Antenna measuring station

Abstract

Method for determining the antenna gain of an antenna (21) to be tested in free space, wherein the method comprises the following steps: Acquisition of measurement results of a transmitted power of a measurement signal (24a, 24b) transmitted between a reference antenna (22) and an antenna to be tested (21); Determining an input reflection factor ( P e _ TP e _ R ) | P g _ R = 0 the antenna (21) to be tested and an input reflection factor ( P g _ TP g _ R ) | P e _ R = 0 the reference antenna (22); Detecting polarization losses based on an angle between the unit vector of the electric field vector (p̂) T ) the antenna (21) to be tested and the electric field vector (p̂ R ) the reference antenna (22); where the detection takes place in the frequency domain; Converting the recorded measurement results into the time domain; Applying a time domain filter (26) to the measurement results converted into the time domain, wherein a filter width of the time domain filter (26) is determined as a function of a spatial distance (r) between the reference antenna (22) and the antenna (21) to be tested, so that measurement result components (24b) resulting from multipath propagation of the measurement signal (24a, 24b) between the reference antenna (22) and the antenna (21) to be tested are reduced or removed; Converting the filtered measurement results into the frequency domain; and Determining the antenna gain G T (ϑ, φ) of the antenna (21) to be tested, taking into account the recorded input reflection factors and polarization losses, based on the filtered measurement results available in the frequency domain using the following equation: GT ( ϑ , ϕ ) = 10 log 10 ( P _ TP g _ R ) − 20 log 10 ( λ 4 π r ) − GREF ( ϑ , φ ) − ( 10 log ( 1 − ( P _ TP g _ R ) | P g _ R = 0 ) + 10 log ( 1 − ( P g _ TP g _ R ) |. P _ R = 0 ) + 20 log |

Description

[0001] The invention relates to a method for determining an antenna characteristic of an antenna to be tested in free space, a device for determining an antenna characteristic of an antenna to be tested in free space, and an antenna measuring station for determining an antenna characteristic of an antenna to be tested in free space (reflection-free) with the features of the respective independent claims.

[0002] The economic use of millimeter (mm) and terahertz (THz) waves has increased significantly in recent years. Worldwide, intensive research is currently underway on the practical application of mm and THz waves for communication and radar applications. This frequency range offers many important advantages. The most illustrative examples are future wireless video signal transmission, for instance to projectors using the new high-speed WLAN standard IEEE 802.11ad in the 60 GHz band, and the application of 79 GHz automotive radar for detecting a car's surroundings during autonomous driving.

[0003] However, millimeter waves have some disadvantages due to their inherent physical properties, such as a short range resulting from high attenuation and reflection by many solid and liquid materials. Through targeted technical developments, these disadvantages can be circumvented or even specifically utilized for the desired application (e.g., near-field communication).

[0004] The central theme in these technical developments is antennas for optimal transmission and reception of mm and THz waves. Accordingly, antenna developments, and the associated measurement technology for characterizing antenna properties, will significantly influence the use of mm and THz waves.

[0005] Today, shielded cabinets are typically used for the metrological characterization of antennas for mm-wave applications. Fig. Figure 15 shows an example of a shielded cabinet, such as the one currently used at the Fraunhofer IZM institute. Antenna measurements are very time-consuming nowadays and must be carried out by experienced high-frequency (HF) specialists.

[0006] These expensive shielded cabins, the need for highly qualified RF specialists to carry out the measurements, and the high time expenditure for carrying out the measurements are obstacles to the development of mm and THz wave antennas and the quality assurance of these antennas in production.

[0007] The state of the art [1] to [5] includes scientific and commercial systems. The scientific systems are all based on a similar principle. A linearly polarized standard gain horn antenna is mounted on a rotatable arm. The arm is used to guide the standard gain horn antenna around the antenna to be measured.

[0008] Commercial systems are offered exclusively in shielded cabins or with shielded cabins, and these systems are based on frequency-range measurement methods or near-field measurement methods.

[0009] A method for determining antenna gain using the substitution method is described in Andrew M. Predoehl's master's thesis, dated June 1996 (Predoehl, AM: Time Domain Antenna Pattern Measurements. Master Thesis, Virginia Polytechnic Institute and State University, USA, June 1996). The method described therein always requires a relative measurement of the antenna pattern of the test antenna and a subsequent comparison with the transmission coefficients of a standard antenna. From this, the antenna gain of the test antenna can be estimated. Additionally, a reference measurement must be performed to estimate the surrounding environment.

[0010] Known systems therefore require a free field, or at least an estimate of the environment, to obtain reproducible measurement results and thus reliable statements about the characteristics of an antenna under test. However, such free-field conditions can only be artificially created with considerable effort, namely by providing so-called low-reflection rooms. Therefore, a conventional test setup requires a great deal of space (for example, the dimensions of the shielded booth at Fraunhofer IZM are 5 × 3 m). 2 ), especially when compared to the actual size of an antenna under test for the millimeter or terahertz range. Furthermore, qualified personnel are required to perform the RF measurements.

[0011] It would therefore be desirable to provide a method and a device for determining the antenna characteristics of an antenna under test that addresses the aforementioned problems from the prior art.

[0012] This problem is solved according to the invention by a method as well as with a device and an antenna measuring station with the features of the respective independent patent claims.

[0013] The method according to the invention offers the significant advantage that the antenna characteristics of an antenna under test can be determined in free space. The term "free space" must be clearly distinguished here from the previously mentioned term "free field." A free field refers to a field situation in which no reflections occur. Free field conditions can be artificially created in anechoic chambers or shielded booths. With the method according to the invention, however, it is possible to test the antenna in free space, that is, in any space, which does not necessarily have to be anechoic. Thus, the method according to the invention can, for example, be carried out in almost any (laboratory) space to determine the antenna characteristics of an antenna under test. The method according to the invention therefore eliminates the need for shielded booths with separate wave shielding and / or shielding material.Absorber material. In the method according to the invention, a measurement signal is transmitted between a reference antenna and an antenna under test. The measurement results of the transmitted power of this measurement signal are acquired in the frequency domain. The acquired measurement results are then converted into the time domain. A time-domain filter is also provided, e.g., in the form of a bandpass filter (which only allows power within a specific time range to pass through). The filter bandwidth of this time-domain filter is determined, among other things, by the spatial distance between the reference antenna and the antenna under test. This spatial distance is, for example, the shortest distance between the two antennas. This also characterizes the so-called direct path of the signal transmission. Knowing the signal parameters of a measurement signal, e.g., the wavelength, the propagation time between the two antennas in the direct path can be determined.On the other hand, signal components that are not transmitted via the direct path have longer propagation times, as they are reflected, for example, by obstacles in the environment and arrive at the receiver as reflected signal components with a longer travel time. These signal components are transmitted via an indirect path in the form of so-called multipath propagation between the reference antenna and the antenna under test. The time domain filter can therefore be selected so that only the signal components transmitted via the direct path can pass through the filter. Measurement result components that arise due to multipath propagation of the measurement signal between the reference antenna and the antenna under test are thus removed. A tolerance of, for example, ±10% or ±20% around the signal propagation time on the direct path can also be set.Measurement result components resulting from multipath propagation of the measurement signal between the reference antenna and the antenna under test are thus reduced. According to the invention, a time-domain filter is applied to the measurement results converted into the time domain. The filter bandwidth of the time-domain filter is determined as a function of the spatial distance between the reference antenna and the antenna under test, so that measurement result components resulting from multipath propagation of the measurement signal between the reference antenna and the antenna under test are reduced or eliminated. After applying the time-domain filter, the filtered measurement results are converted back into the frequency domain. Based on the filtered measurement results available in the frequency domain, the antenna gain G is then determined using the method according to the invention. T(ϑ, φ) of the antenna to be tested were determined using the following equation: GT(ϑ,φ)=10log10(Pe_TPg_R)−20log10(λ4πr)−GREF(ϑ,φ)−(10log(1−(Pe_TPe_R)|Pg_R=0)+10log(1−(Pg_TPg_R)|Pe_R=0)+20log|p^R⋅p^T|) where • G T (ϑ, φ) denotes the antenna gain of the antenna under test (abbreviation AUT) as a function of the solid angle, i.e. an azimuth angle φ and an elevation angle ϑ, • G REF (ϑ, φ) denotes the antenna gain of the reference antenna as a function of the solid angle, i.e. an azimuth angle φ and an elevation angle ϑ, • P g_R The term refers to the power of a signal (transmission) flowing into the reference antenna. • P g_T The term refers to the power of a signal emanating from the reference antenna (receiving). • P e_R refers to the power of a signal (transmission) flowing into the antenna under test, and • Pe_T This refers to the power output of a signal (receiving) from the antenna being tested. • Polarization losses arise because there is an angle between the unit vector and the electric field vector of the antenna under test (p̂ T ) and that of the reference antenna (p̂ R ) lies. • Reflections occur at the transition from the cable to the respective antenna because there is a discontinuity between the characteristic impedance of the cable and the antenna. This effect is represented in the equation above by the two terms 10log(Pe_TPe_R)|PgR=0 (antenna to be tested) and 10log(Pg_TPg_R)|PerR=0 (Reference antenna) taken into account.

