ANTENNA UNIT, TRANSMITTING SYSTEM AND METHOD FOR OPERATING AN ANTENNA UNIT

Description

[0001] The invention relates to a self-calibrating antenna unit, a transmission system with such an antenna unit and a method for operating such an antenna unit.

[0002] Antenna units that compensate for cable losses of a cable connection between the antenna unit and a signal provision unit, e.g. a modem, are known from the prior art.

[0003] For example, US Pat. No. 9,191,903 B2 discloses a method and a device for efficient external control of the transmission power of an antenna unit. Essential for the control is a feedback signal that the signal provision unit receives from the antenna unit.

[0004] US 9,491,713 B2 discloses a compensation module that can be connected to a transmitting / receiving unit and an antenna cable. The compensation module generates a parameter representing an output transmission power and transmits this parameter to the transmitting / receiving unit via the antenna cable.

[0005] A disadvantage of these solutions is that signal transmission from the antenna unit to the signal delivery unit is required for operation of the antenna unit, especially for adjusting a gain factor. This requires appropriate signal interfaces and signal processing. Overall, such an approach results in a complex and costly system.

[0006] Also known is US Pat. No. 7,965,977 B2. This discloses an antenna circuit with an amplifier unit for amplifying a transmission signal. A control unit controls the operation of the transmission amplifier. This method provides a so-called T / R control signal, which represents a cable loss in a coaxial cable to which the antenna circuit is connected.

[0007] Also known is US 5,634,191, which discloses that a signal strength is determined by a so-called base station extension unit and transmitted as a coded data stream to a so-called microcell extension unit with an antenna.

[0008] US2005 / 130595 A1 discloses a power control device and a method for calibrating the power of a transmitter or receiver of a mobile communication network.

[0009] US2013 / 002357 A1 discloses an apparatus comprising a power control loop for receiving a feedback signal from a power amplifier and for generating a first control signal for controlling a variable amplifier.

[0010] EP 0 461 314 A1 discloses transmission amplitude control or stabilization systems for antenna elements.

[0011] DE 10 2015 217 695 A1 discloses a communication device for a motor vehicle. The communication device comprises a transceiver unit and an antenna for transmitting transmission signals from the transceiver unit. The antenna is coupled to the transceiver unit via a cable. To compensate for signal attenuation of the cable in the transmission signals, an amplifier device is provided at the antenna-side end of the cable. The communication device can be provided, for example, for car-to-car communication (vehicle-to-vehicle communication).

[0012] US2007 / 129031 A discloses a method and apparatus for gain calibration and in particular for automatic calibration in a transceiver unit such as a HiperLAN transceiver.

[0013] These technical teachings also disadvantageously require data transmission of a control signal for adjusting the gain from a signal providing unit to the antenna unit.

[0014] The technical problem therefore arises of creating a self-calibrating antenna unit, a transmission system with such an antenna unit and a method for operating an antenna unit which enable efficient and simple operation of the antenna unit and reduce manufacturing costs for the antenna unit.

[0015] The solution to the technical problem results from the subject matter having the features of claims 1, 14 and 15. Further advantageous embodiments of the invention result from the subject matter having the features of the subclaims.

[0016] A method for operating an antenna unit is proposed. The antenna unit can be used, in particular, to transmit a signal. The antenna unit can also be used to receive a signal. The signal can be, in particular, a WLAN signal, furthermore, in particular, a signal according to the IEEE 802.11p standard. In this case, signals in a frequency range from 5.8 GHz to 5.9 GHz can be transmitted. The signal can also be a mobile radio signal, furthermore, in particular, a mobile radio signal according to the LTE-V2V (Long Term Evolution Vehicle to Vehicle) standard of the European ETSI 3GPP standards institute. Of course, it is also conceivable to transmit other signals via the antenna unit.

[0017] The antenna unit can be an antenna unit of a vehicle, in particular a motor vehicle. This is not mandatory, however. The antenna unit can also be used in other technical areas of application, e.g. in rail vehicles or in mobile devices, for the remote control of vehicles or other devices, or other areas of application in which antenna units are used for signal transmission. If the antenna unit is arranged in a motor vehicle, it can be used in particular for so-called car2car communication. The antenna unit can be arranged in or on the vehicle, e.g. in an interior rear-view mirror of the vehicle, be designed as a roof antenna, or be integrated into the bumper of the vehicle, in particular as a distributed antenna.

[0018] The antenna unit has an antenna-side signal interface and a device-side signal interface. An antenna for transmitting and / or receiving signals can be or be connected to the antenna-side signal interface. A signal provision unit, e.g. a transmitting / receiving unit, in particular a modem, can be or be connected to the device-side signal interface. It is possible for the antenna unit to be connected to the signal provision unit via a signal connection means, e.g. a signal cable, in particular a coaxial cable. Signal transmission can take place via the cable. Power can also be supplied to the antenna unit via the cable. Cable losses can occur during transmission via the cable.

[0019] The antenna unit can serve to amplify transmission signals transmitted or radiated by the antenna. Alternatively, or preferably cumulatively, the antenna unit can serve to amplify reception signals received by the antenna.

[0020] The antenna unit further comprises a control device, at least one device for adjusting a signal strength of a transmission signal, and at least one device for detecting a signal strength of the transmission signal. The control device can be designed as a microcontroller or comprise such a microcontroller. The device for adjusting a signal strength can increase a signal strength of a transmission signal. Alternatively or cumulatively, the signal strength can also be reduced. The device can be designed as an amplifier device, in particular as an amplifier device with an adjustable gain factor. Preferably, however, it is designed as an attenuator device. In particular, the device for adjusting the signal strength is a device whose gain and / or attenuation factor is adjustable and thus enables the signal strength to be adjusted even under constant operating conditions.

[0021] The device for detecting signal strength can generate a signal representing the signal strength, e.g., a voltage signal. This device can be configured, for example, as a power detector.

[0022] In particular, the signal strength detection device can detect the signal strength of a signal transmitted from the signal strength adjustment device to the antenna-side signal interface. In other words, the signal strength of an amplified signal can be detected. However, it is also possible for the signal strength detection device to detect the signal strength of a signal transmitted from the device-side signal interface to the signal strength adjustment device. In other words, the signal strength of an unamplified signal can be detected.

[0023] During a calibration process, a calibration signal is received via the device-side signal interface. The calibration signal can be provided, in particular generated, by the described signal provision unit, for example. The calibration signal can be transmitted from the device-side signal interface to the antenna-side signal interface via the signal strength adjustment device.

[0024] The calibration signal can be a communication signal, whereby a communication signal can contain communication or user data. In particular, the calibration signal can be a modulated signal. Preferably, the calibration signal is a modulated signal with a low crest factor, which describes the ratio of peak power to average power of the signal. This enables simple determination of the signal strength of the modulated signal. The calibration signal can also be an OFDM (Orthogonal Frequency-Division Multiplexing) modulated signal. This also enables the determination of the signal strength, although a temporal averaging of the signal strength over a time window of predetermined duration may be necessary to determine the signal strength. Of course, the modulated signal can also be modulated according to a different modulation method.

