Wireless device test system

Abstract

To provide a radio equipment test system capable of accurately measuring the reflected wave power of an antenna.SOLUTION: A radio device test system 100 includes a power amplifier 136 that power-amplifies a high-frequency signal from a signal generator 134, a pseudo antenna 130 that has a variable voltage standing wave ratio and is connected to a coaxial cable 112 in place of an antenna 102, a directional coupler 138 that is connected between the power amplifier and the pseudo antenna, couples the high-frequency signal to the pseudo antenna, and outputs traveling wave power and reflected wave power between the power amplifier and the pseudo antenna, and a power measuring device 140 and a control device 110 that are connected to a subsequent stage of the directional coupler. The control device calculates a correlation coefficient between the progressive wave power and the reflected wave power of the pseudo antenna for each voltage standing wave ratio of the pseudo antenna, and calculates the reflected wave power of the antenna by correcting the progressive wave power and the reflected wave power measured by the power measuring instrument with the correlation coefficient in a state where the pseudo antenna is replaced with the antenna.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a radio test system. [Background technology]

[0002] For example, a radio test may be performed by attaching an antenna to a test carriage that simulates a vehicle, and feeding power from a radio transmitter to the antenna via a coaxial cable.

[0003] Patent Document 1 describes a transmitter for emitting radio waves via an antenna. This transmitter includes a power amplifier that receives a high-frequency signal and amplifies its power, a directional coupler that couples the amplified high-frequency signal to the antenna, a voltage-variable attenuator connected before the power amplifier, and a control device. The directional coupler detects the forward wave power and reflected wave power between the power amplifier and the antenna and outputs the detected power to the control device.

[0004] The control device determines whether the transmitter is in a stable operating state based on the value of the forward wave power, calculates a voltage standing wave ratio based on the values ​​of the forward wave power and the reflected wave power, and compares the voltage standing wave ratio with a threshold value to control the power amplification of the high-frequency signal in the power amplifier section.

[0005] The transmitter in Patent Document 1 reduces the output before the transmitter reaches the specified output, preventing the level of reflected wave power input to the power amplifier from exceeding the allowable value even for an instant, thereby eliminating unnecessary reductions or stops in the output of the transmission power amplifier and enabling more stable transmission operation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-35703 Summary of the Invention [Problem to be solved by the invention]

[0007] The above radio test is preferably carried out by accurately measuring the reflected wave power of an antenna connected to a coaxial cable and feeding the antenna the effective power (net power) obtained by subtracting the reflected wave power from the forward wave power.

[0008] However, when high-frequency power from a wireless transmitter is transmitted through the inner conductor of a coaxial cable to supply power to the antenna under test, if reflection occurs at the antenna's power feed point, the reflected power from the antenna is transmitted through the outer conductor of the coaxial cable and transmitted to the wireless transmitter. Furthermore, since the outer conductor of the coaxial cable is grounded or earthed, it is difficult to accurately measure the reflected power at a location far from the antenna's power feed point.

[0009] The transmitter in Patent Document 1 simply controls the power amplifier based on the voltage standing wave ratio calculated from the values ​​of the forward wave power and reflected wave power output from the directional coupler, and does not take into consideration the transmission loss of the reflected wave power of the antenna connected to the coaxial cable. Therefore, even if you try to apply the transmitter in Patent Document 1 to the above-mentioned wireless device test, you will not be able to accurately measure the reflected wave power of the antenna being tested.

[0010] In view of the above, an object of the present invention is to provide a radio equipment test system that can accurately measure the reflected wave power of an antenna. [Means for solving the problem]