[0014] The antenna gain G can therefore be determined using the method according to the invention. T(ϑ, φ) of an antenna under test can be determined as a function of the solid angle and taking into account reflection and polarization losses. It should be emphasized again that, in contrast to the prior art, the method according to the invention is suitable for determining the antenna gain in free space, i.e., without the need for a shielded enclosure.

[0015] According to one embodiment of the method according to the invention, when acquiring the measurement results, the reference antenna can be moved to different measurement positions relative to the antenna under test. In each of these different measurement positions, the power of a measurement signal transmitted via a free-space path at a specific wavelength λ and the spatial distance between the reference antenna and the antenna under test can be measured in the frequency domain for various solid angles (ϑ, φ) with elevation angle ϑ and azimuth angle φ. A measurement position is understood to be the orientation of the antenna under test relative to the reference antenna. The antenna under test can preferably be rotatable by 360° in a first (e.g., horizontal) plane. In a second (e.g., vertical) plane perpendicular to the first plane, the reference antenna can be movable by ±90° relative to the antenna under test.Thus, a complete sphere around the antenna under test can be mapped, in which the antenna gain of the antenna under test can also be determined.

[0016] According to further embodiments of the method of the invention, an input reflection factor can be (Pe_TPe_R)|Pg_R=0 the antenna to be tested and an input reflection factor of the reference antenna (Pg_TPg_R)|Pe_R=0 This can be determined. For this purpose, a VNA (Vector Network Analyzer) can be used, which has been calibrated via an easy-to-use electrical calibration module (eCal). An electrical calibration module contains all the necessary calibration standards (line, reflection standard, e.g., open or short-circuited lines and a very short line) and can switch electronically to the required standards, which significantly speeds up the calibration. Thus, the electrical influences of the cables and the measurement tolerances of the two antennas are taken into account. The antenna gain G T (ϑ, φ) of the antenna to be tested is thus determined taking into account the recorded input reflection factors by including these input reflection factors as terms in the equation according to the invention.

[0017] According to further embodiments of the method of the invention, the measurement signal power P flowing into the reference antenna can be g_R and the measurement signal power P emanating from the antenna under test e_T Polarization losses can be determined for various solid angles ϑ, φ. Furthermore, polarization losses can be calculated based on an angle between the unit vector of the electric field vector p̂. T the antenna to be tested and the electric field vector p̂ R The reference antenna is measured. The antenna gain G T (ϑ, φ) of the antenna to be tested is thus determined taking into account the measured signal powers and polarization losses by including these field vectors as terms in the equation according to the invention.

[0018] According to further embodiments of the method according to the invention, when measuring polarization losses, the polarization of the reference antenna can be rotated by 90° relative to the polarization of the antenna under test (electrically or mechanically). This allows polarization losses to be determined.

[0019] According to further embodiments of the method according to the invention, the spatial distance and / or the orientation between the antenna to be tested and the reference antenna can be detected by means of laser radiation. This can be done, for example, using a laser measuring device that measures the distance and the angle between the two antennas.

[0020] Another aspect of the invention provides a device for determining the antenna characteristics of an antenna under test in free space. The device includes, among other things, means for acquiring measurement results of the transmitted power of a measurement signal transmitted between a reference antenna and the antenna under test. The measurement results are acquired in the frequency domain. The device according to the invention also includes a control device configured to convert the measurement results into the time domain. Furthermore, the device includes a time-domain filter. The control device is configured to apply the time-domain filter to the measurement results converted into the time domain, the filter bandwidth of the time-domain filter being determined as a function of the spatial distance between the reference antenna and the antenna under test.Applying the time-domain filter to the measurement results reduces or eliminates components of the measurement results that arise due to multipath propagation of the measurement signal between the reference antenna and the antenna under test. Furthermore, the control device is designed to convert the filtered measurement results into the frequency domain and to determine the antenna gain of the antenna under test based on the filtered, frequency-domain measurement results, using the following equation: GT(ϑ,φ)=10log10(Pe_TPg_R)−20log10(λ4πr)−GREF(ϑ,φ)−(10log(1−(Pe_TPe_R)|Pg_R=0)+10log(1−(Pg_TPg_R)|Pe_R=0)+20log|p^R⋅p^T|) For an explanation of the individual terms, reference is made to the above explanations of the method according to the invention.

[0021] According to embodiments of the present invention, the device can have a means for moving the reference antenna relative to the antenna under test into different measurement positions, and the control device can be configured to detect, in each of the different measurement positions, the power of a measurement signal transmitted via a free-space path at a frequency f and the spatial distance between a reference antenna and the antenna under test in the frequency domain for different solid angles ϑ, φ with elevation angle ϑ and azimuth angle φ.

[0022] According to further embodiments of the present invention, the means for acquiring measurement results can be configured to include an input reflection factor. (Pe_TPe_R)|Pg_R=0 the antenna to be tested and an input reflection factor of the reference antenna (Pg_TPg_R)|Pe_R=0 to determine. The control device can be designed to determine the antenna gain G. T (ϑ, φ) of the antenna to be tested by applying the equation according to the invention and taking into account the input reflection factors, wherein the input reflection factors are included as terms in the equation according to the invention.

[0023] According to further embodiments of the present invention, the means for acquiring measurement results can be configured to measure the measurement signal power P flowing into the reference antenna. g_R and the measurement signal power P emanating from the antenna under test e_T to measure for different solid angles ϑ, φ. Reflection losses can be taken into account using the measured signal powers. Furthermore, the means for acquiring the measurement results can be designed to determine the angle between the unit vector and the electric field vector (p̂). T) the antenna to be tested and the electric field vector (p̂ R ) of the reference antenna. Polarization losses can be taken into account using the measured angles. The control device is designed to adjust the antenna gain G. T (ϑ, φ) of the antenna to be tested, taking into account reflection losses and polarization losses.

[0024] According to further embodiments of the present invention, the means for acquiring measurement results can further comprise a transmitter stage which includes, in the signal direction, a mixer, an amplifier, a switching matrix, and a transmitting antenna. Thus, in the transmitter stage, a signal to be transmitted can be upmixed to an intermediate frequency by means of the mixer and amplified by means of the amplifier. The switching matrix then allows switching back and forth between, for example, the antenna or the calibration module with virtually no loss and in a straightforward manner. The amplified signal can thus be routed either to the antenna or to the calibration module.

[0025] According to further embodiments of the present invention, the means for acquiring measurement results can include a receiving stage comprising, in the signal direction, a receiving antenna, a switching matrix, an amplifier, and a mixer. Thus, the receiving stage can amplify a received signal by means of the amplifier and downmix it to a signal frequency by means of the mixer. The switching matrix can also be used in the receiving stage to switch, for example, between the receiving antenna and a calibration module. It would also be conceivable that the switching matrix could be used to switch between different intermediate frequency generators (e.g., local oscillators) with different frequency ranges.

[0026] According to further embodiments of the present invention, the control device can be configured to control the transmitting stage and / or the receiving stage such that the polarization of the transmitting stage is rotated by 90° relative to the receiving stage, wherein the rotation is effected by controlling the switching matrix of the transmitting stage and / or the receiving stage. By means of the switching matrix, the polarization of the reference antenna can thus be rotated by 90° relative to the antenna under test in a virtually lossless and straightforward manner. The switching matrix therefore eliminates the need for manually switching the polarization of a dual-polarized antenna, and in particular the manual rotation of known linearly polarized standard gain horn antennas.

