EP1476764A1

EP1476764A1 - Method and system for sampling at least one antenna

Info

Publication number: EP1476764A1
Application number: EP03742513A
Authority: EP
Inventors: Jürgen Deininger; Bernd Gottschalk; Stefan Lindenmeier; Günter Reichert
Original assignee: DaimlerChrysler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2002-02-22
Filing date: 2003-02-11
Publication date: 2004-11-17
Also published as: WO2003071293A1; DE10305741A1; JP2005518172A; US20060082494A1

Abstract

The invention relates to a method for sampling at least one antenna (2) comprising a receiver module (8) and a coupling module (10) that is arranged between the antenna (2) and the receiver module (8). A noise signal (S) is fed to the antenna (2) and the receiver module (8) as a sampling signal via the coupling module (10). An instantaneous transmission coefficient (UV) indicating the relationship between a first noise signal, which reaches a sampling module (12) via a first path (S, S1) without transiting through the at least one antenna (2), and a second noise signal, which reaches said sampling module (12) from the noise source (18) via a second path (S', S2) transiting through the at least one antenna (2), is then determined via the sampling module (12) and is compared with a reference transmission coefficient (Uvinorm) stored in a transmission matrix (14). Also disclosed is a system for carrying out the inventive method.

Description

Method and arrangement for testing at least one antenna

The invention relates to a method and an arrangement for testing at least one antenna, in particular a multi-antenna system of a vehicle.

With an increasing number of antennas in the vehicle, there is a need to carry out a functional test of the antenna system. Such functional tests are usually carried out in the disassembled state. A functional test in the installed state of the antenna has so far been particularly complex and complex. For example, from DE 196 18 333 AI a circuit arrangement for the functional test of mobile radio reception systems is described in the installed state. The disadvantage here is that, in order to generate a test signal, this comprises a calibrated signal generator which emits a discrete test signal exclusively at the frequency on which the receiver is tuned. In addition, the circuit arrangement described there is not suitable for diagnosis taking external influences such as snow or ice into account.

Furthermore, a system for testing a signal transceiver, such as a receiving antenna, is known from US Pat. No. 6,005,891. Here, a pseudo-noise signal source is used as the test signal source. In the system, processing of a signal reflected on a damaged receiving antenna and a comparison with the original test signal is carried out by means of a complex circuit. leads. Among other things, a correlation receiver is required for this. However, this system is very expensive to implement due to the use of the pseudo-noise signal source, which generates a fast digital signal, and the correlation receiver. In addition, it is always necessary to know the level of the output signal of the pseudo-noise signal source.

The invention is therefore based on the object of specifying a method for testing at least one antenna of a vehicle, in which a diagnosis is carried out on all frequencies of a band, e.g. Radio, TV, mobile radio, ISM band, inexpensively and in a particularly simple manner. Furthermore, a particularly simple arrangement for testing the antenna when installed is to be specified. In addition, it should also no longer be necessary to know the level of the test signal source, which makes it possible to use an inexpensive test signal source.

The object is achieved according to the invention by the features of claim 1 and claim 6. The subclaims comprise advantageous design details and variants.

The advantages achieved by the invention are, in particular, that a noise signal from an uncalibrated noise source is coupled onto the antenna as a test or test signal by means of a controllable coupling module. In the case of only a single antenna, the noise signal reflected at the antenna input is evaluated as a received signal in a test module. For this purpose, a current transmission coefficient representing the relevant antenna is advantageously determined on the basis of the received signal at a predetermined frequency or at several frequencies of a band and compared with a reference transmission coefficient which represents the transmission behavior from the noise source via the coupling module to the antenna and back to the receiver. advantage. With a working antenna, the reflection from the antenna is minimal.

In the case of a multi-antenna system comprising several antennas, the noise signal transmitted between the antennas is analyzed and evaluated as an alternative or in addition to the noise signal reflected at the respective antenna inputs. For this purpose, the noise signal is coupled into the antenna (s) from the uncalibrated noise source or test signal source by means of a coupling circuit and received by an adjacent antenna and in the test module, in particular in the receiver, e.g. Audio or video tuner, analyzed using a transmission matrix. Such function monitoring or diagnosis using a simple, uncalibrated noise source, which in the simplest case is formed by a source of the receiver itself, enables a particularly inexpensive and simple arrangement. In particular, the manufacturing effort is particularly low. Due to the use of already existing components of the receiver, the arrangement requires little space and as a result, due to the integration of the test module e.g. into a vehicle, the use of the diagnostic or test procedure in the vehicle area can eliminate the need for complex test transmitters in production at the end of the line or in service.

In addition, due to the use of a noise signal as a test signal, diagnosis of the antenna (s) covering all frequency bands is possible. In particular, such a test based on a noise signal also makes it possible to evaluate external influences on the functionality of the antenna (s), such as snow or other external interference signals, which lead to misdiagnosis in the conventional systems according to the prior art. In particular, it is ensured that the antenna (s) can also be status and thus checked and monitored, for example, while a vehicle is in motion.

