Amplification device, radio device, and monitoring method

Abstract

To enable even a wireless device with a simple configuration without an advanced signal processing section to monitor the output signal of an amplifier built in the wireless device.SOLUTION: An amplification device according to this example includes a power amplifier 15 that amplifies an input signal to a predetermined level, a first detector 4 that detects the amplitude level on the input side of the power amplifier 15 on the basis of a signal obtained by branching a part of the input signal to the power amplifier 15, a second detector 8 that detects the amplitude level on the output side of the power amplifier 15 on the basis of a signal obtained by branching a part of the output signal from the power amplifier 15, and a gain detection mechanism (analog-to-digital converter 9, 10 and a signal processing unit (not shown)) that detects the gain of the power amplifier 15 by comparing the amplitude level detected by the first detector 4 and the amplitude level detected by the second detector 8.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an amplifier that amplifies an input signal to a predetermined level, and to a wireless device incorporating the amplifier. [Background technology]

[0002] In broadcasting services such as terrestrial television broadcasting, in areas far from the main broadcasting transmitting station (parent station) or in areas with obstacles such as mountains, the electromagnetic waves transmitted from the parent station cannot be received with sufficient strength, and the quality of the broadcasting service may deteriorate. To address this problem, relay transmitting stations (child stations) are installed near areas with poor reception, and signals are transmitted from the parent station to the child station using electromagnetic waves such as microwaves, and the child station transmits the broadcast signal to the target area. Furthermore, when it is difficult to transmit a signal directly from the parent station to the child station, the signal is also transmitted to the child station via another relay transmitting station.

[0003] Fig. 8A shows a block diagram of a receiving section for receiving a broadcast signal transmitted from a parent station at a child station. Fig. 8B shows a block diagram of a transmitting section for transmitting a signal to a child station. Note that the transmitting section in Fig. 8B can be used in two ways: transmitting a signal from a parent station to a child station, and transmitting a signal from a child station to another child station. In either case, a transmitting section with a similar configuration can be used.

[0004] In the slave station, a signal transmitted by electromagnetic waves such as the microwave band from the master station or another slave station is received by a receiving antenna 81, passes through a bandpass filter 82 and a low-noise amplifier 83, and is then frequency-converted to the IF (Intermediate Frequency) band by a frequency converter 84. The slave station converts this IF band signal to a broadcasting frequency band and transmits it as a broadcast signal to the target area. When retransmitting a signal to another slave station, the signal is converted to a transmission frequency such as the microwave band and retransmitted. A transmitting section for transmitting a signal to the slave station converts the IF band signal to a transmission frequency such as the microwave band by a frequency converter 87, amplifies the signal to a required signal level by a power amplifier 88, and transmits the signal from a transmitting antenna 89.

[0005] In order to provide broadcasting services while maintaining a certain quality throughout the target area, it is necessary to install relay transmitting stations in all areas where the signal quality deteriorates as described above. Therefore, it is desirable to reduce the installation cost of relay transmitting stations. For this reason, some relay transmitting stations used in terrestrial television broadcasting use modulated signals defined by broadcasting standards for IF signals, and only frequency convert and amplify the IF signals to transmit broadcast signals or retransmit them to other child stations. This configuration simplifies the device without using modulation, demodulation, or complex signal processing units.

[0006] 9 shows a block diagram of a repeater device used to extend the communication area in a wireless communication device such as a wireless LAN (Local Area Network). In the repeater device, a signal from a main base station (parent station) is received by a receiving antenna 81, passed through a band-pass filter 82 and a low-noise amplifier 83, and then frequency-converted to an IF band by a first frequency converter 84. This IF signal is further converted to a transmission frequency by a second frequency converter 87, amplified to a predetermined level by a power amplifier 88, and then transmitted from a transmitting antenna 89 to a predetermined area.

[0007] There are various configurations of repeater devices, but as with broadcast relay transmitting stations, when it is desired to expand the area while keeping installation costs down, a simple configuration that does not use modulation, demodulation, or other advanced signal processing, such as the configuration example in Figure 9, may be used. Also, in the above example, an example was described in which different frequencies are used for the signal from the parent station and the signal retransmitted from the repeater, but the same frequency may be used if interference between the two can be sufficiently reduced.

[0008] The above-mentioned broadcast relay transmitting station and communication repeater device do not require modulation, demodulation, or advanced signal processing, so the device can be simplified. This has the advantage of reducing costs when expanding the area. The configuration of the above-mentioned repeater device is disclosed in, for example, Patent Document 1.

[0009] Incidentally, in the transmitting section of the above-mentioned broadcast relay transmitting station, in order to transmit the required distance, it is necessary to amplify the signal to a specified level by the power amplifier 88. Similarly, in the communication repeater, in order to cover the desired area, it is necessary to amplify the signal by the power amplifier 88. At this time, in order to prevent interference with adjacent frequency channels, it is necessary to suppress signal distortion caused by the power amplifier.