[0025] Alternatively, the calibration signal may not be a communication signal. In particular, it may not contain any communication or user data. For example, the calibration signal may be an unmodulated signal, in particular a so-called CW (continuous wave) signal or carrier signal.

[0026] The calibration signal is in particular a signal whose signal strength can be determined easily, reliably and accurately.

[0027] Furthermore, the signal strength of the calibration signal, in particular of an amplified calibration signal, is determined. The signal strength of the amplified calibration signal can be detected here. The signal strength of an amplified calibration signal can also be determined as a function of a signal strength of a calibration signal that is detected between the device-side signal interface and the antenna-side signal interface, in particular as a function of a detected signal strength of an unamplified calibration signal. The signal strength can be a signal power. In particular, the signal strength of the calibration signal transmitted via the device for adjusting the signal strength is determined. Furthermore, the signal strength determined in this way is compared with a reference signal strength. The reference signal strength can in particular be a predetermined signal strength, e.g., a predetermined maximum permissible transmission signal strength or a proportion thereof. This can, for example,be stored in a memory device of the antenna unit. The reference signal strength can be, for example, a predetermined maximum transmission signal strength or maximum desired transmission signal strength and can be, for example, 23 dBm.

[0028] Furthermore, in particular by means of the control device, an amplification factor of the at least one device for adjusting the signal strength is adjusted such that the difference between the reference signal strength and the signal strength of the amplified calibration signal is minimized. In particular, the amplification factor of the at least one device for adjusting the signal strength can be adjusted such that the difference between the reference signal strength and the determined signal strength is minimized.

[0029] In particular, the amplification factor of the at least one device for adjusting the signal strength can be adjusted such that the difference between the reference signal strength and a signal strength of an amplified calibration signal is smaller than a predetermined threshold value or that the signal strengths are equal.

[0030] The amplified calibration signal may refer to a calibration signal transmitted via the signal strength adjustment device. Such a signal is present on a signal connection between the signal strength adjustment device and the antenna-side signal interface. In particular, the amplified calibration signal may refer to a signal present at the antenna-side signal interface.

[0031] The gain factor can be an attenuation factor. In particular, the gain factor can be adjusted to amplify or attenuate a signal.

[0032] After the calibration process has been completed, the antenna unit is operated with the gain factor set in this way.

[0033] The signal strength of the amplified calibration signal can be detected, as previously explained, in particular by means of the detection device. This signal strength can also be determined, in particular mathematically, in particular as a function of an unamplified calibration signal. An unamplified calibration signal can refer to a calibration signal not transmitted via the device for adjusting the signal strength and is present between the device-side signal interface and the device for adjusting the signal strength. For example, a signal strength of an unamplified calibration signal can be determined, in particular detected as previously explained, and then multiplied by the set or to-be-set amplification factor and, if applicable, amplification factors of further amplification devices in order to determine the signal strength of the amplified calibration signal.

[0034] For example, it is possible to determine the signal strength of the unamplified calibration signal present at the device-side signal interface and then use this to determine the signal strength of the amplified calibration signal.

[0035] Thus, the reference signal strength can designate a signal strength that forms a reference value for the signal strength of a signal transmitted via the device for adjusting the signal strength and thus amplified, in particular for a signal present at the antenna-side signal interface. However, it is also conceivable that this reference signal strength—in accordance with the preceding explanations—is determined as a function of a reference value for the signal strength of a signal not transmitted via the device for adjusting the signal strength and thus unamplified, and of the amplification factor that has been set or is to be set, whereby the reference value thus forms a reference value for an unamplified signal.

[0036] According to the invention, the antenna unit comprises at least one transmission signal branch, wherein a transmission signal is transmitted from the device-side signal interface to the antenna-side interface via the transmission signal branch. The device for adjusting the signal strength can be arranged in the transmission signal branch. This can mean that the transmission signal can be transmitted from the device-side signal interface to the antenna-side signal interface via the device, wherein the signal strength of the transmission signal can also be adjusted, in particular changed. Furthermore, according to the invention, the device for detecting the signal strength is arranged in the transmission signal branch.

[0037] Furthermore, the antenna unit can also comprise at least one receive signal branch, wherein a receive signal can be transmitted from the antenna-side signal interface to the device-side interface via the receive signal branch.

[0038] In addition to the device for adjusting the signal strength, the antenna unit can comprise at least one amplifier device in the transmission signal branch, in particular a constant-gain amplifier device. This can also be referred to as a transmission amplifier device.

[0039] A constant-gain amplifier device can refer to an amplifier device whose gain cannot be adjusted, in particular not by a corresponding control signal. However, the gain of a constant-gain amplifier device can change when operating conditions change, e.g., when temperatures change. Thus, a constant-gain amplifier device can refer to an amplifier device whose gain is constant under constant operating conditions and cannot be changed.

[0040] Alternatively, it is also possible for the antenna unit to comprise at least one amplifier device with an adjustable gain factor in the transmission signal branch as a transmission amplifier device. This can form or provide the device for adjusting the signal strength.

[0041] The antenna unit can also comprise at least one additional amplifier device in the receive signal branch. This additional amplifier device can also be a constant-gain amplifier device or an amplifier device with an adjustable gain factor. This can also be referred to as a receive amplifier device. In particular, the signal strength of the calibration signal transmitted via the signal strength adjustment device and the transmit amplifier device can be determined using the signal strength detection device.

[0042] The control device, the at least one device for adjusting a signal strength of a transmission signal and the at least one device for detecting a signal strength of the transmission signal can be connected by signal technology.

[0043] Furthermore, the antenna unit can comprise a temperature sensor for detecting the temperature of the antenna unit. This sensor can be connected to the control device via signaling. Furthermore, the antenna unit can comprise a voltage sensor for detecting the level of the supply voltage of the antenna unit. This can be connected to the control device via signaling.

[0044] The calibration process can have a duration from a predetermined duration range, for example, from 1 ms to 5 ms. The calibration process can be performed in a calibration mode of the antenna unit. This can be activated to perform the calibration process. After the calibration process has been completed, a normal operating mode can be activated. The gain factor determined in the calibration process is then used in the normal operating mode. The normal operating mode can follow directly after the calibration mode. In calibration mode, the antenna unit is not used for the intended signal transmission of transmit or receive signals.

[0045] The proposed method advantageously results in simple and reliable calibration of the gain factor and thus reliable operation of the antenna unit by compensating for signal losses during signal transmission from the signal provision unit to the antenna unit. The determination and adjustment of the gain factor is carried out, in particular, exclusively by the antenna unit and requires no additional exchange of information with the signal provision unit. Thus, no information about signal strength, e.g., in the form of data, needs to be transmitted between the antenna unit and the signal provision unit. Due to the reduced need for data transmission, the antenna unit also operates more efficiently.Since no corresponding signal interface needs to be provided, manufacturing costs for the antenna unit and the signal provision unit can be reduced. This also enables easy retrofitting of an antenna unit, since it does not have to be designed for appropriate communication of the signal strength with the signal provision unit. Furthermore, it is advantageous that, alternatively or in addition to compensating for transmission-related signal losses, undesirably low signal strengths of the signal provided by the signal provision unit can be compensated for by the proposed method.

