Communication device, control method for communication device, program, and communication system

Abstract

To synchronize clock signals between communication devices even in an environment in which phase changes occur due to fluctuations in radio transmission path characteristics.SOLUTION: A communication device receives a radio signal including a reference clock signal from another communication device, measures the distance and direction of movement of the communication device relative to the position of the other communication device, calculates an amount of phase change of the received radio signal due to fluctuations in the characteristics of a radio transmission path between the other communication device and the communication device based on the distance and direction of movement, determines a division ratio based on the amount of phase change, and regenerates a clock signal by dividing the received radio signal in accordance with the division ratio.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a communication device, a control method for a communication device, a program, and a communication system. [Background technology]

[0002] In a device (hereinafter referred to as a clock recovery device) that receives a radio signal synchronized with a reference clock signal transmitted from a device equipped with a reference clock signal source (hereinafter referred to as a clock source device), a technology is known for recovering a clock signal from the radio signal. Patent document 1 discloses a technology in which, by taking advantage of the fact that the characteristics of a wireless transmission path, which is the space through which a wireless signal travels, are known, a clock recovery device corrects the phase delay of a recovered clock signal by a phase delay corresponding to the wireless transmission path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-44437 A Summary of the Invention [Problem to be solved by the invention]

[0004] In wireless communication, in an environment where the position of the communicating antenna changes or objects near the wireless transmission path move, the phase of the wireless signal may change due to the effects of Doppler shift and multipath caused by changes in the distance of the wireless transmission path. However, when the antennas are in the far field and the change in distance is relatively small, the phase change according to the electric field distribution becomes dominant. Here, the latter phase change according to the electric field distribution is referred to as the phase change due to the change in the wireless transmission path characteristics.

[0005] When no phase change occurs due to fluctuations in the wireless transmission path characteristics, only the phase delay of the wireless transmission path needs to be considered, and according to the technology disclosed in Patent Document 1, it is possible to synchronize the clock signal recovered by the clock recovery device with the reference clock signal in the clock source device.

[0006] However, when a phase change occurs due to a fluctuation in the characteristics of the wireless transmission line, the technique disclosed in this document has the problem that the reference clock signal in the clock source device and the clock signal recovered by the clock recovery device are not synchronized.

[0007] The present invention has been made in view of the above problems, and has an object to synchronize clock signals between communication devices even in an environment in which phase changes occur due to fluctuations in wireless transmission path characteristics. [Means for solving the problem]

[0008] As one means for achieving the above object, the communication device of the present invention has the following configuration: namely, receiving means for receiving a radio signal including a reference clock signal from another communication device, measuring means for measuring a moving distance and a moving direction of the communication device relative to a position of the other communication device, calculating means for calculating an amount of phase change due to a phase change of the received radio signal caused by a fluctuation in characteristics of a radio transmission path between the other communication device and the communication device based on the moving distance and the moving direction, determining means for determining a frequency division ratio based on the amount of phase change, and frequency division means for regenerating a clock signal by dividing the received radio signal in accordance with the frequency division ratio. Effect of the Invention

[0009] It is possible to synchronize the clock signals of communication devices even in an environment in which phase changes occur due to fluctuations in wireless transmission path characteristics. [Brief description of the drawings]

[0010] [Figure 1] 1 illustrates an example of the configuration of a wireless transmission system according to a first embodiment. [Diagram 2] 3 illustrates an example of the configuration of a transmission processing unit of a clock source device in the first embodiment. [Diagram 3] 3 illustrates an example of the configuration of a reception processing unit of a clock recovery device according to the first embodiment. [Figure 4] FIG. 2 is a diagram showing the positional relationship of antennas in a wireless transmission path. [Diagram 5] 4 shows a flowchart of a process executed by a clock recovery device in the first embodiment. [Figure 6] 13 illustrates an example of the configuration of a wireless transmission system according to a second embodiment. [Figure 7] 13 illustrates an example of the configuration of a transmission processing unit of a clock source device according to a second embodiment. [Figure 8] 13 illustrates an example of the configuration of a reception processing unit of a clock recovery device according to a second embodiment. [Figure 9] 13 shows a flowchart of a process executed by a clock recovery device in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the embodiment described below is one example of a means for realizing the present invention, and should be appropriately modified or changed depending on the configuration of the device to which the present invention is applied and various conditions, and the present invention is not limited to the embodiment described below.

[0012] <First embodiment> 1 shows an example of the configuration of a wireless transmission system 1 according to this embodiment. The wireless transmission system 1 is a communication system including a clock source device 100 that generates a reference clock signal, and a clock recovery device 200 that recovers a clock signal so as to be synchronized with the reference clock signal.

