JP2007013265A - Wireless communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a wireless communication apparatus to reduce disturbance power and to enhance throughput when another wireless communication system exists in the same area in addition to a wireless communication system including the wireless communication apparatus and transmits/receives data. <P>SOLUTION: The frequency characteristic of a channel selection filter unit for passing a signal with an intermediate frequency fc of 374 MHz after a received signal with a wireless frequency is frequency-converted by a local oscillation signal, is designed symmetrical relative to fc=374 MHz between an adjacent channel band whose center frequency is a lower frequency of fa=354 MHz and an adjacent channel band whose center frequency is a higher frequency of fb=394 MHz in a communication channel band whose center frequency is fc=374 MHz. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus that performs wireless communication with another wireless communication apparatus using a frequency channel selected from a certain frequency band.

  An apparatus as shown in FIG. 8 is considered as a wireless communication apparatus for performing wireless communication between two wireless communication apparatuses in accordance with the IEEE 802.11 standard, for example, in conformity with the IEEE 802.11a standard. It has been.

  In this wireless communication device 51, a MAC (Media Access Controller) 62 is connected to a control unit 61 including a CPU, a ROM, and a RAM, and the modulation / demodulation circuit 63, the first frequency conversion circuit 64, the channel selection filter unit 65, A second frequency conversion circuit 66, a transmission / reception circuit 67, and a transmission / reception antenna 68 are sequentially connected.

  When data is transmitted from the wireless communication device 51 to another wireless communication device, the data to be transmitted is modulated by the modulation / demodulation circuit 63, converted to an intermediate frequency signal by the first frequency conversion circuit 64, and a channel selection filter. The signal is converted into a signal of a frequency channel (radio channel) selected from a predetermined frequency band, for example, 5.2 GHz band by the second frequency conversion circuit 66 through the unit 65, and the other signal is transmitted from the transmission / reception circuit 67 to the other transmission / reception antenna 68. It is transmitted to the wireless communication device.

  When data transmitted from another wireless communication device is received by the wireless communication device 51, a frequency channel (wireless channel) selected from a predetermined frequency band, for example, a 5.2 GHz band, from the other wireless communication device. The data transmitted as the first signal is received by the transmission / reception circuit 67 by the transmission / reception antenna 68, converted to an intermediate frequency signal by the second frequency conversion circuit 66, and passed through the channel selection filter unit 65 by the first frequency conversion circuit 64. The signal is converted into a baseband signal and demodulated by the modem circuit 63.

  The intermediate frequency is set to a predetermined frequency, for example, 374 MHz, and the channel selection filter unit 65 passes a signal in a predetermined bandwidth centered on this frequency, for example, a frequency band of 20 MHz, at the time of transmission and reception, and others. The signal in the frequency band is attenuated.

  In Non-Patent Document 1 below, in the case of “200Ω Balanced” as “Matching Schematics” of such a channel selection filter unit, an inductor (27 nH) is provided on one side of the SAW filter 71 as shown in FIG. It is shown that two capacitors (22 pF) and an inductor (15 nH) are connected to each other on the opposite side, and the frequency characteristic (Frequency Response) of the channel selection filter unit is set to a characteristic as shown in FIG. It is shown.

  The SAW filter is a surface acoustic wave filter, and the reference numeral “71” is added for convenience in this specification.

  The characteristics shown in FIG. 10 are flat in the communication channel band Bc centered on fc = 374 MHz as shown by the characteristic curve 5 in FIG. 11, and adjacent channels centered on fa = 354 MHz on the lower side (low frequency side). The band Ba and the adjacent channel band Bb centered on fb = 394 MHz on the upper side (high frequency side) are asymmetric with respect to fc = 374 MHz.

