JPH11144962A - Filter and high frequency device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter which can be accurately adjusted with little changes in adjusted value. SOLUTION: A filter constituted of an inductance is provided on a printed board and a capacitance, which is connected in parallel to the inductance. The inductance is comprised of two coreless coils 14 and 15 which are connected in series. One coreless coil 15 is made adjustable, and the other coreless coil 13 is a fixed inductance. In this way, a filter which can be accurately adjusted with little change in adjusted value can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency-adjustable filter and a high-frequency device using the filter.

[0002]

2. Description of the Related Art A conventional filter will be described below. In the conventional filter, as shown in FIG. 8, an inductance 3 and a capacitance 4 are connected in parallel between terminals 1 and 2. The capacitor 4 uses a chip component, and the inductance 3 uses an air-core coil 3a. This air-core coil 3a is composed of one part,
The passing frequency was adjusted by changing the inductance value. That is, frequency adjustment was performed by breaking the air core coil 3a.

[0003]

However, in such a conventional configuration, since the air-core coil 3a is a single component, when the air-core coil 3a is divided, the inductance 3
Changes were too large and fine-tuning was difficult. Further, since the air-core coil 3a after adjustment is a wire having elasticity, a change in the adjustment value due to springback caused by this elasticity is also one of the factors that make adjustment difficult.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a filter which can be adjusted accurately and has little change in adjustment value.

[0005]

According to the present invention, there is provided a filter comprising an inductance provided on a printed circuit board and a capacitance connected in parallel with the inductance. The plurality of inductance elements are connected in series, and at least one of the inductance elements is formed by an adjustable air-core coil, and the other inductances are fixed inductances.

As a result, a filter that can be adjusted accurately and has a small change in the adjustment value can be obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a first aspect of the present invention, there is provided a filter comprising an inductance provided on a printed circuit board and a capacitance connected in parallel to the inductance, wherein the inductance is plural. Are connected in series, and at least one of the inductance elements is formed of an adjustable air-core coil, and the other inductance is a filter having a fixed inductance, and the adjustable air-core coil is the entire inductance. , The adjustment range is reduced, but fine adjustment is possible, and accurate adjustment can be performed. Further, since the adjustable inductance is smaller than the whole inductance, even if the air-core coil has elasticity, the adjustment value change due to springback is reduced, and the adjustment becomes easy.

According to a second aspect of the present invention, an inductance is formed by two air-core coils connected in series, and the first air-core coil and the second air-core coil are perpendicular to each other on a printed circuit board. The filter according to claim 1, which is mounted, wherein the two air-core coils are arranged at right angles to each other, so that they do not interfere with each other. Also, since both inductances are formed by air-core coils, they can be realized at low cost and have a higher queue (hereinafter referred to as Q) than the inductance formed by the pattern.

According to a third aspect of the present invention, the first air-core coil is mounted parallel to the printed circuit board, and the second air-core coil is provided perpendicular to the printed circuit board. In the filter described above, the first air-core coil is mounted in parallel with the printed circuit board, so that the coil can be easily split and adjusted. Further, since the second air-core coil is provided perpendicular to the printed circuit board, it does not adversely affect other circuits due to the magnetic flux. In addition, by being provided vertically, the size can be reduced and the coil Q
Is not reduced.

The invention according to claim 4 is the filter according to claim 3, wherein the inductance ratio between the first air-core coil and the second air-core coil is approximately 3: 7. Since the coil is mounted in parallel with the printed circuit board, it can be easily adjusted by breaking the coil. Further, this adjustment range is 30% of the total inductance, so that an appropriate adjustment range can be obtained and the change in the adjustment value due to springback is reduced. Further, since the second air-core coil occupying 70% is provided perpendicular to the printed circuit board, the adverse effect of the magnetic flux on other circuits is reduced.

According to a fifth aspect of the present invention, there is provided an input terminal to which a high-frequency signal is input, a high-frequency amplifier circuit to which a signal input to this input terminal is supplied, and an output of the high-frequency amplifier circuit to one input. 5. The filter according to claim 4, wherein the filter is connected to the output of the first local oscillator circuit and connected to the other input, and the intermediate frequency is connected to the output of the mixer circuit. An intermediate frequency amplifying circuit connected to the filter and an output of the intermediate frequency amplifying circuit connected to one input and an output of a second local oscillation circuit for oscillating a frequency substantially equal to the intermediate frequency are provided to the other input. This is a high-frequency device having a connected demodulation circuit and an output terminal to which the output of the demodulation circuit is supplied. Since the filter is adjustable, the intermediate frequency can be adjusted to the second frequency.
Frequency of the local oscillation circuit. Also, since the second air-core coil occupying approximately 70% of this filter is provided perpendicular to the printed circuit board,
And the adverse effect of the magnetic flux due to interference with the local oscillation circuit is reduced, and the noise figure (hereinafter referred to as NF) is improved.

