JP2000295120A - Interference wave level detection circuit, narrow band interference wave limiting device using the same and communication equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interference wave level detection circuit detecting the level of a narrow band interference wave by connecting power detectors to an input side and an output side and obtaining the level of the narrow band infrequence wave containing in an inputted signal. SOLUTION: A signal inputted from an input terminal 2 is amplified by an amplification rate variable amplifier 4 and is divided into two by a signal distributor 21. One is inputted an static wave filter 22 and the other is inputted to a power detector 24. The signal outputted from the static magnetic wave filter 22 is divided into two by a signal distributor 23 and one signal is outputted from an output terminal 7 and other is inputted to a power detector 25. The outputs of the power detectors 24 and 25 are inputted to a power difference detector 26. The power difference detector 26 detects the difference of power detected by the two power detectors 24 and 25, namely, power limited by the static magnetic wave filter 22 among the power of a narrow band interference wave. Thus, the level of the narrow band interference wave can be detected in an interference wave level defector 29.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interference wave level detecting circuit, a narrow band interference wave limiting device using the same, and a communication device using the same, and more particularly, a mixed signal in a frequency band occupied by spread signals in spread spectrum communication. The present invention relates to an interference wave level detection circuit for detecting the level of a narrow band interference wave, a narrow band interference wave limiting device using the same, and a communication device using the same.

[0002]

2. Description of the Related Art With the spread of spread spectrum communication in recent years, a problem has arisen that a narrow band interference wave is mixed into an occupied frequency band of a spread signal and communication quality is deteriorated. There is a need for a device that limits the narrow-band interference wave.

FIG. 7 shows a conventional narrow-band interference wave limiting device. The basic configuration of the narrow-band interference wave limiting device 1 shown in FIG. 7 is disclosed in Japanese Patent Application Laid-Open No. 9-214397.

In FIG. 7, a narrow-band interference wave limiting device 1 is shown.
Is connected to the input terminal 2, the signal distributor 3 connected to the input terminal 2, the variable gain amplifier 4 connected to one output of the signal distributor 3, and the other output of the signal distributor 3. A level detection circuit 5, a magnetostatic wave filter 6 which is a frequency selective type level limiting circuit connected to the variable amplification factor amplifier 4,
It comprises an output terminal 7 connected to a magnetostatic wave filter 6. The amplification factor variable amplifier 4 has an amplification factor control terminal 4a, and the level detection circuit 5 is connected to the amplification factor control terminal 4a. Here, the magnetostatic wave filter 6 has a function of frequency-selectively limiting a signal having a level equal to or higher than the saturation level within the band to the saturation level.
In other words, it is possible to limit a signal having a frequency that is equal to or higher than the saturation level of the magnetostatic wave filter 6 on the frequency axis to the saturation level. Conversely, level restriction is not performed on a signal having a frequency that does not reach the saturation level of the magnetostatic wave filter 6. The magnetostatic wave filter 6 has not only a frequency-selective level limitation but also an insertion loss over the entire band. The level detection circuit 5 detects the level of the spread signal included in the signal input to the input terminal 2, and determines the level of the spread signal output from the amplification factor variable amplifier 4 to the saturation level of the magnetostatic wave filter 6. The amplification factor variable amplifier 4 is controlled so as to substantially coincide with. At this time, if a narrow-band interference wave is mixed in the input signal, it is also amplified at the same amplification factor. Here, the signal level means the power of the signal within a certain narrow frequency bandwidth. Therefore, the level matches the power in the narrowband interference wave.

When a spread signal is input from the input terminal 2 in the narrow-band interference wave limiting device 1 configured as described above, the level of the spread signal is reduced by the variable gain amplifier 4 via the signal distributor 3. The signal is amplified to the saturation level of the magnetic wave filter 6. When the amplified signal is input to the magnetostatic wave filter 6, signals having a saturation level or higher are limited in the magnetostatic wave filter 6 in a frequency-selective manner. That is, if a narrow band interference wave higher than the saturation level of the magnetostatic wave filter 6 is mixed, the saturation level of the magnetostatic wave filter 6, that is, the level of the spread signal in this case is limited. In this way, the level of the narrowband interference wave is limited to the level of the spread signal, and output from the output terminal 7.