The prior art documents listed above are as follows.
“SAWTEK Part Number 8556653 374 MHz SAW Filter Data Sheet”, [online], [searched on June 13, 2005], Internet <URL: http://www.triquint.com/company/divisions/sawtek/docs/855653 /855653.pdf>

  However, if the channel selection filter unit 65 of the wireless communication apparatus 51 as shown in FIG. 8 has the characteristics shown in FIGS. 10 and 11, there are the following problems.

  FIG. 12 shows a case where a wireless communication system 55 including wireless communication devices 51 and 52 and a wireless communication system 56 including wireless communication devices 53 and 54 exist in the same area 9. The wireless communication device 53 exists in the vicinity of the wireless communication device 51, the wireless communication devices 52 and 54 exist in the vicinity of the wireless communication devices 51 and 53, respectively, and is wireless between the wireless communication device 51 and the wireless communication device 52. It is assumed that wireless communication is performed between the wireless communication device 53 and the wireless communication device 54 simultaneously with the communication.

  As a radio frequency band that can be used in such a wireless communication system (wireless LAN system), the IEEE802.11a standard defines a 5.2 GHz band as shown in FIG. 6, and the IEEE802.11b standard shows that in FIG. The 2.4 GHz band is specified as shown.

  However, when a plurality of radio channels are set simultaneously in the same area, the frequency interval between adjacent radio channels needs to be 20 MHz or more in the 5.2 GHz band, and adjacent radio channels are used in the 2.4 GHz band. It is necessary to set the frequency interval of 25 MHz or more.

  Therefore, in the 5.2 GHz band, as shown in FIG. 6 as channels C1, C2, C3 or C4, the channel frequency is 5.17 GHz, 5.19 GHz, 5.21 GHz or 5.23 GHz, and in the 2.4 GHz band, As shown in FIG. 7 as channels C11, C12, or C13, the channel frequency is 2.412 GHz, 2.437 GHz, or 2.462 GHz.

  Therefore, in the case of FIG. 12, for example, as shown in the figure, in the wireless communication system 55, the wireless channel is set to 5.19 GHz in the 5.2 GHz band, and the wireless communication apparatus 51 and the wireless communication apparatus 52 are connected. At the same time as performing wireless communication, the wireless communication system 56 performs wireless communication between the wireless communication device 53 and the wireless communication device 54 with the wireless channel set to 5.21 GHz in the 5.2 GHz band. .

  In the wireless communication devices 51, 52, 53, and 54, the respective transmission / reception units (front end units) are configured as shown in FIG. 8, and the respective channel selection filter units 65 are shown in FIG. 10 and FIG. Assume that the frequency characteristics are asymmetric as shown.

  The relationship between the channel frequency fr and the local oscillation frequency fo is set, for example, as fo> fr, that is, fo = fr + fc. Is received by the transmission / reception circuit 67, down-converted by the local frequency signal of the frequency fo by the second frequency conversion circuit 66, and converted to an intermediate frequency signal of fc (= fo−fr = 374 MHz). The signal is converted into a baseband signal by the first frequency conversion circuit 64 through the channel selection filter unit 65 and demodulated by the modulation / demodulation circuit 63.

  In this case, in the wireless communication system 55, the frequency channel of fr2 = 5.19 GHz is selected and data is transmitted from the wireless communication apparatus 51 to the wireless communication apparatus 52. At the same time, in the wireless communication system 56, fr3 = 5.21GHz. Is selected and data is transmitted from the wireless communication device 53 to the wireless communication device 54.

  At this time, the transmission / reception circuit 67 of the wireless communication device 52 receives the fr2 = 5.19 GHz signal from the wireless communication device 51 and the fr3 = 5.21 GHz signal from the wireless communication device 53, and the wireless communication device 52. In the second frequency conversion circuit 66, a signal of fr2 = 5.19 GHz from the wireless communication device 51 is converted into an original signal in the same system by a local signal of fo2 = fr2 + fc = 5.19 GHz + 374 MHz = 5.564 GHz. Although it is converted into a signal having an intermediate frequency of fc = 374 MHz shown in FIG. 11 as being within the communication channel band Bc, the signal of fr3 = 5.21 GHz from the wireless communication device 53 is the same as the local signal of fo2 = 5.564 GHz. As an interference signal from other systems, the lower (low frequency side) adjacent channel band is shown in FIG. It is converted to the frequency of the signals fa = 354MHz, shown as in a.