[0046] In a further embodiment, the calibration signal is generated by a signal provision unit and transmitted to the antenna unit via a signal connection means via the device-side signal interface. This advantageously results in simple generation of the calibration signal, since the antenna unit is also connected to the signal provision unit during normal operation. It is therefore possible for the signal provision unit to generate the necessary calibration signal during the calibration process. For this purpose, the signal provision unit can also be put into a calibration mode, in particular simultaneously with the antenna unit. The calibration mode of both units can preferably be activated simultaneously, for example immediately after both units are switched on or activated simultaneously.The sequence and type of functions performed during calibration mode can be stored in the corresponding unit, for example in firmware.

[0047] In a further embodiment, the signal provision unit generates the calibration signal with the maximum achievable signal strength or with a signal strength corresponding to a predetermined proportion of the maximum signal strength. It is possible that information about the magnitude of the proportion is stored, e.g., in a memory device of the antenna unit.

[0048] This enables a simple determination of the reference signal strength, which can be related, in particular, to the antenna-side signal interface. In particular, if the calibration signal is generated with the maximum signal strength that can be generated by the signal provision unit, it can be assumed that the antenna unit should generate a transmission signal with a predetermined (desired) maximum transmission signal strength. This, in turn, enables a simple determination of the amplification factor. The same applies if the calibration signal is generated with a proportional maximum signal strength that can be generated.

[0049] In a further embodiment, the reference signal strength, in particular a signal strength related to the antenna-side signal interface, is determined such that the ratio of the reference signal strength to the predetermined maximum transmission signal strength is equal to the ratio of the signal strength of the signal generated by the signal provision unit to the maximum producible signal strength. This advantageously results in improved operational reliability during subsequent normal operation of the antenna unit, since the probability of unwanted generation of transmission signals with excessively high signal strengths is reduced.

[0050] In a further embodiment, the maximum signal strength of the calibration signal that can be generated by the signal provision unit is determined as a function of the detected signal strength of the calibration signal. It is possible, for example, that different types of signal provision units exist that can generate different maximum signal strengths, e.g. 5 dBm or 20 dBm. Therefore, in such a calibration process, it may be necessary for the antenna unit to determine the maximum signal strength that can be generated by a signal provision unit connected to the antenna unit. In particular, the determination can exist as a function of a previously known assignment in which different signal strength ranges are assigned to different maximum signal strengths that can be generated by a signal provision unit. This assignment can, for example, be stored in the antenna unit.

[0051] Depending on the maximum signal strength that can be generated and / or the detected signal strength determined in this way, the previously explained proportion or the previously explained ratio can also be determined. For this purpose, an assignment between a proportion and a signal strength of the calibration signal can exist, in particular for each identifiable maximum signal strength that can be generated, whereby the proportion can be determined depending on this assignment.

[0052] This advantageously results in greater reliability and accuracy during calibration, particularly if the calibration signal is not generated by the signal provision unit with the maximum signal strength that can be generated.

[0053] In a further embodiment, a calibration process is performed each time the antenna unit is switched on or activated. In other words, the calibration mode can be activated each time the antenna unit is switched on. "Activating" can mean that the antenna unit is switched from a not fully operational state to a fully operational mode. Switching on or activating can occur, in particular, when a power supply to the antenna unit required for normal operation is established.

[0054] If such a power supply is provided by the signal provision unit, e.g., via the cable described above, switching on or activating the signal provision unit can lead to the switching on or activation of the antenna unit simultaneously or almost simultaneously. This advantageously results in the fact that the switching on or activation processes of the units, and thus also the activation of the corresponding calibration modes, can be reliably synchronized.

[0055] If the antenna unit is located in a vehicle, the antenna unit can be switched on or activated whenever the vehicle's "ignition on" state is established.

[0056] In a preferred embodiment, the device for adjusting the signal strength is, for example, an attenuator. In this case, the gain factor is an attenuation factor. With the attenuator, the signal strength of a signal transmitted via the attenuator can be reduced or left unchanged, but not increased. This advantageously results in simple manufacture of an antenna unit. In particular, existing antenna units without adjustable gain can be retrofitted, e.g., with the previously explained constant amplifier devices, which regularly exist as prefabricated modules that correspond to desired standards, in order to enable self-calibration.

[0057] Alternatively, the device for adjusting the signal strength is an amplifier device with an adjustable gain factor.

[0058] In a further embodiment, the signal strength adjustment device can adjust or change both the signal strength of a transmitted signal and the signal strength of a received signal. In other words, the signal strength adjustment device can be arranged in both the transmitted and received signal branches. This advantageously results in balanced amplification between the transmitted signal and the received signal, which can, for example, fulfill approval requirements. It also prevents the antenna unit from over-amplifying the received signal and exposing the signal delivery unit to excessive signal power.

[0059] In a further embodiment, a temperature or a temperature change of the antenna unit is determined, wherein, in particular after completion of the calibration process, the gain factor of the device for adjusting the signal strength, in particular the gain factor determined in the calibration process, is changed, e.g., increased or decreased, depending on the temperature or the temperature change. In particular, the gain factor can be changed in a temperature-dependent manner such that a temperature-related change in the overall gain of the antenna unit is minimized or completely compensated. In other words, the gain factor can be changed in a temperature-dependent manner in the event of temperature changes of the antenna unit such that the overall gain of the antenna unit remains constant or approximately constant.

[0060] For example, it is possible for the gain factor to be adjusted, in particular changed, depending on a previously known relationship between a temperature or a temperature change and a gain factor or a change in the gain factor. The previously known relationship can be given, for example, in the form of a function or an assignment, in particular in the form of a characteristic curve.

[0061] It is particularly possible for a temperature to be determined as the reference temperature during the calibration process, with the gain factor then being changed depending on a difference between the reference temperature and the currently determined temperature. For example, it is possible for the gain factor to be set, or in particular changed, depending on a previously known relationship between the difference and a gain factor or a change in the gain factor. This previously known relationship can also be given, for example, in the form of a function or an assignment, in particular in the form of a characteristic curve. For example, the smaller the value of the difference, the more the transmission signal can be amplified, with a signed consideration being made. As the temperature increases, the gain of the amplifier device for the transmission signal can decrease.To keep the overall gain of the antenna unit constant over temperature, the gain factor of the signal adjustment device, e.g., the attenuation device, can be reduced so that the overall gain of the antenna unit remains constant. In other words, a signal gain factor can also be increased, for example, as temperatures rise above the reference temperature.

[0062] By such a temperature-dependent adjustment of the gain factor, it can be achieved that, depending on the temperature change, the maximum reference power (e.g. 23 dBm) of the antenna unit is not exceeded or undercut when the signal delivery unit transmits at the maximum power.

