JP4987998B2 - Wireless communication apparatus, signal detection circuit, and signal detection method - Google Patents

Description

  The present invention relates to a wireless communication device, a signal detection circuit, and a signal detection method. For example, the present invention relates to a method for efficiently using a frequency in a wireless LAN system.

  In the wireless LAN system, the radio wave law regulates radar monitoring. This radar is, for example, a radar used by the Japan Meteorological Agency. When this radar is found in the communication band used by the wireless LAN system, the wireless LAN system needs to change the communication band.

  In a conventional IEEE (Institute of Electrical and Electronics Engineers) 802.11a wireless LAN system, wireless communication is performed using a frequency band of 20 MHz. Therefore, the radar signal may be monitored with respect to the 20 MHz frequency band (see, for example, Patent Document 1).

  However, as a method for increasing the transmission speed in a recent wireless LAN, expansion of the frequency band is being studied in IEEE 802.11n. IEEE 802.11n enables wireless communication in the 40 MHz band in addition to the conventional 20 MHz band. Then, in the conventional radar detection method, the radar can be monitored only for one of the bands. Therefore, if a radar is found, communication must be interrupted or the communication channel must be changed, resulting in a problem that frequency utilization efficiency is lowered.

Japanese Patent Laid-Open No. 2005-210616

  The present invention provides a wireless communication device, a signal detection circuit, and a signal detection method that can improve frequency utilization efficiency.

  A wireless communication apparatus according to an aspect of the present invention includes a first frequency band that is a first communication channel, and a second frequency band that includes the first communication channel and a second communication channel adjacent to the first communication channel; A wireless communication apparatus capable of communicating using the first and second interference bands in the first frequency band and the second frequency band, and detecting the interference signal in the first frequency band. An interference signal detector that outputs a detection signal and outputs a second detection signal when the interference signal is detected in the second frequency band, and the interference based on the first detection signal and the second detection signal An interference signal determination unit that determines whether a signal is present in the first communication channel or the second communication channel, and the interference signal determination unit receives the second detection signal from the interference signal detection unit. If the output and the first detection signal is not output, it is determined that the interference signal exists in the second frequency channel.

  The signal detection circuit according to one aspect of the present invention includes a frequency converter that converts the frequency of an input signal, which is a digital signal, using an oscillation signal having a predetermined oscillation frequency, and a cutoff equal to the oscillation frequency. A filter having a frequency and extracting a part of the input signal having the frequency converted by the frequency converter; a measuring unit for measuring the intensity of the input signal extracted by the filter; and the measurement And a determination unit that determines presence / absence of a pulse signal in the input signal based on a measurement result in the unit.

  Still further, in the signal detection method according to one aspect of the present invention, interference signals are detected for the first and second antennas that transmit and receive radio signals and the signals received by the first antenna and the second antenna. 4. A signal detection method for a wireless communication apparatus comprising the signal detection circuit according to claim 2, wherein the frequency conversion unit provided in the signal detection circuit converts a radio signal received by the first antenna. The conversion frequency to be converted is different from the conversion frequency converted by the frequency conversion unit for the radio signal received by the second antenna.

  According to the present invention, it is possible to provide a radio communication device, a signal detection circuit, and a signal detection method that can improve frequency utilization efficiency.

1 is a block diagram of a wireless LAN system according to a first embodiment of the present invention. The band figure shown about the frequency band which the wireless LAN system which concerns on 1st Embodiment of this invention uses. The block diagram showing an example of the radio | wireless communication apparatus which concerns on 1st Embodiment of this invention. The block diagram of the receiving part which the radio | wireless communication apparatus which concerns on 1st Embodiment of this invention has. The graph which shows the frequency band which can be used in the wireless LAN system which concerns on 1st Embodiment of this invention. The conceptual diagram of the information memorize | stored in the channel information storage part which the radio | wireless communication apparatus which concerns on 1st Embodiment of this invention has. 3 is a flowchart showing the operation of the wireless communication apparatus according to the first embodiment of the present invention. The block diagram of the radio | wireless communication apparatus which concerns on 2nd Embodiment of this invention. The block diagram of the receiving part which the radio | wireless communication apparatus which concerns on 2nd Embodiment of this invention has. The flowchart of operation | movement of the radio | wireless communication apparatus which concerns on 2nd Embodiment of this invention. The flowchart of operation | movement of the radio | wireless communication apparatus which concerns on 3rd Embodiment of this invention. The block diagram of the radio | wireless communication apparatus which concerns on 4th Embodiment of this invention. The block diagram of the receiving part which the radio | wireless communication apparatus which concerns on 4th Embodiment of this invention has. The block diagram of the radar detection part which the radio | wireless communication apparatus concerning 4th Embodiment of this invention has. The block diagram of the frequency conversion part which the radio | wireless communication apparatus concerning 4th Embodiment of this invention has. The wave form diagram of the sine wave output from the oscillation part which the radio | wireless communication apparatus concerning 4th Embodiment of this invention has. It is the wave form diagram of the signal in the frequency conversion part of the radio | wireless communication apparatus which concerns on 4th Embodiment of this invention, (a) A figure is a wave form figure of a digital signal, (b) A figure is a frequency spectrum of an oscillation signal. It is the waveform diagram of the signal in the frequency conversion part of the radio | wireless communication apparatus which concerns on 4th Embodiment of this invention, (a) A figure is a waveform diagram of a digital signal, (b) A figure is a frequency spectrum of an oscillation signal, (c The figure shows the result of multiplication in the complex multiplier. It is the waveform diagram of the signal in the frequency conversion part of the radio | wireless communication apparatus which concerns on 4th Embodiment of this invention, (a) A figure is a waveform diagram of a digital signal, (b) A figure is a frequency spectrum of an oscillation signal, (c The figure shows the result of multiplication in the complex multiplier. The graph which shows the frequency characteristic of the band-limiting filter with which the radio | wireless communication apparatus which concerns on 4th Embodiment of this invention is provided. In the radio | wireless communication apparatus which concerns on 4th Embodiment of this invention, it is a graph which shows the multiplication result in a complex multiplication part, and the frequency characteristic of a band-limiting filter, (a) FIG. The figure shows the case where the second communication channel is passed. The graph which shows the time change of the signal strength input into the pulse property determination part with which the radio | wireless communication apparatus which concerns on 4th Embodiment of this invention is provided. The flowchart of operation | movement of the radio | wireless communication apparatus which concerns on 4th Embodiment of this invention. The block diagram of the radar detection part which the radio | wireless communication apparatus concerning 5th Embodiment of this invention has. The graph which shows the frequency characteristic of the band-limiting filter part which concerns on 5th Embodiment of this invention. The flowchart of operation | movement of the radio | wireless communication apparatus which concerns on 5th Embodiment of this invention. The block diagram of the radio | wireless communication apparatus which concerns on 6th Embodiment of this invention. The flowchart of operation | movement of the radio | wireless communication apparatus which concerns on 6th Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In this description, common parts are denoted by common reference numerals throughout the drawings.

[First embodiment]
A wireless communication device, a signal detection circuit, and a signal detection method according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a conceptual diagram of a wireless LAN system according to this embodiment, and shows a wireless LAN system according to the IEEE 802.11 standard.

  As shown in the figure, the wireless LAN system according to the present embodiment includes a wireless base station 101 and wireless terminal stations 102 and 103, and wireless communication is performed between them. A unit composed of the wireless base station 101 and at least one wireless terminal station is called BSS (Basic Service Set) in the IEEE 802.11 standard. Although FIG. 1 shows a case where there are two wireless terminal stations included in the BSS, the number of wireless terminal stations is not particularly limited. Further, the wireless terminal stations 102 and 103 may include a plurality of antennas capable of transmitting and receiving data streams. Further, the BSS may include a radio base station 101 having a plurality of antennas and a radio terminal station 103 having a single antenna. Further, the number of antennas mounted on the wireless base station 101 and the wireless terminal stations 102 and 103 may be one or a plurality may be mounted depending on the communication method in the wireless LAN system.

  FIG. 2 is a band diagram showing frequency bands used in the wireless LAN system according to the present embodiment. As shown in the figure, the wireless LAN system uses a first frequency band and a second frequency band that overlap each other. The first frequency band has a bandwidth of 20 MHz from a [MHz] to (a + 20) [MHz]. Hereinafter, a band corresponding to the first frequency band is referred to as a first communication channel. The second frequency band has a bandwidth of 40 MHz from a [MHz] to (a + 40) [MHz]. Hereinafter, a band between (a + 20) [MHz] and (a + 40) [MHz] is referred to as a second communication channel.

  That is, the second frequency band includes a first communication channel and a second communication channel adjacent to the first communication channel. In the conventional IEEE802.11a standard or the like, only wireless communication in the first frequency band is possible, but in the IEEE802.11n standard, wireless communication using not only the first frequency band but also the second frequency band is possible. It is said.