  On the other hand, the transmission / reception circuit 67 of the wireless communication device 54 receives the fr3 = 5.21 GHz signal from the wireless communication device 53 and the fr2 = 5.19 GHz signal from the wireless communication device 51. In the second frequency conversion circuit 66, the fr3 = 5.21 GHz signal from the wireless communication device 53 is converted into an original signal in the same system by a local signal of fo3 = fr3 + fc = 5.21 GHz + 374 MHz = 5.584 GHz. 11 is converted into a signal having an intermediate frequency of fc = 374 MHz, which is shown as in the communication channel band Bc, but the signal of fr2 = 5.19 GHz from the wireless communication device 51 is the same as the local signal of fo3 = 5.584 GHz, As an interference signal from another system, the upper (high frequency side) adjacent channel band Bb is shown in FIG. It is converted to the frequency of the signal fb = 394MHz shown as.

  Therefore, in the wireless communication device 52, an interference wave signal having a frequency of fa = 354 MHz passes through the channel selection filter unit 65 as shown as the interference wave spectrum Sax in FIG. Produces a disturbance power as shown in FIG. 13A as 5.21 GHz channel interference power Pax on the first frequency conversion circuit 64 side. In the wireless communication device 54, an interference wave signal having a frequency of fb = 394 MHz is As shown as an interference wave spectrum Sbx in FIG. 11, the signal passes through the channel selection filter unit 65 and is output to the output side of the channel selection filter unit 65 (in this case, the first frequency conversion circuit 64 side). The interference power as shown as 19 GHz channel interference power Pbx is generated.

  Moreover, if the frequency characteristics of the channel selection filter unit 65 of the wireless communication devices 52 and 54 are asymmetric as shown in FIGS. 10 and 11, the interference wave spectrum Sax is at a low level and the interference power Pax is reduced. However, the interference wave spectrum Sbx becomes high level, and the interference power Pbx becomes large.

  The code error rate of the data received by the wireless communication device and the throughput between the wireless communication devices are affected by the magnitude of the interference power. The greater the interference power, the higher the code error rate and the lower the throughput. .

  Therefore, in the above example, in the wireless communication device 54 that generates large interference power as the 5.19 GHz channel interference power Pbx, the code error rate of the data received from the wireless communication device 53 becomes high, and the wireless communication devices 53 and 54 In an extreme case, communication between the wireless communication devices 53 and 54 becomes impossible.

  Therefore, the present invention reduces interference power when there is a wireless communication system in addition to the wireless communication system including the wireless communication device in the same area, and data is transmitted / received through adjacent frequency channels. However, the code error rate is reduced, the throughput can be increased, and the wireless communication systems can coexist.

The wireless communication device of the present invention
A modulation / demodulation circuit, a first frequency conversion circuit, a channel selection filter unit, a second frequency conversion circuit, and a transmission / reception circuit, which are sequentially connected,
The channel selection filter unit is characterized in that the characteristics of the lower and upper adjacent channel bands around the predetermined intermediate frequency are symmetrical with respect to the intermediate frequency.

  In the wireless communication device of the present invention configured as described above, when data is received from other wireless communication devices in the wireless communication system including the wireless communication device, wireless communication is performed simultaneously using adjacent wireless channels. Even if a signal from another wireless communication system having a similar configuration is received and interference power is generated in the lower or upper adjacent channel band of the communication channel band, the interference power is reduced to the lower adjacent channel band. And the interference power generated in the upper adjacent channel band are small, the code error rate of the data received from other wireless communication devices in the wireless communication system is reduced, and the adjacent wireless channel is The code error rate of other wireless communication systems with similar configurations that are used for wireless communication also decreases, and the wireless communication systems of each other coexist Kill as to become.

