JP2018087711A - Near field measurement device and near field measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a near field measurement device and near field measurement method that can easily reduce unevenness found in data on directivity of a front direction of a far field without conducting a plurality of near field scans.SOLUTION: A near field measurement device comprises: an amplitude calculation unit 17 that calculates amplitude of a radio signal received by a probe antenna 12; a phase calculation unit 18 that outputs a value in which a phase of the radio signal received by the probe antenna 12 is calculated as phase information; an amplitude correction unit 20 that replaces the value of the amplitude with a zero to output the value replaced with the zero as the amplitude information, as to a measurement position where the amplitude is judged equal to or less than a lower limit amplitude value by an amplitude judgement unit 19, and outputs the value of the amplitude as the amplitude information, as to a measurement position where the amplitude is judged not equal to or less than the lower limit amplitude value by the amplitude judgement unit 19; and a far field directivity calculation unit 21 that calculates directivity of a far field, using the amplitude information and phase information.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a near-field measurement device and a near-field measurement method, and more particularly to a near-field measurement device and a near-field measurement method for measuring an electric field strength distribution of an antenna in a near-field region.

  An array antenna such as a Massive-MIMO antenna has a plurality of antenna elements and is characterized in that the radiation direction and beam shape of an output electromagnetic wave can be controlled. As a method for measuring the characteristics of an antenna having such a strong directivity, a near field measurement (NFM) method is known in which far field directivity is calculated from a near electromagnetic field of the antenna by electromagnetic field theory.

  The near-field measurement method measures the electromagnetic field in the vicinity of the antenna, so that the loss of electromagnetic waves due to the space is small, and there is an advantage that the antenna can be diagnosed not only by the directivity measurement but also by the near-field distribution of the antenna.

  In general, as shown in FIG. 12, among the electromagnetic field radiated from the antenna opening surface, the region close to the antenna opening is a reactive near-field region mainly composed of electromagnetic field components that do not contribute to radiation ( A region that is in the vicinity of the pole and has no change in directivity depending on the distance from the antenna opening is called a radiation far-field region (far-field). In general, what is expressed as the directivity of the antenna is the directivity measured in this far field region.

The far field is defined as a position away from the maximum diameter D (opening dimension) of the antenna by a distance R that satisfies the following formula (1). Here, λ is a free space wavelength. Further, the maximum power Wa that can be received by the receiving antenna in free space is expressed by the following equation (2), where Gt is the gain of the transmitting antenna, Gr is the gain of the receiving antenna, and Wt is the transmitting power.
R> 2D ² / λ (1)
Wa = (λ / 4πR) ² · Gt · Gr · Wt (2)

  For this reason, in the antenna having a high gain and a large aperture surface, the distance R becomes large and the attenuation in the space becomes large. Furthermore, since the free space wavelength λ becomes smaller in the millimeter wave band, there is a problem that the amount of attenuation is further increased and it becomes difficult to measure a low level side lobe.

  The radiation near field region (near field), which is a region between the reactive near field region and the radiation far field region, is a region where the directivity changes according to the distance. The NFM described above measures the electromagnetic field in this radiation near-field region and obtains the directivity in the far field by calculation.

  Specifically, the vicinity of an antenna to which a predetermined signal is supplied is scanned with a probe antenna, and the distribution of amplitude and phase is obtained for each scanning position from the signal received by the probe antenna. Directivity can be obtained by data processing. Since measurement is performed near the antenna, the amount of attenuation in the space is small, and high-accuracy measurement is possible compared to far-field measurement.

  NFMs are classified into a plurality of types depending on the range in which the vicinity of the antenna to be measured is scanned, but planar NFMs that are advantageous for high gain antennas and that allow easy data processing are widely used.

  FIG. 13 shows the configuration of the measuring apparatus 10 that obtains the directivity of the antenna under measurement 100 using a planar NFM. The measuring apparatus 10 includes an antenna support 51 that supports the antenna 100 under measurement with its radiation surface facing a predetermined direction, a probe antenna 52 for receiving electromagnetic waves output from the antenna 100 under measurement, and a probe antenna. And a probe scanning mechanism 53 that moves 52 in the X and Y directions in a measurement plane near the radiation surface of the antenna 100 to be measured.

  The measurement apparatus 10 also controls a signal generator 54 that provides a measurement signal to the antenna 100 under measurement, an amplitude / phase detector 55 that detects amplitude and phase information from the received signal of the probe antenna 52, and a probe scanning mechanism 53. Then, the output of the amplitude phase detector 55 is received while scanning the position of the probe antenna 52 at a predetermined pitch in the measurement plane P, and the far-field directivity of the antenna 100 under measurement is determined from the amplitude phase distribution in the measurement plane P. And a display unit 57 for displaying the directivity of the obtained antenna 100 to be measured. Note that a network analyzer having these functions can be used as the signal generator 54 and the amplitude / phase detector 55, and a personal computer can be used as the measurement control unit 56.

  Here, in the case of NFM, the probe antenna 52 scans within the measurement plane P in the vicinity of the measurement signal about three wavelengths away from the antenna under measurement 100, and the amplitude and phase of the electric field are detected.

  The amplitude and phase distribution on the measurement plane P is in the form of a Fourier transform of a function defined by the directivity of the antenna under measurement 100 and the directivity of the probe antenna 52. In the measurement control unit 56, the inverse Fourier transform is performed. Then, the directivity of the antenna 100 to be measured can be obtained by performing calculation processing (probe correction) to remove the directivity of the probe antenna 52 after obtaining the function. Since the measurement control unit 56 can perform data processing by fast Fourier transform (FFT), the directivity of the far field of the antenna under measurement 100 can be calculated at high speed.

  As described above, the distribution of amplitude and phase in the measurement plane P is in the form of a Fourier transform of a function defined by the directivity of the antenna under measurement and the directivity of the probe antenna. As disclosed in Non-Patent Document 1, the directivity of the antenna under measurement 100 can be obtained by performing calculation processing (probe correction) to remove the directivity of the probe antenna 52 after the determination. Generally known.

