JP2004235845A - Receiver mounted on helicopter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver mounted on a helicopter which has a small-sized and simple structure and has an excellent ratio of C/N in communication with a helicopter side as a receiving station. <P>SOLUTION: An interruption timing estimating part 14 estimates a timing when a rotating wing 8 interrupts a reception beam, while a noise eliminating part 15 makes an amplitude of a received signal in the interruption timing estimated by a disconnection timing estimating part 14 zero. A time diversity synthesizing part 16 performs time diversity synthesis by using a signal from which a noise is eliminated by the noise eliminating part 15, and a desired received signal is obtained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a helicopter-mounted receiver that is mounted on a helicopter and receives a signal transmitted from a ground station via a communication satellite.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a technique for performing communication between a helicopter and a ground station via a communication satellite is known (for example, see Patent Document 1). Generally, when a radio wave from a communication satellite is received by a helicopter, the radio wave is cut off by a rotor, and continuous reception becomes impossible. In order to solve this problem, in the technology disclosed in Patent Document 1, two antennas are arranged below the rotating wing of a helicopter, and radio waves are received by switching these two antennas. Is being avoided. That is, the two antennas are mounted at separate positions on the helicopter, and when the rotor blade detector detects that one of the antennas has blocked the radio wave by the rotor blades, the reception is switched to the reception by the other antenna. Then, a continuous reception signal is generated by combining the intermittent reception signals obtained from the two antennas in the reception unit. This allows for continuous reception at the helicopter.
[0003]
Patent Document 2 discloses another technique for performing communication between a helicopter and a ground station via a communication satellite. In the technology disclosed in Patent Document 2, a radio wave transmitted from a ground station via a communication satellite is received by an antenna. A receiver connected to the antenna detects a reception level of a reception signal output from the antenna. Meanwhile, the data terminal calculates a reception timing of a reception signal output from the receiver. The phase difference detector detects a phase difference between the reception level and the reception timing, and stops transmission from the ground station when it is determined that the radio wave is cut off based on the detected phase difference. Thus, the control signal for controlling the transmission timing of the ground station is generated and transmitted to the ground station. This avoids that the rotor impedes communication.
[0004]
[Patent Document 1]
JP-A-5-167344 [Patent Document 2]
JP-A-7-22993
[Problems to be solved by the invention]
However, in the technology described in Patent Document 1, two antennas are required to realize continuous reception by switching antennas, so that the device becomes large and is mounted on a helicopter whose spatial arrangement is limited. Not suitable for
[0006]
Further, in the technology disclosed in Patent Document 2, when receiving a signal from a ground station, a control signal must be transmitted to the ground station in order to avoid interruption of radio waves by the rotating wing. Therefore, the configuration of the device becomes complicated, and a certain band is occupied for transmitting the control signal.
[0007]
Furthermore, when a communication system is implemented using the time diversity system, data of a portion of the signal received on the helicopter side where radio waves are cut off by the rotor blades is lost, and only thermal noise is received. Therefore, if time diversity combining is performed as it is, there is a problem that the C / N ratio (Carrier to Noise ratio) deteriorates due to the influence of thermal noise.
[0008]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to mount a helicopter having a small and simple structure and having a good C / N ratio in communication using a helicopter as a receiving station. It is to obtain a receiving device.
[0009]
[Means for Solving the Problems]
A helicopter-mounted receiving device according to the present invention, in order to achieve the above object, a receiver that receives a target signal sent from a ground station via a communication satellite in a time diversity system and outputs the signal as a received signal, A reception level calculator for calculating a reception level of the target signal in the receiver; and a shutoff timing estimation for estimating a shutoff timing at which the target signal is cut off by the helicopter rotor based on the reception level calculated by the reception level calculator. A noise removing unit that removes the amplitude of the received signal at the cutoff timing estimated by the cutoff timing estimating unit from the received signal output from the receiver to generate a diversity signal, and a diversity from the noise removing unit. Having a time diversity combining unit for performing time diversity combining using signals A.