[0013] The clock source device 100 is composed of a reference clock signal source 102 that generates a reference clock signal Sr, a transmission processing unit 101 that generates a radio signal from the reference clock signal Sr input from the reference clock signal source 102, and a transmitting antenna unit 103 that transmits the radio signal. The clock recovery device 200 is composed of a receiving antenna unit 202 that receives the radio signal transmitted from the clock source device 100 via a wireless transmission path, and a receiving processing unit 201 that generates (regenerates) a clock signal Srx by correcting the phase of the received radio signal. In this embodiment, the function for synchronizing the clock signal Srx with the reference clock signal Sr will be mainly described, but both the clock source device 100 and the clock recovery device 200 may be configured to be capable of generating and transmitting any signal. Also, the transmitting antenna unit 103 and the receiving antenna unit 202 may each be configured to include one or more antennas.

[0014] Next, the configurations and functions of the transmission processing unit 101 of the clock source device 100 and the reception processing unit 201 of the clock recovery device 200 will be described in more detail. First, the transmission processing unit 101 of the clock source device 100 will be described with reference to Fig. 2. Fig. 2 shows an example of the configuration of the transmission processing unit 101 of the clock source device 100 according to this embodiment. The transmission processing unit 101 is composed of a transmission circuit unit 111 and a code data generating unit 112, and a transmission antenna unit 103 is connected to the transmission circuit unit 111. In this embodiment, the transmission antenna unit 103 is composed of a transmission antenna 103A. The transmission circuit unit 111 is composed of a PLL (phase locked loop) 113, a mixer 114, and a modulation unit 115, and generates a radio signal from a reference clock signal Sr input from a reference clock signal source 102. The code data generating unit 112 generates an encoded signal based on the reference clock signal Sr input from the reference clock signal source 102.

[0015] The code data generating unit 112 generates a coded signal consisting of 0 and 1. In this embodiment, the code data generating unit 112 can generate a coded signal in which 0 and 1 are random and of equal frequency. For example, a PRBS (Pseudo-Random Binary Sequence) is an example of a signal that satisfies such a condition. Furthermore, when it is desired to transmit a data signal together with a clock signal, a Manchester code or 6B10B (a method of converting 8-bit data into a 10-bit symbol) may be combined with the PRBS. The code data generating unit 112 may also generate a coded signal by encoding a PN9 (pseudo-random signal) with 8B10B (a method of converting 8-bit data into a 10-bit symbol). The code data generating unit 112 outputs the generated coded signal to the modulation unit 115 of the transmission circuit unit 111.

[0016] In the transmission circuit unit 111, the PLL 113 generates a carrier signal from the reference clock signal Sr input from the reference clock signal source 102, and outputs the carrier signal to the mixer 114. Specifically, the PLL 113 generates a carrier signal by up-converting the reference clock signal Sr to an arbitrary frequency using the division number of a frequency divider (not shown) included in the PLL 113. By generating the carrier signal in this manner, the reference clock signal Sr and the carrier signal are synchronized. The division number by the PLL 113 is known to the clock source device 100 and the clock recovery device 200. The division number may also be notified from the clock source device 100 to the clock recovery device 200 using a different wireless communication (not shown).

[0017] The modulation unit 115 generates an in-phase / quadrature-phase (IQ) modulated signal based on the coded signal input from the coded data generation unit 112. The clock signal used for IQ modulation may be a carrier signal generated by a reference clock signal Sr or the PLL 113, or may be a clock signal generated by an external clock source (not shown). The modulation method is, for example, continuous phase frequency shift keying (CPFSK). In CPFSK, the average clock of the IQ modulated signal varies depending on the total number of 0s and 1s in the coded signal. For example, when there are many 0s, the average clock is low, and when there are many 1s, the average clock is high. When the modulation is reversed, when there are many 0s, the average clock is high, and when there are many 1s, the average clock is low. The modulation method is not limited to CPFSK.

[0018] The mixer 114 generates a signal by mixing the carrier signal input from the PLL 113 and the IQ modulated signal input from the modulation unit 115 as a radio signal, and outputs the signal to the transmitting antenna 103A. The transmitting antenna 103A sends the radio signal generated by the mixer 114 to a radio transmission path and transmits it to the clock recovery device 200.

[0019] Next, the reception processing unit 201 of the clock recovery device 200 will be described with reference to FIG. 3. FIG. 3 shows an example of the configuration of the reception processing unit 201 of the clock recovery device 200 according to this embodiment. The reception processing unit 201 is composed of a reception circuit unit 211 and a phase adjustment unit 212, and a reception antenna unit 202 is connected to the reception circuit unit 211. In this embodiment, the reception antenna unit 202 is composed of a reception antenna 202A. The reception circuit unit 211 is composed of a band pass filter 213, an AGC (automatic gain control) 214, and a frequency divider 215, and recovers a clock signal Srx from the received radio signal. The phase adjustment unit 212 is composed of a measurement unit 216 and a frequency division ratio adjustment unit 217, and generates a control signal for adjusting the ratio of down-conversion by the frequency divider 215 according to a phase change of the received radio signal.

