FM weak field strength wireless device using multiple antennas

Abstract

A low field strength wireless device comprises an FM transmitter that generates and outputs an FM transmission signal; a distributor that calculates a transmission output conforming to the FM low field strength technical standards, generates a control signal representing the calculated transmission output, and distributes the FM transmission signal according to the control signal; at least one coaxial cable connected to the distributor to receive the FM transmission signal; and at least one transmitting antenna connected to the at least one coaxial cable to transmit the FM transmission signal. Accordingly, the present invention provides a low field strength wireless device that is expected to play a very important role in realizing an environment where a radio station can be established in the FM broadcast band with a low field strength at drive-in theaters, small-scale religious and cultural events, etc., solely through radio certification without a radio station license.

Description

Technology Field

[0001] The present invention relates to a low electric field strength wireless device using multiple transmitting antennas in the FM broadcast band. Background Technology

[0002] With the advancement of information and communication technology and socioeconomic development, the demand for the use of radio waves is rapidly increasing. Among these radio wave utilization systems, there is growing interest in low-field strength wireless devices that use significantly weak radio waves to provide a service area within a narrow range for daily life.

[0003] The term "weak electric field strength wireless device" refers to a wireless device that satisfies the allowable electric field strength measured at a distance of several meters from the wireless device. This wireless equipment is expected to play a very important role in realizing a ubiquitous environment, and its scope of use is expected to increase in various ways in the future.

[0004] For low-field strength wireless devices, provided they satisfy the technical standards within the relevant frequency bands regulated by each country, the output used is limited to the upper limit of the standard field strength, regardless of the application. Since they use significantly less output than low-power wireless devices, they can be defined as wireless equipment of a distinct concept. The characteristics of low-field strength wireless devices are as follows.

[0005] 1. Anyone can use it without a license.

[0006] 2. It can be freely configured according to the intended use, such as a duplex method or a multi-channel system.

[0007] 3. Except for specific frequency bands, frequency bands can be freely selected and changed.

[0008] For low-field strength wireless devices, the standard value of the electric field strength is small, so the service area radius varies depending on the frequency band used or the characteristics of the receiver, but is typically within 20 to 30 m.

[0009] The electric field strength standards for such low-field strength wireless devices are significantly lower than those for Electromagnetic Compatibility (EMC) registration, which specifies the upper limits for unwanted emissions from electronic products rather than wireless equipment. Considering this in reality, the use of low-field strength wireless devices is very difficult. Consequently, these unrealistic factors are acting as obstacles to the development of low-field strength wireless devices.

[0010] In addition, due to the recent impact of COVID-19, non-face-to-face religious and cultural events using FM radio in cars have increased rapidly. Although FM radio frequencies (88–108 MHz) are being used to transmit movie sound to vehicles at drive-in theaters, facility owners are required to apply for a license to open an FM radio station and obtain a license renewal every year, resulting in economic costs and inconvenience.

[0011] Therefore, there is a need for technology that allows the use of FM radio frequencies without a wireless station establishment license in small-scale, non-face-to-face locations utilizing car radio, such as drive-in theaters. The problem to be solved

[0012] Taking into account the above points, the present invention aims to provide a low electric field strength wireless device that is expected to play a very important role in realizing a ubiquitous environment.

[0013] In addition, the present invention aims to provide an FM multi-antenna low-field strength wireless device that enables the use of FM radio frequencies without a wireless station establishment permit in small-scale, non-face-to-face locations utilizing car radio, such as drive-in theaters. means of solving the problem

[0014] A low electric field strength wireless device according to one aspect of the present invention comprises an FM transmitter that generates and outputs an FM transmission signal; a distributor that calculates a transmission output conforming to an FM low electric field strength technical standard, generates a control signal representing the calculated transmission output, and distributes the FM transmission signal according to the control signal; at least one coaxial cable connected to the distributor to receive the FM transmission signal; and at least one transmitting antenna connected to the at least one coaxial cable to transmit the FM transmission signal.

[0015] The above distributor can calculate the transmission output according to the following mathematical formula.

