JPS60162324A - Tuner device - Google Patents

Abstract

PURPOSE:To prevent the transmission of noise components produced at a point near an oscillation frequency to a mixing circuit even in case a surface wave filter element is used for an oscillation circuit, by using serial and parallel resonance circuits. CONSTITUTION:The output of an oscillation circuit 18 containing an oscillation transistor 81 and a surface wave filter 82 is supplied to a mixing circuit 17. In this case, a parallel circuit containing an inductor 92 and a capacitor 93 is used as a serial resonance circuit which has resonance with the oscillation frequency of the circuit 18. While a capacitor 95 and an inductor 96 from a serial resonance circuit which has resonance with the input signal frequency given from a BPF16. With use of such serial and parallel resonance circuits, the transmission of the noise components produced at a point near an oscillation frequency to a mixing circuit can be prevented even in case a surface wave filter element is used to an oscillating circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a tuner device using a surface wave filter element as an oscillation element, and particularly to a tuner device suitable for application to a converter tuner for CATV or the like.

[Technical background of the invention and its problems]

Conventionally, LC resonance type oscillation circuits have been widely used as local oscillation circuits in CATV converter tuners and UHF tuners. This oscillation circuit usually consists of an oscillation transistor (including a field effect transistor), a plate-shaped or linear inductor, a voltage variable capacitance diode, and the like. With this kind of oscillation circuit, it is possible to obtain a sufficiently good oscillation frequency when the frequency is relatively low.
It has already been put into practical use and is commonly used. However, with this oscillation circuit, it is difficult to obtain a high oscillation frequency due to factors such as the ratings of the elements, and the development of a new oscillation circuit is desired.

Generally, in order to obtain a high oscillation frequency, the use of a crystal oscillation oscillation circuit is being considered. It has been found that in an oscillation circuit using this surface wave filter element, because the oscillation output circuit has a high impedance, nearby noise other than the oscillation frequency is generated. For example, in an up-down converter type tuner, if the intermediate frequency signal frequency that is the output of the first converter circuit is 610 MHz, and the local oscillation frequency for the second converter is 674 MHz, the original 674MH2 component (7
) It was found that noise components in the MH2 band flowed in and degraded the performance of the mixing circuit.

[Purpose of the invention]

An object of the present invention is to provide a tuner device that exhibits excellent mixing performance without transmitting noise components near the oscillation frequency to the mixing circuit even when a surface wave filter element is used in the oscillation circuit.

[Summary of the invention]

The present invention applies a surface wave filter element to an oscillation circuit, provides a series resonant circuit that resonates with the input signal frequency between the oscillation circuit and the mixing circuit, and further includes a transmission circuit and a reference potential point between the oscillation circuit and the mixing circuit. By providing a parallel resonant circuit that resonates with the oscillation frequency of the oscillation circuit between them, noise components near the oscillation frequency can be removed, and the oscillation circuit can be constructed using nine surface wave filter elements, while being influenced by the noise component as much as possible. This was prevented.

[Embodiments of the invention]

The present invention will be described below based on specific examples.

The circuit shown in FIG. 1 is suitable for application to the present invention.
This shows an example of a down tuner, and a cable television signal sent from a cable broadcasting station is added to the terminal (10).This television signal has a frequency of 55 to 450 MH2, which is considered as a US channel. The television signal passes through a bandpass filter (11) and transmits only the necessary frequency band to the output side.
The output of 6
It is possible to switch from 60 to 1060 MH2, and select the frequency corresponding to the desired broadcast channel.

The output of this first local oscillation circuit (13) and the bandpass filter (
11) is mixed in the first mixing circuit (12) to obtain an output of 612MH2 on the output side of the mixing circuit (12). This output is supplied to a second mixing circuit (17) via a first intermediate frequency band filter (14), a first intermediate frequency amplifier circuit (15), and a first intermediate frequency band filter (16). This second mixing circuit (17) includes a second local oscillation circuit (
18) is also provided. →→→Hshii Hotaru “.The second local oscillation circuit (18) oscillates at a local oscillation frequency corresponding to the designated channel when supplying the television signal to the receiver.
When set to a channel, it oscillates at a fixed oscillation frequency of 667MH2.