[0020] In the receiving circuit unit 211, the bandpass filter 213 passes only a radio signal of a desired frequency among the radio signals received via the receiving antenna 202A, and inputs the signal to the AGC 214. The AGC 214 adjusts the amplitude of the radio signal input from the bandpass filter 213 to a constant value, and inputs the signal to the frequency divider 215. The frequency divider 215 corrects the frequency division ratio of the radio signal input from the AGC 214 with respect to a known frequency division ratio based on a control signal input from the phase adjustment unit 212, and then down-converts the signal (i.e., corrects the phase of the radio signal) to reproduce (extract) a clock signal Srx. The frequency divider 215 outputs the reproduced clock signal Srx to a subsequent processing unit (not shown).

[0021] In the phase adjustment unit 212, the measurement unit 216 measures a movement amount indicating a movement distance and a movement vector indicating a movement direction due to the movement of the receiving antenna 202A (or the clock recovery device 200 main body). Specifically, the measurement unit 216 detects the movement of the receiving antenna 202A (or the clock recovery device 200 main body) as an acceleration, and calculates the movement amount by integrating the acceleration over time. The measurement unit 216 also detects geomagnetism and estimates a movement vector based on the detected geomagnetism. In this embodiment, the measurement unit 216 is assumed to be an acceleration sensor, but it can be replaced by other sensors such as a GPS (Global Propositioning System) or a body movement sensor, and may be configured by combining multiple sensors. The measurement unit 216 can continue to operate as long as the power supply of the clock recovery device 200 is ON. The measurement unit 216 outputs the movement amount and the movement vector to the frequency division ratio adjustment unit 217. The division ratio adjustment unit 217 determines the division ratio (i.e., the down-conversion ratio) of the divider 215 of the receiving circuit unit 211 based on the amount of movement and the movement vector input from the measurement unit 216, generates a control signal including information on the determined division ratio, and outputs it to the divider 215. Note that the control signal may be a difference value for correcting a known division ratio, or may be the division ratio after correction. In any case, in the wireless transmission system 1 according to this embodiment, the clock source device 100 does not adjust the phase of the clock signal, and the clock recovery device 200 is configured to be the main body of the phase adjustment and recover the clock signal from the received signal.

[0022] Next, a procedure for determining the division ratio from the movement amount and movement vector by the division ratio adjustment unit 217 will be described with reference to Fig. 4. Fig. 4 is a diagram showing the positional relationship of antennas in a wireless transmission path. In Fig. 4, the positions of the transmitting antenna 103A and the receiving antenna 202A are represented in a three-dimensional space (X-axis, Y-axis, Z-axis). Note that the positions of the transmitting antenna 103A and the receiving antenna 202A may be the positions of the clock source device 100 and the clock recovery device 200, respectively.

[0023] In this embodiment, it is assumed that the clock source device 100 and the clock recovery device 200 are arranged opposite to each other, and that the clock recovery device 200 vibrates periodically (performs a repetitive motion). For example, in a wireless sensor device that remotely monitors a human body's biosignal, the clock source device 100 is provided in a monitoring device, and the clock recovery device 200 having a sensor device is worn on the human body, and the periodic vibration corresponds to the body movement of the human body. In this embodiment, it is assumed that the amplitude of the repetitive motion is shorter than one period of the wireless signal transmitted and received between the clock source device 100 and the clock recovery device 200. In this embodiment, the reference position (hereinafter, reference position) of the receiving antenna 202A at a reference time (hereinafter, reference time) is set in advance, and its coordinates in three-dimensional space are known. The position of the transmitting antenna 103A is fixed, and its coordinates in three-dimensional space are known.

[0024] In FIG. 4, the position P-103A of the transmitting antenna 103A and the reference position P-202A' of the receiving antenna 202A are defined, and the receiving antenna 202A periodically repeats moving from the reference position P-202A' to a position P-202A". At this time, since the position P-103A of the transmitting antenna 103A and the reference position P-202A' of the receiving antenna 202A are known, the distance Lsrx' between the two positions is also known (i.e., the distance Lsrx' is defined). In FIG. 4, the distance Lsrx' is represented by a dashed dotted line. When the movement amount and movement vector are input from the measurement unit 216, the frequency division ratio adjustment unit 217 resolves the movement vector into three axes, the X-axis, Y-axis, and Z-axis, and multiplies it by the movement amount to identify the coordinates of the position P-202A" of the receiving antenna 202A. Next, the frequency division ratio adjustment unit 217 calculates the distance Lsrx" between the position P-103A of the transmitting antenna 103A and the position P-202A" of the receiving antenna 202A from the coordinates of these two points. Since the distance Lsrx" is expressed as Lsrx'+ΔL, the frequency division ratio adjustment unit 217 calculates ΔL by subtracting the known distance Lsrx' from the calculated distance Lsrx". In FIG. 4, ΔL is represented by a dotted line.