  As described above, according to the present invention, there is a wireless communication system other than the wireless communication system including the wireless communication device in the same area, and data is transmitted and received using adjacent frequency channels. The interference power is reduced, the code error rate is lowered, the throughput can be increased, and the wireless communication systems can coexist.

  FIG. 1 shows an example of a wireless communication apparatus of the present invention.

  In the wireless communication device 11 of this example, a MAC (Media Access Controller) 22 is connected to a control unit 21 including a CPU, a ROM, and a RAM. The MAC 22 is connected to a modulation / demodulation circuit 23, a first frequency conversion circuit 24, and a channel selection filter unit. 25, the second frequency conversion circuit 26, the transmission / reception circuit 27, and the transmission / reception antenna 28 are sequentially connected, and the channel selection filter unit 25 has a configuration and characteristics as described below.

  When data is transmitted from the wireless communication device 11 to another wireless communication device, the data to be transmitted is modulated by the modulation / demodulation circuit 23, converted to an intermediate frequency signal by the first frequency conversion circuit 24, and a channel selection filter. The signal is converted into a signal of a frequency channel (radio channel) selected from a predetermined frequency band, for example, 5.2 GHz band, by the second frequency conversion circuit 26 through the unit 25, and the other signal is transmitted from the transmission / reception circuit 27 to the other transmission / reception antenna 28. It is transmitted to the wireless communication device.

  When data transmitted from another wireless communication device is received by the wireless communication device 11, a frequency channel (wireless channel) selected from a predetermined frequency band, for example, a 5.2 GHz band, from the other wireless communication device. The data transmitted as the first signal is received by the transmission / reception circuit 27 by the transmission / reception antenna 28, converted to an intermediate frequency signal by the second frequency conversion circuit 26, and passed through the channel selection filter unit 25 by the first frequency conversion circuit 24. The signal is converted into a baseband signal and demodulated by the modem circuit 23.

  When the 5.2 GHz band defined by the IEEE802.11a standard is used as the radio frequency band, the frequency channels are 5.17 GHz, 5.19 GHz, 5.21 GHz and 5.23 GHz as shown in FIG. Is selected, and the intermediate frequency is set to fc = 374 MHz.

  The channel selection filter unit 25 allows a signal in a frequency band of 20 MHz width centering on fc = 374 MHz to pass at the time of transmission and reception. Specifically, as shown in FIG. 2, the SAW filter A matching circuit 33 including capacitors 34a and 34b and an inductor 35 is connected to one side of 31 (terminals 32a and 32b connected to the first frequency conversion circuit 24), and the other side (connected to the second frequency conversion circuit 26). It is assumed that a matching circuit 37 including capacitors 38a and 38b and an inductor 39 is connected to the terminals 36a and 36b).

  In addition, by adjusting the capacitance values of the capacitors 34a, 34b, 38a, and 38b and the inductance values of the inductors 35 and 39, the frequency characteristic of the channel selection filter unit 25 is fc = The communication channel band Bc centered on 374 MHz is flat, the adjacent channel band Ba centered on fa = 354 MHz on the lower side (low frequency side), and the adjacent channel band Ba centered on fb = 394 MHz on the upper side (high frequency side). The channel band Bb is symmetric with respect to fc = 374 MHz.

  FIG. 4 shows a case where a wireless communication system 15 including wireless communication devices 11 and 12 and a wireless communication system 16 including wireless communication devices 13 and 14 exist in the same area 9. The wireless communication device 13 exists in the vicinity of the wireless communication device 11, the wireless communication devices 12 and 14 exist in the vicinity of the wireless communication devices 11 and 13, respectively, and the wireless communication device 11 and the wireless communication device 12 are wirelessly connected. It is assumed that wireless communication is performed between the wireless communication device 13 and the wireless communication device 14 simultaneously with the communication.

