JP2001217669A - Filter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make steep the attenuation characteristics of a filter device and a communication device which attenuate unwanted frequency components of a signal. SOLUTION: For example, a distributing means 1 distributes an object signal to be attenuated, a filter (BPF) 2 attenuates unwanted frequency components of one distributed signal, and an attenuating means 3 attenuates the other distributed signal, and a phase unit 4 and a delay circuit 5 put the signal attenuated by the filter 2 and the signal attenuated by the attenuating means 3 in phase relation, so that frequency components having the same amplitude cancel each other and a composing means 6 puts them together. Furthermore, a filter (BPF) 7 attenuates unwanted frequency components of the signal, after having been composed by the composing means 6 (or before being distributed by the distributing means 1).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter device and a communication device for attenuating unnecessary frequency components of a signal, and more particularly to a filter device and a communication device having a sharp characteristic for attenuating unnecessary frequency components.

[0002]

2. Description of the Related Art For example, filters for filtering a signal to be transmitted and limiting a pass band are widely used in various systems such as communication systems. Such a filter desirably has a transmission characteristic of passing only a signal in a required pass band and attenuating a signal in a band other than the required pass band as much as possible to prevent passage.

However, with the conventional filter, it is difficult to secure a sufficient amount of attenuation with respect to the attenuation characteristics outside the required pass band at a band point far from the upper band end or the lower band end of the pass band. However, it is very difficult to secure a sufficient amount of attenuation near these band edges.

As a specific example, FIG. 14 shows an example of a filter characteristic of a band pass filter (BPF).
The horizontal axis in the figure indicates the frequency (Hz), and the vertical axis indicates the attenuation (dB). Further, the required pass band is indicated as “own band”, and unnecessary frequency bands other than the required pass band are indicated as “other bands”. As mentioned above,
A relatively large amount of attenuation can be secured at a band point far from the band end of the own band, but near the band end of the own band (that is, near the boundary between the own band and another band). Only a slight attenuation x (dB) is obtained.

[0005] For this reason, for example, in a situation where different systems are adjacent to each other and each system communicates signals in bands close to each other, the filter characteristics (see FIG. For example, a BP having a characteristic in which a different own band is set for each system)
When F is used, there is a problem that mutual interference occurs between the two systems at a point near the boundary between the own band of the BPF used in each system and another band.

FIG. 15 shows an example of ideal BPF filter characteristics capable of solving the above-described problem. In FIG. 15, the horizontal axis indicates frequency (Hz), and the vertical axis indicates frequency. Indicates the amount of attenuation (dB). In the filter characteristic shown in the figure, a relatively large attenuation y (dB) is secured near the boundary between the own band and the other band adjacent thereto, and the slope of the attenuation in the vicinity (the slope of the filter characteristic). ) Is steep.

However, realizing a BPF having ideal filter characteristics as shown in FIG. 1 is very difficult even if the order is further increased or a complicated configuration is used using, for example, a high Q element. It is not practical because it is difficult, and the BPF becomes large and costly.

[0008]

As shown in the above conventional example, in the conventional filter, the amount of attenuation near the boundary between the own band and the other band is relatively small, and there is no solution to this problem. There was a defect. In particular, for example, in a communication device that communicates a signal in a specific band (own band), if a conventional filter is used, there is a problem that large interference occurs near the boundary and communication quality is degraded. there were.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and has as its object to provide a filter device and a communication device having a sharp characteristic for attenuating unnecessary frequency components of a signal. More specifically, for example, a low-loss, small-sized and economical filter device and a communication device having such a low-loss filter unit are provided.

[0010]

Means for Solving the Problems To achieve the above object, a filter device according to the present invention has the following features.
Attenuates unnecessary frequency components of the signal. That is, the distribution means distributes the signal to be attenuated, and the filter (hereinafter, referred to as
Filter A) attenuates the unnecessary frequency components of one of the divided signals, the attenuating means attenuates the other distributed signal, and the combining means separates the signal attenuated by the filter and the signal attenuated by the attenuating means. The frequency components having the same amplitude are combined in a phase relationship that cancels each other.

Accordingly, at the frequency (band point) having the same amplitude, the amplitude of the combined signal can be reduced (for example, to zero), so that a relatively large attenuation can be secured at the frequency. Thereby, the characteristic of attenuating the unnecessary frequency component of the signal can be sharpened.

Further, in the filter device according to the present invention, a filter (hereinafter, referred to as a filter B) for attenuating unnecessary frequency components of a signal before being distributed by the distribution means or a signal after being synthesized by the synthesis means. Further provision. Therefore, for example, as shown in an embodiment to be described later, in a case where a part where the attenuation of the filter device according to claim 1 of the present invention is smaller than that of the filter A in an unnecessary frequency band occurs. Even so, by providing the filter B, a relatively large attenuation can be ensured even in such a band.