[0025] The frequency division ratio adjustment unit 217 acquires the phase change amount (i.e., the phase change amount associated with the repetitive motion of the clock recovery device 200) of the received radio signal due to the movement of the transmitting antenna 103A (i.e., the movement of the clock recovery device 200) based on the calculated ΔL. For example, if a phase change amount proportional to ΔL is pre-stored in a memory (not shown) of the clock recovery device 200, the frequency division ratio adjustment unit 217 acquires the corresponding phase change amount from the memory based on ΔL. Alternatively, the frequency division ratio adjustment unit 217 may acquire the phase change amount by calculating the phase change amount from ΔL. Then, the frequency division ratio adjustment unit 217 determines the frequency division ratio from the phase change amount, generates a control signal including information of the determined frequency division ratio, and outputs the control signal to the frequency divider 215.

[0026] The frequency division ratio will be described using a specific numerical example. If the radio signal is 2.45 GHz, one wavelength of the radio signal is approximately 122 mm, one period is 408 psec, and when ΔL is 30 mm, the time corresponds to 100 psec. If the reference clock signal Srx is 10 MHz and a 2.45 GHz radio signal is used, the frequency division ratio is 245. If the phase change due to the change in the position of the receiving antenna 202A is regarded as an instantaneous frequency change of the radio signal, one period of the radio signal received by the clock recovery device 200 is 308 (=408-100) psec (i.e., the phase change amount is -100 psec). Therefore, the frequency division ratio adjustment unit 217 can calculate the frequency division ratio for the 3.24 GHz radio signal corresponding to 308 psec as 324. The frequency divider 215 uses this frequency division ratio to synchronize the clock signal Srx and the reference clock signal Sr at 10 MHz.

[0027] In this numerical example, the direction is one in which the receiving antenna 202A approaches the transmitting antenna 103A, and the phase change is expressed as a subtraction (negative value) (i.e., -100), but the addition or subtraction of the phase change can be determined by the movement vector. That is, the frequency division ratio adjustment unit 217 specifies whether the receiving antenna 202A (clock recovery device 200) approaches (approaches) the transmitting antenna 103A (clock source device 100) or moves away (away) from the transmitting antenna 103A based on the movement vector. Then, the frequency division ratio adjustment unit 217 subtracts 308 psec in the direction in which the receiving antenna 202A approaches the transmitting antenna 103A, and adds 508 (=408+100) psec in the direction in which the receiving antenna 202A moves away from the transmitting antenna 103A.

[0028] The division ratio adjustment unit 217 executes a series of processes for calculating the division ratio continuously in real time, but may execute the process only at a predetermined timing where phase matching is strictly required as a wireless transmission system. In that case, a periodic phase shift occurs based on 10 MHz in the recovered clock signal except at the predetermined timing, and 10 MHz is recovered only at the predetermined timing. In the above description, the frequencies, division ratios, and ΔL of the radio signal and the clock signal are merely examples, and any values ​​may be used. For example, the known distance Lsrx′ may be provided from the clock source device 100 to the clock recovery device 200 as position information.

[0029] Although the position of the receiving antenna 202A is defined on a three-dimensional coordinate system (X-axis, Y-axis, Z-axis), the present embodiment may also include corrections using parameters such as the tilt or rotation of the receiving antenna 202A, or the pitch, yaw, and roll. In that case, the measurement unit 216 of the clock recovery device 200 may be configured using a sensor corresponding to the tilt, rotation, and the like.

[0030] 5 shows a flowchart of the process executed by the clock recovery device 200 according to this embodiment. First, the antenna 202A receives the radio signal transmitted from the clock source device 100 and passed through the radio transmission path (S51). Next, the measurement unit 216 measures the amount of movement indicating the movement distance and the movement vector indicating the movement direction due to the movement of the receiving antenna 202A (or the clock recovery device 200 main body) (S52). The division ratio adjustment unit 217 acquires the amount of phase change based on the amount of movement and the movement vector (S53), and determines the division ratio based on the amount of phase change (S54). The divider 215 down-converts the radio signal input from the AGC 214 according to the division ratio determined in S54, thereby regenerating (extracting) the clock signal Srx (S55).

