JP2010183552A - Doppler shift generating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To add a speed difference (Doppler shift effect) in order of time to a high-frequency signal in a radio wave state. <P>SOLUTION: A directional antenna 6 transmits radio waves toward a rotary reflecting body 1 via a radio propagation path 8. The rotary reflecting body 1 and a rotary shaft body 2 rotate about a rotation axis 3 in a rotational direction 4 by a drive means. At this time, the reflecting surface of the rotary reflecting body 1 moves in a direction shown by 5 in order to form a spiral shape. Radio waves reflected from the rotary reflecting body 1 are received by a test radio device 10 via a reflection propagation path 9. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a Doppler shift generation apparatus used for wireless communication and radio wave propagation tests.

  Frequency resources are an essential element of useful communication means that exist in nature. For this reason, almost all frequencies are publicly restricted. Therefore, it is assumed that the research, development, and manufacture of wireless communication devices are performed using an anechoic chamber or a radio wave shielding room. However, the radio wave propagation environment used by an actual wireless device is complicated and changes from time to time due to influences such as fading effects and Doppler effects.

  For this reason, conventionally, in order to simulate an outdoor environment, a test has been performed using a fading simulator or the like (Patent Document 1, Patent Document 2, Non-Patent Document 1, and Non-Patent Document 2).

  The fading simulator digitizes the transmission output by the sampling means, then extracts the baseband signal, performs delay wave synthesis corresponding to the fading effect, performs modulation and frequency conversion, and returns to the carrier frequency of the original signal. .

  Patent Document 2 is a fading simulator for an array antenna, which generates a simulated fading signal that simulates a fading signal based on a plurality of incoming waves output from each element of the array antenna.

  In this fading simulator, information to be transmitted is generated by a transmission signal generator, and a radio wave propagation path equal to the number of elements of the array antenna is configured on the circuit and transmitted. By generating a simulated fading signal with an angular spread in the incident direction of the incoming wave as a simulated fading signal, the characteristics and functions of the receiving device including the receiving system and the signal processing system can be evaluated under conditions that are closer to actual conditions. Is configured to be feasible.

  The means for generating a simulated fading signal having an angular spread is composed of the same number of DDSs (direct digital synthesizers) as the elements of the array antenna, and means for updating the phase and amplitude set for each of these DDSs, A simulated fading signal that is close to reality can be generated.

  In this method, a realistic simulated fading signal can be generated by updating the phase and amplitude set in each DDS at a period that satisfies the Nyquist condition of the maximum Doppler frequency of the signal. Furthermore, a simulated fading signal with a wider dynamic range can be generated by analog multiplication of the output of each DDS and the modulation signal. In addition, a plurality of means for generating a simulated fading signal having an angular spread in the incident direction of a plurality of incoming waves are provided, and the same number of output signals as the number of elements of the array antenna output from each are synthesized to each corresponding element. By providing the signal synthesis means for outputting, a more realistic simulated fading signal can be generated.

  In addition, the conventional Doppler shift generator receives a target high-frequency signal, detects and A / D-converts it, and then uses a DDS (Direct Digital Synthesizer) or the like to obtain the maximum phase and amplitude of the signal. The digital data is updated at a period that satisfies the Nyquist condition of the Doppler frequency, and the digital data is D / A converted and modulated and frequency converted.

JP 2003-298536 A JP 2002-325011 A

Hidenori Oguni, Eisuke Kudo, Fumiyuki Adachi, "Frequency-selective fading simulator that generates fading waves with arbitrary multi-wave arrival angle distribution," 5th DSP Educator Conference, pp.55-60, September 2002. Public URL: http://www.mobile.ecei.tohoku.ac.jp/paper/pdf/rcs_2002/09_rcs_2002_sao.pdf (Figure 2) Product Overview of Agilent Multipath Fading Simulator / Signature Test Set product number 11757B URL: [http://cp.literature.agilent.com/litweb/pdf/5091-1052EN.pdf] “Agilent 11757B Multipath Fading Simulator / Signature Test Set Product Overview ”