[0027] Another aspect of the invention relates to an antenna test setup for determining the antenna characteristics of an antenna under test in free space. Here again, the difference between the terms "free field" and "free space" should be explicitly emphasized. The term "free space" must be clearly distinguished from the previously mentioned term "free field." A free field describes a sound or field situation in which no reflections occur. Free field conditions can be artificially created in anechoic chambers or shielded booths. With the antenna test setup according to the invention, however, it is possible to test the antenna in free space, that is, in any space, which does not necessarily have to be anechoic. Thus, the antenna test setup according to the invention can, for example, be installed in almost any (laboratory) room to determine the antenna characteristics of an antenna under test.The antenna test setup according to the invention eliminates the need for shielded booths with separate wave shielding and / or shielding or absorber material. The antenna test setup according to the invention includes, among other things, an antenna measuring device with a transmitter module and a receiver module. The antenna measuring device can generate measurement signals or test signals, transmit them via the transmitter module, receive them via the receiver module, and measure the received signal, e.g., with regard to signal strength and the like. The antenna test setup also includes an antenna to be tested and a reference antenna. The transmitter module is coupled to at least one of the two antennas, e.g., by means of a suitable signal line. That is, the transmitter module can, for example, be coupled to the reference antenna. In that case, the transmitter module would send a test signal via the reference antenna.The same applies in reverse, of course, if the transmitting module were coupled to the antenna under test. The receiving module is coupled to the other of the two antennas. That is, if the transmitting module is coupled to the reference antenna, then the receiving module would be coupled to the antenna under test. The antenna test setup also includes a control device that performs a variety of different functions. Among other things, the control device is designed to control the transmitting and receiving modules, such that the transmitting module sends out a test signal via one of the two antennas, and the receiving module receives the test signal in the frequency domain via the other of the two antennas. The receiving module, coupled to the antenna tester, thus forwards the received signal to the antenna tester, which processes the received signal in the frequency domain. The antenna test setup also includes a time domain filter, e.g.A bandpass filter is used. The filter bandwidth of the time-domain filter is determined by the spatial distance between the antenna under test and the reference antenna. This spatial distance is, for example, the shortest distance between the two antennas. This also defines the so-called direct path of signal transmission. Knowing the signal parameters of a measurement signal, such as the wavelength, the propagation time between the two antennas in the direct path can be determined. On the other hand, signal components that are not transmitted in the direct path have longer propagation times because they are reflected, for example, by obstacles in the environment and arrive at the receiver as reflected signal components with a longer propagation time. These signal components are transmitted on an indirect path in the form of so-called multipath propagation between the reference antenna and the antenna under test.The time-domain filter can therefore be selected so that only the signal components transmitted via the direct path can pass through the filter. Measurement result components resulting from multipath propagation of the measurement signal between the reference antenna and the antenna under test are thus removed. A tolerance of, for example, ±10% or ±20% of the signal propagation time of a signal transmitted via the direct path can also be set. Measurement result components resulting from multipath propagation of the measurement signal between the reference antenna and the antenna under test are thus reduced. Signal components lying outside the selected filter bandwidth are filtered out. The control device is structurally designed to convert the test signal received in the frequency domain into the time domain and to apply the time-domain filter to the received test signal in order to filter out test signal components lying outside the filter bandwidth.Furthermore, the control device is designed to convert the filtered test signal, which is present in the time domain, back into the frequency domain. In addition, the control device is designed to determine the antenna gain of the antenna under test from the converted test signal using the following equation: GT(ϑ,φ)=10log10(Pe_TPg_R)−20log10(λ4πr)−GREF(ϑ,φ)−(10log(1−(Pe_TPe_R)|Pg_R=0)+10log(1−(Pg_TPg_R)|Pe_R=0)+20log|p^R⋅p^T|) where • G T (ϑ, φ) denotes the antenna gain of the antenna under test (abbreviation AUT) as a function of the solid angle, i.e. an azimuth angle φ and an elevation angle ϑ, • G REF (ϑ, φ) denotes the antenna gain of the reference antenna as a function of the solid angle, i.e. an azimuth angle φ and an elevation angle ϑ, • P g_RThe term refers to the power of a signal (transmission) flowing into the reference antenna. • P g_T The term refers to the power of a signal emanating from the reference antenna (receiving). • P e_R refers to the power of a signal (transmission) flowing into the antenna under test, and • P e_T This refers to the power output of a signal (receiving) from the antenna being tested. • Polarization losses arise because there is an angle between the unit vector and the electric field vector of the antenna under test (p̂ T ) and that of the reference antenna (p̂ R ) lies. • Reflections occur at the transition from the cable to the respective antenna because there is a discontinuity between the characteristic impedance of the cable and the antenna. This effect is represented in the equation above by the two terms 10log(Pe_TPe_R)|PgR=0 (antenna to be tested) and 10log(Pg_TPg_R)|PerR=0 (Reference antenna) taken into account.

[0028] The antenna measurement setup according to the invention can therefore be used to determine the antenna gain G. T (ϑ, φ) of an antenna under test can be determined as a function of the solid angle and taking into account reflection and polarization losses. It should be emphasized again that the antenna test setup according to the invention, in contrast to the prior art, is suitable for determining the antenna gain in free space, i.e., without the need for a shielded enclosure.

[0029] According to embodiments of the invention, the reference antenna and / or the antenna under test can be configured to transmit and / or receive radiation in a frequency range between 1 GHz and 10 THz, or between 50 GHz and 1.1 THz, or between 50 GHz and 100 GHz. These are millimeter or terahertz waves. These antennas are used, for example, in future wireless video signal transmissions, such as to projectors using the new high-speed WLAN standard IEEE 802.11ad in the 60 GHz band. Further application examples for such antennas include the fifth generation of the 5G mobile communication standard, E-band wireless backhaul, or future 100 Gbps wireless communication applications using frequencies around 0.3 THz.It is also conceivable to use such antennas in 79 GHz automotive radar for detecting the surroundings of a vehicle during autonomous driving, or in 94 GHz radar as well as future industrial radar applications in the 0.122 THz and 0.24 THz ranges.

[0030] According to further embodiments of the antenna test setup according to the invention, the control device can be configured to determine the spatial distance between the reference antenna and the antenna under test and / or the orientation of the reference antenna relative to the antenna under test. This is particularly advantageous before a measurement. This can be done either before each individual measurement or before a measurement block consisting of several individual measurements. By determining the distance between the two antennas, the direct path for determining the signal propagation time, and thus for determining the filter bandwidth of the time-domain filter, can be determined. By determining the (angular) position of the two antennas relative to each other, polarization losses can be compensated.

[0031] According to further embodiments of the antenna test setup according to the invention, the antenna test setup can include a laser measuring device configured to determine the spatial distance and / or an angle of the reference antenna relative to the antenna under test. A laser measuring device operates very precisely and is suitable for distance and angle measurements with very low tolerances. This significantly increases the accuracy in calculating the antenna gain of the antenna under test.

[0032] According to further embodiments of the antenna test setup according to the invention, the receiving stage can include a switching matrix, an amplifier, and a mixer in the direction of signal propagation of the test signal. Thus, the receiving stage can amplify a received signal using the amplifier and downmix it to a signal frequency using the mixer. The switching matrix can also be used in the receiving stage to switch between, for example, the receiving antenna and a calibration module. It would also be conceivable to use the switching matrix to switch between different intermediate frequency generators (e.g., local oscillators) with different frequency ranges.

[0033] According to further embodiments of the antenna test setup according to the invention, the transmitter stage can include a mixer, an amplifier, and a switching matrix in the direction of signal propagation of the test signal. Thus, in the transmitter stage, the signal to be transmitted can be upmixed to an intermediate frequency by means of the mixer and amplified by means of the amplifier. The switching matrix then allows for virtually lossless and straightforward switching back and forth, for example, between the antenna and a calibration module. The amplified signal can thus be routed either to the antenna or to the calibration module.

[0034] According to further embodiments of the antenna test setup according to the invention, the reference antenna can be a dual-polarized antenna, and the control device can be configured to rotate the polarization of the reference antenna by 90° using the switching matrix. The switching matrix can be implemented as a mechanical and / or electrical switch that can switch back and forth between at least two states. For example, an electrical switch can be used to switch back and forth between a first and a second polarization of a dual-polarized antenna with essentially no loss.

[0035] According to further embodiments of the antenna test setup according to the invention, the antenna test setup can have a rotatable table on which the antenna to be tested can be arranged. For example, the table can be a motor-driven table, with the control device configured to rotate the table. The antenna to be tested, arranged on the table, can be electrically contacted, for example, by means of a probe or by means of connectors. As mentioned, the control device can be configured to rotate the table so that when the table is rotated, the antenna to be tested rotates together with the table in a first plane (horizontal antenna plane). This rotation changes an azimuth angle φ between the reference antenna and the antenna to be tested. The table can preferably be rotatable through 360°. The table can also be continuously rotatable.This allows the entire horizontal antenna plane to be scanned for measuring the antenna under test.

[0036] According to further embodiments of the antenna test setup according to the invention, the antenna test setup can have a receiving device for movably holding the reference antenna. Such a receiving device can, for example, be a support or an arm on which the reference antenna is movably arranged. Preferably, this can be a semicircular arm that extends at least partially around the rotatable table. The control device can be configured to move the reference antenna along the receiving device relative to the antenna under test in a second plane (vertical antenna plane) perpendicular to the first plane. In this way, an elevation angle ϑ between the reference antenna and the antenna under test can be changed.

[0037] According to further embodiments of the antenna test setup according to the invention, the antenna test setup can include a test signal generator. The test signal generator can be an integral part of the antenna test device. The test signal generator can be configured to generate the test signal and transmit it to the transmitter module. The transmitter module has a first integrated transmitter stage and a second integrated transmitter stage. The first transmitter stage has a frequency mixer for upmixing the test signal into a first frequency band, and the second transmitter stage has a frequency mixer for upmixing the test signal into a second frequency band. The frequency bands differ but can also overlap, at least to some extent. For example, the frequency band of the first transmitter stage can cover a range from 70 GHz to 110 GHz, and the frequency band of the second transmitter stage can cover a range from 110 GHz to 170 GHz.More than two transmission stages, each with different frequency bands, are also possible. The transmission module always has a switch for selectively choosing the desired transmission stage. Thus, multiple transmission stages can be integrated into a single transmission module. Switching between the individual transmission stages is easily accomplished with a switch, allowing a test signal to be upmixed into different frequency bands.

[0038] Exemplary embodiments of the invention are shown in the drawing and are explained below. They show: Fig. 1 a block diagram of a method according to the invention, Fig. 2 a block diagram of a device according to the invention, Fig. 3 a block diagram of an antenna measuring station according to the invention, Fig. 4 A schematic diagram illustrating signal transmission in direct and indirect paths, Fig. 5. A diagram showing the received signal strength over time. Fig. 6. A schematic diagram illustrating power flows that can be transmitted between two antennas. Fig. 7 an embodiment of an antenna measuring station according to the invention, Fig. 8 another embodiment of an antenna measuring station according to the invention, Fig. 9A a block diagram of a receiver stage, Fig. 9B a block diagram of a transmitter stage, Fig. 10 a detailed block diagram of an exemplary transmitter stage, Fig. 11 a block diagram of an eCal calibration module, Fig. 12 a block diagram of an example of a method according to the invention, Fig. 13 a flowchart of another example of a method according to the invention, Fig. 14 a block diagram to illustrate the device components in connection with the process steps, and Fig. 15 a conventional umbrella cabin from the state of the art.

