JP2000286728A - Tuner unit adopting direct conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress crosstalk between an RF circuit and a channel selection circuit of a tuner adopting a direct conversion system with a simple and inexpensive configuration. SOLUTION: An RF circuit, a base band circuit and a channel selection circuit are formed on a tuner board 44, a metal-made chassis 46 shields the RF circuit or the channel selection circuit, input output circuit patterns 47 connecting the tuner board 44 and a set board 45 and provided to the tuner board 44 are extended to one end of the tuner board 44, ends of the input output circuit patterns 47 are exposed, the tuner board 44 is set to the set board 45 in an orthogonal direction, ends of the input output circuit patterns 47 and wiring patterns 49, 49,... extended up to positions opposed to the ends are formed on the set board 45, and the ends of the input output circuit patterns 47 and ends of the wiring patterns 49 opposed to the ends of the input output circuit patterns 47 are soldered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct conversion type tuner unit for use in a digital satellite broadcast receiver for receiving digitally compressed and modulated information such as video, audio and text.

[0002]

2. Description of the Related Art A conventional satellite broadcasting receiver generally employs a heterodyne system for performing two-stage frequency conversion.
FIG. 5 is a block diagram showing a conventional example of a front end section of a receiver according to this method. The front end unit shown in FIG. 5 includes a connector 1 for introducing a signal from an LNB (Low Noise Block) to a receiver, a high-pass filter 2 for suppressing signals other than an input signal, an RF amplifier 3, and the high-pass filter 2. And an RF attenuator 4, a variable band-pass filter 5 for suppressing an input signal other than a desired signal, and a mixer for mixing the desired signal with a local signal and converting the frequency to an IF band. 6 and an RF circuit 31 composed of the RF attenuator 4, the variable bandpass filter 5 and the mixer 6.
A first IF amplifier 7, a SAW filter 8 for suppressing signals (noise, adjacent channel signals, spurious) other than a desired wave in the IF band, a first IF amplifier 7 and a SA
An IF circuit 32 composed of a W filter 8 and a second IF
An amplifier 9, an IF variable amplifier 10, a quadrature detector (I) 11 and a quadrature detector (Q) 12 for restoring an IF signal into two baseband signals orthogonal to each other, a baseband amplifier (I) 13 and a base Band amplifier (Q) 1
4, a baseband low-pass filter (I) 15 and a baseband low-pass filter (Q) 16 for suppressing unnecessary spurious in each baseband, and a second local oscillation circuit 22 for outputting a baseband demodulation reference signal. ,
90 ° phase shifter 21 and AGC drive circuit 23, second IF amplifier 9, IF variable amplifier 10, quadrature detector (I) 11, quadrature detector (Q) 12, baseband amplifier (I) 13, Baseband amplifier (Q) 14, baseband lowpass filter (I) 15, baseband lowpass filter (Q) 16, 90 ° phase shifter 21 and second
Baseband circuit 33 composed of local oscillation circuit 22
, A first local oscillation circuit 17, a tank circuit 18, a PL
It comprises an L synthesizer 19, a loop filter 20, and a tuning circuit 34 including the first local oscillation circuit 17, the tank circuit 18, the PLL synthesizer 19 and the loop filter 20.

FIG. 6 shows a configuration of a circuit arrangement of a front end portion of the receiver shown in FIG. In FIG. 6, 4
1 is a substrate on which the circuit shown in FIG. 5 is mounted. The circuit shown in FIG. 5 mounted on the board 41 is connected by a copper foil pattern printed on the board 41. The periphery of the substrate 41 is covered with a metal chassis 40, and the RF circuit 30, the RF circuit 31, the IF circuit 32, the baseband circuit 33, and the tuning circuit 34 are electrically connected to each other by a shield plate 42. It is constituted so that it may be shielded.