  However, the conventional Doppler shift generation device receives the target high frequency signal, not on the high frequency of the original carrier frequency, and once receives and detects and A / D converts the phase and amplitude to the maximum of the signal. Since the digital data is updated at a period satisfying the Nyquist condition of the Doppler frequency, and the digital data is D / A converted and subjected to modulation and frequency conversion, the modulation accuracy and frequency characteristics inherent in the high frequency signal are inherent in the Doppler shift generation device. Deteriorated by errors and noise. Furthermore, the conventional Doppler shift generation device cannot cope with a case where a plurality of high-frequency signals having different frequency bands exist. Further, the radio wave propagation path is a Doppler for a radio communication system for both downlink and uplink, that is, propagation from a network system represented by a radio base station to a radio terminal and propagation from the radio terminal to the base station. As described above, the conventional Doppler shift generation device receives a communication, extracts its components, and then adds a fading effect that becomes a Doppler shift effect as described above. It is difficult to build a test environment that suits

  This invention is made in view of this point, and provides a Doppler shift production | generation apparatus which can add a time-sequential speed difference (Doppler shift effect) to a high frequency signal with a radio wave state. Objective.

  The Doppler shift generation device of the present invention is a generation device that adds a Doppler shift to a radio wave having directivity transmitted from a directional antenna, the rotation shaft body being rotatable around one rotation axis, A rotating reflector that is attached to a rotating shaft and has a reflecting surface that reflects the radio wave in a spiral shape, and a radial direction of the reflecting surface has an angle of about 90 degrees with respect to the rotating shaft; and the rotating shaft And a driving means for rotating the at a predetermined speed.

  According to the present invention, by providing a high-speed rotating body having a spiral reflecting surface, if a high-frequency signal is reflected by the high-speed rotating body, the time-series speed difference (Doppler shift effect) Can be added.

The figure which shows the structure of the system which concerns on Embodiment 1 of this invention. The figure which shows the structure of the Doppler shift production | generation apparatus of Embodiment 1 of this invention. The figure which shows the structure of the Doppler shift production | generation apparatus of Embodiment 2 of this invention. The figure which shows the structure of the system which concerns on Embodiment 3 of this invention. The figure which shows the structure of the system which concerns on Embodiment 4 of this invention. The figure which shows the structure of the system which concerns on Embodiment 5 of this invention. The figure which showed the structure of the multipath fading production | generation apparatus containing the antenna group for the multipath fading production | generation which showed the concept in FIG. The figure which shows the relationship of the Doppler shift frequency by the positional relationship between a mobile body and a propagation path The figure which shows the structure of the system which concerns on Embodiment 6 of this invention. The figure explaining the Doppler shift frequency which arises in an antenna Diagram showing the entire system when generating Rayleigh fading or rice fading Diagram showing the multipath fading generation system when considering the actual situation of the urban environment

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram illustrating a configuration of a system according to the first embodiment. 1 is a rotating reflector, 2 is a rotating shaft body, 3 is a rotating shaft of the rotating reflector 1 and the rotating shaft body 2, 4 is a rotating direction of the rotating reflector 1 and the rotating shaft body 2, and 5 is a reflection of the rotating reflector 1. Indicates the direction of movement of the surface. Reference numeral 6 denotes a directional antenna that transmits a directional radio wave (high-frequency signal) toward the rotary reflector 1, 7 denotes a connection line with a wireless system connected to the directional antenna 6, and 8 denotes a transmission from the directional antenna 6. A radio propagation path through which the transmitted radio wave passes, 9 is a reflection propagation path through which the radio wave that has passed through the radio propagation path 8 is reflected by the rotating reflector 1, and 10 is a test radio that receives the radio wave that has passed through the reflection propagation path. , 11 is an anechoic chamber, and 12 is a means for preventing direct wireless coupling between the directional antenna 6 and the test radio 10.

  The operation of the system according to the present embodiment will be described with reference to FIG. A directional antenna 6 connected to a connection line 7 from an arbitrary wireless system transmits a radio wave toward the rotating reflector 1 via a wireless propagation path 8. The rotary reflector 1 and the rotary shaft 2 are rotated in the direction of the rotation direction 4 around the rotary shaft 3 by a driving means (not shown). At this time, since the rotary reflector 1 has a spiral shape (spiral shape), the reflecting surface moves in the direction indicated by 5. The radio wave reflected by the rotary reflector 1 is received by the test radio device 11 via the reflection propagation path 9. These components are placed in the anechoic chamber 11. The anechoic chamber 11 and the wireless coupling prevention means 12 prevent the generation of a wireless propagation path other than the desired wireless propagation path.