According to a sixth aspect of the present invention, in the high-frequency device according to the fifth aspect, a metal partition plate is provided between the filter and the second local oscillation circuit while being housed in a metal housing. Since the interference between the filter and the second local oscillation circuit is further reduced by the partition plate, NF is further improved.

According to a seventh aspect of the present invention, there is provided a series connection of a fixed inductance and an adjustable air-core coil formed in series on a printed circuit board, and a first connection connected to both ends of the series connection. And a second capacitor connected between the fixed inductance of the series-connected body, the connection point of the air-core coil, and the ground,
A predetermined first capacitor and a series connection body.
And a trap filter for removing a predetermined second frequency by the fixed inductance of the series-connected body and the second capacitor. Since the filter has an adjustable air core coil, it can be adjusted to pass the first frequency. Further, since the adjustable air-core coil is a part of the whole inductance, fine adjustment is possible instead of reducing the adjustment range, and accurate adjustment can be performed. Furthermore, since the adjustable inductance is smaller than the total inductance, even if the air-core coil has elasticity, the change in the adjustment value due to springback is reduced,
Adjustment becomes easy. Further, since the trap filter for removing the second frequency is formed by sharing the fixed inductance used in the band-pass filter, it is possible to realize a small size, low cost and light weight.

The invention according to claim 8 is the filter according to claim 7, wherein the fixed inductance and the air-core coil are arranged at right angles. Since the air-core coil and the fixed inductance are arranged at right angles to each other, Does not interfere. Further, since at least one of the inductances is formed by an air-core coil, it can be realized at a low cost and has a higher Q than the inductance formed by the pattern.

According to a ninth aspect of the present invention, in the filter according to the eighth aspect, the air-core coil is mounted in parallel with the printed board and the fixed inductance is provided perpendicular to the printed board. Since the core coil is mounted in parallel with the printed circuit board, it can be easily adjusted by breaking the coil. Also, since the fixed inductance is provided perpendicular to the printed circuit board, it does not adversely affect other circuits due to magnetic flux. Further, by providing the antenna vertically, the size can be reduced, and since the air core coil is used, the Q of the coil does not decrease.

According to a tenth aspect of the present invention, there is provided the filter according to the ninth aspect, wherein the inductance ratio between the fixed inductance and the air-core coil is approximately 2 to 8, wherein the air-core coil is mounted in parallel with the printed circuit board. So it can be easily adjusted by breaking the coil. Further, this adjustment range is 80% of the total inductance, so that an appropriate adjustment range can be obtained and the change in the adjustment value due to springback is reduced. Further, since the fixed inductance occupying 20% is provided perpendicular to the printed circuit board, the adverse effect of the magnetic flux on other circuits is reduced.

According to an eleventh aspect of the present invention, there is provided an input terminal to which a high-frequency signal is input, a high-frequency amplifier circuit to which a signal input to the input terminal is supplied, and an output of the high-frequency amplifier circuit to one input. 11. A filter connected to the output of the local oscillator circuit connected to the other input while being connected to the other input, the filter according to claim 10 connected to the output of the mixer circuit and passing the intermediate frequency, and connected to the filter. And an output terminal connected to the output of the intermediate frequency amplifying circuit. The filter passes the intermediate frequency output from the mixing circuit and removes the audio signal of the adjacent lower channel. Since it is a high-frequency device and the filter is adjustable, the intermediate frequency can be adjusted. Also, with the trap filter,
The audio signal of the adjacent lower channel can be removed.

According to a twelfth aspect of the present invention, there is provided an input terminal to which a high-frequency signal is input, a high-frequency amplifier circuit to which a signal input to the input terminal is supplied, and an output of the high-frequency amplifier circuit to one input. 11. The filter according to claim 10, wherein the filter is connected to an output of the first local oscillator circuit and connected to the other input, and is connected to an output of the mixer circuit and passes an intermediate frequency. An intermediate frequency amplifying circuit connected to the filter and an output of the intermediate frequency amplifying circuit connected to one input and an output of a second local oscillation circuit for oscillating a frequency substantially equal to the intermediate frequency are provided to the other input. A demodulation circuit connected thereto, and an output terminal to which an output of the demodulation circuit is supplied, wherein the filter passes an intermediate frequency output from the mixing circuit and an adjacent lower channel. A high-frequency device for removing the audio signal of the tunnel, since the filter is adjustable, it is possible to adjust the intermediate frequency to the frequency of the second local oscillation circuit. Further, since the second air-core coil occupying approximately 20% of the filter is provided perpendicular to the printed circuit board, it is less likely to interfere with the second local oscillation circuit and adversely affect the magnetic flux. NF is improved. Further, the audio signal of the adjacent lower channel can be removed by the trap filter.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) The filter in Embodiment 1 is
As shown in FIG. 1, a fixed capacitor (used as an example of capacitance) 13 is provided between terminals 11 and 12.
A series connection of an air-core coil (used as an example of a fixed inductance, which may be formed by a printed pattern) 14 and an air-core coil (used as an example of a variable inductance) 15 is connected in parallel with the above. ing.

