Wireless radio-frequency receiver and a method for beam analysis

Abstract

A wireless radio-frequency receiver (500) comprising multiple antenna elements (511-514) for receiving a radio signal, an analogue beamforming radio circuit (520), a digital baseband processor (530), a first signal path (531) and a second signal path (532) from the multiple antenna elements (511-514) to the digital baseband processor (530), wherein the first signal path comprises the analogue beamforming radio circuit (520) and wherein the second signal path (532), which is at least partly parallel to the first signal path (531), comprises an analogue crossbar array (540), wherein a respective antenna element (511-514) is connected to a corresponding input of the analogue crossbar array (540), the analogue crossbar array (540) being configured to provide output signals that is the result of a matrix multiplication of input signals of the analogue crossbar array (540).

Description

[0001]WIRELESS RADIO-FREQUENCY RECEIVER AND A METHOD FOR BEAM ANALYSIS TECHNICAL FIELD The embodiments herein relate to a wireless radio-frequency receiver and a method for beam analysis. A corresponding computer program and a computer program carrier are also disclosed. BACKGROUND Beamforming allows for achieving spatial domain multiplexing for modern mobile communication systems. Spatial domain multiplexing is a key feature in Fifth Generation (5G) and upcoming 6G communication systems and beyond complying with third generation partnership program (3GPP). To achieve a desired beamforming there are usually a need for more than one antenna and corresponding radio chain where the antennas have a known physical arrangement and orientation. Figure 1 illustrates an example of a simplified block diagram of a wireless Analogue Beamforming (ABF) receiver 100 comprising an antenna array comprising multiple antenna elements 101-104. The ABF receiver 100 further comprises a respective Low-Noise Amplifier (LNA) 111-114 and a respective phase tuner 121-124 per antenna element 101-104. After that, by adding beam weighting factors, a variation of a signal at each antenna element 121-124 is applied to achieve different directive beams that may be sequentially employed. Wireless devices are adopting beamforming capabilities to have enhanced directivity and corresponding higher data rates. Generally, beamforming is useful in a dynamic environment, e.g., where one or both communicating wireless devices or scatterers of wireless signals are moving. Beamforming may be employed for both sending and receiving a signal. While sending a signal, beamforming will help direct the signal towards a particular receiver. Similarly, when receiving a signal, beamforming will provide a high sensitivity in receiving the signal originating from a transceiver of interest. Figure 2 illustrates a base station 201 and UE 202, which both have beamforming capability to different directions. Analogue beamforming radio corresponds to having only one analogue-to-digital (ADC) converter in a radio chain. Thus, all the signals from the different antenna elements are summed up. A beam direction may be set by phase and gain blocks. At a time, only one beam may be set. The set beam may be a pencil beam, such as the beams of the base station 201 in Figure 2, or a wide beam, such as the beams of the UE 202 in Figure 2. In case of a wide beam, the receiver will not have any knowledge of direction except the set beam direction / beam weighting factor. A first generation of a commercial multi-antenna system radio is based on analogue beamforming. Analogue beamforming multi-antenna systems are easier to design and implement than digital beamforming multi-antenna systems, needs fewer digital resources, and may easily form pencil beams. However, it also reduces the scope of beam recovery when a beam link is failed. When using pencil beamforming with ABF a beam width of a directed signal is usually very narrow. With a small movement of any of the participants in a communication there is a chance that a beam link will be lost. In a scenario of beam link failure, as illustrated in Figure 3, one or both of communicating devices 301, 302 tries to reestablish a communication link by utilizing alternate sets of beams. In one solution of beam link recovery, one of the devices searches a strong beam link by sequentially changing its own beam. This process of searching for a new beam link is time and resource hungry. As an example, if a device is able to create 64 possible beams, it needs to try a percentage of these possible beams to find the correct or desired beam direction to reestablish the beam link. Another possible solution is for an analogue beamforming transceiver