JPH05259705A - Variable band pass filter - Google Patents

Abstract

PURPOSE:To allow the filter applied to a frequency selection section of a 1st intermediate frequency of a satellite broadcast use tuner to eliminate the need for a grounded shield plate shielding the variable band pass filter and its peripheral circuit with a small mount area and less number of components. CONSTITUTION:Microstrip lines 25, 26 are adopted for inductance lines used for a variable tuning circuit section at a primary side being an input section of the variable band pass filter and at a secondary side being an output section. Since deviation if the relation of position of the microstrip lines 25, 26 caused at mounting is less, the dispersion in the characteristic of the variable band pass filters at mass-production is reduced. Furthermore, a microstrip line 29 is arranged around a ground side of the microstrip lines 25, 26 and the length, the width and the interval of the microstrip lines 25, 26 are optionally selected for the adjustment of the pass frequency band. Furthermore, a copper foil is arranged to the outside of the microstrip lines 25, 26 to make shielding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a frequency selecting section of a receiver, and more particularly to a variable band pass filter for selecting a first intermediate frequency of 1 GHz band in a satellite broadcasting tuner.

[0002]

2. Description of the Related Art A conventional variable band pass filter is shown in FIG.
The configuration was as shown in FIG. FIG. 7 shows a first conventional example, in which a circuit element 9 constituting a variable band pass filter is shielded by a chassis 8 or a ground shield plate 7 of the equipment, and a variable band pass is made from a gap 6 of the chassis 8 or the ground shield plate 7. It is constructed by taking out the input terminal 1 and the output terminal 2 of the filter. In the figure, reference numeral 5 is a tuning voltage power supply connection terminal for supplying a voltage to the variable capacitance element in the circuit element 9 constituting the variable band pass filter.

FIG. 8 shows a second conventional example, in which the first inductance line 21 and the second inductance line 21 are arranged in parallel with each other with a certain distance in the horizontal direction with each length direction of the inductance line being horizontal. Inductance line 2
2, one terminal of each of the third inductance line 23 and the fourth inductance line 24 is grounded, and the first outside of the four inductance lines 21 to 24 is connected.
The non-grounded terminals of the inductance line 21 and the second inductance line 22 are used as the input terminal 1 and the output terminal 2 via the first capacitor 11 and the second capacitor 12, respectively, and the third inductance line 23 and the fourth non-grounded terminal of the fourth inductance line 24 are connected to the third capacitor 13,
The cathodes of the first variable capacitance diode 31 and the second variable capacitance diode are simultaneously connected to the cathodes of the first variable capacitance diode 31 and the second variable capacitance diode 32 via the fourth capacitor 14, respectively. A first resistor 41 is connected between the cathodes of 32, the anodes of the first variable capacitance diode 31 and the second variable capacitance diode 32 are grounded, and the first variable capacitance diode 31 or the second variable capacitance is connected. The cathode of the diode 32 is connected via the second resistor 42 to the tuning voltage power supply connection terminal 5
The circuit configured by connecting to the device is shielded by the chassis 8 or the ground shielding plate 7 of the equipment, and the input terminal 1 and the output terminal 2 of the variable band pass filter are taken out from the gap 6 of the chassis 8 or the ground shielding plate 7. Was configured.

[0004]

However, in the configuration of the first conventional example described above, in addition to the circuit element 9 in which the variable bandpass filter constitutes the variable bandpass filter, the circuit element constituting the variable bandpass filter is added. Since the grounding shield plate 7 for shielding 9 is required, there is a problem that a large mounting area is required.

In the configuration of the second conventional example described above, the variable bandpass filter is provided with the ground shielding plate 7 for shielding the circuit elements forming the variable bandpass filter in addition to the circuit elements forming the variable bandpass filter. In order to effectively ground the first to fourth inductance lines 21, 22, 23, and 24, each of the inductance lines 21 to 21 requires a large mounting area.
It is necessary to make the ground plane of 24 large. In addition, it is necessary to mount the four inductance lines 21 to 24 on the substrate so as not to shift the positions, and there is a problem that the manufacturing cost becomes high.

The present invention can solve the above-mentioned conventional problems and reduce the mounting area of the variable band pass filter.
It is an object of the present invention to provide a variable bandpass filter that does not need to be provided with a ground shielding plate and need not have an inductance line.