FIG. 8 shows the configuration of the level detection circuit 5. In FIG. 8, the level detection circuit 5 includes an input terminal 1
It comprises one or three bandpass filters 12, 13, 14, three detectors 15, 16, 17, a level comparison circuit 18, and an output terminal 19. Three bandpass filters 1
The input sides of 2, 13, and 14 are combined into one and connected to the input terminal 11, and the output sides are detectors 15, 16,
17 is connected to a level comparator 18. The output of the level comparison circuit 18 is connected to an output terminal 19.

FIG. 9 shows a spectrum of a spread signal input to the level detection circuit 5 and three band-pass filters 12 and 1.
3 and 14 are shown. In FIG. 9, 11s indicates a spread signal, and 12w, 13w, and 14w indicate pass bands of three band-pass filters 12, 13, and 14, respectively. As shown in FIG. 9, the three band-pass filters 12, 13, 14
Are set near the center of the frequency band of the spread signal so that they do not overlap with each other.

In FIG. 8, a spread signal input from an input terminal 11 is divided into three, and input to detectors 15, 16, and 17 via three band-pass filters 12, 13, and 14, respectively. Since the spread signal is distributed almost uniformly in the frequency band, as shown in FIG. 9, the spread signals input to the detectors 15, 16, and 17 have substantially the same level. However, when a narrow-band interference wave is added to the spread signal, the output of the band-pass filter including the frequency of the narrow-band interference wave in the pass band is higher in level than the outputs of the other band-pass filters. Therefore, three detectors 1
The outputs of 5, 16 and 17 are compared by a level comparing circuit 18,
The signal with the lowest level is the level of the spread signal, and the signal with the highest level is the level of the narrowband interference wave. In this way, the levels of the spread signal and the narrow-band interference wave are detected.

Although the level detection circuit 5 of FIG. 8 has three band-pass filters, the detection accuracy of the level of the spread signal increases as the number of band-pass filters is increased and the pass band is narrowed.

[0010]

However, in the level detection circuit 5 shown in FIG. 8, the number of parts is large,
There is a problem that the configuration is complicated. In addition, there is a problem that a high-precision band-pass filter having a narrow band is required, which increases the price. In addition, there is a problem that accuracy is reduced when the power density of the spread signal is not uniform.

Further, if there is a narrow band interference wave outside the band of the band pass filter, the level of the narrow band interference wave cannot be detected. If the level of the narrow-band interference wave cannot be detected, the narrow-band interference using a plurality of magnetostatic wave filters is used to avoid the involvement of a spread signal as disclosed in Japanese Patent Application Laid-Open No. 10-224263. In a narrow-band interference wave limiting device configured to limit waves little by little, there is a problem that narrow-band interference waves cannot be efficiently limited.

Accordingly, the present invention provides an interference wave level detection circuit capable of detecting the level of a narrow band interference wave, a narrow band interference wave limiting device using the same, and a communication device using the same.

[0013]

In order to achieve the above object, an interference wave level detecting circuit according to the present invention is connected to an input side of a frequency-selective level limiting circuit, A first power detector for detecting the power of a signal input to the frequency-selective level limiting circuit; and a signal connected to the output side of the frequency-selective level limiting circuit and output from the frequency-selective level limiting circuit. A second power detector for detecting the power of the signal, and the level of the narrow-band interference wave included in the signal input to the frequency-selective level limiting circuit connected to the first and second power detectors. And an interference wave level calculation circuit to be determined.

Further, the interference wave level detection circuit of the present invention
A variable gain amplifier having a gain control terminal for changing the power of a signal input to the frequency selective type level limiting circuit; and a sweep control of the gain of the variable gain amplifier from a low gain to a high gain. A gain sweeping circuit that switches the interference wave level calculation circuit and the gain sweeping circuit to the gain control terminal of the variable gain amplifier.

