Method and receiver

Abstract

The invention relates to a method for receiving and analyzing received signals. The method is characterized by the steps of: receiving each received signal by means of a respective receiving antenna of at least two receiving antennas (A); allocating a respective receiving chain of at least two receiving chains (EK) to each receiving antenna of the receiving antennas and allowing a signal path between each receiving antenna of the receiving antennas and the receiving chain allocated to the respective receiving antenna by switching a selection circuit (SS); and ascertaining a phase difference between the received signals.

Description

[0001]02931-24 He / FeN Friedrich-Alexander-University Erlangen-Nuremberg Erlangen ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Method and receiver ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The present invention relates to a method for receiving and evaluating received signals. As shown in Fig. 5, systems known from the prior art for locating a transmitter S, which are based on the evaluation of directional information, typically comprise a plurality of receiving devices E, each with a plurality of receiving antennas. In Fig. 5, the receiving devices E each have six receiving antennas and the transmitter S has one transmitting antenna. Depending on the application, one receiving device with a plurality of receiving antennas may be sufficient for locating a transmitter. The information about the direction of the received signal is contained in the relative phases or the phase differences between the receiving antennas.The accuracy of the location depends in particular on the size of the receiver aperture spanned by the receiving antennas. Various concepts exist for evaluating the relative phase information or the phase difference, such as angle estimation or the Holographic Extended Kalman Filter (HEKF). The emission and immission of antennas exhibit polarization-selective behavior, i.e., behavior that differs depending on the polarization type of the transmitted or received electromagnetic waves or signals, which is described by the orientation of the electric field. Different, intentionally implemented, polarization types are known. Typical polarization types are linear polarization (horizontal or vertical) and circular polarization (left- or right-handed). The polarization type can change, e.g., due to reflection from objects.All other polarization types can be represented by a combination of linear polarization and / or circular polarization. If the polarization type of a transmitter or transmitting antenna is orthogonal to the polarization type of a receiver or receiving antenna, e.g., horizontal and vertical, no signal or received signal can be transmitted via line of sight (LOS). The location of the transmitter by the receiver is then severely hampered or even impossible. For unknown transmitters or transmitting antennas, receivers and / or receiving antennas are necessary for location purposes, which can evaluate at least two different polarization types. Receivers are known in which each receiving antenna has a complete receive chain for evaluating or processing the received signal, including amplifiers, mixers, analog-to-digital converters, etc.These are mostly used in communication systems or imaging radar systems. Typically, only one type of polarization is evaluated at each receiving antenna. This achieves a high degree of flexibility, which also enables use in communication processes with multiple overlapping transmitters or with "multiple input multiple output" (MIMO). The relative phases or phase differences of the received signals can be determined in a communication system, for example, during channel estimation or after data demodulation. The evaluation of two types of polarization at each receiving antenna of a receiver is carried out according to the state of the art using two receive chains per receive antenna, which causes very high costs and effort, which is disadvantageous for a localization system. A prior art receiver with a plurality of Nant receive antennas A is sketched in Fig. 6. In Fig.6, each receiving antenna A has two receiving chains EK, one for each type of polarization, pole 1 and pole 2. At each receiving antenna A, all intended polarization directions are thus observed and evaluated, each with its own receiving chain EK. In Fig. 6, only the first receiving antenna A and the last receiving antenna A of the receiver are shown. As indicated by the three dots between the receiving antennas A and the receiving chains EK, the receiver has several receiving antennas A and two receiving chains EK per receiving antenna A. The receiver also has a reference unit R. A reference signal originating from the reference unit R is used to generate baseband signals from the received signals within the receiving chains EK. The receiver also has a processing unit V. The Bluetooth standard 5.1 has been in existence since 2019 and enables the estimation of the angles of an incoming plane electromagnetic wave orthe "angle of arrival" (AOA). For this purpose, the Constant Tone Extension (CTE) is appended to the Bluetooth packets sent by a transmitter S, e.g. a smartphone, which each have a header H, a payload P, and a cyclic redundancy check (CRC), as shown in Fig. 7. The CTE represents a monofrequency signal which has the purpose of enabling the low-effort estimation of the relative phases or phase differences and is received at the three