[0063] This advantageously increases the operating quality of the antenna unit, in particular since temperature-related changes in the gain can be compensated completely or at least partially.

[0064] In a further embodiment, a level of the supply voltage of the antenna unit is determined. The supply voltage can in particular also be a supply voltage of a constant amplifier device, e.g. the transmit amplifier device. Furthermore, in particular after completion of the calibration process, the gain factor of the device for adjusting the signal strength, in particular the gain factor determined in the calibration process, is changed depending on the level of the supply voltage. In particular, the gain factor can be changed in a supply voltage-dependent manner such that a supply voltage-related change in the overall gain of the antenna unit is minimized or completely compensated. In other words, the gain factor can be changed in a supply voltage-dependent manner when the supply voltage of the antenna unit changes such that the overall gain of the antenna unit is constant or approximately constant.

[0065] For example, it is possible for the gain factor to be adjusted, in particular changed, depending on a previously known relationship between the supply voltage level or a change in the supply voltage level and a gain factor or a change in the gain factor. The previously known relationship can be given, for example, in the form of a function or an assignment, in particular in the form of a characteristic curve.

[0066] In particular, it is possible for a supply voltage level to be determined as the reference supply voltage level during the calibration process, with the gain factor being changed depending on a difference between the reference supply voltage level and the currently determined supply voltage level. In this case, it is possible, for example, for the gain factor to be set, in particular changed, depending on a previously known relationship between the difference and a gain factor or a change in the gain factor. The previously known relationship can be given, for example, in the form of a function or an assignment, in particular in the form of a characteristic curve.

[0067] In particular, the smaller the difference value, the more the transmitted signal can be amplified, with a signed consideration. For example, as the supply voltage level increases above the reference supply voltage, the signal amplification factor can be reduced.

[0068] This advantageously increases the operating quality of the antenna unit, in particular since changes in the gain due to the supply voltage can be completely or at least partially compensated.

[0069] According to the invention, during the calibration process, the amplified calibration signal is not transmitted to an antenna, in particular to an antenna connected to the antenna-side signal interface. In particular, the amplified calibration signal can be fed into or transmitted to an antenna equivalent resistor. Furthermore, incorrect calibration, which would occur if external influences were to change the antenna properties, can be advantageously avoided.

[0070] For this purpose, the antenna equivalent resistor can be connected to the antenna-side signal interface or the transmission signal branch can be connected to the antenna equivalent resistor instead of to the antenna-side signal interface, e.g. via a suitable switching means of the antenna unit.

[0071] This advantageously results in improved operational reliability of the antenna unit, since during the calibration process the antenna does not send a signal that could, for example, interfere with the operation of other units.

[0072] In a further embodiment, a transmission mode of the antenna unit is activated, wherein the calibration process is carried out in the transmission mode. In particular, the calibration process can only be carried out when the transmission mode is activated. The transmission mode can be activated, for example, when an activation signal is received from the antenna unit or when a mode control signal has a predetermined signal level. Furthermore, a reception mode can also be activated, for example, when no activation signal is received or the mode control signal does not have the predetermined signal level. In the transmission mode, a signal connection is established between the device-side signal interface and the antenna-device-side signal interface via a transmission signal branch. Accordingly, in the reception mode, a signal connection is established between the device-side signal interface and the antenna-device-side signal interface via a reception signal branch.

[0073] Preferably, the activation signal or mode control signal is generated by the signal providing unit and transmitted to the antenna unit, e.g., via the previously explained signal connection means. In the antenna unit, the activation signal or mode control signal can be extracted, e.g., filtered out or decoupled, from the transmitted signal. The activation signal or mode control signal can have frequencies from a frequency range that differ from frequencies of the communication signal, e.g., frequencies from a range of 120 MHz to 130 MHz. Thus, the calibration process can, e.g., only be carried out if the signal providing unit generates a corresponding activation signal or mode control signal. It is, for example, possible for the signal providing unit to always generate a corresponding activation signal or mode control signal after switching on or activation.

[0074] Alternatively, it is also possible for the transmission mode to be activated for the calibration process independently of the activation or mode control signal. For example, it is possible for the antenna unit to always activate the transmission mode after being switched on or activated.

[0075] This advantageously results in increased reliability when carrying out the calibration.

[0076] It is also possible that during normal operation of the antenna unit, i.e. even after completion of the calibration process, the transmission or reception mode of the antenna unit is set with the activation signal or mode control signal, in particular by the signal provision unit.

[0077] In a further embodiment, the gain factor is determined at the beginning of the calibration process as a function of at least one gain factor determined in a previous calibration process. It is possible, for example, for the gain factor determined in a calibration process to be stored, e.g., in a memory device of the antenna unit. For example, at the beginning of a current calibration process, the gain factor can then be set to the gain factor stored in a calibration process, in particular in the immediately preceding one.

[0078] The gain factors determined in all or a predetermined number of calibration processes can also be saved. For example, at the beginning of a current calibration process, the gain factor can be set to an average value of these multiple saved gain factors.

[0079] This advantageously results in an accelerated determination of the gain factor during the calibration process, since it can generally be assumed that the gain factor will not change between two calibration processes, especially calibration processes that follow one another in close time, or will not change by more than a predetermined amount. Thus, using the previously determined gain factor as the starting value during the determination usually leads to a rapid determination of the currently valid gain factor.

[0080] In a further embodiment, the control device detects an error condition if the minimized difference is greater than a predetermined threshold value. If an error condition is detected, the operating behavior of the antenna unit can be changed, in particular by the control device. For example, one or more constant amplifier devices can be deactivated. The connection to the antenna can also be interrupted. A connection to the explained antenna equivalent resistor can also be established. This advantageously makes it possible for an error in calibration to be detected by external devices, e.g. the signal provision unit, without the antenna unit having to transmit error data. For example, the signal provision unit can determine a current strength of a signal transmitted via the signal connection means and detect an error condition depending on the current strength.If an error is detected, suitable error measures can be initiated, e.g. the output of an error signal to a higher-level system or a user.

[0081] It should be noted here that a fault condition can be detected by an external device even without changing the antenna unit's operating behavior. For example, even a gain factor that does not reduce the aforementioned difference to zero or a predetermined level can result in the antenna unit's operating behavior being adjusted in such a way that the signal delivery unit detects a fault condition depending on the aforementioned current intensity.

[0082] In a further embodiment, a signal strength of the transmitted signal is determined, particularly after completion of the calibration process, wherein the amplification factor, particularly the amplification factor determined in the previous calibration process, is varied depending on the signal strength. The signal strength can be detected by the device for detecting the signal strength described above. Furthermore, the amplification factor can be adjusted, in particular, such that a predetermined maximum permissible limit of the signal strength is not exceeded.

[0083] This advantageously increases the operational reliability of the antenna unit.

[0084] A self-calibrating antenna unit is also proposed. The antenna unit is configured according to one of the embodiments disclosed in this disclosure.