Preferred exemplary embodiments of the invention are explained in more detail below in conjunction with the drawing. In it show:

1 schematically shows a circuit arrangement for checking the functionality of a multi-antenna system,

2 schematically shows the signal curve of a test signal in the multi-antenna system,

3 to 5 schematically alternative embodiments of the

1 with switchable transmission branches for an AM band and an FM band or FM band with diversity,

6 schematically shows a flowchart of the test algorithm, and

7 to 14 schematically show different circuit arrangements for checking the functionality of an individual antenna.

Corresponding parts are provided with the same reference symbols in all figures.

FIG. 1 shows a circuit arrangement 1 for testing an antenna system 4, comprising several antennas 2, of a vehicle (not shown in more detail). The antenna system 4 is in particular integrated into a window 6, eg rear window, side window, or rear window and / or side window (s) of the vehicle. The circuit arrangement 1 comprises a receiver module 8 and a coupling module 10 arranged between the antennas 2 and the receiver module 8. The antenna or coupling module 10 serves to couple a noise signal S. into the respective antenna 2 and into the receiver module 8, also called a tuner. The receiver module 8 further comprises a test module 12 for determining an instantaneous transmission coefficient U _v i on the basis of a relationship between the noise signal component S 'coupled via the antennas and the noise signal component Si transmitted directly from the noise source to the receiver. To determine the functionality of the respective antenna 2, the test module 12 comprises a transmission matrix 14 in which a reference transmission coefficient U _v i _norm (also called U _vn - _m ) describing the transmission behavior and / or the transmission path is stored for the respective antenna 2. On the basis of a comparison of the current transmission coefficient Ü _v i with the reference transmission coefficient Ü _v i _norm , the operability of the antenna 2 is inferred. The coupling module 10, also called an antenna module, comprises an uncalibrated noise source 18 and a controllable RF switch 20 as the diagnostic circuit 16. The noise source 18 covers all frequency bands which can be detected in the receiver module 8.

In an advantageous embodiment, the noise source 18 can be implemented in the form of a bipolar transistor in an amplifier circuit. A calibrated noise source is not required in the diagnostic or test procedure proposed here. This means that a complex determination of the current frequency response of the component and temperature-dependent noise source 18 can be omitted. The controllable RF switch 20 is designed, for example, in the form of switchover diodes. The number of switching diodes corresponds to the number of antennas 2, which are used in the diagnostic mode as transmitting antennas 2 (n). The number of transmit antennas 2 (n) used determines the evaluation reliability of the diagnosis. The diagnostic circuit does not require any complex manufacturing costs, but can be accommodated on its circuit board surface, for example, by changing the layout of the antenna amplifier module. The data evaluation in the tuner or receiver 8 can be implemented by expanding the software, additional hardware is not required. Depending on the type and design of the circuit arrangement 1, the receiver module 8 and the coupling module 10 can be formed by a common module. In addition, depending on the function, the individual modules can be implemented in software and / or hardware. The arrangement and combination of the individual modules can also vary depending on the specifications.

The switchover diodes are controlled with the aid of a digital counter 21. A control signal DI transmits two voltage states from the receiver module 8 to the digital counter 21 at a low bit rate. The control signal DI can be transmitted along an already existing RF cable in the same way as is already carried out when a given FM diversity circuit is activated. With each positive edge of the control signal DI, the counter 21 switches one position so that all antenna branches A, B, ..., Z are switched through in succession. After the last antenna branch Z has been switched through and the diagnosis has been made, the next positive edge causes the noise source 18 to be switched off or, alternatively, the state that no antenna branch A to Z is switched through. On the subsequent positive edge, the first antenna branch A is switched through again in a new diagnostic cycle.

At least two rear window antennas 2 are successively coupled as transmission antennas 2 (n) via the HF switch 20. In an antenna system 4 with at least two antennas 2, the functionality of the antennas 2 is preferably measured by measuring the near-field transmission between the antennas 2 sen. The reference transmission coefficients Ü _V i _norm or factors for all possible couplings between the antennas 2 form the transmission matrix 14. The current transmission coefficients Üvi are determined analogously to this using the transmission matrix 14 and compared with the reference transmission coefficients Ü _v i _norm . The antennas 2 are used both as transmitting and receiving antennas.

The transmission path is determined by sending out the noise signal S via one of the antennas 2 as the transmitting antenna n and by receiving the resulting reception signal S 'at one of the other antennas 2 as the receiving antenna m or by reflection of the noise signal S at the antenna input of the relevant transmitting antenna n.