FIG. 7 shows a configuration in which the above-described tuner board 41 is mounted on a set board 45. The tuner board 41 is configured to completely cover the periphery of the tuner board 41 so as to be shielded by the chassis 40, and the metal input / output terminals 24, 24,... An opening 25 is provided for insertion without contact. The substrate 41 has openings 26, 26 through which the metal input / output terminals 24, 24,.
Are provided, and openings 27, 27,... Through which the metal input / output terminals 24, 24,.
Is provided.

The metal input / output terminals 24, 24,...
The openings 26, 26,..., 25 and 27, 27,.
, One end of each of the metal input / output terminals 24, 24,... Is electrically connected to a predetermined location of the tuner substrate 41, and the other end is electrically connected to a predetermined location of the set substrate 45, respectively. At the same time, the tuner substrate 41 shielded by the chassis 40 is fixed to the set substrate 45. In this case, the metal input / output terminals 24, 24,.
The connection with the set board 45 is made by soldering. Reference numeral 28 denotes a wiring pattern formed on the surface of the set substrate 45.

[0006]

In a receiver employing a heterodyne system, unnecessary spurious is generated in a baseband signal by two mixers, and the input sensitivity is reduced. The spurious of the second local oscillation will be described as an example of the spurious. The second local oscillation frequency serving as a reference frequency for orthogonal detection of an IF signal is usually 479.5 MHz. If the doubled harmonic (479.5 MHz × 2 = 959 MHz) radiates a large amount to the RF circuit, a spurious is generated at 9 MHz in the baseband when f _RF = 950 MHz is selected. A filter for suppressing the spurious is required, and the shielding structure of the chassis is complicated to shield the radiation of the local signal.

On the other hand, the direct conversion method is
The direct frequency conversion between the RF signal and the baseband signal eliminates the IF band signal processing circuit. In addition, since the spurious which existed in the heterodyne method does not occur in principle, a filter for suppressing this is not required. . However, as a unique problem of the direct conversion method, there is crosstalk between the RF signal and the local signal,
This may cause the input sensitivity of the receiver to decrease.

According to the present invention, in a tuner unit of a direct conversion system, an RF signal and a local signal are effectively shielded by a simple and inexpensive shield structure. According to the above prior art, the connection between the tuner board and the set board is made by metal input / output terminals, so that the number of components is increased by using this, and the metal input / output terminals are used as the tuner board, the chassis and the set. It is necessary to perform an operation of inserting through the opening provided in the substrate and electrically connecting both ends thereof to predetermined portions of the tuner substrate and the set substrate, resulting in a problem that the number of manufacturing steps is increased and the cost is increased.

Further, when an external force is applied to the metal input / output terminal during or after the manufacture of the tuner unit, there is a problem that the metal input / output terminal is bent. An object of the present invention is to reduce the manufacturing cost of a tuner unit, reduce inconveniences, and improve productivity.

[0010]

According to the present invention, in order to achieve the above object, according to the direct conversion type tuner unit of claim 1, an RF circuit for performing RF signal processing of an input signal, and an RF circuit for the RF circuit. A baseband circuit that outputs a baseband signal by quadrature detection of an output;
In a direct conversion type tuner unit for digital satellite broadcasting constituted by a tuning circuit for selecting a specific channel of an input signal, a chassis for shielding at least one of the RF circuit and the tuning circuit formed on a tuner substrate The end of the input / output circuit pattern formed on the tuner substrate for connecting to the set substrate is formed so as to extend and expose on one end surface of the tuner substrate, and the tuner substrate is set on the set substrate. When aligned in the orthogonal direction, the wiring pattern is formed on a set substrate such that a wiring pattern for connecting the input / output circuit pattern is located at a position facing an end of the input / output circuit pattern, The two patterns facing each other are electrically connected with the two substrates aligned in a direction orthogonal to each other. Characterized in that so as to physically fixed.