Further, the interference wave level detection circuit of the present invention
A second frequency-selective level limiting circuit is provided at a stage preceding the frequency-selective level limiting circuit, and is connected to an input side of the second frequency-selective level limiting circuit. A third power detector for detecting the power of an input signal; and a third power detector connected to an output side of the second frequency-selective power limiting circuit for detecting a signal output from the second frequency-selective level limiting circuit. A fourth power detector for detecting power, wherein the third power detector and the fourth power detector are connected to the interference wave level calculation circuit.

Further, the narrow-band interference wave limiting device of the present invention comprises:
An interference wave level detection circuit according to any one of the above is used.

Further, a communication apparatus according to the present invention is characterized by using the above narrow band interference wave limiting apparatus.

With such a configuration, the interference wave level detection circuit of the present invention can detect the level of the narrow band interference wave of the spread signal in which the narrow band interference wave is mixed in the occupied frequency band.

In the narrow band interference wave limiting device of the present invention, the narrow band interference wave can be effectively limited with a simple configuration.

Further, in the communication device according to the present invention, it is possible to prevent communication quality from deteriorating.

[0021]

FIG. 1 shows an embodiment of a narrow band interference wave limiting device using an interference wave level detection circuit according to the present invention. 1, the same or equivalent parts as those in FIG. 7 are denoted by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, a narrow band interference wave limiting device 20
Connects a signal distributor 21 to the output of the variable amplification factor amplifier 4, connects one output to a magnetostatic wave filter 22 which is a frequency-selective level limiting circuit, and connects the other output to a first power detector. It is connected to a certain power detector 24. Also,
A signal distributor 23 is connected to the output of the magnetostatic wave filter 22,
One output is connected to the output terminal 7 and the other output is connected to a power detector 25 which is a second power detector.
The output of the power detector 24 is connected to both the power difference detector 26 and the level calculator 27. The output of the power detector 25 is connected to the power difference detector 26. Power difference detector 2
The output of 6 is connected to a level calculator 27. The output of the level calculator 27 is connected to the gain control terminal 4a of the gain variable amplifier 4. Among them, the power difference detector 26 and the level calculator 27 constitute an interference wave level calculation circuit 28. Further, a signal distributor 21, a magnetostatic wave filter 22, a signal distributor 23, power detectors 24 and 25,
The interference wave level calculation circuit 28 constitutes an interference wave level detection circuit 29.

FIG. 2 shows the frequency characteristic (a) of the signal inputted to the magnetostatic wave filter 22 and the frequency characteristic (FIG. 2) of the signal outputted from the magnetostatic wave filter 22 for the narrow-band interference wave limiting device 20 thus configured. b) will be described, and the description will be given in combination with FIG.

First, the signal input from the input terminal 2 is amplified by the variable amplification factor amplifier 4 and divided into two signals by the signal distributor 21, one of which is input to the magnetostatic wave filter 22, and the other is the power It is input to the detector 24. As shown in FIG. 2A, the signal input to the magnetostatic wave filter 22 has a narrow-band interference wave x mixed into the spread signal y. The level of the narrow-band interference wave x is higher than the saturation level r of the magnetostatic wave filter 22. The power detector 24 considers the distribution ratio of the signal distributor 21 and considers the power of the entire signal input to the magnetostatic wave filter 22, that is, the spread signal y and the narrow band interference mixed in the frequency band of the spread signal y. The power combined with the wave x is detected. Here, the power detected by the power detector 24 is Pa.

In the magnetostatic wave filter 22, a signal having a level higher than the saturation level r is frequency-selectively limited. Here, the level of the narrow-band interference wave x is limited, and the narrow-band interference wave x ′ is obtained.