As described above, since the inductance is divided into the air-core coils 14 and 15, and the adjustment of the inductance is performed only by the air-core coil 15, fine adjustment is possible instead of reducing the adjustment range. In addition, since the change width of the air-core coil is small, springback due to change over time or over time is reduced. Further, by using the air-core coil, a large Q can be obtained and the cost can be reduced as compared with the case where a pattern inductance is formed.

It is important that the two air-core coils 14 and 15 are arranged at right angles to each other as shown in FIG. By arranging them at right angles to each other, the influence of magnetic flux is eliminated.

Further, as shown in FIG.
By arranging the air core coil 15 for adjustment in parallel on 6 and providing the fixed air core coil 14 vertically to the printed circuit board 16, it is possible to reduce the size in mounting. By providing the air-core coil 14 vertically, there is no adverse effect on other circuits, although the reason is not clear. This is because the magnetic flux of the air-core coil 14 is
It seems that there is little effect because it crosses at right angles. On the other hand, if it is arranged in parallel with the printed circuit board 16 like the air-core coil 15, the magnetic flux runs on the surface of the printed circuit board 16, and it is considered that the magnetic flux affects other circuits.

(Embodiment 2) FIG. 4 is a block diagram of a high-frequency device using a filter of the present invention in Embodiment 2. In FIG. 4, the high-frequency device according to the second embodiment includes an input terminal 21 to which a high-frequency signal is input, a high-frequency amplifier circuit 22 to which a signal input to the input terminal 21 is supplied, and a high-frequency amplifier circuit 22. An output is connected to one input and a local oscillation circuit 2 is connected to the other input.
3 is connected to the output of the mixing circuit 24;
4, an intermediate frequency amplifying circuit 26 connected to the filter 25, and an output of the intermediate frequency amplifying circuit 26 connected to one input and the other The input is composed of a demodulation circuit 28 to which the output of a local oscillation circuit 27 for oscillating a frequency substantially equal to the intermediate frequency is connected, and an output terminal 29 to which the output of the demodulation circuit 28 is connected. The filter 25 uses the filter described in the first embodiment.

In such a high-frequency device, by using the filter 25 of the first embodiment, the filter 25 can be adjusted, so that the intermediate frequency can be adjusted to the frequency of the local oscillation circuit 27. Further, since the air-core coil 14 occupying approximately 70% of the filter 25 is provided perpendicular to the printed circuit board 16, the air-core coil 14 interferes with the local oscillation circuit 27 and adversely affects the magnetic flux. Is less. Therefore, NF in this high-frequency device is improved.

FIG. 5 shows the mounting of the high-frequency device according to the second embodiment. In the high-frequency device according to the second embodiment, the circuit shown in FIG. 4 is mounted on a printed circuit board 30 (having the same function as the printed circuit board 16 of the first embodiment), and is mounted in a metal housing 31. Have been. The air-core coils 14 and 15 constituting the filter 25 are provided in one of the compartments 33 via a metal partition plate 32, and a local oscillation circuit 27 and the local oscillation circuit 27 are provided in the other compartment 34. The high frequency transformer 35 to be constituted is provided upright. As described above, since the interference between the filter 25 and the local oscillation circuit 27 is further reduced by the partition plate 32, NF is further improved.