  FIG. 2 is a diagram illustrating a structure of the Doppler shift generation apparatus according to the present embodiment. In FIG. 2, the same reference numerals as those in FIG. 13 is the radius of rotation of the rotating reflector 1, 14 is the diameter of the reflecting surface portion of the rotating reflector 1, 15 is the diameter of the rotating shaft portion of the rotating reflector 1, 16 is the pitch of the helical shape of the rotating reflector 1, 17 Denotes a normal direction to the radius of the reflecting surface of the rotary reflector 1, and 18 denotes an angle formed by the rotation axis of the rotary reflector 1 and the normal direction of the reflecting surface.

The operation of the Doppler shift generation apparatus according to the present embodiment will be described with reference to FIG. The rotary reflector 1 has a spiral shape with a pitch 16. Due to the effect of the spiral, the reflecting surface is given a movement distance corresponding to the pitch 16 when the rotating reflector 1 rotates once. On the other hand, the reflection surface of the rotary reflector 1 has an angle 18 formed by the reflection surface and the rotary shaft 3 at a right angle. For this reason, the movement distance provided by the reflector can be directly treated as a propagation path length change with respect to the wireless propagation path. That is, if the angle 18 formed by the reflecting surface and the rotating shaft 3 is θ, the pitch 16 is p (mm), and the rotational speed is r (rotation / min), the moving distance l (mm) per hour indicated by the reflecting surface is shown. ) Is given by the following equation (1). Here, the numerical value “2” in the first term of the expression (1) indicates that the virtual image in the reflection surface of the radio wave source is moving at a speed twice the moving speed of the reflector as shown in FIG. It means to act as follows.

Since θ = 90 °, the movement distance l (mm) is expressed by the following equation (2).

  Now, assuming that the pitch p is 50 mm and the rotation speed r is 15,000 times / minute, the moving distance l of the reflecting surface is 90,000,000 mm, that is, 90 km. This means that the rotating reflector 1 generates a moving effect of 90 km / h on the radio wave propagation path.

For example, considering an unmodulated wave with a frequency of 1,000 MHz, the Doppler shift frequency _fd is given by the following equation (3).

  If the frequency is 2,000 MH, not only the Doppler shift frequency of 166.6 Hz can be easily obtained, but also functions simultaneously for two types of radio waves of 1,000 MHz and 2,000 MHz. Further, the present system does not limit the directionality of the radio wave propagation path, and applies Doppler shift to the propagation in the direction opposite to the arrow direction of the propagation path in FIG.

  As described above, according to the present embodiment, by providing the high-speed rotating body having a reflecting surface in a spiral shape, if the high-frequency signal is reflected on the high-speed rotating body, the time-series speed of the high-frequency signal in the radio wave state is obtained. A difference (Doppler shift effect) can be added, and all the above-mentioned problems of the conventional Doppler shift generation device can be solved.

(Embodiment 2)
The Doppler shift generating apparatus shown in the first embodiment needs to rotate the spiral reflector at high speed. According to this apparatus, the heat generated by the air resistance of the disk may destroy the disk. Embodiment 2 solves this problem.

  FIG. 3 is a diagram illustrating a structure of the Doppler shift generation apparatus according to the present embodiment. In FIG. 3, the same reference numerals as those in FIG. 1 or FIG. 21 is the first blade, 22 is the second blade, 23 is the pitch existing between the first tip of the first blade 21 and the second blade 22 that is switched, and 24 is the first blade 21. The pitch which exists between the front-end | tip part of the 2nd blade | wing 22 which switches to the 2nd front-end | tip part of this is shown.

The operation of the Doppler shift generation apparatus according to this embodiment will be described with reference to FIG. The Doppler shift generator shown in FIG. 2 has a large step at the pitch portion, that is, the disc discontinuous portion. The Doppler shift generation device shown in FIG. 3 divides the disk into two blades, and the step at the pitch portion can be halved with respect to FIG. Thereby, the air fluid resistance produced | generated in the cross section of a discontinuous part can be halved. Furthermore, in this embodiment, the number of divisions can be increased. When the number of divisions is n, the pitch 16 is p (mm), and the rotation speed is r (rotation / minute), the above equation (2) can be transformed into the following equation (4).