  The NFM for obtaining the antenna directivity in this way has the following advantages over far field measurement (FFM).

  Since NFM is a measurement at a short distance, measurement is possible without using an anechoic chamber, and a large-scale device is not required. In addition, since the equipment is compact in the millimeter wave band, it is possible to measure with a simple anechoic box installed in the room, greatly reducing the time spent building a measurement system that is a problem in measurement in an anechoic chamber. Can do. Furthermore, since the measurement is performed in a region where the free space loss is small, a highly accurate measurement result can be obtained.

  Further, NFM can obtain the amplitude / phase distribution in the vicinity of the antenna, so that the cause can be diagnosed when the designed directivity cannot be obtained. This is a great advantage for phased array antennas such as Massive-MIMO antennas.

  However, NFM has a problem in that when measuring an antenna having a relatively small size and wide directivity, the directivity in the front direction of the far field is uneven. This is because a planar antenna with a relatively small aperture surface has a large area that scans the space around the antenna, and is strongly affected by the influence of the surrounding environment and scattering from the antenna substrate edge. (For example, refer nonpatent literature 2).

  Non-Patent Document 2 proposes a method of synthesizing data obtained on two scanning planes whose distances are changed by a half wavelength of the measurement signal in order to avoid this unevenness.

Specifically, as shown in FIG. 14, a scanning point near the front surface of the planar antenna on the scanning plane P1 is a, a scanning point far from the planar antenna is b, and λ _{0 in the} Z direction from each scanning point. Points on the scanning plane P2 moved by / 2 are defined as a ′ and b ′. At this time, plane waves radiated from the planar antenna mainly arrive at a and a ′, and an electric field with the same amplitude and reversed phase is observed. In addition, since spherical waves radiated from the antenna substrate end mainly reach b and b ′, and the distance from the planar antenna is greatly separated, an electric field having substantially the same phase is observed.

  From the above, the near-field electric field obtained on the scanning plane P1 and the near-field electric field obtained on the scanning plane P2 are added by inverting the phase, and a, a The electric field is added with the same phase at ', and the phase is inverted and added at b and b' where radiation is mainly from the antenna substrate end, so that the scattered wave component from the antenna substrate end can be removed. .

OHM Co., Ltd. July 25, 2008 Antenna Engineering Handbook (2nd edition) The Institute of Electronics, Information and Communication Engineers p730-p733 Takashi Kawamura, Aya Yamamoto, Satoshi Teshirogi, "Correction of beam front and back irregularities in planar near-field measurement", Proceedings of the IEICE General Conference, March 7, 2007, B-1-201

  However, the method of Non-Patent Document 2 has a problem that the measurement time increases due to an increase in the number of scans. Furthermore, since it is necessary to accurately change the distance between the antenna and the probe, there is a problem that the measuring apparatus becomes complicated and the cost increases.

  The present invention has been made to solve such a conventional problem, and it is possible to simplify the unevenness seen in the directivity data in the front direction of the far field without performing multiple near-field scans. An object of the present invention is to provide a near-field measurement device and a near-field measurement method that can be reduced.

  In order to solve the above problems, a near-field measurement device according to the present invention is a near-field measurement device that measures the amplitude and phase of a radio signal transmitted from a measured antenna in the near field, A probe antenna that receives the wireless signal at a plurality of measurement positions arranged in a predetermined measurement plane in the near field region, a probe scanning mechanism that moves the probe antenna to the plurality of measurement positions, and the probe scanning mechanism Each time the probe antenna is moved to the measurement position, a quadrature detector that outputs a real component and an imaginary component of a waveform of a radio signal received by the probe antenna, and a real component output from the quadrature detector And an amplitude calculation unit for calculating the amplitude of the radio signal received by the probe antenna from the imaginary component, and the quadrature detection unit A phase calculation unit that outputs a value obtained by calculating a phase of a radio signal received by the probe antenna from the output real number component and imaginary number component as phase information, and a lower limit amplitude in which the amplitude calculated by the amplitude calculation unit is constant An amplitude determination unit that determines whether or not the amplitude is equal to or less than a value; and amplitude information by replacing the amplitude value with zero for the measurement position at which the amplitude is determined to be equal to or less than the lower limit amplitude value by the amplitude determination unit And an amplitude correction unit that outputs the amplitude value as amplitude information for the measurement position at which the amplitude is determined not to be less than or equal to the lower limit amplitude value, and the amplitude information and the phase information. And a far-field directivity calculating unit that calculates the far-field directivity using the.

  With this configuration, the near-field measurement device according to the present invention corrects the amplitude data at the measurement position before the far-field conversion for the measurement position where the amplitude obtained by the near-field scanning is equal to or lower than the lower limit amplitude value. Thus, it is possible to easily reduce the unevenness seen in the directivity data in the front direction of the far field without performing near field scanning a plurality of times as in the prior art.

  The near-field measurement device according to the present invention is a near-field measurement device that measures the amplitude and phase of a radio signal transmitted from the antenna under measurement in the near field, and is a predetermined field in the near-field region of the antenna under measurement. At a plurality of measurement positions arranged in a measurement plane, a probe antenna that receives the radio signal, a probe scanning mechanism that moves the probe antenna to the plurality of measurement positions, and the probe scanning mechanism causes the probe antenna to be Each time it is moved to the measurement position, the quadrature detection unit that outputs the real component and the imaginary component of the waveform of the radio signal received by the probe antenna, and the real component and the imaginary component output from the quadrature detection unit, An amplitude calculation unit that outputs a value obtained by calculating the amplitude of the radio signal received by the probe antenna as amplitude information; A phase calculation unit for calculating a phase of a radio signal received by the probe antenna from a real component and an imaginary component output from the unit, and whether the amplitude calculated by the amplitude calculation unit is equal to or less than a certain lower limit amplitude value An amplitude determination unit that determines whether or not the phase value calculated by the phase calculation unit is 0 ° to 360 ° for the measurement position at which the amplitude is determined to be less than or equal to the lower limit amplitude value by the amplitude determination unit. The phase information is output as phase information by replacing it with a random value in the range of the phase of the phase calculated by the phase calculation unit for the measurement position where the amplitude determination unit determines that the amplitude is not less than or equal to the lower limit amplitude value. A configuration comprising: a phase correction unit that outputs a value as phase information; and a far-field directivity calculation unit that calculates a far-field directivity using the amplitude information and the phase information. A.