[0010]
The helicopter-mounted receiving device according to the present invention, for the same purpose as described above, determines the direction of the communication satellite based on the sway data representing the attitude of the helicopter and the position data representing the position, and the orbit data representing the position of the communication satellite in orbit. A receiving direction calculating unit for calculating, a receiver for receiving a target signal transmitted from the ground station by the time diversity method from the direction calculated by the receiving direction calculating unit, and outputting the received signal as a received signal, and rotation of a helicopter rotor blade Based on the position and the direction of the communication satellite calculated by the reception direction calculation unit, a cutoff timing estimation unit that estimates a cutoff timing at which the target signal is cut off by the helicopter rotor, and a reception signal output from the receiver. The amplitude of the received signal at the cutoff timing estimated by the cutoff timing estimation unit is In which includes a noise removing unit that generates a signal, the time diversity combining unit that performs time diversity combining using diversity signal from the noise removing unit.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a helicopter-mounted receiver according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0012]
FIG. 1 is a diagram schematically showing a configuration of a satellite communication system to which a helicopter-mounted receiver according to Embodiments 1 and 2 of the present invention is applied.
[0013]
This satellite communication system includes a helicopter 1, a communication satellite 2, and a ground station 3. The helicopter 1 transmits a signal to the ground station 3 using a transmission line 4 passing through a communication satellite 2. Further, the helicopter 1 receives a signal (corresponding to the “target signal” of the present invention) transmitted from the ground station 3 using the receiving line 5 passing through the communication satellite 2.
[0014]
The helicopter 1 includes a transmission antenna 6 for transmitting an object to the ground station 3 using the transmission line 4 and a reception antenna 7 for receiving a radio wave transmitted from the ground station 3 using the reception line 5. I have. In this satellite communication system, a radio wave (hereinafter, referred to as a “reception beam”) transmitted using the reception line 5 is intermittently cut off as the rotor 8 of the helicopter 1 rotates.
[0015]
Embodiment 1 FIG.
A helicopter-mounted receiver according to Embodiment 1 of the present invention will be described. FIG. 2 is a block diagram showing a configuration of the helicopter-mounted receiver 9 according to the first embodiment. In FIG. 2, in order to clarify the positioning of the helicopter-mounted receiving device 9 in the satellite communication system, a ground station communication device 10 and a ground station transmitting antenna 11 constituting the ground station 3, a communication satellite 2, and The receiving antenna 7 mounted on the helicopter 1 is also illustrated.
[0016]
The receiving antenna 7 mounted on the helicopter 1 receives data transmitted from the ground station transmitting antenna 11 connected to the ground station communication device 10 via the communication satellite 2. The received signal from the receiving antenna 7 is sent to the helicopter-mounted receiver 9. In the first embodiment, the ground station 3 transmits data in a time diversity system.
[0017]
The helicopter-mounted receiver 9 includes a receiver 12, a reception level calculator 13, a cutoff timing estimator 14, a noise remover 15, a time diversity synthesizer 16, a demodulator 17, and a received signal processor 18.
[0018]
The receiver 12 performs low-noise amplification and frequency conversion on a reception signal from the reception antenna 7. The received signal subjected to the low-noise amplification and frequency conversion is sent to the noise removing unit 15.
[0019]
The reception level calculation unit 13 calculates a reception level of a reception signal from the reception antenna 7 at each reception timing. The calculated reception level is sent to the cutoff timing estimator 14 as a reception level signal.
[0020]
The cutoff timing estimating unit 14 estimates a cutoff timing, that is, a section where the reception beam is cut off by the rotor 8 of the helicopter 1, based on the reception level signal sent from the reception level calculation unit 13. As a method of estimating the cutoff timing, a method of estimating a section in which the reception level is equal to or less than a predetermined threshold as the cutoff timing, or a decrease in the reception level due to the cutoff of the reception beam by the rotor 8 of the helicopter 1 Since it occurs periodically, it is possible to employ a method of estimating, as the cutoff timing, a section in which the reception level of the continuously obtained reception signal is periodically reduced. The cutoff timing estimated by the cutoff timing estimating unit 14 is sent to the noise removing unit 15 as a cutoff timing signal.
