Delay profile generation system and delay profile generation method

Abstract

The present disclosure relates to a delay profile generation system. The delay profile generation system comprises: a reception antenna configured to be capable of receiving radio waves; a first cable of which one end is connected to the reception antenna; and a transmission antenna to which the other end of the first cable is connected and which is configured to be capable of transmitting, to the reception antenna, radio waves including a signal transmitted from the first cable. The delay profile generation system is configured such that isolation between the transmission antenna and the reception antenna is variable.

Description

Delay Profile Generation System and Delay Profile Generation Method

[0001] The present disclosure relates to a system and method for generating a delay profile.

[0002] For the application of wireless systems to high-reliability applications, there is an increasing need to reproduce the wireless environment in the assumed usage environment and conduct reliability tests on wireless characteristics.

[0003] As one of the devices used for reliability tests of wireless characteristics, a fading simulator as disclosed in Non-Patent Document 1 is known. For example, a method of conducting a reliability test of wireless characteristics is known in which one of the opposing wireless systems is connected to a fading simulator, and the signal generated by the fading simulator is transmitted from a transmitting antenna and received by the other wireless device.

[0004] As another method of conducting a reliability test of wireless characteristics, a method using an intelligent space formation technology as disclosed in Non-Patent Document 2 is also known. In a test of wireless characteristics using intelligent space formation technology, for example, two wireless devices and a reflector (RIS) with variable reflection direction are installed on the wall surface of the evaluation area, and a pseudo multi-path environment is reproduced by controlling the arrival angle of radio waves incident from one wireless device to the other wireless device.

[0005] Anritsu MF6900A Fading Simulator, https: / / dl.cdn-anritsu.com / ja-jp / test-measurement / files / Product-Introductions / Product-Introduction / MF6900A_JL1300.pdf Ryotaro Taniguchi, Tomonori Murakami, Tomoaki Ogawa, Yasushi Takatori "Evaluation of Wireless Space Reproduction Technology in Indoor Environments" IEICE Society Conference 2023 B-1-104, September 2023.

[0006] Conventional technologies for reproducing the wireless environment of a target usage environment have made it difficult to reproduce the desired delay profile in a low-cost and simple manner. While technologies for generating multipath environments using reflective devices, such as those disclosed in Non-Patent Document 2, could reproduce the reflection direction, they could not reproduce the delay profile. Furthermore, technologies using fading simulators, such as those disclosed in Patent Document 1, generate delay components using signal processing, requiring broadband analog-to-digital signal conversion or digital-to-analog signal conversion or high-speed digital signal processing, leading to increased costs due to the complexity of the processing. Therefore, there was a need for a low-cost and simple method for generating the desired delay profile.

[0007] The first aspect of this disclosure relates to a delay profile generation system. The delay profile generation system includes a receiving antenna configured to receive radio waves, a first cable with one end connected to the receiving antenna, and a transmitting antenna to which the other end of the first cable is connected and which is configured to transmit radio waves including signals transmitted from the first cable to the receiving antenna. In the delay profile generation system, the isolation between the transmitting antenna and the receiving antenna is configured to be variable.

[0008] A second aspect of this disclosure relates to a delay profile generation method that reproduces an arbitrary delay profile by connecting a receiving antenna and a transmitting antenna with a first cable, causing the receiving antenna to receive radio waves, causing the transmitting antenna to transmit radio waves containing signals transmitted from the receiving antenna via the first cable to the receiving antenna, and making the isolation between the transmitting antenna and the receiving antenna variable.

[0009] According to the delay profile generation technology of this disclosure, a signal propagates in a loop through a receiving antenna, a first cable, and a transmitting antenna. By configuring the isolation between the transmitting and receiving antennas to be variable, the amount of attenuation of the signal propagating in the loop with respect to the delay time can be adjusted. In this way, any delay profile can be reproduced. Furthermore, since signal processing such as analog-to-digital signal conversion, digital-to-analog signal conversion, and high-speed digital signal processing is not required to adjust the attenuation, any delay profile can be reproduced easily and at low cost.

[0010] This is a schematic diagram showing the configuration of the delay profile generation system in the first embodiment. This is a graph showing the delay profile reproduced by the delay profile generation system configuration. This is a schematic diagram showing the configuration of the delay profile generation system in the second embodiment. This is a schematic diagram showing the configuration of the delay profile generation system in the third embodiment.