  In the wireless communication devices 11, 12, 13, and 14, each transmitting / receiving unit (front end unit) has a configuration as shown in FIG. 1, and each channel selection filter unit 25 has the configuration shown in FIG. And a symmetrical frequency characteristic as shown in FIG.

  For example, one of the wireless communication devices 11 and 12 constituting the wireless communication system 15 is configured as a base device that functions as an access point, and the other receives television images and information on the Internet from the base device. Thus, it is configured as a terminal device that performs functions such as displaying video and information on a display and sending and receiving e-mails via a base device. The same applies to the wireless communication devices 13 and 14 constituting the wireless communication system 16.

  For example, assuming that the relationship between the channel frequency fr and the local frequency fo is set to fo> fr, that is, fo = fr + fc, the radio communication apparatuses 11, 12, 13 and 14 each receive a signal of the frequency fr at the time of reception. Is received by the transmission / reception circuit 27, down-converted by the local frequency signal of the frequency fo by the second frequency conversion circuit 26, and converted to an intermediate frequency signal of fc (= fo−fr = 374 MHz). The signal is converted into a baseband signal by the first frequency conversion circuit 24 through the channel selection filter unit 25 and demodulated by the modem circuit 23.

  In this case, in the wireless communication system 15, a frequency channel of fr2 = 5.19 GHz is selected and data is transmitted from the wireless communication apparatus 11 to the wireless communication apparatus 12, and at the same time, in the wireless communication system 16, fr3 = 5.21 GHz. Is selected, and data is transmitted from the wireless communication device 13 to the wireless communication device 14.

  At this time, the transmission / reception circuit 27 of the wireless communication device 12 receives the fr2 = 5.19 GHz signal from the wireless communication device 11 and the fr3 = 5.21 GHz signal from the wireless communication device 13. In the second frequency conversion circuit 26, a signal of fr2 = 5.19 GHz from the wireless communication apparatus 11 is converted into an original signal in the same system by a local signal of fo2 = fr2 + fc = 5.19 GHz + 374 MHz = 5.564 GHz. Although it is converted into a signal having an intermediate frequency of fc = 374 MHz shown in FIG. 3 as being within the communication channel band Bc, the signal of fr3 = 5.21 GHz from the wireless communication device 13 is the same as the local oscillation signal of fo2 = 5.564 GHz. As an interference signal from another system, the adjacent channel band Ba on the lower side (low frequency side) is shown in FIG. It is converted to the frequency of the signals fa = 354MHz shown as.

  On the other hand, the transmission / reception circuit 27 of the wireless communication device 14 receives the fr3 = 5.21 GHz signal from the wireless communication device 13 and the fr2 = 5.19 GHz signal from the wireless communication device 11. In the second frequency conversion circuit 26, the fr3 = 5.21 GHz signal from the wireless communication device 13 is converted into an original signal in the same system by a local signal of fo3 = fr3 + fc = 5.21 GHz + 374 MHz = 5.584 GHz. 3 is converted into a signal of an intermediate frequency of fc = 374 MHz, which is shown as in the communication channel band Bc, but the signal of fr2 = 5.19 GHz from the wireless communication device 11 is the same as the local signal of fo3 = 5.584 GHz, As an interference signal from another system, the adjacent channel band Bb on the upper side (high frequency side) in FIG. It is converted to the frequency of the signal fb = 394MHz showing Te.