[0016] Maximum transmit power (eirp) = Feed line power (Pt) + Antenna gain (Gi)

[0017] The above splitter can calculate the transmission output by considering the feed line output and antenna gain. Effects of the invention

[0018] The present invention can provide a weak electric field strength wireless device that is expected to play a very important role in realizing a ubiquitous environment.

[0019] In addition, according to the present invention, facility owners can rapidly establish an FM transmission network at drive-in theaters, performances, or religious services without obtaining a wireless station establishment permit or filing a notification, thereby reducing economic costs and time required.

[0020] In particular, it is possible to rapidly establish contactless activities utilizing automobiles during pandemics such as COVID-19. Brief explanation of the drawing

[0021] FIG. 1 is a diagram showing the configuration of a wireless device system for testing the coverage of a low electric field strength wireless device using multiple transmitting antennas in the FM broadcast band according to the present invention. FIG. 2 is a block diagram of a weak electric field strength wireless device according to one embodiment of the present invention. Figure 3 is a diagram showing a scenario according to the transmission antenna configuration. Figure 4 is a diagram showing the measurement location and measurement point when installing a transmitting antenna configured according to the scenario of Figure 3. Figure 5 is a diagram showing specific examples of measurement locations and measurement points when installing a transmitting antenna. Figure 6 is a schematic diagram showing the coverage when three transmitting antennas are installed at a height of 3 meters in the scenario of Figure 3. Specific details for implementing the invention

[0022] The present invention is susceptible to various modifications and may have various embodiments; specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. Similar reference numerals have been used for similar components in the description of each drawing.

[0023] Terms such as first, second, A, B, etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0024] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0025] The terms used herein are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. Terms related to “comprising,” “having,” etc. in this specification are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0026] Unless otherwise defined in this specification, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted in a meaning consistent with their contextual meaning in the relevant technology and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this specification.

[0027] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0028] FIG. 1 is a diagram showing the configuration of a wireless device system for testing weak electric field strength wireless device coverage using multiple transmitting antennas in the FM broadcast band according to the present invention.

[0029] As described above, low-field strength wireless devices use significantly weak radio waves, and their service area is limited to a narrow range in daily life. In real-world environments, such as drive-in theaters and drive-in events for religious services that utilize low-field strength wireless devices by using multiple transmitting antennas, the wireless device system (1000) needs to verify the available coverage.

[0030] To this end, the wireless device system (1000) includes a low electric field strength wireless device (100) and a receiving device (200). The low electric field strength wireless device (100) must transmit an FM transmission signal with a transmission output that meets the electric field strength standards stipulated by each country.

[0031] The receiving device (200) can receive an FM transmission signal transmitted by a low electric field strength wireless device (100). The receiving device (200) must receive an FM transmission signal of 500 μV / m (54 dBuV / m) or less at a distance of 3 m according to the FM low electric field technical standards. That is, according to the FM low electric field technical standards, if the requirement of 500 μV / m (54 dBuV / m) or less at a distance of 3 m is satisfied, a wireless station can be established without reporting.

[0032] To this end, the weak electric field strength wireless device (100) must determine the transmission output so that the receiving device (200) receives an FM transmission signal of 500 μV / m (54 dBuV / m) or less at a distance of 3 m.

[0033] FIG. 2 is a block diagram of a weak electric field strength wireless device according to one embodiment of the present invention.

[0034] Referring to FIG. 2, a low electric field strength wireless device (100) includes an FM transmitter (120), a splitter (130), at least one coaxial cable (150), and at least one transmitting antenna (160). The FM transmitter (120) and the splitter (130) can form a transmitting device (140).

[0035] The FM transmitter (120) generates and outputs an FM transmission signal. Specifically, the FM transmitter (120) generates an FM transmission signal using FM (Frequency Modulation) and outputs it to the distributor (130).

[0036] The distributor (130) calculates a transmission output that conforms to the FM weak electric field strength technical standard, generates a control signal representing the calculated transmission output, and distributes the FM transmission signal according to the control signal. The distributor (130) can calculate the transmission output according to the weak electric field technical standard by considering the transmission specifications, such as feed line output and antenna gain.