[0031] Thus, according to this embodiment, the clock recovery device 200 corrects the phase of the received wireless signal to synchronize the clock signal Srx with the reference clock signal Sr. This makes it possible to synchronize the clock signals of two communication devices in a wireless communication environment even in an environment where phase changes occur due to fluctuations in wireless transmission path characteristics. Therefore, a system (not shown) including a clock source device 100 that operates using the reference clock signal Sr and a system (not shown) including a clock recovery device 200 that operates using the clock signal Srx can operate at the same timing within a range in which the clock signal can be wirelessly transmitted.

[0032] <Second embodiment> In the first embodiment, it is assumed that the position of the receiving antenna unit 202 at the reference time is known (reference position P-202A' in FIG. 4). In the present embodiment, it is assumed that the position of the receiving antenna unit 202 at the reference time is not known.

[0033] Fig. 6 shows an example of the configuration of a wireless transmission system 2 according to this embodiment. The wireless transmission system 2 includes a clock source device 100 that generates a reference clock signal, and a clock recovery device 200 that recovers a clock signal to be synchronized with the reference clock signal. Compared to the wireless transmission system 1 shown in Fig. 1 described in the first embodiment, the clock source device 100 differs in that it has a transmission processing unit 601 and an imaging unit 602, and the clock recovery device 200 has a reception processing unit 603. Below, a description of the configuration common to the first embodiment will be omitted, and only the different configuration will be described.

[0034] In the first embodiment, as described with reference to Fig. 4, it was necessary to define the distance Lsrx' between the position P-103A of the transmitting antenna 103A at the reference time and the reference position P-202A' of the receiving antenna 202A. Since the measuring unit 216 continues to operate as long as the power of the clock recovery device 200 is ON, if the distance Lsrx' is not known, the clock recovery device 200 needs a function to determine which movement should be corrected. Therefore, in this embodiment, at a time or under conditions when the clock signals of the two communication devices must be wirelessly synchronized, the clock source device 100 detects that the clock recovery device 200 is oscillating periodically, and transmits information related to the period to the clock recovery device 200. Then, the clock recovery device 200 is configured to define the distance Lsrx' using the information related to the period.

[0035] 7 shows an example of the configuration of the transmission processing unit 601 of the clock source device 100 according to this embodiment. The transmission processing unit 601 is composed of a transmission circuit unit 111, a code data generating unit 112, a transmission circuit unit 701, and an image processing unit 702, and a transmission antenna unit 103 is connected to the transmission circuit unit 111 and the transmission circuit unit 701. In this embodiment, the transmission antenna unit 103 is composed of a transmission antenna 103A and a transmission antenna 103B, the transmission antenna 103A is connected to the transmission circuit unit 111, and the transmission antenna 103B is connected to the transmission circuit unit 701. The configurations of the transmission circuit unit 111 and the code data generating unit 112 are as described in the first embodiment.

[0036] The photographing unit 602 has a photographing function and photographs the main body of the clock recovery device 200 or the receiving antenna unit 202 of the clock recovery device 200 at continuous time, and outputs the image data obtained by photographing to the image processing unit 702 of the transmission processing unit 601. The image processing unit 702 performs image determination based on the image data input from the photographing unit 602 to determine whether the clock recovery device 200 vibrates periodically, and acquires the period. For example, when the clock source device 100 is provided in a monitoring device and the clock recovery device 200 having a sensor device is worn on a human body, the image processing unit 702 detects and acquires the period of vibration of the clock recovery device 200 due to the human body's breathing (up and down movement of the chest). Note that an operator who operates the monitoring device may instruct the timing to start and end the image determination. The period may also be associated with information for identifying both ends of the amplitude of the vibration. The image processing unit 702 generates a notification signal including information on the acquired period, and outputs it to the transmission circuit unit 701. The transmission circuit unit 701 outputs a wireless signal including the notification signal to the transmission antenna 103B. For example, the transmission circuit unit 701 stores the notification signal in a data area of ​​a wireless LAN (Local Area Network), and outputs it to the transmission antenna 103B as a wireless signal. The transmitting antenna 103B sends the radio signal including the notification signal to the radio transmission path, and transmits it to the clock recovery device 200.

[0037] 8 shows an example of the configuration of the reception processing unit 603 of the clock recovery device 200 according to this embodiment. The reception processing unit 603 is composed of a reception circuit unit 211, a phase adjustment unit 801, and a reception circuit unit 802, and the reception antenna unit 202 is connected to the reception circuit unit 211 and the reception circuit unit 802. In this embodiment, the reception antenna unit 202 is composed of a reception antenna 202A and a reception antenna 202B, the reception antenna 202A is connected to the reception circuit unit 211, and the reception antenna 202B is connected to the reception circuit unit 802. The configuration of the reception circuit unit 211 is as described in the first embodiment.