The evaluation using the transmission matrix 14 also expediently permits the detection of impairments, such as, for example, wetness, snow, and external interference signals which can affect several antennas 2. The test or diagnosis is carried out in such a way that the transmission of the noise signal S from the respectively selected transmitting antenna 2 (n) to the other adjacent rear window antennas 2 forming the receiving antennas 2 (m) is checked in the receiver module 8, in particular for all frequency bands. Each antenna 2 is thus checked for its transmission behavior U _v for several frequency bands. The FM band, the highest TV band and the AM band are expediently analyzed, as a result of which the function of the antennas 2 is checked and determined safely and easily on the basis of the transmission behavior U _v . Since the transmission is also checked in different combinations of transmitting antennas and receiving antennas, external sources of error can be excluded. In the operation of the circuit arrangement 1, the RF switch 20 does not leave any noise signal S on the antenna path 22 during normal antenna operation with the position 0. In the diagnostic or test mode, the RF switch 20 is successively in the positions 1 and 2, the noise signal S is successively coupled onto the antenna paths 22 via coupling circuits 24, for example via T crossings or capacitively. There, the noise signal S splits into the noise signal Si, which is led directly from the noise source 18 to the tuner 8, and the noise signal S _{2, which} migrates to the antenna 2 in question and is radiated on the antenna ₂ . By comparing the received signal S ₂ received by the receiving antenna 2 (m) with the noise signal Si, which is directed directly to the level evaluation, statements can be made about the functionality of the antennas 2 concerned. In addition, depending on the degree of analysis, the Transmission and amplifier circuits 26 and their influence on the transmission are taken into account. Since all or more antennas 2 are used as transmitting antennas n and all antennas 2 are used as receiving antennas m, the overall system can be represented by a transmission matrix 14 of maximum nx m.

The determination of the transmission matrix 14 for a level evaluation and the measurement tolerance to be expected are shown below with reference to FIG. 2. For example, given a multi-antenna system 4 with three antennas 2. However, the principle also applies to other systems 4 which comprise at least two antennas 2.

In the level evaluation by means of the transmission matrix 14, in the case of using several antennas i (i = 1, 2, 3) as transmission antennas at the gates I, II and III of the level evaluation, the signal levels Sn, S _i2 and Sι _{3 are} detected in each case. animals. In the case of a largely fully functional, ie optimally adapted, antenna system 4, there is minimal Reflection at the antenna inputs 2. The noise signal S with the level P _r (f) is coupled successively onto the signal paths 22 of the antennas 2. Part of the noise power is emitted via the antenna 2 connected in each case, while another part is conducted directly to the receiver module 8 via the respective filter amplifier circuit 26 of the path 22. The level P _r (f) of the noise source 18 does not have to be known before the measurement, since this can be determined from the measurement evaluation by means of the test module 12 in the receiver module 8. The measurement results in the diagnostic process are therefore independent of the tolerance of the noise source 18.

The assumed transmission coefficient or reference transmission _coefficient Ü _v i _nθrm (f) / the filter amplifier circuit 26 with the lowest tolerance δ _v i and the actual transmission coefficient according to are used as the basis for determining the currently applied noise power P _r

Ü _V i (f) with Ü _V i (f) = Ü _vinorm (f) x (l + δ _vl (f)) [1]

From the signal level S _n detected in the level evaluation for the first antenna 2 at the gate I in accordance with

Sn (f) = (P _r (f) / 2) X Ü _vl (f) = (P _r (f) / 2) X Üvi _norm (f) (l + δ _vl (f)) [2]

for the determination of the noise level Pr (f) for a given measurement tolerance δ _v :

Pr (f) = 2 Sn (f) / ((Ü _vlnorm (f)) x (l + δ _vl (f))) [3]

The noise properties of the noise source 18 may thus be different and temperature-dependent for each component and need not be known from the start. This enables inexpensive production of simple noise sources 18. After the noise level Pr (f) has been determined, the transmission coefficients Ü _v2 (f) and Ü _v3 (f) of the other filter amplifier circuits 26 can be determined from the signal levels S22 and S33, respectively.

Ü _v2 (f) = 2 S ₂₂ (f) / _Pr (f); Ü _v3 (f) = 2 S ₃₃ (f) / Pr (f) [4]

From these coefficients Ü _v2 (f) and Ü _v3 (f), by comparing them with the reference transmission _coefficients Ü _v2norm (f) and Ü _V 3n _o rm (f) or target values for the respective frequency bands, it is easy to determine the functionality of the respective one Filter amplifier circuit 26 are closed. The tolerance δ _{v of} the noise power P _{r also} results for these coefficients Ü _v2 (f) and Ü _v3 (f). For the transmission _coefficients Ü _ai2 (f) and Ü _a ι ₃ (f) between the antennas 2, the tolerances in the transmission path 28 can be _calibrated out according to:

Ü _a ι ₂ (f) = Sιa (f) / S ₂₂ (f); Ü _al3 (f) = S ₁₃ (f) / S ₃₃ (f) [5]

The display tolerance of the receiver 8 is not included in this consideration, since the evaluation of the antenna system 4 is always related to its sensitivity. That If the sensitivity of the receiver 8 is high, the antenna system 4 may have correspondingly lower transmission properties. By means of the diagnostic system or the circuit arrangement 1, the required quality of the antenna system 4 is thus always evaluated as a function of the available tuner sensitivity, so that overall systems 1 (receiver 8 and antenna system 4) with the same quality are also evaluated equally.

The transmission coefficients Ü _a not only provide information about the functionality of the antennas 2, but also about the extent to which the transmission path 28 between the antennas 2 is disturbing. If, for example, there is a blanket of snow on the antennas 2, all transmission coefficients Ü _v i (f) are equally disturbed and the diagnostic algorithm recognizes that it is not an antenna 2 that is disturbed, but rather all transmission paths 28 are affected. Depending on the size of the instantaneous transmission coefficient U _vi (f) determined, the state of the antennas 2 is inferred, for example the rear window 6 is covered with a foreign body.