The direct conversion type tuner unit according to claim 2 is the direct conversion type tuner unit according to claim 1,
The end of the input / output circuit pattern is formed in a substantially V-shaped protrusion formed on the tuner substrate, and the tip of the input / output circuit pattern is narrowed. When the tuner substrate and the set substrate are aligned in a direction perpendicular to the set substrate, An opening is formed in which the V-shaped protrusion is fitted, and a wiring pattern facing a corresponding end of the input / output circuit pattern extending on the protrusion when the protrusion is fitted in the opening is set on the set board. And an end portion of the input / output circuit pattern and an end portion of the wiring pattern on the set board are electrically connected and physically fixed.

According to the first aspect of the present invention, when the tuner substrate is set at a predetermined position in a direction orthogonal to the set substrate, an input / output circuit pattern for connecting to a wiring pattern of the set substrate formed on the tuner substrate. Are exposed at positions facing the ends of the corresponding wiring patterns formed on the set substrate. Therefore, when both ends of the input / output circuit pattern and the wiring pattern facing each other in this state are fixed by soldering, the connection between the tuner board and the set board can be performed by one soldering without using a separate connection conductor. As well as fixing the tuner board and the set board at the same time,
Since the number of parts is reduced and the number of soldering points is reduced, the input / output impedance can be reduced, and the number of working steps can be reduced.

According to the second aspect of the present invention, when the projection provided on the tuner substrate is fitted into the opening provided on the set substrate corresponding to the projection, the positions of the tuner substrate and the set substrate are adjusted. It is accurately and firmly fixed, and at the same time, the input / output circuit pattern of the tuner board and the corresponding wiring pattern on the set board are fixed at positions facing each other.
Therefore, if both ends of the input / output circuit pattern and the wiring pattern facing each other are fixed by soldering in this state, the tuner substrate and the set substrate can be connected and both substrates can be firmly fixed.

[0014]

FIG. 1 is a block diagram of a direct conversion type tuner unit according to the present invention. Parts corresponding to the conventional example are denoted by the same reference numerals. The direct conversion type tuner unit of the present invention shown in FIG. 1 includes a connector 1 for introducing a reception signal from an LNB to a receiver, a high-pass filter 2 for suppressing signals other than an input signal, and a first RF amplifier 3. , An RF attenuator 4, a variable band-pass filter 5 for suppressing an input signal other than a desired wave, the high-pass filter 2, a first R
An RF circuit 37 including an F-amplifier 3, an RF attenuator 4 and a variable band-pass filter 5, a second RF amplifier 35, an RF variable amplifier 36, and mixing a desired signal in the RF band with a local signal to directly base the signal; Quadrature detector (I) 11 and quadrature detector (Q) for restoring band signal
12, a baseband amplifier (I) 13 and a baseband amplifier (Q) 14, a baseband low-pass filter (I) 15 and a baseband low-pass filter (Q) for suppressing unnecessary spurious in each baseband band.
16; a 90 ° phase shifter 21;
AGC drive circuit 23, second RF amplifier 35, RF variable amplifier 36, quadrature detector (I) 11, quadrature detector (Q) 12, baseband amplifier (I) 13,
A baseband circuit 38 including a baseband amplifier (Q) 14, a baseband lowpass filter (I) 15, a baseband lowpass filter (Q) 16, a 90 ° phase shifter 21, and a first local oscillation circuit 17, and a tank Circuit 18, a PLL synthesizer 19, a loop filter 20, the tank circuit 18, the PLL synthesizer 1
Tuning circuit 39 composed of the filter 9 and the loop filter 20
And

FIG. 2 shows a configuration of an embodiment of a direct conversion type tuner unit of the present invention. In FIG. 2, reference numeral 44 denotes a tuner board on which the RF circuit 37, the baseband circuit 38, and the tuning circuit 39 shown in FIG. 1 are mounted. Each circuit is formed by a copper foil pattern printed on the tuner board 44. Connected. Reference numeral 43 denotes a metal chassis that shields the RF circuit 37. In the embodiment shown in FIG.
7 is covered and shielded by a metal chassis 43 to reduce crosstalk with the tuning circuit 39. However, the RF circuit 37 is not provided with a chassis.
Even if the tuning circuit 39 is covered with a chassis and shielded, the crosstalk between the two circuits can be similarly reduced, and a drop in input sensitivity can be prevented.