  Further, a bandwidth of 20 MHz from a [MHz] to (a + 20) [MHz] is defined as the second communication channel, and a bandwidth between (a + 20) [MHz] and (a + 40) [MHz] is defined as the first communication channel. It may be defined. Furthermore, in the present embodiment, a case where the bandwidth of the first frequency band is 20 MHz and the bandwidth of the second frequency band is 40 MHz is described as an example, but this is only an example. For example, the bandwidth of the first frequency band may be 40 MHz, and the bandwidth of the second frequency band may be 80 MHz.

  The radio base station 101 according to the present embodiment includes a radio communication device for realizing the above-described radio communication. FIG. 3 is a block diagram of a wireless communication apparatus included in the wireless base station 101.

  As shown in the figure, the radio communication apparatus 200 includes an antenna 201, a radio unit 202, a reception unit 203, a transmission / reception data processing unit 204, a transmission unit 205, a first radar detection unit 206, a second radar detection unit 207, and a radar detection determination unit 208. A frequency switching unit 209 and a channel information storage unit 210.

  The antenna 201 receives radio signals (RF signals: analog signals) transmitted from the radio terminal stations 102 and 103 in the BSS, and transmits radio signals to the radio terminal stations 102 and 103.

  When performing wireless communication in the second frequency band (40 MHz), the wireless unit 202 operates to receive and transmit a wireless signal having a 40 MHz bandwidth in accordance with a command from the frequency switching unit 209. Further, when performing wireless communication in the first frequency band (20 MHz), it operates to receive and transmit a signal in the 20 MHz band in accordance with a command from the frequency switching unit 209. When receiving the wireless signal, the wireless unit 202 down-converts the 5 GHz band wireless signal received by the antenna 201 into a baseband signal and supplies the baseband signal to the receiving unit 203. At the time of transmission, the baseband signal given from the transmission unit 203 is up-converted into a radio signal of 5 GHz band and transmitted from the antenna 201.

  The receiving unit 203 converts the baseband signal given from the wireless unit 202 from an analog signal to a digital signal when receiving the wireless signal. Further, the baseband signal converted into the digital signal is demodulated, and the demodulated signal obtained as a result is supplied to the transmission / reception data processing unit 204. Further, the baseband signal converted into the digital signal is supplied to the first radar detection unit 206 and the second radar detection unit 207.

  Details of the reception unit 203 will be described with reference to FIG. FIG. 4 is a block diagram of the receiving unit 203. As shown in the figure, the receiving unit 203 includes an A / D conversion unit (hereinafter referred to as an ADC unit) 203a, filter units 203b and 203c, a selection unit 203d, and a demodulation unit 203e.

  The ADC unit 203a converts the baseband signal given from the radio unit 202 from an analog signal to a digital signal. The ADC unit 203a supplies a radio signal converted into a digital signal (hereinafter sometimes simply referred to as a digital signal) to the filter units 203b and 203c.

  The filter unit 203b passes only the 20 MHz band signal among the digital signals supplied from the ADC unit 203a, and the filter unit 203c passes only the 40 MHz band signal. The digital signals that have passed through the filter units 203b and 203c are given to the first and second radar detection units 203b and 203c, respectively. Both of them are given to the selection unit 203d.

  The selection unit 203d supplies the output of the filter unit 203b to the demodulation unit 203e during wireless communication using the first frequency band, and outputs the output of the filter unit 203c to the demodulation unit 203e during wireless communication using the second frequency band. Supply. Which output of the filter units 203b and 203c is selected is determined by, for example, an instruction from the demodulation unit 203e.

  The demodulator 203e performs a demodulation process defined by the wireless LAN system of the IEEE 802.11 standard on the digital signal supplied from the selector 203d. For example, orthogonal frequency division multiplexing (OFDM) demodulation and error correction decoding are performed to obtain a baseband received signal. Then, the obtained baseband received signal is supplied to the transmission / reception data processing unit 204.

  Returning to FIG. 3, the description will be continued. The transmission / reception data processing unit 204 performs baseband processing on the transmission / reception data. For example, when a radio signal is received, a MAC (Media Access Control) header is removed from the baseband received signal received from the receiving unit 203 and a packet is assembled. A packet is transmission / reception data assembled in a data structure that can be handled by a personal computer or the like. Conversely, when transmitting, a frame is assembled by adding a MAC header to the data to be transmitted. A frame is transmission / reception data assembled so as to be communicable by wireless communication. Then, the frame is output to the transmission unit 205.

  The transmission unit 205 performs modulation processing specified by the wireless LAN system of the IEEE 802.11 standard on the frame received from the transmission / reception data processing unit. For example, OFDM modulation and error correction coding are performed to obtain a baseband signal. Further, the baseband signal is converted from a digital signal to an analog signal, and the obtained analog signal is supplied to the wireless unit 202.

  The first radar detection unit 206 detects the radar in the 20 MHz band for the digital signal given from the filter unit 203b of the reception unit 203. Then, the detection result is output to the radar detection determination unit 208. That is, it is detected whether or not a radar is present in the first communication channel. When the radar is detected, the first detection signal is output to the radar detection determination unit 208.

  The second radar detection unit 207 detects a radar in the 40 MHz band for the radio signal given from the filter unit 203c of the reception unit 203. Then, the detection result is output to the radar detection determination unit 208. When the radar is detected, the second detection signal is output to the radar detection determination unit 208. Accordingly, the first radar detection unit 206 can detect the presence / absence of a radar in the first frequency band (20 MHz), and the second radar detection unit 207 can detect the presence / absence of a radar in the second frequency band (40 MHz).

  The radar detection determination unit 208 determines whether the radar is present in the first communication channel or the second communication channel based on the output signals of the first radar detection unit 206 and the second radar detection unit 207. As a result of this determination, when a radar is detected in the currently used frequency band, the radar detection determination unit 208 determines that a change in the frequency band for communication or a change in the communication channel is necessary. Radar detection determination unit 208 then outputs a frequency change instruction signal to frequency switching unit 209. Further, the radar detection determination unit 208 instructs the transmission / reception data processing unit 204 to stop data transmission.

  The frequency switching unit 209 changes the frequency band or the communication channel in response to the frequency change instruction signal given from the radar detection determination unit 208. When the change is made, the wireless unit 202 is notified of the change. The change of the frequency band and communication channel in the frequency switching unit 209 is performed according to information in the channel information storage unit 210. That is, the frequency switching unit 209 instructs the wireless unit 202 to switch to a new communication channel by setting the channel information acquired from the channel information storage unit 210 in the wireless unit 202. For example, when a radar is found in the 40 MHz band during communication and the communication is changed to the 20 MHz band, the frequency switching unit 209 notifies the radio unit 202 to that effect. Then, the setting of the wireless unit 202 is changed so that the wireless unit 202 can communicate in the 20 MHz band. As a result, the radio unit 202 switches from an operation of receiving a 40 MHz band signal to an operation of receiving a 20 MHz band signal.

  When the wireless unit 202 switches operation, the wireless unit 202 notifies the frequency switching unit 209 that the switching has been completed. When the notification is accepted, the frequency switching unit 209 notifies the transmission / reception data processing unit 204 of the change of the communication channel or the change of the frequency bandwidth. Thus, the transmission / reception data processing unit 204 can perform data transmission processing after recognizing the frequency bandwidth currently occupied by the BSS.

  The channel information storage unit 210 stores a plurality of pieces of communication channel information within a frequency band that can be used in the wireless LAN system. In the wireless LAN system according to the IEEE 802.11 standard, there are a plurality of usable frequency bands, and a plurality of communication channels exist in each band. The wireless LAN system in the present embodiment can perform communication by selecting an available channel from the plurality of communication channels.

  FIG. 5 is a conceptual diagram showing frequency bands that can be used in the wireless LAN system according to the present embodiment, and particularly shows frequency bands that require radar detection. Usually, frequency bands that can be used in a wireless LAN system are a band from 5.15 GHz to 5.25 GHz, a band from 5.25 GHz to 5.35 GHz, and a band from 5.47 GHz to 5.725 GHz. Among these frequency bands, a communication channel in the band from 5.25 GHz to 5.35 GHz and a communication channel in the band from 5.47 GHz to 5.725 GHz have large transmission power and can be used outdoors. Accordingly, since this band may interfere with the radar, it is necessary to detect the radar when using these bands. In these bands, the communication channel can be used only when a communication channel without a radar is selected.

  FIG. 6 is a conceptual diagram of channel information stored in the channel information storage unit 210. The channel information storage unit 210 holds information CH-a to CH-o regarding communication channels that can be used in the wireless LAN system according to the present embodiment. These communication channels are communication channels that can be selected from frequency bands that can be used in the Radio Law.

  In the present embodiment, frequencies from 5.25 GHz to 5.35 GHz and 5.47 GHz to 5.725 GHz shown in FIG. 5 can be used, and the channel information storage unit 210 acquires channel information from this frequency area. . As an example, the bandwidth of each communication channel is 20 MHz as described with reference to FIG. Accordingly, there are five communication channels available from 5.25 GHz to 5.35 GHz. That is, the 5.25 to 5.27 GHz band, the 5.27 to 5.29 GHz band, and the 5.33 to 5.35 GHz band are communication channels, respectively. In addition, there are 12 communication channels available from 5.47 GHz to 5.725 GHz. That is, the 5.47 to 5.49 GHz band, the 5.49 to 5.51 GHz band, and the 5.69 to 5.71 GHz band are communication channels, respectively.