to have two active beams all the time. Thus, one beam is used for communication while the other beam will monitor an alternative beam. In case of beam failure of the beam used for communication, the transceiver will easily switch to the next beam link. However, this method needs two active radios and corresponding radio resources. Additionally, for an analogue beamforming transceiver, this method requires several antennas to be dedicated for this monitoring. As a result, overall radio resources and corresponding power / gain decreases while adding a limited advantage. A method for the identification of multiple possible beams may be performed by running 2D Discrete Fourier transform (DFT), such as 2D Fast Fourier Transform (FFT). The inputs to the 2D DFT are then digital signals originating from each antenna element. However, that would require a Digital Beamforming (DBF) transceiver having an ADC for each antenna element, which is resource and power hungry. Furthermore, even though with this method all possible alternate beam links may be identified, it cannot be directly adopted by an analogue beamforming transceiver. SUMMARY There is a need for a solution for efficient beam identification for fast beam recovery in case of a beam failure. In embodiments disclosed herein a wireless radio-frequency receiver, e.g. of a wireless communications device, may be equipped with an advanced antenna system for ABF. Embodiments herein further disclose an arrangement of an analogue crossbar array within the wireless radio-frequency receiver. An analogue crossbar array is a 2-dimensional array that may comprise M×N memristive devices, each of which can be programmed to represent an m-bit binary value. According to a first aspect, the object is achieved by a wireless radio-frequency receiver comprising multiple antenna elements for receiving a radio signal. The wireless radio-frequency receiver further comprises an analogue beamforming radio circuit, a digital baseband processor, a first signal path and a second signal path from the multiple antenna elements to the digital baseband processor. The first signal path comprises the analogue beamforming radio circuit and the second signal path, which is at least partly parallel to the first signal path, comprises an analogue crossbar array. A respective antenna element is connected to a corresponding input of the analogue crossbar array. The analogue crossbar array is configured to provide output signals that is the result of a matrix multiplication of input signals of the analogue crossbar array. According to a second aspect, the object is achieved by a method, performed by a wireless radio frequency receiver, for providing output signals based on received radio signals. The wireless receiver comprises multiple antenna elements for receiving the radio signals. The wireless radio-frequency receiver further comprises an analogue beamforming radio circuit, a digital baseband processor, a first signal path and a second signal path from the multiple antenna elements to the digital baseband processor. The first signal path comprises the analogue beamforming radio circuit and the second signal path, which is at least partly parallel to the first signal path, comprises an analogue crossbar array. A respective antenna element is connected to a corresponding input of the analogue crossbar array. The method comprises providing output signals from the analogue crossbar array by matrix multiplying input signals of the analogue crossbar array. According to a further aspect, the object is achieved by a computer program comprising instructions, which when executed by a processor, causes the processor to perform actions according to any of the aspects above. According to a further aspect, the object is achieved by a carrier comprising the computer program of the aspect above, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium. Since the wireless radio-frequency receiver comprises the second signal path comprising the analogue crossbar array, configured to provide output signals that is the result of a matrix multiplication of input signals of the analogue crossbar array, required signal-processing computations of the received radio signals, such as mathematical transforms, in particular for beamforming, are performed in parallel within the crossbar array which eliminates the need for an ADC for each antenna element branch to perform digital beamforming. By adopting the analogue crossbar array to perform beam identification using the RF signals from the antenna elements, the expected beam link to be selected may be identified very quickly since the required computations are performed in parallel within the crossbar array. The ABF transceiver