JP5157642B2 - Wireless receiver - Google Patents

Description

  The present invention relates to a function of notifying a user by detecting a reception state of radio waves, and more particularly, to a wireless reception device having a function of detecting a situation in which a radio wave reception state deteriorates due to the influence of multipath fading and notifying the user. .

  In the field of wireless communication technology used in offices and homes in recent years, for example, wireless LAN (Local Area Network) communication based on IEEE (Institute of Electronic and Electronics Engineers) 802.11 standard, wireless USB (Universal Serial Bus) ) Wireless PAN (Personal Area Network) communication based on the standard has been put into practical use, and various products are put on the market.

  In such wireless communication, it is important to transmit radio waves while suppressing multipath fading. Multipath fading means that radio waves radiated from a wireless transmission device are reflected, diffracted, or scattered by an obstacle and reach the wireless reception device through various paths, and are synthesized by the antenna of the reception device. It is a phenomenon that radio waves cause interference.

  Conventionally, when communication is performed in a wireless communication device, the wireless communication device measures the received signal strength and indicates it to the user, and the user checks the display to confirm that the strength is equal to or higher than a predetermined strength, or performs communication. Communication was performed by changing the receiving location so that it would be stronger.

  That is, the conventional wireless communication apparatus indicates a radio wave reception state using only the received signal strength as a criterion, and determines that the radio wave reception state is good if the received signal strength is sufficient. However, in practice, due to the influence of multipath fading, the radio wave reception state may not be good even though the received signal strength is sufficient.

  Therefore, as a conventional technique for detecting the influence of multipath fading and presenting it to a user, there is a wireless communication apparatus that determines the degree of radio wave interference due to multipath fading based on the received signal strength and packet error rate of a received packet ( For example, see Patent Document 1).

In addition, there is a wireless communication apparatus that detects the amplitude and phase of a plurality of pilot signals and determines that multipath fading has occurred when it differs greatly from the original information, and performs notification (see, for example, Patent Document 2).
JP 2007-27932 A ([0023], [0024]) JP 2003-101468 A ([0029])

  However, the conventional wireless communication device disclosed in Patent Document 1 uses a packet error of a received packet to determine the degree of radio interference, but receives a large number of packets to detect the packet error. Need. Therefore, there is a problem that it takes a long time to accurately detect a packet error when the frequency of packet reception is low.

  Further, in the conventional wireless communication device disclosed in Patent Document 2, an extra pilot signal phase amplitude detection unit for detecting the amplitude and phase of the pilot signal is necessary, and the detection method is not simple. There was a problem of increasing on a scale that cannot be ignored.

  The present invention has been made to solve such a conventional problem, and is a wireless reception capable of detecting the occurrence of multipath fading in a shorter time and with a simple detection method than the conventional one. An object is to provide an apparatus.

  The radio reception apparatus of the present invention is a radio reception apparatus that receives an OFDM signal having a guard interval including a symbol interval and a null signal, and determines whether multipath fading has occurred, wherein the radio reception device in the symbol interval A first power detector for detecting the power of the OFDM signal; a second power detector for detecting the power of the OFDM signal in the guard interval; and detecting the power of the OFDM signal in the symbol interval and the guard interval. A third power detector that calculates power, a power ratio calculator that calculates a ratio of the power detected by the second power detector to the power detected by the first power detector, and the power ratio calculator And the power detected by the third power detection unit based on the ratio calculated by Has a configuration in which multipathing fading equipped with a multi-path fading determining unit determines whether the occurred.

  With this configuration, the radio reception apparatus of the present invention determines the occurrence of multipath fading based on the power of the OFDM signal in the symbol period, the power of the OFDM signal in the guard period, and the power of the OFDM signal in the symbol period and the guard period. The occurrence of multipath fading can be detected in a shorter time and with a simple detection method than the conventional one.