[0011] Embodiments of this disclosure will be described with reference to the attached drawings.

[0012] 1. First Embodiment This disclosure provides a delay profile generation system capable of reproducing any delay profile with a simple configuration. Figure 1 is a schematic diagram showing the configuration of the delay profile generation system 1 in the first embodiment. The delay profile generation system 1 comprises a receiving antenna 11, a transmitting antenna 12, a cable 13 connecting the receiving antenna 11 and the transmitting antenna, and a variable amplifier 14 connected to the receiving antenna 11 and the transmitting antenna 12 via the cable 13. The cable 13 is an RF cable.

[0013] The receiving antenna 11 receives radio waves, converts the received signal into an electric current, and transmits it to the cable 13. The signal transmitted as an electric current to the cable 13 is amplified by the variable amplifier 14 and then transmitted to the transmitting antenna 12. The amount of amplification by the variable amplifier 14 can be controlled to be variable. The transmitting antenna 12 converts the signal transmitted from the cable 13 into radio waves and transmits them. The radio signal transmitted from the transmitting antenna 12 is then received again by the receiving antenna 11. In other words, when radio waves are input to the receiving antenna 11, the input signal propagates in a loop through the signal path formed by the receiving antenna 11, the cable 13, and the transmitting antenna 12.

[0014] As the signal loops through the signal path, delay and attenuation occur in the transmitted signal. The delay is fixed by the cable length of cable 13. The attenuation can be adjusted by making the isolation between the receiving antenna 11 and the transmitting antenna 12 variable. In this way, the delay profile generation system 1 allows the attenuation with respect to the delay time to be adjusted, and any desired delay profile can be reproduced.

[0015] The delay profile reproduced by the delay profile generation system 1 can be represented by the graph in Figure 2. The vertical axis represents the signal strength transmitted through the loop formed by the receiving antenna 11, cable 13, and transmitting antenna 12, and the horizontal axis represents the delay time after the signal is input to the receiving antenna 11.

[0016] As the signal input to the receiving antenna 11 travels through the loop of the signal path, a delay time of ΔT occurs for each loop. ΔT can be calculated from the cable length L of one loop, that is, the cable length L of cable 13, and the signal propagation speed v within cable 13. In other words, ΔT is a fixed value determined by the cable length L. Note that the delay occurring between the receiving antenna 11 and the transmitting antenna 12 is small compared to the delay caused by cable 13, and is therefore treated as negligible here.

[0017] The attenuation is determined by the isolation between the antennas, the gain of the variable amplifier 14, and the loss in the cable 13. If the isolation between the transmitting antenna 12 and the receiving antenna 11 is α [dB], the gain of the variable amplifier 14 is G [dB], and the cable loss per loop, that is, the loss that occurs when the signal is transmitted over the entire length of the cable 13, is β [dB], then the attenuation per loop is G - α - β.

[0018] Therefore, if P [dB] is the attenuation per ΔT of the delay profile to be reproduced, then the isolation α [dB] should be adjusted to satisfy the following equation (1). By adjusting the isolation between antennas, it becomes possible to reproduce any delay profile.

[0019]

[0020] Any method can be used to change the isolation between the antennas. For example, the isolation may be changed by changing the directional direction of at least one of the receiving antenna 11 and the transmitting antenna 12. Alternatively, the isolation may be changed by changing the distance between the receiving antenna 11 and the transmitting antenna 12. Alternatively, the isolation may be changed by inserting a shield between the receiving antenna 11 and the transmitting antenna 12, changing the type of shield inserted, or removing the shield. Alternatively, the isolation may be adjustable by arbitrarily combining the above three methods.

[0021] 2. Figure 3 of the second embodiment is a schematic diagram showing the configuration of the delay profile generation system 1 in the second embodiment. The delay profile generation system 1 is the same as in the first embodiment in that it comprises a receiving antenna 11, a transmitting antenna 12, a cable 13, and a variable amplifier 14, and the isolation between the transmitting antenna 12 and the receiving antenna 11 can be variably adjusted.