does not need to try several beams in case of a beam link failure or need to have a split beam to avoid possible beam link failure. Additionally, it will not need an ADC for each antenna element branch. Therefore, the embodiments disclosed herein do not demand more power and resources than prior art solutions. Still, the wireless radio-frequency receiver is able to set / select the next beam link when there is a link failure. That will ensure uninterrupted high-speed communication. BRIEF DESCRIPTION OF THE DRAWINGS In the figures, features that appear in some embodiments are indicated by dashed lines. The various aspects of embodiments disclosed herein, including particular features and advantages thereof, will be readily understood from the following detailed description and the accompanying drawings, in which: Figure 1 is a block diagram schematically illustrating an Analogue Beamforming receiver according to prior art, Figure 2 is a block diagram schematically illustrating a base station and a UE, which both have beamforming capability to different directions, Figure 3 is a block diagram schematically illustrating a scenario of beam link failure in which embodiments herein may be employed, Figure 4a is a block diagram schematically illustrating an electronic device comprising a memristive crossbar array according to prior art, Figure 4b is a block diagram schematically illustrating a memristive crossbar array according to embodiments herein, Figure 5a is a block diagram schematically illustrating a wireless radio-frequency receiver according to some embodiments herein, Figure 5b is a further block diagram schematically illustrating details of the wireless radio-frequency receiver according to some embodiments herein, Figure 5c is a further block diagram schematically illustrating further details of the wireless radio-frequency receiver according to some embodiments herein, Figure 5d is a further block diagram schematically illustrating further details of the wireless radio-frequency receiver according to some embodiments herein, Figure 6 is a further block diagram schematically illustrating clock pulses, Figure 7 is a flow chart illustrating a method according to some embodiments herein, Figure 8 is a block diagram schematically illustrating a network node, Figure 9 is a block diagram schematically illustrating a wireless communications device, and Figure 10 is a block diagram schematically illustrating a wireless communication system. DETAILED DESCRIPTION Embodiments herein relate to beamforming in general and beam link recovery in particular. A formed beam is a function of antenna elements, their relative placement and applied beam weighting factors. The relation may be described with a Fourier transform. From the Euler theorem ^^^^^^^^^^^^ = cos^^^^ + ^^^^ ∙ sin∙ ^^^^ (1)according to Fourier, the relation between beam and space is given by ∞ ^^^^(^^^^) =1 ∙� ^^^^(^^^^) ^^^^−^^^^^^^^^^^^^^^^∙ ^^^^^^^^−∞ ^^^^ represents the beam direction for 1D beam space relative to boresight. X is a Fourier transform of x equivalent to an intensity of radiation for each beam direction. d is a coordinate of a 1D linear / planar antenna array, such as a coordinate of a centre of each antenna where the intensity x is measured. n is a positional number in a planar vector d of the coordinates d. ω is the angular frequency of radiation. The expression of ^^^^ may be translated for discrete samples of data to translate ^^^^ in a first domain to ^^^^ in a^^^^ ^^^^second domain (e.g. DFT), e.g., X is a Fourier-transformed value in the second domain of x in the first domain at m:th index point. For thembeam angular domain, X is the radio signal intensity at ^^^^(m). m is an index for the angle ^^^^ for the discreatemequation. n is an index for positions of linearly distributed spatial coordinates in the first domain, such as positions of antenna elements (more specifically where the signal is measured, such as at the antenna centre) in planar space for the 1D antenna array. k represents the wave number as function of wavelength and factorized with actual distance between two successive points in the linear array. Furthermore, the coefficients, which may be written as ^^^^^^^^ −^^^^2^^^^^^^^^^^^^^^^ / ^^^^ ^^^^ = ^^^^ , are the coefficients of the DFT, which are called twiddle factors.