Similarly, 674 MHz for 3 channels, 680 MHz for 4 channels, 690 MHz for 5 channels.
MHZ, and switching of these frequencies is not performed by general users, but is preset and shipped from the factory.

Therefore, the oscillation frequency can be changed by replacing the oscillation frequency determining element with an element having a different constant, such as an inductor or capacitor or a surface wave filter. The second local oscillation circuit (18
) is supplied to the aforementioned second mixing circuit (17), and the second mixing circuit (17) passes the oscillation output of the first intermediate band filter (16
) is mixed with the output of the second mixing circuit (17).
5575MHz if set to channel
It is possible to obtain an output signal of As mentioned above, the mixed circuit (
The output of 17) differs depending on the set channel, 61.25 MH2 for 3 channels, 67.25 MHZ for 4 channels, and 4 m huff 125 MHZ for 5 channels (7). . The output of this second mixing circuit (17) passes through a second bandpass filter (19) and an amplifier circuit (20) and is supplied to an output terminal (21) that supplies a signal to an antenna input terminal of a television receiver, for example. Cable television signals can be reproduced by setting the receiver's tuner to 2 channels, for example. The tuner device is constructed in this way, and cable television signals can be reproduced on an ordinary general television receiver.

Next, the schematic circuit configuration of each circuit part constituting this tuner device will be explained. The first mixing circuit (1
2) is configured as a balanced modulation type mixing circuit using four diodes (31x32) (33) (34), and the first local oscillation circuit (
An oscillation signal from 13) is supplied via a terminal (36). This diode (31) (32) (33)
The mixed output at (34) is made into a single output by a transformer (37), and is supplied from a terminal (38) to a first intermediate frequency band filter (14) at the next stage. Figure 3 is the first
This shows the local oscillation circuit (13), which is composed of an oscillation transistor (41), amplification transistors (42) (43), etc.
) amplifies the oscillation signal and outputs the terminal (44) (44'
) to obtain oscillation output.

The output of the terminal (44) is supplied to the aforementioned terminal (36),
The output of the terminal (44') is supplied to other utilized circuits. The collector of the oscillation transistor (41) is equipped with a resonant inductor (45) and a voltage variable capacitance that can be adjusted to achieve the desired oscillation frequency by changing the voltage. The output of the mixing circuit (12) from 38) is supplied to the input inductor (51) and tuned to the required band by the tuning inductor (52) C53) and capacitors (54) (55), and this output is connected to the junction electric field. It is supplied to the effect transistor (56). The signal amplified by this transistor (56) is transferred to the inductor (57) (58) and the capacitor (59) (6
After further band correction with the first intermediate frequency band filter (16) consisting of 0), the signal is supplied to the output terminal (61). Fifth
The figure shows the second mixing circuit (17) and the second band filter (19).
), the intermediate frequency signal that is the output of the first intermediate frequency band filter (16) is transmitted from the terminal (71) to the terminal (7
2) respectively supply oscillation outputs that are the outputs of the second local oscillation circuits (18). The signals from these terminals (71) and (72) are supplied to the first gate of a mixing field effect transistor (73), and the mixed output is sent to a filter element (74).
A filter circuit consisting of the following performs band correction and outputs only the necessary signal band to the terminal ('75). 6th
The circuit shown in the figure shows the second local oscillation circuit (18) and mixing circuit (17) that constitute the main part of the present invention, and the details will be described later, but we will briefly touch on them here (and the oscillation circuit). (18) is mainly composed of a field effect transistor (81) and a surface wave filter element (82), and obtains the above-mentioned oscillation output.

In this embodiment, the oscillation frequency can be changed by replacing the surface wave filter element (82). If the gain decreases due to the use of the surface wave filter element (82), a one-stage amplifier circuit may be inserted on the output side of the oscillation circuit (18) to correct the gain. A tuner device having such a circuit configuration is built into the housing.