receive antennas A. To determine the relative phases or phase differences, the received signal within the CTE is compared at different times, as outlined in Fig. 7 by the dashed lines and boxes. In order to determine the relative phases or phase differences between the receiving antennas A using the CTE, AOA-based localization systems are known from the state of the art, which comprise receivers as shown in Fig.8. In the receiver shown in Fig. 8, during reception of the CTE by the selection circuit SS, the received signal at the different receiving antennas A is evaluated using exactly one receiving chain EK. The selection circuit SS selects the respective receiving antenna A or the respective polarization type Pole 1, Pole 2, etc. This concept only works in localization systems in which only one transmitter transmits at a time, i.e., Single-Input-Multiple-Output (SIMO) conditions exist. SIMO is the standard mode in the Bluetooth standard and therefore does not represent an additional restriction. As can be seen in Fig. 7 by the dashed lines and boxes, due to the only exactly one receiving chain of the receiver from Fig. 8 within the CTE, a comparison of the phases received at different receiving antennas A is only possible at different times.This implies the assumption of a monofrequency transmission signal in which the phase is as stable as possible over time. This, in turn, requires stable and thus expensive transmit and receive oscillators with low phase noise, which contradicts the goal of the Bluetooth standard of enabling a simple, efficient, and low-complexity transmission method. A widespread implementation in everyday life for the localization of smartphones is therefore difficult to achieve. The hardware requirements increase again if two types of polarization are to be received at each receiving antenna. As can also be seen in Fig. 7, the CTE is located after the CRC block. The CRC block is used within the Bluetooth data packet to verify the success of the data transmission. This makes it possible to check whether the transmission of the Bluetooth packet was disrupted by other transmission signals, e.g., other Bluetooth transmitters.Since the CTE is a monofrequency signal due to the evaluation method, there is no verifiable data modulation and, after the CRC, it is transmitted without any protection mechanism. Therefore, reliable use in this form is not possible in complex scenarios with multiple transmitters, as these would interfere with each other unnoticed during measurements. In order to correctly demodulate a Bluetooth data packet, the received signal in Fig. 7 is continuously evaluated along a receive chain. Since the receiver used for this purpose in Fig. 8 only has exactly one receive chain, it is not possible to verify the polarization type with which the transmitter or transmitting antenna is emitting its transmission signal by evaluating different polarization types within the Bluetooth data packet.Against this background, the object of the present invention is to provide a method and a receiver that are improved compared to the prior art. This object is achieved by the method having the features of independent claim 1 and the subject matter of independent claim 10. Advantageous developments of the invention are the subject matter of the dependent claims. Accordingly, the invention provides that the method comprises the steps of: - receiving a respective received signal by one of at least two receiving antennas; - assigning one of at least two receiving chains to one of the receiving antennas and enabling a signal path between one of the receiving antennas and the receiving chain assigned to the respective receiving antenna by switching a selection circuit; - determining a phase difference between the received signals.The received signals preferably comprise or consist of electromagnetic waves. Before the phase difference is determined, each received signal is preferably processed by the respective receiving chain. One or more phase differences can be determined. Determining the phase difference can comprise calculating and / or determining the phase difference. It is preferably provided that at least two polarization types of the respective received signal are or can be received at at least one of the receiving antennas. It is preferably provided that, to determine the phase difference, the received signals are compared with one another exclusively at the same times. It is preferably provided that no absolute phases are determined during the entire method.It is preferably provided that the phase difference is determined by forming the difference between absolute phases of the received signals or by offsetting one or more difference formations of absolute phases of the received signals. It is preferably provided that the received signals, in particular each, have a modulated signal within a data packet, wherein, in particular each, the modulated signal is used to determine the phase difference, wherein the modulation of the received signals is preferably the same for each receiving antenna. Preferably, the modulation of the received signals is the same for both or all receiving antennas. It is preferably provided that the phase difference between the received signals is determined by, in particular direct, mixing with a common reference signal, low-pass filtering, sampling, calculating the cross-correlation and / or by means of argument formation.Preferably, the cross-white correlation is performed by