(Embodiment 1) FIG. 3 shows a tuner board 44 on which an RF circuit 37, a baseband circuit 38 and a tuning circuit 39 shown in FIGS.
FIG. 5 is an exploded perspective view showing a mounting method when mounting is performed. Although not shown on the tuner substrate 44, the above R
An F circuit 37, a baseband circuit 38, and a tuning circuit 39 are mounted. Either the RF circuit 37 or the tuning circuit 39 is formed inside a metal chassis 46, and the RF circuit 37 or the tuning circuit 39 is formed. The other of the tuning circuit 39 and the baseband circuit 38 are formed outside the chassis 46.

The input / output circuit patterns 47, 47,... On the tuner board 44 for connecting each circuit formed on the tuner board 44 to each circuit formed on the set board 45.
Are formed so as to extend to one end surface of the tuner substrate 44, and the input / output circuit patterns 47, 47,... Are exposed near this end surface.

On the other hand, reference numeral 48 denotes an opening provided in the set substrate 45. When the tuner substrate 44 is mounted in a direction perpendicular to the set substrate 45, the tuner substrate 4
4 is fitted into the opening 48, and the tuner substrate 4
4 is positioned with respect to the set substrate 45. 49, 4
9,... Are wiring patterns formed on the set board side for connecting the set board 45 and the tuner board 44;
The ends of the wiring patterns 49, 49 ... extend to the opening 48, and the tuner substrate 44 and the set substrate 45
Are formed so that those corresponding to the predetermined input / output circuit patterns 47, 47,... Formed on the tuner substrate 44 face exactly.

Therefore, the end face of the tuner board 44 where the input / output circuits 47, 47,.
8, the tuner substrate 44 becomes the set substrate 4
, Formed on the tuner substrate 44, and the vicinity of the ends of the input / output circuit patterns 47, 47,... Formed on the ends of the corresponding predetermined wiring patterns 49, 49,. .. Are soldered to connect the input / output circuit patterns 47, 47,... And the corresponding wiring patterns 49, 49,.
Is fixed.

Are cutouts for taking out the input / output circuit patterns 47 formed on the chassis 46 to the outside of the chassis 46. Although not shown, the chassis 46 is connected to a wiring pattern 49 on the set board 45 via an input / output circuit pattern 47.

(Embodiment 2) FIG.
FIG. 14 is an exploded perspective view showing another method of attaching 4 ′ to the set board 45. 4, parts corresponding to those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. In the embodiment shown in FIG. 4, the set substrate 45 of the tuner substrate 44 '
The input / output circuit patterns 47, 4
Are formed to the tip end, and the shapes of the projections 51, 51,... Are formed in a substantially V-shape in which the width becomes narrower toward the tip. On the set board 45 side,
An opening 5 into which each of the protrusions 51 is fitted.
When the protrusions 51, 51,... Corresponding to the openings 52, 52,... Are fitted, the tuner substrate 44 ′ is firmly positioned with respect to the set substrate 45. To do. At this time, the input / output circuit patterns 47, 47,... Are positioned at the leading ends of the corresponding predetermined wiring patterns 49, 49,.
The wiring patterns 49, 49,.
... to the edge.

Therefore, the openings 52, 5
The projections 51, 51,.
Are fitted, the tuner substrate 44 ′ becomes the set substrate 45.
Of the tuner board 44 ', and the input / output circuit patterns 47, 47,.
Are positioned at positions facing the ends of the corresponding wiring patterns 49, 49,. Therefore, the input / output circuit patterns 47, 47,.
By soldering the opposing portions of 9,..., Both patterns can be electrically connected, and at the same time, the tuner substrate 44 ′ can be fixed to the set substrate 45.