  Therefore, when performing communication using the first frequency band, communication in the 20 MHz band is performed using any one of the communication channels as the first communication channel (see FIG. 2). On the other hand, when performing communication using the second frequency band, communication in the 40 MHz band is performed using the two adjacent communication channels. At this time, of the two communication channels, the communication channel on the low frequency side becomes the first communication channel, and the communication channel on the high frequency side becomes the second communication channel. The channel information storage unit 210 holds information regarding each communication channel in the 20 MHz band as information CH-a to CH-o.

  The communication channel selection method is not limited to the above, and the communication channel on the low frequency side may be the second communication channel and the communication channel on the high frequency side may be the first communication channel.

  The frequency switching unit 209 controls the radio unit 202 and the transmission / reception data processing unit 204 using the information CH-a to CH-o. Further, when changing the communication channel, the frequency switching unit 209 may select the communication channel at random or may preferentially select from the high-frequency communication channel. Alternatively, when each communication channel is numbered as the first, second, and third channels, an even channel or an odd channel may be selected. The communication channel selection method can be selected as appropriate, such as using a specific algorithm.

  Next, details of operations from radar detection to frequency switching in the wireless communication apparatus 200 having the above-described configuration will be described with reference to FIG. FIG. 7 is a flowchart showing an operation flow of the wireless communication apparatus 200.

  First, it is assumed that the wireless communication apparatus 200 performs communication using the second frequency band (40 MHz band) using a certain communication channel. A radar detection determination unit 208 in the wireless communication apparatus 200 of the wireless base station 101 monitors detection signals from the first radar detection unit 206 and the second radar detection unit 207. When radar is detected by the first radar detection unit 206 and / or the second radar detection unit 207 (step S0), the radar detection determination unit 208 instructs the transmission / reception data processing unit 204 to stop transmission. In response to this, the transmission / reception data processing unit 204 stops transmission (S1). Subsequently, the radar detection determination unit 208 confirms the first detection signal and the second detection signal output from the first radar detection unit 206 and the second radar detection unit 207 (S2).

  Hereinafter, for the first detection signal and the second detection signal, a case where the signal is output is expressed as “1”, and a case where the signal is not output is expressed as “0”. A combination of detection results of the first and second detection signals is indicated by (0, 1), (1, 0), (1, 1).

First, the case where the detection result in the radar detection determination unit 208 is (first detection signal, second detection signal) = (0, 1) (S3, {0, 1}) will be described. This case corresponds to a case where radar is not detected in the first frequency band and radar is detected in the second frequency band. Then, the radar detection determination unit 208 determines that radar is present in the second communication channel (S4). In this case, communication using the second communication channel cannot be continued. That is, communication using the second frequency band including the second communication channel is impossible. However, since there is no radar in the first communication channel, communication using only the first communication channel (that is, using the 20 MHz band) is possible.

  For example, in FIG. 6, a channel (CH-a) in the band of 5.25 to 5.27 GHz is the first communication channel, and a communication channel (CH-b) in the band of 5.27 to 5.29 GHz is the second communication channel. Suppose that 40 MHz band communication is performed. (First detection signal, second detection signal) = (0, 1) means that the radar is detected in the second communication channel in the band of 5.27 to 5.29 GHz. Therefore, in this case, the communication is switched to communication using only the first communication channel in the band of 5.25 to 5.27 GHz (20 MHz band communication) or switched to another communication channel to perform 40 MHz band communication. The meaning of switching to another communication channel means that another communication channel that does not use the band of 5.25 to 5.29 GHz is used. For example, 40 MHz band communication is performed using a 5.29 to 5.33 GHz band. In this case, the communication channel in the 5.29 to 5.31 GHz band is used as the first communication channel, and the communication channel in the 5.31 to 5.33 GHz band is used as the second communication channel.

  Therefore, the radar detection determination unit 208 determines whether to switch the currently used communication channel to a communication channel of another frequency band (S5).

  When switching to another communication channel (S5, YES), the radar detection determination unit 208 commands the radio unit 202 and the transmission / reception data processing unit 204 to that effect. For example, when the 5.29 to 5.33 GHz band is used, information CH-c and CH-d are read from the channel information storage unit 210, and the radio unit 202 is set based on this information. As a result, the wireless communication apparatus resumes communication in the 40 MHz band using a different communication channel (S6).

  When switching to another communication channel is not performed (S5, NO), the radar detection determination unit 208 changes the frequency band to be used from the second frequency band to the first frequency band, and performs wireless communication only with the first communication channel. Is determined to resume (S7). Next, the frequency switching unit 209 sends a frequency band change notification to the transmission / reception data processing unit 204 and the radio unit 202. As a result, the radio base station 101 resumes communication using only the first frequency channel (S8).

  Next, a case where the detection result in the radar detection determination unit 208 is (first detection signal, second detection signal) = (1, 0) (S3, {1, 0}) will be described. This case corresponds to a case where radar is detected in the first frequency band and no radar is detected in the second frequency band. Such a case should not occur as long as the wireless communication apparatus 200 operates normally, but exists as a combination of detection results, and there is no case where such a detection result is obtained for some reason. Is not limited. Therefore, in this embodiment, a measure for the case of (first detection signal, second detection signal) = (1, 0) is also prepared.

  In this case, the radar detection determination unit 208 determines that the radar exists only in the first communication channel (S9). Therefore, communication using the first communication channel cannot be continued. That is, communication using the second frequency band including the first communication channel is not possible. Of course, unlike the case of step S7, communication with the frequency band changed to 20 MHz is also impossible. Accordingly, the radar detection determination unit 208 resumes 40 MHz band communication using a communication channel different from the first communication channel (step S10). This process is the same as step S6 described above.

  Next, a case where the detection result in the radar detection determination unit 208 is (first detection signal, second detection signal) = (1, 1) (S3, {1, 1}) will be described. This case corresponds to a case where radar is detected in the first frequency band and radar is also detected in the second frequency band. In this case, the radar detection determination unit 208 determines that the radar is detected only in the first communication channel or in both the first communication channel and the second communication channel (S11).

  According to the detection result in this case, it cannot be specified whether the radar is present in the first communication channel or the second communication channel. Therefore, the radar detection determination unit 208 stops using both the first communication channel and the second communication channel.

  Therefore, the radar detection determination unit 208 switches to a communication channel having a frequency different from that of the first and second communication channels (S12). That is, as described above, the channel (CH-a) in the 5.25 to 5.27 GHz band is the first communication channel, and the communication channel (CH-b) in the 5.27 to 5.29 GHz band is the second communication channel. Assuming that 40 MHz band communication is performed. When (first detection signal, second detection signal) = (1, 1), use of two communication channels included in 5.25 to 5.29 GHz is prohibited. Therefore, the radar detection determination unit 208 performs 40 MHz band communication using another communication channel, for example, a 5.29 to 5.33 GHz band.

  Further, in the determination of step S0, when radar is not detected by both the first and second radar detection units 206 and 207 (that is, (first detection signal, second detection signal) = (0, 0). Corresponding), wireless communication is continued without changing the frequency channel or frequency band (S13).

As described above, the wireless communication device, the signal detection circuit, and the signal detection method according to the present embodiment can achieve the following effect (1).
(1) The communication frequency can be used efficiently (part 1).
In the conventional IEEE802.11a standard, for example, the bandwidth of the frequency band used for wireless communication is 20 MHz. Therefore, it was sufficient to monitor the radar in the 20 MHz band.

  However, in the IEEE 802.11n standard, communication is performed not only in the 20 MHz band but also in the 40 MHz band. Then, for example, when the radar is monitored only in the 40 MHz band, the communication channel must be changed even if the radar is present only in the first communication channel. Therefore, there is a problem that the use efficiency of the communication frequency is lowered and the operation speed is lowered due to the communication channel changing process.

  However, the wireless communication apparatus 200 according to the present embodiment includes the first radar detection unit 206 that monitors the radar in the 20 MHz band and the second radar detection unit 207 that monitors the radar in the 40 MHz band. Therefore, the radar detection determination unit 208 can grasp that the radar exists only in the second communication channel. That is, if the radar is not detected by the first radar detection unit 206 and the radar is detected by the second radar detection unit 207, it can be grasped that the radar exists only in the second communication channel in this case. In this case, since 20 MHz band communication using only the first communication channel is possible, the frequency utilization efficiency is improved. In addition, when performing 20 MHz band communication using only the first channel, it is not necessary to change the communication channel, and thus it is possible to prevent a decrease in the operating speed of the wireless communication apparatus 200.

