JPH0310246B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention uses a double superheterodyne system (hereinafter referred to as the double super system) to
This invention relates to a tuner for TV reception that receives signals.

Conventional configuration and its problems In recent years, a double super system equipped with two local oscillators and two mixers has been developed as a receiving system that receives a wide frequency band and does not require tracking adjustment for each channel. There is Chiyuna. This method enables wideband reception as the first intermediate frequency is selected higher than the upper limit of the received signal frequency, and has the advantage of reducing the effects of interference waves. Circuit design and structural design become difficult. In particular, this method has the disadvantage that interference will rapidly increase unless coupling between the two local oscillators is avoided as much as possible.

Hereinafter, a conventional double super type tuner will be explained in more detail with reference to the drawings.

FIG. 1 shows the block configuration of a conventional double super type tuner, and FIG. 2 shows a perspective view of the casing of the conventional double super type tuner.
In the drawings, the same reference numerals are used to denote the same functions.

First, the TV signal is input from RF input terminal 1 and the RF
The signal is applied to the amplifier circuit 2, and after being made to an appropriate signal level by the filter circuit, AGC circuit, and amplifier, it is applied to the first mixer 3, and the frequency is set by the first local oscillator 4 (oscillation frequency F _L1 ). The signal is converted into a first intermediate frequency signal (frequency IF ₁ ). The signal is guided to a first intermediate frequency amplification circuit 5, passes through an amplifier and a bandpass filter, and removes the required band characteristics and interference waves, and is then added to a second mixer 6, where it is applied to a second local oscillator 7 (oscillation frequency F). _L2 ), the frequency is converted into a second intermediate frequency signal (frequency IF ₂ ), which is applied to the second intermediate frequency amplification circuit 8, and further amplified by a filter and an amplifier to achieve strict band characteristics, and then output. It is sent from terminal 9.

In the above configuration, as shown in FIG. 2, each circuit section is basically shielded by a shielding plate. That is, the RF amplifier circuit section 12, the first mixer section 13 including the first local oscillator, the second mixer section 16 including the second local oscillator, the second intermediate frequency amplifier circuit section 18, etc. A shielding plate is provided to prevent such coupling.

Now, if the frequency of the TV signal is F _RF , then the first
In the mixer, F _L1 −F _RF = IF ₁ , and the second
In the mixer, IF ₁ −F _L2 =IF ₂ . When there is a coupling between the first local oscillator 4 and the second local oscillator 7 as described above, the frequency relationship is F _L1 ~ _{F L2}
= F _RF + IF ₂ , which enters the TV signal frequency band as an interference wave. Therefore, as shown in Figure 2, a double shielding space 20 is provided to prevent coupling, but each circuit is lined up in a plane. Therefore, since the shielding plate (lid part) that shields the opening surface is common, the structure has to be complicated in order to reduce the coupling.

Furthermore, as mentioned above, in the double super system, since the first intermediate frequency is selected higher than the upper limit of the received signal frequency band, the second
Since the frequency up to mixer 6 is in the gigahertz band, the circuit design technology is also sophisticated, and in particular, it is necessary to take a connection method that takes into account shielding and impedance matching in the connections between each circuit, and in the above configuration, the characteristics This was the cause of variations in the results.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention configures a circuit section that operates in a high frequency band in a separate housing that is easy to handle, and also prevents coupling between the first and second local oscillators.
In addition, the present invention provides a tuner that has a good shielding effect and realizes circuit connections with good impedance characteristics.

Configuration of the Invention The present invention includes a wideband amplifier that amplifies a TV signal;
A first intermediate frequency signal is obtained by varying the output frequency of the broadband amplifier and converting the frequency.
a local oscillator and a first mixer; a second local oscillator and a second mixer; a second local oscillator and a second mixer; the output is amplified by a first intermediate frequency amplifier including a bandpass filter and then frequency-converted; a second intermediate frequency amplifier for amplifying the frequency as a second intermediate frequency amplifier; a first mixer comprising a double-sided printed wiring board configured to electrically isolate the two circuit parts, one side of which is mainly grounded, and the other side of which includes the first local oscillator; a first substrate having a circuit configured with a stripline circuit, and a second substrate having a circuit configured with a stripline circuit, a second mixer unit including the second local oscillator;
The first substrate and the second substrate sandwich an electrically shielding conductor plate, and a third substrate forms the input and output parts of a bandpass filter that constitutes a part of the first intermediate frequency amplifier. The above object is achieved by sandwiching the printed wiring board between the two substrates and forming a signal path using through holes in the third substrate.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is an exploded perspective view of a tuner in one embodiment of the present invention.

In FIG. 3, the housing A is a cavity 30 of the housing B.
It is a chuyuna that is inserted into the . The housing A includes a housing part 35 forming the first mixer part 13, a housing part 36 forming the second mixer part 16', and a band wave generator of the first intermediate frequency amplification circuit part 5. It is connected to the housing part 37. On the other hand, case B is the RF amplifier circuit section 1.
2 and a second intermediate frequency amplification circuit section 18 are formed therein.