[0022] The delay profile generation system 1 further comprises two 4-port hybrid circuits. A receiving antenna 11 is connected to one input port of the first 4-port hybrid circuit 15, a cable 13 is connected to one output port, and a second cable 17 is connected to the other input port. The other output port is terminated. A transmitting antenna 12 is connected to one input port of the second 4-port hybrid circuit 16, a transmitting antenna 12 is connected to one output port, and a second cable 17 is connected to the other output port. The other input port is terminated. The second cable 17 is also an RF cable. In the following description, cable 13 will be referred to as the first cable to distinguish it from the second cable 17.

[0023] Furthermore, a variable attenuator 18 is connected to the output port of the second four-port hybrid circuit 16 and the input port of the first four-port hybrid circuit 15 via a second cable 17. The variable attenuator 18 can variably control the amount of attenuation of the signal transmitted from the output port of the second four-port hybrid circuit 16 to the input port of the first four-port hybrid circuit 15 via the second cable 17.

[0024] With the hybrid circuit inserted, the signal transmitted from the first cable 13 is split and output to the transmitting antenna 12 and the second cable 17, and the signal received by the receiving antenna 11 and the signal transmitted from the second cable 17 are added together and output to the first cable 13. In other words, similar to the first embodiment, the signal is configured to propagate in a loop within the signal path, but the loop branches midway, a portion of the signal propagating through the loop is attenuated by the isolation between the antennas, and the remaining signal is attenuated by the variable attenuator 18.

[0025] The delay time ΔT per loop when a signal propagates through a signal path in a loop is determined by the cable length L of the first cable 13. Since the cable length of the second cable 17 is shorter than that of the first cable, the delay caused by the second cable 17 is treated as negligible here.

[0026] Furthermore, the isolation between the receiving antenna 11 and the transmitting antenna 12 is α [dB], the cable loss per loop is β [dB], the gain in the variable amplifier 14 is G [dB], and the attenuation in the variable attenuator 18 is γ [dB]. β is the loss that occurs when the signal travels through the entire length of the first cable 13 and the entire length of the second cable 17. However, if the second cable 17 is sufficiently shorter than the first cable 13, β may be the cable loss that occurs when the signal travels through the entire length of the first cable 13.

[0027] If P [dB] is the attenuation per ΔT of the delay profile to be reproduced, then either or both of α [dB] and γ [dB] should be adjusted so that the relationship expressed by equation (2) is satisfied. In other words, in the second embodiment, the attenuation can be adjusted by both changing the isolation between antennas and changing the attenuation amount of the variable attenuator 18. In this way, any delay profile can be reproduced. Since the attenuation can also be changed by adjusting the attenuation amount of the variable attenuator 18, finer adjustment of the delay profile becomes possible.

[0028]

[0029] 3. Figure 4 of the third embodiment is a schematic diagram showing the configuration of the delay profile generation system 1 in the third embodiment. In the third embodiment, an E / O converter 19 is inserted between the receiving antenna 11 and the first 4-port hybrid circuit 15, and an O / E converter 20 is inserted between the second 4-port hybrid circuit 16 and the transmitting antenna 12. In addition, the first cable 13 and the second cable 17 are optical fiber cables.

[0030] In the third embodiment as well, the signal propagates by looping through the signal path, during which delay and attenuation occur. If ΔT is the delay time per loop when the signal propagates by looping through the signal path, then the delay time ΔT is determined by the length of the first cable 13. Let α [dB] be the isolation between the transmitting antenna 12 and the receiving antenna 11, β [dB] be the cable loss per loop, G [dB] be the gain of the variable amplifier 14, and γ [dB] be the attenuation by the variable attenuator 18. If P [dB] is the attenuation per ΔT of the delay profile to be reproduced, then the desired delay profile can be realized by adjusting both or either α and γ to satisfy the relationship in equation (2). In other words, as in the second embodiment, any delay profile can be reproduced by adjusting at least one of the following: adjusting the isolation between the antennas and adjusting the attenuation amount of the variable attenuator 18.

[0031] Furthermore, if the delay profile generation system 1 includes a variable amplifier 14, the amount of attenuation in the desired delay profile may be achieved by adjusting the gain G of the variable amplifier 14 in addition to α and γ. The same applies to the first and second embodiments.