  In addition, the multipath fading determination unit is configured such that the power detected by the third power detection unit exceeds a predetermined first threshold, and the ratio calculated by the power ratio calculation unit is predetermined. When the threshold value of 2 is exceeded, it may be determined that multipath fading has occurred.

  With this configuration, the radio reception apparatus of the present invention can detect the occurrence of multipath fading even when the power of the received signal is sufficiently large.

  In addition, the wireless reception device of the present invention may include a display unit that displays the determination result determined by the multipath fading determination unit.

  With this configuration, the wireless reception device of the present invention can visually notify the user of the occurrence of multipath fading.

  In addition, the wireless reception device of the present invention may include an interface unit for outputting the determination result to an external terminal device.

  With this configuration, the wireless reception device of the present invention can notify the user of the occurrence of multipath fading via the external terminal device.

  The display unit may display the power detected by the third power detection unit and the ratio calculated by the power ratio calculation unit together with the determination result.

  With this configuration, the radio reception apparatus of the present invention notifies the user of the occurrence of multipath fading and notifies the user of the received signal power and the ratio calculated by the power ratio calculation unit, thereby providing a more detailed radio wave reception state. Users can recognize related information.

  The radio reception apparatus of the present invention is a radio reception apparatus that receives an OFDM signal having a guard interval including a symbol interval and a null signal, and determines whether multipath fading has occurred, wherein the radio reception device in the symbol interval A first power detector for detecting the power of the OFDM signal; a second power detector for detecting the power of the OFDM signal in the guard interval; and the first power detector for the power detected by the first power detector. A power ratio calculation unit that calculates a ratio of the power detected by the two power detection units; and the multipath based on the ratio calculated by the power ratio calculation unit and the power detected by the first power detection unit. A multipath fading determination unit that determines whether or not fading has occurred. To have.

  With this configuration, the radio reception apparatus of the present invention determines the occurrence of multipath fading based on the power of the OFDM signal in the symbol section and the power of the OFDM signal in the guard section, and in a shorter time than the conventional one, and The occurrence of multipath fading can be detected with a simple detection method.

  The present invention can provide a wireless receiver capable of detecting the occurrence of multipath fading in a shorter time than the conventional one and by a simple detection method.

  Hereinafter, embodiments of a wireless reception apparatus according to the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a radio reception apparatus according to the first embodiment of the present invention. A wireless receiver 1 according to the first embodiment of the present invention shown in FIG. 1 includes an antenna 10 that receives an OFDM (Orthogonal Frequency Division Multiplexing) signal having a frequency f ₁ , and a low-frequency amplifier that amplifies the OFDM signal received by the antenna 10. The OFDM signal is converted to a signal having a frequency f ₂ ± f ₁ by frequency-mixing the noise amplifier 11 and the OFDM signal amplified by the low noise amplifier 11 and a local oscillation signal having a frequency f ₂ output from a local oscillator (not shown). A frequency converter 12 that converts the signal to a frequency f _2, a band pass filter (BPF) 13 that filters a signal of frequency f ₂ ± f ₁ and transmits a base band signal of frequency f ₂ −f _{1, and} a baseband that is transmitted by the BPF 13 The received signal strength is detected from the AD converter 14 for digitizing the signal and the baseband signal transmitted by the BPF 13. A third received signal strength detecting unit 15 as a power detection unit for, a.

  The radio reception apparatus 1 also includes a symbol interval detector 16 that detects a symbol interval from the baseband signal digitized by the AD converter 14 and a digitized base in the symbol interval detected by the symbol interval detector 16. A symbol power detection unit 17 as a first power detection unit for detecting the power of the band signal (hereinafter referred to as symbol power), and a guard interval for detecting a guard interval from the baseband signal digitized by the AD converter 14 Guard section power detection as a second power detection section that detects the power of the digitized baseband signal in the guard section detected by the detection section 18 and the guard section detection section 18 (hereinafter referred to as guard section power). Unit 19 and the symbol power detection unit 17 The ratio of the guard interval powers detected by the guard interval power detection unit 19 for Rupawa (hereinafter, referred to as power ratio) further includes a power ratio calculation unit 20 for calculating a, a.