[0039] First, with reference to Fig. 1 the method according to the invention is described.

[0040] Block 101 records measurement results of the power transmitted by a measurement signal transmitted between a reference antenna and an antenna under test, with the recording taking place in the frequency domain.

[0041] In block 102, the recorded measurement results are converted into the time domain.

[0042] In block 103, a time domain filter is applied to the measurement results converted into the time domain, whereby a filter width of the time domain filter is determined as a function of a spatial distance between the reference antenna and the antenna under test, so that measurement result components that result from multipath propagation of the measurement signal between the reference antenna and the antenna under test are reduced or removed.

[0043] In block 104, the filtered measurement results are converted into the frequency domain.

[0044] In block 105, the antenna gain G T (ϑ, φ) of the antenna to be tested, based on the filtered measurement results available in the frequency domain, determined using the following equation: GT(ϑ,φ)=10log10(Pe_TPg_R)−20log10(λ4πr)−GREF(ϑ,φ)−(10log(1−(Pe_TPe_R)|Pg_R=0)+10log(1−(Pg_TPg_R)|Pe_R=0)+20log|p^R⋅p^T|)

[0045] Fig. Figure 2 shows a device 20 for determining an antenna characteristic of an antenna 21 to be tested in free space.

[0046] The device 20 has means 23 for acquiring measurement results of a transmitted power of a measurement signal 24a, 24b transmitted between a reference antenna 22 and an antenna 21 under test. The measurement results are acquired in the frequency domain.

[0047] The device 20 further comprises a control device 25. The control device 25 is designed to convert the measurement results into the time domain.

[0048] The device 20 also includes a time-domain filter 26. The control device 25 is configured to apply the time-domain filter 26 to the measurement results converted into the time domain.

[0049] The filter bandwidth of the time-domain filter 26 is determined as a function of a spatial distance r between the reference antenna 22 and the antenna 21 under test. This is explained below with reference to the Fig. 4 and Fig. 5 will be explained in more detail.

[0050] The distance r, represented by arrow 27, between the reference antenna 22 and the antenna 21 under test simultaneously represents the direct path of the signal transmission. This means that the signal components 24a, which are transmitted directly from the reference antenna 22 to the antenna 21 under test, have the shortest signal propagation time.

[0051] In addition, there are signal components 24b that are not transmitted via the direct path. These signal components can, for example, be reflected by objects 28 in the environment. These reflected signal components 24b have a correspondingly longer propagation time, as they have to travel a longer distance compared to the signal components 24a transmitted via the direct path. The reflected signal components 24b are, so to speak, multipath propagation, meaning they are transmitted via an indirect path between the reference antenna 22 and the antenna 21 under test.

[0052] The filter width of the time domain filter 26 is adjusted so that those measurement result components 24b that result from multipath propagation of the measurement signal between the reference antenna 22 and the antenna 21 under test are reduced or removed.

[0053] According to the invention, the control device 25 is configured to convert the filtered measurement results into the frequency domain. Furthermore, the control device 25 is configured to determine the antenna gain of the antenna 21 to be tested based on the filtered measurement results available in the frequency domain, using equation (1).

[0054] Fig. Figure 3 shows an antenna test setup 30 according to the invention for determining the antenna characteristics of an antenna 31 to be tested in free space. The antenna test setup 30 includes, among other things, an antenna tester 33 with a transmitter module 38 and a receiver module 39.

[0055] The antenna test station 30 also includes an antenna 31 to be tested and a reference antenna 32. The transmitter module 38 is coupled to at least one of the two antennas 31, 32. In the Fig. In the embodiment shown in Figure 3, the transmitter module 38 is coupled to the reference antenna 32. It is also conceivable that the transmitter module 38 is coupled to the antenna 31 under test. Likewise, it would be conceivable that the transmitter module 38 is coupled to both antennas 31 and 32.

[0056] The receiver module 39 is coupled to at least the other of the two antennas 31, 32. In the Fig. In the embodiment shown in Figure 3, the receiving module 39 is coupled to the antenna 31 under test. It is also conceivable that the receiving module 39 is coupled to the reference antenna 32. Likewise, it would be conceivable that the receiving module 39 is coupled to both antennas 31 and 32.

[0057] The antenna test setup 30 also includes a time-domain filter 36. The filter bandwidth of the time-domain filter 36 is determined as a function of a spatial distance r between the antenna 31 under test and the reference antenna 32. Regarding the spatial distance r and the associated direct path, reference is made to the above explanations. Fig. 2 referred.

[0058] The antenna test station 30 includes a control device 35. The control device 35 is configured to control the transmitting module 38 and the receiving module 39 such that the transmitting module 38 sends a test signal 34a, 34b via one of the two antennas 31, 32, and the receiving module 39 receives the test signal 34a, 34b via the other of the two antennas 31, 32. The test signal can include test signal components 34a that are transmitted on the direct path between the two antennas 31, 32, as well as test signal components 34b that are transmitted on an indirect path between the two antennas 31, 32.

[0059] The control device 35 is further configured to convert the test signal 34a, 34b received in the frequency domain into the time domain. The control device 35 also applies the time domain filter 36 to the received test signal, specifically to the time-domain-converted test signal. This allows test signal components lying outside the filter bandwidth to be filtered out. For example, the filter bandwidth can be determined such that only the test signal components 34a transmitted via the direct path can pass through the time domain filter 36, while the test signal components 34b transmitted via the indirect path are filtered out by the time domain filter 36.

[0060] The control device 35 is also designed to convert the filtered test signal present in the time domain back into the frequency domain and to determine the antenna gain of the antenna 31 to be tested as a function of a certain solid angle using equation (1) from the test signal converted back into the frequency domain.

[0061] With regard to the Fig. 4 and Fig. Section 5 below will illustrate the previously described signal propagation times of the test signal.

[0062] Fig. Figure 4 schematically shows a reference antenna 31 and an antenna 32 to be tested. The test signal includes both test signal components 34a, which are transmitted via the direct path between the two antennas 31, 32, and test signal components 34b, which are transmitted via indirect paths between the two antennas 31, 32. On the indirect paths, the test signal components 34b are reflected by objects or obstacles 41, 42 located in the vicinity or in free space.

[0063] Fig. Figure 5 shows a typical time-domain signal from a measurement using a measurement setup as shown in Figure 5. Fig. Figure 4 shows the amplitude of the measured signal over time.

[0064] It is clearly evident that the signal component 34a transmitted via the direct path has a significantly shorter propagation time than the signal components 34b transmitted via indirect paths. Since the signal exhibits the least attenuation on the direct path, it is understandable that the signal component 34a transmitted via the direct path has a larger amplitude compared to the signal components 34b transmitted via indirect paths.

[0065] According to the invention, the spatial distance r ( Fig. 4) between the two antennas 31, 32. Thus, if the wavelength or propagation speed of the time-domain signal is known, the propagation time of the signal on the direct path can be determined. A filter width 50 of the time-domain filter 36 can now be set, for example, so that only the signal components 34a transmitted on the direct path can pass through the filter 36, while the signal components 34b transmitted on indirect paths with a longer propagation time and smaller amplitude are filtered out by the filter 36. This method is also called time gating.

[0066] In an antenna test site, there is therefore one direct path and many indirect paths, as in Fig. Figure 4 illustrates this. The aim of filtering using the time-domain filter 36 is to eliminate the indirect paths so that these signal components 34b do not interfere with the actual power transmission or so that the measurement level does not change due to constructive interference, depending on the position. This signal change can also be interpreted as an interference signal.

[0067] In the prior art, the main strategy for reducing interference signals involves placing absorber material between the antennas and the environment. This significantly suppresses the interference signals (at least 30 dB). The absorber material limits measurements to enclosed spaces (e.g., anechoic chambers, shielded booths). The time-domain filtering described above overcomes this limitation, meaning that antennas 31 and 32 can also be measured in free space, i.e., outside of enclosed spaces (e.g., anechoic chambers, shielded booths).

[0068] In the time domain, the interference signal components 34b can be separated from the signal components 34a transmitted via the direct path and filtered out. This is because the direct path theoretically exhibits the shortest delay and simultaneously the greatest amplitude (see Fig. 5).

[0069] The time-domain filter 36 according to the invention thus serves to separate the direct path from environmental influences. Various measures can be taken for this purpose: a) ensure that no reflective objects 41, 42 are so close to the antennas 31, 32 that the indirect and direct paths overlap; b) Determining the direct path delay by determining the spatial distance r of the reference antenna 32 to the antenna 31 under test; and c) Determining the bandwidth from antenna type and room characteristics.

[0070] After the filter width of the time domain filter 36 has been determined, the control device 35 converts the filtered signal, or the filtered signal components 34a, back into the frequency domain.

[0071] Taking into account this filtered signal component 34a, the control device 35 then determines the antenna gain of the antenna 31 to be tested by applying equation (1).