^^^^Using equation (1) and (2), the following is obtained Equation (3) may be represented with m equations, one equation for each point of the angular domain as ) … Alternatively, Equation (3) may be expressed in a matrix format by putting n = 0,1, 2…N-1 and m = 0, 1, 2, …, M-1, e.g., Furthermore, the real and imaginary parts may be separated to obtain With vector and matrix notations, the expression becomes For a 1D array antenna this can be represented in matrix form [^^^^^^^^] = [^^^^^^^^] ∙ [^^^^^^^^^^^^] (4)where [^^^^^^^^^^^^] = [^^^1^ ] + ^^^^ ∙ [^^^2^ ]and where However, according to some aspects of the techniques disclosed herein, the complex part or angle may be ignored even if the input signal is also complex. A complex signal may be expressed as ^^^^^^^^ = ^^^^^^^^ + ^^^^ ∙ ^^^^^^^^xnis a complex signal at n:th index point of the planar antenna array. Inis the in-phase part of the signal xnat the n:th index point. Qnis the quadrature-phase part of the signal xnat the n:th index point. Thus equation (4) may be expressed as Considering only the real part sin(−^^^^) = −sin(^^^^)cos(−^^^^) = cos(^^^^)equation (5) may be further expressed as Thus, two analogue crossbars may be used for performing the real part of the discrete transformation, namely[^^^^^^^^^^^^1]for the in-phase signal[^^^^^^^^]and[^^^^^^^^^^^^2]for the quadrature signal[^^^^^^^^], where A similar equation may be extracted for a 2D antenna array, namely Where ^^^^ and ^^^^ are azimuth and elevation directions respectively and ^^^^ and ^^^^ are planar coordinate positions. As mentioned above, the wireless radio-frequency receiver according to embodiments herein comprises one or more analogue crossbar arrays (implemented, e.g., by memristors). The crossbar arrays according to embodiments herein enable performing massive multiply-accumulate (MAC) operations in parallel. More specifically, the crossbar arrays may compute matrix-vector multiplication (MVM) by calculating a dot-product of the input vector applied to crossbar rows (i.e., word lines) and every column of the crossbar (i.e., bit lines). This reduces the latency and increases throughput. A memristor may also be referred to as a memristive device. A memristor is a tuneable and programmable resistor with memory. The memristor may comprise a dielectric layer sandwiched by two electrodes. A unique feature of memristors is that the conductance depends on historical electrical signals, making them capable of working as non-volatile memory. In addition, memristors may store multibit information with continuously tuneable conductance, in contrast to binary states “0” and “1” in traditional digital storage systems, equipping them with higher bit density. Analogue memristive devices have emerged as a new technology for storing and processing information in analogue domain. These devices make it possible to perform computations in a place where data is stored. This concept is called in-memory computing (or processing in memory), which eliminates the need for moving data from a memory to a processing unit. There are different types of memristive devices, which are differentiated with respect to the used materials, switching principles, device endurance, retention, etc. The main types of memristive devices include phase change memory (PCM), resistive random-access memory (ReRAM), spin-transfer torque magnetic RAM (STT-MRAM), ferroelectric memristive devices (FeRAM). Memristive devices may support a limited bit precision, attributed to the limited number of conductance levels that may be reliably programmed in the device. For example, a PCM device may support around 50 conductance levels, meaning that it may represent around 6 bits. A number of memristor devices may be organized to form an analogue crossbar array. Figure 4a illustrates an electronic device 401, such as a wireless receiver, comprising a memristor crossbar array 410 according to prior art. The memristor crossbar array 410 computes MVM by calculating a dot-product of the input vector applied to crossbar rows (i.e., word lines) and every column of the crossbar (i.e., bit lines). The memristor crossbar array 410 is a two-dimensional array that comprises an M×L array of memristors 411, 412, 421, 422, each of which may be programmed to represent an m-bit binary value. In Figure 4a L = M. Thus, the m-bit binary value of the memristor may be set or programmed by applying a current to the memristor. The binary value may depend on theamplitude of the current. Thus, an ^^^^ × ^^^^ matrix of binary words, G, may be represented by the memristor crossbararray 410 comprising ^^^^ × ^^^^ memristors. The input to the memristor crossbar array 410 is an electronic input signalof multiple samples, such as a vector of ^^^^ analogue voltages, e.g., V. Analogue crossbar arrays comprise parallel conductors, such as metal lines, termed word lines and bit lines, respectively, as electrodes of the memristors. The word lines and bit lines may be perpendicular to each other. The memristors are formed at the intersections of word and bit lines. In embodiments herein input conductors 431 of the