  With this configuration, the near-field measurement device according to the present invention corrects the phase data at the measurement position before the far-field conversion for the measurement position where the amplitude obtained by the near-field scanning is equal to or lower than the lower limit amplitude value. Thus, it is possible to easily reduce the unevenness seen in the directivity data in the front direction of the far field without performing near field scanning a plurality of times as in the prior art.

  Further, the near-field measuring device according to the present invention includes a display unit that displays the far-field directivity calculated by the far-field directivity calculating unit, an amplitude value setting unit for setting the lower limit amplitude value, Is further provided.

  With this configuration, the near-field measurement device according to the present invention allows the user to operate the amplitude value setting unit according to the degree of unevenness in the directivity data in the front direction of the far field displayed on the display unit. An amplitude value can be set.

  In the near-field measurement device according to the present invention, the amplitude value setting unit automatically sets the lower limit amplitude value based on the far-field directivity calculated by the far-field directivity calculation unit. It is.

  With this configuration, the near-field measurement device according to the present invention can automatically perform processing for setting an appropriate lower limit amplitude value based on the far-field directivity calculated from the far-field directivity calculation unit. Become.

  The near-field measurement method according to the present invention is a near-field measurement method for measuring in the near field the amplitude and phase of a radio signal transmitted from the antenna under measurement using any of the above-described near-field measurement devices. A probe scanning step of moving the probe antenna to a plurality of measurement positions, a signal reception step of receiving a radio signal by the probe antenna at the measurement position where the probe antenna is moved in the probe scanning step, and the signal The quadrature detection step for outputting the real component and the imaginary component of the waveform of the radio signal received in the reception step, and the radio signal received in the signal reception step from the real component and the imaginary component output in the quadrature detection step Amplitude calculation step for calculating the amplitude and whether the real number component and the imaginary number component output in the orthogonal detection step A phase calculation step for outputting a value obtained by calculating a phase of the radio signal received in the signal reception step as phase information, and whether the amplitude calculated in the amplitude calculation step is equal to or less than a certain lower limit amplitude value. Amplitude determination step for determining, and for the measurement position where the amplitude is determined to be less than or equal to the lower limit amplitude value in the amplitude determination step, the amplitude value is replaced with zero and output as amplitude information, and the amplitude determination An amplitude correction step for outputting the amplitude value as amplitude information for the measurement position where the amplitude is determined not to be less than or equal to the lower limit amplitude value in step, and directing the far field using the amplitude information and the phase information And a far-field directivity calculating step for calculating the characteristics.

  With this configuration, the near-field measurement method according to the present invention corrects the amplitude data at the measurement position before the far-field conversion for the measurement position where the amplitude obtained by the near-field scanning is equal to or lower than the lower limit amplitude value. Thus, it is possible to easily reduce the unevenness seen in the directivity data in the front direction of the far field without performing near field scanning a plurality of times as in the prior art.

  The near-field measurement method according to the present invention is a near-field measurement method for measuring in the near field the amplitude and phase of a radio signal transmitted from the antenna under measurement using any of the above-described near-field measurement devices. A probe scanning step of moving the probe antenna to a plurality of measurement positions; a signal reception step of receiving the radio signal by the probe antenna at the measurement position where the probe antenna is moved in the probe scanning step; A quadrature detection step for outputting a real component and an imaginary component of a waveform of the radio signal received in the signal reception step, and a radio signal received in the signal reception step from the real component and the imaginary component output in the quadrature detection step The amplitude calculation step for outputting the calculated amplitude value as amplitude information and the quadrature detection step A phase calculation step for calculating a phase of the radio signal received in the signal reception step from the real number component and the imaginary number component, and whether the amplitude calculated in the amplitude calculation step is equal to or less than a certain lower limit amplitude value And a phase value calculated in the phase calculation step in a range of 0 ° to 360 ° for the measurement position where the amplitude is determined to be equal to or lower than the lower limit amplitude value in the amplitude determination step. And the phase value calculated in the phase calculation step for the measurement position where the amplitude is determined not to be less than or equal to the lower limit amplitude value in the amplitude determination step. A phase correction step for outputting as phase information, and a far-field directivity calculation step for calculating far-field directivity using the amplitude information and the phase information. It is a configuration including a flop, the.

  With this configuration, the near-field measurement method according to the present invention corrects the phase data at the measurement position before the far-field conversion for the measurement position where the amplitude obtained by the near-field scanning is equal to or lower than the lower limit amplitude value. Thus, it is possible to easily reduce the unevenness seen in the directivity data in the front direction of the far field without performing near field scanning a plurality of times as in the prior art.

  The present invention provides a near-field measurement apparatus and a near-field measurement method that can easily reduce the unevenness seen in the directivity data in the front direction of the far field without performing multiple near-field scans. It is.

It is a block diagram of the near field measuring apparatus which concerns on 1st Embodiment. (A) is sectional drawing of the rectangular waveguide used as a probe antenna, (b) is sectional drawing of the double ridge waveguide used as a probe antenna. It is a front view which shows the structure of the 1 * 4 array antenna as a to-be-measured antenna. (A) is a graph which shows an example of the two-dimensional data of the amplitude calculated by an amplitude calculation part, (b) is a graph which shows an example of the two-dimensional data of the phase calculated by a phase calculation part. It is a graph which shows an example of the directivity of a far field. 6 is an enlarged graph showing the vicinity of the center of directivity in FIG. 5. It is a graph which shows the directivity of a far field at the time of correct | amending the amplitude in a near field by an amplitude correction part. It is a flowchart which shows the process of the near field measurement method by the near field measurement apparatus which concerns on 1st Embodiment. It is a block diagram of the near field measuring apparatus which concerns on 2nd Embodiment. It is a graph which shows the directivity of a far field at the time of correct | amending the phase in a near field by a phase correction part. It is a flowchart which shows the process of the near field measurement method by the near field measurement apparatus which concerns on 2nd Embodiment. It is explanatory drawing of the measurement area | region of an antenna. It is a block diagram of the conventional near field measuring apparatus. It is a block diagram which shows the structure for performing the correction | amendment of the conventional directivity.