FIG. 3 shows an alternative embodiment of the circuit arrangement 1, in which, in order to test the different frequency bands of the receiver module 8, the coupling module 16 by means of the positions 1 and 2 of the HF switch 20 for coupling the noise signal S to the relevant transmission branch 30 or 32 is intended for the FM band or AM band. The circuit arrangement 1 shows a two-antenna system 4 for the AM and FM bands. FIG. 4 shows a further embodiment of the circuit arrangement 1 for a five-antenna system 4 for the AM band and the FM band with 4-fold diversity. For this purpose, the number of positions of the RF switch 20 for testing the FM band with diversity has been expanded by the corresponding number of antennas. The test procedure is carried out as already described above. That is, the noise signal S of the noise source 18 is coupled separately into each antenna 2 by means of the RF switch 20. Using the received signal S 'received by one of the adjacent antennas 2 and the transmitted noise signal S, transmission coefficients U _v i (f) relating to all possible combinations of the antennas 2 are determined and with the reference transmission coefficients Ü _V i _norm (f) of the transmission matrix 14 compared.

The method described above for checking the functionality of the antenna 2 is type-independent. FIG. 5 shows an embodiment for a further diagnostic circuit Five antenna system 4, shown for a so-called high-end version for AM, FM and TV diversity. As shown in FIG. 5, an FZV antenna 36 (FZV = radio central locking) can, for example, also be examined according to the method described above if the associated FZV receiver 38 is connected to the AM / FM tuner 8 via a data line 40 so that information about the received level is transmitted to the AM / FM receiver 8 for evaluation.

Alternatively or additionally, depending on the level of equipment in the vehicle, cell phone and / or GPS antennas can also be tested for their functionality via broadband coupling with TV, AM and FM antennas. It does not matter how and where the individual antennas 2 are integrated in the vehicle.

When operating the circuit arrangement 1 according to one of the figures

1 to 5 the n-number antennas 2 are switched in succession as transmitting antennas. Depending on the number n of transmit antennas

2 results in a corresponding number m of receiving antennas 2 and thus to represent the transmission behavior Ü _v nx m level information, which is preferably represented as a level or transmission matrix 14. A permissible range of values can be established for each transmission coefficient Ü _V i of the transmission matrix 14, which

1. is individually assigned to the coupling of a pair of antennas 2 (n, m) and

2. is dependent on all currently measured transmission coefficients Üvi of the transmission matrix 14.

If a permissible value range is exceeded, one or more defective antennas 2 are / are determined using the transmission matrix 14. The dynamic adaptation of the value ranges to the current reception situation advantageously analyzes and identifies external interference effects that affect several antennas 2, for example iced-up rear window 6, in the diagnosis.

Table 1 below shows an example of a transmission matrix 14 for an antenna system 4 with four antennas 2.

TX / RX Antl Ant2 Ant3 Ant4 Ant m

Antl Pll P12 P13 P14.

Ant2 P21 P22 P23 P24.

Ant3 P31 P32 P33 P34.

Ant4 P41 P42 P43 P44.

A t n • • • • Pnm

Table 1

with Ant n = number of transmit antennas, Ant m = number of receive antennas, TX = transmitter, RX = receiver, Pnm = signal level.

Depending on the type and function of the circuit arrangement 1, the transmission matrix 14 comprises, as information, level and / or frequency values which represent the reference transmission coefficient Ü _V i _norm and / or current transmission coefficient Ü _v i for the antenna combination in question. In the case of a diagnosis, the current transmission coefficients Ü _V i are compared with the reference transmission coefficients Ü _v i _{norm of} the respective antenna combination 2 (n, m). This requires an initialization of the transmission matrix 14, for example before the vehicle is started up, ie at the time of production. For this purpose, reference knowledge is generated, on the basis of which a diagnosis can then take place. A possible method for knowledge generation and evaluation is presented below. A diagnosis takes place in several steps:

I) Generating symptoms

(e.g. based on the information available in the transmission matrix 14)

II) Error detection

III) Error localization

FIG. 6 shows an example of a flow diagram of the diagnostic algorithm, which comprises the following steps:

(1) picking up the matrix elements, e.g. on the basis of measurements, specifications of type-specific values or reading of stored past values;

(2) Calibration by standardizing the matrix elements to the transmission power and transmission losses. The calibration is carried out using the elements in the diagonal of the transmission matrix 14.

(3) Detection of "invalid states" such as, for example, iced-up rear window or strong disturbing electromagnetic field.

(4) Evaluation by comparison with stored errors or through a decision network. As an alternative or in addition, a frequency or amplitude analysis can be used to identify an error in one or more antennas 2 or antenna combinations 2 (n, m).

(5) Filtering: plausibility check, ie the diagnostic procedure is run n times. Depending on the specification, an error message is only issued after successful detection of an error, otherwise a message is omitted or the message "Healing" is output. H. Resetting the error memory when multiple ok status is detected.