An example of this is shown in Fig. 7. The same parts as those explained in Figs. 1 to 6 will be explained using the same names and numerals. 101). The inside of this frame (101) is divided approximately at the center by two parallel partition plates (102) and (103) separated from each other. For example, the part divided by the partition plate (102) and the frame (101) accommodates the up circuit part, and the part divided by the partition plate (103) and the frame (101) accommodates the down circuit part. It will be done. The space between the partition plate (102) and the frame (101) is further divided into 7 parts by six partition plates (104) to (109).
divided into several independent parcels. For convenience, this frame (101) and each partition plate (102) (104) to (10
9') into the first to seventh chambers (
110) to (116). Similarly, the partition plate (103
) and the frame (101) are further divided into six partitions by five partition plates (117) to (121').
It is divided into independent small compartments, and the divided parts are similarly called 8th to 13th chambers (122) to (127). A chassis plate (128) is provided on one side of the opening of the eighth to eleventh chambers (122) to (125'). Therefore, the 8th to 11th chambers (122) to (12
In 5), each circuit is three-dimensionally wired, and in the other rooms, a printed wiring board (not shown) incorporating a predetermined circuit is placed on the side surface in the same direction as this chassis plate (128). And the - side frame of the first chamber (110) (
101) is provided with an input terminal (10).

An output terminal (21) is provided in the negative side frame (101) portion of the thirteenth chamber (127). Similarly, various terminals (101) such as power terminals are provided on the side of the frame (101).
29) Types are provided. The first chamber (110)
The third chamber (112) is provided with a bandpass filter (11) connected to the input terminal (10), and the fourth chamber (113) is provided with a bandpass filter (11) connected to the input terminal (10).
A first local oscillation circuit (13) is arranged in the fifth local oscillation circuit (13), and a fifth
The chamber (114) is provided with an amplifier circuit portion constituting the first local oscillation circuit (13). The sixth chamber (115) accommodates a circuit such as a prescaler. 7th chamber (116)
A first mixing circuit (12) is arranged.

The output of this first mixing circuit (12) is the partition plate (102) (
The output of the mixing circuit (12) is connected to the eighth
to the chamber (122). A first intermediate frequency band filter (14) is disposed in the eighth chamber (122) and the ninth chamber (123), and these two chambers (122)
') A notch (130) is provided in the middle partition plate (118) of (123). Furthermore, the 10th chamber (124
) has a first intermediate frequency amplification circuit (15) in the eleventh chamber (
A first intermediate frequency band filter (16) is disposed in each of the chambers (125), a second local oscillation circuit (18) is disposed in the twelfth chamber (126), and a second local oscillation circuit (18) is disposed in the thirteenth chamber (127'). A second mixing circuit (17), a second band filter (19), and an amplifier circuit (20) are respectively provided, and the output of the amplifier circuit (20) is supplied to an output terminal (21).

The tuner device is configured as described above (but here, the above-mentioned second local oscillation circuit (18) and mixing circuit (17) are configured.
) will be explained in more detail with reference to FIG.

The first gate of the field effect transistor (81) for oscillation is connected to the voltage dividing resistor (84) (85) via the inductor (83).
), one end of the resistor (85) is grounded, and one end of the resistor (84) is grounded to the ground, which is the reference potential point, via the capacitor (86), and via the resistor (87). It is connected to a power supply terminal (88). The resistance (
84) (7) -m is further a transistor (81) (7
) connected to the second gate. This transistor (8
The source of 1) is grounded through a parallel circuit of a resistor (89) and a capacitor (90), and the drain (also connected to the power supply terminal (88) via an inductor (91) and a parallel circuit of an inductor (92) and a capacitor (93) in series). A feedthrough capacitor (94) is provided at this power supply terminal (88).A surface wave filter element (82) constituting this oscillation circuit (18) is connected to each inductor (83) (91). One end of the inductor (91) is connected to the mixing circuit (1) through a series circuit of a capacitor (95), an inductor (96), and an inductor (97).
7) is connected to the first gate of the field effect transistor (98). This inductor (96) and (9
A first intermediate band filter (16) is connected to the connection point of 7) via an inductor (99), and a feedthrough capacitor is connected in the connection path between this inductor (99), (96') and (97). (100) is interposed. Here, the parallel circuit of the inductor (92) and the capacitor (93) is set as a parallel resonant circuit that resonates with the oscillation frequency of the oscillation circuit (18), and the capacitor (95) and the inductor (96) are connected to the bandpass filter (16). ) is set up as a series resonant circuit that resonates with the input signal frequency from ).