  Hereinafter, embodiments of a near-field measurement device and a near-field measurement method according to the present invention will be described with reference to the drawings.

  As described in the “Background Art” section, conventionally, the cause of unevenness in directivity data was considered to be due to the influence of scattering from the antenna substrate end. The applicant of the present invention conceives that the present invention is presumed that, as a cause other than the above, the influence due to the fact that data different from the original electric field data is obtained due to the lack of the dynamic range of the measurement system is large. It came. That is, the present invention obtains directivity data having no irregularities by processing data whose amplitude of data obtained by near-field scanning is below a certain value (below the limit level of the measurement system) before far-field conversion. It is intended.

(First embodiment)
As shown in FIG. 1, the near-field measurement device 1 according to the first embodiment of the present invention measures the amplitude and phase of a radio signal transmitted from an antenna under measurement 100 including a plurality of antenna elements in the near field. The directivity in the far field is calculated.

  The antenna under measurement 100 is an array antenna such as a Massive-MIMO antenna. As a radio signal to be transmitted from the antenna under measurement 100 when measuring the directivity by the near-field measuring device 1, an unmodulated wave signal, a broadband signal (for example, OFDM signal), or the like can be used.

  The near-field measurement device 1 includes an antenna support unit 11, a probe antenna 12, a probe scanning mechanism 13, a scanning control unit 14, a signal generator 15, a quadrature detection unit 16, an amplitude calculation unit 17, and a phase calculation. Unit 18, amplitude determination unit 19, amplitude correction unit 20, far-field directivity calculation unit 21, storage unit 22, display unit 23, operation unit 24, and control unit 25. At least one of the operation unit 24 and the control unit 25 constitutes an amplitude value setting unit.

  The antenna support unit 11 is configured to support the antenna to be measured 100 in a state where the electromagnetic wave radiation surface 100a faces a predetermined direction.

  The probe antenna 12 receives electromagnetic waves of radio signals output from the antenna under measurement 100 at a plurality of measurement positions arranged in a predetermined measurement plane P in the near field region of the antenna under measurement 100. .

  For example, the probe antenna 12 may be a waveguide having a waveguide for propagating electromagnetic waves in a predetermined frequency range of a microwave or millimeter wave band and having an open end. Examples of such a waveguide include a rectangular waveguide having a rectangular cross-sectional shape, and a double-ridge waveguide in which the cross-sectional shape of the waveguide is smaller at the center than at both sides. A tube can be used.

  FIG. 2A is a diagram showing a cross section perpendicular to the longitudinal direction of a waveguide 30 of a rectangular waveguide used as the probe antenna 12. The rectangular waveguide outer shape a × b is arbitrary as long as it is larger than the inner diameter w0 × h0 and can provide strength as a structure.

  FIG. 2B is a diagram showing a cross section perpendicular to the longitudinal direction of the waveguide 31 of the double ridge waveguide used as the probe antenna 12. In the double ridge waveguide, two projecting portions 32a and 32b projecting in a direction approaching each other from the center of the upper and lower inner walls are formed continuously in the longitudinal direction. That is, the height h1 of the central portion 31a of the waveguide 31 is set to be smaller than the height h2 of the side portions 31b and 31c.

  In the case of this double ridge waveguide, by adjusting the width w1 and height h1 of the central portion 31a and the width w2 and height h2 of the side portions 31b and 31c, the waveguide of the standard rectangular waveguide can be adjusted. There is an advantage that electromagnetic waves in the same frequency range can be propagated with a cross-sectional shape smaller than the cross-sectional shape. Further, if the double ridge waveguide has the same width and height, there is an advantage that the opening becomes wider and the reception sensitivity is increased.

  The probe scanning mechanism 13 moves the probe antenna 12 in the X and Y directions in the measurement plane P near the electromagnetic radiation surface 100a of the antenna 100 to be measured. That is, the probe scanning mechanism 13 moves the probe antenna 12 to a plurality of measurement positions in the measurement plane P.

  The scanning control unit 14 controls the probe scanning mechanism 13 to move the probe antenna 12 to all measurement positions (lattice points) in the measurement plane P in a predetermined order. For example, these measurement positions are arranged at positions corresponding to the respective lattice points of the square lattice on the measurement plane P. Further, the scanning control unit 14 is configured to send position information of the measurement position where the probe antenna 12 exists to the far-field directivity calculation unit 21.

  The signal generator 15 generates a radio signal such as an unmodulated wave signal or a wideband signal (for example, an OFDM signal), and outputs the generated radio signal to the antenna under measurement 100, so that the radio signal is measured. To send from. The signal generator 15 outputs a synchronization signal synchronized with the output of the radio signal to the antenna under measurement 100 to the phase calculation unit 18.

  Each time the probe antenna 12 is moved to the measurement position by the probe scanning mechanism 13, the quadrature detection unit 16 performs the real component Re (X, Y, t) of the waveform at time t of the radio signal received by the probe antenna 12 and An imaginary number component Im (X, Y, t) is output.

The amplitude calculator 17 calculates the amplitude of the radio signal received by the probe antenna 12 from the real component Re (X, Y, t) and the imaginary component Im (X, Y, t) output from the quadrature detector 16. It is supposed to be. The amplitude A (X, Y, t) calculated by the amplitude calculation unit 17 is expressed as the following equation (3).

The phase calculation unit 18 calculates the phase of the radio signal received by the probe antenna 12 from the real number component Re (X, Y, t) and the imaginary number component Im (X, Y, t) output from the quadrature detection unit 16. The value obtained is output as phase information. The phase Ph (X, Y, t) calculated by the phase calculation unit 18 is expressed as the following equation (4).