The measurement and diagnosis procedure is explained below using an example. The transmission behavior between different rear window antennas 2 in their near field is determined by means of a so-called network analyzer. For the measurements of the transmission behavior, the noise signal S is coupled into the antennas 2 one after the other. To estimate the field behavior on the real vehicle, the vehicle roof, C-pillars and trunk lid with electrically connected sheet steel parts have been reproduced. Measurements were carried out for intact antennas 2 and for defective antennas 2, e.g. for an interruption of the window contacts and / or for an interruption of the antenna wires on the rear window 6. Furthermore, the influence of moisture on the transmission behavior was measured.

The transmit or noise signal S was coupled directly into the antenna 2, the antenna amplifier was unsoldered. The transmission antenna 2 is therefore not adapted. If the transmission antenna 2 is fed in in an adapted manner, the transmission factors improve. The values shown in the following tables are the S21 transmission coefficients in dB measured at 100 MHz (FM). S21-

Transmission coefficients represent the transmission factor or transmission coefficient U _v i between the antennas 2 coupled in each case over the near field. In addition to the normal case of the functioning antennas 2, several types of error cases and their influence on the transmission factors were examined. The fault cases were brought about by interrupting the pane contacts, interrupting the pane antenna wires, influencing the near field of the antennas 2 by water on the pane and metal surfaces located in the near field of the antennas 2. For the normal case without incorrect action of an antenna system 4 comprising six antennas 2, which is integrated in the rear window 6, the transmission matrix shown in Table 2 results for the frequency of f = 100 MHz (FM band):

Table 2

The instantaneous transmission coefficients U _v ι determined by means of the transmission matrix 14 are consistently better than -25dB, the anticipated necessary transmission powers for the near field transmission, measured in the conventional far field transmission-reception case, are very low.

To represent the detection of contact weaknesses of the antennas 2. the disk contacts at the connections to the antennas FM1 and TV3 were deteriorated or interrupted by inserting layers of paper of different thicknesses. As shown in Table 2, the antenna combination FM1 and TV3 normally has a transmission coefficient Ü _v ι of -22.37 dB.

Table 3 shows the influence of the weakness of contact on the transmission behavior through a significant change in the transmission coefficient U _v currently determined by means of the transmission matrix 14.

Table 3

The last fault case, "sheet metal in front of window", simulates an invalid state, such as occurs on the rear window 6 due to conductive material such as ice or water.

Furthermore, an interruption of the antenna wires, for example severing the conductor track of the antenna TV3 or severing both conductor tracks of the antenna TV3 and FM2, was simulated. The test or noise signal S is sent via the antenna FM2 or FM1, depending on the activation of the coupling or RF switch 20. The transmission coefficients U determined by means of the transmission matrix 14 are shown in the following tables 4A to 4C. Table 4A

Table 4B

Table 4C

All errors can be clearly recognized by the decrease or increase in the transfer factors Ü. The method described above thus enables a particularly simple and reliable diagnosis of the functionality of individual antennas 2. Depending on the type of antenna, other transmission properties or operating parameters can be taken into account. For example, the increase in the so-called coupling factor S FM1 -> FM3 in the UHF band (800 MHz) in the event of an error in the FM antenna can be explained by the shortening of the electrically effective antenna length. In contrast, the same error in the FM band leads to a corresponding reduction in the coupling.

When the antennas 2 are checked further, they are checked for changes due to the action of water on the rear window 6 and other objects in the vicinity of the rear window 6 analyzed. As shown in Tables 5A and 5B, water sprinkling at 100 MHz has almost no influence on the transmission behavior. On the other hand, if objects, in particular conductive objects, are arranged close to the rear window 6, these changes are displayed in the diagnosis, since these have a significant influence on the transmission behavior of individual antenna pairs.

Table 5A

An alternative embodiment of the circuit arrangement 1 is shown in FIG. 7. The circuit arrangement 1 is designed for a single antenna system 4. In this case, instead of the evaluation of the transmitted from the transmitting to the receiving antenna 2 noise signal S is at a respective antenna input 42 reflected the individual antenna 2 noise signal S ₂ analyzed by the emitted noise signal S _λ and evaluated. Since if the antenna 2 is damaged, its adaptation is disturbed, 42 reflections arise at its input. In the 0 position, the RF switch 20 does not allow any noise signal S from the noise source 18 onto the antenna path during normal antenna operation 22. In the diagnostic mode, the RF switch 20 is in position 1. The noise signal S is then coupled to the antenna path 22 via a coupling network 24, for example a T-element. There, the noise signal S cleaves in the guided directly from the noise source 18 to the receiver module 8 and the noise signal S _x to the antenna 2 migratory and reflected by the antenna 2, noise signal S _2.

Based on the superimposition of the noise signals S _± and S ₂ of the noise signal Si, which is led directly from the noise source 18 to the receiver 8, with the reflected noise signal S ₂ , a characteristic frequency characteristic curve with dips is produced, from which conclusions about the state of the antenna 2 are determined and evaluated. A prerequisite for this, however, is a calibrated noise source 18, the frequency characteristic of which is known. The functionality of the antennas 2 can only be determined by comparing the frequency characteristic of the superposition of the noise signals Si and S ₂ with the frequency characteristic of the noise signal S ₁ .