Therefore, the oscillation operation is performed by the loop of the surface acoustic wave filter element (82) interposed between the drain of the oscillation transistor (81) and the first gate.

This oscillation frequency is set to 674MH2, for example.

This oscillation frequency is 51Q, which resonates with the parallel resonant circuits (92) and (93) and is a source of nearby noise.
The values of the inductor (92) and capacitor (93) of the resonant circuit are selected so that the M HZ is sufficiently attenuated. The oscillation output that resonates in this resonant circuit is connected to a capacitor (95)
Supplied to the series resonant circuit of the inductor (96).
−゛−− Kashichi→→H→This series resonant circuit is a bandpass filter (16)
Series resonance occurs at the input signal frequency of 674 MH2 supplied from 610 MHZ ``C''
By selecting an IC of 1/(2yCs 61G·ICp-Ce5) or more, the 610 MHz component is removed and only the necessary 674 MH2 signal is supplied to the mixing circuit (17). Therefore, the output of the oscillation circuit (18) can supply the originally required 674 MHz signal to the mixing circuit (17), and the 610 MHz signal from the bandpass filter (16).
The required 54M is mixed with the H2 input signal by the mixing circuit (17).
H2 signal can be obtained.

Note that the capacitor (93) constituting the parallel resonant circuit may use a printed circuit board or a stray member between patterns, and the lead inductor components of the capacitor (95) may be used individually or individually as the inductor (96) of the series resonant circuit. If possible, and if a resonant circuit can be constructed using these components in two equivalent ways, the effects of the present invention can be produced.

〔Effect of the invention〕

As described above, according to the present invention, by using a surface wave filter element as an oscillation element, not only can a high oscillation frequency be obtained, but also the high impedance of the oscillation output circuit caused by using the surface wave filter element can be obtained. Neighboring noise that generates frequencies near the oscillation frequency can also be reduced before being supplied to the mixing circuit, so the oscillation circuit output can have the desired frequency value, improving the mixing circuit's output characteristic 'uQ. Therefore, it is possible to provide a chi-21 device that can sufficiently withstand practical use.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing the circuit configuration of a tuner device according to the present invention, FIGS. 2 to 6 are circuit diagrams for explaining each circuit of the circuit configuration shown in FIG. 1, and FIG. 2 is a perspective view showing a tuner housing for accommodating the circuit configuration shown in FIG. 1. FIG. 17...Mixing circuit 18...Oscillating circuit 81...Oscillating transistor 82...Surface wave filter element 92...For parallel resonant circuit Inductor 93 ---
... Parallel resonant circuit capacitor 95 ... Series resonant circuit capacitor 96 ... Series resonant circuit inductor Patent attorney Kensuke Norichika (and one other person)
Figure 3 A4 Figure 4 Figure 5 c0 Figure 6 front 7 Figure 129 +14

Claims (1)

[Claims] An oscillation circuit configured with an oscillation transistor and a surface wave filter element, a mixing circuit that mixes the output of this oscillation circuit with an input signal and obtains an output signal whose frequency has been converted into an output, and a circuit between this mixing circuit and the oscillation circuit. A series resonant circuit that is interposed in a transmission circuit and resonates with the input signal frequency, and a parallel resonant circuit that is connected between the transmission circuit and a reference potential point between the oscillation circuit and the mixing circuit and resonates with the oscillation frequency of the oscillation circuit. tuner device.