Hereinafter, with reference to FIG. 4, the configuration of the casing A shown in FIG. 3 will be explained in more detail. FIG. 4 shows the configuration of the casing A, with FIG. 4A being a plan view thereof, and FIG. 4B being an elevational view thereof.

In FIGS. 4A and 4B, 30a is a housing that houses the first mixer section 13 and the second mixer section 16,
One side has an opening for connection to the input/output section of the band wave generator in the first intermediate frequency amplification circuit section 5, and a part of the printed wiring board 37a constituting the band wave wave generator protrudes from this opening. There is. 35
A is a printed wiring board in which a first mixer section 13 including a first local oscillator 4 is formed into a stripline circuit with one side grounded, and a second mixer section 16' including a second local oscillator 7 is connected to a stripline circuit. It is housed in a housing 30a with a shielding plate 30c sandwiched between a printed wiring board 36a on which a circuit is formed using a lipline and one side of which is grounded, and an input/output protrusion 37a' of the printed wiring board 37a is sandwiched between both sides. I'm here. In addition, the input and output of the band wave device is connected to a printed wiring board 3.
It is electrically connected to the output section and input section of 5a and 36a. The connected portion will be further enlarged and explained below.

FIG. 5A is an enlarged partial cross-sectional view taken along line A-A' in FIG.

In FIG. 5A, 36c is the printed wiring board 3
The ground pattern 6a, 36i, is a through hole provided in the printed wiring board 36a, and is connected to the pattern 37c of the output section of the printed wiring board 37a through the through hole. 35h is a through hole provided in the printed wiring board 35a, which connects the ground surface 30c and the pattern 35c provided on the circuit surface, shields the connection portion 36i, and can be designed to have any stable impedance. It is configured as follows.

On the other hand, FIG. 5B is an enlarged partial cross-sectional view taken along line BB' of FIG. 4A.

Reference numeral 35i denotes a through hole provided in the printed wiring board 35a, which is connected to the pattern 37c to transmit signals. Reference numeral 36h is a through hole for connection to the ground plane, which is connected to the pattern 36c to provide a shielding effect and stable characteristic impedance.

FIG. 5C is an enlarged partial cross-sectional view taken along the line C-C' of FIG. 4A.

The output section 35i of the printed wiring board 35a and the input section 36i of the printed wiring board 36a are configured to be separated by opposing substrates and shielding plates.

Effects of the Invention As described above, the tuner of the present invention can reduce the coupling between the first and second local oscillators without providing extra space, simplify the connection between each circuit part, and provide stable impedance. It is possible to construct a double super type tuner that can be connected, is easy to assemble, and has stable performance, and has great effects in terms of performance, quality, and cost.

[Brief explanation of the drawing]

Fig. 1 is a block wiring diagram of a conventional double super type tuner, Fig. 2 is an exploded perspective view of the same double super type tuner, Fig. 3 is an exploded perspective view of a tuner in an embodiment of the present invention, and Fig. 4A. is a plan view of the main part of the same tuner, FIG. 4B is an elevational view of the main part of the same tuner, and FIGS. 5A, B, and C are sectional views of FIG. 4, respectively. 2...RF amplifier circuit, 3...first mixer, 4
...First local oscillator, 5...First intermediate frequency amplification circuit, 6...Second mixer, 7...Second local oscillator, 8...Second intermediate frequency amplification circuit, 12...RF
Amplifier circuit section, 13... first mixer section, 16...
Second mixer section, 18... Second intermediate frequency amplification circuit section, 30a... Shielding casing, 30c... Shielding plate, 3
5a...Printed wiring board, 35h, 35i...Through hole, 36a...Printed wiring board, 36
h, 36i...through hole, 37...shielding casing, 37a...printed wiring board, 37i...through hole.

Claims (1)

[Claims] 1. A wideband amplifier that amplifies the TV signal; the output frequency of the wideband amplifier and the signal obtained by varying the frequency of the first local oscillator are mixed to produce a first intermediate frequency signal; a first mixer for converting;
a second local oscillator and a second mixer that amplify the output with a first intermediate frequency amplifier including a bandpass filter and then convert the frequency; and a second intermediate frequency amplifier that amplifies the output as a second intermediate frequency signal. A first mixer section including the first local oscillator and a second mixer section including the second local oscillator are each configured on a printed wiring board with one side grounded, and the two circuit sections are connected to each other. The first mixer section including the first local oscillator is configured with a stripline circuit on the other side of a double-sided printed wiring board that has an electrically isolated double structure and one side is mainly grounded. A second mixer section including a first substrate and the second local oscillator is a second substrate configured with a stripline circuit, and the first substrate and the second substrate are electrically shielded conductor plates. and a third substrate printed wiring board that forms the input and output parts of the bandpass filter constituting a part of the first intermediate frequency amplifier, and a signal path is formed by a through hole in the third substrate. . 2. Claim 1, characterized in that the first substrate and the second substrate form a shielding pattern on a substrate facing the substrate connected to the input section and the output section of the third substrate. Chuyuna described in item 1.