(Embodiment 3) FIG. 6 is a circuit diagram of a filter according to Embodiment 3. In FIG. 6, a filter according to the third embodiment includes a series connection body 43 of an air-core coil 41 (used as an example of a fixed inductance) formed in series on a printed circuit board and an adjustable air-core coil 42. And a capacitor 44 connected to both ends of the series-connected body 43, and an air-core coil 41 of the series-connected body 43.
And a capacitor 46 connected between a connection point 45 of the air-core coil 42 and the ground, and a capacitor 44 and a series connection body 43 form a band-pass filter that passes a predetermined first frequency. ing. Further, a trap filter for removing a predetermined second frequency is formed by the air core coil 41 of the series connection body 43 and the capacitor 46. Both ends of the series connection body 43 are connected to terminals 47 and 48 as terminals of the filter, respectively. This filter includes an air-core coil 41 and an air-core coil 42.
Are approximately 2 to 8. The air core coil 41 is approximately 95 nanohenries, and the air core coil 42 is approximately 76 nanohenries.
0 nanohenry, the condenser 44 is approximately 9 picofarats, and forms a bandpass filter of 45.75 MHz. In addition, the condenser 46 uses approximately 12 picofarats and uses the audio frequency 4 of the adjacent lower channel.
A trap filter that removes 1.25 MHz is realized.

As described above, since the band-pass filter has the adjustable air core coil 42, it can be adjusted to pass the first frequency (45.75 MHz). Further, since the adjustable air-core coil 42 is a part of the whole inductance, fine adjustment is possible instead of reducing the adjustment range, and accurate adjustment can be performed. Furthermore, since the inductance of the air-core coil 42 that can be adjusted is smaller than the entire inductance, even if the air-core coil 42 has elasticity, the adjustment change due to springback is reduced, and the adjustment becomes easier. Furthermore, since the trap filter for removing the second frequency (41.25 MHz) can be formed by sharing the air core coil 41 used in the band-pass filter, a small size, low cost and light weight can be realized.

The same effect as in the first embodiment can be obtained by arranging the air-core coils 41 and 42 in the same manner as in the first embodiment. That is, the air-core coil 4
1 and the air-core coil 42 are arranged at right angles to each other, and the air-core coil 41 is mounted vertically to the printed circuit board.
The air-core coil 42 is mounted parallel to the printed circuit board for adjustment.

(Embodiment 4) FIG. 7 is a block diagram of a high-frequency device using a filter of the present invention in Embodiment 4. In FIG. 7, the high-frequency device according to the fourth embodiment includes an input terminal 51 to which a high-frequency signal is input, a high-frequency amplifier 52 to which a signal input to the input terminal 51 is supplied, and a high-frequency amplifier 52 A tuning circuit 53 to which an output is connected, a mixing circuit 55 having an output connected to one input and an output of a local oscillation circuit 54 connected to the other input, A filter 56 according to the third embodiment which is connected to an output and passes an intermediate frequency, an intermediate frequency amplifying circuit 57 connected to the filter 56, and an output terminal to which an output of the intermediate frequency amplifying circuit 57 is connected 58 is provided. The filter 56 outputs the intermediate frequency (45.75 MHz) output from the mixing circuit 55.
z), and removes the audio signal (41.25 MHz) of the adjacent lower channel. As described above, since the filter 56 is adjustable, the intermediate frequency can be adjusted. Further, the trap filter can remove the audio signal of the adjacent lower channel.

The filter according to the third embodiment can be used for the high-frequency device described in the second embodiment. That is, the configuration is such that an input terminal to which a high-frequency signal is input, a high-frequency amplifier circuit to which a signal input to this input terminal is supplied, and an output of the high-frequency amplifier circuit connected to one input and the other A mixer connected to the input of the output of the first local oscillation circuit, a filter connected to the output of the mixer and passing an intermediate frequency, and a filter connected to the filter. A demodulation circuit in which an intermediate frequency amplifier circuit and an output of the intermediate frequency amplifier circuit are connected to one input and an output of a second local oscillation circuit for oscillating a frequency substantially equal to the intermediate frequency is connected to the other input; And an output terminal to which the output of the demodulation circuit is connected. The filter allows the intermediate frequency output from the mixing circuit to pass through, and Those provided to remove items. Thus, the filter is adjustable and the intermediate frequency can be tuned to the frequency of the second local oscillator. Further, since the second air-core coil occupying approximately 20% of the filter is provided perpendicular to the printed circuit board, it is less likely to interfere with the second local oscillation circuit and adversely affect the magnetic flux. NF is improved. Furthermore,
The trap filter can remove the audio signal of the adjacent lower channel.

[0031]

As described above, the filter according to the present invention is a filter comprising an inductance provided on a substrate and a capacitance connected in parallel to the inductance, wherein the inductance comprises a plurality of inductance elements connected in series. Connected and at least one of the inductance elements is formed of an adjustable air core coil, and the other inductance is a fixed inductance, and the adjustable air core coil is a part of the entire inductance. Therefore, fine adjustment is possible instead of the adjustment range being reduced, and accurate adjustment can be performed. Further, since the adjustable inductance is smaller than the whole inductance, even if the air-core coil has elasticity, the adjustment value change due to springback is reduced, and the adjustment becomes easy.