The signal output from the magnetostatic wave filter 22 is split into two by a signal splitter 23, one of which is output from the output terminal 7, and the other is input to the power detector 25. The power detector 25 considers the distribution ratio of the signal distributor 23 and considers the power of the entire signal output from the magnetostatic wave filter 22, that is, the spread signal y and the narrow band interference mixed in the frequency band of the spread signal y. The power combined with the wave x ′ is detected, and the amount of attenuation in the magnetostatic wave filter 22 over the entire frequency band is corrected. FIG. 2B shows a signal output from the magnetostatic wave filter 22 added to the magnetostatic wave filter 22.
7 shows the frequency characteristics after the attenuation amount is corrected. FIG.
As shown in (b), the level of the spread signal y does not change, and only the narrowband interference wave x is level-limited to the saturation level r of the magnetostatic wave filter 22 to be a narrowband interference wave x '. That is, since the power of the spread signal y does not change, the power detector 25 detects power in which the narrow-band interference wave is reduced by an amount corresponding to the level restriction from x to x ′.
Here, the power detected by the power detector 25 is Pa ′.

The outputs of the power detectors 24 and 25 are input to a power difference detector 26. The power difference detector 26 detects the powers Pa and Pa ′ detected by the two power detectors 24 and 25.
, That is, the power limited by the magnetostatic wave filter 22 out of the power of the narrow-band interference wave x. here,
The power difference detected by the power difference detector 26 is defined as Ps.

The output of the power difference detector 26 is a level calculator 2
7 is input. The output of the power detector 24 is also input to the level calculator 27.

Here, for the power difference Ps detected by the power difference detector 26, the following holds: Ps = Pa−Pa ′ (1) Further, assuming that the power of the narrowband interference wave x is Px and the power of the spread signal y is Py among the power Pa input to the magnetostatic wave filter 22, Pa = Px + Py (2) Further, among the power Pa ′ output from the magnetostatic wave filter 22, the power of the spread signal y remains Py and the power of the narrow-band interference wave x ′ whose level is limited is Px ′, so that Pa ′ = Px ′ + Py (3) Further, the suppression ratio a of the narrow-band interference wave is given by: a = Px / Px ′ (4) Then, Equations (2), (3), and (4) are added to Equation (1).
And solving for Px, Px = Ps × a / (a−1) (5) is obtained. Also, by substituting equation (5) into equation (2), Py
, Py = Pa−Ps × a / (a−1) (6) is obtained. In equations (5) and (6), since Pa and Ps are measured by the power detectors 24 and 25 and the power difference detector 26, the unknowns are Px, Py, and a. If one of them is known, the remaining two can be obtained from equations (5) and (6).

In a system such as a cellular phone using a spread spectrum signal, the power of the spread signal arriving at the base station is sometimes controlled to a specific value. The power Py of y becomes known. Therefore, in the level calculator 27,
The power Px of the narrowband interference wave x and the suppression ratio a of the narrowband interference wave can be calculated. Since the narrow-band interference wave has a narrow band, the power Px is equal to the level of the narrow-band interference wave. In this way, the interference wave level detector 29 can detect the level of the narrow band interference wave.

The output of the level calculator 27 is connected to an amplification factor control terminal 4a of the amplification factor variable amplifier 4, and controls the amplification factor of the amplification factor variable amplifier 4 based on the detected level of the narrow band interference wave x. In addition, the level limiting amount of the narrow-band interference wave in the magnetostatic wave filter 22 can be controlled.

As described above, in the narrow-band interference wave limiting device 20, the level of the narrow-band interference wave can be detected by using the interference wave level detection circuit 29. It can be set freely, and control such as limiting narrow-band interference waves at a level at which no entanglement occurs becomes easy.

In the interference wave level calculation circuit 28, the two power detectors 24 and 25 are followed by the power difference detector 2
6 and the level calculator 27 are individually connected to form an analog circuit, but may be digitally processed using a microcomputer or the like.

The interference wave level detection circuit 29 used in the narrow band interference wave limiting device 20 shown in FIG. 1 can detect the level of the narrow band interference wave only when the power Py of the spread signal y is known. it can. However, in actual spread spectrum communication, the power Py of the spread signal y included in the received signal is often unknown, and an interference wave level detection circuit applicable in such a case is also required.