Further, in the communication device according to the present invention, like the above-described filter device, by attenuating the unnecessary frequency components of the communication signal as described below, the characteristic of the attenuation can be sharpened. . That is, the distributing means distributes the communication signal to be attenuated, the filter attenuates an unnecessary frequency component of one distributed signal, the attenuating means attenuates the other distributed signal, and the combining means attenuates the signal attenuated by the filter. And the signal attenuated by the attenuating means are combined in a phase relationship in which frequency components having the same amplitude cancel each other.

Further, in the communication apparatus according to the present invention, a filter for attenuating unnecessary frequency components of a signal before being distributed by the distribution means or a signal after being synthesized by the synthesis means, for example, like the above-described filter apparatus. By further providing, it is possible to compensate for securing a relatively large amount of attenuation in the unnecessary frequency band.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A filter device according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a circuit configuration of the filter device of the present embodiment. This circuit is a filter attenuation compensation circuit for compensating the attenuation of the filter 2. The circuit shown in FIG. 1 includes a distributor 1, a band-pass filter (referred to as a first BPF in this example) 2,
Variable attenuator 3, phase shifter 4, delay circuit 5, synthesizer 6
And a band pass filter (referred to as a second BPF in this example) 7. Note that, in FIG.
Each signal path point is indicated using .about. "G".

The splitter 1 receives a signal to be processed by the filter device of the present embodiment, splits the signal equally into two signals, and splits each split signal into a first BPF 2 and a variable attenuator 3. It has the function of outputting to First B
The PF 2 has a function of receiving one distribution signal output from the distributor 1, filtering the distribution signal, passing a signal in a required pass band, and outputting the signal to the synthesizer 6. Here, in the present example, a general one is used as the first BPF 2, that is, as the filter characteristics of the first BPF 2 of the present example, for example, the same one as shown in FIG. I have. This filter characteristic has symmetry with respect to frequency centering on the own band.

The variable attenuator 3 receives the other split signal output from the splitter 1 and attenuates the split signal (ie, reduces the amplitude of the split signal) and outputs it to the phase shifter 4. And a function capable of variably adjusting the amount of attenuation. Phase shifter 4
Has a function of receiving a signal output from the variable attenuator 3, changing the phase of the signal, and outputting the signal to the delay circuit 5, and variably adjusting the amount of phase change. It has a function that can.

The delay circuit 5 has a function of receiving a signal output from the phase shifter 4, delaying the signal for a predetermined time, and outputting the delayed signal to the synthesizer 6. The synthesizer 6 includes a first BPF
2 and a delay circuit 5
Has a function of inputting a signal output from the second BPF, synthesizing these two signals, and outputting the synthesized signal to the second BPF 7. The second BPF 7 has a function of inputting a synthesized signal output from the synthesizer 6, attenuating unnecessary frequency components of the signal, and outputting the signal.

FIG. 2 shows the first BPF.
2 (“a”-“b” shown in FIG. 1)
-The path of "c"-"f" is shown as an example of the transmission characteristics of the compensated path, and the second path ("a" shown in FIG. 1 shown in FIG. "-
This is a path of “d”-“e”-“f”, and shows an example of the transmission characteristic of the compensation path). Other examples of the transmission characteristic that can be realized by the second path are “and”. Two are indicated by dotted lines.

The horizontal axis in FIG. 2 indicates the frequency (Hz), and the vertical axis indicates the attenuation (dB). The transmission characteristic of the first path is mainly based on the filter characteristic of the first BPF 2, and the transmission characteristic of the second path is mainly based on the attenuation characteristic of the variable attenuator 3.

As shown by the symbol in the figure, the first BP
In F2, near the boundary between the own band and another band adjacent thereto, the signal of the other band is slightly x1 (dB).
Signals that only attenuate but cannot be attenuated pass through and are output to the synthesizer 6. In this example, x1 (d
B) is, for example, equal to x (dB) shown in FIG. Further, as shown by in the figure, the variable attenuator 3
In the above, the signal is attenuated with an attenuation characteristic having a constant attenuation y1 (dB) regardless of the frequency.

In this example, as shown in the figure, the transmission characteristics of the first path and the transmission characteristics of the second
Since the two band points A and B intersect with each other and the attenuation amounts of the first path and the second path are equal at these two band points A and B, the first BPF 2 and the combiner 6 The amplitudes of the signals at the band points A and B output to the synthesizer 6 are equal to the amplitudes of the signals at the band points A and B output to the synthesizer 6 from the delay circuit 5.

The characteristic of the synthesized signal output from the synthesizer 6 is the characteristic of the signal obtained by synthesizing the signal input to the synthesizer 6 from the first BPF 2 and the signal input to the synthesizer 6 from the delay circuit 5. In this example, the two signals to be combined are canceled by the combination at the two band points A and B, that is, the amplitude of the combined signal at the two band points A and B is changed. The amount of phase change in the phase shifter 4 and the delay time in the delay circuit 5 described above are set so as to be small (for example, zero). In this example, the setting can be performed by variably adjusting the amount of phase change in the phase shifter 4 and the delay time in the delay circuit 5, but, for example, the setting is fixedly performed in advance. May be.