[0072] Fig. Figure 6 shows, to illustrate equation (1) for calculating the antenna gain of an antenna 31 to be tested, the different signal powers of a test signal transmitted between a reference antenna 32 and an antenna 31 to be tested. Fig. Figure 6 shows two signal inputs 61 and 62. The first signal input 61 can, for example, be coupled to a transmitter module 38. The second signal input 62 can, for example, be coupled to a receiver module 39.

[0073] P g_R P denotes the power flowing into the reference antenna 32. g_T P denotes the power emanating from the reference antenna 32. e_R denotes the power flowing into the antenna 31 under test. P e_T denotes the power flowing out of the antenna 31 being tested.

[0074] Fig. Figure 7 shows an embodiment of an antenna measuring station 30 according to the invention. The antenna measuring station 30 is divided into a physical antenna measuring station 30a and an automated sequence control 30b. As can be seen, the antenna measuring station 30 according to the invention does not require separate wave shielding, e.g. by means of a shielded cabin.

[0075] The antenna measurement station 30 has a centralized control device 35. The control device 35 can have an output or display device 71 to show the measurement results to a user 72. The control device 35 can also have an input device 73, e.g. in the form of a keyboard 73, so that a user 72 can enter data.

[0076] The control device 35 includes a computer program according to the invention in the form of software stored on a storage medium. The software can include a sequence control software 74 for carrying out the method according to the invention, as well as further software 75 for acquiring, storing and evaluating the measurement signals.

[0077] Furthermore, the control device 35 can include electronic components 76 for controlling the transmitter module 38, as well as electronic components for controlling the rotating table 78. The control device 35 can also include electronic components for controlling the receiver module 39.

[0078] The antenna test setup 30a in question has a rotating table 78. The antenna 31 to be tested is arranged on this rotating table 78. The receiving module 39 is coupled to the antenna 31 to be tested.

[0079] The antenna measuring station 30 also has a calibration module 79. This is described below with reference to Fig. 11 described in more detail. The rotatable table 78 has a connector (e.g. coaxial or waveguide) by means of which the calibration module 79 can be connected.

[0080] The antenna measuring station 30 further comprises a receiving device 80 for movably receiving the reference antenna 32. The reference antenna 32 is coupled to the transmitting module 38. The transmitting module 39 or the reference antenna 32 is movable along the receiving device 80. The receiving device 80 is shown here as an approximately semicircular arm, so that the transmitting module 39 or the reference antenna 32 can be moved 180° (±90°) along this semicircle.

[0081] The modules are connected for calibration using the aforementioned calibration unit 79. The TRL method is used for calibration, which is described in relation to Fig. 11 is explained in more detail. The transmitter module 38 with a dual-polarized reference antenna 32 is movably mounted on the preferably semi-circular, rotating mounting device 80, which is rotatable by 180°.

[0082] The rotating table 78 and the receiving device 80 are arranged together on a vibration-protected table 81.

[0083] The antenna 31 to be tested is positioned on the rotatable table 78 and electrically connected to it via the necessary terminals. The table 78 is rotatable about its longitudinal axis 82. Preferably, the table 78 is continuously rotatable through 360°. As soon as the table 78 rotates, the antenna 31 to be tested also rotates. This rotation of the antenna 31 to be tested about the longitudinal axis 82 of the rotatable table 78 is called a rotation in a first plane. In the case shown here, the antenna 31 to be tested rotates about its horizontal plane, with the angle of rotation also being referred to as the azimuth angle φ.

[0084] In contrast, as the reference antenna 32 moves along the receiving device 80, it moves relative to the antenna 31 under test in a second plane perpendicular to the first plane. This second plane can therefore also be considered a vertical plane in which the antenna 31 under test is measured. The deflection angle of the reference antenna 32 relative to the antenna 31 under test is therefore also referred to as the elevation angle ϑ.

[0085] The 360° rotation of the antenna 31 under test in its horizontal plane, as described above, combined with the described deflection of the reference antenna 32 relative to the antenna 31 by ±90° (starting from the horizontal plane as the zero level), results in a complete sphere forming around the antenna 31 under test. The antenna 31 under test can thus be measured completely; that is, its radiation and reception characteristics can be determined throughout the entire space.

[0086] Fig. Figure 8 shows a slightly more detailed view of the antenna test site 30 just described. The same features as in Fig. 7 are also in Fig. 8 are marked with the same reference symbols, which is why reference is made to the paragraphs above for their explanation.

[0087] In Fig. Figure 8, however, shows more clearly how the reference antenna 32 can be moved along the receiving device 80. The reference antenna 32 can be moved in the direction of arrow 83 along the semicircular receiving device 80. An example is shown in Fig. Figure 8 shows the lower position of the reference antenna 32 in dashed lines. The lower position is designated with reference symbol 32' for the reference antenna and with reference symbol 38' for the transmitting module.

[0088] The reference antenna 32 is movable by ±90° relative to the horizontal plane of the antenna 31 under test, so that a semicircle is formed around the antenna 31 under test. Therefore, if the antenna 31 under test is rotated in its horizontal plane by means of the rotating table 78, as described above, and simultaneously the reference antenna 32 is moved along the semicircular receiving device, a complete sphere around the entire antenna 31 under test can be imaged.

[0089] The antenna 31 under test can be operated in both transmit and receive modes. In the exemplary embodiments shown in the figures, the reference antenna 32 is operated in transmit mode, and the antenna 31 under test is operated in receive mode. For this purpose, the reference antenna 32 is coupled to a transmit module 38, and the antenna 31 under test is coupled to a receive module 39.

[0090] It would also be conceivable that the antenna 31 under test is operated in a transmit mode, and the reference antenna 32 in a receive mode. In this case, the reference antenna 32 would be coupled to a receive module 39, and the antenna 31 under test would be coupled to a transmit module 38. It would also be conceivable that both antennas 31 and 32 could each be coupled to their own or a shared transmit and receive module.

[0091] Fig. Figure 9A shows a schematic block diagram of an exemplary receiver module 39 and Fig. Figure 9B shows a schematic block diagram of an exemplary transmitter module 38.

[0092] As in Fig. As shown in Figure 9A, the receiving module according to the invention includes a receiving stage with an ultra-wideband receiving antenna 91 (dual, linearly polarized) arranged in the direction of the signal, a switching matrix 92, an amplifier 93 and a mixer 94.

[0093] As in Fig. As shown in Figure 9B, the transmitter module contains a transmitter stage with a mixer 95, amplifier 96 and a switching matrix 97 arranged in the direction of the signal.

[0094] The receive / transmit modules 38 and 39 are adaptable / interchangeable to the respective frequency band. At the input of each receive / transmit module 38 or 39, a transmit signal, e.g., from 20 GHz, is up-converted / down-converted and amplified. The high frequencies are only present in the transmit / receive module and are then distributed to the individual frequency ranges.

[0095] The transmitter module 38 consists of various components that have been specially optimized for the antenna test setup 30 according to the invention. Compared to known systems from the prior art, the transmitter module 38 according to the invention has only one transmitter stage. This makes it possible to design the module to be compact yet powerful. Additionally, the transmitter stage for one or even several frequency systems is integrated within the transmitter module 38 so that the transmitter module 38 does not need to be changed when switching frequency ranges.

[0096] In Fig. Figure 10 shows an exemplary configuration of a transmitter module 38 according to the invention, comprising three transmitter stages 1001, 1002, and 1003. The transmitter stages 1001, 1002, and 1003 are driven by signals generated by a signal generator (e.g., a high-frequency measuring device) (e.g., up to 26.5 GHz). The individual transmitter stages 1001, 1002, and 1003 can be selectively controlled via an electrical or mechanical switch 1004.

[0097] As previously mentioned with reference to Fig. As described in Figure 9B, each transmitting stage 1001, 1002, 1003 has a frequency mixer 1005, 1006, 1007 and a signal amplifier 1008, 1009, 1010. The frequency of the input signal is upconverted to the respective high-frequency band by the respective mixer 1005, 1006, 1007 and amplified by the corresponding power amplifier 1008, 1009, 1010. The power is then routed to a mechanical or electrical switch 1011, which selectively directs the RF power to the transmitting antenna (reference antenna 32 or antenna 31 under test) or to the electrical calibration module 79.

[0098] The receiver module 39 is constructed similarly to the transmitter module 38. The difference is that only a 1-to-2 switch is required between the antenna 31 to be tested and the calibration unit 79.

[0099] The switch 1011 is particularly advantageous when the respective antenna 31, 32 is a dual-polarized antenna. For the purposes of this disclosure, the switch 1011 is also referred to as a switching matrix and essentially corresponds to the one described in Fig. 9B schematically represented switching matrix 97.

[0100] The application of such a dual-polarized antenna 31, 32 in an antenna test setup 30 according to the invention is significantly advantageous compared to the prior art. With the prior art application of horn antennas, which are typically used as reference standards, both polarizations must be measured. This is classically achieved by measuring the entire sphere with the first polarization and then with the second polarization. This is very time-consuming and expensive.

[0101] Known dual-polarized horn antennas ([6] -

[10] ) according to the prior art are broadband and generally operate in frequency ranges below 60 GHz. To increase the measurement efficiency of the antenna test setup 30 according to the invention, dual-polarized antennas for frequencies between 50 GHz and 100 GHz are advantageous, which can be designed as planar, horn or helical antennas.