[0010] In general, the more the saturation output level of the amplifying device used in the power amplifier is sufficiently higher than the output signal level of the signal being handled, the lower the distortion caused by the power amplifier. On the other hand, the higher the saturation output level of the amplifying device is relative to the output signal level, the worse its power efficiency becomes. Therefore, in order to reduce the power consumption of the device, it is desirable to use an amplifying device with a saturation output level as small as possible within the range in which distortion of the output signal is acceptable.

[0011] However, when the above-mentioned design is performed, since there is little margin for the distortion of the output signal with respect to the allowable value, various influences such as slight damage to the device and environmental changes may cause the distortion of the output signal to exceed the allowable range. On the other hand, since the distortion of the output signal causes interference with adjacent frequency channels, the allowable value is strictly defined by standards. Therefore, if the distortion of the output signal worsens, it is necessary to detect it before it exceeds the allowable value and perform maintenance. For this reason, it is desirable for these devices to have a function of analyzing the output signal and issuing an alarm when the distortion of the output signal of the power amplifier exceeds a predetermined value.

[0012] In order to realize such a function, a method is often used in which the output signal is sampled, and then analyzed in a signal processing unit to calculate a frequency spectrum, thereby detecting the signal level leaking to an adjacent frequency channel. According to this method, the signal level leaking to an adjacent frequency channel is directly detected, so that highly accurate detection is possible. However, in relay transmitting stations and repeater devices having a simple configuration as described above, there are many cases where a signal processing unit for performing advanced signal processing is not built in. In the case of such devices, since it is difficult to perform an analysis such as calculating the frequency spectrum of the output signal, there is a problem that it is difficult to have a function for monitoring the signal level leaking to an adjacent channel. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] JP 2004-260371 A Summary of the Invention [Problem to be solved by the invention]

[0014] As mentioned above, some broadcast relay transmitting stations and communication repeater devices that aim to reduce costs with a simple configuration do not have a built-in signal processing unit for performing advanced signal processing. In such devices, there is a problem that it is difficult to perform advanced signal processing to detect failures or malfunctions and issue an alarm as necessary. On the other hand, when trying to reduce the power consumption of the device while maintaining the required communication distance, it is desirable to use an amplifying device with a saturation output level as small as possible within the range in which the distortion of the output signal is allowed in the power amplifier used in the transmission unit, but since the margin of the distortion of the output signal relative to the allowable value is small, there is a certain possibility that the distortion of the output signal will exceed the allowable value due to various factors such as failures and environmental changes. Therefore, measures such as monitoring the output signal and issuing an alarm when the distortion of the output signal exceeds a predetermined level have been desired.

[0015] However, as mentioned above, some broadcast relay transmitting stations and communication repeater devices with simple configurations do not have a built-in signal processing unit that performs advanced signal processing. For this reason, there is a problem that it is difficult to perform processing such as detecting the signal level leaking to adjacent frequency channels by sampling the output signal and then analyzing it with signal processing to calculate the frequency spectrum.

[0016] The present invention has been made in consideration of the above-described conventional circumstances, and has an object to make it possible to monitor the output signal of an amplifier built into a wireless device, even if the wireless device has a simple configuration and does not have an advanced signal processing unit. [Means for solving the problem]

[0017] In order to achieve the above object, an amplifying device according to one aspect of the present invention is configured as follows: That is, the amplifying device according to the present invention is characterized by comprising an amplifier that amplifies an input signal to a predetermined level, a first detector that detects an amplitude level on the input side of the amplifier based on a signal that is a part of the signal that is input to the amplifier, a second detector that detects an amplitude level on the output side of the amplifier based on a signal that is a part of the signal that is output from the amplifier, and a gain detection mechanism that detects the gain of the amplifier by comparing the amplitude level detected by the first detector with the amplitude level detected by the second detector.

[0018] Here, the amplification device of the present invention can be configured to further include a gain control unit that controls the gain of a signal branched off from a portion of the signal input to the amplifier in accordance with the difference between the amplitude level detected by the first detector and the amplitude level detected by the second detector, a subtractor that calculates the difference between a signal branched off from a portion of the signal output from the amplifier and a signal whose gain has been controlled by the gain control unit, a third detector that detects the output level of the subtractor, and a passing phase detection mechanism that detects the passing phase of the amplifier based on the output level detected by the third detector and the gain detected by the gain detection mechanism.

[0019] Furthermore, the amplifying device according to the present invention may further include a distortion generating circuit disposed in front of the amplifier, and the distortion generating circuit may be configured to include an element having distortion characteristics inverse to those of the distortion generated by the amplifier.