[0085] In a calibration process, a calibration signal can be received via the device-side signal interface, wherein the signal strength of the calibration signal, in particular of an amplified or unamplified calibration signal, can be determined, wherein the determined signal strength, in particular the signal strength of an amplified calibration signal, is comparable to a reference signal strength, wherein an amplification factor of the at least one device for adjusting the signal strength can be adjusted such that the difference between the reference signal strength and the determined signal strength, in particular a signal strength of the amplified calibration signal, is minimized, wherein the antenna unit can be operated with the amplification factor adjusted in this way after the calibration process has been completed.

[0086] Thus, the antenna unit is configured such that a method according to one of the embodiments described in this disclosure can be carried out with the antenna unit.

[0087] It is possible, but not mandatory, for the antenna unit to comprise an interface for data transmission, e.g., for communication, with an external unit, in particular with the signal provision unit. Diagnostic information or information about error states, for example, can be transmitted via this interface. However, the interface is not designed, in particular, to transmit information about a gain factor from the antenna unit to an external unit or from an external unit to the antenna unit. Of course, the antenna unit can also be designed such that it does not comprise such an interface.

[0088] Further proposed is a transmission system comprising a self-calibrating antenna unit according to one of the embodiments described in this disclosure and a signal provision unit, wherein the antenna unit and the signal provision device are connected via a signal connection means. This and corresponding advantages have already been explained above.

[0089] It is possible for the antenna unit and the signal provision unit to be connected exclusively via the signal connection means, via which a signal provided or generated by the signal provision unit is transmitted to the antenna unit for transmission, or a signal received by the antenna unit is transmitted to the signal provision unit. In particular, the system, and furthermore, in particular the elements of the system, can be configured such that no information about an amplification factor is transmitted between the units via the signal connection means.

[0090] The invention is explained in more detail using exemplary embodiments. The figures show: Fig. 1 is a schematic block diagram of a transmission system according to the invention according to a first embodiment, Fig. 1a is a schematic block diagram of a transmission system according to the invention according to a further embodiment, Fig. 2 is a schematic block diagram of a transmission system according to the invention according to a further embodiment, Fig. 3 is a schematic block diagram of a transmission system according to the invention according to a further embodiment, Fig. 4 is a schematic flow diagram of a method according to the invention and Fig. 5 is a schematic block diagram of a transmission system according to the invention according to a further embodiment.

[0091] In the following, the same reference symbols designate elements with the same or similar technical features.

[0092] Fig. 1 shows a schematic block diagram of a transmission system 1 according to the invention. The transmission system 1 comprises a signal provision unit 2, which can be designed, for example, as a modem. In particular, the signal provision unit 2 can be designed as a transmission / reception unit. This can be used to transmit and receive WLAN signals, in particular WLAN signals according to the IEEE 802.11p standard or mobile radio signals according to the LTE-V2V (Long Term Evolution Vehicle to Vehicle) standard of the European ETSI 3GPP standards institute. The transmission / reception unit 2 is connected to an antenna unit 4 according to the invention via a signal connection means designed as a coaxial cable 3. The antenna unit 4 comprises a device-side signal interface 5, via which the antenna unit 4 is connected to the transmission / reception unit 2 by means of the coaxial cable 3. The antenna unit 4 further comprises an antenna-side signal interface 6.An antenna 7 can be connected to the antenna unit 4 via the antenna-side signal interface 6. It is possible for the antenna unit 4 to also include the antenna 7. For example, elements of the antenna unit 4 and the antenna 7 can be arranged on a common circuit board. However, this is not mandatory.

[0093] The antenna unit 4 further comprises a control device 8. This control device 8 can be designed as a microcontroller or comprise a microcontroller. The antenna unit 4 further comprises a device designed as an attenuator device 9 for adjusting or changing the signal strength of a transmission signal. A transmission signal is generated by the signal provision unit 2 and transmitted to the antenna unit 4 via the coaxial cable 3 and the device-side signal interface 5. The transmission signal is then transmitted from the device-side signal interface 5 via the attenuator device 9 and an amplifier device 10, also referred to as a transmission amplifier device, of the antenna unit 4 to the antenna-side signal interface 6 and from there to the antenna 7. The transmission amplifier device 10 can be designed as a constant-gain amplifier device. Thus, the antenna unit 4 also comprises the transmission amplifier device 10.Both the attenuator device 9 and the constant amplifier device 10 are arranged in a transmission signal branch of the antenna unit 4.

[0094] The antenna unit further comprises a device designed as a power detector 11 for detecting the signal strength of a transmitted signal. The power detector 11 is shown detecting the signal strength of a signal transmitted from the constant amplifier device 10 to the antenna-side signal interface 6, i.e., an amplified signal. The power detector 11 can, for example, generate a voltage signal that represents the signal strength or signal power of the transmitted signal, in particular, is proportional thereto. The power detector 11 is connected to the control device 8 for signal processing purposes.

[0095] It is further shown that the antenna unit 4 comprises a temperature sensor 12 for detecting a temperature of the antenna unit 4. This temperature sensor 12 is also connected to the control device 8 via signaling.

[0096] It is possible for a transmit amplifier device 10 with a power detector 11 and a temperature sensor 12 to be implemented as an integrated circuit 22. This joint implementation is visualized by a block shown with dashed lines and can also be referred to as a front-end module.

[0097] The damper device 9 can be a so-called variable damper device. In particular, the damper device 9 can be designed as a digital attenuator. The damper device 9 is connected to the control device 8 for signal transmission. The control device 8 can adjust an attenuation factor of the damper device 9. By means of the damper device 9, a signal strength of the transmission signal transmitted from the device-side signal interface 5 to the damper device 9 can be reduced, in particular if the attenuation factor is greater than 1. The signal strength can also be left unchanged, in particular if the attenuation factor is 1. Amplification of this signal by means of the damper device 9 is not possible.

[0098] The antenna unit 4 shown forms a self-calibrating antenna unit 4. During a calibration process of the antenna unit 4, an attenuation factor can be determined. This attenuation factor is used by the control device 8 for the operation (normal operation) of the antenna unit 4 after the calibration process has ended. The attenuation factor can be determined by the control device 8 as a function of the output signal of the power detector 11.

[0099] It is possible that the antenna unit 4 is supplied with power by the signal supply unit 2, with the corresponding energy being transmitted via the coaxial cable 3.

[0100] A calibration process can be performed, for example, immediately after each switching on or activation of the antenna unit 4. If the power supply is provided by the signal provision unit 2, the calibration process can be performed after each switching on or activation of the signal provision unit 2, since in this case the antenna unit 4 is always switched on or activated when the signal provision unit 2 is also switched on or activated.

[0101] During a calibration process, the antenna unit 4 receives a calibration signal via the device-side signal interface 5. The calibration signal can be generated by the signal provision unit 2. It is possible, for example, for the signal provision unit 2 to also perform a calibration process after each switching on or activation or to participate in the calibration process of the antenna unit 4, e.g., by the signal provision unit 2 generating the calibration signal immediately after switching on or activation. A corresponding functionality of the signal provision unit 2 can be provided, for example, by encoding the corresponding functionality in the firmware of the signal provision unit 2.