[0021]
The noise removal unit 15 removes a reception signal in a section indicated by the cutoff timing signal sent from the cutoff timing estimation unit 14 from the reception signal sent from the receiver 12. This removal can be performed by reducing the amplitude of the received signal to zero. As a result, thermal noise caused by the reception beam being blocked by the rotary wings 8 is removed. The received signal from which the thermal noise has been removed by the noise removing unit 15 is sent to the time diversity combining unit 16 as a diversity signal.
[0022]
The time diversity combining unit 16 performs time diversity combining of the diversity signal obtained by removing the thermal noise by the noise removing unit 15. The combined signal obtained by the time diversity combining is sent to the demodulator 17. The demodulator 17 reproduces the signal received from the ground station 3 by demodulating the combined signal obtained by the time diversity combining unit 16 and sends the signal to the received signal processing unit 18.
[0023]
The received signal processing unit 18 processes a signal from the demodulator 17 to convert, for example, a voice signal from the ground station 3 into voice, and executes control according to a control signal from the ground station 3.
[0024]
Next, the operation of the helicopter-mounted receiver according to Embodiment 1 of the present invention will be described with reference to the flowchart shown in FIG.
[0025]
In the helicopter-mounted receiver, first, a reception level of a reception signal is calculated (step ST1). The calculation of the reception level is performed by the reception level calculation unit 13. As described above, the reception level calculator 13 calculates the reception level of the reception signal obtained from the reception antenna 7 at each reception timing.
[0026]
Next, the cutoff timing is estimated (step ST2). The estimation of the cutoff timing is performed by the cutoff timing estimating unit 14. That is, the reception level calculated in step ST1 is compared with a predetermined threshold. Then, the received signal having the reception level equal to or less than the threshold value is regarded as the reception signal in the section where the reception beam is cut off by the rotor 8, and the section where the reception level is lowered is recognized as the cutoff timing.
[0027]
Next, it is checked whether it is the cutoff timing (step ST3). That is, it is checked whether or not the current section is the section estimated to be the cutoff timing in step ST2. If it is determined that the timing is not the cutoff timing, the reception signal from the receiver 12 is left as it is, but if it is determined that the timing is the cutoff timing, noise removal is performed (step ST4). Specifically, the amplitude of the signal received from the receiver 12 is set to zero. The processing of steps ST3 and ST4 is performed by the noise removing unit 15. Thus, even in a section where the reception beam is cut off by the rotary wing 8 and only the thermal noise is obtained as the reception signal, the influence of the thermal noise can be removed.
[0028]
FIG. 4 shows the relationship between the received signal and the cutoff timing signal in the noise removing unit 15. As shown in FIG. 4A, the received signal is continuously obtained at predetermined time intervals. The cutoff timing signal is a signal having a low level (L level) or a high level (H level) as shown in FIG. In the section in which the cutoff timing signal is at the L level, there is no cutoff of the received beam by the rotor 8 of the helicopter 1, and the process of removing noise from the received signal is not performed. On the other hand, in a section in which the cutoff timing signal is at the H level, noise removal for reducing the amplitude of the received signal to zero is performed. The shut-off timing signal shown in FIG. 4B is generated by the shut-off timing estimating unit 14 described above.
[0029]
Next, time diversity combining is performed using the received signal from which the thermal noise has been removed by the processing of steps ST3 and ST4 as a diversity signal (step ST5). The operation of the time diversity combining will be described with reference to FIG. FIG. 5 shows a case where the ground station 3 transmits one signal four times at different timings (time diversity transmission), and the received signals from which the thermal noise corresponding to each has been removed are used as the diversity signals 1 to 4. Represents. In this example, the reception signal is cut off by the rotor 8 in the diversity signal 1.
[0030]
If the received signal is used as it is (without noise removal) for time diversity combining, the noise removal section of the diversity signal 1 is a portion containing only thermal noise, and noise (thermal noise) is generated after time diversity combining. The included signal is obtained. On the other hand, in the helicopter-mounted receiver according to the first embodiment, since the noise removal section of the diversity signal 1 is all zero, the signal after the time diversity combination does not include thermal noise, 8, it is possible to improve the deterioration of the C / N ratio due to the cutoff of the reception beam by the C.N.
[0031]
When the time diversity combining is completed, the sequence returns to step ST1, and the same processing is repeated thereafter. Thereby, continuous reception is possible while complementing the reception beam cut off by the rotor 8 of the helicopter 1.