In order to be able to replace the calibrated noise source 18 with a less expensive, uncalibrated noise source 18, the static coupling circuit 24 is expanded by a switching function with additional positions 2 and 3 to the switchable coupling circuit 44, as shown in FIG. In switch position 2, the noise signal S is sent directly to the receiver 8 and detected there. Ie the antenna path 22 is open. The frequency characteristic of the current noise signal Si is then known for the level evaluation and is stored. Position 3 is then set by means of switchable coupling circuit 44 and antenna path 22 is thus closed. Now the frequency characteristic of the superposition of the noise signals Si and S _{2 is} detected in the level evaluation using the transmission matrix 14 and with the Frequency characteristic of the stored noise signal Si compared.

As an alternative to the switchable coupling circuit 44 or to the open switch, a superimposition of the noise signal Si with the noise signal S ₂ reflected at a defined impedance Z ₂ can also be measured and analyzed for the reference measurement of the noise signal Si, after which the frequency characteristic of the pure noise signal S is then calculated back , The associated circuit arrangement 1 is shown by way of example in FIG. 9.

The frequency characteristic of the illustrated embodiments in FIGS. 7 to 9 for single-antenna systems 4 is detected and analyzed in a relatively wide frequency band in order to ensure the best possible information about the functionality of the antenna 2, since damage to the antenna 2 occurs in the center frequency range f _m in the superimposed noise signal Sι + S ₂ does not necessarily result in significant level changes.

In order to be able to deduce the functionality of the antenna 2 from the level changes of the reflected signal S ₂ when looking at a narrow frequency band f, a directionally selective coupling circuit 46, for example a directional coupler, is preferably used, as shown in FIG. Only the reflected signal S _{2 is} detected here, which has a substantially lower level than the noise signal Si in the case of the functioning antenna 2. A prerequisite for the level evaluation here is that the noise signal level Si is already known. A calibrated noise source 18 is required for this embodiment.

In order to be able to use an inexpensive, uncalibrated noise source 18, a directionally selective coupling network 48 with a switchable signal flow direction is used, as shown in FIG Figure 11 is shown. For this purpose, a directional coupler with alternatively switchable inputs E1, E2 is provided, for example. In switch position 1, the noise signal S is directed to the antenna 2 via the directional coupler 48, reflected and detected as a signal S ₂ in the level evaluation. In switch position 2, the noise signal S is passed via the directional coupler 48 directly to the level evaluation, where it is detected as a reference signal Si.

In FIGS. 12 to 14, modifications of the arrangement according to FIG. 11 are shown below, in which a diagnosis using an uncalibrated, inexpensive noise source 18 is also possible. In this case, uncalibrated always means that the transmission power of the noise source is not known and does not have to assume reproducible values and thus, for example, a strong temperature drift of the transmission power is permitted. For these embodiments, only the differences in structure and function compared to FIG. 11 are discussed in more detail below.

In the embodiment according to FIG. 12, a directionally selective coupling network 50 with a switchable signal flow direction is used in order to be able to use an inexpensive, uncalibrated noise source. As in the embodiment according to FIG. 11, a directional coupler with alternatively switchable inputs is used in the embodiment according to FIG. 12. In contrast to Fig. 11, however, an input is terminated with a 50Ω resistor. In addition, the embodiment according to FIG. 12, in contrast to the embodiment according to FIG. 11, has a modified filter amplifier circuit 26 'with a switchable amplifier. In addition, a switch 49 is additionally formed, which in connection with the switchable amplifier for switching over the signal path from the noise source 18 via the antenna 2 to the receiver 8 Signal path from the noise source 18 directly to the receiver 8 and vice versa. In switch position 2, the noise signal S from the noise source 18 is passed via the directional coupler 50 directly to the level evaluation, where it is detected as a reference signal Si in order to be able to determine and calibrate the noise level. In the case of direct measurement of the noise signal S, the switchable amplifier 26 'is switched off, ie switch position 4, in order to interrupt the signal path via the antenna 2 to the receiver 8. In addition, an attenuator DG can be inserted in the path for a possible level reduction. In switch positions 3 and 5, the noise signal S is passed to the antenna 2, reflected there and passed via the modified filter circuit 26 * in the antenna module 10 to the receiver 8, in which it is detected in the level evaluation as the signal S ₂ . Thus, in addition to the antenna 2 and the modified filter circuit 26 ^λ are checked for their function. With switch position 0 of the HF switch 20, the noise source 18 is switched off for normal operation.

FIG. 13 shows a modification of the embodiment according to FIG. 12, which can be used if it is not possible to use the modified filter circuit 26 ^v with a switchable amplifier, but only the filter circuit according to FIG. 11. In this case, an additional one Switch 51 formed with switch positions 4 ^X and 5 ^V , by which the switch positions 4 and 5 realized in FIG. 12 in the switchable amplifier of the modified filter circuit 26 ^x are replaced. By using this additional switch, the same function as described in connection with FIG. 12 can be achieved.

Due to the use of this additional switch 51, it is now also possible to dispense with the RF switch 20. The resulting circuit is shown in FIG. 14. In this case, the RF switch 20 is for switching off the noise source 18 is no longer required since the switch-off can now be carried out by a combination of the switch positions 3 and 4.