  According to this method, it is possible to freely reduce the rotation speed or reduce the pitch width depending on the number of divisions after making the product of the rotation speed and the pitch required in the first embodiment equal. become.

  Thus, according to the present embodiment, the heat generated by the reflection rotator can be reduced.

(Embodiment 3)
It should be considered that the Doppler shift effect in a moving body in an urban area is that reflection from a building or the like comes not only from the front of the moving body but also from the back. The third embodiment provides a method for solving this problem. FIG. 4 is a diagram showing the structure of the system according to the present embodiment. In FIG. 4, the same reference numerals as those in FIG.

  In FIG. 4, 31 is a rotary reflector, 32 is a rotary shaft body, 33 is a rotary shaft of the rotary reflector 31 and the rotary shaft body 32, 34 is a rotation direction of the rotary reflector 31 and the rotary shaft body 32, and 35 is a rotary reflection. The moving direction of the reflective surface of the body 31 is shown. Reference numeral 36 denotes a directional antenna that transmits a directional radio wave (high-frequency signal) toward the rotating reflector 31. Reference numeral 37 denotes a connection line 7 between the directional antenna 6 and a wireless system connected to the directional antenna 36. , 38 is a wireless propagation path through which the radio wave transmitted from the directional antenna 36 passes, and 39 is a reflection propagation path through which the radio wave that has passed through the wireless propagation path 38 is reflected by the rotating reflector 31.

  The operation of the system according to the present embodiment will be described with reference to FIG. The directional antenna 6 and the directional antenna 36 connected to the connection line 7 from an arbitrary radio system are directed to the rotary reflector 1 and the rotary reflector 31 by the radio propagation path 8 and the radio propagation path 38, respectively. The rotating reflector 31 has a moving direction 35 different from the moving direction 5 of the reflecting surface of the rotating reflector 1, and the Doppler shift frequency generated in the reflection propagation path 39 by the rotating reflector 31 is the rotational reflection. The body 1 has a reciprocal polarity with respect to the Doppler shift frequency generated in the reflection propagation path 9. In FIG. 4, the rotary reflector 1 and the rotary reflector 31 have the same shape, and the rotation direction 4 and the rotation direction 34 are opposite to each other. As a result, the radio waves reaching the test radio device 10 obtain positive and negative Doppler shift frequencies.

  Note that even if the rotation direction 4 and the rotation direction 34 are made the same, assuming that the pitch directions of the reflecting surfaces of the rotary reflector 1 and the rotary reflector 31 are opposite to each other, the radio waves reaching the test radio device 10 are positive and negative. To obtain the Doppler shift frequency.

  Thus, according to the present embodiment, it is possible to provide a positive and negative Doppler shift action that often occurs in urban areas. In addition, this method does not limit the directionality of the radio wave propagation path, and it also applies a Doppler shift to the propagation in the direction opposite to the arrow direction of the propagation path in FIG. This is the same as in the first embodiment.

(Embodiment 4)
A conventional Doppler shift generator receives a target high-frequency signal, detects and A / D-converts it, updates the phase and amplitude at a period that satisfies the Nyquist condition of the maximum Doppler frequency of the signal, Digital data is D / A converted and subjected to modulation and frequency conversion. This method cannot cope with a case where there are a plurality of high-frequency signals having different frequency bands. The fourth embodiment provides a method for solving this conventional problem. FIG. 5 is a diagram showing the structure of the system according to the present embodiment. In FIG. 5, the same reference numerals as those in FIG.

  In FIG. 5, 40 is a directional antenna that transmits radio waves having directivity toward the rotary reflector 1 and the rotary reflector 31, 41 is a connection line with the second wireless system that is connected to the directional antenna 40, 42. Is a radio propagation path through which a radio wave transmitted from the directional antenna 6 toward the rotary reflector 1 passes, 43 is a reflection propagation path through which the radio wave passed through the radio propagation path 42 is reflected by the rotary reflector 1, 44 is a radio propagation path through which the radio wave transmitted from the directional antenna 6 toward the rotary reflector 31 passes, and 45 is a reflection propagation path through which the radio wave passed through the radio propagation path 44 is reflected by the rotary reflector 31. , 46 is a radio propagation path through which the radio wave transmitted from the directional antenna 40 toward the rotary reflector 1 passes, and 47 is a radio propagation path after the radio wave that has passed through the radio propagation path 46 is reflected by the rotary reflector 1. 48 is a radio propagation path through which a radio wave transmitted from the directional antenna 40 toward the rotary reflector 31 passes, and 49 is after the radio wave that has passed through the radio propagation path 48 is reflected by the rotary reflector 31. The reflection propagation path which passes is shown.