[Second Embodiment]
Next, a radio communication device, a signal detection circuit, and a signal detection method according to a second embodiment of the invention will be described. In the present embodiment, two radar detection units are combined into one in the first embodiment. FIG. 8 is a block diagram of the wireless communication apparatus according to the present embodiment.

  As shown in the figure, the radio communication apparatus 200 according to the present embodiment eliminates the first and second radar detection units 206 and 207 in the configuration of FIG. 3 described in the first embodiment, and provides one radar detection unit. 212, and the receiving unit 203 is replaced with the receiving unit 211. Since other configurations are the same as those in the first embodiment, description thereof will be omitted.

  FIG. 9 is a block diagram of the receiving unit 211. As shown in the figure, the reception unit 211 has a configuration in which the filter units 203b and 203c and the selection unit 203d are eliminated and the filter unit 203f is newly provided in the configuration of FIG. 4 described in the first embodiment. .

  The filter unit 203f passes a signal in the 20 MHz band or the 40 MHz band in the digital signal supplied from the ADC unit 203a in accordance with a command from the radar detection unit 212. That is, the filter unit 203f is a filter having a variable pass band. Then, the digital signal that has passed through the filter unit 203f is provided to the demodulation unit 203e and the radar detection unit 212. When the wireless communication apparatus 200 performs wireless communication using the first frequency band (20 MHz), the filter unit 203f passes only a signal in the 20 MHz band. On the other hand, when wireless communication is performed using the second frequency band (40 MHz), a 20 MHz band signal or a 40 MHz band signal is passed.

  The filter unit 203f passes a filter that passes the second frequency band (40 MHz), a filter that passes the first frequency band (20 MHz) corresponding to the first communication channel, and 20 MHz that corresponds to the second communication channel. Including filters. Any one of the filters is made effective by a command from the radar detection unit 212. Hereinafter, the state in which the filter unit 203f is operating to pass a frequency component with a bandwidth of 40 MHz is referred to as a second frequency band mode, and the state is operating to pass a frequency component with a bandwidth of 20 MHz. Is referred to as a first frequency band mode. Also, in the first frequency band mode, a state in which the band corresponding to the first communication channel is operating is called a first channel mode, and the band corresponding to the second communication channel is allowed to pass. This state is referred to as a second channel mode.

  The radar detection unit 212 detects a radar for the digital signal given from the reception unit 211. Then, the detection result is output to the radar detection determination unit 208. The radar detection unit 212 outputs a first detection signal when the radar is detected when the filter unit 203f is in the first frequency band mode. On the other hand, when the radar is detected in the second frequency band mode, a second detection signal is output. Further, when performing communication in the second frequency band, the radar detection unit 212 instructs the filter unit 203f to pass only the 20 MHz band when radar is detected in the 40 MHz band.

  Next, details of operations from radar detection to frequency switching in the wireless communication apparatus 200 having the above configuration will be described with reference to FIG. FIG. 10 is a flowchart showing an operation flow of the wireless communication apparatus 200.

  First, in the wireless communication device 200, the filter unit 203f operates in the second frequency band mode before determining a frequency band to be used, that is, before determining a communication channel for performing wireless communication or during wireless communication. (S20).

  Accordingly, the radar detection unit 212 detects a radar in the second frequency band. The radar detection determination unit 208 monitors the detection signal from the radar detection unit 212. When the radar detection unit 212 detects a radar (step S21, YES), the radar detection determination unit 208 instructs the transmission / reception data processing unit 204 to stop transmission. In response to this, the transmission / reception data processing unit 204 stops transmission (S22).

  Next, when the radar detection determination unit 208 determines that a radar signal has been detected within the second frequency band, the radar detection unit 212 switches to the filter unit 203f so as to switch from the second frequency band mode to the first channel mode. Give instructions. In response to this instruction, the filter unit 203f switches to the first channel mode (S23).

  The radar detection unit 212 sets the radar observation time TO1 in the timer held by itself, and performs radar detection only during the period of TO1 (S24). The reason for providing the timer is as follows. That is, the radar is a pulse signal that is continuously given at a certain period. Therefore, if the radar observation time is too short, a non-radar pulse signal may be erroneously recognized as a radar. Further, for example, erroneous detection obtained by thermal noise is also conceivable. Therefore, the radar detection unit 212 sets the radar observation time TO1 in advance, and if there is a pulse signal that is continuously given at a constant period during this period, the radar detection unit 212 determines that it is a radar. The radar observation time TO1 is, for example, about 30 to 70 [msec].

  When the radar is detected in the first channel mode (S25, YES), the radar detection determination unit 208 determines that the radar is detected only in the first communication channel or in both the first communication channel and the second communication channel. (S26). Accordingly, the radar detection determination unit 208 switches to a communication channel having a frequency different from that of the first and second communication channels (S27). The processes in steps S26 and S27 correspond to steps S11 and S12 described in the first embodiment.

  The radar detection is continued until the radar observation time TO1 elapses (S25, NO, S28, NO). If no radar is detected even after TO1 has elapsed (S28, YES), the radar detector 212 determines that no radar has been detected (S29). In response to this result, the radar detection determination unit 208 determines that radar is present in the second communication channel (S30). Accordingly, the radar detection determination unit 208 determines whether or not to switch the currently used communication channel to a communication channel in another frequency band (S31).

  When switching to another communication channel (S31, YES), the radar detection determination unit 208 commands the radio unit 202 and the transmission / reception data processing unit 204 to that effect. As a result, the wireless communication apparatus resumes communication in the 40 MHz band using a different communication channel (S32). When not switching to another communication channel (S31, NO), the radar detection determination unit 208 changes the frequency band to be used from the second frequency band to the first frequency band, and performs wireless communication only with the first communication channel. Is determined to resume (S33). As a result, the wireless communication apparatus 200 resumes communication using only the first frequency channel (S34).

  The processes in steps S30 to S34 described above correspond to steps S4 to S8 described in the first embodiment.

  If it is determined in step S21 that the radar signal is not detected by the radar detector 212, wireless communication is continued without changing the frequency channel (S35).

  Next, the case where the filter unit 203f operates in the first frequency band mode in step S20 will be described. In this case, the wireless communication apparatus performs communication using only the first communication channel. The radar detection unit 212 detects the presence or absence of radar in the first frequency band (S36).

  When the radar detection unit 212 detects a radar (S36, YES), the radar detection determination unit 208 instructs the transmission / reception data processing unit 204 to stop transmission. In response to this, the transmission / reception data processing unit 204 stops transmission (S37). The radar detection / determination unit 208 recognizes the presence of radar in the first communication channel (S38), and switches to a different communication channel (S39). If the radar is not detected in the determination in step S36 (S36, NO), the wireless communication is continued (S35).

As described above, in the wireless communication device, signal detection circuit, and signal detection method according to the second embodiment of the present invention, in addition to the effect of (1) described in the first embodiment, The effect (2) can also be obtained.
(2) The circuit scale of the wireless communication device can be reduced (part 1).
In the configuration according to the present embodiment, the filter unit 203f functions as a 40 MHz band pass filter (second frequency band mode) and also functions as a 20 MHz band pass filter (first frequency band mode). When detecting radar in the 40 MHz band, the filter unit 203f operates in the second frequency band mode. When detecting a radar in the 20 MHz band, the filter unit 203f operates in the first frequency band mode. Therefore, the radar detection similar to that in the first embodiment can be performed by one radar detection unit 212. As a result, the circuit scale of the wireless communication device 200 can be reduced as compared with the first embodiment.

[Third embodiment]
Next, a radio communication device, a signal detection circuit, and a signal detection method according to a third embodiment of the invention are described. In this embodiment, radar detection is further performed in the second communication channel in the second embodiment.

  Since the configuration of the wireless communication apparatus 200 according to the present embodiment is the same as that of FIGS. 8 and 9 described in the second embodiment, description thereof is omitted. However, unlike the second embodiment, when the radar detection unit 212 detects a radar within the second frequency band, the radar detection unit 212 shifts not only to the first channel mode but also to the second channel mode with respect to the filter unit 203f. Command.

  Next, details of operations from radar detection to frequency switching in the radio communication apparatus 200 having the above configuration will be described with reference to FIG. FIG. 11 is a flowchart showing an operation flow of the wireless communication apparatus 200.

  First, the operations in steps S20 to S25 described in the second embodiment are performed. Since these operations are the same as those described in the second embodiment, a description thereof will be omitted. In addition, the operations in steps S36 to S39 when the first frequency band mode is set in step S20 and the operation in step S35 when NO is determined in step S21 are the same as those in the second embodiment. Omitted.

  In step S25, when a radar is detected (step S25, YES), the radar detection unit 212 outputs a first detection signal. Furthermore, the radar detection unit 212 outputs a command for transition from the first channel mode to the second channel mode to the filter unit 203f (S40). As a result, the filter unit 203f shifts to the second channel mode and passes the first frequency band (20 MHz) corresponding to the second channel. Thereafter, the radar detector 212 sets the radar observation time TO1 in the timer (S41), and monitors the radar signal (S42).