[0032] However, in the third embodiment, the variable amplifier 14 is not an essential component. The signal received by the receiving antenna 11 is converted to end-of-service (E / O) and propagated through the optical fiber cable, generating a delay. Then, it is converted to end-of-service (O / E) again and transmitted from the transmitting antenna. The cable loss β generated at this time is fixed by the length of the first cable 13, but by using an optical fiber cable for the first cable 13, the fixed cable loss can be greatly reduced. If the cable loss β is sufficiently small, the delay profile generation system 1 may be configured without the variable amplifier 14. By omitting the variable amplifier 14, it becomes possible to reproduce any delay profile with a simpler configuration. In this case, α and γ are variably adjusted so that the relationship in the following equation (3) is satisfied.

[0033]

[0034] Furthermore, the first and third embodiments can be combined. That is, in the configuration of Figure 1, the first cable 13 may be an optical fiber cable. Then, the signal output from the receiving antenna 11 may be converted to E / O, propagated through the first cable 13 to generate a delay, and then converted to O / E before being transmitted from the transmitting antenna 12. In this case as well, if the cable loss β of the first cable 13 is sufficiently small, the configuration can be made without the variable amplifier 14.

[0035] 4. Effects The three embodiments of the delay profile generation system 1 have been described above. In this way, the delay profile generation system 1 is configured so that the signal forms a loop with at least the receiving antenna 11, the first cable 13, and the transmitting antenna 12. The amount of attenuation corresponding to the delay in the propagation environment attenuation model to be reproduced is variably adjusted by adjusting at least one of the isolation between antennas, the attenuation amount of the variable amplifier 14, and the gain of the variable amplifier 14. Since there is no need to perform analog-to-digital signal conversion or digital-to-analog signal conversion in the generation of the delay profile, it is possible to realize the desired delay profile at low cost with a simple configuration.

[0036] 1. Delay profile generation system 11. Receiving antenna 12. Transmitting antenna 13. First cable 14. Variable amplifier 15. First 4-port hybrid circuit 16. Second 4-port hybrid circuit 17. Second cable 18. Variable attenuator 19. E / O converter 20. O / E converter

Claims

1. A delay profile generation system comprising: a receiving antenna configured to receive radio waves; a first cable with one end connected to the receiving antenna; and a transmitting antenna to which the other end of the first cable is connected, and which is configured to transmit radio waves including signals transmitted from the first cable to the receiving antenna, wherein the isolation between the transmitting antenna and the receiving antenna is variable.

2. A delay profile generation system according to claim 1, further comprising a variable amplifier connected to the receiving antenna and the transmitting antenna via the first cable, which can control the amount of amplification of the signal transmitted from the receiving antenna to the transmitting antenna.

3. A delay profile generation system according to claim 1 or 2, further comprising: a first four-port hybrid circuit in which the receiving antenna is connected to one input port and the first cable is connected to one output port; a second four-port hybrid circuit in which the transmitting antenna is connected to one output port and the first cable is connected to one input port; a second cable connecting the other output port of the second four-port hybrid circuit to the other input port of the first four-port hybrid circuit; and a variable attenuator connected via the second cable to the other output port of the second four-port hybrid circuit and the other input port of the first four-port hybrid circuit, and capable of controlling the amount of attenuation of the signal transmitted from the other output port of the second four-port hybrid circuit to the other input port of the first four-port hybrid circuit.

4. A delay profile generation system according to claim 1 or 2, wherein at least the first cable is an optical fiber cable.

5. A delay profile generation system according to claim 1 or 2, wherein the isolation between the receiving antenna and the transmitting antenna is made variable by at least one of the following: changing the directional direction of at least one of the receiving antenna and the transmitting antenna; changing the distance between the receiving antenna and the transmitting antenna; and inserting a shield between the receiving antenna and the transmitting antenna.

6. A delay profile generation system according to claim 2, wherein an arbitrary delay profile is reproduced by the sum of the isolation between the transmitting antenna and the receiving antenna and the attenuation generated by the first cable and the difference in the amount of amplification by the variable amplifier.

7. A delay profile generation system according to claim 3, wherein the first cable and the second cable are RF cables.

8. A delay profile generation method that reproduces an arbitrary delay profile by connecting a receiving antenna and a transmitting antenna with a first cable, causing the receiving antenna to receive radio waves, causing the transmitting antenna to transmit radio waves including the signal transmitted from the receiving antenna via the first cable to the receiving antenna, and varying the isolation between the transmitting antenna and the receiving antenna.

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