate frequency amplifier is provided between the output intermediate frequency filter of the single-balanced mixing circuit and the signal switching circuit. (6) The tuner according to claim 1, wherein a gain control circuit made of a PIN diode is provided at the first stage of the antenna input terminal and then coupled to the UHF/VHF divider.