analogue crossbar array 410 corresponds to the word lines and output conductors 432 of the analogue crossbar array 410 corresponds to the bit lines. The analogue crossbar array 410 computes MVM by calculating the dot-product of the input vector applied to crossbar rows (i.e., word lines) and every column of the crossbar (i.e., bit lines), all performed in analogue domain using Ohm’s law for multiplication and Kirchhoff’s law for accumulation. In Figure 4a the entries of a matrix G (an M×M matrix) are programmed to the memristive devices 411, 412, 421, 422 of the M×M crossbar array 410 while the input vector V (an M×1 vector) is applied to the crossbar rows. Note that, the vector V corresponds to the actual input vector (Input 1, …, Input M), which may be converted to analogue voltages using one or more Digital to Analogue Converter (DAC) modules 404 illustrated in Figure 4a. As a result, the following MVM may be realized using the illustrated crossbar array 410, =1, … ,^^^^ (8) where an output vector O is the output current of crossbar columns, which is equal to the result of matrix- vector multiplication, i.e., O = G‧V. The output vector O may be converted to the corresponding binary words using one or more ADC modules 405 as shown in Figure 4a. This conversion may be done either separately for each crossbar column (i.e., one ADC for each binary word) or in a time-multiplexed fashion and hence reduce ADC overhead (i.e., multiple bit lines may share one ADC 405). In this disclosure vectors and matrices are represented using capital boldface letters while their entries are shown using normal letters. Thus, when the electronic input signal is digital then the electronic device 401 further comprises the one or more DACs 404 adapted to convert the input signal of multiple samples to corresponding analogue voltages V1, V2, … VM. In other words, when the input signal of the multiple samples is digital, the electronic device 401 may further comprise the DACs 404 configured to convert the digital input signal of the multiple samples to the analogue voltages. There may be one DAC 404 per input sample. In some other embodiments there may be less than one DAC 404 per input sample as one DAC 404 may be shared among several input samples by multiplexing. For example, two input samples may share the same DAC 404. Output signals will be extracted from the bit lines (columns in Figure 4a) of the crossbar array 410. If digital output values of the crossbar array 410 are needed then the outputs of the crossbar array 410 may be converted to digital values. Thus, the electronic device 401 may further comprise the one or more ADCs 405 adapted to convert the output samples, comprising analogue output current, to corresponding digital output values. In other words, the electronic device 401 may further comprise ADCs 405 configured to convert the output from the respective output conductor to a digital signal. If analogue signals are needed in a next block in the processing chain then the ADCs 405 in the electronic device 401 may not be needed. Further, if the analogue outputs are sent to another crossbar array then they may be converted to voltage signals, which may be done by a resistor. In embodiments below it will be assumed that input signals to the analogue crossbar array are in analogue domain and do not need a DAC. Also, some embodiments disclosed herein comprise analogue processing blocks directly after the crossbar array, in which case an analogue output signal from the analogue crossbar array is required. Having considered the computations in equation (1) above, the required mathematical operations within an DFT or Inverse DFT (IDFT) may be performed using a crossbar array. More specifically, the DFT / IDFT computation is converted to a matrix-vector multiplication, which may be mapped to a crossbar array as explained above. Figure 4b shows a memristive-based crossbar array 450 according to embodiments herein. The crossbar array 450 is used to realize an N-point DFT. The crossbar array 450 consists of four sections: Section 1, Section 2, Section 3 and Section 4. Crossbar elements of each section are programmed with the real (ℜ�WN^^^^^^^^�) or imaginary (ℑ�WN^^^^^^^^�) parts of the DFT coefficients as specified in Figure 4b. To perform an N-point DFT, the crossbar elements in Section 1 and Section 2 receive the real part of the input signal (ℜ{^^^^}), while Section 3 and Section 4 receive the imaginary part of the input signal, ℑ{^^^^}. In this way, as mentioned above, all the computations in (4) will be performed using the illustrated crossbar array 450. Finally, the real and imaginary parts of the DFT output samples will be generated through the crossbar columns. For each