[0037] Specifically, the splitter (130) generates a control signal indicating a transmission output that meets the FM weak field strength technical standard. The maximum transmission output (eirp) that meets the FM weak field strength technical standard can be -41 dBm (75 nW) assuming free-space loss.

[0038] In other words, to satisfy the FM weak field technical standards, the maximum transmit power (EIRP) can be configured so that it does not exceed 75nW by calculating the antenna gain, distribution loss, and cable loss values.

[0039] This maximum transmission power (eirp) can be calculated as shown in the following mathematical formula 1.

[0040]

[0041] Therefore, if the maximum transmit power (eirp) is -41 dBm (75 nW) and the antenna gain (Gi) is -4.5 dBi, the feed line power (Pt) can be -35.5 dBm (-41 dBm = -36.5 dBm + -4.5 dBi).

[0042] The splitter (130) can calculate the transmission output by taking into account the distribution loss of the splitter (130) and the coaxial cable loss of the coaxial cable (150). The distribution loss may be, for example, 13 dB, and the coaxial cable loss may be, for example, 15 dB per 100m.

[0043] In this case, the distributor (130) can generate a control signal indicating a transmission output such that the feed line output (Pt) becomes -35.5 dBm.

[0044] The splitter (130) outputs an FM transmission signal to the coaxial cable (150) with a transmission output determined according to a control signal. That is, the splitter (130) distributes the FM transmission signal to at least one coaxial cable (150).

[0045] At least one transmitting antenna (160) is connected to a coaxial cable (150). Multiple transmitting antennas (160) may be installed depending on the site size. When transmitting FM transmission signals through multiple transmitting antennas (160), multiple coaxial cables (150) connected to each of the multiple transmitting antennas (160) may be provided. Accordingly, the FM transmission signal provided to the coaxial cable (150) is transmitted through the transmitting antenna (160) connected to the corresponding coaxial cable (150).

[0046] In addition, to minimize the phase difference of signals simultaneously transmitted by multiple antennas, the transmission cables from the splitter to the antennas can be configured to have the same length, and the multiple antennas can be manufactured with the same characteristics.

[0047] In this way, FM transmission signals transmitted through multiple transmitting antennas (160) can be received through a receiving device (200).

[0048] When transmitting an FM transmission signal through a single or multiple transmitting antennas (160), it is necessary to verify whether coverage is available in a real environment, such as a drive-in theater, a religious event, or a drive-in for a cultural event. To this end, the receiving device (200) may include a vehicle radio / spectrum analyzer.

[0049] A test to verify the coverage of the weak electric field strength wireless device (100) according to the present invention can be performed.

[0050] The weak electric field strength wireless device (100) transmitted an FM transmission signal having a transmission frequency of 100.3 MHz with a transmission output of 75 nW (-41 dBm).

[0051] In this case, after installing a single or multiple transmitting antennas, the audible range can be verified and the signal strength measured using a vehicle radio / spectrum analyzer.

[0052] FIG. 3 is a diagram showing a scenario according to the configuration of a transmitting antenna, and FIG. 4 is a diagram showing the measurement location and measurement point when the transmitting antenna is installed according to the scenario of FIG. 3. FIG. 5 is a diagram showing specific examples of the measurement location and measurement point when the transmitting antenna is installed.

[0053] Referring to FIGS. 3 to 5, a single transmitting antenna was installed at various heights, and the reception level and sound quality of the FM transmitting signal were evaluated at 121 measurement points. In addition, multiple transmitting antennas were installed at multiple points at various heights, and the reception level and sound quality of the FM transmitting signal were evaluated at 121 measurement points.

[0054] The result of receiving the FM transmission signal at the receiving device (200) is as shown in Table 1 below.

[0055]

[0056] Referring to Table 1 above, it can be seen that when using a single transmitting antenna, the audible range covers only a part of the area (radius 30~40m), but when using multiple transmitting antennas, the entire area (100m × 100m) is covered (59%→100%). The reception level is generally low due to the characteristics of the weak electric field strength wireless device (100) which transmits low output (75nW -41dBm), so the reception level can be secured by using multiple transmitting antennas (45%→98%).