[0020] Furthermore, in the amplification device of the present invention, the distortion generating circuit can be configured to include a pre-gain control section that controls the gain of a signal input to the amplifier, a pre-phase control means that controls the phase of the signal input to the amplifier, a gain control signal generation section that generates a control signal to have the inverse characteristics of the amplitude distortion generated in the amplifier based on the amplitude level detected by the first detector and provides the control signal to the pre-gain control section, and a phase control signal generation section that generates a control signal to have the inverse characteristics of the phase distortion generated in the amplifier based on the amplitude level detected by the first detector and provides the control signal to the pre-phase control section.

[0021] A wireless device according to another aspect of the present invention is configured as follows. That is, the antenna includes an amplifier which receives a signal to be transmitted wirelessly and amplifies the input signal to a predetermined level; an antenna which transmits the signal amplified by the amplifier; a first detector which detects an amplitude level at the input side of the amplifier based on a signal obtained by branching off a portion of the signal input to the amplifier; a second detector which detects an amplitude level at the output side of the amplifier based on a signal obtained by branching off a portion of the signal output from the amplifier; a gain detection mechanism which detects the gain of the amplifier by comparing the amplitude level detected by the first detector with the amplitude level detected by the second detector; a gain control section which controls the gain of the signal obtained by branching off a portion of the signal input to the amplifier in accordance with the difference between the amplitude level detected by the first detector and the amplitude level detected by the second detector; a subtractor which calculates the difference between the signal obtained by branching off a portion of the signal output from the amplifier and a signal whose gain is controlled by the gain control section; a third detector which detects the output level of the subtractor; and a pass phase detection mechanism which detects the pass phase of the amplifier based on the output level detected by the third detector and the gain detected by the gain detection mechanism.

[0022] A monitoring method according to yet another embodiment of the present invention is configured as follows: That is, the monitoring method for monitoring an amplifier that amplifies an input signal to a predetermined level includes a first detection step of detecting an amplitude level on the input side of the amplifier based on a signal obtained by branching off a part of the signal input to the amplifier, a second detection step of detecting an amplitude level on the output side of the amplifier based on a signal obtained by branching off a part of the signal output from the amplifier, a gain detection step of detecting a gain of the amplifier by comparing the amplitude level detected in the first detection step with the amplitude level detected in the second detection step, a gain control step of controlling a gain of the signal obtained by branching off a part of the signal input to the amplifier in accordance with a difference between the amplitude level detected in the first detection step and the amplitude level detected in the second detection step, a subtraction step of calculating a difference between the signal obtained by branching off a part of the signal output from the amplifier and a signal whose gain has been controlled in the gain control step, a third detection step of detecting an output level in the subtraction step, and a passing phase detection step of detecting a passing phase of the amplifier based on the output level detected in the third detection step and the gain detected in the gain detection step.

[0023] A monitoring method according to yet another aspect of the present invention is configured as follows: That is, in a monitoring method for monitoring a wireless device having an amplifier to which a signal to be wirelessly transmitted is input and which amplifies the input signal to a predetermined level, and an antenna to transmit the signal amplified by the amplifier, the monitoring method includes a first detection step of detecting an amplitude level on the input side of the amplifier based on a signal obtained by branching off a part of the signal input to the amplifier, a second detection step of detecting an amplitude level on the output side of the amplifier based on a signal obtained by branching off a part of the signal output from the amplifier, and comparing the amplitude level detected in the first detection step with the amplitude level detected in the second detection step to determine the utilization of the amplifier. the amplifier input signal is input to the amplifier through a first detection step; a gain control step for controlling the gain of a signal obtained by branching off a portion of the signal input to the amplifier in accordance with the difference between the amplitude level detected in the first detection step and the amplitude level detected in the second detection step; a subtraction step for calculating the difference between the signal obtained by branching off a portion of the signal output from the amplifier and the signal whose gain has been controlled in the gain control step; a third detection step for detecting the output level of the subtraction step; and a passing phase detection step for detecting the passing phase of the amplifier based on the output level detected in the third detection step and the gain detected in the gain detection step. Effect of the Invention

[0024] According to the present invention, even a wireless device having a simple configuration without an advanced signal processing section can monitor the output signal of an amplifier built into the wireless device. [Brief description of the drawings]