FIG. 3 shows an example of the characteristic of the synthesized signal output from the synthesizer 6 (an example of the characteristic at the point "f" shown in FIG. 1). An example of the transmission characteristics and an example of the transmission characteristics of the above-described second path are indicated by dotted lines. Note that the horizontal axis in the figure indicates the frequency (Hz), and the vertical axis indicates the attenuation (dB).

As shown in the figure, the characteristics of the synthesized signal output from the synthesizer 6 indicate, for example, the above-mentioned first B with respect to the vicinity of the boundary between the own band and another band adjacent thereto.
A relatively large amount of attenuation x even at a band point where only a small amount of attenuation x1 (dB) could be secured by PF2
2 can be secured, and further, for example, at the band points A and B where only the relatively small attenuation y1 (dB) can be secured with the above-described first BPF2, the relatively large attenuation y2 (dB) can be secured. ) Can be secured. As described above, in the characteristics of the synthesized signal output from the synthesizer 6 of the present example, it is possible to ensure a sufficiently large amount of attenuation near the boundary between the own band and the other bands, as shown in FIG. The characteristics of attenuating signals in other bands can be sharpened.

The band point where the transmission characteristic of the first path and the transmission characteristic of the second path intersect can be changed by, for example, variably adjusting the amount of attenuation in the variable attenuator 3. FIG. 2 shows, for example, the transmission characteristics of the second path.
(When the attenuation amount is y1 '(dB)), and the two band points A' and B 'that intersect, or when the transmission characteristic of the second path is adjusted as " Two band points A ″ and B ″ that intersect (when the amount of attenuation is y1 ″ (dB)) are shown. Then, similarly to the above, by adjusting the phase shifter 4 and the delay circuit 5 so that the signal component at such an intersection band point is canceled by the combination, the steepness at the intersection band point and the vicinity thereof is obtained as described above. Properties can be obtained.

As a specific example, for example, when the above-mentioned attenuation amount y1 (or y1 ′ or y1 ″) is 20 (dB), the signal of the own band passing through the first path and the second path are transmitted. Even if the signal of the own band passing therethrough is synthesized by the synthesizer 6, the output from the synthesizer 6 is within ± 0.8 (dB) with respect to the amplitude of the signal of the own band passing through the first path. Can be suppressed. As described above, if the above-described attenuation amount y1 (or y1 ′ or y1 ″) is a necessary and sufficient value within a range allowed in the characteristics of the signal of the own band output from the combiner 6, the variable attenuator is used. By adjusting the amount of attenuation at 3, the attenuation amount compensation point of the first BPF 2 can be freely changed.

As described above, in the filter device of this embodiment,
In the output from the synthesizer 6, a relatively large amount of attenuation can be ensured near the boundary between the own band and another band adjacent thereto, whereby the unnecessary frequency components of the signal (that is, other The characteristic of attenuating the signal component of the band can be sharpened.

Further, the second BPF 7 will be described in detail. That is, in this example, the filter 2 to be subjected to attenuation compensation is a band-pass filter.
In the characteristics of the synthesized signal from the synthesizer 6 as shown in FIG.
Outside the band on the low band side of the own band, when the band is lower than the detuning point C, a larger amount of attenuation cannot be secured as compared with the first BPF 2 to be compensated for attenuation. Outside the band on the high frequency side, if the frequency is higher than the detuning point D, it may not be possible to secure a large amount of attenuation as compared with the first BPF 2 to be compensated for attenuation. Note that these two detuning points C and D are intersections between the characteristics of the combined signal and the transmission characteristics of the first path.

Therefore, in the present embodiment, the second BPF 7 is connected to the output side of the synthesizer 6 so that the second BPF 7 is provided on the lower side than the above-mentioned detuning point C and on the higher side than the above-mentioned detuning point D. The amount of attenuation is improved by securing a large amount of attenuation. Here, as the second BPF 7, it is not always necessary to use a filter that is difficult to realize so as to abruptly attenuate a signal component near a boundary between the own band and another band adjacent to the own band. BPF2
It is sufficient if an easy-to-implement filter having a gentler attenuation characteristic is used. In short, it is necessary to attenuate unnecessary frequency components lower than the above-mentioned detuning point C and higher than the above-mentioned detuning point D. Anything that can do it is acceptable.

FIG. 4 shows an example of the filter characteristic of the second BPF 7 as α, in which the horizontal axis represents the frequency (Hz) and the vertical axis represents the attenuation (dB). I have.
FIG. 5 shows an example of the characteristic of the signal output from the second BPF 7 (an example of the characteristic at the point "g" shown in FIG. 1), and the transmission characteristic of the first path described above. Example, characteristic example of the synthesized signal from the synthesizer 6, and the second BPF
The filter characteristic example α of No. 7 is indicated by a dotted line, and the horizontal axis in the figure indicates frequency (Hz), and the vertical axis indicates attenuation (dB).