[0057] According to the above test, the audible range is difficult to achieve with only one antenna in venues such as drive-in worship services and drive-in theaters (100m × 100m), and it is necessary to install multiple antennas (2 to 8) to secure coverage.

[0058] Since the audible reception level is low—similar to the instrument noise level (-90 to -100 dBm)—it is vulnerable to interference, so it is necessary to minimize the influence of ambient noise. Additionally, while reception gain can be secured through signal superposition when using multiple antennas, sound quality may suddenly deteriorate at certain points; therefore, it is necessary to move the vehicle slightly (20–75 cm) to improve sound quality.

[0059] Table 2 below shows the analysis of results according to antenna configuration scenarios.

[0060]

[0061] Referring to Table 2 above, in coverage measurements using a single antenna, when the antenna height of the single antenna increases (3m→9m), the ratio of good sound quality increases (59%→79%), but the ratio of the reception limit level actually decreases (49%→45%). In addition, the influence of propagation characteristics such as ground reflections and vertical radiation patterns can be estimated depending on the height of the transmitting antenna.

[0062] In coverage measurements using multiple antennas, it can be confirmed that coverage is expanded compared to a single antenna (good sound quality increases to 59%, 82%, and 100% when using 1, 3, or 4 antennas at a height of 3m). When the reception level and distance between two signals from two transmitting antennas are similar, it can be confirmed that the reception gain increases or decreases or the sound quality deteriorates.

[0063] Figure 6 is a schematic diagram showing the coverage when three transmitting antennas are installed at a height of 3 meters in the scenario of Figure 3.

[0064] Referring to Fig. 6, the area marked in red is where the transmitting antenna is installed, and the area marked in blue is where good sound quality (good sound quality grade 3 or higher) is received. In other words, it can be seen that a signal of good quality is received at 99 out of 121 measurement locations.

[0065] According to the measurement results above, when using a single antenna, it is necessary to set the antenna height by considering field conditions such as ground reflection and antenna radiation pattern, rather than simply increasing the antenna height to expand coverage.

[0066] In addition, when using multiple antennas, if the reception level and distance between the two signals at the reception point are similar, the sound quality may suddenly deteriorate, so it is necessary to move the vehicle slightly (20–75 cm) to receive the signal.

[0067] Since the position of the vehicle radio reception antenna may change depending on the vehicle's direction of travel, it is necessary to analyze the reception sound quality evaluation based on the vehicle's direction.

[0068] Table 3 below shows the reception rate of FM transmission signals according to the direction of the vehicle.

[0069]

[0070] Referring to Table 3 above, it can be seen that when the transmitting antenna height is 3m, rear vehicle reception (30 / 55 units) is better (55% → 60%) than front reception (33 / 55 units).

[0071] In addition, when the transmitting antenna height is 9m, it can be seen that rear vehicle reception (53 / 55 units) is better (58% → 96%) than front vehicle reception (32 / 55 units). When the transmitting antenna height is typical (3m), the front and rear radio reception rates were similar (55% → 60%), but when the transmitting antenna height is increased (9m), the reception rate of rear vehicle reception increases compared to front vehicle reception (58% → 96%).

[0072] As can be seen from the measurement data in Table 3 above, the radio reception rate varies depending on the direction of the transmitting antenna and the vehicle, so it is necessary to install the transmitting antenna considering the direction of the stage and the direction of the vehicle.

[0073] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0074] Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention; thus, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application. Explanation of the symbols

[0075] 120: FM Transmitter 130: Distributor 150: Coaxial cable 160: Antenna

Claims

Claim 1 A low-field strength wireless device comprising: an FM transmitter that generates and outputs an FM transmission signal; a splitter that calculates a maximum transmission output, generates a control signal representing the calculated maximum transmission output, and distributes the FM transmission signal according to the control signal; at least one coaxial cable connected to the splitter to receive the FM transmission signal; and at least one transmitting antenna connected to the at least one coaxial cable to transmit the FM transmission signal; wherein the splitter calculates the maximum transmission output according to the following mathematical formula, taking into account the feed line output and antenna gain. Maximum transmission output (eirp) = Feed line output (Pt) + Antenna gain (Gi) Claim 2 delete Claim 3 delete

Images