[0102] The use of a dual-polarized antenna as a reference antenna 32 is therefore clearly advantageous and results in significant time and cost savings. Referring again to Fig. Therefore, in section 10, we will discuss the dual polarized antenna 32 in more detail, the polarization of which can be switched using the switch 1001.

[0103] When measuring an antenna 31 under test, a (top-mixed) test signal is transmitted by the reference antenna 32 at a specific position of the antenna 31 under test relative to the reference antenna 32. The switch position of the switch 1011 is selected such that the reference antenna 32 has a first polarization direction. The switch 1011 can then be switched so that the reference antenna 32 has a second polarization direction, this second polarization direction being offset by 90° from the first polarization direction.

[0104] Instead of such a dual-polarized antenna, linearly polarized antennas 32' can also be used. According to the invention, for example, a motor 1012 can then be used to rotate the linearly polarized antenna 32' by 90°. A switch can also be provided here to switch between the linearly polarized antenna 32' and the calibration module 79'.

[0105] The previously mentioned calibration module 79 could, for example, be a so-called eCal module. Fig. Figure 11 shows an example of a calibration module 79 as it can be used in an antenna measurement station 30 according to the invention.

[0106] The calibration module 79 consists of a control section and power section, as well as a radio frequency (RF) section. According to current technology, calibration can be implemented, for example, using the so-called Multi-Line TRL

[11] , which was developed by Marks in the 1990s. This calibration requires various standards (precisely defined RF structures). TRL stands for Thru (direct connection between the two ports; reflection (short circuit or open circuit)) and different line lengths. An electrical or mechanical switch is used to toggle between these configurations during calibration. The actual calibration procedure takes place either in the measuring instrument or in the control PC.

[0107] After the structural features of the devices 20, 30 according to the invention have been described in detail, the functioning of these devices will be described below with reference to the Fig. 12 to 14 explained in more detail.

[0108] First, in Fig. 12 describes an example of how the method according to the invention can be carried out using a device 20 according to the invention or with an antenna measuring station 30 according to the invention.

[0109] The automatic control of the test setup and measuring instruments is handled by a centralized computer. In the first step (Block 1201), the antenna 31 under test (AUT: Antenna Under Test) is placed in the test setup. The distance between the antenna 31 and the reference antenna 32, as well as their relative orientations, are automatically recorded and stored. This can be achieved, for example, with a laser measuring device. This device measures the distance and the angle between the two antennas 31 and 32.

[0110] Tilting of the reference antenna 32 can be avoided by fixing it to the mounting device 80 perpendicular to the surface. Subsequently, the electrical influences of the cables and the tolerances of the measuring instruments to the two antennas are calibrated using an easy-to-use electrical calibration module (eCal) 79 (Block 1202).

[0111] Automated measurements can be started via an intuitive graphical user interface (GUI of the central computer), requiring no expertise in high-frequency measurement technology (Block 1203). The GUI allows for the definition of the frequency range and spatial area. The horizontal plane can be covered from -180° to +180°, and the vertical plane from -90° to approximately +90°. The respective spatial angle is achieved through electronic control of the system.

[0112] The reference antenna 32 can be a dual-polarized antenna mounted on the receiving device 80. In contrast to a linearly polarized horn antenna, the dual-polarized antenna does not need to be mechanically rotated, but can be rotated by means of the electronic switch 1011 ( Fig. 10) the second polarization (perpendicular to the first) of the antenna can be used for measurement.

[0113] The resulting measurement data is then converted from the frequency domain to the time domain using the inverse Fast Fourier Transform (iFFT). This conversion is initiated by the central control device 35 (block 1204).

[0114] The software 74, 75 automatically accesses the stored distance r between the antenna 31 under test and the reference antenna 32 and calculates the width of the time-domain filter 36 (block 1205). The filter width is selected to account for the effects of multipath propagation caused by unwanted reflections from surrounding objects. This eliminates the need for a shielded booth during the measurement, significantly simplifying the setup.

[0115] Filter 36 is then applied to the obtained time domain measurement (block 1206) to filter out the interfering multipath reflections.

[0116] The signal is then converted back into the frequency domain using Fast Fourier Transform (FFT) (Block 1207). The resulting value is the transmitted and reflected power, filtered for unwanted signal interference (multipath propagation / reflection), as a function of the solid angle, i.e., the position in space.

[0117] The operating software calculates the antenna gain G based on this. T (ϑ, φ) using equation (1), depending on the solid angle and taking into account reflection and polarization losses (Block 1208). GT(ϑ,φ)=10log10(Pe_TPg_R)−20log10(λ4πr)−GREF(ϑ,φ)−(10log(1−(Pe_TPe_R)|Pg_R=0)+10log(1−(Pg_TPg_R)|Pe_R=0)+20log|p^R⋅p^T|)

[0118] Both effects, i.e. reflection and polarization losses, will be explained below with reference to equation (1).

[0119] Reflections occur at the transition between the respective cable and the respective antenna because there is a discontinuity between the characteristic impedance of the cable and the antenna. This effect is represented in the equation (1) above by the two terms 10 log(Pe_TPe_R)|PgR=0 (antenna to be tested) and 10 log(Pg_TPg_R)|PerR=0 (Reference antenna) taken into account. P g_R denotes the power of a signal flowing into the reference antenna 32 (see also Fig. 6), P g_T denotes the power of a signal emanating from the reference antenna 32, P e_R denotes the power of a signal flowing into the antenna 31 under test, and P e_T denotes the power of a signal emanating from the antenna 31 under test.

[0120] Polarization losses arise because there is an angle between the unit vector and the electric field vector of the antenna under test (p̂).T ) and that of the reference antenna (p̂ R ). Polarization losses are typically determined by measuring both polarizations of a linearly polarized horn antenna. This requires mechanically rotating the antenna by 90° each time. By using a dual-polarized antenna, an RF switch 1011 ( Fig. 10) Both polarizations are detected significantly faster.

[0121] Equation (1) thus describes the complete formula for calculating the gain of an antenna 31 under test according to the invention, which the operating software can perform and save in the background. The resulting overall result is the spatial radiation (gain) of the antenna 31 under test, taking into account and extracting unwanted multipath signal interference, using an intuitive software interface and an automatically controlled antenna test setup.

[0122] This results in significant advantages over the state of the art: • No umbrella cabin is needed, • automated measurement process, • No highly qualified personnel are required for operation • higher measurement accuracy, • Low investment costs for the antenna test site

[0123] In Fig. Section 13 describes a more detailed measurement procedure, as performed with a [unclear text] Fig. The antenna measurement station 30 shown in Figure 8 can be used. The dashed box 1301 contains several blocks that can be executed once before a test run.

[0124] In a first step, the devices are initialized and moved to the zero position. For this purpose, the rotatable table 78 is moved to a zero position, so that the antenna 31 to be tested, which is arranged on it, is in a zero position with respect to its rotation φ in its horizontal plane.

[0125] The reference antenna 32 is also moved along the receiving device 80 to its zero position with respect to its inclination ϑ relative to the antenna 31 under test. This zero position can be either parallel to the horizontal plane of the antenna 31 under test, or perpendicular to it.

[0126] The devices are then calibrated using the calibration module 79. Before or after this, the spatial distance r and the relative orientation of the two antennas 31, 32 to each other are measured using a laser measuring device.

[0127] The test run to determine the antenna characteristics of the antenna under test can then be performed. In block 1310, the antenna 31 under test is first brought into a specific position (first azimuth measurement position) with respect to its rotation φ. This is done by rotating the rotatable table 78.

[0128] In block 1311, the reference antenna 32 is brought into a specific position (first elevation measurement position) relative to the antenna 31 to be tested. This is done by moving the reference antenna 32 along the receiving device 80.

[0129] Steps 1310 and 1311 can also be performed in reverse order.

[0130] In block 1312, the antenna 31 to be tested is contacted. This can be done, for example, using a probe.

[0131] In block 1313, the RF switch 1011 of the receiver module 39, coupled to the antenna 31 under test, is activated to switch from the calibration position to the receive position, so that the receiver module 39 can receive the signal transmitted by the reference antenna 32 via the antenna 31 under test. The RF switch 1011 in the transmitter module 38, coupled to the reference antenna 32, switches to a first polarization of the reference antenna 32.

[0132] In block 1314, the received signal is measured in the frequency domain. In block 1315, this signal is transformed into the time domain using an inverse FFT, and the time gating described above is applied to the signal. Finally, it is transformed back into the frequency domain using an FFT.

[0133] In block 1316, the measurement results of the filtered signal are read out, and the antenna gain can be determined using equation (1) as a function of the currently set solid angle. The results can be stored on the control device and displayed to the operator using a suitable display device.

[0134] In block 1317, the RF switch 1011 of the transmitter module 38 coupled to the reference antenna 32 is then switched to a second polarization, which is offset by 90° to the first polarization.

[0135] In block 1318, the signal is measured again, analogous to block 1314. In block 1319, time gating is then applied to the signal, analogous to block 1315.

[0136] In block 1320, analogous to block 1316, the measured values ​​of the filtered signal are read out and stored, and the antenna gain can be determined using equation (1) as a function of the currently set solid angle.