  Further, the wireless reception device 1 includes a multipath fading determination unit 21 that determines whether or not multipath fading has occurred based on the power ratio and the received signal strength, and a control unit 22 that controls the multipath fading determination unit 21. And a display unit 23 for notifying the user of occurrence of multipath fading when the multipath fading determination unit 21 determines the occurrence of multipath fading.

  Here, FIG. 2 schematically shows the configuration of the received signal. Conventional OFDM transmission schemes achieve long symbol lengths by using multiple orthogonal subcarriers, and can reduce interference between different symbols by providing guard intervals between symbols. It is a simple transmission method.

  In the guard interval, a method of repeatedly transmitting a part of the symbol signal or a method of inserting a null signal (null prefix), such as a transmission method of wireless USB communication, is used. A method of inserting a null signal in the section is adopted.

  That is, as shown in FIG. 2, a null signal is inserted as a guard interval for each symbol in the OFDM signal. The time width of the guard interval is determined by the state of the transmission path, that is, the maximum delay time of the delayed wave that affects demodulation. Intersymbol interference can be prevented by making the guard interval larger than the maximum delay time of the delayed wave. For example, in the case of the wireless USB system, the symbol interval is 242.42 ns, and the guard interval is determined to be 70.08 ns.

  The received signal strength detection unit 15 detects received signal strength, which is a signal representing the power of the received signal in real time, and temporarily stores the received signal strength, for example, a plurality of signals in a predetermined section (for example, a symbol section and a guard section). The average value of the received signal strength at the time is output as the received signal strength in that section.

  The symbol interval detection unit 16 detects the start time of the symbol interval based on the change in the power of the digitized baseband signal, and detects a certain time (for example, 242.42 ns in wireless USB) using a timer or the like. Detect symbol intervals.

  The symbol power detection unit 17 detects the symbol power by summing the square value of the digital data of the digitized baseband signal in the symbol interval product.

  The guard interval detection unit 18 detects the guard interval by detecting a certain time (for example, 70.08 ns for wireless USB) using a timer or the like, with the end time of the symbol interval as the start time of the guard interval.

  For example, the guard section power detection unit 19 detects the guard section power by summing the square values of the digital data of the digitized baseband signal.

  For example, when the multipath fading determination unit 21 determines the occurrence of multipath fading by turning on an LED, the display unit 23 notifies the user to that effect.

  FIG. 3 schematically shows a time waveform of the received signal. Waveform 3-1) is a state without multipath fading, and there is no signal in the guard interval. Waveform 3-2) is a state in which there is multipath fading, and a delayed wave of the symbol signal appears in the guard interval. Similarly, the waveform 3-3) has multipath fading, and a delayed wave of the symbol signal appears in the guard interval.

  As for the waveform 3-2), the level of the delayed wave is smaller than that of the waveform 3-3), but it can be seen that the delay time is long. Conversely, for waveform 3-3), the level of the delayed wave is greater than that of waveform 3-2), but it can be seen that the delay time is short. Therefore, the power ratio calculation unit 20 can detect the occurrence of multipath fading of the received signal by calculating a power ratio that is a ratio between the guard interval power and the symbol power (guard interval power / symbol power).

  However, in the detection of only the power ratio, the power ratio is increased due to multipath fading, or simply because the level of the received signal is small (for example, because the radio transmission device is far from the radio reception device). It cannot be determined whether the power ratio is increased due to the SNR degradation due to the noise of the noise amplifier 11. Therefore, the multipath fading determination unit 21 uses the received signal strength output from the received signal strength detection unit 15 in addition to the power ratio in order to detect the influence of multipath fading.

The multipath fading determination unit 21 determines whether multipath fading has occurred using the received signal strength and the power ratio, using a table as shown in [Table 1]. In the table shown in [Table 1], a first threshold value a for received signal strength and a second threshold value b for power ratio are set in advance, and there are four types of situations.