[0102] Preferably, the signal providing unit 2 generates a calibration signal with the maximum signal strength that can be generated by the signal providing unit 2. This can be, for example, 5 dBm or 20 dBm.

[0103] Furthermore, the calibration process determines the signal strength of the calibration signal transmitted via the attenuator device 9 and the transmit amplifier device 10 and thus amplified. This can be done using the power detector 11 and the control device 8.

[0104] Furthermore, the signal strength determined in this way is compared with a reference signal strength, in particular also by the control device 8. The reference signal strength can, for example, be a predetermined maximum transmission signal strength that is to be set by the antenna unit 4 for a transmission signal transmitted from the antenna-side signal interface 6 to the antenna 7. Such a predetermined maximum transmission signal strength can, for example, be 23 dBm. Of course, it is also possible to select other predetermined maximum transmission signal strengths. It is possible that the reference signal strength is stored, for example, in a Fig. 1 illustrated memory device of the antenna unit 4, or an internal memory device of the control device 8, e.g. a memory in a microcontroller.

[0105] Furthermore, the control device 8 adjusts the attenuation factor of the attenuation device 9 such that the difference between the reference signal strength and the determined signal strength of the calibration signal is minimized. Preferably, the attenuation factor is adjusted such that the difference is 0 or does not deviate from 0 by more than a predetermined amount.

[0106] After the calibration process is completed, the antenna unit 4, in particular the attenuator device 9, is then operated with the attenuation factor determined in this way. It is also possible to store the attenuation factor determined in a calibration process, for example, also in the previously explained storage device or in another storage device. In this case, in particular, it is possible for the attenuation factor to be adjusted at the beginning of a new calibration process depending on an attenuation factor determined in a previous calibration process.

[0107] The described calibration process advantageously makes it possible to compensate for signal losses caused by the coaxial cable without requiring additional signal transmission between the antenna unit 4 and the signal provision unit 2. Illustratively speaking, assuming that the maximum producible signal strength is provided by the signal provision unit 2 during a calibration process, the attenuation factor is determined such that a predetermined, desired maximum transmission signal strength is provided by the antenna unit 4 at the antenna-side signal interface 6. Thus, it can be assumed that the attenuation factor is determined such that the cable losses caused by the coaxial cable 3 are compensated.Since the cable losses are not dependent on the signal strength, the attenuation factor set in this way ensures reliable and accurate compensation of the cable losses even in normal operation following the calibration process, in particular for signal strengths that deviate from the maximum signal strength that can be generated by the signal provision unit 2.

[0108] However, it is also possible for the signal provision unit 2 to generate a calibration signal during a calibration process not with the maximum achievable signal strength, but with a signal strength that corresponds to a predetermined proportion of the maximum achievable signal strength. Information, in particular a numerical value of this proportion, can be predetermined. This information can be stored, for example, also in the previously explained memory device of the antenna unit 4.

[0109] In this case, a proportion of the predetermined maximum transmission signal strength can be selected as the reference signal strength. During such a calibration process, however, it may be necessary for the antenna unit 4 to determine the maximum signal strength that can be generated by a signal provision unit 2 connected to the antenna unit 4. It can be assumed that different signal provision units 2 can generate different maximum signal strengths. The determination or identification of the maximum signal strength that can be generated can be carried out depending on the signal strength of the calibration signal determined during the calibration process. For example, an assignment can exist in which different signal strength ranges are assigned to different maximum signal strengths that can be generated by a signal provision unit 2.This assignment can be stored, for example, in the antenna unit 4, in particular in one of the previously explained storage devices. The maximum signal strength that can be generated by the signal provision unit 2 can then be determined depending on this assignment. If, for example, it is known that different types of signal provision units 2 can generate either a maximum signal strength of 5 dBm or 20 dBm, it can be assumed that for signal strengths of the calibration signal less than 5 dBm, the maximum signal strength that can be generated by the signal provision unit 2 is 5 dBm, whereas for signal strengths of the calibration signal greater than 5 dBm, the maximum signal strength that can be generated by the signal provision unit 2 is 20 dBm.

[0110] Furthermore, the corresponding component can also be determined depending on the maximum signal strength that can be generated in this way. For this purpose, an assignment between a component and a signal strength of the calibration signal can exist, in particular for each identifiable maximum signal strength that can be generated, whereby the component can be determined depending on this assignment.

[0111] It is further possible that the temperature of the antenna unit 4 is determined during the calibration process, in particular by means of the temperature sensor 12. This can, for example, be stored, in particular in one of the storage devices explained above.

[0112] After the calibration process has been completed, particularly during normal operation of the antenna unit 4, the temperature of the antenna unit 4 can then be continuously determined using the temperature sensor 12. Furthermore, the attenuation factor can be adjusted, in particular changed, depending on the difference between the currently detected temperature and the temperature detected during the previous calibration process. For example, at temperatures higher than the temperature of the calibration process, the attenuation factor can be adjusted to a lower value, the higher the said difference.

[0113] Not in Fig. 1 It is shown that a supply voltage level of the antenna unit 4, in particular a supply voltage level of the transmitting amplifier device 10, can also be determined. For this purpose, the antenna unit 4 can have a Fig. 1 The voltage sensor shown here can be used to determine the supply voltage level during the calibration process. This can be stored, for example, in particular in one of the previously explained storage devices.

[0114] Furthermore, the supply voltage level can be continuously recorded during normal operation. Furthermore, the attenuation factor can be adjusted depending on the difference between the currently recorded supply voltage level and the supply voltage level recorded during the calibration process. For example, if the currently recorded supply voltage level is lower than the supply voltage level recorded during the calibration process, the attenuation factor can be reduced as the difference or the magnitude of the difference increases.

[0115] It is also possible for the signal strength of the transmission signal to be continuously determined, in particular by means of the power detector 11. If the signal strength detected by the power detector 11 exceeds a predetermined, maximum permissible signal strength, the attenuation factor of the attenuator device 9 can be adjusted, in particular by means of the control device 8, such that the transmission signal strength is set to the maximum permissible transmission signal strength and thus limited. This advantageously ensures that no undesirable operating state of the antenna unit 4 occurs and no desired high transmission power is continuously transmitted by the antenna unit 4.

[0116] In other words, self-calibration of the antenna unit 4 is enabled. During the calibration process, an attenuation factor, which is exemplified for a gain factor, is determined, which is then set for normal operation following the calibration process. This attenuation factor is ideally constant during normal operation. However, in order to compensate for changes in the gain behavior of the antenna unit 4 during normal operation that are temperature- and / or supply voltage-related, the attenuation factor determined by the self-calibration can also be changed during normal operation. The attenuation factor can also be changed during normal operation in order to limit the maximum generated transmission signal strength to a maximum permissible transmission signal strength.