[0038] The receiving circuit unit 802 extracts a notification signal from the wireless signal received by the receiving antenna 202B. The notification signal is the notification signal transmitted by the transmitting circuit unit 701 in FIG. 7 via the transmitting antenna 103. The receiving circuit unit 802 also measures the signal strength of the received wireless signal. Here, the receiving circuit unit 802 can measure the signal strength of the received wireless signal at both ends of the amplitude of oscillation of the clock recovery device 200 based on the period included in the notification signal. Then, the receiving circuit unit 802 links the notification signal to the signal strength of the received wireless signal and outputs it to the division ratio adjustment unit 803 of the phase adjustment unit 801.

[0039] In the phase adjustment unit 801, the measurement unit 216 measures the movement amount and the movement vector as described in the first embodiment, and outputs them to the division ratio adjustment unit 803. The division ratio adjustment unit 803 determines a division ratio for adjusting the division ratio of the frequency divider 215, based on the movement amount and the movement vector input from the measurement unit 216 and the notification signal input from the reception circuit unit 802 and linked to the signal strength of the received wireless signal. Then, the division ratio adjustment unit 803 generates a control signal including information on the determined division ratio, and outputs it to the frequency divider 215.

[0040] Next, a procedure for determining the division ratio from the movement amount, the movement vector, and the notification signal by the division ratio adjustment unit 803 will be described with reference to FIG. 4 referred to in the first embodiment. In this embodiment, the distance Lsrx' between the transmitting antenna 103A and the receiving antenna 202A' at the reference time is unknown. The frequency division ratio adjustment unit 803 first calculates the distance Lsrx' and the distance Lsrx" from the signal strength at both ends of the amplitude of the received wireless signal. Here, the distance Lsrx' and the distance Lsrx" calculated from the signal strength are scalar quantities. Next, when the movement amount and the movement vector are input from the measurement unit 216, the frequency division ratio adjustment unit 803 resolves the movement vector into three axes, the X-axis, the Y-axis, and the Z-axis, and multiplies it by the movement amount to calculate the distance Lsrx" between the transmitting antenna 103A and the receiving antenna 202A" after the movement. Here, the frequency division ratio adjustment unit 803 determines (defines) the distance Lsrx' to be the reference distance from the previously calculated distances Lsrx' and distances Lsrx" based on the distance Lsrx" calculated based on the movement vector and the movement amount. Since the distance Lsrx" is expressed as Lsrx'+ΔL, the frequency division ratio adjusting unit 803 calculates ΔL by subtracting the distance Lsrx' from the calculated distance Lsrx".

[0041] Next, the division ratio adjustment unit 803 acquires the amount of phase change based on ΔL. For example, as described in the first embodiment, if a phase change amount proportional to ΔL is stored in advance in a memory (not shown) of the clock recovery device 200, the division ratio adjustment unit 803 acquires the corresponding amount of phase change from the memory based on ΔL. Alternatively, the division ratio adjustment unit 217 may acquire the amount of phase change by calculating the amount of phase change from ΔL according to the procedure described in the first embodiment. Then, the division ratio adjustment unit 803 determines a division ratio from the amount of phase change, generates a control signal including information on the determined division ratio, and outputs it to the divider 215.

[0042] FIG. 9 shows a flowchart of the process executed by the clock recovery device 200 according to this embodiment. The same reference numerals are used for the process similar to that in the flowchart of FIG. 5 described in the first embodiment, and the description will be omitted. First, the receiving antenna 202B receives a radio signal including a notification signal transmitted from the clock source device 100 and passing through a radio transmission path (S91). After the measuring unit 216 measures the amount of movement indicating the moving distance and the movement vector indicating the moving direction (S52), the division ratio adjustment unit 803 acquires the amount of phase change (S92). In this embodiment, the division ratio adjustment unit 803 acquires the amount of phase change based on the amount of movement, the movement vector, and the notification signal. Thereafter, the division ratio adjustment unit 803 determines the division ratio (S54), and the divider 215 down-converts the radio signal input from the AGC 214 according to the division ratio determined in S54, thereby regenerating (extracting) the clock signal Srx (S55).

[0043] In the above description, the receiving circuit unit 802 measures the signal strength of a wireless signal received by the receiving antenna 202B, but the signal strength of the wireless signal may be measured from a wireless signal received by the receiving antenna 202A. In this case, the frequency division ratio adjustment unit 803 can calculate ΔL by combining the notification signal, the movement amount, and the movement vector.

[0044] In the wireless transmission system 2 according to the present embodiment, different frequencies may be used to prevent interference between the communication between the transmitting antenna 103A and the receiving antenna 202A and the communication between the transmitting antenna 103B and the receiving antenna 202B. For example, the two wireless transmission paths are separated by using a 2.5 GHz signal for the communication between the transmitting antenna 103A and the receiving antenna 202A and a 5.5 GHz signal for the communication between the transmitting antenna 103B and the receiving antenna 202B.