  Situation 1 is a case where the received signal strength is large and the power ratio is large, and the guard section power is large even though the distance to the wireless transmission device is short. That is, in the situation 1, since the radio wave reception state is not good due to the occurrence of multipath fading, the multipath fading determination unit 21 determines that “multipath fading is present”.

  Situation 2 is a case where the received signal strength is large and the power ratio is small, and the distance from the wireless transmission device is short and the guard section power is small. That is, in situation 2, since multipath fading has not occurred and the radio wave reception state is good, the multipath fading determination unit 21 determines “no multipath fading”.

  Situation 3 is a case where the received signal strength is small and the power ratio is large, and the level of the received signal is small because the distance to the wireless transmission device is far, and the guard interval power is large due to SNR degradation due to noise of the low noise amplifier 11. is there. That is, in the situation 3, the radio wave reception state is not good regardless of the occurrence of multipath fading. At this time, the multipath fading determination unit 21 determines “no multipath fading”.

  Situation 4 is a case where the received signal strength is small and the power ratio is small, and the level of the received signal is small because the distance to the wireless transmission device is far, but the guard interval power due to SNR degradation due to noise of the low noise amplifier 11 is also small. It is. That is, multipath fading does not occur in situation 4, but the radio wave reception state is better than situation 3 but not better than situation 2 because the level of the received signal is small. For this reason, the multipath fading determination unit 21 determines “no multipath fading”.

  Note that the threshold values a and b are values obtained from experiments, values obtained from theoretical values of spatial attenuation of radio waves, and the like, and can be changed by the control unit 22.

  Next, the operation of the wireless reception device 1 of this embodiment will be described.

A signal received by the antenna 10 is amplified by a low noise amplifier 11 and frequency-mixed with a local oscillation signal having a frequency f ₂ output from a local oscillator (not shown) by a frequency converter 12 to obtain a frequency f ₂ ± f _1. Is converted into a signal. The signal having the frequency f ₂ ± f ₁ is filtered by the BPF 13 and transmitted as a baseband signal of the signal having the frequency f ₂ −f ₁ .

  The baseband signal is digitized by the AD converter 14. A symbol interval is detected by the symbol interval detector 16 from the digitized baseband signal, and a symbol power in the symbol interval is detected by the symbol power detector 17.

  Further, a guard section is detected from the digitized baseband signal by the guard section detection unit 18, and a guard section power in the guard section is detected by the guard section power detection unit 19.

  The power ratio is calculated by the power ratio calculation unit 20 from the symbol power and guard interval power obtained in this way.

  On the other hand, the received signal strength is detected by the received signal strength detector 15 from the baseband signal transmitted by the BPF 13. The multipath fading determination unit 21 determines the occurrence of multipath fading from the power ratio and the received signal strength based on the table shown in [Table 1].

  When the multipath fading determination unit 21 determines that multipath fading has occurred, the display unit 23 notifies the user of that fact. Thereby, the user can recognize the deterioration of the radio wave state due to multipath fading by the display unit 23 and change the position and direction of the antenna, thereby suppressing the occurrence of multipath fading, and stable wireless communication. Is possible.

  In the present embodiment, the first power detection unit may detect an average value of received signal strengths at a plurality of time points in the symbol section as symbol power, like the received signal strength detection unit 15. The second power detection unit may detect an average value of received signal strengths at a plurality of points in the guard interval as the guard interval power like the received signal strength detection unit 15. Further, the third power detection unit may detect the signal power in the symbol interval and the guard interval like the symbol power detection unit 17 and the guard interval power detection unit 19.

  As described above, since the radio reception apparatus according to the present embodiment determines multipath fading using the received signal strength and power ratio, the multipath can be performed in a shorter time and with a simple detection method than the conventional one. The occurrence of fading can be detected.