  When the radar is detected in the second channel mode (step S42, YES), the radar detection unit 212 outputs the first detection signal again. In response to this result, the radar detection determination unit 208 determines that radar is present in both the first communication channel and the second communication channel (S43). Accordingly, the radar detection determination unit 208 switches to a communication channel having a frequency different from that of the first and second communication channels (S44). The processes in steps S43 and S44 correspond to steps S11 and S12 described in the first embodiment.

  The radar detection in step S42 is continued until the radar observation time TO1 elapses (S42, NO, S45, NO). If no radar is detected even after TO1 has elapsed (S45, YES), the radar detector 212 determines that no radar has been detected (S46). In response to this result, the radar detection determination unit 208 determines that the radar exists only in the first communication channel (S47). Accordingly, the radar detection determination unit 208 switches the currently used communication channel to a communication channel in another frequency band (S48).

  If no radar is detected in step S25 (step S25, NO, step S49, YES), the radar detector 212 does not output the first detection signal. Further, the radar detection unit 212 outputs a transition command from the first channel mode to the second channel mode to the filter unit 203f (S50). As a result, the filter unit 203f shifts to the second channel mode and passes the first frequency band (20 MHz) corresponding to the second channel. Thereafter, the radar detector 212 sets the radar observation time TO1 in the timer (S51), and monitors the radar signal (S52).

  When the radar is detected in the second channel mode (step S42, YES), the radar detection unit 212 outputs the first detection signal again. In response to this result, the radar detection determination unit 208 determines that the radar exists only in the second communication channel (S53). Therefore, the radar detection determination unit 208 determines whether or not to switch the currently used communication channel to a communication channel in another frequency band (S54).

  When switching to another communication channel (S54, YES), the radar detection determination unit 208 commands the radio unit 202 and the transmission / reception data processing unit 204 to that effect. As a result, the wireless communication apparatus resumes communication in the 40 MHz band using a different communication channel (S55). When switching to another communication channel is not performed (S54, NO), the radar detection determination unit 208 changes the frequency band to be used from the second frequency band to the first frequency band, and performs wireless communication using only the first communication channel. Is determined to resume (S56). As a result, the wireless communication apparatus 200 resumes communication using only the first frequency channel (S57). The processes in steps S54 to S57 correspond to steps S30 to S34 described in the second embodiment.

  The radar detection in step S52 is continued until the radar observation time TO1 has elapsed (S52, NO, S58, NO). If no radar is detected even after TO1 has elapsed (S58, YES), the radar detector 212 determines that no radar has been detected (S46). In this case, this corresponds to the fact that no radar is detected in either the first communication channel or the second communication channel. However, since it is determined in step S21 that the radar exists, the radar detection determination unit respects this determination and determines that the radar exists in the first communication channel and the second communication channel (step S59). Accordingly, the radar detection determination unit 208 determines whether or not to switch the currently used communication channel to a communication channel in another frequency band (S60).

As described above, the wireless communication device, the signal detection circuit, and the signal detection method according to this embodiment have the effects (1) and (2) described in the first and second embodiments. The following effect (3) can be obtained.
(3) Accurate radar detection is possible.
In the wireless communication apparatus according to the present embodiment, when the radar is detected when the filter unit 203f is in the second frequency band mode, the filter unit 203f is set not only in the first channel mode but also in the second channel mode. Detection is performed.

  That is, the radar is first detected in the 40 MHz band, then the radar is detected in the 20 MHz band (first communication channel) on the low frequency side in the 40 MHz band, and then the 20 MHz band (second communication channel) on the higher frequency side. The radar is detected by Therefore, more accurate radar detection is possible with the same configuration as in the second embodiment.

[Fourth Embodiment]
Next, a radio communication device, a signal detection circuit, and a signal detection method according to a fourth embodiment of the invention are described. In the present embodiment, in the second or third embodiment, the filter is provided in the radar detection unit, thereby eliminating the filter from the reception unit 213.

  FIG. 12 is a block diagram of the wireless communication apparatus 200 according to the present embodiment. As shown in the figure, the basic configuration is the same as in the second and third embodiments. However, in the present embodiment, since the internal configurations of the receiving unit and the radar detecting unit are different from those of the second and third embodiments, they are hereinafter referred to as the receiving unit 213 and the radar detecting unit 214.

  FIG. 13 is a block diagram of the receiving unit 213 according to the present embodiment. As shown in the figure, the receiving unit 213 according to the present embodiment has a configuration in which the filter unit 203f is omitted from the configuration of FIG. 9 described in the second embodiment. Therefore, the digital signal output from the ADC unit 203 a is directly input to the radar detection unit 214. The baseband signal is separated into a real part and an imaginary part by being converted into a digital signal by the ADC unit 203a.

  FIG. 14 is a block diagram of the radar detection unit 214 according to the present embodiment. As illustrated, the radar detection unit 214 includes a frequency conversion unit 214a, a band limiting filter unit 214b, a signal intensity measurement unit 214c, and a pulse property determination unit 214d.

  The frequency conversion unit 214a performs frequency conversion on the digital signal supplied from the ADC unit 203a. More specifically, the frequency of the digital signal is shifted by a predetermined value in the plus direction and the minus direction. The band limiting filter unit 214b passes only some components of the digital signal whose frequency is converted by the frequency conversion unit 214a, and outputs it to the signal strength measurement unit 214c. The signal strength measuring unit 214c measures the strength of the digital signal given from the ADC unit 203a and the digital signal passed through the band limiting filter unit 214b. Further, the pulse property determination unit 214d determines the presence / absence of a pulse signal, that is, the presence / absence of a radar, based on the measurement result of the signal intensity measurement unit 214c.

  FIG. 15 is a block diagram showing an internal configuration of the frequency converter 214a. As shown in the figure, the frequency conversion unit 214 a includes an oscillation unit 216 and a complex multiplication unit 217. The oscillating unit 216 generates an oscillation signal having a predetermined oscillation frequency f1. The real part of this oscillation signal is called a real part 215c, and the imaginary part is called an imaginary part 215d.

  The complex multiplier 217 multiplies the real part 215a and imaginary part 215b of the digital signal by the real part 215c and imaginary part 215d of the oscillation signal output from the oscillator 216. As a result, the frequency of the digital signal is converted.

Next, details of the operation of the radar detection unit 214 configured as described above will be described.
First, the frequency converter 214a will be described. The oscillation frequency f1 of the oscillation signal output from the oscillation unit 216 described with reference to FIG. 15 is, for example, ± 10 MHz. That is, the frequency of the digital signal given from the ADC unit 203a is shifted by 10 MHz in the plus direction or shifted by 10 MHz in the minus direction. In the oscillation unit 216, the oscillation signal is sampled at a sampling frequency f2 = 40 MHz, for example. Then, the oscillation signal sampled by f2 is given to the complex multiplier 217. It should be noted that the relationship between the oscillation frequency f1 and the sampling frequency may be such that the ratio of the absolute values of the two is one power of 2, that is, | f1 | / | f2 | = 1 / ²ⁿ (where n is Natural number). Thereby, only the values of “0”, “1”, and “−1” among the sine waves indicating the imaginary part 215 d of the oscillation signal are output from the oscillation unit 216. This is shown in FIG. FIG. 16 is a waveform diagram of the imaginary part 215d of the oscillation signal. As shown in the figure, the frequency of the sine wave is 10 MHz, and as a result of the sampling frequency being 40 MHz, four values (“0”, “1”, “0”, “−1”) per cycle are obtained. Output from the oscillator 216.

  Then, the real part 215a and the imaginary part 215b of the digital signal are multiplied by the real part 215c and the imaginary part 215d of the oscillation signal in the complex multiplier 217. As a result, the frequency of the digital signal is shifted by ± 10 MHz. Frequency conversion will be described with reference to FIGS. 17A and 17B, FIGS. 18A to 18C, and FIGS. 19A to 19C. FIG. 17A is a graph showing the frequency distribution of the digital signal, and FIG. 17B is a graph showing the frequency spectrum of the oscillation frequency of the oscillation signal. FIGS. 18A and 19A are graphs showing the frequency distribution of the digital signal, and FIGS. 18B and 19B are graphs showing the frequency spectrum of the oscillation frequency of the oscillation signal. FIG. 18B and FIG. 19C are graphs showing the frequency distribution of the multiplication result in the complex multiplier 217. Note that FIGS. 17A to 19A show the case where the bandwidth of the digital signal is 40 MHz, but this is for the sake of simplification of description, and the digital signal has a wider band than 40 MHz. There may be, and it is normal.

  First, it is assumed that a digital signal as shown in FIG. 17A is input to the complex multiplier 217. That is, the bandwidth is 40 MHz, 20 MHz on the low frequency side corresponds to the first communication channel, and 20 MHz on the high frequency side corresponds to the second communication channel. The center frequency of the digital signal corresponds to the boundary portion between the first communication channel and the second communication channel. The oscillation frequency f1 of the oscillation signal generated by the oscillation unit 216 is +10 MHz and −10 MHz as shown in FIG. 17B, and can be selected as appropriate.