  As described above, the amplitude calculator 17 and the phase calculator 18 obtain the amplitude and phase distribution in the measurement plane P. The amplitude calculation unit 17 and the phase calculation unit 18 can be configured by a vector network analyzer, a spectrum analyzer, an oscilloscope, or the like.

  The amplitude determination unit 19 determines whether or not the amplitude A (X, Y, t) at each measurement position calculated by the amplitude calculation unit 17 is equal to or less than a certain lower limit amplitude value.

  The amplitude correction unit 20 sets the value of the amplitude A (X, Y, t) to zero, that is, the measurement position where the amplitude A (X, Y, t) is determined to be less than or equal to the lower limit amplitude value by the amplitude determination unit 19. Replace with -∞ dB and output as amplitude information. In addition, the amplitude correction unit 20 determines the amplitude A (X, Y, t) as the amplitude at the measurement position where the amplitude determination unit 19 determines that the amplitude A (X, Y, t) is not less than or equal to the lower limit amplitude value. It is output as information. Here, replacing the value of the amplitude A (X, Y, t) with zero means that the real number component Re (X, Y, t) and the imaginary number component Im (X, Y, t) in the equations (3) and (4). ) Means zero.

  The far-field directivity calculation unit 21 uses the position information of the probe antenna 12 output from the scanning control unit 14, the amplitude information output from the amplitude correction unit 20, and the phase information output from the phase calculation unit 18. Thus, the far-field directivity is calculated. Here, the far-field directivity in the far field of the antenna 100 to be measured can be obtained by estimating the far-field electric field strength distribution by performing numerical calculation using a known near-field / far-field conversion method.

  The storage unit 22 is configured to store the amplitude calculated by the amplitude calculation unit 17 and the phase value calculated by the phase calculation unit 18 in association with the measurement position. Further, the storage unit 22 may store the amplitude information output from the amplitude correction unit 20 and the far-field directivity calculated by the far-field directivity calculation unit 21.

  The display unit 23 is configured by a display device such as an LCD or a CRT, for example, and displays various display contents according to a control signal from the control unit 25. This display content includes the measurement result of the amplitude and phase in the near field of the antenna 100 to be measured, the directivity calculation result in the far field of the antenna 100 to be measured, and the like. Furthermore, the display unit 23 may display operation objects such as soft keys for setting measurement conditions and the like, a pull-down menu, and a text box.

  The operation unit 24 is for performing an operation input by a user, and includes an input device such as a keyboard, a touch panel, or a mouse. For example, the user can input a lower limit amplitude value using the operation unit 24. Alternatively, the operation unit 24 may be configured such that operation objects such as buttons, soft keys, pull-down menus, and text boxes are displayed on the display unit 23.

  The control unit 25 is composed of, for example, a microcomputer or a personal computer including a CPU, ROM, RAM, and the like, and controls operations of the above-described units constituting the near-field measurement device 1. Furthermore, the control unit 25 configures the amplitude calculation unit 17, the phase calculation unit 18, the amplitude determination unit 19, the amplitude correction unit 20, and the far-field directivity calculation unit 21 by software by executing a predetermined program. It has become.

  The control unit 25 sets the lower limit amplitude value input by the operation unit 24 in the amplitude determination unit 19. Alternatively, the control unit 25 may be configured to automatically set the lower limit amplitude value in the amplitude determination unit 19 based on the far-field directivity calculated by the far-field directivity calculation unit 21. Further, the control unit 25 evaluates whether or not the difference between the directivity data at adjacent angles is within an allowable range in the vicinity of 0 ° of the directivity of the far field, thereby directing the far field in the front direction. It is also possible to determine whether or not the sex data has an optimum value.

  Hereinafter, the results of measuring the directivity of the antenna under measurement 100 as shown in FIG. 3 using the near-field measurement apparatus 1 of the present embodiment will be described.

  As shown in FIG. 3, the 1 × 4 array antenna as an example of the antenna under measurement 100 includes an SMA connector 101 for inputting a radio signal from the signal generator 15, an antenna pattern 102 including four antenna elements, including.

  As shown in FIG. 4A, the amplitude calculator 17 generates two-dimensional amplitude data as near-field measurement data. Moreover, the phase calculation part 18 produces | generates the two-dimensional data of a phase as near-field measurement data, as shown in FIG.4 (b).

  FIG. 5 shows the far-field directivity of the antenna under measurement 100 by executing a two-dimensional inverse Fourier transform process on the two-dimensional data of the amplitude and phase calculated by the amplitude calculator 17 and the phase calculator 18. It is a graph which shows the calculated | required result.

  FIG. 6 is an enlarged graph showing the vicinity of the center of directivity in FIG. From this graph, it can be seen that there is a drop near 0 ° in the directivity of both the horizontal plane and the vertical plane.

  FIG. 7 shows a case where the amplitude in the near field is corrected by the amplitude correction unit 20 with respect to the directivity of the horizontal plane shown in FIG. 6 (shown as “no processing” by a dashed line in FIG. 7). 5 is a graph showing the directivity calculated by the far-field directivity calculating unit 21. The broken line indicates the directivity when the amplitude of −60 dB or less is replaced with −∞ dB. The solid line indicates the directivity when the amplitude of −55 dB or less is replaced with −∞ dB. Compared to the result without processing, the drop around 0 ° is slightly improved when the amplitude of −60 dB or less is set to −∞ dB, and the drop near 0 ° is obtained when the amplitude of −55 dB or less is set to −∞ dB. It has been improved to a level where it can hardly be seen. Similar results can be obtained for the directivity of the vertical plane shown in FIG.

  Hereinafter, a near-field measurement method using the near-field measurement apparatus 1 of the present embodiment will be described with reference to the flowchart of FIG.

  First, the signal generator 15 outputs a radio signal to the antenna under measurement 100 and outputs a synchronization signal synchronized with the output of the radio signal to the antenna under measurement 100 to the phase calculation unit 18 (step S1).