[Brief description of the drawings]

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

FIG. 2 is a layout diagram of an air-core coil constituting the filter.

FIG. 3 is a layout diagram of air-core coils constituting a filter according to another example of the present invention.

FIG. 4 is a block diagram of a high-frequency device using the filter according to the first embodiment in the second embodiment of the present invention;

FIG. 5 is a layout diagram of the same.

FIG. 6 is a circuit diagram of a filter according to a third embodiment of the present invention.

FIG. 7 is a block diagram of a high-frequency device using a filter according to a third embodiment of the present invention.

FIG. 8 is a circuit diagram of a conventional filter.

[Explanation of symbols]

 11 terminal 12 terminal 13 capacitor 14 air core coil 15 air core coil 16 printed circuit board

Claims (12)

[Claims] 1. A filter comprising an inductance provided on a printed circuit board and a capacitance connected in parallel to the inductance, wherein the inductance comprises a plurality of inductance elements connected in series and at least one of them. One inductance element is formed by an adjustable air core coil, and the other inductance is a fixed inductance filter. 2. An inductance is formed by two air-core coils connected in series, and a first air-core coil and a second air-core coil are connected to each other.
The filter according to claim 1, wherein the air-core coil is mounted on the printed circuit board at right angles to each other. 3. The filter according to claim 2, wherein the first air-core coil is mounted in parallel with the printed circuit board, and the second air-core coil is provided perpendicular to the printed circuit board. 4. The filter according to claim 3, wherein the inductance ratio between the first air-core coil and the second air-core coil is approximately 3: 7. 5. An input terminal to which a high-frequency signal is input, a high-frequency amplifier circuit to which a signal input to the input terminal is supplied, and an output of the high-frequency amplifier circuit connected to one input and the other input A mixer connected to an output of the first local oscillator circuit, a filter connected to an output of the mixer and passing an intermediate frequency, and an intermediate frequency connected to the filter. An amplifier circuit, a demodulation circuit having an output of the intermediate frequency amplification circuit connected to one input and an output of a second local oscillation circuit for oscillating a frequency substantially equal to the intermediate frequency to the other input; A high-frequency device comprising an output terminal to which the output of the demodulation circuit is supplied. 6. The high-frequency device according to claim 5, wherein a metal partition plate is provided between the filter and the second local oscillation circuit while being housed in a metal housing. 7. A series connection of a fixed inductance and an adjustable air core coil formed in series on a printed circuit board, a first capacitor connected to both ends of the series connection, and the series connection. A second capacitor connected between a fixed inductance of the body, a connection point of the air-core coil, and ground, and passing a first frequency predetermined by the first capacitor and the series-connected body; And a trap filter for removing a predetermined second frequency by the fixed inductance of the series connection body and the second capacitor. 8. The filter according to claim 7, wherein the fixed inductance and the air-core coil are arranged at right angles. 9. The filter according to claim 8, wherein the air-core coil is mounted parallel to the printed circuit board, and the fixed inductance is provided perpendicular to the printed circuit board. 10. The filter according to claim 9, wherein an inductance ratio between the fixed inductance and the air-core coil is approximately 2: 8. 11. An input terminal for receiving a high-frequency signal,
A high-frequency amplifier circuit to which a signal input to the input terminal is supplied, a mixing circuit in which an output of the high-frequency amplifier circuit is connected to one input and an output of a local oscillator circuit is connected to the other input, 11. The filter according to claim 10, which is connected to an output of the mixing circuit and passes an intermediate frequency, an intermediate frequency amplifying circuit connected to the filter, and an output terminal to which an output of the intermediate frequency amplifying circuit is connected. A high-frequency device, wherein the filter passes an intermediate frequency output from the mixing circuit and removes an audio signal of an adjacent lower channel. 12. An input terminal for receiving a high-frequency signal,
A high-frequency amplifier circuit to which a signal input to the input terminal is supplied, and a mixing device in which an output of the high-frequency amplifier circuit is connected to one input and an output of the first local oscillation circuit is connected to the other input. 11. The filter according to claim 10, which is connected to an output of the mixing circuit and passes an intermediate frequency, an intermediate frequency amplifying circuit connected to the filter, and an output of the intermediate frequency amplifying circuit having one input. A demodulation circuit connected to an output of a second local oscillation circuit that oscillates a frequency substantially equal to the intermediate frequency at the other input, and an output terminal to which an output of the demodulation circuit is supplied, A high-frequency device that passes the intermediate frequency output from the mixing circuit and removes an audio signal of an adjacent lower channel.