The advantages achieved by the invention are, in particular, that a noise generator 18 is used as the transmitter, which can be integrated into the antenna module 10. The tuner or transceiver set in a diagnostic mode can serve as the receiver 8. This provides a particularly inexpensive transmitter. Since the receiver 8 is already present, the diagnostic function must be added to the software.

As a further alternative embodiment of the invention, an additional antenna can be formed which, in contrast to the antenna 2, has no connection to the receiver module 8. The noise signal S from the noise generator 18 is now coupled into this additional antenna. The additional antenna then sends this noise signal to the antenna (s) 2. The resulting reception signal S ^x or S ₂ is received and evaluated by the test module 12 in the receiver module 8.

As described above, the present invention discloses the use of a very simple, inexpensive test signal source for antenna diagnosis. This is done in particular by using an economically favorable low-price noise signal source, the performance of which need not be known. Due to its wide signal spectrum, the noise source is suitable for testing antennas in several frequency bands, eg AM, FM, TV. By sequentially using a different antenna as the transmitting antenna, a transmission matrix can be created that represents the near field coupling between different antenna combinations. With the help of this transmission matrix, the signal power of the noise source or test signal source can be extracted. be librated. A simple, inexpensive test signal source can thus be used, the level of which, in contrast to all previous approaches, does not have to be known and not reproducible. The transmission matrix is also used to calculate out external influences that affect all or more antennas, such as common single, snow or leaf coverings as well as external interference signals. In the case of an arrangement for single antenna systems, a directional coupler is used in a calibration circuit. The reception level is measured for several switching positions in the arrangement on the tuner. The performance of the low-price signal source can be determined or calibrated out from various level values. This calibration circuit can of course also be used in the case of several antennas.

In summary, the present invention discloses a method for testing at least one antenna 2 with a receiver module 8 and a coupling module 16 arranged between the antenna 2 and the receiver module 8. In this case, the antenna 2 and the receiver module 8 are supplied with a noise signal S as a test signal by means of the coupling module 16 , Using a test module 12, a current transmission coefficient is then determined by superimposing the noise signal S, Si with a received signal SS ₂ resulting from the noise signal S, Si and compared with a reference transmission coefficient stored in a transmission matrix. Furthermore, an arrangement for carrying out the method according to the invention is also disclosed.

Claims

claims

1. Method for testing at least one antenna (2) with a receiver module (8) and a coupling module (10) arranged between the at least one antenna (2) and the receiver module (8), in which the antenna (2) and the receiver module ( 8) by means of the coupling module (10) a noise signal (S) from at least one noise signal source (18) is supplied as a test signal, with a test module (12) a current transmission coefficient (Ü _v ), which is the ratio between a first noise signal, the a first path (S, Si) reaches the test module (12) without passing through the at least one antenna (2), and a second noise signal which is transmitted from the noise source (18) via a second path (at least one antenna (2)) S ', S ₂ ) arrives at the test module (12), specifies it, determines it and compares it with a reference transmission coefficient (Ü _v i _norm ) stored in a transmission matrix (14).

2. The method according to claim 1, in which an uncalibrated noise source is used as the at least one noise source (18).

3. The method according to claim 2, in which a switchable coupling circuit (44), by means of which the noise signal is coupled into the first or second path (Si, S ₂ ), between the first path (Si) and the second path (S ₂ ) is switched so that the noise signal is routed directly to the receiver (8) via the first path (Si), while via the second path (S ₂ ) a superimposition of the noise signal with a noise signal reflected by the at least one antenna (2) is passed to the receiver (8), and the second noise signal is detected on the basis of the transmission matrix and compared with the frequency characteristic of the first noise signal.

4. The method according to claim 2, in which a switchable coupling circuit (44) through which the noise signal is coupled into the first or second path (S _{1 #} S ₂ ) and in which the at least one antenna (2) reflected noise signal at an impedance (Z) with the noise signal superimposed, switching between the first path (S _x ) and the second path (S ₂ ), so that the noise signal goes directly to the receiver (8) via the first path (Si) is passed, while a superposition of the noise signal with a noise signal reflected by the at least one antenna (2) is passed to the receiver (8) via the second path (S ₂ ), and the second noise signal is detected using the transmission matrix and with the frequency characteristic of the first Noise signal is compared.

5. The method of claim 2, wherein a directionally selective coupling network (48) with switchable signal flow direction, through which the noise signal in the first or second path

(Si, S ₂ ) is coupled in, switches between the first path (S _x ) and the second path (S ₂ ), so that the noise signal from the noise source (18) as the first noise signal and that at the antenna (2 ) reflected noise signal (S ₂ ) for evaluation at the receiver (8).

6. The method according to claim 5, wherein the switching between the first path (S _x ) and the second path (S ₂ ) instead of at the inputs of the directionally selective switching network (48) by an additional switching device (49) in the first path (Si) and there is a switchable amplifier in the second path (S ₂ ),

7. The method according to claim 1, in which a calibrated noise source is used as the at least one noise source (18), the frequency characteristic of which is known, the test module (12) is supplied with a superposition of the first and second noise signals, which results in a characteristic frequency characteristic, and the characteristic frequency characteristic is compared with the known frequency characteristic of the calibrated noise source.