  First, the case where the oscillation frequency f1 is +10 MHz will be described with reference to FIGS. By performing complex multiplication of the oscillation signal whose oscillation frequency f1 is +10 MHz and the digital signal, the frequency of the digital signal is shifted by +10 MHz as shown in FIG. That is, the first communication channel is located between −10 MHz and +10 MHz.

  Next, the case where the oscillation frequency f1 is −10 MHz will be described with reference to FIGS. By performing complex multiplication of an oscillation signal having an oscillation frequency f1 of −10 MHz and a digital signal, the frequency of the digital signal is shifted by −10 MHz as shown in FIG. That is, the second communication channel is located between −10 MHz and +10 MHz.

  The digital signals shown in FIGS. 18C and 19C obtained by the frequency conversion as described above are supplied to the band limiting filter unit 214b. In the above description, the case where the frequency is shifted by ± 10 MHz by setting the oscillation frequency f1 to ± 10 MHz has been described. However, as long as the relationship with the sampling frequency is a value that is a power of two, it is not limited to ± 10 MHz, and may be ± 20 MHz, for example. In this case, the frequency shift amount is also ± 20 MHz.

  Next, details of the band limiting filter unit 214b will be described. FIG. 20 is a graph showing the frequency characteristics of the band limiting filter unit 214b, in which the horizontal axis represents frequency and the vertical axis represents signal transmittance. In FIG. 20, only the positive region is shown for the sake of simplicity, but similar characteristics exist on the negative side. As shown in the figure, the band limiting filter unit 214b is a low-pass filter having an absolute value of the cutoff frequency of 10 MHz and the same value as the oscillation frequency f1. Further, the absolute value of the cutoff frequency is not limited to 10 MHz as long as it is the same value as the oscillation frequency. Further, the band limiting filter unit 214b according to the present embodiment is a low-pass filter using a roll-off filter.

  Therefore, only the component of ± 10 MHz from the center frequency is extracted from the center frequency of the digital signal frequency-converted by the frequency converting unit 214a by the band limiting filter unit 214b. This will be described with reference to FIGS. 21 (a) and 21 (b). FIGS. 21A and 21B are graphs showing the frequency-converted digital signal and the frequency band passed through the band limiting filter unit 214b. FIG. 21A shows the oscillation frequency f1 of the oscillation unit 216. FIG. In the case of +10 MHz, (b) shows the case of -10 MHz.

  First, as shown in FIG. 21A, when the oscillation frequency f1 is +10 MHz and the frequency of the digital signal is shifted by +10 MHz, the center frequency of the digital signal is between −10 MHz and +10 MHz as described above. To -20 MHz, ie the first communication channel is located. Accordingly, the band limiting filter unit 214b passes only the frequency component corresponding to the first communication channel in the digital signal.

  As shown in FIG. 21B, when the oscillation frequency f1 is set to -10 MHz and the frequency of the digital signal is shifted by -10 MHz, the digital signal is between -10 MHz and +10 MHz as described above. A component between the center frequency and +20 MHz, that is, the second communication channel is located. Accordingly, the band limiting filter unit 214b passes only the frequency component corresponding to the second communication channel in the digital signal.

Next, the signal strength measuring unit 214c will be described. The digital signal that has passed through the band limiting filter unit 214b or the digital signal that is directly given from the ADC unit 203a of the receiving unit 214 is input to the signal strength measuring unit 214c, and the strength thereof is measured. The signal strength measuring unit 214c measures the signal strength of the digital signal by performing the following calculation.
Σ (I ² + Q ² )
Where I is the real part of the digital signal and Q is the imaginary part.

  Next, the pulse determination unit 214d will be described. The pulse property determination unit 214d determines whether or not the digital signal has a pulse property based on the intensity measured by the signal intensity measurement unit 214c. And when it determines with having a pulse property, it determines that the said digital signal contains a radar. An example of a method for determining whether or not a pulse has is described with reference to FIG. FIG. 22 is a graph showing the time change of the intensity of the digital signal.

  For example, focusing on the signal intensity I1, when I1 is 10 dB or more larger than the signal intensity I2 3 μs before the observation time of I1 and 10 dB or more larger than the intensity I3 10 μs after the observation time of I1, Judge that there is sex.

  Next, the details of the radar detection method in radio communication apparatus 200 having the above configuration will be described with reference to FIG. FIG. 23 is a flowchart showing an operation flow of the wireless communication apparatus 200.

  First, the signal strength measuring unit 214c takes in a digital signal directly given from the ADC unit 203a of the receiving unit 213. And the intensity | strength of the taken-in digital signal is measured, and the pulse property determination part 214d determines the presence or absence of a radar based on the intensity | strength (S70). In the configuration according to the present embodiment, unlike the first to third embodiments, no filter is provided in the reception unit 213. Accordingly, in step S70, radar detection is performed in the entire frequency band of the digital signal.

  As a result of step S70, when the pulse property determination unit 214d determines that there is no radar (S71, YES), communication is continued (S72). On the other hand, if it is determined in step S70 that the radar is present (S71, YES), the signal intensity measuring unit 214c takes in the digital signal provided from the band limiting filter unit 214b (S73). Then, first, radar detection in the first communication channel is performed on the digital signal given from the band limiting filter unit 214b.

  That is, the oscillation frequency f1 of the oscillation unit 216 in the frequency conversion unit 214a is set to +10 MHz (S74). Then, the complex multiplication unit 217 performs complex multiplication of the oscillation signal and the digital signal to shift the frequency of the digital signal by +10 MHz (S75). The processes in steps S74 and S75 are as described with reference to FIGS.

  The band limiting filter unit 214b passes only the frequency component corresponding to the first communication channel in the frequency-converted digital signal (S76). The process in step S76 is as described with reference to FIG. Then, the signal intensity measuring unit 214c sets the radar observation time TO1 as a timer, and measures the intensity of the digital signal output from the band limiting filter unit 214b only during the period of TO1. That is, the intensity of the frequency component corresponding to the first communication channel is measured (S77).

  At this time, if the wireless communication apparatus 200 is performing communication in the 20 MHz band (S78, NO), the second stage is determined when the radar is determined by the pulse determining unit 214d (S79, YES). The process proceeds to step S37 described in the embodiment. That is, the communication is changed to a communication using another communication channel. On the other hand, if it is determined that there is no radar (S79, NO), the process proceeds to step S72 and communication is continued.

  When the wireless communication apparatus 200 is communicating in the 40 MHz band (S78, YES), the radar detection unit 214 next performs radar detection in the second communication channel.

  That is, the oscillation frequency f1 of the oscillation unit 216 in the frequency conversion unit 214a is set to −10 MHz (S80). Then, the complex multiplier 217 performs complex multiplication of the oscillation signal and the digital signal to shift the frequency of the digital signal by −10 MHz (S81). The processing in steps S74 and S75 is as described with reference to FIGS. 19 (a) to 19 (c).

  The band limiting filter 214b passes only the frequency component corresponding to the second communication channel in the frequency-converted digital signal (S82). The process in step S82 is as described with reference to FIG. Then, the signal intensity measuring unit 214c sets the radar observation time TO1 as a timer, and measures the intensity of the digital signal output from the band limiting filter unit 214b only during the period of TO1. That is, the intensity of the frequency component corresponding to the second communication channel is measured (S83).

  The radar detection determination unit 207 transmits / receives a transmission stop when radar is present in at least one of the communication channels, that is, when it is determined that radar is present in at least one of steps S77 and S83 (YES in S84). The data processing unit is commanded (S85). Thereafter, the process proceeds to step S3 described in the first embodiment. In the present embodiment, the first detection signal = “1” in step S3 corresponds to the case where it is determined that the radar is present in the first communication channel (step S77). The second detection signal = "1" corresponds to the case where it is determined that the radar is present on the second communication channel (step S83).

  If it is determined in step S84 that no radar is present, the process proceeds to step S59 described in the third embodiment.

As described above, the following effects (4) to (7) can be obtained with the wireless communication apparatus, signal detection circuit, and signal detection method according to the present embodiment.
(4) The communication frequency can be used efficiently (part 1).
In the wireless communication apparatus 200 according to the present embodiment, in the wireless communication apparatus 200 that can communicate in both the 20 MHz band and the 40 MHz band, the radar detection unit 214 detects the radar in units of 20 MHz band. More specifically, the digital signal is limited to the 20 MHz band by the band limiting filter unit 214b having a 20 MHz (± 10 MHz) pass band to detect the radar. Therefore, when a radar is detected, it can be determined whether the radar is present in the first communication channel or the second communication channel. Therefore, similarly to the effect (1) described in the first embodiment, the frequency utilization efficiency is improved. In addition, when performing 20 MHz band communication using only the first channel, it is not necessary to change the communication channel, and thus it is possible to prevent a decrease in the operating speed of the wireless communication apparatus 200.