[0117] Fig. 1a shows a schematic block diagram of a transmission system 1 according to the invention in a further embodiment. Fig. 1a The transmission system 1 shown is essentially like the one in Fig. 1 The transmission system 1 shown in Figure 1 is designed as shown in Figure 1. Therefore, the corresponding explanations regarding Fig. 1 In contrast to Fig. 1 the power detector 11 detects the signal strength of a signal which is transmitted from the device-side signal interface 5 to the damper device 9, i.e. an unamplified signal.

[0118] Furthermore, in a calibration process, the signal strength of the (unamplified) calibration signal transmitted from the device-side signal interface 5 to the damper device 9 is determined. This can be done using the power detector 11 and the control device 8. Furthermore, the signal strength of the amplified calibration signal is determined, in particular using the control device 8, by multiplying the detected signal strength by the currently set amplification factors of the damper device 9 and the constant amplifier device 10.

[0119] Furthermore, the signal strength of the amplified calibration signal determined in this way is compared with a reference signal strength, in particular also by the control device 8.

[0120] Furthermore, the control device 8 adjusts the attenuation factor of the attenuation device 9 such that the difference between the reference signal strength and the signal strength of the amplified calibration signal determined as explained is minimized. Preferably, the attenuation factor is adjusted such that the difference is 0 or does not deviate from 0 by more than a predetermined amount.

[0121] After completion of the calibration process, the antenna unit 4, in particular the damper device 9, is then operated with the damping factor determined in this way.

[0122] Fig. 2 shows a block diagram of a transmission system 1 according to the invention in a further embodiment. Reference can be made here to the explanations for Fig. 1 In contrast to the Fig. 1 In the embodiment shown, in addition to the previously explained transmission signal branch, a reception signal branch is also shown. Via the reception signal branch, a signal received by the antenna 7 can be transmitted to the antenna unit 4 via the antenna-side signal interface 6. The antenna unit 4 here comprises a further amplifier device 13, also referred to as a reception amplifier device, for amplifying such a reception signal, which can be designed as a constant amplifier device. It is further shown that the antenna unit 4 comprises switching means 14 for establishing signal connections via a transmission signal branch or the reception signal branch. In a transmission mode, the switching means 14 are controlled such that a transmission signal is transmitted from the device-side signal interface 5 via the attenuator device 9 and the transmission amplifier device 10 to the antenna-side signal interface 6.In a reception mode, the switching means 14 can be controlled such that a signal connection is established from the antenna-side signal interface 6 via the reception amplifier device 13 and the attenuator device 9 to the device-side signal interface 5.

[0123] The switching means 14 can be controlled by the control device 8.

[0124] It is further shown that the antenna unit 4 comprises a resistance-side signal interface 15, to which an antenna equivalent resistor 16 is connected. Furthermore, the antenna unit 4 comprises a further switching means 17. By means of the further switching means 17, a signal output of the transmission amplifier device 10 can be connected either to the antenna-side signal interface 6 or to the resistance-side signal interface 15. The further switching means 17 can also be controlled by the control device 8.

[0125] During the calibration process, the further switching means 17 can be controlled in particular such that the signal output of the transmission amplifier device 10 is connected to a reference or ground potential via the equivalent resistor 16 to amplify the transmission signal (and thus the calibration signal). This advantageously ensures that no transmission signal, which could form an undesirable interference signal, is emitted by the antenna 7 during the calibration process.

[0126] Further on, Fig. 2 It is shown that the attenuator device 9 is arranged in both the transmit signal branch and the receive signal branch. Thus, in normal operation, the attenuation factor determined during the calibration process then forms both the attenuation factor set in transmit mode and the attenuation factor set in receive mode of the antenna unit 4. This advantageously results in simple manufacture of the self-calibrating antenna unit 4, since the unit comprising the transmit amplifier device 10, the power detector 11, and the temperature sensor 12, and optionally the receive amplifier device 13, as well as the switching means 14, is generally available as a prefabricated module, thus enabling simple expansion of the antenna unit 4. Furthermore, it is advantageous that approximately equal amplification occurs in the transmit and receive branches.

[0127] Fig. 3 shows a further schematic block diagram of a transmission system 1 according to the invention in a further embodiment. The antenna unit 4 of the transmission system 1 is essentially like the one in Fig. 2 The antenna unit 4 shown in FIG. Therefore, the corresponding explanations regarding Fig. 2 In contrast to the Fig. 2 In the antenna unit 4 shown, the antenna unit 4 comprises a signal extraction means 18, which is arranged in a signal branch section between the device-side signal interface 5 and the attenuator device 9. By means of the signal extraction means 18, a signal component with a predetermined frequency or with frequencies from a predetermined frequency range can be extracted from a signal present on this signal branch section. The antenna unit 4 further comprises a signal level detector 19 for determining the signal level of the thus extracted signal component. This signal level detector 19 can, for example, generate a voltage signal that represents the signal level, in particular is proportional to it. The antenna unit 4 further comprises a comparator 20, which compares the thus determined signal level with a predetermined threshold value. A signal output of the comparator is connected to the control device 8 for signal purposes.

[0128] The signal extraction means 18, the signal level detector 19, and the comparator 20 serve to set a transmission mode or a reception mode of the antenna unit 4. In particular, the transmission mode can be activated if the control device 8 detects that the signal level of the extracted signal component is greater than or equal to the predetermined threshold. In this case, the control device 8 can control the switching means 14 such that the signal connection between the device-side signal interface 5 and the antenna-side signal interface 6 is established via the transmission amplifier device 10.If the control device 8 detects that the signal level of the extracted signal component is less than the predetermined threshold, the receive mode can be activated and the switching means 14 can be controlled such that the signal connection between the antenna-side signal interface and the device-side signal interface 5 is established via the receive amplifier device 13. Furthermore, it is possible for the calibration process to be performed only when the antenna unit 4 is in transmit mode.

[0129] Fig. 4 shows a schematic flow diagram of a method according to the invention. In a first step S1, a transmission system 1 or a signal provision unit 2 and an antenna unit 4 (see e.g. Fig. 1 ) is switched on or activated. This can be done, for example, by switching the transmitting system 1 or the signal provision unit 2 and the antenna unit 4 from a not fully operational state to a fully operational state, for example by establishing the power supply.

[0130] In a second step S2, a calibration signal is generated by the signal providing unit 2, wherein the calibration signal is generated with the maximum signal strength that can be generated by the signal providing unit 2. The maximum signal strength that can be generated can, for example, be the maximum signal power of the signal providing unit 2. This calibration signal is generated by the signal providing unit 2 via the Fig. 1 coaxial cable 3 shown to the antenna unit 4 and received by the antenna unit 4. In a third step S3, the signal strength of the calibration signal is determined, in particular by means of the Fig. 1 illustrated power detector 11. In particular, the signal strength of the calibration signal transmitted via the attenuator device 9 and the transmission amplifier device 10 can be determined. In a fourth step S4, the signal strength of the calibration signal determined in this way is compared with a reference signal strength. In a fifth step S5, an attenuation factor of an attenuator device 9 of the antenna unit 4 is set such that the difference between the reference signal strength and the determined signal strength of the calibration signal is minimized. In a sixth step S6, the calibration process is terminated, wherein the antenna unit 4, in particular the attenuator device 9, is then operated in a subsequent normal operation with the previously determined attenuation factor.