FIG. 3 shows another embodiment of the narrow band interference wave limiting device using the interference wave level detection circuit of the present invention. FIG.
In FIG. 7, the same or equivalent parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 3, the narrow-band interference wave limiting device 30
Is connected to a variable gain amplifier 31 having a gain control terminal 31a between the input terminal 2 and the signal distributor 21. The gain control terminal 31a of the gain variable amplifier 31 is connected to the output of the switch 32, one input of the switch 32 is connected to the level calculator 27 of the interference wave level detection circuit 28, and the other input of the switch 32 is amplified. Rate sweep circuit 3
3 is connected. That is, the amplification factor variable amplifier 31
Is configured to be controlled by either the interference wave level detection circuit 29 or the amplification factor sweep circuit 33. Among them, signal distributor 21, magnetostatic wave filter 22, signal distributor 23, power detectors 24 and 25, power difference detector 26, level calculator 27, variable amplification factor amplifier 31, switch 3
2. The amplification factor sweep circuit 33 constitutes an interference wave level detection circuit 34. As a result, the interference wave level detection circuit 34 constitutes the narrow band interference wave limiting device 30 as it is.

The operation of the narrow-band interference wave limiting device 30 configured as described above will be described below. Here, it is assumed that the power of the spread signal input to the input terminal 2 is unknown, and that the occupied frequency band of the spread signal is mixed with a narrow-band interference wave whose power is also unknown.

First, the gain sweep circuit 33 is connected to the gain control terminal 31a of the variable gain amplifier 31, and the gain of the variable gain amplifier 31 is controlled to be swept from a low gain to a high gain. As a result, the signal input to the magnetostatic wave filter 22 is swept from low power to high power.

FIG. 4 shows the relationship between the input power and the difference between the input power and the output power (power difference) when the spread signal mixed with the narrow-band interference wave passes through the magnetostatic wave filter 22. This power difference can be detected by the power difference detector 26. As for the output power, the magnetostatic wave filter 2
It is assumed that the insertion loss due to No. 2 has been corrected.

First, when both the level of the spread signal and the level of the narrow-band interference wave are lower than the saturation level of the magnetostatic wave filter 22 (when the input power is equal to or less than P1), the frequency selection by the magnetostatic wave filter 22 is performed. Since there is no level limitation, the power difference remains at 0.

Next, when the level of the narrow band interference wave is higher than the saturation level of the magnetostatic wave filter 22, and the level of the spread signal is lower than the saturation level of the magnetostatic wave filter 22 (when the input power is P1 or more and P2 or less). Since only the narrow-band interference wave is frequency-selectively limited, the power difference increases in a curve as shown in FIG.

When both the level of the spread signal and the level of the narrow band interference wave are higher than the saturation level of the magnetostatic wave filter 22 (when the input power is equal to or higher than P2), not only the narrow band interference wave but also the spread band Since the level of the signal is also frequency-selectively limited, the limited power rapidly increases, and the power difference also rapidly increases as shown in FIG.

As described above, by checking the power difference between the signals passing through the magnetostatic wave filter 22 while increasing the power input to the magnetostatic wave filter 22, both the power of the spread signal and the power of the narrow band interference wave can be obtained. Is unknown, the input power P1 when the level of the narrow-band interference wave matches the saturation level of the magnetostatic wave filter and the input power P2 when the level of the spread signal matches the saturation level of the magnetostatic wave filter are detected. Can be.

When the input power is between P1 and P2, only the narrow band interference wave is level-limited by the magnetostatic wave filter 22. Therefore, the input power is changed from P1 to P
2, two input powers Pb and Pc (for example, Pb is P1
The output powers Pb ′ and Pc ′ at that time are detected by the power detector 25, and the power difference detector 26 calculates the power difference.
At this time, the amount of change in the input power Pc with respect to the input power Pb is known (in this case, 3 dB). Moreover, the power difference at this time is due to the level restriction of only the narrowband interference wave. Therefore, the limited level of the narrow band interference wave is equal to the difference between the input power Pb and the input power Pc. Thus, the suppression ratio of the narrow-band interference wave when the input power is Pc is obtained from Equation (4) (in this case, suppression is 3 dB, so the suppression ratio a = 2).