section of Figure 4b, the number of crossbar rows equals the number of antenna elements. In some embodiments herein the number of crossbar columns of each section equals the number of possible angular points of the received beam. If the direction of the received beam is a multidimensional direction then the number of possible angular points of the received beam can be calculated by multiplying a number of angular points in a first dimension with a number of angular points in a second dimension. For example, if antenna elements of a receiving antenna are arranged in a 2-dimensional pattern a total number of angular points can be calculated by multiplying a number of angular points in an azimuth direction with a number of angular points in an elevation direction. When all coefficients and input samples are real valued, an N-point DFT may be realized using N^2 memristors. In a more general case, e.g., when both the coefficients and the input samples are complex valued, 4N^2 memristors may be needed. In some embodiments herein techniques to reduce the number of memristors for calculating the DFT may be applied. Two Dimensional DFT (2D DFT) The presented crossbar-based DFT may be scaled to a 2-dimensional DFT. The corresponding computation may be expressed as, where ^^^^^^^^,^^^^^^^^ = 0, … ,^^^^ − 1 and ^^^^ = 1, 2, which represents the dimension of the DFT operation. Here,W^^^^N^^^^^^^^^^^^= e-j2π ^^^^^^^^^^^^^^^^ / Nare complex-valued coefficients. Since the multiplication of the two coefficients in equation 9) may be merged, the inner summation corresponding to each output sample, X, may be implemented using a crossbar similar the one shown in Figure 4b. There are two main differences compared to the one-dimensional DFT. The crossbar elements are programmed with different coefficients compared to the one-dimensional DFT. The combined coefficients are obtained from equation (9) (W^^^^ ^^^^ ^^^^ ^^^^N1 1^^^^^^^^2 2). Further, the size of the crossbar array is larger than the one in Figure 4b since it handles NxN samples instead of N samples. Thus, the corresponding computation in equation (9) may be performed using multiple cascaded crossbar arrays to generate the 2D output signal. The values of the crossbar elements are programmed into memristors with the DFT coefficients while the input samples are applied to the crossbar rows. The output signal generated through the crossbar columns will be stable after a certain time, which may be called the read cycle of the crossbar array. Eventually, after a read cycle of the crossbar, the generated signals via the crossbar columns represent the output samples of the DFT / IDFT. Embodiments herein present a solution for beam analysis, such as analysis of beam direction and identification of beam direction, of received signals at antennas for faster beam link recovery by arranging an analogue crossbar array in an analogue beamforming receiver. The receiver may be part of a transceiver. Memristors of the analogue crossbar array may be programmed with a defined set of values which is based on positions of the antenna elements, a desired resolution of beam angle and the wavelength of the carrier frequency of the received signals as set out by the equations derived from equation (1) above. Thus, the crossbar may convert signal strength information for different antenna element positions to signal strength information for different beam directions. This information may be fed back to a processing unit, such as a digital baseband processor, of the analogue beamforming radio receiver. Thus, the digital baseband processor may identify what is the next beam direction for the communication and establish a new beam link. Correspondingly the digital baseband processor may set beam weighting factors with a phase and gain tuner for each antenna element of the analogue beamforming receiver. Embodiments disclosed herein may be used in a live scenario, as well as sequentially. In a live scenario, the digital baseband processor of the device will continuously feed the information about the alternate beam. Thus, it will adopt the next beam link immediately in case of any beam link failure. In case of any beam failure, the processor performs sequential steps to take the input from the analogue crossbar array to identify the next beam and reestablish beam communication. Figure 5a illustrates a block diagram of a wireless radio-frequency receiver 500. The wireless radio- frequency receiver 500 comprises multiple antenna elements 511-514 for receiving a radio signal. Thus, the wireless radio-frequency receiver 500 comprises at least two antenna elements. The multiple antenna elements 511-514 form an antenna array 510. The wireless radio-frequency