multiplying the sampled values ​​of the received signal from one receiving antenna by the complex conjugate sampled values ​​of the received signal from another receiving antenna, followed by summing the results of the multiplications from different points in time. Preferably, the argument is formed by extracting the phase from a complex number, in particular a result of the cross-wise correlation. Preferably, it is provided that the respective received signal is used with a polarization type at which the received power of the respective received signal is maximum. Preferably, it is provided that the received signals have the same polarization type. Preferably, it is provided that the received signals from different receiving antennas are evaluated with the same polarization type.Preferably, the determined phase difference is used to locate a transmitter, in particular using a HEKF. The terms "location" and "localization" are preferably used synonymously herein. The invention also relates to a receiver for receiving and evaluating received signals, having at least two receiving antennas and a selection circuit, characterized in that the system has at least or exactly two receiving chains, wherein the selection circuit is connected to the receiving antennas and the receiving chains and is designed and / or can be switched in such a way as to enable and / or interrupt signal paths between one, several or each of the receiving antennas and one, several or each of the receiving chains. Preferably, the receiver is designed and / or arranged to extract phase differences from spatially distributed received signals.Preferably, phase differences between the received signals from multiple receiving antennas are extracted. Preferably, a transmitter emits a transmitted signal, for example via a transmitted antenna, which is received as a received signal by a receiver having multiple receiving antennas, each at a receiving antenna. Due to the change in the transmitted signal due to attenuation, etc., each receiving antenna preferably receives its own received signal resulting from the transmitted signal. The transmitter and the receiver preferably form a system, preferably a single-input-multiple-output (SIMO) system. It can be provided that the receiving antennas of the receiver are spatially distributed. The receiver can also be a receiver structure, in particular with several, for example, receiving devices or sub-receivers. For example, the receiving antennas can be arranged in different components, in particular housings.However, it is also conceivable that the receiving antennas are all arranged in one component, in particular in one housing, e.g. in a receiving device. It is preferably provided that the receiver has means designed to carry out a method according to the invention. It is preferably provided that a receiving antenna is designed to be able to receive received signals with different polarization types. It is preferably provided that the selection circuit has a multiplexer circuit and / or one or more switches. It is preferably provided that the receiver has a plurality of receiving antennas, wherein the receiver has fewer receiving chains than receiving antennas. It is preferably provided that the receiver has fewer receiving chains than the sum of all evaluable polarization types of all receiving antennas of the receiver.The receiver preferably enables localization of the transmitter, preferably by evaluating relative phases or phase differences between the received signals of the individual receiving antennas of one or more receiving devices. The receiver is preferably designed as a phase difference of arrival (PDOA) receiver. The method preferably uses a PDOA principle. The receiver is preferably designed as a PDOA receiver structure and is preferably part of a high-performance, inexpensive, and practical SIMO indoor localization system. The receiver preferably has as few receive chains as possible, since these represent the main cost factor. The phase differences are preferably determined in such a way that the evaluated receive signal can be checked for any errors and / or overlays using the communication data.Preferably, at least two polarization types can be evaluated at each receiving antenna and / or the best or most suitable polarization type for determining the phase differences can be determined. Preferably, the determination of the phase differences is not dependent on the hardware quality of the transmitter, in particular the oscillator stability and the antenna polarization. Preferably, the receiver is designed as a SIMO-PDOA receiver and / or for determining phase differences for a localization system. The receiver is preferably calibrated. Preferably, the receiver has at least two receiving antennas, each of which can receive signals of at least one polarization type, a selection circuit, and at least two receiving chains.It is preferably provided that the phase differences between the received signals can be determined by forwarding the received signals to the receiving chains by means of the selection circuit. It is preferably provided that at least two types of polarization are and / or can be received at at least one receiving antenna. It is preferably provided that the phase differences between the received signals can be determined by all receiving antennas of the receiver. It is preferably provided that, to determine the phase differences, the received signals are compared with one another exclusively at