[0007]

In order to solve the above problems, a variable bandpass filter according to the present invention is a variable tuning circuit including a microstrip line formed on the front surface of a double-sided substrate whose back surface is a ground surface and a variable capacitance diode. Are provided on the primary side which is the input part and the secondary side which is the output part, and the ground ends of the microstrip lines on the primary side and the secondary side are connected to the back surface of the substrate through through holes and at the same time on the front surface. Then, the through holes are connected by a copper foil.

Alternatively, a plurality of through holes connected to the ground plane on the rear surface of the substrate are provided between the microstrip lines in the primary side and secondary side variable tuning circuits formed in parallel, and the through holes are formed on the front surface of the substrate. It is configured such that some of the plurality of through holes are connected by a copper foil having a constant width.

[0009]

With the above configuration, the inductance band used in the variable tuning circuit on the primary side which is the input part of the variable band pass filter and the secondary side which is the output part of the variable band pass filter is a microstrip line. The mounting area of the pass filter can be reduced, there is no displacement between the inductance lines on the primary side and the secondary side that occur during mounting, and the micro tuning circuit of the primary side and the secondary side arranged in parallel is A copper foil of a certain width is arranged in parallel outside the strip line, and the copper foil is connected to the ground plane on the back surface of the substrate by a plurality of through holes to shield the peripheral circuit and the variable bandpass filter. Is possible,
The device can be downsized without the need for a ground shield for shielding the variable band pass filter.

[0010]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a variable bandpass filter according to a first embodiment of the present invention, in which 1 is an input terminal, 2 is an output terminal, 5 is a tuning voltage power supply connection terminal, and 1 is a tuning voltage power supply connection terminal.
1, 12, 13, 14, and 15 are first, second, third, fourth, and fifth capacitors, 25, 26, 27, and 2, respectively.
8 and 29 are the first, second, third, fourth, and fifth microstrip lines, and 31 and 32 are the first and first microstrip lines, respectively.
The second variable capacitance diodes 41 and 42 are first and second resistors, respectively.

A mounting state in which the variable band pass filter of FIG. 1 is mounted on a double-sided board is shown in FIG. 2, 4 is a double-sided board whose back surface is a ground plane, and 3 is a copper foil pattern on the front surface of the double-sided board 4 and a back surface. The through-hole connecting to the ground plane of 6 is a copper foil pattern on the front surface of the double-sided board 4, and is connected to the ground plane on the back surface of the double-sided board 4 by the through-hole 3.

In the variable bandpass filter having the above-described structure, the microstrip lines 25 and 25 are provided in the variable tuning circuits on the primary side as the input section and the secondary side as the output section, respectively.
26 is used, and the microstrip line 2 is used.
5 and 26 have the same length and the same width, and the variable frequency range of the variable bandpass filter can be arbitrarily changed by making the length and the width optional. It is possible to change the degree of coupling between the primary side and the secondary side by changing the distance between the microstrip lines 25 and 2.
The positional relationship of 6 does not shift, and it is possible to reduce variations in characteristics during mass production.

The microstrip lines 27 and 28 are
A variable bandpass filter having a width smaller than that of the microstrip lines 25 and 26, and arbitrarily selecting the length and width of the microstrip lines 27 and 28 and the capacities of the first and second capacitors 11 and 12. It is possible to optimize the frequency selectivity, the input impedance and the output impedance.

Further, by changing the width of the microstrip line 29 and the distance between the ground ends of the microstrip lines 25 and 26 from the through hole 3, the degree of coupling between the primary side and the secondary side of the variable bandpass filter can be improved. It can be changed, and the frequency band pass characteristic after the variable band pass filter is mounted on the double-sided board 4 can be adjusted.

By arranging the copper foil pattern 6 outside the microstrip line 25 or 26 with a certain distance, the variable band pass filter can be shielded, and the peripheral circuit and the variable band pass filter can be shielded. It is no longer necessary to provide a grounding shield to shield the filter,
It is possible to downsize equipment using this variable bandpass filter and reduce manufacturing costs.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a circuit diagram of a variable band pass filter according to the second embodiment of the present invention, in which 1 is an input terminal, 2 is an output terminal, 5 is a tuning voltage power supply connection terminal, and 1 is a tuning voltage power supply connection terminal.
1, 12, 13, 14, and 15 are first, second, third, fourth, and fifth capacitors, 25, 26, 27, and 2, respectively.
8 and 29 are the first, second, third, fourth, and fifth microstrip lines, and 31 and 32 are the first and first microstrip lines, respectively.
The second variable capacitance diodes 41 and 42 are first and second resistors, respectively.