[0011] In order to solve the above problem, a representative configuration of a radio device test system according to the present invention is a radio device test system including an antenna connected to a coaxial cable, the radio device test system further including: a signal generator that generates a high frequency signal; a power amplifier that power-amplifies the high frequency signal; a dummy antenna that has a variable voltage standing wave ratio, which indicates the transmission efficiency of high frequency power, and is connected to the coaxial cable in place of the antenna; a directional coupler that is connected between the power amplifier and the dummy antenna and couples the power-amplified high frequency signal to the dummy antenna and outputs forward wave power and reflected wave power between the power amplifier and the dummy antenna; a power meter that is connected downstream of the directional coupler and measures the forward wave power and reflected wave power output from the directional coupler; and a control device that calculates the reflected wave power of the antenna, wherein the control device has a correlation coefficient calculation unit that calculates a correlation coefficient between the forward wave power and reflected wave power of the dummy antenna for each voltage standing wave ratio of the dummy antenna and the forward wave power and reflected wave power measured by the power meter; and a power value calculation unit that calculates the reflected wave power of the antenna by correcting the forward wave power and reflected wave power measured by the power meter with the dummy antenna replaced with the antenna by the correlation coefficient. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a radio equipment test system that can accurately measure the reflected wave power of an antenna. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a functional block diagram of a radio equipment test system according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram illustrating an antenna and a coaxial cable of the radio equipment test system of FIG. [Figure 3] FIG. 2 is a diagram illustrating a main part of the radio equipment test system of FIG. [Figure 4] 2 is a flowchart showing a procedure for a radio test using the radio test system of FIG. 1. [Figure 5]FIG. 4 is a diagram showing a state in which an antenna is connected to a coaxial cable instead of the dummy antenna in the radio equipment test system of FIG. [Figure 6] FIG. 10 is a diagram illustrating a modified example of a radio equipment test system. [Figure 7] FIG. 7 is a diagram showing a state in which an antenna is connected to a coaxial cable instead of the dummy antenna in the radio equipment test system of FIG. 6. [Figure 8] FIG. 6 is a diagram illustrating a modification of the radio equipment test system of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Dimensions, materials, and other specific values ​​shown in the embodiments are merely examples for facilitating understanding of the invention and, unless otherwise specified, do not limit the present invention. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0015] a directional coupler connected between the power amplifier and the pseudo antenna and coupling the power-amplified radio frequency signal to the pseudo antenna and outputting forward wave power and reflected wave power between the power amplifier and the pseudo antenna; a power meter connected downstream of the directional coupler and measuring the forward wave power and reflected wave power output from the directional coupler; and a control device that calculates the reflected wave power of the antenna, wherein the control device further comprises: a correlation coefficient calculation unit that calculates a correlation coefficient between the forward wave power and reflected wave power of the pseudo antenna for each voltage standing wave ratio of the pseudo antenna and the forward wave power and reflected wave power measured by the power meter; and a power value calculation unit that calculates the reflected wave power of the antenna by correcting, by the correlation coefficient, the forward wave power and reflected wave power measured by the power meter with the pseudo antenna replaced with the antenna.

[0016] In the above configuration, a pseudo antenna (e.g., a variable impedance terminator) that can change the voltage standing wave ratio is connected to the coaxial cable prior to the antenna under test, a directional coupler is connected between the power amplifier and the pseudo antenna, and a power meter is connected after the directional coupler.

[0017] The control device measures the forward and reflected power of the pseudo antenna and the power meter for each voltage standing wave ratio of the pseudo antenna, and calculates a correlation coefficient that indicates the strength of the correlation between the power values ​​by creating a correction curve based on each power value. Then, with the antenna under test connected to the coaxial cable instead of the pseudo antenna, the control device can calculate the reflected power of the antenna by correcting the forward and reflected power measured by the power meter with the correlation coefficient.

[0018] The power value calculation unit calculates net power, which is effective power, by subtracting the calculated reflected wave power from the forward wave power of the antenna, and the control device may further have a control unit that controls the output of the signal generator so as to supply net power to the antenna.

[0019] This not only allows the reflected wave power of the antenna to be calculated, but also allows the radio equipment test to be performed with net power being supplied to the antenna.

[0020] The radio device testing system may further include an attenuator connected between the directional coupler and the dummy antenna via a selector to attenuate reflected power from the dummy antenna and output the attenuated power to the power amplifier, and a filter to remove high-frequency components from the reflected power or to match the impedance of the high-frequency power transmission line, and the control unit may switch the selector to connect the attenuator or the filter between the directional coupler and the dummy antenna.