the same times. It is preferably provided that the phase differences are determined without determining absolute phases. It is preferably provided that the data packet is demodulated and checked for data correctness.Preferably, the phase differences between the received signals are calculated by cross-correlation. Preferably, the correlation gain of the cross-correlation is used to determine the phase differences under poor measurement conditions. Preferably, the phase differences between the received signals are determined by mixing with a common reference signal, low-pass filtering, sampling, calculating the cross-correlation and forming its arguments, in particular in accordance with Fig. 3. Preferably, the phase differences between the received signals are determined by directly mixing the, in particular high-frequency, received signals. Preferably, the receive chains are used to check which type of polarization is best for receiving the received signal.Preferably, the reception chains evaluate the reception signals of all polarization types at a reception antenna at the beginning of a data packet and thereby determine the polarization type that is best suited for determining the phase differences. Preferably, the reception chains evaluate the reception signals of all polarization types at a reception antenna at the beginning of a data packet and thereby determine the polarization type for which the reception power is highest. Preferably, the receiver has fewer reception chains than the sum of all evaluable polarization types of all reception antennas. Preferably, the phase differences of reception signals received with the same polarization type are determined.Preferably, the determined phase differences of at least one receiver are used to locate a transmitter using a HEKF. Preferably, the receiver is used within a communication standard, preferably the Bluetooth standard, in particular Bluetooth 4.0 or higher. The received signals are preferably designed according to a communication standard, preferably the Bluetooth standard, in particular Bluetooth 4.0 or higher. In 2019, Bluetooth 5.1 introduced CTE, which has, among other things, the disadvantages mentioned above. Since the method preferably works with modulated signals, a transmitter can preferably be located using transmitted or received signals of all Bluetooth standards. The Bluetooth standard preferably has Bluetooth advertising, which is available from Bluetooth 4.0 onwards.Since this was introduced in 2009, almost all Bluetooth-enabled transmitters in widespread use today can preferably be located. At this point, it should be noted that the terms "a" and "an" do not necessarily refer to exactly one of the elements, although this represents a possible embodiment, but can also refer to a plurality of the elements. Likewise, the use of the plural also includes the presence of the element in question in the singular and, conversely, the singular also encompasses several of the elements in question. Furthermore, all features of the invention described herein can be combined with one another as desired or claimed in isolation from one another. Further advantages, features and effects of the present invention will become apparent from the following description of preferred embodiments with reference to the figures, in which identical or similar components are designated by the same reference numerals.: a sketch of an embodiment of a receiver according to the invention. Fig. 2: a sketch of an embodiment of a receiver according to the invention. Fig. 3: a sketch of an embodiment of a reception chain and a processing unit of a receiver according to the invention. Fig. 4: a sketch of an embodiment of a system according to the invention for locating a transmitter using the Bluetooth standard. Fig. 5: a sketch of an embodiment of a system known from the prior art for locating a transmitter. Fig. 6: a sketch of an embodiment of a receiver known from the prior art. Fig. 7: a sketch of a system known from the prior art for locating a transmitter using the Bluetooth 5.1 standard. Fig. 8: a sketch of an embodiment of a system known from the prior art for locating a transmitter. The receiver sketched in Fig. 1 has a plurality of receiving antennas A with the number ^^^^.ant , several receiving chains EK with the number ^^^^ ch , as indicated by the points between the receiving antennas A and the receiving chains EK in Fig.1, a selection circuit SS, a reference unit R and a processing unit V. At the ^^^^ ant -th receiving antenna A, ^^^^pol,^^^^antPolarization types are sent by the selection circuit SS to the ^^^^ chReception chains EK. Thus, from each reception antenna A, several polarization types are passed on to the selection circuit SS and / or to the reception chains EK, as indicated in Fig. 1 by the dots between the connecting lines from the reception antennas A to the selection circuit SS. The selection circuit SS is designed such that a selection can be made as to which, in particular high-frequency, reception signal is passed on to which reception chain EK. The selection circuit SS can be designed such that the reception signal of each polarization type from each reception antenna A can be passed on to each reception chain EK, or each, one or more selected reception chains EK can only receive the reception signals from selected polarization types of selected reception antennas A through the selection circuit SS. Passing on or receiving are preferably synonyms for assigning.The