  The operation of the system according to the present embodiment will be described with reference to FIG. In general, an antenna has frequency characteristics. For this reason, in order to construct a radio system corresponding to a plurality of types of frequency bands, it is natural to use respective antennas corresponding to the frequency bands. Now, assume that the directional antenna 6 corresponds to the first frequency and the directional antenna 40 corresponds to the second frequency. In the system of the present embodiment shown in FIG. 5, each of the two directional antennas transmits radio waves to the rotary reflector 1 and the rotary reflector 31 via the radio propagation paths 42, 44, 46 and 48. . The radio waves reflected by the rotary reflector 1 and the rotary reflector 31 are received by the test radio device 10 via the reflection propagation paths 43, 45, 47 and 49, respectively.

  Thus, according to the present embodiment, positive and negative Doppler shift frequencies can be simultaneously provided for radio waves of radio systems in different frequency bands. In addition, this method does not limit the directionality of the radio wave propagation path, and it also applies a Doppler shift to the propagation in the direction opposite to the arrow direction of the propagation path in FIG. This is the same as the first embodiment and the third embodiment.

  In the system of FIG. 5, when one of the positive and negative Doppler shift frequencies is unnecessary, it is possible to use a single rotating reflector.

(Embodiment 5)
In urban areas, building reflections are not simple, and reflections from multiple buildings must be taken into account. Conventionally, there is a problem that it is difficult to realize means for simulating a multipath fading environment for a radio system of a plurality of frequency bands. The present embodiment provides a method for solving this conventional problem. FIG. 6 is a diagram showing the structure of the system according to the present embodiment. In FIG. 6, the same reference numerals as those in FIG.

  In FIG. 6, 50 is a first multipath fading antenna group connected to the connection line 7 with the wireless system, and 51 is a second multipath connected to the connection line 41 with the second wireless system. An antenna group for fading generation, 52 is a wireless propagation path through which radio waves transmitted from the antenna group 50 toward the rotary reflector 1 pass, and 53 is a radio propagation path through which the radio propagation path 52 is reflected by the rotary reflector 1 A reflection propagation path that passes later, 54 is a radio propagation path through which radio waves transmitted from the antenna group 50 toward the rotary reflector 31 pass, and 55 is a radio propagation path through which the radio propagation path 54 is reflected by the rotary reflector 31 A reflection propagation path that passes later, 56 is a radio propagation path through which radio waves transmitted from the antenna group 51 toward the rotary reflector 1 pass, and 57 is a rotation reflection of radio waves that have passed through the radio propagation path 56. 1 is a reflection propagation path that passes after being reflected by 1, 58 is a radio propagation path through which a radio wave transmitted from the antenna group 51 toward the rotary reflector 31 passes, and 59 is a radio wave transmission path that passes through the radio propagation path 58. The reflection propagation path which passes after being reflected by 31 is shown.

  The operation of the system according to the present embodiment will be described with reference to FIG. Now, it is assumed that the antenna group 50 for generating multipath fading corresponds to the first frequency, and the antenna group 51 corresponds to the second frequency. In the system shown in FIG. 6, each of the two groups of antennas transmits radio waves to the rotary reflector 1 and the rotary reflector 31 via the radio propagation paths 52, 54, 56 and 58. The radio waves reflected by the rotary reflector 1 and the rotary reflector 31 are received by the test radio device 10 via the reflection propagation paths 53, 55, 57 and 59, respectively.

  FIG. 7 is a diagram showing a configuration of a multipath fading generation apparatus including the antenna group for multipath fading generation whose concept is shown in FIG. In FIG. 7, 61 corresponds to the connection line 7 with the wireless system in FIG. 62 is a distributor, 63 is an electronically controllable transmission amount adjustment unit, 64 is a transmission amount adjustment element of the transmission amount adjustment unit 63, 65 is a delay amount adjustment unit of each propagation path as a path, and 66 is a delay amount adjustment unit 65 is a delay amount adjusting element, 67 is an antenna group of the propagation path, and 68 is a radio wave propagation path generated by the antenna. 69 is an electronic control unit, and 70 is a control signal line.