  In addition, since the wireless reception device of this embodiment can determine whether or not multipath fading has occurred in the wireless reception signal, the user can recognize that the radio wave reception state is not good and change the direction and location of the antenna. It is possible to obtain a good reception state.

(Second Embodiment)
FIG. 4 is a block diagram showing a wireless reception apparatus according to the second embodiment of the present invention. The same components as those in the first embodiment of the present invention are denoted by the same reference numerals and description thereof is omitted. The radio receiver 4 according to the second embodiment of the present invention shown in FIG. 4 includes a symbol section detector 46, a symbol power detector 47, a guard section detector 48, and a guard section power detector 49, which are digitized bases. It differs from the wireless receiver according to the first embodiment of the present invention in that it detects the symbol interval, symbol power, guard interval, and guard interval power using the received signal strength of the analog baseband signal instead of the band signal. .

  Next, the operation of the wireless reception device 4 of this embodiment will be described.

Similar to the radio reception apparatus according to the first embodiment of the present invention, the signal having the frequency f ₂ ± f ₁ is filtered by the BPF 13 and transmitted as the baseband signal of the signal having the frequency f ₂ −f ₁ . The received signal strength is detected by the received signal strength detection unit 15 from the baseband signal transmitted by the BPF 13.

  The symbol interval detector 46 detects the symbol interval from the received signal strength output from the received signal strength detector 15, and the symbol power detector 47 detects the symbol power. As described above, since the received signal strength is a signal that represents the power of the received signal in real time, when the symbol power is detected by the symbol power detection unit 47, for example, the received signal at one point in time in the symbol interval is used. The intensity or the average value of the received signal intensity at a plurality of time points may be used.

  Similarly, a guard interval is detected from the received signal strength by the guard interval detecting unit 48, and the guard interval power detecting unit 49 detects, for example, the received signal strength at one point in the guard interval or the average of received signal strengths at a plurality of points in time. The guard interval power is detected by the value.

  Then, similarly to the radio reception apparatus according to the first embodiment of the present invention, the power ratio is calculated by the power ratio calculation unit 20 from the symbol power and the guard interval power, and the multipath fading determination unit 21 generates multipath fading. If it is determined that it is, the display unit 23 notifies the user to that effect.

  As described above, the radio reception apparatus according to the present embodiment can detect multipath fading without using an AD converter in addition to the effects of the first embodiment of the present invention.

(Third embodiment)
FIG. 5 is a block diagram showing a wireless reception apparatus according to the third embodiment of the present invention. The same components as those in the first embodiment of the present invention are denoted by the same reference numerals and description thereof is omitted. A wireless reception device 5 according to the third embodiment of the present invention shown in FIG. 5 includes a reception signal strength detection unit 55 that detects reception signal strength from a baseband signal digitized by the AD converter 14, and multipath fading. An input / output interface (IO) unit 50 that outputs occurrence information, a personal computer (PC) 51 as an external terminal device that displays the occurrence information of multipath fading on a screen, and a threshold value a used in the multipath fading determination unit 21; and a control unit 52 that changes information on occurrence of multipath fading to the PC 51 via the IO unit 50 and is different from the wireless reception device according to the first embodiment of the present invention. A PDA (Personal Digital Assist) or the like may be used as the external terminal device.

  Next, the operation of the wireless reception device 5 of this embodiment will be described.

  When it is determined by the multipath fading determination unit 21 that multipath fading has occurred as in the wireless reception device of the first embodiment of the present invention, the determination result is sent to the IO unit 50 by the control unit 52. Via the PC 51.

  The PC 51 displays multipath fading occurrence information based on the transmitted determination result on the screen. For example, when multipath fading has occurred, the degree of multipath fading may be displayed by displaying the power ratio as a bar graph.

  As described above, in addition to the effects of the first embodiment of the present invention, the wireless reception device of the present embodiment, when multipath fading has occurred, notifies the user via the external terminal device. Can be notified.