selection circuit SS can, for example, comprise multiplexer circuits and / or switches. The selection circuit SS can switch between the receiving antennas A and the receiving chains EK during the reception of a received signal, e.g., in the form of a data packet. Fig. 2 shows a possible embodiment of the selection circuit SS with two evaluable polarization types, pole 1 and pole 2, for each receiving antenna A, wherein the embodiment shown in Fig. 2 comprises a plurality of receiving antennas A with the number ^^^^. antand two receive chains EK. With the selection circuit SS shown in Fig. 2, it is possible to connect the receive signals for the different polarization types of all receive antennas A with the existing receive chains EK as desired and thus to determine their phase differences. The receive chains EK use the, in particular high-frequency, reference signal from the reference unit R to create baseband signals from the, in particular high-frequency, receive signals, which are then further processed. The reference unit R can, for example, have oscillator circuits and / or phase-locked loops and / or the reference signal can be used for coherent mixing and / or sampling. The receive signal of one polarization type at a receive antenna A can also be used as a reference signal.In this case, the selection circuit SS forwards the received signal of one polarization type of a receiving antenna A as a reference signal. One, several or all receiving chains EK can have, among other things, mixers, adjustable and non-adjustable amplifiers, filters, attenuators, limiters, equalizers, elements for signal conditioning and / or analog-to-digital converters or analog-to-digital converters (ADCs). The processing unit V can have further means or elements for signal conditioning, demodulation and / or for determining the phase differences. The phase differences are determined in the processing unit V. When determining the phase differences with the help of the receiver, a SIMO transmission with a transmitter or a transmitting antenna is assumed, which is at the position ^^^^. TX the transmission signal ^^^^ TX (^^^^), which can be represented by the formula, where ^^^^ Daten(^^^^) the typically narrowband data signal in the baseband, ^^^^0 = 2^^^^^^^^0^ the angular frequency of the transmitter or the transmitting antenna and ^^^^ TX represents the unknown transmission phase of the transmission signal. The transmission signal is denoted by ^^^^ ^^^^ant time-delayed and due to damping by the factor ^^^^^^^^ant,^^^^pole-scaled at the ^^^^ ant -th receiving antenna A at ^^^^ ^^^^ant as a received signal ^^^^RX,RF,^^^^ant,^^^^pol(^^^^), which is calculated using the formula can be displayed, where both the attenuation on the propagation path to ^^^^ ant -th receiving antenna A as well as the polarization-dependent attenuation at the ^^^^ ant -th receiving antenna A. At the receiver, within each receiving chain EK, to which the respective received signal is passed on by the selection circuit SS, into the baseband to ^^^^RX,BB,^^^^ant,^^^^pol ( ^^^^ ) , which is calculated using the following formula can be represented, mixed, where ^^^^ RX represents the unknown phase of the reference signal. Subsequently, in processing block V, the phase difference between the respective received signal of the ^^^^ ant -th and ^^^^ a ′ n t -th receiving antenna A, which is located between the times ^^^^ Start and ^^^^ End by the selection circuit SS to one of two receiving chains EK. Each receiving antenna or each received signal is preferably assigned to a different receiving chain or forwarded to a different receiving chain. One possibility for determining the phase difference Evaluation of the argument of the signal cross-correlation between the respective received signal of the ^^^^ ant -th and ^^^^ a ′ n t -th receiving antenna A according to the formula where ^^^^data�^^^^ − ^^^^ ^^^^ant� ≈ is assumed, since the bandwidth of ^^^^data ( ^^^^ ) is small relative to the transmit frequency. Determining the phase differences can be replaced by mixing with a monofrequency reference signal and subsequent correlation, by directly mixing two received signals with each other and then applying a low-pass filter and / or averaging. The correct phase difference ∆^^^^ ^^^^ ′is independent of the polarization-dependent attenuations ^^^^^^^^ant,^^^^pol and ^^^^^^^^ant′,^^^^pol′. Therefore, the receiver according to the invention is preferably suitable for evaluating or determining the phase differences with the received signals of the most suitable polarization type using the selection circuit SS. This is typically the polarization type with the greatest received power. Fig. 3 shows a preferred embodiment of the two receiving chains EK and the processing unit V for determining the phase differences of two received signals. nale The received signals are first mixed into the baseband with the typically monofrequency reference signal RF. The optional filter FLT removes unwanted signal components. After sampling using the ADCs, the baseband signals are correlated with each other in the correlator K, and the phase difference ∆^^^^^^^^ant,^^^^′ a is calculated from the correlation result by forming the argument in the ARG block. ntdetermined. The structure shown in Fig. 3 differs significantly from implementations known from the prior art, in particular because any estimation of the absolute phases of the received signals is bypassed and the same reference signal is used