A multipath fading generation method will be described with reference to FIG. The connection line 61 with the wireless system is divided into a plurality of lines by a distributor 62 in order to simulate a plurality of propagation paths. This line is connected to the transmission amount adjustment unit 63 and passes through the transmission amount adjustment element 64 constituting the transmission amount adjustment unit 63, and each output line thereof is connected to the delay amount adjustment unit 65, and the transmission constituting the delay amount adjustment unit 65. Each delay amount is given by the amount adjusting element 66. In FIG. 7, a cable having a line length corresponding to a desired delay amount is used. Each delay time _{t d1, t d2, t d3} , t d4, t d5, t d6, give the _{t d7,} t _d8. Each output line of the delay amount adjusting unit 65 is connected to an antenna group 67 having antennas of the number of lines, and becomes a radio wave to form a radio wave propagation path 68. As described above, a multipath fading environment is constructed in the radio wave propagation path 68.

  Thus, according to the present embodiment, it is possible to provide a multipath fading environment having simultaneously positive and negative Doppler shift frequencies for radio waves of radio systems in different frequency bands. In addition, this method does not limit the directivity of the radio wave propagation path, and it also applies a Doppler shift to the propagation in the direction opposite to the arrow direction of the propagation path in FIG. This is the same as the first embodiment, the third embodiment, and the fourth embodiment.

  In the system of FIG. 6, when one of the positive and negative Doppler shift frequencies is unnecessary, it is possible to use a single rotating reflector.

(Embodiment 6)
Here, in an actual outdoor environment, as shown in FIG. 8, various Doppler shift frequencies are generated by multiple propagation paths, that is, multipaths. FIG. 8 is a diagram illustrating the relationship of the Doppler shift frequency depending on the positional relationship between the moving body and the propagation path.

In FIG. 8, if the moving body 81 travels at a speed v (t) and the radio wave propagation path 82 arrives at an angle θ, the relative speed of the incoming wave is given by v (t) cos θ. In general, there are a plurality of incoming waves from different angles. In urban areas, radio waves transmitted from base stations are often reflected, diffracted or scattered by buildings or the like and reach the receiving point. In this case, in the case of receiving while moving in an environment where the direct wave from the base station cannot be seen, the amplitude of the synthesized wave of the incoming wave has an equal variance with an average value of “0” in the function of time. This is called Rayleigh fading. Rayleigh fading is named because the probability distribution of amplitude intensity of received waves is Rayleigh distributed. Theoretically, assuming that the number of incoming received waves is N, the amplitude of each is a _i , and the phase is φ _i , the fluctuation of the synthesized wave at the receiving point with respect to time t is the angular frequency of the carrier wave as ω _c. It can be expressed as the following equation (5).

Here, it is assumed that N is sufficiently large, the amplitude a _i of each incoming wave is substantially equal, and the phase φ _i is random. When the reception point is moved and a _i is observed, the synthesized value of the sine of the amplitude and the synthesized value of the cosine of the amplitude in the above formula (5) are normal values with an average value of “0” and equal variance values, independent of each other. It will have a distribution. At this time, the probability p (R) that the reception amplitude is R is given by the following equation (6).

This represents the appearance probability of the amplitude level R of the received wave observed by moving the reception point. This is the Rayleigh distribution, and when a certain amplitude level R _d is set for the received wave, the cumulative probability distribution that is equal to or less than R _d is P (R _d ) (see Expression (7)).

On the other hand, rice fading is generated in a multiple propagation path in an environment where the base station can be seen. The probability p (R) that the reception amplitude becomes R when the base station antenna is visible, the line-of-sight propagation, or one of the incoming waves E _o is much stronger than the other waves, is given by the following equation (8). This is called the Rice (or Nakagami-Rice) distribution. In Equation (8), σ / 2 is the combined power of incoming waves other than E _o , and r is the ratio of E _o power to σ / 2. I _o (x) is a zeroth-order modified Bessel function.

In the above equation (5), when the moving speed of the receiving point is given by v (t), the angular frequency ω _c and the phase φ _i need to have the relationship shown in the following equation (9). Since the frequency ω _c of the incoming wave from the angle θ when traveling at the speed v (t) should be expressed as a synthesis of ω _c (θ), the formula (9) is substituted into the formula (5). Then, the following equation (10) is obtained.