A mounting state in which the variable band pass filter of FIG. 3 is mounted on a double-sided board is shown in FIG. 4, 4 is a double-sided board whose back surface is a ground plane, and 3 is a copper foil pattern on the front surface of the double-sided board 4 and a back surface. The through-hole connecting to the ground plane of 6 is a copper foil pattern on the front surface of the double-sided board 4, and is connected to the ground plane on the back surface of the double-sided board 4 by the through-hole 3.

In the variable bandpass filter having the above-mentioned structure, the microstrip lines 25 and 25 are provided in the variable tuning circuits on the primary side which is the input section and the secondary side which is the output section, respectively.
26 is used, and the microstrip line 2 is used.
5 and 26 have the same length and the same width, and the variable frequency range of the variable band pass filter can be arbitrarily changed by making the length and the width optional. It is possible to change the degree of coupling between the primary side and the secondary side by changing the distance between the microstrip lines 25 and 2.
The positional relationship of 6 does not shift, and it is possible to reduce variations in characteristics during mass production.

The microstrip lines 27 and 28 are
By making the width narrower than that of the microstrip lines 25 and 26 and arbitrarily selecting the length and width of the microstrip lines 27 and 28 and the capacitance of the capacitors 11 and 12, the frequency selectivity and input of the variable band pass filter can be obtained. It is possible to optimize the impedance and the output impedance.

Further, the ground patterns of the anodes of the first and second variable capacitance diodes 31, 32 are connected by a microstrip line 29, and the width of the microstrip line 29 and the first, second By changing the distance from the anode terminal of each of the variable capacitance diodes 31 and 32, the degree of coupling between the primary side and the secondary side of the variable bandpass filter can be changed, and the variable bandpass filter can be formed on the double-sided board 4. It becomes possible to adjust the frequency band pass characteristics after mounting.

By arranging the copper foil pattern 6 outside the microstrip line 25 or 26 with a certain distance, the variable band pass filter can be shielded, and the peripheral circuit and the variable band pass filter can be shielded. It is no longer necessary to provide a grounding shield to shield the filter,
It is possible to reduce the size of the device using this variable bandpass filter and reduce the manufacturing cost.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 shows a mounted state in which the variable bandpass filter according to the third embodiment of the present invention is mounted on a double-sided board. The circuit configuration of the variable bandpass filter shown in FIG. 5 is that shown in FIG. The air core coil 51 is newly added to the. Reference numeral 4 is a double-sided board having a back surface as a ground plane, 3 is a through hole for connecting a copper foil pattern on the front surface of the double-sided board 4 and a ground plane on the back surface, and 6 is a copper foil pattern on the front surface of the double-sided board 4. It is connected to the ground plane on the back surface of the double-sided board 4 by a through hole 3, and both terminals of the air-core coil 51 are provided between the microstrip line 26 and the copper foil pattern 6 in parallel with the microstrip line 26. The two through holes 3 are connected to the ground plane, which is the back side of the double-sided board 4.

The variable bandpass filter in this embodiment performs the same operation as that of the first embodiment, and tilts the air-core coil 51 toward the microstrip line 26, so that the variable bandpass filter 1 The tuning frequency of the variable tuning circuit on the secondary side or the secondary side can be changed, and the pass frequency of the variable bandpass filter can be adjusted.

The same effect can be obtained when the air-core coil 51 is arranged between the chassis 8 and the microstrip line 25 or between the microstrip line 25 and the microstrip line 26.

(Embodiment 4) A fourth embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 shows a mounting state in which the variable bandpass filter according to the fourth embodiment of the present invention is mounted on a double-sided board, and the circuit configuration of the variable bandpass filter shown in FIG. 6 is that shown in FIG. Is the same as. Reference numeral 4 is a double-sided board having a back surface as a ground plane, 3 is a through hole for connecting the copper foil pattern on the front surface of the double-sided board 4 and the ground plane on the back surface, and 6 and 10 are copper foil patterns on the front surface of the double-sided board 4. Yes Connected to the ground plane on the back surface of the double-sided board 4 by the through hole 3.