(5) The characteristics of the radar detector 214 can be improved.
In the present embodiment, the baseband received signal is converted from an analog signal to a digital signal by the ADC unit 213 a provided in the receiving unit 213. And it is detected whether the radar exists in this digital signal.

  In this regard, if an attempt is made to detect a radar from an analog signal, the circuit configuration and operation of a circuit for detection by the radar will be more complicated than when a digital signal is used. This is because, when an analog signal is used, the complex frequency calculation is performed in the RF circuit to change the center frequency and its pass band, and narrow down the frequency channel in which the radar exists. As a result, processing takes a long time compared to the case of a digital circuit.

  On the other hand, by using a digital signal, a radio signal is separated into a real part and an imaginary part, and complex calculation becomes easy. The frequency conversion only needs to be multiplied by the oscillation signal output from the oscillating unit 216, so that the processing time can be increased and the accuracy can be improved. Therefore, the characteristics of the radar detector can be improved.

(6) The circuit scale of the wireless communication device can be reduced (part 2).
In the present embodiment, the oscillation frequency f1 and the sampling frequency f2 of the oscillation signal in the oscillator 216 are designed to satisfy the relationship of | f1 | / | f2 | = 1 / ²ⁿ . For example, f1 = ± 10 MHz and f2 = 40 MHz. As a result, the value of the sampling point in the imaginary part of the oscillation signal is simplified to “0”, “+1”, “−1”.

  Therefore, the configuration of the oscillation unit 216 can be simplified, and the circuit scale of the wireless communication apparatus 200 can be reduced. Further, simplifying the value at the sampling point in this way also leads to an increase in the operation speed of the frequency conversion unit 214a.

  Note that, as described above, the oscillation frequency f1 and the sampling frequency f2 need only have a power-of-two relationship, so that, for example, f1 = ± 20 MHz and f2 = 40 MHz may be used. In this case, the value at the sampling point is only “0”.

(7) The circuit scale of the wireless communication device can be reduced (part 3).
In the configuration according to the present embodiment, the cut-off frequency (± 10 MHz) of the band limiting filter unit 214b is made equal to the oscillation frequency f1 in the oscillation unit 216. Therefore, the configuration of the band limiting filter unit 214b can be simplified, and the circuit scale of the wireless communication device 200 can be reduced.

  Further, as described in (5) above, the radar detection unit 214 can be reduced by detecting the radar from the digital signal. In other words, when an analog signal is used, the calculation for separating a radio signal into a positive frequency component and a negative frequency component becomes complicated, and a complex arithmetic unit is essential. For this reason, the circuit scale becomes larger than necessary. However, in the present embodiment, a digital signal is used to change the center frequency thereof, so that a static digital filter may be used for the band limiting filter unit 214b, and the circuit configuration can be simplified.

  Furthermore, in this embodiment, a static roll-off filter can be used as the band limiting filter unit 214b by using a digital signal. By using this roll-off filter, the impulse response is set so as not to be infinite. For this reason, “0” periodically exists in the filter coefficient (tap weight) constituting the band limiting filter unit 214b. Therefore, the amount of calculation in the band limiting filter unit 214b can be reduced, and the band limiting filter unit 214b can be reduced.

[Fifth Embodiment]
Next explained is a wireless communication device, signal detection circuit and signal detection method according to the fifth embodiment of the invention. In the fourth embodiment, a band-limiting filter unit 214 is further provided in the radar detection unit before the frequency conversion unit 214a in the fourth embodiment. FIG. 24 is a block diagram of the radar detection unit 214 according to the present embodiment.

  As shown in the figure, the radar detection unit 214 according to the present embodiment further includes a band limiting filter unit 214e in the configuration of FIG. 14 described in the fourth embodiment. The frequency band that the band limiting filter unit 214e passes is wider than the frequency band that the band limiting filter unit 214b passes, for example, 40 MHz.

  The frequency conversion unit 214a performs frequency conversion on the digital signal that has passed through the band limiting filter unit 214e. Further, the signal strength measuring unit 214c measures the strength of the digital signal that has passed through the band limiting filter units 214b and 214e.

Since other configurations are the same as those of the fourth embodiment, description thereof is omitted.
FIG. 25 is a graph showing the frequency characteristics of the band limiting filter units 214b and 214e. The horizontal axis shows the frequency and the vertical axis shows the signal transmittance. In FIG. 25, only the positive region is shown for simplification, but similar characteristics exist on the negative side. As shown in the figure, the band limiting filter unit 214b has an absolute value of the cut-off frequency of 10 MHz, which is the same as in the fourth embodiment. On the other hand, the absolute value of the cutoff frequency of the band limiting filter unit 214e is, for example, 20 MHz.

  Next, details of the radar detection method in the wireless communication apparatus 200 according to the present embodiment will be described with reference to FIG. FIG. 26 is a flowchart showing an operation flow of the wireless communication apparatus 200.

  As shown in the figure, first, the band limiting filter unit 214e passes only a frequency component of 40 MHz (± 20 MHz) in the digital signal supplied from the ADC unit 203a of the receiving unit 213 (step S90).

  Next, the signal strength measuring unit 214c captures the digital signal that has passed through the band limiting filter unit 214e. And the intensity | strength of the taken-in digital signal is measured, and the pulse property determination part 214d determines the presence or absence of a radar based on the intensity | strength (S91). That is, radar detection in the second frequency band that has passed through the band limiting filter unit 214e is performed.

  As a result of step S91, when the pulse property determination unit 214d determines that there is no radar (S71, YES), communication is continued (S72). On the other hand, if it is determined in step S91 that the radar is present (S71, YES), the radar detection determination unit 208 instructs the transmission / reception data processing unit 204 to stop transmission (step S92). Thereafter, the process proceeds to step S73 described in the fourth embodiment, and processing similar to that in the fourth embodiment is performed (see FIG. 23). However, step S85 in FIG. 23 is not necessary. This is because this process is completed in step S92.

As described above, the wireless communication apparatus 200 according to the fifth embodiment of the present invention has the following (8) in addition to the effects (4) to (7) described in the fourth embodiment. An effect is obtained.
(8) Radar detection efficiency can be improved.
In the configuration according to the present embodiment, the band limiting filter unit 214e having a wider band than the band limiting filter unit 214b is provided in the previous stage of the frequency conversion unit 214b. Therefore, the frequency band to be detected by the signal intensity measuring unit 214c and the pulse property determining unit 214d in step S91 is narrower than that in the fourth embodiment. Therefore, if it is determined in step S91 that the radar is present, the possibility that the radar is present in the currently used frequency band is increased.

  For example, as described in the above embodiment, if the pass band of the band limiting filter 214e is 40 MHz equal to the second frequency band, the 40 MHz band communication is performed at the moment when the radar is determined to be present in step S91. Will have a radar in the frequency band currently in use. In other words, when radar is present in a frequency band other than the currently used frequency band, it is not necessary to perform the processing after step S92. Therefore, the radar detection efficiency is improved. In addition, the frequency of performing unnecessary radar detection processing in the radar detection unit 214 can be reduced.

  Note that the band limiting filter unit 214e only needs to have a bandwidth of at least 40 MHz, and may have a pass band including another adjacent frequency channel, for example.

[Sixth Embodiment]
Next, a radio communication device, a signal detection circuit, and a signal detection method according to a sixth embodiment of the invention are described. In this embodiment, a plurality of radar detection units according to the fifth embodiment are provided. FIG. 27 is a block diagram of the wireless communication apparatus 200 according to the present embodiment.

  As illustrated, the wireless communication apparatus 200 according to the present embodiment includes three radar detection units 214-1 to 214-3 in the configuration of FIG. 12 described in the fourth embodiment. In addition, the wireless communication device 200 includes three antennas 201-1 to 201-3 corresponding to the radar detection units 214-1 to 214-3. That is, the radio signals received by the antennas 201-1 to 201-3 are supplied to the radar detection units 214-1 to 214-3 via the reception unit 213, respectively.

  Each of the radar detection units 214-1 to 214-3 has the configuration of FIG. 24 described in the fifth embodiment. The radar detection unit 214-1 performs radar detection in the first communication channel, and the radar detection unit 214-2 performs radar detection in the second communication channel. The radar detector 214-3 is provided as a spare. Since the basic operation of the wireless communication apparatus 200 according to the present embodiment is the same as that of the fourth and fifth embodiments, only differences from the fourth and fifth embodiments will be described below.

  Next, the operation of the radar detectors 214-1 and 214-2 in the above configuration will be described with reference to FIG. FIG. 28 is a flowchart of the radar detection operation in each of the radar detection units 214-1 and 214-2.

  As shown in the drawing, in each of the radar detection units 214-1 and 214-2, the processes of steps S 90, S 91, S 71, S 92, and S 73 described in the fifth embodiment are sequentially executed.