[0025] [Figure 1] 1 is a block diagram showing an example of the configuration of an amplifier device according to a first embodiment of the present invention. [Diagram 2] FIG. 11 is a block diagram showing an example of the configuration of an amplifier device according to a second embodiment of the present invention. [Figure 3A] FIG. 1 is a diagram showing an image of the occurrence probability of the amplitude of an OFDM signal. [Figure 3B] FIG. 13 is a diagram illustrating an example of a threshold value for a gain deviation. [Figure 3C]FIG. 13 is a diagram illustrating an example of a threshold value related to a deviation of a passing phase. [Figure 4] FIG. 11 is a block diagram showing an example of the configuration of an amplifier device according to a third embodiment of the present invention. [Figure 5A] FIG. 2 is a diagram showing an example of input signal level vs. gain characteristics in an amplifier. [Figure 5B] FIG. 1 is a diagram showing an example of input signal level vs. passing phase characteristics in an amplifier. [Figure 6A] FIG. 13 is a diagram showing an example of control voltage vs. gain characteristics in a second gain control section. [Figure 6B] 13 is a diagram illustrating an example of input / output characteristics of a second control voltage generating unit. FIG. [Figure 7A] 11 is a diagram showing an example of a control voltage vs. phase shift amount characteristic in a phase control section. FIG. [Figure 7B] 13 is a diagram illustrating an example of input / output characteristics of a third control voltage generating unit. FIG. [Figure 8A] FIG. 1 is a block diagram showing an example of the configuration of a receiving section of a simple wireless device. [Figure 8B] FIG. 1 is a block diagram showing an example of the configuration of a transmission section of a simple wireless device. [Figure 9] FIG. 1 is a block diagram showing an example of the configuration of a simple repeater device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The present invention will now be described with reference to the drawings, using several embodiments.

[0027] (First embodiment) FIG. 1 shows an example of the configuration of an amplifier device according to a first embodiment of the present invention. The amplifier device (amplifier circuit) of this example has a built-in power amplifier that amplifies a signal to a predetermined level, and has a function of monitoring the output signal of the power amplifier. The amplifier device of this example is built into, for example, a wireless device such as a relay transmitting station or a repeater device that has a simple configuration without an advanced signal processing unit. As an example, it is installed in place of the power amplifier 88 in the wireless device shown in FIG. 8B or FIG. 9.

[0028] In this example, instead of monitoring the signal spectrum of the output signal, the output signal of power amplifier 15, which amplifies the signal to be wirelessly transmitted to a predetermined level, is monitored to detect the gain deviation and passing phase deviation of power amplifier 15 relative to the input signal level. In normal power amplifier operation, when these deviations are small, the distortion of the output signal is small, and conversely, when the deviations increase, the distortion increases. Therefore, by monitoring that these deviations are within predetermined values, it is possible to equivalently monitor that the distortion of the output signal is within the allowable value.

[0029] The operation of the amplifying device of this embodiment will be described below. The amplifying device of this embodiment first detects the signal level between the input and output of the power amplifier 15 to obtain the gain deviation. The input signal to the power amplifier 15 is detected using the first directional coupler 1, the second directional coupler 2, the first amplitude adjustment unit 3, and the first detector 4. A part of the input signal is input to the first amplitude adjustment unit 3 via the first directional coupler 1 and the second directional coupler 2. The first amplitude adjustment unit 3 is composed of an amplifier, an attenuator, etc., and provides a fixed gain or attenuation so that the signal level becomes a predetermined level. The input signal whose amplitude has been adjusted by the first amplitude adjustment unit 3 is input to the first detector 4. The first detector 4 detects the envelope level of the input signal, i.e., the amplitude level of the input signal.

[0030] Similarly, the output signal from power amplifier 15 is detected using third directional coupler 5, fourth directional coupler 6, second amplitude adjustment unit 7, and second detector 8. That is, a part of the output signal is input to second amplitude adjustment unit 7 via third directional coupler 5 and fourth directional coupler 6, and after the signal level is adjusted by second amplitude adjustment unit 7 applying a fixed gain or attenuation amount, the amplitude level of the output signal is detected by second detector 8.

[0031] The output of the first detector 4 is then converted into a digital signal by the first analog-digital converter 9, and the output of the second detector 8 is converted into a digital signal by the second analog-digital converter 10, after which the signal levels of both are compared in a signal processing unit (not shown) to detect the gain in the input and output. As described above, when the distortion of the output signal is small, the gain calculated as described above has a small deviation from the input signal level. Therefore, the deviation of the gain detected from the input signal level is compared with a predetermined threshold, and an alarm is issued if the gain deviation exceeds the threshold.

[0032] In this example, a signal processor is required to detect the input and output gain, but the signal processing performed here is a simple process of simply comparing the output levels of the detectors, and can therefore be realized with a relatively inexpensive and simple signal processor.

[0033] As described above, the input / output gain characteristics can be easily monitored by providing detectors (4, 8) on the input and output sides of the power amplifier 15 and comparing the output levels of the detectors. However, since a normal detector only detects the amplitude of the input and output signals, it is difficult to monitor the phase. Therefore, a mechanism for detecting the phase is also added to the amplifier of this embodiment.

[0034] The operation for detecting the phase will be described below. A part of the input signal is branched by the first directional coupler 1 and the second directional coupler 2, while the other signal branched by the second directional coupler 2 is input to the first gain control section 12 via the first delay circuit 11. On the other hand, the output of the first detector 4 and the output of the second detector 8 are also input to the first subtractor 13, and a signal corresponding to the difference between the two is output from the first subtractor 13. The first control voltage generating section 14 generates a control voltage for the first gain control section 12 based on the signal corresponding to this difference. The first gain control section 12 operates to add a gain equal to the difference to the input signal based on the control voltage provided by the first control voltage generating section 14. The first gain control section 12 can be easily configured with a variable gain amplifier, a variable gain device, or the like.