The wiring patterns 49, 4 provided on the set substrate 45 side in both the embodiments shown in FIGS.
Are extended to the inner surface of the opening 48 or the openings 52, 52,.
Connections with 7,... Can be made stronger.

[0024]

According to the present invention, as described above, only one of the RF circuit and the tuning circuit provided on the tuner substrate is shielded to effectively suppress crosstalk between the RF circuit and the tuning circuit. A decrease in input sensitivity can be suppressed. Also, since the input / output circuit pattern of the tuner board and the wiring pattern of the set board are directly connected, connection conductors for connecting between terminals that were conventionally used are not required, and the number of parts can be reduced. It is possible to provide an inexpensive tuner because it is possible to eliminate defects due to terminal bending in the manufacturing process. Further, the number of soldering points in the terminal portion for connection between the tuner substrate and the set substrate is reduced by one compared with the related art, so that the impedance of the input / output circuit can be reduced.

Further, since the tuner substrate can be connected to the set substrate by using only one surface, the rear surface of the tuner substrate can be formed with different input / output terminal formation portions. The number can be doubled.

According to the second aspect of the present invention, in the configuration of the first aspect, the fixing force in the direction in which the input / output circuit pattern is distorted is increased, and the pattern connection between the two substrates is stabilized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a circuit of the present invention.

FIG. 2 is a diagram illustrating an example of an arrangement of the circuit illustrated in FIG. 1;

FIG. 3 is a diagram showing a configuration of a main part of the first embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a main part of a second embodiment of the present invention.

FIG. 5 is a block diagram of a conventional circuit.

FIG. 6 is a diagram showing an arrangement of a circuit of a conventional example.

FIG. 7 is a perspective view showing a mounting structure of a tuner substrate and a set substrate in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Connector 37 ... RF circuit 38 ... Baseband circuit 39 ... Tuning circuit 43, 46 ... Chassis 44, 44 '... Tuner board 45 ... Set board 47 ... Input / output circuit pattern 48, 52 ... Opening 49 ... Wiring pattern 50 ... Notch 51 ... Projection

Claims (2)

[Claims] 1. An RF circuit for performing RF signal processing of an input signal, a baseband circuit for orthogonally detecting an output of the RF circuit and outputting a baseband signal, and a tuning station for selecting a specific channel of the input signal. In a direct conversion tuner unit for digital satellite broadcasting constituted by a circuit, a tuner for shielding at least one of the RF circuit and the tuning circuit formed on a tuner substrate is provided, and the tuner for connecting to a set substrate is provided. An end of the input / output circuit pattern formed on the substrate is formed so as to extend and be exposed on one end surface of the tuner substrate. When the tuner substrate is aligned in a direction orthogonal to the set substrate, the input / output circuit A wiring pattern for connecting the input / output circuit pattern is located at a position facing the end of the pattern. The wiring patterns are formed on a set substrate so that the two substrates are electrically connected and physically fixed to each other in a state where the two substrates are aligned in a direction orthogonal to each other. Direct conversion tuner unit. 2. An end portion of the input / output circuit pattern is formed in a substantially V-shaped projection formed on the tuner substrate, the tip portion of which is narrowed. When the tuner substrate and the set substrate are aligned in a direction orthogonal to each other, An opening is formed in the set board so that the substantially V-shaped protrusion fits therein. When the protrusion is fitted in the opening, the opening faces the corresponding end of the input / output circuit pattern extending on the protrusion. The wiring pattern to be formed is formed on a set substrate, and an end of the input / output circuit pattern and an end of the wiring pattern on the set substrate are electrically connected and physically fixed. 1. The tuner unit of the direct conversion method according to 1.