[0131] It is possible that during the sequence from the first step S1 to the sixth step S6, a temperature of the antenna unit 4 and / or a supply voltage level of the supply voltage of the antenna unit 4 may also be determined. These may be stored.

[0132] In normal operation of the antenna unit 4 following the sixth step S6, the temperature can then be continuously recorded and compared with the temperature stored during the calibration process. The attenuation factor determined during the calibration process can be changed as previously depending on the difference. The same applies to the supply voltage level. Furthermore, the transmission signal strength can also be recorded using the power detector 11 during normal operation, i.e., after completion of the calibration process in the sixth step S6. If the transmission signal strength exceeds a maximum permissible transmission signal strength, the attenuation factor determined during the calibration process can also be changed, in particular increased.

[0133] Fig. 5 shows a further embodiment of a transmission system 1 according to the invention. This is essentially like the one in Fig. 1 The transmission system 1 shown in the figure is designed. Therefore, the corresponding explanations for Fig. 1 In contrast to the Fig. 1 In the embodiment shown, the antenna unit 4 comprises the antenna 7. The antenna-side signal interface 6 can in this case be a signal interface of a so-called front-end module 22, which comprises the transmission amplifier device 10 as well as the power detector 11 and the temperature sensor 12.

[0134] Furthermore, the antenna unit 4 does not include the attenuator device 9 arranged between the device-side interface 5 and the transmission amplifier device 10. It is also shown that the transmission amplifier device 10 is signal-connected to the control device 8 via an additional control line 21 for adjusting the gain. The transmission amplifier device 10 is thus an amplifier device with an adjustable gain factor and forms the Fig. 1 Device for adjusting the signal strength formed by the damper device 9.

[0135] The adjustment of the gain level and thus the gain factor of the transmitting amplifier device 10 can be achieved, for example, by changing the operating point of the amplifier 10. This can be done by changing the voltage level of a voltage signal transmitted via the control line 21. A damping device 9 as in the Fig. 1 The embodiment shown can therefore be omitted. 1Transmitting system 2Signal provision unit 3Coaxial cable 4Antenna unit 5Device-side signal interface 6Antenna-side signal interface 7Antenna 8Control device 9Attenuator device 10Amplifier device 11Power detector 12Temperature sensor 13Further amplifier device 14Switching device 15Resistance-side signal interface 16Equivalent resistor 17Further switching device 18Signal decoupling device 19Signal level detector 20Comparator 21Control line 22Integrated circuit / front-end module S1First step S2Second step S3Third step S4Fourth step S5Fifth step S6Sixth step

Claims

1. Method for operating an antenna unit (4), wherein the antenna unit (4) comprises an on-antenna signal interface (6) and an on-device signal interface (5), a control device (8), at least one device for adjusting a signal strength of a transmission signal and at least one device for detecting a signal strength of the transmission signal, wherein a calibration process involves a calibration signal being received via the on-device signal interface (5), wherein the signal strength of the calibration signal is determined, wherein the determined signal strength is compared with a reference signal strength, wherein a gain factor of the at least one device for adjusting the signal strength is set such that the difference between the reference signal strength and a signal strength of the amplified calibration signal is minimized, wherein the antenna unit (4) is operated with the gain factor set in this manner following completion of the calibration process, wherein the antenna unit (4) comprises at least one transmission signal branch, wherein during the calibration process the calibration signal is not transmitted to an antenna (7), characterized in that the device for detecting a signal strength is arranged in the at least one transmission signal branch, wherein the transmission signal branch serves to transmit a transmission signal from the on-device signal interface to the on-antenna signal interface.

2. Method according to claim 1, characterized in that the calibration signal is generated by a signal providing unit (2) and transmitted via a signal connection means (3) through the on-device signal interface (5) to the antenna unit (4).

3. Method according to claim 2, characterized in that the signal providing unit (2) generates the calibration signal at the maximum signal strength that can be generated or at a signal strength which corresponds to a predetermined proportion of the maximum signal strength.

4. Method according to claim 3, characterized in that the reference signal strength is determined such that the ratio of reference signal strength to the predetermined maximum transmission signal strength is equal to the ratio of the signal strength of the signal generated by the signal providing unit (2) to the maximum signal strength that can be generated.

5. Method according to any one of the preceding claims, characterized in that a calibration process is performed after each time the antenna unit (4) is switched on or activated.

6. Method according to any one of the preceding claims, characterized in that the device for adjusting the signal strength is a damper device (9) or an amplifier device (10).

7. Method according to any one of the preceding claims, characterized in that the device for adjusting the signal strength is capable of adjusting both a signal strength of a transmission signal and a signal strength of a reception signal.

8. Method according to any one of the preceding claims, characterized in that a temperature or a temperature variation in the antenna unit (4) is determined, wherein the gain factor of the device for adjusting the signal strength is varied depending on the temperature or the temperature variation.

9. Method according to any one of the preceding claims, characterized in that a supply voltage of the antenna unit (4) is determined, wherein the gain factor of the device for adjusting the signal strength is changed depending on the supply voltage.

10. Method according to any one of the preceding claims, characterized in that a transmission mode is activated by the antenna unit (4), wherein the calibration process is carried out in the transmission mode.

11. Method according to any one of the preceding claims, characterized in that the gain factor at the beginning of the calibration process is determined depending on at least one gain factor that was determined in a previous calibration process.

12. Method according to any one of the preceding claims, characterized in that the control device (8) detects an error state when the minimized difference is greater than a predetermined threshold value.

13. Method according to any one of the preceding claims, characterized in that a signal strength of a transmission signal is determined, wherein the gain factor determined in the previous calibration process is changed depending on the signal strength.

14. Self-calibrating antenna unit, wherein the antenna unit (4) comprises an on-antenna signal interface (6) and an on-device signal interface (5), a control device (8), at least one device for adjusting a signal strength of a transmission signal and at least one device for detecting a signal strength of the transmission signal, wherein a calibration process involves a calibration signal being receivable via the on-device signal interface (5), wherein the signal strength of the calibration signal is determinable, wherein the determined signal strength is comparable with a reference signal strength, wherein a gain factor of the at least one device for adjusting the signal strength is adjustable such that the difference between the reference signal strength and a signal strength of the amplified calibration signal is minimized, wherein the antenna unit (4) is operable with the gain factor set in this manner following completion of the calibration process, wherein the antenna unit (4) comprises at least one transmission signal branch, wherein during the calibration process the calibration signal is not transmitted to an antenna (7), characterized in that the device for detecting a signal strength is arranged in the at least one transmission signal branch, wherein the transmission signal branch serves to transmit a transmission signal from the on-device signal interface to the on-antenna signal interface.

15. Transmission system, comprising a self-calibrating antenna unit (4) according to claim 14 and a signal providing unit (2), wherein the antenna unit (4) and the signal providing unit (2) are connected via a signal connection means.