  In addition, since the radio reception apparatus according to the present embodiment can make most of the circuit configuration of the apparatus a digital circuit, the circuit configuration is easy.

(Fourth embodiment)
FIG. 6 is a block diagram showing a wireless reception apparatus according to the fourth embodiment of the present invention. The same components as those in the third embodiment of the present invention are denoted by the same reference numerals and description thereof is omitted. The wireless reception device 6 according to the fourth embodiment of the present invention shown in FIG. 6 includes a reception signal strength detection unit 55 that detects the reception signal strength from the baseband signal digitized by the AD converter 14, and multipath fading determination. And a display unit 63 that notifies the user when the occurrence of multipath fading is determined by the unit 21.

  The display unit 63 includes a power ratio display unit 63a that displays the power ratio calculated by the power ratio calculation unit 20, a signal strength display unit 63b that displays the received signal strength detected by the received signal strength detection unit 55, and a multi A determination result display unit 63c for displaying the determination result when the path fading determination unit 21 determines the occurrence of multipath fading.

  Next, the operation of the wireless reception device 6 of this embodiment will be described.

  As in the first embodiment of the present invention, when the multipath fading determination unit 21 determines that multipath fading has occurred, the determination result display unit 63c displays that fact and notifies the user. . At the same time, the power ratio is displayed on the power ratio display unit 63a, and the received signal strength is displayed on the signal strength display unit 63b.

  Therefore, in addition to the effect of the first embodiment of the present invention, the wireless reception device of the present embodiment displays the power ratio and the received signal strength at the same time, so that more detailed radio wave status information and received signal quality can be obtained. It is possible to make the user recognize information related to the above.

  That is, when the power ratio displayed by the power ratio display unit 63a is large and the received signal strength displayed by the signal strength display unit 63b is large, the user is close to the wireless transmission device and the level of the received signal is sufficient. However, it can be recognized that strong multipath fading has occurred due to the surrounding environment, and multipath fading can be avoided by changing the direction of the antenna.

  In addition, when the power ratio displayed by the power ratio display unit 63a is small and the received signal strength displayed by the signal strength display unit 63b is small, the user has a wireless transmission device far away and the received signal level is low. The radio wave condition can be improved by recognizing that the antenna is small and moving the antenna position closer to the wireless transmission device so that the received signal strength is increased.

(Fifth embodiment)
FIG. 7 is a block diagram showing a wireless reception apparatus according to the fifth embodiment of the present invention. The same components as those in the first embodiment of the present invention are denoted by the same reference numerals and description thereof is omitted. In the wireless reception device 7 according to the fifth embodiment of the present invention shown in FIG. 7, the multipath fading determination unit 71 detects the symbol power detected by the symbol power detection unit 17 and the power calculated by the power ratio calculation unit 20. It is determined whether multipath fading has occurred based on the ratio. Note that, in the wireless reception device 7, a reception signal strength detection unit that detects the reception signal strength is omitted.

The multipath fading determination unit 71 uses the table as shown in [Table 2] to determine whether multipath fading has occurred using the symbol power and the power ratio. In the table shown in [Table 2], a threshold c for symbol power and a threshold b for power ratio are set in advance, and there are four types of situations.

  Situation A is a case where the symbol power is large and the power ratio is large, and the guard section power is large even though the distance from the wireless transmission device is short. That is, in the situation A, since the radio wave reception state is not good due to the occurrence of multipath fading, the multipath fading determination unit 71 determines that “multipath fading is present”.

  The situation B is a case where the symbol power is large and the power ratio is small, and the distance from the wireless transmission device is short and the guard section power is small. That is, in the situation B, since multipath fading has not occurred and the radio wave reception state is good, the multipath fading determination unit 71 determines “no multipath fading”.

  The situation C is a case where the symbol power is small and the power ratio is large, and the level of the received signal is small because the distance from the radio transmission apparatus is far, and the guard interval power is large due to SNR degradation due to noise of the low noise amplifier 11. . That is, in the situation C, the radio wave reception state is not good regardless of the occurrence of multipath fading. At this time, the multipath fading determination unit 71 determines “no multipath fading”.