[0021] In this way, since an attenuator or a filter can be connected between the directional coupler and the dummy antenna, it is possible to prevent the power amplifier from being destroyed by the reflected wave power from the dummy antenna.

[0022] The above-mentioned radio device testing system may further include another directional coupler connected directly below the antenna for coupling a low-frequency band signal to the antenna and outputting forward wave power and reflected wave power, and another power meter connected downstream of the other directional coupler for measuring the forward wave power and reflected wave power output from the other directional coupler.

[0023] When a low-frequency band signal (e.g., 3M-30MHz) is transmitted over a coaxial cable in this way, the reflected wave power of the antenna can be accurately measured by connecting another directional coupler directly below the antenna and connecting another power meter after the other directional coupler. [Example]

[0024] 1 is a functional block diagram of a radio equipment test system 100 according to an embodiment of the present invention. The radio equipment test system 100 is a system that supplies power to an antenna 102 under test to perform a radio equipment test, and includes a test bogie 104 simulating a vehicle, a test system rack 106, and a control device 110 installed in a measurement room 108.

[0025] The antenna 102, test cart 104, and test system rack 106 are electrically connected by a coaxial cable 112 used as a transmission line, and are further installed in an anechoic chamber 114 to verify the effects of electromagnetic waves radiated from the antenna 102. The antenna 102 is also attached to the test cart 104.

[0026] The control device 110 is connected to the test cart 104 and the test system rack 106 via a control signal cable 116 indicated by a dotted line in the figure. The control device 110, which will be described in detail later, has a control unit 118, a correlation coefficient calculation unit 120, a storage unit 122, a power value calculation unit 124, and an operation unit 126, which are connected via an internal bus 128.

[0027] Figure 2 is a schematic diagram illustrating the antenna 102 and coaxial cable 112 of the radio device test system 100 of Figure 1. Figure 2(a) schematically illustrates a radio device test in which power is supplied from an existing radio transmitter 200 to the antenna 102, which is a load, via the coaxial cable 112. Figure 2(b) shows the internal structure of the coaxial cable 112.

[0028] The coaxial cable 112 has a circular cross section and is composed of four layers, namely, an inner conductor 112a, an insulator 112b, an outer conductor 112c, and an outer coating 112d, which are concentrically stacked as shown in Figure 2(b). The inner conductor 112a is a copper wire located at the center of the circular cross section and transmits electrical signals. The insulator 112b is an insulating layer that surrounds the inner conductor 112a.

[0029] The outer conductor 112c of the coaxial cable 112 is a braided or meshed wire that surrounds the outside of the insulator 112b, and serves as a ground or earth during transmission, providing a shielding effect to prevent signal leakage to the outside and radio waves from entering from the outside. The outer sheath 112d is a jacket also known as vinyl or protective sheath, and is the outermost protective cover of the coaxial cable 112.

[0030] 2(a), when high-frequency power from wireless transmitter 200 is transmitted through inner conductor 112a of coaxial cable 112 to supply power to antenna 102 under test, traveling power Pf is transmitted toward antenna 102. However, if reflection occurs at the feed point of antenna 102, reflected power Pr of antenna 102 is conducted through outer conductor 112c of coaxial cable 112 and transmitted to the wireless transmitter 200 side. However, because outer conductor 112c of coaxial cable 112 is grounded or earthed, it is difficult to accurately measure the reflected power at a position away from the feed point of antenna 120.

[0031] Therefore, the radio equipment test system 100 is configured to accurately measure the reflected wave power of the antenna 102 connected to the coaxial cable 112, and feed the net power obtained by subtracting the reflected wave power from the forward wave power to the antenna 102, thereby enabling radio equipment testing.

[0032] Fig. 3 is a diagram showing the main components of the radio device test system 100 of Fig. 1. The radio device test system 100 includes a dummy antenna 130. The dummy antenna 130 is a variable impedance terminator that can vary the voltage standing wave ratio (VSWR), which indicates the transmission efficiency of high-frequency power. The dummy antenna 130 is connected to a coaxial cable 112 and attached to a test bogie 104 prior to the antenna 102 under test.