[0035] Here, the input signal is Si and the output signal is So, and they are expressed by the following equations (1) and (2).

number

[0036]

number

[0037] In the above formula, A is the input signal amplitude, θ is the phase of the input signal, G is the gain, Ge is the gain deviation, φ is the passing phase, and φe is the passing phase deviation. Note that the gain deviation Ge and the passing phase deviation φe occur mainly in the power amplifier 15 and change depending on the signal level.

[0038] The first control voltage generating unit 14 generates a control voltage for the first gain control unit 12 so that a gain equal to the difference between the input and output amplitudes is added. Therefore, the first gain control unit 12 controls the gain so that the amplitude of the input signal shown in equation (1) becomes equal to the amplitude of the output signal shown in equation (2). Therefore, the output of the first gain control unit 12 becomes as shown in the following equation (3).

[0039]

number

[0040] The output of the first gain control section 12 is input to a second subtractor 16. A part of the output signal of the power amplifier 15 is branched by the third directional coupler 5 and the fourth directional coupler 6, and is further provided to the other input of the second subtractor 16 via a third amplitude adjustment section 19. The difference component between the two calculated by the second subtractor 16 is then input to a third detector 17.

[0041] Here, if the input signal to the third detector 17 is Si(DET), then the following equation (4) is obtained.

number

[0042] Since the third detector 17 detects the amplitude component of this signal, the output of the third detector 17 is given by the following equation (5).

number

[0043] In the above formula, (G+Ge)A represents the output amplitude, which has already been calculated from the output signals of the first detector 4 and the second detector 8. Therefore, after this is converted to a digital signal by the third analog-to-digital converter 18, the passing phase component φ+φe of the power amplifier 15 can be calculated by subtracting (G+Ge)A from the magnitude of that signal in a signal processing unit (not shown).

[0044] As with the amplitude, when the distortion of the power amplifier 15 is sufficiently small, the deviation of its passing phase from the input signal level is small. Therefore, the deviation of the detected passing phase from the input signal level is monitored, and an alarm is issued if it exceeds a predefined threshold. Although a signal processing unit is also required for phase detection, the signal processing performed here is also very simple. Therefore, it can be realized with an inexpensive and simple signal processing unit.

[0045] According to this embodiment, in addition to calculating the gain from the input and output signal levels detected by the detectors 4 and 8, the gain control unit 12, the control voltage generating unit 14, the subtractor 16, the detector 17, and the like calculate the phase, thereby making it possible to detect the input and output gain and phase with a simple configuration. Moreover, by monitoring the deviation between the input and output gain and phase, it becomes possible to equivalently monitor the distortion of the output signal. Moreover, since these calculations can be performed with only simple signal processing, it becomes possible to monitor the output signal without using an expensive signal processing unit. Furthermore, by applying the amplifier device of this embodiment to a wireless device that is designed to reduce costs with a simple configuration, it becomes possible to monitor the output signal while suppressing increases in cost.

[0046] As described above, the amplifying device of this embodiment includes the power amplifier 15 that amplifies the input signal to a predetermined level, the first detector 4 that detects the amplitude level of the input side of the power amplifier 15 based on a signal obtained by branching off a part of the input signal to the power amplifier 15, the second detector 8 that detects the amplitude level of the output side of the power amplifier 15 based on a signal obtained by branching off a part of the output signal from the power amplifier 15, and a gain detection mechanism (analog-digital converters 9, 10 and a signal processing unit not shown) that detects the gain of the power amplifier 15 by comparing the amplitude level detected by the first detector 4 with the amplitude level detected by the second detector 8. Therefore, even a wireless device with a simple configuration that does not have an advanced signal processing unit can monitor the gain of the power amplifier by installing the amplifying device of this embodiment. This makes it possible to provide the wireless device with a function such as issuing an alarm when the deviation of the gain of the power amplifier relative to the input signal exceeds a threshold value.

[0047] The amplifier of this embodiment further includes a gain control section 12 that controls the gain of a signal obtained by splitting a part of an input signal to the power amplifier 15 in accordance with the difference between the amplitude level detected by the first detector 4 and the amplitude level detected by the second detector 8, a subtractor 16 that calculates the difference between a signal obtained by splitting a part of an output signal from the power amplifier 15 and a signal whose gain is controlled by the gain control section 12, a third detector 17 that detects the output level of the subtractor 16, and a passing phase detection mechanism (analog-digital converter 18 and a signal processing section not shown) that detects the passing phase of the power amplifier 15 based on the output level detected by the third detector 17 and the gain detected by the gain detection mechanism. Therefore, even a wireless device with a simple configuration that does not have an advanced signal processing section can monitor the passing phase of the power amplifier by mounting the amplifier of this embodiment. This makes it possible to provide the wireless device with a function such as issuing an alarm when the deviation of the passing phase of the power amplifier relative to the input signal exceeds a threshold value.