As described above, in the filter device of this embodiment,
For example, as shown in FIG. 5, in the characteristics of the signal output from the second BPF 7, it is possible to ensure a sufficiently large attenuation near the boundary between the own band and another band adjacent thereto, and A large amount of attenuation can be ensured on the lower frequency side than the detuning point C and on the higher frequency side than the detuning point D. Further, the filter device of this example has a low loss,
In addition, it is possible to construct an economical circuit.

Here, in this example, the distributor 1 according to the present invention is constituted by the function of the distributor 1 equally dividing the signal to be attenuated into two signals. It should be noted that the distribution method is not necessarily equal distribution. Further, in this example, the first BPF 7 has a function of attenuating an unnecessary frequency component of one of the distribution signals, thereby forming a filter according to claim 1 of the present invention. In this example, a band-pass filter (the first BPF 2 in this example) is used as a filter to be compensated for the attenuation. However, for example, a low-pass filter (LPF), a high-pass filter (HPF), and a band elimination filter are used. (BEF) can also be used as a filter to be subjected to attenuation compensation. Various filter characteristics may be used as the filter characteristics of the filter whose attenuation is to be compensated.

In this embodiment, the function of the variable attenuator 3 for attenuating the other distributed signal constitutes the attenuating means according to the present invention. Although the variable attenuator 3 is used in this example, for example, when it is not necessary to adjust the attenuation,
It is also possible to use an attenuator having a fixed attenuation amount as the attenuation means.

In this embodiment, the signal attenuated by the first BPF 2 and the signal attenuated by the variable attenuator 3 are converted into frequency components having the same amplitude by the phase shifter 4 and the delay circuit 5 (this In the example, the intersection band points A and B described above are used.
Are combined by the combiner 6 in such a way that the signal components (the signal components of the two components) cancel each other out to constitute a combining means according to the present invention. In the present invention, the degree of canceling out frequency components having the same amplitude from each other is not limited to completely canceling out (that is, making the synthesis result zero), but may be a degree of canceling out a part. The point is that it is only necessary to be able to obtain steep characteristics that are practically effective.

In this embodiment, the phase of the signal attenuated by the attenuating means (in this embodiment, the variable attenuator 3) is adjusted by changing the phase of the signal by the phase shifter 4 and the delay circuit 5. Any means may be used as the means for performing the above-mentioned operations. For example, the means for adjusting the length of the signal line to adjust the delay time (adjusting the phase), or the means for It is also possible to adopt a configuration in which the phase is adjusted internally.

As an example, in the present embodiment, the delay circuit 5 is provided, but the delay circuit 5 is not necessarily required depending on, for example, the frequency and bandwidth of the required passband, the amount of attenuation to be compensated, and the like. The connection order of the variable attenuator 3, the phase shifter 4, and the delay circuit 5 is not necessarily the one shown in FIG. 1 and may be arbitrary. In this example, the phase change amount can be variably adjusted. However, for example, when it is not necessary to adjust the phase change amount, a phase shifter having a fixed phase change amount may be used. Is also possible.

In this example, unnecessary frequency components of the signal after the second BPF 7 is synthesized by the synthesizer 6 (particularly,
The function of attenuating the unnecessary frequency components lower than the detuning point C and higher than the detuning point D) constitutes a filter according to claim 2 of the present invention. In addition,
In this embodiment, the filter is configured to attenuate the signal after being synthesized by the synthesizing unit (in this embodiment, the synthesizing unit 6). The filter may be connected to the side to attenuate unnecessary frequency components of the signal before the filter is distributed by the distribution means, and the same effect as in the case of this example can be obtained.

In this embodiment, a band-pass filter (the second BPF 7 in this embodiment) is used as the filter. However, for example, a low-pass filter (LPF), a high-pass filter (HPF), and a band elimination filter (B
EF) can also be used, and various filter characteristics may be used as such a filter.

Next, a filter device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an example of a circuit configuration of the filter device of the present embodiment. The configuration of the circuit includes a first directional coupler 11 having a function of equally dividing a signal into two signals, For example, in FIG. 1 of the first embodiment, except that an amplifier 16 having an amplifying function and a second directional coupler 17 having a function of combining two signals are used. The configuration is the same as that of the circuit shown.

Specifically, the circuit shown in FIG. 6 includes, for example, the first BPF 2, the variable attenuator 3, the phase shifter 4, the delay circuit 5, and the second BPF 2 shown in FIG. A band-pass filter (also referred to as a first BPF in this example) 12, a variable attenuator 13, a phase shifter 14, a delay circuit 15, and a band-pass filter (also a second BPF in this example) corresponding to each of the BPFs 7. 18), and the first directional coupler 11 and the second directional coupler 11 have the same functions as those of the distributor 1 and the combiner 6 shown in FIG. 1 of the first embodiment, for example. In this example, an amplifier 16 is connected between the delay circuit 15 and the second directional coupler 17. In the same drawing, each signal path point is indicated using “a ′” to “g ′”, for example, as in FIG. 1 of the first embodiment.