Equation (10) shows that the coefficient terms by the phase phi _i resulting from a variety of directions θ and the delay time is multiplied to the main signal cos .omega _{c t} and sin .omega _{c t.} Here, in Expression (10), ω _c × v / c is a Doppler frequency, and ω _c × (v / c) × cos ωθ _i is a Doppler frequency as a vector component from each direction. The above formula (10) can be expressed by the following formula (11) as a standard case.

  That is, in order to simulate a Rayleigh fading environment or a rice fading environment, the simulation may be insufficient only by generating a single Doppler frequency.

  Therefore, in the present embodiment, a case will be described in which a plurality of Doppler shift frequencies indicated by the Fay fading environment or the Rice fading environment are generated using the disk-shaped reflector described in the first embodiment or the like. Specifically, a plurality of radio waves having different irradiation angles, that is, sets of incident angles and outgoing angles, are irradiated onto the disk-shaped reflector described in the first embodiment.

  FIG. 9 is a diagram showing a configuration of a system according to the present embodiment. As illustrated in FIG. 9, the Doppler shift generation device 91 includes a rotating reflector 92, a rotating unit 93 that rotates the rotating reflector 92, and a container 95 that houses the rotating reflector 92. In FIG. 9, a rotating shaft 94 that connects the rotating reflector 92 and the rotating means 93, a moving direction 96 of the reflecting surface of the rotating reflector 92, a reflecting surface (portion used for reflection) 97 of the rotating reflector 92, A radio wave propagation path group 98 and an angle (incident angle) 99 formed by the propagation path 98 and the axis of the rotary reflector 92 are shown. In addition, FIG. 9 shows directional antenna groups 101 to 106 and 111 to 116 that irradiate or receive the rotating reflector 92 with radio waves at different angles.

  Hereinafter, the operation of the system according to the present embodiment will be described with reference to FIG. Now, the radio wave propagation path 98 from the antenna 101 enters the reflecting surface 97 with an incident angle 99. The radio wave reflected by the reflecting surface 97 travels in the opposite direction at an angle equal to the incident angle 99 and enters the antenna 111. On the same principle, radio waves arrive from the antenna 102 to the antenna 112, from the antenna 103 to the antenna 113, from the antenna 104 to the antenna 114, from the antenna 105 to the antenna 115, and from the antenna 106 to the antenna 116, respectively.

  At this time, the velocity of the reflecting surface is assumed to be v, and the Doppler shift frequency generated in each antenna will be described with reference to FIG.

  FIG. 10 shows the position 121 of the reflecting surface of the rotating reflector at time t0, the position 122 of the reflecting surface of the rotating reflector at time t1, the incident propagation path 123, the reflection point 124 for the incident propagation path 123, and the incident propagation path 123. Reflected wave propagation path 125, reflection point 126 at time t1, reflected wave propagation path 127 with respect to incident path 123 at time t1, antenna 128 forming incident path 123, antenna 129 housing reflected wave propagation paths 125 and 127, antenna 128 Radio wave radiation point 130, incident angle 131 of incident propagation path 123, reflection angle 132 of reflected wave propagation path 125, mirror image 134 of radio wave radiation point 130 of antenna 128 by reflecting surface 121 at time t0, and mirror image of antenna 128 at time t0. 135, mirror image 136 of radio wave radiation point 130 at time t1, time t1 Mirror image 137 of the definitive antenna 128 is shown.

  The incident wave 123 is reflected at the reflection point 124 at time t0 and becomes a reflected wave 125. At this time, the mirror image 134 is located on the opposite side equal to the normal direction l from the mirror surface (reflection surface) 121.

  Next, when moving from the reflecting surface 121 to the reflecting surface 122 between time t0 and time t1, the mirror image 134 moves to the mirror image 136. When viewed from the antenna 129 that receives the reflected wave, it appears as if radio waves are radiated from the mirror image antenna.

Here, the mirror image moves twice the moving distance L of the reflecting surface, but the moving distance of the mirror image with respect to the antenna 129 is 2L cos θ. As shown in the following equation (12), the moving speed of the mirror image antenna with respect to the antenna 129 is obtained by dividing by the difference between the time t0 and the time t1.