[0033] The dummy antenna 130 is set with a plurality of (for example, three) voltage standing wave ratios, and a plurality of voltage standing wave ratios can be selected by switching the selector 132. The voltage standing wave ratio VSWR can be calculated using the following equation (1) based on the forward wave power Pf and the reflected wave power Pr.

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[0034] The test system rack 106 is equipped with a signal generator 134, a power amplifier 136, a directional coupler 138, and a power meter 140. The signal generator 134 generates a high-frequency signal, and the output thereof is controlled by the control unit 118 (see FIG. 1) of the control device 110. The power amplifier 136 amplifies the power of the high-frequency signal output from the signal generator 134.

[0035] The directional coupler 138 is connected between the power amplifier 136 and the dummy antenna 130. The directional coupler 138 also couples the power-amplified high-frequency signal to the dummy antenna 130, and extracts and outputs the forward power Pf and the reflected power Pr between the power amplifier 136 and the dummy antenna 130. The power meter 140 is connected downstream of the directional coupler 138, and measures the forward power Pf and the reflected power Pr output from the directional coupler 138.

[0036] The test vehicle 104 is equipped with an attenuator 142, a filter 144, and selectors 146 and 148. The attenuator 142 and the filter 144 are connected between the directional coupler 138 and the dummy antenna 130 via the selectors 146 and 148, as shown in the figure. The attenuator 142 attenuates the reflected power Pr from the dummy antenna 130 and outputs the attenuated power to the power amplifier 136. The filter 144 removes high-frequency components from the reflected power Pr or matches the impedance of the transmission line for the high-frequency power.

[0037] 1 switches between selectors 146 and 148 to connect attenuator 142 or filter 144 between directional coupler 138 and dummy antenna 130. This prevents power amplifier 136 from being destroyed by reflected wave power Pr from dummy antenna 130.

[0038] Fig. 4 is a flowchart showing the procedure for testing a radio device using the radio device test system 100 of Fig. 1. First, as shown in Fig. 3, a dummy antenna 130 is connected to the coaxial cable 112 prior to the antenna 102 to be tested (step S100).

[0039] Next, the correlation coefficient calculation unit 120 of the control device 110 measures and acquires the forward wave power Pf and reflected wave power Pr at the dummy antenna 130 for each voltage standing wave ratio (each power reflectivity) of the dummy antenna 130, and the forward wave power Pf and reflected wave power Pr measured by the power meter 140 (step S102). The voltage standing wave ratio of the dummy antenna 130 can be appropriately selected, for example, by the control unit 118 switching the selector 132. Furthermore, the control unit 118 controls the output of the signal generator 134 to change the frequency of the high-frequency signal, and the process of step S102 can be performed for each frequency to acquire multiple power values. These acquired multiple power values ​​are stored in the memory unit 122 by the correlation coefficient calculation unit 120.

[0040] Next, the correlation coefficient calculation unit 120 reads out each power value acquired in step S102, i.e., the forward wave power Pf and reflected wave power Pr at the pseudo antenna 130 and the power meter 140 for each voltage standing wave ratio, from the storage unit 122, and calculates a correlation coefficient indicating the strength of the correlation between the power values ​​by, for example, creating a correction curve based on each power value (step S104).The correlation coefficient calculation unit 120 also stores the calculated correlation coefficient in the storage unit 122.

[0041] In this way, in the radio device test system 100, it is possible to know in advance, by using an index called a correlation coefficient, how much the reflected wave power of the artificial antenna 130, which has a preset voltage standing wave ratio, will attenuate before reaching the power meter 140, which is connected downstream of the directional coupler 138.

[0042] 5 (step S106), the antenna 102 is connected to the coaxial cable 112 instead of the dummy antenna 130. In this manner, the antenna 102 to be tested is attached to the test cart 104.