[0137] In query block 1322, a decision is made as to whether the measurement is complete or whether further measurements should be performed. If the measurement is not yet complete, the system returns to block 1310 via transition 1323. Here, a new position of the antenna 31 under test is moved relative to the reference antenna 32, and another measurement is performed. This loop can be repeated as often as necessary until a complete sphere around the antenna 31 under test has been traversed and measured, preferably in both polarizations of the reference antenna 32.

[0138] Once this loop is complete, the process moves from query block 1322 to block 1325 via transition 1324. Here, the measurement results are evaluated and displayed graphically to the operator if required.

[0139] Fig. Figure 14 summarizes a block diagram showing some elements of the device according to the invention. The blocks are labelled with individual steps relating to the method according to the invention.

[0140] In block 1401, a microcontroller controls the hardware surrounding the antenna measuring station 30. For example, block 1401 controls the rotating table 78, the recording device 80, the probe for antenna contacting, and the laser measuring device. Sensors can provide corresponding feedback.

[0141] In block 1402, the transmit and receive modules are controlled in order to send or receive signals (e.g. a test signal) using the respective coupled antenna 31, 32.

[0142] The central control device 35 coordinates and controls the processes and evaluates the measurement results.

[0143] Although some aspects have been described in connection with a device, it is understood that these aspects also constitute a description of the corresponding process, such that a block or component of a device can also be understood as a corresponding process step or as a feature of a process step. Similarly, aspects described in connection with or as a process step also constitute a description of a corresponding block, detail, or feature of a corresponding device. Some or all of the process steps can be performed by (or using) a hardware apparatus, such as a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, some or more of the key process steps can be performed by such an apparatus.

[0144] Depending on specific implementation requirements, embodiments of the invention can be implemented in hardware or in software. The implementation can be carried out using a digital storage medium, for example, a floppy disk, DVD, Blu-ray disc, CD, ROM, PROM, EPROM, EEPROM, FLASH memory, hard disk, or other magnetic or optical storage medium, on which electronically readable control signals are stored. These control signals can interact with, or interact with, a programmable computer system in such a way as to execute the respective method. Therefore, the digital storage medium can be computer-readable.

[0145] Some embodiments according to the invention therefore comprise a data carrier which has electronically readable control signals which are able to interact with a programmable computer system in such a way that one of the methods described herein is carried out.

[0146] In general, embodiments of the present invention can be implemented as a computer program product with a program code, wherein the program code is effective in carrying out one of the methods when the computer program product runs on a computer.

[0147] The program code can also be stored on a machine-readable medium, for example.

[0148] Other embodiments include a computer program for carrying out one of the methods described herein, wherein the computer program is stored on a machine-readable medium. In other words, an embodiment of the method according to the invention is thus a computer program that includes program code for carrying out one of the methods described herein when the computer program is executed on a computer.

[0149] Another embodiment of the methods according to the invention is therefore a data carrier (or a digital storage medium or a computer-readable medium) on which the computer program for carrying out one of the methods described herein is recorded.

[0150] Another embodiment of the method according to the invention is thus a data stream or a sequence of signals that represents the computer program for carrying out one of the methods described herein. The data stream or sequence of signals can be configured, for example, to be transferred via a data communication connection, such as the Internet.

[0151] Another embodiment comprises a processing device, for example a computer or a programmable logic device, which is configured or adapted to perform one of the methods described herein.

[0152] Another embodiment comprises a computer on which the computer program for performing one of the procedures described herein is installed.

[0153] Another embodiment of the invention comprises a device or system designed to transmit a computer program for carrying out at least one of the methods described herein to a receiver. The transmission can be, for example, electronic or optical. The receiver can be, for example, a computer, a mobile device, a storage device, or a similar device. The device or system can, for example, include a file server for transmitting the computer program to the receiver.

[0154] In some embodiments, a programmable logic device (for example, a field-programmable gate array, an FPGA) can be used to perform some or all of the functionalities of the methods described herein. In some embodiments, a field-programmable gate array can interact with a microprocessor to perform one of the methods described herein. Generally, in some embodiments, the methods are performed by any hardware device. This can be general-purpose hardware such as a computer processor (CPU) or method-specific hardware such as an ASIC.

[0155] The embodiments described above merely illustrate the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be obvious to other people skilled in the art. Therefore, it is intended that the invention be limited only by the scope of protection set forth in the following claims and not by the specific details presented herein by way of description and explanation of the embodiments. Sources [1] S. Ranvier, M. Kyro, C. Icheln and C. Luxey, “COMPACT 3-D ON-WAFER RADI-ATION,” in MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, 2008 [2] J. Akkermans, R. v. Dijk and M. Herben, “Millimeter-wave antenna measurement,” in Proceedings of the 37th European Microwave Conference, Munich, 2007 [3] H. Gulan, S. Beer, S. Diebold, C. Rusch, A. Leuther, I. Kallfass und T. Zwick, „Probe based antenna measurements up to 325 GHz for upcoming millimeter-wave applications“, in International Workshop on in Antenna Technology (iWAT), 2013. [4] T. Zwick, C. Baks, U. R. Pfeiffer, D. Liu und B. P. Gaucher, „Probe Based MMW Antenna Measurement Setup“, in IEEE Antennas and Propagation Society International Symposium, 2004. [5] S. Beer, G. Adamiuk und T. Zwick, „Design and Probe Based Measurement of 77 GHz“, in Proceedings of the 39th European Microwave Conference, Roma, 2009. [6] „A-Info,“ [Online]. Available: http: / / www.ainfoinc.com / en / p_ant_h_dual.asp. [Zugriff am 08. Oktober 2015]. [7] http: / / www.ets-lindgren.com / pdf / 3115-PA.pdf, „ETS-Lindgren,“ [Online]. Available: http: / / www.ets-lindgren.com / pdf / 3115-PA.pdf. [Zugriff am 08 Oktober 2015]. [8] „exelisinc,“ [Online]. Available: http: / / www.exelisinc.com / capabilities / Antennas / Documents / AS-48461_Series.pdf. [Zugriff am 08 Oktober 2015]. [9] J. Edwards, R. O'Brient, A. Lee und G. Rebeiz, „Dual-Polarized Sinuous Antennas on Extended Hemispherical Silicon Lenses,“ in IEEE Transactions on in Antennas and Propagation, 2012.

[10] G. Adamiuk, T. Zwick und W. Wiesbeck, „Compact, Dual-Polarized UWB-Antenna, Embedded,“ in IEEE Transactions on Antennas and Propagation , 2010.

[11] Roger B. Marks: „A Multiline Method of Network Analyzer Calibration“, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 39, NO. 7, JULY 1991

[12] R. V. De Jough, M. Hajian and L. P. Ligthart, „Antenna time-domain measurement techniques,“ in IEEE Antennas and Propagation Magazine, vol. 39, no. 5, pp. 7-11, Oct 1997.