[0032]
As described above, according to the helicopter-mounted receiver according to the first embodiment, when the signal transmitted from the ground station 3 via the communication satellite 2 is received by the helicopter 1, the rotor 8 receives the signal. Since the cutoff timing at which the beam is cut off is estimated and the amplitude of the received signal at the cutoff timing is set to zero to perform the time diversity combining, even if the cutoff of the received beam by the rotary wing 8 occurs, a good result is obtained after the time diversity combining. A received signal having a C / N ratio can be obtained.
[0033]
In addition, even if it is the cutoff timing, the process of stopping the communication is not required, so that it can be realized by a helicopter-mounted receiver with a simple configuration. Furthermore, since only one receiving antenna 7 is required, an inexpensive and small helicopter-mounted receiving device can be configured.
[0034]
Embodiment 2 FIG.
Next, a helicopter-mounted receiver according to Embodiment 2 of the present invention will be described. FIG. 6 is a block diagram showing a configuration of the helicopter-mounted receiver 19 according to the second embodiment. In FIG. 6, in order to clarify the positioning of the helicopter-mounted receiver 9 in the satellite communication system, a ground station communication device 10 and a ground station transmission antenna 11, a ground station transmission antenna 11, a communication satellite 2, and a helicopter The receiving antenna 7 mounted on 1 is also depicted. In the following, the same or corresponding parts as in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description will be omitted.
[0035]
The helicopter-mounted receiver 19 includes a receiver 12, a noise remover 15, a time diversity synthesizer 16, a demodulator 17, a received signal processor 18, an inertial navigation device 20, a rotary wing detector 21, a satellite direction calculator 22, It comprises a receiving direction calculator 23 and a cutoff timing estimator 24.
[0036]
Among the above components, the inertial navigation device 20 and the rotary wing detector 21 are devices necessary for the navigation of the airframe, and are originally mounted on the helicopter 1. In the helicopter-mounted receiving device 19 according to the second embodiment, the receiving operation is controlled by using the signals output from the inertial navigation device 20 and the rotary wing detector 21. Therefore, in FIG. It is described as a part of the components of the receiving device 19.
[0037]
The inertial navigation device 20 outputs position data representing the position of the aircraft, such as latitude, longitude, and altitude, and sway data representing the attitude of the aircraft, such as a roll axis, a pitch axis, and an azimuth axis. The position data and the sway data output from the inertial navigation device 20 are sent to the satellite direction calculation unit 22 and the reception direction calculation unit 23.
[0038]
The rotating blade detector 21 detects that the rotating blade 8 has reached a specific rotation position every time the rotating blade 8 makes one rotation in the rotation direction of a rotating shaft (not shown), similarly to the tachometer that measures the rotation speed. Output as a wing detection signal. The rotary wing detector 21 detects, for example, a mark (such as a pin made of a magnetic material) provided on the rotary wing 8 or its rotating shaft by a detector (a magnetic detector or the like) fixed at a specific position of the fuselage.
[0039]
This rotor wing detector 21 is used for calculating the rotation speed of the rotor 8 by counting the number of rotations of the rotor 8 in a fixed time during normal navigation of the aircraft. Since the rotor wing detector 21 has a simple configuration, a detector having the same configuration as the rotor wing detector 21 mounted for navigating the helicopter 1 may be separately provided.
[0040]
The satellite direction calculator 22 calculates the helicopter 1 based on the position data of the airframe received from the inertial navigation device 20 and the orbit data (latitude, longitude, altitude data) indicating the position of the communication satellite 2 in orbit stored in advance. The direction of the communication satellite 2 as viewed from is calculated. The direction calculated by the satellite direction calculation unit 22 is sent to the reception direction calculation unit 23 as direction data.
[0041]
The reception direction calculation unit 23 calculates the direction of the reception beam based on the direction data received from the satellite direction calculation unit 22 and the fluctuation data of the aircraft sent from the inertial navigation device 20. Data indicating the direction of the reception beam calculated by the reception direction calculation unit 23 is sent to an actuator (not shown). Thereby, the receiving antenna 7 is controlled so as to face the direction of the receiving beam. The data indicating the direction of the reception beam calculated by the reception direction calculation unit 23 is sent to the cutoff timing estimation unit 24.