[0048] (Second Example) 2 shows an example of the configuration of an amplifier according to a second embodiment of the present invention. The amplifier according to this embodiment has a configuration in which a predistorter 21 is added to the amplifier according to the first embodiment.

[0049] As mentioned above, in a general power amplifier device, the distortion becomes smaller when the saturation output level is sufficiently larger than the output signal level of the signal being handled. On the other hand, the efficiency becomes worse as the saturation output level of the amplifier device becomes larger than the output signal level. Therefore, in order to reduce the power consumption of the device, it is desirable to use an amplifier device with a saturation output level as small as possible within the range in which the distortion of the output signal is allowed, but this increases the distortion generated by the amplifier device. Therefore, in the second embodiment, a predistorter 21 is inserted in the front stage of the power amplifier 15.

[0050] The predistorter 21 reduces distortion by generating distortion that is inverse to the distortion characteristics generated by the power amplifier 15. For example, a diode having characteristics similar to the inverse distortion characteristics of the power amplifier 15 can be used as the predistorter 21. As another example, a method is available in which a device capable of controlling gain, such as a variable gain amplifier or a variable attenuator, and a device capable of controlling phase, such as a phase shifter, are used and controlled to reproduce characteristics similar to the inverse distortion characteristics of the power amplifier 15.

[0051] In general devices, it is desirable to detect failures or malfunctions and issue an alarm as necessary. In particular, in wireless devices using a predistorter, there is a possibility that the predistorter will not function properly due to the influence of a slight failure, and the distortion of the power amplifier will not be sufficiently suppressed. For this reason, it is desirable to provide a function that issues an alarm when the distortion of the output signal exceeds a predetermined level. Therefore, the amplifier according to the second embodiment also monitors the output signal in the same manner as the first embodiment.

[0052] Figure 3A shows an image of the occurrence probability of the amplitude of an OFDM (Orthogonal Frequency-Division Multiplexing) signal. As shown in the figure, the occurrence probability of the amplitude in an OFDM signal is generally maximum near the amplitude equivalent to the average power, and tends to decrease at amplitudes higher than that. Therefore, the deviation of gain and passing phase is also greatly affected by deviations near the average.

[0053] Therefore, for example, thresholds such as those shown by solid lines in Figures 3B and 3C are set, and an alarm is issued when the magnitude of the deviation exceeds the threshold. Figure 3B shows an example of a threshold related to gain deviation, which increases stepwise as the amplitude level increases. Figure 3C shows an example of a threshold related to pass phase deviation, which increases stepwise as the amplitude level increases. The thresholds to be actually applied can be determined in advance by acquiring statistical data on the relationship between the deviation of gain or pass phase and distortion.

[0054] As described above, the amplifier device of this embodiment is provided with a predistorter 21, which is configured as a distortion generating circuit in front of the power amplifier 15 and is made up of elements having a distortion characteristic opposite to that generated by the power amplifier 15. Therefore, according to the amplifier device of this embodiment, even in a wireless device such as a relay transmitting station or a repeater device having a simple configuration without an advanced signal processing unit, it is possible to reduce power consumption by using a predistorter and to monitor whether the distortion of the output signal is within a tolerable range.

[0055] (Third Example) 4 shows an example of the configuration of an amplifier according to a third embodiment of the present invention. The amplifier of this embodiment is configured such that a distortion generating circuit consisting of a second gain control section 41, a phase control section 42, a second control voltage generating section 43, a third control voltage generating section 44, and a second delay circuit 45 is provided in the front stage of a power amplifier 15 as the predistorter 21 in the second embodiment.

[0056] An input signal is input to a second gain control section 41 and a phase control section 42 via a first directional coupler 1 and a second delay circuit 45. The second gain control section 41 controls the gain of the input signal so that it has an inverse characteristic to the amplitude distortion of the power amplifier 15. Similarly, the phase control section 42 controls the phase of the input signal so that it has an inverse characteristic to the phase distortion of the power amplifier 15. In this way, an input signal having an inverse distortion characteristic to the distortion generated in the power amplifier 15 is generated, and the distortion is suppressed.

[0057] The other output of the first directional coupling 1 is input to the first detector 4 via the second directional coupler 2 and the first amplitude adjustment unit 3, as described in the first embodiment. The first detector 4 detects an envelope level, which is input to the second control voltage generation unit 43 and the third control voltage generation unit 44. The second control voltage generation unit 43 generates a control voltage to provide a desired gain or attenuation amount according to the envelope level input from the first detector 4, and inputs it to the control voltage input terminal of the second gain control unit 41. Similarly, the third control voltage generation unit 44 generates a control voltage to provide a desired phase shift amount according to the envelope level input from the first detector 4, and inputs it to the control voltage input terminal of the phase control unit 42.