[0045] In this way, according to this embodiment, even if the position of the clock regeneration device 200 at the reference time is unknown, the clock regeneration device 200 can correct the phase of the received wireless signal from the information on the period of the received vibration. This makes it possible to synchronize the clock signal Srx with the reference clock signal Sr.

[0046] According to the embodiment described above, even in an environment in which phase changes occur due to fluctuations in wireless transmission path characteristics, it is possible to synchronize the reference clock signal of the clock source device with the clock signal recovered from a wireless signal by the clock recovery device.

[0047] <Other embodiments> The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0048] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) A communication device comprising: a receiving means for receiving a radio signal including a reference clock signal from another communication device; a measuring means for measuring a moving distance and a moving direction of the communication device relative to a position of the other communication device; a calculating means for calculating an amount of phase change of the received radio signal due to fluctuations in characteristics of a radio transmission path between the other communication device and the communication device based on the moving distance and the moving direction; a determining means for determining a division ratio based on the amount of phase change; and a frequency dividing means for regenerating a clock signal by dividing the received radio signal in accordance with the division ratio. A communication device having the above configuration.

[0049] (Configuration 2) The communication device according to configuration 1, wherein the amount of phase change is an amount of phase change associated with a periodic repetitive motion of the communication device.

[0050] (Configuration 3) A communication device according to configuration 2, wherein the amplitude of the repetitive motion is shorter than one period of the radio signal.

[0051] (Configuration 4) A communication device described in any of configurations 1 to 3, wherein a reference distance, which is the distance between the position of the other communication device and the position of the communication device at a reference time, is set in advance, and the calculation means calculates the amount of phase change based on the moving distance, the moving direction, and the reference distance.

[0052] (Configuration 5) The communication device described in configuration 4, wherein the calculation means determines whether the communication device is moving toward or away from the other communication device based on the direction of movement, and calculates the amount of phase change based on the determined direction.

[0053] (Configuration 6) A communication device described in configuration 4 or 5, wherein the period of the radio signal transmitted from the other communication device and the clock of the reference clock signal are set in advance, and the determination means determines the frequency division ratio using the period of the transmitted radio signal, the clock of the reference clock signal, and the amount of phase change.

[0054] (Configuration 7) A communication device described in any of configurations 1 to 6, wherein the receiving means receives another wireless signal including a notification signal indicating information about a period of the periodic repetitive motion of the communication device, and the calculation means calculates the amount of phase change based on the moving distance, the moving direction, and the notification signal.

[0055] (Configuration 8) The communication device described in Configuration 7, wherein the calculation means calculates signal strength at both ends of the amplitude of the received radio signal or the received another radio signal during the repetitive motion based on the period, determines a reference distance, which is the distance between the position of the other communication device and the position of the communication device at a reference time, based on the signal strength, and calculates the amount of phase change based on the moving distance, the moving direction, and the reference distance.

[0056] (Configuration 9) The communication device of configuration 7 or 8, wherein the communication device has a first antenna and a second antenna, and the receiving means receives the radio signal at a first frequency via the first antenna and receives the other radio signal at a second frequency via the second antenna.

[0057] (Configuration 10) A communication system including a first communication device and a second communication device, the first communication device has a first transmission means for transmitting a first wireless signal including a modulated signal encoded based on a reference clock, and a second transmission means for transmitting a second wireless signal including a notification signal indicating information on a period of a periodic repetitive motion of the second communication device, the period being determined based on an image of the second communication device captured by an image capturing unit; The second communication device has a first receiving means for receiving the first radio signal, a second receiving means for receiving the second radio signal, a measuring means for measuring a moving distance and a moving direction of the second communication device relative to a position of the first communication device, a calculating means for calculating an amount of phase change of the received first radio signal or the second radio signal due to fluctuations in characteristics of a radio transmission path between the first communication device and the second communication device based on the moving distance, the moving direction, and the notification signal included in the second radio signal, a determining means for determining a division ratio based on the amount of phase change, and a dividing means for regenerating a clock signal by dividing the received first radio signal or the second radio signal in accordance with the division ratio.