for mixing on all receive channels. The measured phase of a received signal from a receive antenna after the mixing process is preferably referred to as the absolute phase. Due to the mixing process, this phase only exists implicitly relative to the phase of the reference signal. If several receive signals from several receive antennas are mixed with the same reference signal, the difference phases between the two or more receive signals can then be determined, preferably by subtraction. The estimation of the absolute phases of the received signals represents a major hurdle, since the received signals are modulated and constant phases can only be assumed for very short time intervals.This in turn implies that in the short time intervals during which the absolute phases are determined, the signal-to-noise ratio is poor, and thus the quality of their estimation is massively degraded. Since the calculation of phases from complex-valued data is again a non-linear operation, subsequent processing, for example, the calculation of differential phases, is severely impaired. The negative effect is most pronounced under poor measurement conditions, typically with a large measurement distance between transmitter and receiver. Furthermore, the implementation of large receiver apertures, which is necessary for precise positioning, is significantly hampered, since the received signals from the external receiving antennas are attenuated by the signal routing, thus further deteriorating the signal-to-noise ratio. In contrast, the correlator K in Fig.3 Due to the freely adjustable correlation length and the resulting correlation gain, the reliable determination of phase differences even with poor signal-to-noise ratios is possible. Since the phase differences determined in this way contain implicitly correlated measurement errors, this is particularly suitable for evaluation using a HEKF. The receiver preferably has at least two receive chains. Since at least one receive signal should be continuously evaluated in one receive chain for low-complexity data demodulation, at least the second receive chain can be used to switch between the receive antennas and polarization types and determine the phase differences. More than two receive chains are necessary if the receive signal is too short to pass through all necessary receive antennas and polarization types with just one receive chain.Thus, compared to prior art receivers, which use a separate receive chain for each receive antenna and polarization type, the effort and costs are significantly reduced. Since the phase differences in the receiver are preferably determined from the received signal of a data packet, which is simultaneously demodulated and verified using the demodulated data, the phase differences are implicitly protected in the case of a correctly decoded data packet. This represents a significant advantage of a receiver according to the invention over the CTE concept used in Bluetooth 5.1, as outlined in Fig. 4. The comparison for determining the phase differences takes place without the use of a CTE, but directly using the Bluetooth data packet, as indicated by the dashed lines in Fig. 4.Each Bluetooth data packet comprises a header (H), a payload (P), and a cyclic redundancy check (CRC), and is received at three receive antennas (A), as shown in Fig. 4. To determine the phase differences, the received signal is viewed simultaneously on two channels within the Bluetooth data packet, which is why no constant tone extension (CTE) is evaluated. Preferably, the ^^^^. ant -th receiving antenna A, ^^^^pol,^^^^ant polarization types can be evaluated by the selection circuit SS. In order to determine in which polarization type the receiver or the receiving antenna A best receives the received signal and also to be able to evaluate it, it is advisable to conduct the same ^^^^pol,^^^^ant = ^^^^pol polarization types at each receiving antenna A. This is made possible by the implementation of ^^^^ polReceive chains compare all polarization types at the beginning of a data packet, preferably at one receive antenna A, and then perform data demodulation with the best polarization type, typically the polarization type with the highest reception power, of this receive antenna A, while the other receive chains EK determine the phase differences to the other receive antennas A, preferably in the same polarization type. For cost reasons, the use of two orthogonal polarization directions, for example, linear vertical and linear horizontal, is recommended. Preferably, one, several, or all receive antennas A are patch, dipole, Yagi, slot, and / or horn antennas, whereby a receive antenna A can also have a different antenna shape than another receive antenna A. The evaluation of the phase differences within the CTE of the Bluetooth standard 5.1 is based on the observation of the phases at different receiving antennas A at different times, as shown in Fig. 7. This implies the assumption of stable frequency reference signals with little phase noise, so that a phase relationship that is as stable as possible over time exists. As outlined in Fig. 4 using the Bluetooth standard as an example, the receiver preferably evaluates the phase differences within the data packet at the same times. Thus, frequency variations and phase noise of the transmitter and the reference signal in the receiver have the same effect in the reception chains used, which does not interfere with the determination of the phase differences.