[0042]
The cutoff timing estimator 24 estimates the timing at which the rotor 8 cuts off the reception beam based on the data indicating the direction of the reception beam sent from the reception direction calculator 23.
[0043]
Next, the operation of the helicopter-mounted receiver according to Embodiment 2 of the present invention will be described with reference to the flowchart shown in FIG.
[0044]
In this helicopter-mounted receiver, first, the satellite direction is calculated (step ST10). That is, based on the position data of the aircraft transmitted from the inertial navigation device 20 and the pre-stored position information (latitude, longitude, altitude information) of the communication satellite 2 on the orbit, the communication satellite 2 viewed from the helicopter 1 Is calculated. The calculation of the satellite direction is performed by the satellite direction calculation unit 22.
[0045]
Next, the receiving direction is calculated (step ST11). In other words, the direction of the received beam is calculated based on the direction of the communication satellite 2 obtained in step ST10 and the data of the motion of the aircraft sent from the inertial navigation device 20. The calculation of the receiving direction is performed by the receiving direction calculator 23. The receiving antenna 7 of the helicopter 1 is directed to the direction of the receiving beam calculated in step ST11.
[0046]
Next, it is checked whether the rotary wing 8 has been detected (step ST12). The detection of the rotor 8 is performed by checking whether or not a rotor detection signal is output from the rotor detector 21 mounted on the helicopter 1. As described above, the rotating blade detector 21 outputs a rotating blade detection signal when the rotating blade 8 reaches a specific rotation position during one rotation.
[0047]
If it is determined in this step ST12 that the rotor 8 has not been detected, the process proceeds to the time diversity combining process in step ST15. On the other hand, when it is determined that the rotary wing 8 has been detected, next, the cutoff timing is estimated (step ST13). The estimation of the cutoff timing is performed by the cutoff timing estimating unit 14.
[0048]
In other words, the current position of the rotating blade 8 in the rotating direction can be determined by generating a rotating blade detection signal from the rotating blade detector 21. In step ST11, the arrival direction of the received beam as viewed from the body of the helicopter 1 (or the helicopter-mounted receiver) is calculated. Therefore, when the rotor 8 at a specific position cuts off the reception beam should be estimated based on the rotation speed of the rotor 8 which is separately calculated based on the rotor detection signal from the rotor detector 21. Can be. In this step ST13, it is estimated whether or not the cutoff is performed for each reception beam, and a cutoff timing is generated.
[0049]
Next, noise removal is performed (step ST14). This noise removal is performed by generating a diversity signal in which the amplitude of the reception signal at the cutoff timing is made zero among the reception signals transmitted from the receiver 12. At the timing when the receiving beam is cut off by the rotor 8, a receiving signal consisting of only thermal noise is received. Therefore, the influence of thermal noise can be eliminated by setting the amplitude of the received signal received at this timing to zero.
[0050]
Next, time diversity combining is performed (step ST15). The processing in step ST15 is the same as the processing in step ST5 in the first embodiment described above. If the noise removal is performed in step ST14, information included in the received signal is partially lost. However, by performing time diversity synthesis, the missing information is complemented by the same signal received at another timing. Is possible. If at least one received signal can be obtained at a timing that is not interrupted by the rotor 8, the received signal can be restored well.
[0051]
Thereafter, the sequence returns to step ST10, and the same processing is repeated thereafter. Thereby, continuous reception is possible while complementing the reception beam cut off by the rotor 8 of the helicopter 1.
[0052]
As described above, according to the helicopter-mounted receiver according to the second embodiment, similarly to the helicopter-mounted receiver according to the first embodiment, even when the reception beam is cut off by the rotor 8, the time is reduced. After the diversity combining, a received signal having a good C / N ratio can be obtained, and it can be realized with a helicopter-mounted receiver with a simple configuration.
[0053]
In addition, since only one receiving antenna 7 is required, and the rotary wing detector originally mounted on the helicopter can be used, an inexpensive and small helicopter-mounted receiver can be configured.