[0058] In many cases, a delay occurs between the time it takes for the input signal to reach the first gain control section 45 and the phase control section 42 and the time it takes for the second control voltage generation section 43 and the third control voltage generation section 44 to generate a control voltage. Therefore, the second delay circuit 45 adjusts the timing of both.

[0059] In the second control voltage generating section 43, it is necessary to generate a control voltage so that the gain or attenuation of the second gain control section 41 becomes a desired value according to the envelope level. Similarly, the third control voltage generating section 44 needs to generate a control voltage so that the phase control section 42 becomes a desired phase shift amount. Therefore, it is only necessary to measure the input signal level vs. gain characteristic and the input signal level vs. phase characteristic of the power amplifier 15 in advance, and to design the second control voltage generating section 43 and the third control voltage generating section 44 based on these characteristics so as to convert the envelope level input from the first detector 4 to a desired control voltage.

[0060] Fig. 5A shows an example of the gain (Gain) characteristic versus the input signal level (Pin) in a power amplifier. Also, Fig. 5B shows the input signal level (Pin) versus the passing phase (Phase) characteristic in a power amplifier. In an ideal power amplifier, the gain and passing phase are constant, but in an actual power amplifier, they are not constant and distortion occurs in the output signal.

[0061] Therefore, in the second gain control section 41, when the characteristic of the gain (Gain) with respect to the control voltage (Vc) is as shown in Fig. 6A, the second control voltage generation section 43 is designed to have the input / output characteristic as shown in Fig. 6B. Similarly, in the phase control section 42, when the phase shift amount (Phase) with respect to the control voltage (Vc) is as shown in Fig. 7A, the third control voltage generation section 44 is designed to have the input / output characteristic as shown in Fig. 7B.

[0062] In addition, even in the amplifier of this example, if the predistorter function does not operate normally due to the influence of a failure or the like, there is a possibility that the distortion of the power amplifier cannot be sufficiently suppressed. For this reason, it is desirable to provide a function such as issuing an alarm when the distortion of the output signal exceeds a predetermined level. Therefore, in the amplifier of the third embodiment, the output signal is monitored in the same manner as in the first embodiment.

[0063] As described above, the amplifier of this embodiment has a distortion generating circuit disposed in front of the power amplifier 15, and this distortion generating circuit includes a second gain control section 41 for controlling the gain of the signal input to the power amplifier 15, a phase control section 42 for controlling the phase of the signal input to the power amplifier 15, a second control signal generating section 43 for generating a control signal to have an inverse characteristic to the amplitude distortion generated in the power amplifier 15 based on the amplitude level detected by the first detector 4 and providing the control signal to the second gain control section 41, and a control signal generating section 44 for generating a control signal to have an inverse characteristic to the phase distortion generated in the power amplifier 15 based on the amplitude level detected by the first detector 4 and providing the control signal to the phase control section 42. Therefore, according to the amplifier of this embodiment, it is possible to suppress the distortion of the power amplifier more effectively without performing complicated signal processing. As a result, it is possible to obtain a desired output power while reducing power consumption even in the transmission section of a wireless device such as a relay transmission station or a repeater, which is simple in configuration and low in cost. Furthermore, it is also possible to monitor whether the distortion of the output signal is within an allowable range.

[0064] Although the embodiments of the present invention have been described above, the above embodiments are merely illustrative and do not limit the technical scope of the present invention. The present invention can take various other embodiments, and various modifications such as omissions and substitutions can be made without departing from the gist of the present invention. These embodiments and modifications are included in the scope and gist of the invention described in this specification, etc., and are included in the scope of the invention described in the claims and their equivalents.

[0065] Furthermore, the present invention can be provided not only as devices such as those described above or as a system composed of these devices, but also as methods executed by these devices, programs for causing a processor to realize the functions of these devices, and storage media for storing such programs in a computer-readable format. [Industrial Applicability]

[0066] The present invention can be used in an amplifier that amplifies an input signal to a predetermined level, and in a wireless device incorporating the amplifier. [Explanation of symbols]

[0067] 1,2,5,6: directional couplers; 3,7,19: amplitude adjustment section; 4,8,17: detector; 9,10,18: analog-to-digital converter; 11,45: delay circuit; 12,41: gain control section; 13,16: subtractor; 14,43,44: control voltage generation section; 15,88...power amplifier; 21: predistorter; 42: phase control section; 81: receiving antenna; 82: band-pass filter; 83: low-noise amplifier; 84,87: frequency converter; 89: transmitting antenna