  Therefore, in the wireless communication device 12, the interference wave signal having a frequency of fa = 354 MHz passes through the channel selection filter unit 25 as shown as the interference wave spectrum Sa in FIG. Causes interference power as shown as 5.21 GHz channel interference power Pa in FIG. 5A on the first frequency conversion circuit 24 side, that is, between terminals 32a and 32b in FIG. An interference wave signal having a frequency of fb = 394 MHz passes through the channel selection filter unit 25 as shown in FIG. 3 as an interference wave spectrum Sb, and is output from the channel selection filter unit 25 (in this case, the first frequency conversion circuit 24). (Ie, between terminals 32a and 32b in FIG. 2), the 5.19 GHz channel interference power Pb in FIG. Resulting interference power as shown.

  However, the frequency characteristics of the channel selection filter unit 25 of the wireless communication devices 12 and 14 are symmetrical with respect to fc = 374 MHz as shown by the characteristic curve 1 in FIG. 3, and even in the lower adjacent channel band Ba. Since the characteristic is sufficient attenuation even in the upper adjacent channel band Bb, both the interference wave spectrums Sa and Sb are at a low level, and both the interference powers Pa and Pb are small.

  Therefore, in the above example, the code error rate of the data received from the wireless communication device 11 or the wireless communication device 13 in the same system becomes low in both the wireless communication device 12 and the wireless communication device 14. A decrease in throughput between 12 and between the wireless communication devices 13 and 14 is avoided.

  In the above example, the relationship between the channel frequency fr and the local frequency fo is set as fo> fr, that is, fo = fr + fc, but the relationship between the channel frequency fr and the local frequency fo is reversed. The present invention can also be applied to a case where fo <fr, that is, fo = fr−fc, and as described above, the interference power can be reduced, the code error rate can be reduced, and the throughput can be increased. it can.

  In addition, the present invention is particularly suitable when the 5.2 GHz band, which is a narrow frequency interval between adjacent channels of 20 MHz, is used as the radio frequency band, but also when the 2.4 GHz band is used as the radio frequency band. Can be applied.

It is a figure which shows an example of the radio | wireless communication apparatus of this invention. It is a figure which shows an example of a structure of the channel selection filter part of the radio | wireless communication apparatus of FIG. It is a figure which shows the frequency characteristic of the channel selection filter part of FIG. FIG. 3 is a diagram illustrating a state in which a plurality of wireless communication systems using the wireless communication apparatus of FIG. 1 including the channel selection filter unit of FIG. 2 exist in the same area. It is a figure with which it uses for description when transmitting / receiving data simultaneously in each system in the state of FIG. It is a figure which shows the 5.2 GHz band prescribed | regulated by the IEEE802.11a standard. It is a figure which shows the 2.4 GHz band prescribed | regulated by the IEEE802.11b standard. It is a figure which shows the conventional radio | wireless communication apparatus. It is a figure which shows the structure of the channel selection filter part of the radio | wireless communication apparatus of FIG. It is a figure which shows the frequency characteristic of the channel selection filter part of FIG. It is a figure which shows the frequency characteristic of the channel selection filter part of FIG. FIG. 10 is a diagram illustrating a state in which a plurality of wireless communication systems using the wireless communication apparatus of FIG. 8 including the channel selection filter unit of FIG. 9 exist in the same area. It is a figure with which it uses for description when transmitting / receiving data simultaneously in each system in the state of FIG.

Explanation of symbols

  Since all the main parts are described in the figure, they are omitted here.

Claims (3)

A modulation / demodulation circuit, a first frequency conversion circuit, a channel selection filter unit, a second frequency conversion circuit, and a transmission / reception circuit, which are sequentially connected,
The channel selection filter unit is characterized in that the characteristics of the lower and upper adjacent channel bands around the predetermined intermediate frequency are symmetrical with respect to the intermediate frequency. Communication device. In the wireless communication device of claim 1,
The channel selection filter unit includes a filter body, and two matching circuits each including a capacitor and an inductor connected between the filter body and the first frequency conversion circuit and the second frequency conversion circuit. A wireless communication device. The wireless communication device according to claim 2, wherein
The wireless communication apparatus, wherein the filter body is composed of a SAW filter.

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