When the suppression ratio a is obtained, the power Px of the narrowband interference wave and the power Py of the spread signal when the input power is Pc can be obtained from the equations (5) and (6).

Once the power Px of the narrow-band interference wave, that is, the level of the narrow-band interference wave is determined, the output of the level calculator 27 is connected to the gain control terminal 31a of the gain variable amplifier 31, and the calculated narrow-band interference wave is output. The limiting amount of the narrow-band interference wave in the magnetostatic wave filter 22 can be controlled by controlling the amplification factor of the amplification factor variable amplifier 31 based on the level of the band interference wave.

As described above, in the narrowband interference wave limiting device 30, the level of the narrowband interference wave can be detected by using the interference wave level detection circuit 34 even when the power of the spread signal is unknown. The level at which the narrow-band interference wave is limited can be set freely, and control such as limiting the narrow-band interference wave at a level at which no entanglement occurs becomes easy.

In the above description, the input power P
Although b and Pc are set between the input powers P1 and P2, the input power Pb may be set to the input power P1 and the input power Pc may be set to the input power P2.

FIG. 5 shows still another embodiment of the narrow band interference wave limiting device using the interference wave level detection circuit of the present invention. 5, the same or equivalent parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted.

In FIG. 5, a narrow-band interference wave limiting device 40
Denotes a signal distributor 41, a magnetostatic wave filter 42 as a second frequency-selective level limiting circuit, a signal distributor 43, and a third power detector between the variable amplification factor amplifier 4 and the signal distributor 21. A power detector 44, a power detector 45 as a fourth power detector, and an amplifier 46 are provided. Specifically, first, a signal distributor 41 is connected to the output of the variable gain amplifier 4, one output of which is connected to a magnetostatic wave filter 42, and the other output is connected to a power detector 44.
Further, a signal distributor 43 is connected to the output of the magnetostatic wave filter 42, one of the outputs is connected to the amplifier 46, and the other output is connected to the power detector 45. The output of the amplifier 46 is connected to the signal distributor 21. The outputs of the power detector 44 and the power detector 45 are output to the interference wave level calculation circuit 28 together with the power detector 24 and the power detector 25.
It is connected to the. Here, the signal distributor 21, the magnetostatic wave filter 22, the signal distributor 23, the power detector 24, the power detector 25, the interference wave level calculation circuit 28, and the signal distributor 4
1. The magnetostatic wave filter 42, the signal distributor 43, the power detector 44, the power detector 45, and the amplifier 46 constitute an interference wave level detection circuit 47.

In the interference wave level detecting circuit 47 of the narrow-band interference wave limiting device 40 thus configured, the signal distributor 41, the magnetostatic wave filter 42, the signal distributor 43, the power detector 44, and the power detector 45 The function is the signal distributor 21,
Magnetostatic wave filter 22, signal distributor 23, power detector 2
4. Since the function is exactly the same as that of the power detector 25,
2 corresponds to two circuits having the same function as the interference wave level detection circuit 29 (tentatively called an interference wave level detection unit) connected in series.

Next, the operation of the interference wave level detection circuit 47 will be described. First, by comparing whether or not there is a difference between the output of the power detector 44 and the output of the power detector 45 in the interference wave level detection unit at the preceding stage, the narrow band interference in the signal input by the magnetostatic wave filter 42 is determined. You can see if the waves are level-limited. When the level of the narrow-band interference wave is limited by the magnetostatic wave filter 42, the level of the input narrow-band interference wave is known in the magnetostatic wave filter 22 of the subsequent-stage interference wave level detection unit. Therefore, the level limiting amount of the narrow band interference wave in the magnetostatic wave filter 22 is also known, and the suppression ratio a of the narrow band interference wave is known. By knowing the suppression ratio of the narrow-band interference wave, the power of the spread signal input to the magnetostatic wave filter 22 can be obtained from Expression (6). When the power of the spread signal input to the magnetostatic wave filter 22 is known, the power of the spread signal input to the magnetostatic wave filter 42 of the subsequent interference wave level detection unit is calculated by calculating the loss and gain in the middle. be able to. Based on the power of the spread signal and the outputs of the power detectors 44 and 45 in the preceding interference wave level detector, the narrow band interference wave of the signal input to the magnetostatic wave filter 42 is obtained from the equations (5) and (6). , That is, the level of the narrow-band interference wave. The above calculation is performed by the interference wave level calculation circuit 28.