[0058] (Method 1) The method includes a receiving step of receiving a radio signal including a reference clock signal from another communication device, a measuring step of measuring a moving distance and a moving direction of the communication device relative to a position of the other communication device, a calculating step of calculating an amount of phase change of the received radio signal due to fluctuations in characteristics of a radio transmission path between the other communication device and the communication device based on the moving distance and the moving direction, a determining step of determining a division ratio based on the amount of phase change, and a dividing step of regenerating a clock signal by dividing the received radio signal in accordance with the division ratio. [Explanation of symbols]

[0059] 100: clock source device, 101: transmission processing unit, 102: reference clock signal source, 103: transmission antenna unit, 111: transmission circuit unit, 112: code data generation unit, 113: PLL (phase locked loop), 114: mixer, 115: modulation unit, 200: clock recovery device, 201: reception processing unit, 202: reception antenna unit, 211: reception circuit unit, 212: phase adjustment unit, 213: band pass filter, 214: AGC (automatic gain control), 215: frequency divider, 216: measurement unit, 217: frequency division ratio adjustment unit, 601: transmission processing unit, 602: imaging unit, 603: reception processing unit, 701: transmission circuit unit, 702: image processing unit, 801: phase adjustment unit, 802: reception circuit unit, 803: frequency division ratio adjustment unit

Claims

1. 1. A communication device, comprising: A receiving means for receiving a radio signal including a reference clock signal from another communication device; a measuring means for measuring a moving distance and a moving direction of the communication device relative to a position of the other communication device; a calculation means for calculating an amount of phase change of the received wireless signal caused by a fluctuation in characteristics of a wireless transmission path between the other communication device and the communication device based on the moving distance and the moving direction; a determining means for determining a frequency division ratio based on the phase change amount; a frequency division means for regenerating a clock signal by dividing the frequency of the received radio signal in accordance with the frequency division ratio; A communication device comprising:

2. 2. The communication device according to claim 1, wherein the phase change amount is an amount of phase change associated with a periodic repetitive motion of the communication device.

3. 3. The communication device of claim 2, wherein the amplitude of the repetitive motion is shorter than one period of the radio signal.

4. a reference distance between a position of the other communication device and a position of the communication device at a reference time is set in advance; The calculation means calculates the phase change amount based on the movement distance, the movement direction, and the reference distance.

2. The communication device according to claim 1 .

5. The communication device according to claim 4, characterized in that the calculation means determines whether the communication device is moving toward or away from the other communication device based on the direction of movement, and calculates the amount of phase change based on the determined direction.

6. a period of the radio signal transmitted from the other communication device and a clock of the reference clock signal are preset; 6. The communication device according to claim 4, wherein the determining means determines the frequency division ratio using a period of the transmitted radio signal, a clock of the reference clock signal, and the amount of phase change.

7. the receiving means receives another wireless signal including a notification signal indicating information about a period of the periodic repetitive motion of the communication device; 2. The communication device according to claim 1, wherein the calculation means calculates the amount of phase change based on the moving distance, the moving direction, and the notification signal.

8. The calculation means calculates signal strength at both ends of an amplitude of the received radio signal or the received another radio signal during the repetitive motion based on the period; determining a reference distance between a position of the other communication device and a position of the communication device at a reference time based on the signal strength; 8. The communication device according to claim 7, wherein the amount of phase change is calculated based on the movement distance, the movement direction, and the reference distance.

9. 9. The communication device according to claim 7 or 8, characterized in that the communication device comprises a first antenna and a second antenna, and the receiving means receives the radio signal at a first frequency via the first antenna and receives the other radio signal at a second frequency via the second antenna.

10. A communication system comprising a first communication device and a second communication device, The first communication device is a first transmitting means for transmitting a first radio signal including a modulated signal encoded based on a reference clock; and a second transmitting means for transmitting a second wireless signal including a notification signal indicating information on a period of a periodic repetitive motion of the second communication device, the period being determined based on an image of the second communication device captured by an imaging unit, The second communication device is a first receiving means for receiving the first radio signal; a second receiving means for receiving the second radio signal; a measuring means for measuring a moving distance and a moving direction of the second communication device relative to a position of the first communication device; a calculation means for calculating a phase change amount of the received first wireless signal or the second wireless signal due to a fluctuation in characteristics of a wireless transmission path between the first communication device and the second communication device, based on the moving distance, the moving direction, and the notification signal included in the second wireless signal; a determining means for determining a frequency division ratio based on the phase change amount; a frequency division means for regenerating a clock signal by dividing the frequency of the received first radio signal or the received second radio signal in accordance with the frequency division ratio; A communication system comprising:

11. A method for controlling a communication device, comprising: a receiving step of receiving a radio signal including a reference clock signal from another communication device; a measuring step of measuring a moving distance and a moving direction of the communication device relative to a position of the other communication device; a calculation step of calculating a phase change amount of the received wireless signal due to a fluctuation in characteristics of a wireless transmission path between the other communication device and the communication device based on the moving distance and the moving direction; determining a frequency division ratio based on the phase change amount; a frequency dividing step of regenerating a clock signal by dividing the received radio signal in accordance with the frequency division ratio; A control method comprising the steps of:

12. A program for causing a computer to function as the communication device according to claim 1.

Images