Claims

[1] Method for determining the antenna gain of an antenna (21) to be tested in free space, wherein the method comprises the following steps: Acquisition of measurement results of a transmitted power of a measurement signal (24a, 24b) transmitted between a reference antenna (22) and an antenna to be tested (21); Determining an input reflection factor (Pe_TPe_R)|Pg_R=0 the antenna (21) to be tested and an input reflection factor (Pg_TPg_R)|Pe_R=0 the reference antenna (22); Detecting polarization losses based on an angle between the unit vector of the electric field vector (p̂) T ) the antenna (21) to be tested and the electric field vector (p̂ R ) the reference antenna (22); where the detection takes place in the frequency domain; Converting the recorded measurement results into the time domain; Applying a time domain filter (26) to the measurement results converted into the time domain, wherein a filter width of the time domain filter (26) is determined as a function of a spatial distance (r) between the reference antenna (22) and the antenna (21) to be tested, so that measurement result components (24b) resulting from multipath propagation of the measurement signal (24a, 24b) between the reference antenna (22) and the antenna (21) to be tested are reduced or removed; Converting the filtered measurement results into the frequency domain; and Determining the antenna gain G T (ϑ, φ) of the antenna (21) to be tested, taking into account the recorded input reflection factors and polarization losses, based on the filtered measurement results available in the frequency domain using the following equation: GT(ϑ,φ)=10 log10(Pe_TPg_R)−20 log10(λ4πr)−GREF(ϑ,φ)−(10 log(1−(Pe_TPg_R)|Pg_R=0)+10 log(1−(Pg_TPg_R)|Pe_R=0)+20 log|p^R⋅p^T|) [2] Method according to claim 1, wherein, when acquiring the measurement results, the reference antenna (22) is moved to different measurement positions relative to the antenna (21) to be tested, and in the different measurement positions, the power of a measurement signal (24a) transmitted via a free space path is acquired at a specific wavelength λ and the spatial distance (r) between the reference antenna (22) and the antenna (21) to be tested in the frequency domain for different solid angles (ϑ, φ) with elevation angle ϑ and azimuth angle φ. [3] A method according to any of the preceding claims, comprising the following steps: Capturing the measurement signal power P flowing into the reference antenna (22) g_R and the measurement signal power P emanating from the antenna (21) to be tested e_Tfor different solid angles (ϑ,φ), and Determining the antenna gain G T (ϑ, φ) of the antenna (21) to be tested, taking into account the measured signal powers. [4] Method according to one of the preceding claims, wherein when detecting the polarization losses the polarization of the reference antenna (22) is rotated by 90° relative to the polarization of the antenna (21) to be tested. [5] Method according to one of the preceding claims, wherein the spatial distance (r) and / or the orientation between the antenna (21) to be tested and the reference antenna (22) is detected by means of laser radiation. [6] Device (20) for determining the antenna gain of an antenna (21) to be tested in free space, wherein the device (20) comprises: Means (23) for recording measurement results of a transmitted power of a measurement signal (24a, 24b) transmitted between a reference antenna (22) and an antenna (21) to be tested, wherein the recording takes place in the frequency domain; a control device (25) configured to convert the measurement results into the time domain; and a time domain filter (26), wherein the control device (25) is configured to apply the time domain filter (26) to the measurement results converted into the time domain, wherein a filter width of the time domain filter (26) is determined as a function of a spatial distance (r) between the reference antenna (22) and the antenna (21) to be tested, so that measurement result components (24b) resulting from multipath propagation of the measurement signal (24a, 24b) between the reference antenna (22) and the antenna (21) to be tested are reduced or removed; wherein the control device (25) is further configured to convert the filtered measurement results into the frequency domain; wherein the means (23) are designed to record measurement results in order to an input reflection factor (Pe_TPe_R)|Pg_R=0 the antenna to be tested (21) and an input reflection factor (Pg_TPg_R)|Pe_R=0 to determine the reference antenna (22); wherein the means (23) for acquiring measurement results are further configured to calculate polarization losses based on an angle between the unit vector and the electric field vector (p̂ T ) the antenna (21) to be tested and the electric field vector (p̂ R ) to detect the reference antenna (22); and wherein the control device (25) is further configured to control the antenna gain G T(ϑ,φ) of the antenna (21) to be tested, taking into account the recorded input reflection factors and polarization losses, based on the filtered measurement results available in the frequency domain, using the following equation: GT(ϑ,φ)=10 log10(Pe_TPg_R)−20 log10(λ4πr)−GREF(ϑ,φ)−(10 log(1−(Pe_TPe_R)|Pg_R=0)+10 log(1−(Pg_TPg_R)|Pe_R=0)+20 log|p^R⋅p^T|) [7] Device (20) according to claim 6, wherein the device (20) has a means (80) for moving the reference antenna (22) relative to the antenna (21) to be tested into different measurement positions, and wherein a control device (25) is configured to detect in the different measurement positions the power of a measurement signal transmitted via a free-space path at a frequency f and the spatial distance (r) between the reference antenna (22) and the antenna (21) to be tested in the frequency domain for different solid angles (ϑ, φ) with elevation angle ϑ and azimuth angle φ. [8] Device (20) according to one of claims 6 or 7, wherein the means (23) for acquiring measurement results are configured to measure the measurement signal power P flowing into the reference antenna (22). g_R and the measurement signal power P emanating from the antenna (21) to be tested e_Tto detect for different solid angles (ϑ, φ), and wherein the control device (25) is designed to control the antenna gain G T (ϑ, φ) of the antenna (21) to be tested, taking into account the measured signal powers. [9] Device (20) according to one of claims 6 to 8, wherein the means (23) for acquiring measurement results further comprise a transmitter module (38) with a transmitter stage comprising a mixer (95), an amplifier (96) and a switching matrix (97) in the direction of the signal. [10] Device (20) according to one of claims 6 to 9, wherein the means (23) for acquiring measurement results comprise a receiving stage (39) which includes a receiving antenna (91), a switching matrix (92), an amplifier (93) and a mixer (94) in the direction of the signal. [11] Device (20) according to claim 9 or 10, wherein the control device (25) is configured to control the transmitting stage and / or the receiving stage such that the polarization of the transmitting stage is rotated by 90° relative to the receiving stage, wherein the rotation is carried out by controlling the switching matrix of the transmitting stage and / or the receiving stage. [12] Device (20) according to one of claims 6 to 11, wherein the device (20) has an automated sequence control (30b) for the automated execution of a measurement sequence. [13] Antenna test site (30) for determining the antenna gain of an antenna (21) to be tested in free space, wherein the antenna test site (30) comprises: an antenna measuring device (33) with a transmitting module (38) and a receiving module (39), an antenna (31) to be tested and a reference antenna (32), wherein the transmitting module (38) is coupled to at least one of the two antennas (31, 32) and the receiving module (39) is coupled to at least the other of the two antennas (31, 32), a time domain filter (36), wherein a filter width of the time domain filter (36) is determined as a function of a spatial distance (r) between the antenna (31) to be tested and the reference antenna (32), and a control device (35) configured to control the transmitting module (38) and the receiving module (39) such that the transmitting module (38) sends out a test signal (34a, 34b) by means of one of the two antennas (31, 32) and the receiving module (39) receives the test signal (34a, 34b) by means of the other of the two antennas (31, 32), and the control device (35) is further configured to convert the test signal (34a, 34b) received in the frequency domain into the time domain and to apply the time domain filter (36) to the received test signal (34a, 34b) in order to filter out test signal components (34b) lying outside the filter width, and wherein the control device (35) is configured to convert the filtered test signal present in the time domain back into the frequency domain, wherein the control device (35) is further configured to provide an input reflection factor (Pe_TPe_R)|Pg_R=0 the antenna to be tested (21) and an input reflection factor (Pg_TPg_R)|Pe_R=0 to detect the reference antenna (22), and to account for polarization losses based on an angle between the unit vector of the electric field vector (p̂ T ) the antenna (21) to be tested and the electric field vector (p̂ R) to detect the reference antenna (22); and wherein the control device (35) is further configured to determine the antenna gain G from the test signal converted back into the frequency domain T (ϑ, φ) of the antenna (31) to be tested, taking into account the recorded input reflection factors and the polarization losses, as a function of a certain solid angle (φ, ϑ) using the following equation: GT(ϑ,φ)=10 log10(Pe_TPg_R)−20 log10(λ4πr)−GREF(ϑ,φ)−(10 log(1−(Pe_TPe_R)|Pg_R=0)+10 log(1−(Pg_TPg_R)|Pe_R=0)+20 log|p^R⋅p^T|) [14] Antenna test setup (30) according to claim 13, wherein the reference antenna (32) and the antenna (31) to be tested are configured to transmit and / or receive radiation in a frequency range between 1 GHz and 10 THz, and in particular between 50 GHz and 1.1 THz, or between 50 GHz and 100 GHz. [15] Antenna measuring station (30) according to claim 13 or 14, wherein the control device (35) is configured to determine the spatial distance (r) between the reference antenna (32) and the antenna (31) to be tested and / or the orientation of the reference antenna (32) relative to the antenna (31) to be tested. [16] Antenna measuring station (30) according to claim 15, wherein the antenna measuring station (30) comprises a laser measuring device configured to determine the spatial distance (r) and / or an angle of the reference antenna (32) relative to the antenna (31) to be tested. [17] Antenna test setup (30) according to one of claims 13 to 16, wherein the receiver module (39) has a receiver stage comprising a switching matrix (92), an amplifier (93) and a mixer (94) in the direction of propagation of the test signal. [18] Antenna test setup (30) according to one of claims 13 to 17, wherein the transmitter module (38) has a transmitter stage comprising a mixer (95), an amplifier (96) and a switching matrix (97; 1011) in the direction of signal propagation of the test signal. [19] Antenna measuring station (30) according to one of claims 17 or 18, wherein the reference antenna (32) is a dual polarized antenna, and the control device (35) is configured to rotate the polarization of the reference antenna (32) by 90° using the switching matrix (97; 1011). [20] Antenna test setup (30) according to one of claims 13 to 19, wherein the antenna test setup (30) has a rotatable table (78) on which the antenna (31) to be tested can be arranged, and wherein the control device (35) is designed to rotate the table (78) so that when the table (78) is rotated, the antenna (31) to be tested rotates together with the table (78) in a first plane to change an azimuth angle φ between the reference antenna (32) and the antenna (31) to be tested. [21] Antenna measuring station (30) according to one of claims 13 to 20, wherein the antenna measuring station (30) has a receiving device (80) for movably receiving the reference antenna (32), and wherein the control device (35) is configured to move the reference antenna (32) along the receiving device (80) relative to the antenna (31) to be tested in a second plane perpendicular to the first plane in order to change an elevation angle ϑ between the reference antenna (32) and the antenna (31) to be tested. [22] Antenna test setup (30) according to one of claims 13 to 21, wherein the antenna test setup (30) comprises a test signal generator configured to generate the test signal and transmit it to the transmitter module (38), wherein the transmitter module (38) comprises a first integrated transmitter stage (1001) and a second integrated transmitter stage (1002), wherein the first transmitter stage (1001) comprises a frequency mixer (1005) for upmixing the test signal into a first frequency band and the second transmitter stage (1002) comprises a frequency mixer (1006) for upmixing the test signal into a second frequency band, and wherein the transmitter module (38) comprises a switch (1004) for selectively selecting the respective transmitter stage (1001, 1002). [23] Antenna measuring station (30) according to one of claims 13 to 22, wherein the antenna measuring station (30) has an automated sequence control (30b) for the automated execution of a measurement sequence. [24] Computer program comprising program code for carrying out the method according to any one of claims 1 to 5.

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