[0043] Fig. 5 is a diagram showing a state in which an antenna 102 is connected to a coaxial cable 112 instead of the dummy antenna 130 in the radio device test system 100 of Fig. 3. In the radio device test system 100 shown in Fig. 5, power is supplied to the antenna 102 under test, and the forward power Pf and reflected power Pr are measured by a power meter 140.

[0044] Next, the power value calculation unit 124 reads the correlation coefficient from the storage unit 122 and calculates the reflected power of the antenna 102 by correcting the forward power Pf and the reflected power Pr measured by the power meter 140 with the correlation coefficient (step S108). Note that the processes of steps S102, S104, and S108 can be executed as appropriate by signals input from the operation unit 126 of the control device 110.

[0045] In this way, in the radio device test system 100, prior to the measurement of the antenna 102, a correlation coefficient is calculated between the power value of the power meter 140 downstream of the directional coupler 138 and the power value of the dummy antenna 130, in a preliminary measurement using the dummy antenna 130, which has a variable voltage standing wave ratio. Then, by correcting the power value of the power meter 140 when power is supplied to the antenna 102 using the correlation coefficient, the reflected wave power of the antenna 102 can be measured accurately.

[0046] Furthermore, after step S108, the power value calculation unit 124 calculates the net power, which is the effective power, by subtracting the reflected wave power Pr of the antenna 102 calculated in step S108 from the forward wave power Pf of the antenna 102. In addition, the control unit 118 controls the output of the signal generator 134 so as to supply the net power to the antenna 102.

[0047] As a result, the radio device test system 100 can not only accurately measure the reflected wave power of the antenna 102, but also perform a radio device test while supplying net power to the antenna 102. In this way, the radio device test system 100 can be used for a so-called immunity test to verify whether or not electromagnetic waves radiated from the antenna 102 cause malfunctions in, for example, an in-vehicle device.

[0048] Fig. 6 is a diagram showing a modified example of a radio device test system 100A. Fig. 7 is a diagram showing a state in which an antenna 102 is connected to a coaxial cable 112 instead of the dummy antenna 130 in the radio device test system 100A of Fig. 6.

[0049] The radio device test system 100A includes a test system rack 106A. The test system rack 106A differs from the test system rack 106 in that it includes three power amplifiers 136a, 136b, and 136c corresponding to three different frequency bands, directional couplers 138a, 138b, and 138c, and selectors 150, 152, 154, and 156.

[0050] The signal generator 134 and the power amplifiers 136a, 136b, and 136c are connected via a selector 150. The directional couplers 138a, 138b, and 138c are connected between the power amplifiers 136a, 136b, and 136c and the selector 156, respectively.

[0051] Furthermore, power meter 140 is connected to the rear stage of directional couplers 138a, 138b, and 138c via selectors 152 and 154. Therefore, the forward wave power and reflected wave power output from directional couplers 138a, 138b, and 138c are measured by power meter 140 via selectors 152 and 154, respectively. Here, a state is shown in which the high-frequency signal from signal generator 134 is power-amplified by power amplifier 136a, and the forward wave power Pf and reflected wave power Pr output from directional coupler 138a are measured by power meter 140.

[0052] As a result, the control unit 118 (see FIG. 1) can switch the selectors 150, 152, 154, and 156 as appropriate, so that the high frequency signals can be power-amplified by the three power amplifiers 136a, 136b, and 136c, respectively.

[0053] In the radio device test system 100A, prior to the measurement of the antenna 102, a correlation coefficient is calculated between the power value of the power meter 140 downstream of the directional couplers 138a, 138b, and 138c and the power value of the dummy antenna 130, in a preliminary measurement using the dummy antenna 130, which has a variable voltage standing wave ratio. The power value of the power meter 140 when power is supplied to the antenna 102 is then corrected by the correlation coefficient to calculate the reflected wave power of the antenna 102. Therefore, in the radio device test system 100A as well, the reflected wave power of the antenna 102 can be accurately measured by performing the processing of steps S100 to S108 described above.