8. The method according to any one of claims 1 to 7, with an additional antenna which has no connection to the receiver module (8), into which the noise signal (S) is coupled and which this noise signal (S) as a test signal to the at least one antenna (2nd ) sends.

9. The method according to any one of claims 1 to 8, in which in a multi-antenna system (4) comprising a plurality of antennas (2) as a second noise signal, a noise signal (S ₂ ) reflected on the respective individual antennas ( ₂ ) and / or an between the antennas (2) transmitted noise signal (S '_; S ₂ ) is / are evaluated.

10. The method according to any one of claims 1 to 9, in which the transmission coefficient (Ü _v _ _. ) And the reference transmission coefficient (Ü _v in _o rm) are determined by means of a frequency and / or level analysis.

11. Arrangement (1) for testing at least one antenna (2) with a receiver module (8) and a coupling module (10) arranged between the at least one antenna (2) and the receiver module (8), in which the coupling module (10) is used Coupling a noise signal (S) from at least one noise source (18) into the at least one antenna (2) and into the receiver module (8) and a test module (12) for determining an instantaneous transmission coefficient (Ü _v ), which determines the ratio between a first noise signal that passes through a first path (S, Si) without passing through the at least one antenna (2) to the test module (12) arrives, and a second noise signal, which reaches the test module (12) from the noise source (18) via a second path (S ', S ₂ ) leading via the at least one antenna (2), and for comparing the momentary transmission coefficients (Ü _v i) are provided with a reference transmission coefficient (Ü _V i _norm ) stored in a transmission matrix (14).

12. The arrangement of claim 11, wherein the at least one noise source (18) is an uncalibrated noise source.

13. The arrangement according to claim 12, further comprising a switchable coupling circuit (44) through which the noise signal can be coupled into the first or second path (Si, S ₂ ), for switching between the first path (Si) and the second path ( S ₂ ), so that the noise signal can be fed directly to the receiver (8) via the first path (Si), while overlaying the noise signal with a noise signal reflected by the at least one antenna (2) via the second path (S ₂ ) Receiver (8) can be fed, the test module (12) detecting the second noise signal on the basis of the transmission matrix and comparing it with the frequency characteristic of the first noise signal.

14. The arrangement according to claim 12, further comprising a switchable coupling circuit (44) through which the noise signal can be coupled into the first or second path (Si, S ₂ ) and in which the noise signal reflected on the at least one antenna (2) an impedance (Z) can be superimposed with the noise signal, for switching between the first path (Si) and the second path (S ₂ ), so that the first Path (Si) the noise signal can be fed directly to the receiver (8), while overlaying the noise signal with a noise signal reflected by the at least one antenna (2) can be fed to the receiver (8) via the second path (S ₂ ), and that Test module (12) detects the second noise signal on the basis of the transmission matrix and compares it with the frequency characteristic of the first noise signal.

15. The arrangement according to claim 12, further comprising a directionally selective coupling network (48) with switchable signal flow direction, through which the noise signal can be coupled into the first or second path (S _i; S ₂ ), for switching between the first path (Si) and the second path (S ₂ ), so that the noise signal from the noise source (18) is provided as the first noise signal and the noise signal (S ₂ ) reflected on the antenna (2) is made available for evaluation on the test module (12) as the second noise signal can.

16. The arrangement according to claim 15, wherein an additional switching device (49) is formed in the first path (Si) and a switchable amplifier in the second path (S ₂ ), by means of which the switching between the first path (Si) and the second path ( S ₂ ) can take place instead of at the inputs of the directionally selective switching network (48).

17. The arrangement according to claim 11, wherein the at least one noise source (18) is a calibrated noise source whose frequency characteristic is known.

18. The arrangement according to claim 17, wherein the noise signal can be coupled into the path from the at least one antenna (2) to the test module (12) by means of a coupling network (24), so that a superposition of the first and the second noise signal (Si + S ₂ ) arises, where the superimposition gives a characteristic frequency characteristic, and the test module (12) compares the characteristic frequency characteristic with the known frequency characteristic of the calibrated noise source.

19. The arrangement according to claim 17, wherein the noise signal can be coupled into the path from the at least one antenna (2) to the test module (12) by means of a directionally selective coupling circuit (46), so that only the second noise signal (S ₂ ) is detected, and the test module (12) compares the characteristic frequency characteristic curve resulting from the second noise signal with the known frequency characteristic curve of the calibrated noise source.

20. The arrangement according to one of claims 11 to 19, further comprising an additional antenna, which has no connection to the receiver module (8), for transmitting the noise signal (S) as a test signal to the at least one antenna (2), the coupling module (10) couples the noise signal (S) into the additional antenna.

21. Arrangement according to one of claims 11 to 20, wherein the coupling module (10) for coupling the at least one antenna (2) comprises at least one RF switch (20).

22. Arrangement according to one of claims 11 to 21, in which the transmission matrix (14) in a multi-antenna system (4) has a number of transmitting antennas (2 (n)) and receiving antennas (2 (m)) corresponding to the number of antennas (2). as antenna pairs (2 (n, m)).