  Next, the scanning control unit 14 moves the probe antenna 12 to the measurement position in the measurement plane P by the probe scanning mechanism 13 (probe scanning step S2).

  Next, the probe antenna 12 receives the radio signal output from the antenna under measurement 100 in the near-field region at the measurement position moved in the probe scanning step S2 (signal reception step S3).

  Next, the quadrature detection unit 16 outputs the real component Re (X, Y, t) and the imaginary component Im (X, Y, t) of the waveform of the radio signal received in the signal reception step S3 (orthogonal detection step). S4).

  Next, the amplitude calculation unit 17 receives the radio signal received in the signal reception step S3 from the real number component Re (X, Y, t) and the imaginary number component Im (X, Y, t) output in the quadrature detection step S4. Is calculated (amplitude calculation step S5).

  Next, the phase calculation unit 18 receives the radio signal received in the signal reception step S3 from the real number component Re (X, Y, t) and the imaginary number component Im (X, Y, t) output in the quadrature detection step S4. A value obtained by calculating the phase is output as phase information (phase calculation step S6).

  Next, the control unit 25 determines whether amplitude and phase values have been obtained for all measurement positions in the measurement plane P (step S7). If a negative determination is made, the process returns to the probe scanning step S2. If the determination is affirmative, the process proceeds to step S8.

  Next, the control unit 25 sets the initial value of the lower limit amplitude value in the amplitude determination unit 19 (step S8).

  Next, the amplitude determination unit 19 determines whether or not the amplitude at each measurement position calculated in the amplitude calculation step S5 is equal to or less than a certain lower limit amplitude value (amplitude determination step S9).

  Next, the amplitude correction unit 20 sets the value of the amplitude A (X, Y, t) for the measurement position where the amplitude A (X, Y, t) is determined to be equal to or lower than the lower limit amplitude value in the amplitude determination step S9. Replace with zero and output as amplitude information. In addition, the amplitude correction unit 20 determines the amplitude A (X, Y, t) as the amplitude at the measurement position where the amplitude A (X, Y, t) is determined not to be lower than the lower limit amplitude value in the amplitude determination step S9. It outputs as information (amplitude correction step S10).

  Next, the far-field directivity calculation unit 21 calculates the far-field directivity using the position information, amplitude information, and phase information obtained for all measurement positions (far-field directivity calculation step S11). ).

  Next, the control unit 25 determines whether or not the far field directivity directivity data obtained in the far field directivity calculation step S11 is an optimum value (step S12). For example, the control unit 25 evaluates whether or not the difference in directivity data at adjacent angles is within an allowable range in the vicinity of 0 ° of the directivity of the far field, thereby directing the far field in the front direction. It can be determined whether or not the sex data has an optimum value. If the determination is negative in step S12, the process proceeds to step S13, and if the determination is affirmative, the process ends.

  Next, the control unit 25 updates the lower limit amplitude value (step S13). For example, the control unit 25 performs a process of changing the lower limit amplitude value from the current value in predetermined increments.

  As described above, the near-field measurement device 1 according to the present embodiment, for the measurement position where the amplitude obtained by the near-field scanning is equal to or lower than the lower limit amplitude value, converts the amplitude data at the measurement position before the far-field conversion. By correcting, it is possible to easily reduce the unevenness seen in the directivity data in the front direction of the far field without performing near-field scanning multiple times as in the prior art.

  In addition, the near-field measurement device 1 according to the present embodiment has an appropriate lower limit that the user can operate by operating the operation unit 24 according to the degree of unevenness in the directivity data in the front direction of the far field displayed on the display unit 23. Allows you to set the amplitude value.

  Alternatively, the near-field measurement device 1 according to the present embodiment outputs the far-field frontal directivity data from the far-field directivity calculating unit 21 to the control unit 25, and the output frontal directivity data. It is also possible to automatically perform processing for setting an appropriate lower limit amplitude value by the control unit 25 based on the above. By automatically repeating the setting of the lower limit amplitude value and the calculation of the far field directivity, the directivity data in the front direction of the far field can be automatically converged to the optimum value.

(Second Embodiment)
Subsequently, a near-field measuring apparatus 2 according to a second embodiment of the present invention will be described with reference to the drawings. About the same structure as the structure of the near-field measurement apparatus 1 which concerns on 1st Embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  As shown in FIG. 9, the near-field measurement device 2 includes a phase correction unit 26 instead of the amplitude correction unit 20 in the first embodiment.

  In the present embodiment, the amplitude calculator 17 is received by the probe antenna 12 from the real component Re (X, Y, t) and the imaginary component Im (X, Y, t) output from the quadrature detector 16. A value obtained by calculating the amplitude A (X, Y, t) of the radio signal is output as amplitude information.

  In addition, the phase calculation unit 18 uses the real component Re (X, Y, t) and the imaginary component Im (X, Y, t) output from the quadrature detection unit 16 and the phase of the radio signal received by the probe antenna 12. Ph (X, Y, t) is calculated.

  The phase correction unit 26 uses the phase Ph (X, Y, t) calculated by the phase calculation unit 18 for the measurement position at which the amplitude A (X, Y, t) is determined to be less than or equal to the lower limit amplitude value by the amplitude determination unit 19. The value of t) is replaced with a random value in the range of 0 ° to 360 ° and output as phase information. Here, as a random value in the range of 0 ° to 360 ° output by the phase correction unit 26, an arbitrary random number such as a uniform random number according to the uniform distribution or a normal random number according to the normal distribution can be used. The phase correction unit 26 also uses the phase Ph (X, X, calculated by the phase calculation unit 18 for the measurement position where the amplitude A (X, Y, t) is determined not to be less than or equal to the lower limit amplitude value by the amplitude determination unit 19. The value of Y, t) is output as phase information.

  The storage unit 22 is configured to store the amplitude calculated by the amplitude calculation unit 17 and the phase value calculated by the phase calculation unit 18 in association with the measurement position. Further, the storage unit 22 may store the phase information output from the phase correction unit 26 and the far-field directivity calculated by the far-field directivity calculation unit 21.