In the following, the filter device of the present embodiment will be mainly described only with respect to points different from the configuration of the filter device shown in FIG. 1 of the first embodiment. That is, in the filter device of the present example, the first directional coupler 11
Distributes the signal to be processed by the filter device of the present example equally into two signals and outputs the two signals to the first BPF 12 and the variable attenuator 13, and the second directional coupler 17 outputs the first BPF
The signal input from the PF 12 and the signal input from the amplifier 16 are combined, and the combined signal is output to the second BPF 18.

In the filter device of this embodiment, the amplifier 1
6 amplifies the signal output from the delay circuit 15 and outputs the amplified signal to the second directional coupler 17. Here, when, for example, a coupler having a coarse coupling degree is used as the first directional coupler 11 or the second directional coupler 17, the points “a ′” and “f ′” shown in FIG. During this period, the required saturated output of the amplifier 16 can also be kept low, for example.

With the above-described configuration, in the filter device of this embodiment, similarly to the filter device of the first embodiment shown in FIG. 1, the attenuation near the boundary between the own band and another band adjacent thereto is obtained. It is possible to ensure a sufficiently large amount, and it is possible to use the second BPF 18 to ensure a large amount of attenuation on the low frequency side and the high frequency side from the detuning point.

In this embodiment, the first directional coupler 11
The function of distributing the signal to be attenuated equally into two signals constitutes the distribution means according to the present invention. Also,
For example, as in the case of the first embodiment, the variable attenuator 13
The order of connecting the phase shifter 14, the delay circuit 15, and the amplifier 16 is not necessarily the one shown in FIG. 6, and may be arbitrary.

Next, a filter device according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 7 shows an example of a circuit configuration of the filter device according to the present embodiment. In this circuit configuration, a band-pass filter 23 is connected to a stage preceding the attenuator 24 provided in the second path. Except for this point, the circuit configuration is the same as that of the circuit shown in FIG. 1 of the first embodiment, for example.

Specifically, the circuit shown in FIG. 7 includes, for example, the distributor 1 and the first BP shown in FIG. 1 of the first embodiment.
F2, a variable attenuator 3, a phase shifter 4, a delay circuit 5, a synthesizer 6, and a distributor 21 corresponding to each of the second BPFs 7,
Bandpass filter (also referred to as a first BPF in this example) 22, variable attenuator 24, phase shifter 25, delay circuit 2
6, the synthesizer 27, the band-pass filter (in this example, the third
In this example, a band-pass filter (referred to as a second BPF in this example) 23 is provided between the distributor 21 and the variable attenuator 24. Have been. In the same drawing, each signal path point is shown using "a" to "g", for example, as in FIG. 1 of the first embodiment.

In the following, the filter device of the present embodiment will be mainly described only with respect to differences from the configuration of the filter device of the first embodiment shown in FIG. 1 and the like. That is, in the filter device of this example, one of the divided signals output from the distributor 21 is input to the first BPF 22, while the other distributed signal is input to the second BPF 23.

The second BPF 23 receives the other split signal output from the splitter 21 and filters the split signal so that, for example, a signal having a wider band than the pass band of the first BPF 22 is passed. And outputs it to the attenuator 24. In this example, the second B
As a filter characteristic of the PF23, for example, the first BPF2
As in the case of No. 2, the one having symmetry with respect to the frequency around the own band is used. Further, the attenuator 24 of the present example
Attenuates the signal input from the second BPF 23 and outputs the signal to the phase shifter 25.

FIG. 8 shows the first BPF.
22 (the "a""-
A transmission characteristic example of “b ″” − “c ″” − “f ″”) is shown as an example, and the second BPF 2
3 or the second path passing through the variable attenuator 24 (the path of “a”-“d”-“e”-“f” ”shown in FIG. 7).
And the other transmission characteristics that can be realized by the second path are indicated by two dotted lines as' and ''.

The horizontal axis in FIG. 8 indicates frequency (Hz), and the vertical axis indicates attenuation (dB). The transmission characteristic of the first path is mainly based on the filter characteristic of the first BPF 22, and the transmission characteristic of the second path is mainly based on the filter characteristic of the second BPF 23 and the attenuation characteristic of the variable attenuator 24. Things.

The feature of the filter device of this embodiment is that the transmission characteristics of the second path are different from those having a constant attenuation regardless of the frequency as shown in the first embodiment, for example. Specifically, in this example, as shown in FIG. 8, for example, as shown in FIG. 8, a transmission characteristic is realized in the second path such that the attenuation outside the own band gradually increases as the frequency moves away from the own band. Have been.

Note that w1 (dB) and z1 shown in FIG.
(DB), z1 ′ (dB) and z1 ″ (dB) are, for example, x1 (d) shown in FIG. 2 of the first embodiment.
B), y1 (dB), y1 ′ (dB), y1 ″ (dB)
However, the values do not always match in the case of the first embodiment and the case of the present example. For example, the filter characteristics of the first BPF 22 and the filter characteristics of the second BPF 23, etc. It is decided according to.

The two points E and F shown in FIG.
A band point at which the transmission characteristic of the first path and the transmission characteristic of the second path intersect in another band is shown. Further, such an intersection band point can be changed by, for example, variably adjusting the amount of attenuation in the variable attenuator 24. In FIG. Two band points E 'and F' that intersect when adjusted as described above, and two band points E "and F" that intersect when the transmission characteristic of the second path is adjusted as "", for example. Is shown.