The output of the interference wave level calculation circuit 28 is connected to an amplification factor control terminal 4a of the amplification factor variable amplifier 4, and controls the amplification factor of the amplification factor variable amplifier 4 based on the calculated level of the narrow band interference wave. Thus, the level limiting amount of the narrow band interference wave in the magnetostatic wave filters 42 and 22 can be controlled.

As described above, in the narrowband interference wave limiting device 40, the level of the narrowband interference wave can be detected by using the interference wave level detection circuit 47 even when the power of the spread signal is unknown. The level at which the narrow-band interference wave is limited can be set freely, which facilitates control such as limiting the narrow-band interference wave at a level at which no entrainment occurs.

FIG. 6 shows an embodiment of the communication apparatus of the present invention. A communication device 50 shown in FIG. 6 represents a receiving unit of a spread spectrum communication device, and includes an antenna 51, a band-pass filter 52, an amplifier 53, and the narrow-band interference wave limiting device of the present invention shown in FIG. 20, a despreader 54, a demodulator 55, and a signal processing circuit 56. Here, the antenna 51 includes a band-pass filter 52 and an amplifier 53.
Are sequentially connected to the narrow band interference wave limiting device 20, and the narrow band interference wave limiting device 20 is connected to the signal processing circuit 56 via the despreader 54 and the demodulator 55 in order.

In the communication device 50 configured as described above, the spread signal received by the antenna 51 is subjected to removal of a signal of an unnecessary frequency by the band-pass filter 52, amplified by the amplifier 53, and transmitted to the narrow-band interference wave limiting device. 20. In the narrow-band interference wave limiting device 20, the narrow-band interference wave mixed into the occupied band of the spread signal is limited to the level of the spread signal. The signal in which the narrow-band interference wave is limited is despread by the despreader 54, demodulated by the demodulator 55, subjected to signal processing by the signal processing circuit 56, and output as, for example, an audio signal. The communication device 50 is omitted because it is not the main part of the invention, but in practice, the frequency conversion is often performed by connecting a mixer and a local oscillator to appropriate positions as needed.

As described above, by configuring the communication device 50 using the narrow band interference wave limiting device 20 of the present invention, the narrow band interference wave mixed into the occupied band of the spread signal is limited, and the communication device 50 Communication quality can be prevented from deteriorating.

The communication device using the narrow-band interference wave limiting device of the present invention is not limited to a spread spectrum communication device. The present invention may be applied to an S / N enhancer that lowers the level of noise by inverting the phase of the remaining noise whose level has been limited by the limiting device and adding the inverted signal to the original signal.

[0059]

According to the interference wave level detecting circuit of the present invention, a magnetostatic wave filter which is a frequency-selective level limiting circuit, first and second power detectors connected to its input and output, An interference wave level calculation circuit connected to the first and second power detectors for obtaining the level of the narrowband interference wave included in the signal input to the frequency selective type level limiting circuit. When the power is known, it is possible to detect the level of the narrow-band interference wave mixed into the occupied frequency band.

Further, a variable gain amplifier having a gain control terminal for changing the power of a signal input to the frequency selective type level limiting circuit, and a sweep control of the gain from a low gain to a high gain. Equipped with an amplification rate sweep circuit, the interference wave level calculation circuit and the amplification rate sweep circuit can be switched and connected to the amplification rate control terminal of the variable amplification rate amplifier, so that the power of the spread signal is unknown. Also,
The level of the narrow-band interference wave mixed into the occupied frequency band can be detected.

Further, even if the power of the spread signal is unknown, the narrow band interference mixed in the occupied frequency band can be achieved by connecting the above-mentioned interference wave level detection circuit in two stages in series. The level of the wave can be detected.