  FIG. 10 shows a case where the phase in the near field is corrected by the phase correction unit 26 with respect to the directivity of the horizontal plane shown in FIG. 6 (indicated as “no processing” by a one-dot chain line in FIG. 10). 5 is a graph showing the directivity calculated by the far-field directivity calculating unit 21. The broken line indicates the directivity when the phase of −60 dB or less is replaced with a random value. The solid line indicates the directivity when the amplitude of −55 dB or less is replaced with a random value. Compared to the result without processing, the result of making the phase random at an amplitude of −60 dB or less shows no significant improvement in the drop near 0 °, but the result of making the phase a random value at an amplitude of −55 dB or less. The drop around 0 ° is clearly improved. Similar results can be obtained for the directivity of the vertical plane shown in FIG.

  Hereinafter, a near-field measurement method using the near-field measurement apparatus 2 of the present embodiment will be described with reference to the flowchart of FIG.

  First, the signal generator 15 outputs a radio signal to the antenna under measurement 100 and outputs a synchronization signal synchronized with the output of the radio signal to the antenna under measurement 100 to the phase calculation unit 18 (step S21).

  Next, the scanning control unit 14 causes the probe scanning mechanism 13 to move the probe antenna 12 to a measurement position in the measurement plane P (probe scanning step S22).

  Next, the probe antenna 12 receives the radio signal output from the antenna under measurement 100 in the near-field region at the measurement position moved in the probe scanning step S22 (signal reception step S23).

  Next, the quadrature detection unit 16 outputs the real number component Re (X, Y, t) and the imaginary number component Im (X, Y, t) of the waveform of the radio signal received in the signal receiving step S23 (orthogonal detection step). S24).

  Next, the amplitude calculation unit 17 receives the radio signal received in the signal reception step S23 from the real number component Re (X, Y, t) and the imaginary number component Im (X, Y, t) output in the quadrature detection step S24. A value obtained by calculating the amplitude is output as amplitude information (amplitude calculation step S25).

  Next, the phase calculation unit 18 receives the radio signal received in the signal reception step S23 from the real number component Re (X, Y, t) and the imaginary number component Im (X, Y, t) output in the quadrature detection step S24. Is calculated (phase calculation step S26).

  Next, the control unit 25 determines whether amplitude and phase values have been obtained for all measurement positions in the measurement plane P (step S27). If a negative determination is made, the process returns to the probe scanning step S22. If the determination is affirmative, the process proceeds to step S28.

  Next, the control unit 25 sets the initial value of the lower limit amplitude value in the amplitude determination unit 19 (step S28).

  Next, the amplitude determination unit 19 determines whether or not the amplitude at each measurement position calculated in the amplitude calculation step S25 is equal to or less than a certain lower limit amplitude value (amplitude determination step S29).

  Next, the phase correction unit 26 uses the value of the phase Ph (X, Y, t) calculated in the phase calculation step S26 for the measurement position where the amplitude is determined to be less than or equal to the lower limit amplitude value in the amplitude determination step S29. Substituting with random values in the range of 0 ° to 360 ° and outputting as phase information. In addition, the phase correction unit 26 uses the value of the phase Ph (X, Y, t) calculated in the phase calculation step S26 for the measurement position where the amplitude is determined not to be less than or equal to the lower limit amplitude value in the amplitude determination step S29. It outputs as information (phase correction step S30).

  Next, the far-field directivity calculating unit 21 calculates the far-field directivity using the position information, amplitude information, and phase information regarding all measurement positions (far-field directivity calculating step S31).

  Next, the control unit 25 determines whether or not the far field directivity directivity data obtained in the far field directivity calculation step S31 is an optimum value (step S32). If the determination is negative, the process proceeds to step S33. If the determination is affirmative, the process ends.

  Next, the control unit 25 updates the lower limit amplitude value (step S33). For example, the control unit 25 performs a process of changing the lower limit amplitude value from the current value in predetermined increments.

  As described above, the near-field measurement device 2 according to the present embodiment converts the phase data at the measurement position before the far-field conversion for the measurement position where the amplitude obtained by the near-field scanning is equal to or lower than the lower limit amplitude value. By correcting, it is possible to easily reduce the unevenness seen in the directivity data in the front direction of the far field without performing near-field scanning multiple times as in the prior art.

  In addition, the near-field measurement device 2 according to the present embodiment has an appropriate lower limit that the user can operate by operating the operation unit 24 according to the degree of unevenness in the directivity data in the front direction of the far field displayed on the display unit 23. Allows you to set the amplitude value.

  Alternatively, the near-field measurement apparatus 2 according to the present embodiment outputs the far-field front direction directivity data from the far-field directivity calculation unit 21 to the control unit 25, and outputs the front direction directivity data. It is also possible to automatically perform processing for setting an appropriate lower limit amplitude value by the control unit 25 based on the above. By automatically repeating the setting of the lower limit amplitude value and the calculation of the far field directivity, the directivity data in the front direction of the far field can be automatically converged to the optimum value.

DESCRIPTION OF SYMBOLS 1, 2 Near field measurement apparatus 11 Antenna support part 12 Probe antenna 13 Probe scanning mechanism 14 Scan control part 15 Signal generator 16 Quadrature detection part 17 Amplitude calculation part 18 Phase calculation part 19 Amplitude judgment part 20 Amplitude correction part 21 Far field directivity 21 Sex calculation unit 22 storage unit 23 display unit 24 operation unit 25 control unit 26 phase correction unit 30, 31 waveguide 31a central part 31b, 31c both sides 32a, 32b projecting part 100 antenna to be measured 100a electromagnetic wave radiation surface 101 SMA connector 102 antenna pattern

Claims (6)