In this embodiment, as in the case of the first embodiment, for example, two signals to be synthesized by the synthesizer 27 are canceled by the synthesis at the two band points E and F. , The amount of phase change in the phase shifter 25 and the delay time in the delay circuit 26 are set.

FIG. 9 shows an example of the characteristic of the synthesized signal output from the synthesizer 27 (an example of the characteristic at the point "f""shown in FIG. 7).
Are shown as dotted lines, and the transmission characteristics of the first path and the transmission characteristics of the second path are indicated by dotted lines. Note that the horizontal axis in the figure indicates the frequency (Hz), and the vertical axis indicates the attenuation (dB).

As shown in the figure, the characteristics of the synthesized signal output from the synthesizer 27 indicate that the first BPF 22 has a slight attenuation in the vicinity of the boundary between the own band and another band adjacent thereto. A relatively large amount of attenuation w2 can be secured even at a band point where only the amount w1 (dB) can be secured. Further, for example, the first BPF 22 described above has only a relatively small amount of attenuation z1 (dB). A relatively large attenuation z2 (dB) can be ensured even at the band points E and F that could not be secured.

Further, in this example, the second BPF 2
3, the characteristics of the synthesized signal of this example are as follows.
A relatively large amount of attenuation can be ensured even in the lower band than the detuning point G existing outside the lower band of the own band. Similarly, the detuning point H existing outside the higher band of the own band can be secured. A relatively large attenuation can be ensured even in a higher frequency range. Note that these two detuning points G and H are intersections between the characteristics of the combined signal and the transmission characteristics of the first path.

As described above, in the filter device of this embodiment,
In the output from the combiner 27, for example, as shown in FIG. 1 of the first embodiment, it is possible to ensure a relatively large amount of attenuation near the boundary between the own band and another band adjacent thereto. In this example, the second BPF 23
, It is possible to ensure a relatively large amount of attenuation on the low frequency side and the high frequency side from the detuning point.

Also, in this embodiment, as in the case of the first embodiment, for example, the third BPF
The third BPF 28 is provided, for example, on the lower frequency side than the detuning point G and the detuning point H described above.
The attenuation on the higher frequency side is further improved.

FIG. 10 shows an example of the characteristic of the signal output from the third BPF 28 (an example of the characteristic at the point "g" shown in FIG. 7). Are shown by dotted lines, the transmission characteristic example of the third embodiment, the characteristic example of the combined signal from the combiner 27, and the filter characteristic example β of the third BPF 28 are indicated by dotted lines, and the horizontal axis in FIG. The amount (dB) is shown.

In this example, the function of the second BPF 23 and the variable attenuator 24 for attenuating the other distribution signal is as follows.
The damping means according to the present invention is configured. Here, as the attenuation means, for example, an attenuation characteristic such that an intersection band point between the transmission characteristic of the first path and the transmission characteristic of the second path can be adjusted to a band point required to secure a relatively large amount of attenuation. Various configurations may be used as long as they have. Also, for example, as in the case of the first embodiment, the second
The connection order of the BPF 23, the variable attenuator 24, the phase shifter 25, and the delay circuit 26 need not always be the one shown in FIG. 7 and may be arbitrary.

Next, a relay station apparatus according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an example of a relay station apparatus which is an embodiment of a communication apparatus according to the present invention. This relay station apparatus is provided in, for example, a wireless communication system and has a function of amplifying and relaying a wireless signal. ing.

The relay station device shown in FIG. 1 includes two antennas 31 and 36 for transmitting and receiving radio signals, and two duplexers 32 for enabling transmission and reception with one antenna.
35 and two filter attenuations having the same circuit configuration as the filter device shown in any one of FIG. 1 of the first embodiment, FIG. 6 of the second embodiment, and FIG. 7 of the third embodiment. Compensation circuits 33 and 37 and two amplifiers 34 and 38 for amplifying a communication signal are provided.

The filter attenuation compensation circuits 33, 3
7, a communication signal is transmitted to each filter attenuation compensation circuit 33;
It has a function of passing a frequency component to be relayed when passing through 37 and attenuating unnecessary frequency components other than the frequency component with a steep characteristic.

With such a configuration, in the relay station apparatus of this embodiment, for example, a signal wirelessly received from the base station apparatus or the like by the antenna 31 is input to the filter attenuation compensation circuit 33 via the duplexer 32, Is filtered by the filter attenuation compensation circuit 33 and amplified by the amplifier 34, and then transmitted to the antenna 36 via the duplexer 35.
To the terminal station device and the like. Further, the relay amplification from the terminal station device or the like to the base station device or the like is similarly performed using the other filter attenuation compensation circuit 37 and the other amplifier 38.

As described above, in the relay station apparatus of this embodiment, for example, the components of the required passband of the signal (the communication signal in this embodiment) are similar to those shown in the first to third embodiments. Is relayed by using the filter attenuation compensation circuits 33 and 37 that can pass the signal with steep characteristics, so that the communication quality in the system can be improved.