[0054] Fig. 8 is a diagram showing a modified example of the radio device test system 100 of Fig. 5. The modified radio device test system 100B differs from the radio device test system 100 in that a directional coupler 139 and a power meter 140A are added.

[0055] Directional coupler 139 is connected directly below antenna 102, couples a low-frequency band signal to antenna 102, and outputs forward power Pf and reflected power Pr. Power meter 140A is connected downstream of directional coupler 139, and measures forward power Pf and reflected power Pr output from directional coupler 139.

[0056] In the radio equipment test system 100B, when a signal in a low frequency band (e.g., 3 MHz to 30 MHz) is transmitted through the coaxial cable 112, the directional coupler 139 is connected directly below the antenna 102, and the power meter 140A is connected after the directional coupler 139, thereby enabling accurate measurement of the reflected wave power of the antenna 102.

[0057] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to these examples. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that these modifications and alterations also fall within the technical scope of the present invention. [Industrial Applicability]

[0058] The present invention can be used in a radio test system. [Explanation of symbols]

[0059] 100, 100A, 100B...Radio equipment test system, 102...Antenna, 104...Test cart, 106, 106A...Test system rack, 108...Measurement room, 110...Control device, 112...Coaxial cable, 112a...Inner conductor, 112b...Insulator, 112c...Outer conductor, 112d...Outer coating, 114...Radio wave anechoic chamber, 116...Control signal cable, 118...Control unit, 120...Correlation coefficient calculation unit, 122...Memory unit, 1 24...power value calculation unit, 126...operation unit, 128...internal bus, 130...pseudo antenna, 132, 146, 148, 150, 152, 154, 156...selector, 134...signal generator, 136, 136a, 136b, 136c...power amplifier, 138, 138a, 138b, 138c, 139...directional coupler, 140, 140A...power meter, 142...attenuator, 144...filter, 200...radio transmitter

Claims

1. In a radio equipment test system including an antenna connected to a coaxial cable, the radio equipment test system further comprises: a signal generator for generating a high frequency signal; a power amplifier that amplifies the power of the high-frequency signal; a pseudo antenna having a variable voltage standing wave ratio, which indicates the transmission efficiency of high frequency power, and which is connected to the coaxial cable in place of the antenna; a directional coupler connected between the power amplifier and the pseudo antenna, for coupling a power-amplified high-frequency signal to the pseudo antenna, and for outputting forward wave power and reflected wave power between the power amplifier and the pseudo antenna; a power meter connected to a downstream side of the directional coupler and configured to measure the forward wave power and the reflected wave power output from the directional coupler; a control device that calculates the reflected wave power of the antenna, The control device a correlation coefficient calculation unit that calculates a correlation coefficient between the forward wave power and the reflected wave power of the pseudo antenna for each voltage standing wave ratio of the pseudo antenna and the forward wave power and the reflected wave power measured by the power meter; and a power value calculation unit that calculates the reflected wave power of the antenna by correcting the forward wave power and the reflected wave power measured by the power meter with the pseudo antenna replaced with the antenna using the correlation coefficient.

2. the power value calculation unit calculates net power, which is effective power, by subtracting the calculated reflected wave power from the forward wave power of the antenna; 2. The radio equipment test system according to claim 1, wherein the control device further comprises a control section that controls an output of the signal generator so as to supply the net power to the antenna.

3. The radio test system further comprises: an attenuator connected between the directional coupler and the dummy antenna via a selector, for attenuating the reflected wave power from the dummy antenna and outputting the attenuated power to a power amplifier; and a filter for removing high frequency components of the reflected wave power or for matching impedance of a transmission line for high frequency power, 3. The radio equipment test system according to claim 2, wherein the control unit switches the selector to connect the attenuator or the filter between the directional coupler and the pseudo antenna.

4. The radio test system further comprises: another directional coupler connected directly below the antenna to couple a low-frequency band signal to the antenna and output forward wave power and reflected wave power; 4. The radio equipment test system according to claim 1, further comprising: another power meter connected to a subsequent stage of the other directional coupler, the other power meter measuring the forward wave power and the reflected wave power output from the other directional coupler.

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