The variable band pass filter configured as described above performs the same operation as that of the first embodiment, and at the same time, by arranging the copper foil pattern 6 around the variable band pass filter, the peripheral circuit and the variable band pass filter are arranged. The pass filter can be shielded more effectively, and the attenuation outside the pass frequency band of the variable band pass filter can be increased.

Further, the microstrip line 25,
By providing the copper foil patterns 10 arranged between the two 26 at two positions separated by an arbitrary distance, it is possible to change the degree of coupling between the primary side and the secondary side of the variable bandpass filter.
The distance between the copper foil patterns 10 provided at two locations is adjusted by trimming after mounting the variable bandpass filter,
It is also possible to optimize the characteristics of the variable bandpass filter.

[0032]

As described above, according to the present invention, the inductance line used for the variable tuning circuit section on the primary side which is the input section of the variable band pass filter and the secondary side which is the output section is a microstrip line. The mounting area of the variable band pass filter can be reduced, there is no displacement of the inductance line on the primary side and the secondary side at the time of mounting, and there is little variation in the characteristics of the variable band pass filter during mass production. Copper foils of a certain width are arranged in parallel outside the microstrip lines of the primary side and secondary side tunable circuits arranged in parallel, and the copper foils are provided with a plurality of through holes to form a ground plane on the back surface of the substrate. By connecting with
It becomes possible to shield the peripheral circuit and the variable band pass filter, and it is possible to realize the miniaturization of the device using the variable band pass filter of the present invention without the need for a ground shield plate for shielding the variable band pass filter. .. Further, it is possible to reduce the number of mounting parts and the number of mounting steps of the variable bandpass filter, and to provide an excellent variable bandpass filter that can realize cost reduction, which is of great industrial value.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a variable bandpass filter according to a first embodiment of the present invention.

FIG. 2 is a mounting diagram of a variable bandpass filter according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a variable bandpass filter according to a second embodiment of the present invention.

FIG. 4 is an implementation diagram of a variable bandpass filter according to a second embodiment of the present invention.

FIG. 5 is a mounting diagram of a variable bandpass filter according to a third embodiment of the present invention.

FIG. 6 is a mounting diagram of a variable bandpass filter according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram showing a variable bandpass filter of Conventional Example 1.

FIG. 8 is a circuit diagram showing a variable bandpass filter of Conventional Example 2.

[Explanation of symbols]

 1 Input Terminal 2 Output Terminal 3 Through Hole 4 Double Sided Board 5 Tuning Voltage Power Supply Connection Terminal 6,10 Copper Foil Pattern 8 Chassis 11-15 Capacitor 25-29 Micro Strip Line 31,32 Variable Capacitance Diode 41,42 Resistor 51 Air Core Coil

Claims (5)

[Claims] 1. A variable tuning circuit comprising a microstrip line formed on the front surface of a double-sided substrate whose back surface is a ground plane and a variable capacitance diode is provided on a primary side as an input section and a secondary side as an output section, A variable bandpass filter in which the ground ends of the primary and secondary side microstrip lines are connected to the back surface of the double-sided board via through holes, and at the same time, the through holes are connected with copper foil on the front surface. 2. A variable tuning circuit comprising a microstrip line formed on the front surface of a double-sided substrate whose back surface is a ground surface and a variable capacitance diode is provided on a primary side which is an input section and a secondary side which is an output section, A variable bandpass filter in which the ground ends of the variable capacitance diodes on the primary side and the secondary side are connected to the back surface of the double-sided board through through holes, and at the same time, the through holes are connected on the front surface with copper foil. 3. A plurality of through holes connected to the ground plane on the back surface of the substrate are provided between the microstrip lines in the primary side and secondary side tunable circuits formed in parallel,
3. The variable bandpass filter according to claim 1, wherein some of the plurality of through holes on the surface of the double-sided substrate are connected with copper foil having a constant width. 4. A through-hole is provided in parallel with a microstrip line of a variable tuning circuit on the primary side or a secondary side at a fixed distance, and both terminals of an air-core coil are provided in the two through-holes. 4. The variable bandpass filter according to claim 1, wherein the variable bandpass filter is connected to the ground plane on the back surface of the double-sided board. 5. A copper foil having a constant width is arranged in parallel outside the microstrip lines of the primary side and the secondary side tunable circuits arranged in parallel, and the copper foil is formed into a substrate by a plurality of through holes. 5. The variable bandpass filter according to claim 1, wherein the variable bandpass filter is connected to the ground plane on the back side of the.