Next, a base station apparatus according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an example of a base station apparatus which is an embodiment of a communication apparatus according to the present invention. This base station apparatus is provided in, for example, a wireless communication system, and wirelessly communicates with a terminal station apparatus and the like. It has a function of communicating signals and a function of communicating signals with other base station devices and the like via a wired line or the like.

The base station apparatus shown in FIG. 9 includes an antenna 41 for transmitting and receiving radio signals, a duplexer 42 for enabling transmission and reception with one antenna 41, and for example, a diagram of the first embodiment. 1, a filter attenuation compensation circuit 43 having a circuit configuration similar to that of the filter device shown in FIG. 6 of the second embodiment or FIG. 7 of the third embodiment, and two amplifiers for amplifying a communication signal. 44, 48, a demodulator 45 for demodulating a signal, a modulator 47 for modulating a signal, and a control unit 46 for controlling the processing units 41 to 45, 47, 48 and the like.
And are provided.

When the communication signal received by the antenna 41 passes through the filter attenuation amount compensating circuit 43, the filter attenuation amount compensating circuit 43 passes a frequency component (channel) to be received. It has a function to attenuate unnecessary frequency components other than the components with steep characteristics.

With such a configuration, in the base station apparatus of this example, a signal wirelessly received from, for example, a terminal station apparatus by the antenna 41 is input to the filter attenuation compensation circuit 43 via the duplexer 42, Is filtered by the filter attenuation compensation circuit 43 and amplified by the amplifier 44, and then the signal is demodulated by the demodulator 45 and output to a wired line or the like via the control unit 46. In the base station apparatus of the present example, for example, after a signal input to the control unit 46 from a wired line or the like is modulated by the modulator 47, the signal is amplified by the amplifier 48, and the antenna 41 is transmitted through the duplexer 42. To the terminal station device and the like.

As described above, in the base station apparatus according to the present embodiment, for example, the components of the required passband of the signal (the communication signal in the present embodiment) are similar to those shown in the first to third embodiments. Since the communication signal is received using the filter attenuation amount compensating circuit 43 which can pass the signal with steep characteristics, the reception quality of the signal can be improved.

Next, a terminal station apparatus according to a sixth embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an example of a terminal station apparatus which is an embodiment of a communication apparatus according to the present invention. This terminal station apparatus is provided in, for example, a wireless communication system and wirelessly communicates with a base station apparatus and the like. It has the function of communicating signals. In addition, as the terminal station device, for example, PH
There are an S terminal station device and a mobile phone terminal device.

The terminal station apparatus shown in FIG. 7 includes an antenna 51 for transmitting and receiving a radio signal, a duplexer 52 for enabling transmission and reception with one antenna 51, for example, a diagram of the first embodiment. 1, a filter attenuation compensation circuit 53 having a circuit configuration similar to that of the filter device shown in FIG. 6 of the second embodiment or FIG. 7 of the third embodiment, and two amplifiers for amplifying a communication signal. 54, 60, a demodulator 55 for demodulating a signal, an output unit 57 including, for example, a speaker for outputting an audio signal, and an input unit 58 including, for example, a microphone for inputting an audio signal, and modulating the signal. A modulator 59 and a control unit 56 for controlling the processing units 51 to 55 and 57 to 60 are provided.

When the communication signal received by the antenna 51 passes through the filter attenuation amount compensating circuit 53, the filter attenuation amount compensating circuit 53 passes a frequency component (channel) to be received, while It has a function to attenuate unnecessary frequency components other than the components with steep characteristics.

With such a configuration, in the terminal station apparatus of this example, a signal wirelessly received from, for example, a base station apparatus by an antenna 51 is input to a filter attenuation compensation circuit 53 via a duplexer 52, Is filtered by the filter attenuation compensation circuit 53 and amplified by the amplifier 54, and then the signal is demodulated by the demodulator 55 and output from the output unit 57 via the control unit 56 as an audio signal. In the terminal station device of this example, for example, the input unit 58
The audio signal input from the
9, the signal is amplified by an amplifier 60, and transmitted wirelessly from an antenna 51 to a base station device or the like via a duplexer 52.

As described above, in the terminal station apparatus of the present embodiment, for example, the components of the required passband of the signal (communication signal in this example) are similar to those shown in the first to third embodiments. Since the communication signal is received using the filter attenuation compensation circuit 53 that can pass the signal with a steep characteristic, the reception quality of the signal can be improved.

Here, the configuration of the filter device according to the present invention is not necessarily limited to those described in the first to third embodiments, and various configurations may be used. Similarly, the configuration of the communication device according to the present invention is not necessarily limited to those described in the fourth to sixth embodiments, and various configurations may be used.

As an example, the filter device according to the present invention can be applied to various fields where it is necessary to attenuate unnecessary frequency components of a signal. Similarly, the communication device according to the present invention can be applied to various communication fields in which unnecessary frequency components of a communication signal need to be attenuated. For example, various communication devices such as a PHS system and a mobile phone system can be used. It can be applied to various communication systems.