[0054]
【The invention's effect】
As described above, according to the present invention, in communication with a helicopter side as a receiving station, a reception level at a receiver is calculated, and based on the reception level, a timing of blocking a reception signal by a rotor of a helicopter is estimated, Since the diversity synthesis is performed after removing the amplitude of the received signal at the estimated timing, it is possible to obtain a helicopter-mounted receiver having a good C / N ratio, a small size and a simple structure. There is.
[0055]
According to the present invention, in communication using the helicopter as a receiving station, the direction of the communication satellite is calculated based on the sway data representing the attitude of the helicopter, the position data representing the position, and the orbit data representing the position of the communication satellite in orbit. Then, based on the calculated direction and the rotational position of the helicopter rotor, the cutoff timing of the received signal by the rotor of the helicopter is estimated, and diversity synthesis is performed after removing the amplitude of the received signal at the estimated timing. With such a configuration, it is possible to obtain a helicopter-mounted receiver having a good C / N ratio, a small size, and a simple structure.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of a satellite communication system to which a helicopter-mounted receiver according to Embodiments 1 and 2 of the present invention is applied.
FIG. 2 is a block diagram showing a configuration of a helicopter-mounted receiver according to Embodiment 1 of the present invention.
FIG. 3 is a flowchart showing an operation of the helicopter-mounted receiver according to Embodiment 1 of the present invention.
FIG. 4 is a diagram for explaining a relationship between a reception signal and a cutoff timing signal in the helicopter-mounted receiver according to Embodiments 1 and 2 of the present invention.
FIG. 5 is a diagram for explaining a time diversity combining process of the helicopter-mounted receiver according to the first and second embodiments of the present invention.
FIG. 6 is a block diagram showing a configuration of a helicopter-mounted receiver according to Embodiment 2 of the present invention.
FIG. 7 is a flowchart showing the operation of the helicopter-mounted receiver according to Embodiment 2 of the present invention.
[Explanation of symbols]
Reference Signs List 1 helicopter, 2 communication satellite, 3 ground station, 4 transmission line, 5 reception line, 6 transmission antenna, 7 reception antenna, 8 rotary wing, 10 ground station communication device, 11 ground station transmission antenna, 12 receiver, 13 reception Level calculation section, 14 cutoff timing estimation section, 15 noise removal section, 16-hour diversity synthesis section, 17 demodulator, 18 received signal processing section, 20 inertial navigation device, 21 rotary wing detector, 22 satellite direction calculation section, 23 reception Direction calculation unit, 24 cutoff timing estimation unit.

Claims (2)

A helicopter-mounted receiver that is mounted on a helicopter and communicates with a ground station via a communication satellite,
A receiver that receives a target signal sent from the ground station in a time diversity system and outputs the received signal as a received signal,
A reception level calculation unit that calculates a reception level of the target signal in the receiver,
Based on the reception level calculated by the reception level calculation unit, a cutoff timing estimation unit that estimates a cutoff timing at which the target signal is cut off by the rotor of the helicopter,
Of the reception signals output from the receiver, a noise removal unit that generates a diversity signal by removing the amplitude of the reception signal at the cutoff timing estimated by the cutoff timing estimation unit,
A helicopter-mounted receiving device, comprising: a time diversity combining unit that performs time diversity combining using the diversity signal from the noise removing unit. A helicopter-mounted receiver that is mounted on a helicopter and communicates with a ground station via a communication satellite,
A receiving direction calculation unit that calculates the direction of the communication satellite based on the sway data representing the attitude of the helicopter and the position data representing the position and the orbit data representing the position of the communication satellite in orbit,
A receiver that receives a target signal transmitted from the ground station in a time diversity system from the direction calculated by the reception direction calculation unit, and outputs the received signal as a reception signal.
Based on the rotational position of the rotor of the helicopter and the direction of the communication satellite calculated by the receiving direction calculator, based on the direction of the communication satellite, an interrupt timing estimator that estimates an interrupt timing at which the target signal is interrupted by the rotor of the helicopter. ,
Of the reception signals output from the receiver, a noise removal unit that generates a diversity signal by removing the amplitude of the reception signal at the cutoff timing estimated by the cutoff timing estimation unit,
A helicopter-mounted receiving device, comprising: a time diversity combining unit that performs time diversity combining using the diversity signal from the noise removing unit.

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