Claims

02931-24 He / FeN Friedrich-Alexander-University Erlangen-Nuremberg Erlangen ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Method and receiver ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Patent claims 1. Method for receiving and evaluating received signals, characterized by the steps: - receiving a respective received signal by one of at least two receiving antennas; - assigning one of at least two receiving chains to one of the receiving antennas and enabling a signal path between one of the receiving antennas and the receiving chain assigned to the respective receiving antenna by switching a selection circuit; - determining a phase difference between the received signals.

2. Method according to claim 1, characterized in that at least two types of polarization of the respective received signal are received at at least one of the receiving antennas. - 2 - 3. Method according to claim 1 or 2, characterized in that to determine the phase difference, the received signals are compared with each other exclusively at the same times.

4. Method according to one of the preceding claims, characterized in that no absolute phases are determined during the entire method.

5. Method according to one of claims 1 to 3, characterized in that the phase difference is determined by calculating the difference between absolute phases of the received signals or by calculating one or more difference between absolute phases of the received signals. 6.Method according to one of the preceding claims, characterized in that the received signals, in particular each, have a modulated signal within a data packet, wherein, in particular each, the modulated signal is used to determine the phase difference, wherein the modulation of the received signals is preferably the same for each receiving antenna.

7. Method according to one of the preceding claims, characterized in that the phase difference between the received signals is determined by, in particular direct, mixing with a common reference signal, low-pass filtering, sampling, calculating the cross-correlation and / or by means of argument formation.

8. Method according to one of the preceding claims, characterized in that the respective received signal is used with a polarization type at which the received power of the respective received signal is maximum. - 3 - 9. Method according to one of the preceding claims, characterized in that the received signals from different receiving antennas are evaluated with the same polarization type.

10. Method according to one of the preceding claims, characterized in that the determined phase difference, in particular using a HEKF, is used to locate a transmitter.

11. Receiver for receiving and evaluating received signals with at least two receiving antennas and a selection circuit, characterized in that the system has at least or exactly two receiving chains, wherein the selection circuit is connected to the receiving antennas and the receiving chains and is designed and / or can be switched in such a way as to enable and / or interrupt signal paths between one, several, or each of the receiving antennas and one, several, or each of the receiving chains.Receiver according to claim 11, characterized in that the receiver has means configured to carry out a method according to one of claims 1 to 9.

13. Receiver according to claim 11 or 12, characterized in that at least one receiving antenna is configured to be able to receive received signals with different polarization types.

14. Receiver according to one of claims 11 to 13, characterized in that the selection circuit comprises a multiplexer circuit and / or a switch. - 4 - 15. Receiver according to one of claims 11 to 14, characterized in that the receiver has fewer receive chains than the sum of all evaluable polarization types of all receive antennas of the receiver.

16. Receiver according to one of claims 11 to 15, characterized in that the receiver has a plurality of receive antennas, wherein the receiver has fewer receive chains than receive antennas.

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