The various processes performed by the filter device according to the present invention and the communication device according to the present invention include, for example, a processor executing a control program stored in a ROM in a hardware resource including a processor and a memory. By doing so, it is also possible to adopt a configuration that is controlled, and for example, it is also possible to configure each functional means for executing the processing as an independent hardware circuit. In addition, the present invention can be understood as a computer-readable recording medium such as a floppy disk or a CD-ROM storing the above-mentioned control program. Thereby, the processing according to the present invention can be performed.

[0081]

As described above, according to the filter device and the communication device of the present invention, for example, a signal to be attenuated is distributed, and unnecessary frequency components of one of the distributed signals are attenuated by the filter. The other distributed signal is attenuated by an attenuator or the like, and the signal attenuated by the filter and the signal attenuated by the attenuator or the like are combined in a phase relationship in which frequency components having the same amplitude cancel each other. Therefore, a relatively large amount of attenuation can be ensured at the frequency, whereby the characteristic of attenuating unnecessary frequency components of the signal can be sharpened.

Further, the filter device according to the present invention and the communication device according to the present invention, as a further preferred embodiment, are provided with a filter for attenuating unnecessary frequency components of the signal before distribution and the signal after synthesis described above. For example, the first
As shown in the embodiments and the like, in the configuration according to claims 1 and 3 of the present invention, even when there is a portion where the amount of attenuation becomes relatively small in an unnecessary frequency band,
It is possible to compensate for securing a relatively large amount of attenuation in such a band.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a transmission characteristic example of a first path and a transmission characteristic example of a second path according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a characteristic example of a synthesized signal according to the first example of the present invention.

FIG. 4 is a diagram illustrating an example of a filter characteristic of a second BPF according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a characteristic example of an output from a second BPF according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a circuit configuration example of a filter device according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a circuit configuration example of a filter device according to a third embodiment of the present invention.

FIG. 8 is a diagram illustrating a transmission characteristic example of a first path and a transmission characteristic example of a second path according to a third embodiment of the present invention.

FIG. 9 is a diagram illustrating a characteristic example of a composite signal according to the third example of the present invention.

FIG. 10 is a diagram illustrating a characteristic example of an output from a third BPF according to a third embodiment of the present invention.

FIG. 11 is a diagram illustrating an example of a relay station device according to a fourth embodiment of the present invention.

FIG. 12 is a diagram illustrating an example of a base station device according to a fifth embodiment of the present invention.

FIG. 13 is a diagram illustrating an example of a terminal station device according to a sixth embodiment of the present invention.

FIG. 14 is a diagram illustrating an example of filter characteristics of a bandpass filter.

FIG. 15 is a diagram illustrating an example of filter characteristics of an ideal bandpass filter.

[Explanation of symbols]

1, 21,... Distributor, 2, 7, 12, 18, 22, 2,
3, 28 band filter, 3, 13, 24
Variable attenuator, 4, 14, 25 ··· phase shifter, 5, 15,
26 delay circuits, 6, 27 synthesizers, 11, 17
..Directional couplers, 16, 34, 38, 44, 48, and 5
4, 60 ··· amplifier, 31, 36, 41, 51 · · antenna, 32, 35, 42, 52 · · duplexer, 33,
37, 43, 53... Filter attenuation compensation circuit, 45,
55 demodulator, 46, 56 control unit, 47, 5
9 ··· Modulator, 57 ··· Output part, 58 ··· Input part,

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yoichi Okubo 3-14-20 Higashinakano, Nakano-ku, Tokyo Kokusai Denki Co., Ltd. F-term (reference) 5J024 AA02 CA10 CA11 CA14 CA15 CA17 EA03 KA02

Claims (4)

[Claims] 1. A filter device for attenuating an unnecessary frequency component of a signal, a distribution unit for distributing a signal to be attenuated, a filter for attenuating an unnecessary frequency component of one of the distributed signals, and an attenuating other distributed signal. Attenuating means, and synthesizing means for synthesizing the signal attenuated by the filter and the signal attenuated by the attenuating means in a phase relationship in which frequency components having the same amplitude cancel each other. Filter device. 2. The filter device according to claim 1, further comprising a filter for attenuating an unnecessary frequency component of a signal before being distributed by the distribution unit or a signal after being synthesized by the synthesis unit. Filter device. 3. A communication device for attenuating an unnecessary frequency component of a communication signal, comprising: a distribution unit for distributing a communication signal to be attenuated; a filter for attenuating an unnecessary frequency component of one of the distribution signals; Attenuating means for attenuating, and synthesizing means for synthesizing the signal attenuated by the filter and the signal attenuated by the attenuating means in a phase relationship in which frequency components having the same amplitude cancel each other out. Characteristic communication device. 4. The communication device according to claim 3, further comprising a filter for attenuating an unnecessary frequency component of the signal before being distributed by the distribution means or the signal after being synthesized by the synthesis means. Communication device.