Claims

1. an amplifier that amplifies an input signal to a predetermined level; a first detector that detects an amplitude level of an input side of the amplifier based on a signal that is a part of a signal that is branched off from the input signal to the amplifier; a second detector that detects an amplitude level of the output of the amplifier based on a signal that is a part of the signal output from the amplifier; a gain detection mechanism that detects the gain of the amplifier by comparing an amplitude level detected by the first detector with an amplitude level detected by the second detector; a gain control unit that controls a gain of a signal obtained by branching off a part of a signal input to the amplifier in accordance with a difference between an amplitude level detected by the first detector and an amplitude level detected by the second detector; a subtractor that calculates a difference between a signal obtained by branching off a portion of the signal output from the amplifier and a signal whose gain is controlled by the gain control unit; a third detector for detecting an output level of the subtractor; and a passing phase detection mechanism that detects a passing phase of the amplifier based on an output level detected by the third detector and a gain detected by the gain detection mechanism.

2. 2. The amplifier according to claim 1, Further comprising a distortion generating circuit arranged in front of the amplifier, An amplifying device, wherein the distortion generating circuit includes an element having a distortion characteristic opposite to that generated by the amplifier.

3. 3. The amplifier according to claim 2, The distortion generating circuit includes: a pre-gain control unit for controlling a gain of a signal input to the amplifier; a pre-phase control section for controlling a phase of a signal input to the amplifier; a gain control signal generating unit that generates a control signal based on the amplitude level detected by the first detector so as to have an inverse characteristic to the amplitude distortion generated in the amplifier, and provides the control signal to the pre-gain control unit; and a phase control signal generating unit that generates a control signal to the pre-phase control unit so as to have an inverse characteristic to the phase distortion generated in the amplifier based on the amplitude level detected by the first detector.

4. an amplifier that receives a signal to be wirelessly transmitted and amplifies the input signal to a predetermined level; an antenna for transmitting the signal amplified by the amplifier; a first detector that detects an amplitude level of an input side of the amplifier based on a signal that is a part of a signal that is branched off from the input signal to the amplifier; a second detector that detects an amplitude level of the output of the amplifier based on a signal that is a part of the signal output from the amplifier; a gain detection mechanism that detects the gain of the amplifier by comparing an amplitude level detected by the first detector with an amplitude level detected by the second detector; a gain control unit that controls a gain of a signal obtained by branching off a part of a signal input to the amplifier in accordance with a difference between an amplitude level detected by the first detector and an amplitude level detected by the second detector; a subtractor that calculates a difference between a signal obtained by branching off a portion of the signal output from the amplifier and a signal whose gain is controlled by the gain control unit; a third detector for detecting an output level of the subtractor; a passing phase detection mechanism that detects a passing phase of the amplifier based on an output level detected by the third detector and a gain detected by the gain detection mechanism.

5. A monitoring method for monitoring an amplifier that amplifies an input signal to a predetermined level, comprising: a first detection step of detecting an amplitude level of an input side of the amplifier based on a signal obtained by splitting a part of a signal input to the amplifier; a second detection step of detecting an amplitude level of the output side of the amplifier based on a signal obtained by branching off a part of the signal output from the amplifier; a gain detection step of detecting a gain of the amplifier by comparing an amplitude level detected in the first detection step with an amplitude level detected in the second detection step; a gain control step of controlling a gain of a signal obtained by branching off a part of the signal input to the amplifier in accordance with a difference between an amplitude level detected in the first detection step and an amplitude level detected in the second detection step; a subtraction step of calculating a difference between a signal obtained by branching off a part of the signal output from the amplifier and a signal whose gain has been controlled in the gain control step; a third detection step of detecting an output level of the subtraction step; a passing phase detection step of detecting a passing phase of the amplifier based on the output level detected in the third detection step and the gain detected in the gain detection step.

6. A monitoring method for monitoring a wireless device including an amplifier that receives a signal to be wirelessly transmitted and amplifies the input signal to a predetermined level, and an antenna that transmits the signal amplified by the amplifier, comprising: a first detection step of detecting an amplitude level of an input side of the amplifier based on a signal obtained by splitting a part of a signal input to the amplifier; a second detection step of detecting an amplitude level of the output side of the amplifier based on a signal obtained by branching off a part of the signal output from the amplifier; a gain detection step of detecting a gain of the amplifier by comparing an amplitude level detected in the first detection step with an amplitude level detected in the second detection step; a gain control step of controlling a gain of a signal obtained by branching off a part of the signal input to the amplifier in accordance with a difference between an amplitude level detected in the first detection step and an amplitude level detected in the second detection step; a subtraction step of calculating a difference between a signal obtained by branching off a part of the signal output from the amplifier and a signal whose gain has been controlled in the gain control step; a third detection step of detecting an output level of the subtraction step; a passing phase detection step of detecting a passing phase of the amplifier based on the output level detected in the third detection step and the gain detected in the gain detection step.

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