A near-field measuring device (1) for measuring the amplitude and phase of a radio signal transmitted from a measured antenna (100) in the near field,
A probe antenna (12) for receiving the radio signal at a plurality of measurement positions arranged in a predetermined measurement plane in a near field region of the antenna under measurement;
A probe scanning mechanism (13) for moving the probe antenna to the plurality of measurement positions;
A quadrature detector (16) for outputting a real component and an imaginary component of a waveform of a radio signal received by the probe antenna each time the probe antenna is moved to the measurement position by the probe scanning mechanism;
An amplitude calculation unit (17) for calculating the amplitude of the radio signal received by the probe antenna from the real number component and the imaginary number component output from the quadrature detection unit;
A phase calculator (18) that outputs, as phase information, a value obtained by calculating a phase of a radio signal received by the probe antenna from a real component and an imaginary component output from the quadrature detector;
An amplitude determination unit (19) for determining whether the amplitude calculated by the amplitude calculation unit is equal to or less than a certain lower limit amplitude value;
For the measurement position where the amplitude is determined to be less than or equal to the lower limit amplitude value by the amplitude determination unit, the amplitude value is replaced with zero and output as amplitude information, and the amplitude is determined by the amplitude determination unit. An amplitude correction unit (20) for outputting the amplitude value as amplitude information for the measurement position determined not to be less than the amplitude value;
A near-field measurement device comprising: a far-field directivity calculating unit (21) that calculates the far-field directivity using the amplitude information and the phase information. A near field measurement device (2) for measuring the amplitude and phase of a radio signal transmitted from an antenna under measurement (100) in the near field,
A probe antenna (12) for receiving the radio signal at a plurality of measurement positions arranged in a predetermined measurement plane in a near field region of the antenna under measurement;
A probe scanning mechanism (13) for moving the probe antenna to the plurality of measurement positions;
A quadrature detector (16) for outputting a real component and an imaginary component of a waveform of a radio signal received by the probe antenna each time the probe antenna is moved to the measurement position by the probe scanning mechanism;
An amplitude calculator (17) that outputs, as amplitude information, a value obtained by calculating the amplitude of the radio signal received by the probe antenna from the real component and the imaginary component output from the quadrature detector;
A phase calculation unit (18) for calculating a phase of a radio signal received by the probe antenna from a real number component and an imaginary number component output from the quadrature detection unit;
An amplitude determination unit (19) for determining whether the amplitude calculated by the amplitude calculation unit is equal to or less than a certain lower limit amplitude value;
For the measurement position where the amplitude is determined to be less than or equal to the lower limit amplitude value by the amplitude determination unit, the phase value calculated by the phase calculation unit is replaced with a random value in the range of 0 ° to 360 °. A phase correction unit that outputs the phase value calculated by the phase calculation unit as phase information for a measurement position that is output as phase information and is determined by the amplitude determination unit to be less than or equal to the lower limit amplitude value (26) and
A near-field measurement device comprising: a far-field directivity calculating unit (21) that calculates the far-field directivity using the amplitude information and the phase information. A display unit (23) for displaying the far-field directivity calculated by the far-field directivity calculating unit;
The near field measurement device according to claim 1, further comprising an amplitude value setting unit (24, 25) for setting the lower limit amplitude value.   4. The near field measurement according to claim 3, wherein the amplitude value setting unit automatically sets the lower limit amplitude value based on the far field directivity calculated by the far field directivity calculation unit. apparatus. A near-field measurement method for measuring the amplitude and phase of a radio signal transmitted from an antenna under measurement (100) in the near field using the near-field measurement device according to claim 1, claim 3, or claim 4. There,
A probe scanning step (S2) for moving the probe antenna to a plurality of measurement positions;
A signal receiving step (S3) of receiving a radio signal by the probe antenna at a measurement position where the probe antenna is moved in the probe scanning step;
A quadrature detection step (S4) for outputting a real component and an imaginary component of the waveform of the radio signal received in the signal reception step;
An amplitude calculation step (S5) for calculating the amplitude of the radio signal received in the signal reception step from the real number component and the imaginary number component output in the orthogonal detection step;
A phase calculation step (S6) for outputting, as phase information, a value obtained by calculating the phase of the radio signal received in the signal reception step from the real number component and the imaginary number component output in the quadrature detection step;
An amplitude determination step (S9) for determining whether the amplitude calculated in the amplitude calculation step is equal to or less than a certain lower limit amplitude value;
For the measurement position at which the amplitude is determined to be less than or equal to the lower limit amplitude value in the amplitude determination step, the amplitude value is replaced with zero and output as amplitude information, and the amplitude is lower than the lower limit value in the amplitude determination step. An amplitude correction step (S10) for outputting the amplitude value as amplitude information for a measurement position determined not to be less than or equal to the amplitude value;
A near-field directivity calculating step (S11) for calculating a far-field directivity using the amplitude information and the phase information. A near-field measurement method for measuring in the near field the amplitude and phase of a radio signal transmitted from the antenna under measurement (100) using the near-field measurement device according to any one of claims 2 to 4. There,
A probe scanning step (S22) for moving the probe antenna to a plurality of measurement positions;
A signal receiving step (S23) for receiving the radio signal by the probe antenna at a measurement position where the probe antenna is moved in the probe scanning step;
A quadrature detection step (S24) for outputting a real component and an imaginary component of the waveform of the radio signal received in the signal receiving step;
An amplitude calculation step (S25) for outputting, as amplitude information, a value obtained by calculating the amplitude of the radio signal received in the signal reception step from the real component and the imaginary component output in the orthogonal detection step;
A phase calculation step (S26) for calculating the phase of the radio signal received in the signal reception step from the real number component and the imaginary number component output in the orthogonal detection step;
An amplitude determination step (S29) for determining whether the amplitude calculated in the amplitude calculation step is equal to or less than a certain lower limit amplitude value;
For the measurement position where the amplitude is determined to be less than or equal to the lower limit amplitude value in the amplitude determination step, the phase value calculated in the phase calculation step is replaced with a random value in the range of 0 ° to 360 °. A phase correction step for outputting as phase information the phase value calculated in the phase calculation step for the measurement position that is output as phase information and the amplitude determined in the amplitude determination step is not less than or equal to the lower limit amplitude value (S30),
A near-field directivity calculating step (S31) for calculating a far-field directivity using the amplitude information and the phase information.