Further, according to the narrow-band interference wave limiting device of the present invention, by using the interference wave level detecting circuit of the present invention, the level for limiting the narrow-band interference wave can be set freely, and the interference Control such as limiting the narrow band interference wave at a level that does not occur becomes easy, and the narrow band interference wave can be effectively limited.

In the communication device of the present invention, the use of the narrow-band interference wave limiting device of the present invention can prevent the deterioration of communication quality.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of an interference wave level detection circuit of the present invention.

FIG. 2 is a diagram showing the frequency characteristics of a signal input to a magnetostatic wave filter and the frequency characteristics of a signal output from a magnetostatic wave filter in the interference wave level detection circuit of FIG. 1;

FIG. 3 is a block diagram showing another embodiment of the interference wave level detection circuit of the present invention.

FIG. 4 is a diagram illustrating a relationship between a power of a signal input to a magnetostatic wave filter and a difference (power difference) between input power and output power in the interference wave level detection circuit of FIG. 3;

FIG. 5 is a block diagram showing still another embodiment of the interference wave level detection circuit of the present invention.

FIG. 6 is a block diagram showing one embodiment of the communication device of the present invention.

FIG. 7 is a block diagram showing a conventional narrow-band interference wave limiting device.

8 is a block diagram showing a configuration of a level detection circuit of the narrow band interference wave limiting device of FIG.

9 is a diagram showing a positional relationship of a band of a band-pass filter of the level detection circuit of FIG. 8 with respect to a spread signal.

[Explanation of symbols]

 2 Input terminal 4, 31 Variable gain amplifier 4a, 31a Gain control terminal 7 Output terminal 20, 30, 40 Narrow band interference wave limiter 29, 34, 47 Interference wave level detection circuit 21, 23 , 41, 43 ... signal distributor 22, 42 ... magnetostatic wave filter 24, 25, 44, 45 ... power detector 26 ... power difference detector 27 ... level calculator 28 ... interference wave level calculator 32 ... switch 33 ... amplification Rate sweep circuit 46: Amplifier 50: Communication device

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Tetsu Nishimura 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Inside Murata Manufacturing Co., Ltd. (72) Inventor Hiroaki Tanaka 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Stock Company F-term in Murata Manufacturing (reference) 5K022 EE01 EE35 5K042 AA06 BA08 CA02 CA12 CA13 DA01 DA16 EA03 EA06 FA06 FA21 LA06 5K052 AA03 BB08 CC06 DD04 EE01 EE11 FF01 GG13 GG46

Claims (5)

[Claims] 1. A frequency selective type level limiting circuit, and a first power detector connected to an input side of the frequency selective type level limiting circuit and detecting a power of a signal input to the frequency selective type level limiting circuit. And connected to the output side of the frequency-selective level limiting circuit,
A second power detector for detecting the power of the signal output from the frequency-selective level limiting circuit; and a second power detector connected to the first and second power detectors and input to the frequency-selective level limiting circuit. An interference wave level calculating circuit for calculating a level of a narrow band interference wave included in the signal. 2. A variable gain amplifier having a gain control terminal for changing the power of a signal input to the frequency selective type level limiting circuit, and the gain of the variable gain amplifier is increased from a low gain to a high gain. An amplification factor sweep circuit that performs sweep control to an amplification factor, wherein the interference wave level calculation circuit and the amplification factor sweep circuit are switchably connected to the amplification factor control terminal of the amplification factor variable amplifier. The interference wave level detection circuit according to claim 1. 3. A second frequency selective level limiting circuit, which is connected to an input side of the second frequency selective level limiting circuit at a stage preceding the frequency selective type level limiting circuit, and A third power detector for detecting the power of a signal input to the level limiting circuit; and a third power detector connected to an output side of the second frequency selective type power limiting circuit. A fourth power detector for detecting the power of the output signal, wherein the third power detector and the fourth power detector are connected to the interference wave level calculation circuit. The interference wave level detection circuit according to claim 1, wherein 4. A narrow-band interference wave limiting device using the interference wave level detection circuit according to claim 1. 5. A communication device using the narrow-band interference wave limiting device according to claim 4.