  The situation D is a case where the symbol power is small and the power ratio is small, and the level of the received signal is small because the distance from the radio transmission apparatus is long, but the guard interval power due to the SNR degradation due to noise of the low noise amplifier 11 is also small. is there. That is, multipath fading does not occur in situation D, but the radio wave reception state is better than situation C but not better than situation B because the level of the received signal is small. For this reason, the multipath fading determination unit 71 determines “no multipath fading”.

  The thresholds b and c are values obtained from experiments, values obtained from theoretical values of spatial attenuation of radio waves, and the like, and can be changed by the control unit 22.

  Next, the operation of the wireless reception device 7 of this embodiment will be described.

  As in the first embodiment of the present invention, the power ratio is calculated by the power ratio calculation unit 20 from the symbol power and the guard interval power. Then, the multipath fading determination unit 71 determines the occurrence of multipath fading from the symbol power and power ratio based on the table shown in [Table 2].

  When the multipath fading determination unit 71 determines that multipath fading has occurred, the display unit 23 displays that fact and notifies the user.

  As described above, in addition to the effects of the first embodiment of the present invention, the radio reception apparatus according to the present embodiment uses the symbol power and the power ratio to determine multipath fading. Multipath fading can be detected without using a section.

It is a block diagram which shows the radio | wireless receiver of the 1st Embodiment of this invention. It is a conceptual diagram for demonstrating the structure of a received signal. It is a conceptual diagram which shows the time waveform of a received signal. It is a block diagram which shows the radio | wireless receiver of the 2nd Embodiment of this invention. It is a block diagram which shows the radio | wireless receiver of the 3rd Embodiment of this invention. It is a block diagram which shows the radio | wireless receiver of the 4th Embodiment of this invention. It is a block diagram which shows the radio | wireless receiver of the 5th Embodiment of this invention.

Explanation of symbols

1, 4, 5, 6 Wireless receiver 10 Antenna 11 Low noise amplifier 12 Frequency converter 13 BPF
14 AD converter 15, 55 Received signal strength detection unit 16, 46 Symbol interval detection unit 17, 47 Symbol power detection unit 18, 48 Guard interval detection unit 19, 49 Guard interval power detection unit 20 Power ratio calculation unit 21, 71 Multi Path fading determination unit 22, 52 Control unit 23, 63 Display unit 50 IO unit 51 PC
63a Power ratio display unit 63b Signal strength display unit 63c Determination result display unit

Claims (5)

A radio receiving apparatus that receives an OFDM signal having a guard interval including a symbol interval and a null signal, and determines whether multipath fading has occurred,
A first power detector for detecting the power of the OFDM signal in the symbol period;
A second power detector that detects the power of the OFDM signal in the guard interval;
A third power detector for detecting the power of the OFDM signal in the symbol interval and the guard interval;
A power ratio calculation unit that calculates a ratio of the power detected by the second power detection unit to the power detected by the first power detection unit;
A multipath fading determination unit that determines whether or not the multipath fading has occurred based on the ratio calculated by the power ratio calculation unit and the power detected by the third power detection unit. A wireless receiver characterized by that.   The multipath fading determination unit has a second power in which the power detected by the third power detection unit exceeds a predetermined first threshold, and a ratio calculated by the power ratio calculation unit is predetermined. The radio reception apparatus according to claim 1, wherein it is determined that multipath fading has occurred when a threshold value is exceeded.   The radio reception apparatus according to claim 1, further comprising a display unit that displays a determination result determined by the multipath fading determination unit.   The wireless reception device according to claim 3, further comprising an interface unit for outputting the determination result to an external terminal device.   The radio reception apparatus according to claim 3, wherein the display unit displays the power detected by the third power detection unit and the ratio calculated by the power ratio calculation unit together with the determination result.

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