  After step S73, the oscillation frequencies f1 of the oscillator 216 of the frequency converter 214a in each of the radar detectors 214-1 and 214-2 are set to +10 MHz and −10 MHz, respectively (S93). Then, the complex multiplier 217 in each of the radar detectors 214-1 and 214-2 performs complex multiplication of the oscillation signal and the digital signal, and shifts the frequency of the digital signal by +10 MHz and −10 MHz, respectively (S94). The processes in steps S93 and S94 are as described with reference to FIGS. 18 (a) to 18 (c) and FIGS. 19 (a) to 19 (c).

Further, the band limiting filter 214b in each of the radar detectors 214-1, 214-2 passes only the frequency components corresponding to the first communication channel and the second communication channel, respectively, of the frequency-converted digital signal. (S95). The process in step S95 is as described with reference to FIGS. 21 (a) and 21 (b). Then, the signal intensity measurement unit 214c in each of the radar detection units 214-1 and 214-2 sets the radar observation time TO1 as a timer, and the digital signal output from the band limiting filter unit 214b only during the period of TO1. Measure strength. That is, the cardiac intensity measuring unit 214c in each of the radar detecting units 214-1 and 214-2 measures the intensity of frequency components corresponding to the first communication channel and the second communication channel, respectively (S96).
Thereafter, the process proceeds to step S78 as in the fifth embodiment.

As described above, in the wireless communication device, the signal detection circuit, and the signal detection method according to the present embodiment, in addition to the effects (4) to (8) described in the fourth and fifth embodiments, The following effect (9) can be obtained.
(9) The circuit scale of the wireless communication device can be reduced (part 3).
In the wireless communication apparatus 200 according to the present embodiment, radar detection units 214-1 to 214-3 are provided for each of the plurality of antennas 201-1 to 201-3. Radar detection in the radio signals received by the antennas 201-1 to 201-3 is performed by the radar detection units 214-1 to 214-3, respectively. At this time, the configuration of the radar detection units 214-1 to 214-3 is the configuration shown in FIG. 24 described in the fifth embodiment, and the frequency band in which the radar detection units 214-1 to 214-3 should detect the radar. Is controlled by the frequency converter 214a.

  More specifically, for example, by setting the oscillation frequency f1 of the oscillation unit 216 in the radar detection unit 214-1 to +10 MHz, the radar detection unit 214-1 detects the radar in a range of −20 MHz from the center frequency of the digital signal. . Further, by setting the oscillation frequency f1 of the oscillation unit 216 in the radar detection unit 214-2 to −10 MHz, the radar detection unit 214-1 detects a radar in a range of +20 MHz from the center frequency of the digital signal.

  As described above, since the circuit configuration of each of the radar detection units 214-1 to 214-3 can be made common, even when a plurality of antennas are provided, the circuit scale of the entire wireless communication apparatus 200 can be reduced. .

  In addition, it becomes possible to reduce the power consumption of the radio | wireless communication apparatus 200 by making the unnecessary radar detection part 214-3 into an operation | movement stop state among the some radar detection parts 214-1 to 214-3. In the sixth embodiment, the case where the number of antennas and radar detection units is three has been described. Of course, the number is not limited to this.

  As described above, in the wireless communication device, the signal detection circuit, and the signal detection method according to the first to sixth embodiments of the present invention, the first communication channel and the second communication adjacent to the first communication channel. When performing wireless communication using the second frequency band 9, not only the presence / absence of radar in the first communication channel but also the presence / absence of radar in the second communication channel can be detected. When the radar is present only in the two channels, it is not necessary to change the communication channel by shifting to the wireless communication using only the first communication channel. The operating speed of the communication device can be improved.

  In the first to sixth embodiments, the case where the radar is detected during execution of wireless communication has been described as an example. However, the radar may be detected before the start of wireless communication. In this case, radar is detected before selecting a communication channel, and a communication channel in which no radar is present is grasped in advance. When starting wireless communication, a communication channel in which no radar is present is selected.

  Further, when the radio base station 101 shifts to a new communication channel, the radio base station 101 may notify the radio terminal stations 102 and 103 in the BSS to that effect. In this case, the radio base station 101 transmits predetermined data to the radio terminal stations 102 and 103 before switching the communication channel.

  Further, each block in the first to sixth embodiments may be realized as hardware of an analog or digital circuit, or may be realized by software executed by a CPU.

  In the first to sixth embodiments, the example in which the communication channel is changed when the radar is detected or the frequency band is narrowed from the 40 MHz band to the 20 MHz band has been described. However, the response method when the radar is detected is not limited to the above embodiment. That is, for example, after switching to another communication channel by the frequency switching unit 209, whether to start communication with a 20 MHz bandwidth or to start communication with a 40 MHz bandwidth, the radar detects the new occupied frequency bandwidth. There is no problem if the frequency band is different. That is, which bandwidth to select may be determined by an algorithm implemented by the radio base station 101.

  In the first to sixth embodiments, the first frequency bandwidth is defined as 20 MHz and the second frequency bandwidth is defined as 40 MHz. However, the bandwidth is not limited to this. That is, a combination in which the first frequency bandwidth is 20 MHz and the second frequency bandwidth is 80 MHz, or a combination in which the first frequency bandwidth is 40 MHz and the second frequency bandwidth is 80 MHz may be used.

  In the sixth embodiment, the case where the radar detectors 214-1 to 214-3 have the configuration of FIG. 24 described in the fifth embodiment has been described as an example. However, you may have the structure of FIG. 14 demonstrated in 4th Embodiment. In this case, the process of step S92 in FIG. 28 is performed after it is determined in step S84 that the radar is present (step S84, YES).

Further, the radar detection unit 214 in the fourth and fifth embodiments is not limited to the configuration for radar detection in the wireless communication device. That is, the present invention can also be applied as a signal detection circuit that detects a pulse signal in a certain frequency band. Even in such a case, by using a digital signal as the input signal, the configuration of the frequency conversion unit and the band limiting filter unit can be simplified, and the detection speed and detection accuracy of the pulse signal can be improved.

  Furthermore, in the above embodiment, the case where the radar is detected has been described as an example. However, the above embodiment can be applied not only to the radar defined by the Radio Law but also to the detection of general interference signals that interfere with communication.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention in the implementation stage. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be extracted as an invention.

  DESCRIPTION OF SYMBOLS 101 ... Wireless base station, 102 ... Wireless terminal station, 103 ... Wireless terminal station, 201, 201-1 to 201-3 ... Antenna, 202 ... Wireless part, 203, 211, 213 ... Reception part, 203a, 213a ... A / D conversion unit, 203b, 203c, 203f ... filter unit, 203d ... selection unit, 203e, 203e, 213b ... demodulation unit, 204 ... transmission / reception data processing unit, 205 ... transmission unit, 206,207,212,214,214-1 ˜214-3. Radar detection unit, 208. Radar detection determination unit, 209. Frequency switching unit, 210. Channel information storage unit, 203a. ADC unit, 214a. Frequency conversion unit, 214b, 214e, band-limiting filter unit, 214c. ... Signal intensity measurement unit, 214d ... pulse property determination unit, 215a, 215c ... real number part, 215b, 215d ... imaginary number part, 2 6 ... oscillation unit, 217 ... complex multiplier

Claims (4)

A wireless communication device capable of communicating using a first frequency band serving as a first communication channel and a second frequency band including the first communication channel and a second communication channel adjacent to the first communication channel. ,
A receiver that receives a radio signal and converts the received radio signal from an analog signal to a digital signal;
An interference signal detection unit for detecting an interference signal in the first communication channel and the second communication channel for the radio signal converted into the digital signal by the reception unit, the interference signal detection unit, A frequency converter that converts the frequency of the radio signal converted into the digital signal in the receiver using an oscillation signal having a predetermined oscillation frequency;
A frequency component corresponding to the first communication channel by extracting a part of the radio signal having the cut-off frequency equal to the oscillation frequency and having the frequency converted by the frequency converter, or the second A filter unit that passes a frequency component corresponding to the communication channel;
A measurement unit for measuring the intensity of the frequency component of the radio signal passed through the filter unit;
A wireless communication apparatus comprising: a determination unit that determines presence / absence of the interference signal based on a measurement result in the measurement unit. A frequency converter that converts the frequency of the input signal, which is a digital signal, using an oscillation signal having a predetermined oscillation frequency;
A filter unit having a cutoff frequency equal to the oscillation frequency, and extracting a part of the input signal having the frequency converted by the frequency conversion unit;
A measuring unit for measuring the intensity of the input signal extracted in the filter unit;
A signal detection circuit comprising: a determination unit that determines presence / absence of a pulse signal in the input signal based on a measurement result in the measurement unit. The signal detection circuit according to claim 2, wherein the value of the oscillation frequency is a power of 2 of the frequency of the input signal. A radio comprising: first and second antennas for transmitting and receiving radio signals; and a signal detection circuit according to claim 2 or 3 for detecting interference signals for signals received by the first antenna and the second antenna. A signal detection method for a communication device, comprising:
The conversion frequency converted by the frequency conversion unit provided in the signal detection circuit for the radio signal received by the first antenna is the conversion frequency converted by the frequency conversion unit for the radio signal received by the second antenna. A signal detection method characterized by being different.

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