  As is clear from this equation (12), the moving speed of the mirror image antenna with respect to the antenna 129 is reduced by cos θ when the incident angle is zero, that is, when the incident angle is perpendicular to the reflecting surface. This indicates that exactly the same effect as the reduction of the Doppler shift frequency composed of the angle formed by the moving body and the propagation path shown in FIG. 8 can be obtained.

  That is, as shown in FIG. 9, it is obvious that different Doppler shift frequencies can be generated if radio waves having different incident angles are reflected by the reflecting surface of the rotary reflector.

  FIG. 11 shows the entire system when Rayleigh fading or rice fading is generated. FIG. 11 is obtained by adding changes to FIG. 7 in accordance with the purpose of the present embodiment. In FIG. 11, the same reference numerals as those in FIG. 7 are given to portions common to those in FIG. 7, and detailed description thereof is omitted.

  In FIG. 11, a combination of the antenna group 71 for forming a multipath, the propagation path 72, the antenna group 73 for accommodating the reflected wave, and the reflected wave accommodated by the antenna group 73 is newly added to FIG. 7. The output 75 of the combiner 74 and the combiner 74 is shown.

  The antenna groups 101 to 106 in FIG. 9 correspond to the antenna 71 in FIG. 11, the incident propagation path group and the reflection propagation path group in FIG. 9 correspond to the propagation path 72 in FIG. 11, and the antenna groups 111 to 116 in FIG. This corresponds to the antenna group 74 in FIG. Therefore, in FIG. 11, it is clear that the function corresponding to the above formula (11) is provided.

  FIG. 12 shows a multipath fading generation system in consideration of the original situation of the urban environment. In FIG. 12, the same reference numerals as those in FIG. 11 are given to portions common to FIG. 11, and detailed description thereof is omitted.

  In FIG. 12, a synthesizer 76 that bundles the outputs of the paths whose multipath radio wave intensity and delay amount are adjusted, and a means 77 for transmitting the output of the synthesizer 76 to the antenna group 71, an antenna, A distributor 78 that divides the output of the combiner 76 into a group 71 and an attenuator group 79 that performs power adjustment corresponding to each antenna group are shown.

  That is, the multipath fading generation system shown in FIG. 12 uniformly applies Rayleigh fading or rice fading to radio waves that arrive via multipath.

  Thus, according to the present embodiment, different Doppler shift frequencies can be generated by reflecting radio waves having different incident angles on the reflecting surface of the rotary reflector, and the Rayleigh fading environment or the rice fading can be generated. The environment can be simulated.

  The present invention is suitable for use in wireless communication and radio wave propagation tests.

DESCRIPTION OF SYMBOLS 1,31 Rotating reflector 2,32 Rotating shaft body 6,36 Directional antenna 10 Radio equipment under test 50, 51 Antenna group

Claims (6)

A generator for adding a Doppler shift to a radio wave having directivity transmitted from a directional antenna,
A rotating shaft body rotatable around one rotating shaft;
A rotating reflector that is attached to the rotating shaft and has a spiral shape that reflects the radio waves, and a radial direction of the reflecting surface has an angle of about 90 degrees with respect to the rotating shaft;
Driving means for rotating the rotating shaft at a predetermined speed;
A Doppler shift generation apparatus comprising:   The Doppler shift generation apparatus according to claim 1, wherein the rotary reflector has a shape divided into a plurality of parts. Having two pairs of the rotating shaft body and the rotating reflector,
The driving means rotates the first rotating shaft body and the second rotating shaft body in opposite directions when the first rotating reflector and the second rotating reflector have the same shape, and Rotating the first rotating shaft body and the second rotating shaft body in the same direction when the pitch directions of the reflecting surfaces of the rotating reflector and the second rotating reflector are opposite to each other;
The Doppler shift generation apparatus according to claim 1.   4. The Doppler shift generation device according to claim 1, wherein the rotary reflector reflects a plurality of radio waves emitted from a plurality of devices having at least one of a frequency, a modulation / demodulation method, and a communication method. .   The Doppler shift generation device according to any one of claims 1 to 4, wherein the rotary reflector reflects a plurality of radio waves irradiated at different incident angles. A Doppler shift generation device according to any one of claims 1 to 5,
A delayed wave group generating means comprising a plurality of delay means and attenuation adjustment means;
A Doppler shift generation device.