receiver 500 further comprises an analogue beamforming radio circuit 520, a digital baseband processor 530, a first signal path 531 and a second signal path 532 from the multiple antenna elements 511-514 to the digital baseband processor 530. The first signal path 531 comprises the analogue beamforming radio circuit 520. The first signal path 531 may comprise an ADC 525. In some embodiments herein, such as depicted in Figure 5b, the first signal path 531 comprises a single ADC. The beamforming radio circuit 520 may also be referred to as a radio chain or may be part of a radio chain. Although not depicted in Figure 5a the wireless radio-frequency receiver 500 may further comprise a digital beamforming circuit. The second signal path 532, which is at least partly parallel to the first signal path 531, comprises an analogue crossbar array 540. The analogue crossbar array 540 may be a separate circuit and even may be on a separate die than a radio frequency IC comprising the analogue beamforming radio circuit 520. A respective antenna element 511-514 is connected to a corresponding input of the analogue crossbar array 540. There may be further electronic circuits between the antenna elements 511-514 and the analogue crossbar array 540. Both the first signal path 531 and the second signal path 532 may be composed of multiple branches corresponding to the multiple antennas 511-514. There may be one branch per antenna. The branches may form at least a part of respective signal path. For example, the second signal path 532 may be composed of branches between the antenna elements and the analogue crossbar array 540. The analogue crossbar array 540 is configured to provide output signals that is the result of a matrix multiplication of input signals of the analogue crossbar array 540. The matrix multiplication may for example represent a transform, such as a Fourier transform, of the input signal. Both the input signal and the output signal are each a vector. The input to the analogue crossbar array 540 may not only be a signal from the antenna elements 511-514. The input may also contain multiple inputs from the same antenna element and also some inputs may be provided with a value of zero. This may be done to increase a resolution of the input (x,y) plane for better beam resolution estimation. Like for FFT if the number of samples in a time signal is high, a resolution in frequency domain will also be high. The crossbar elements of the analogue crossbar array 540 may be configured such that a respective provided output signal represents signal strength of a received radio signal in a beam direction when a respective input signal represents signal strength of the received radio signal at a position of a corresponding antenna element. Thus, the crossbar elements of the analogue crossbar array 540 may be programmed according to equation (2) above. The digital baseband processor 530 may provide the values for the crossbar elements of the analogue crossbar array 540. As the value of the crossbar elements programmed according to equation (6) cannot be negative, additional circuitry may be implemented. One of the ways is to include an offsetting mechanism. If the maximum swing due to sin(2^^^^^^^^^^^^) or [cos(2^^^^^^^^^^^^)] is ^^^^0, the required minimum offset would be ^^^^0. Thus, the offset ^^^^0may be applied to the input vector to obtain the following modified output vector, i.e., The effect of the added offset ^^^^0may be compensated from the output vector, which may be achieved by subtracting ^^^^0, scaled by factor ^^^^0(which may depend on the maximum swing of [^^^^^^^^] or [^^^^^^^^]), from the output, i.e.., In some embodiments herein the crossbar elements are programmed with an offset compared to the matrix elements, such as DFT elements. The offset may be needed to avoid any negative value of the crossbar elements. The offset may be added with a DC voltage and later may be subtracted with analogue circuits. Such subtracting circuits may be arranged after the crossbar array 540, e.g. in digital domain or where the output current signals are generated. Subtraction may be performed per crossbar column. In some other embodiments the subtracting circuits may be arranged after a current-to-voltage converter arranged after the crossbar array 540, or after a parallel to serial circuit 550 between the analogue crossbar array 540 and the digital baseband processor 530. The parallel to serial circuit 550 converts the parallel output of the analogue crossbar array 540 to serial form. The second signal path 532 may further comprise an ADC 555 between the parallel to serial circuit 550 and the digital baseband processor 530. By converting the parallel output to serial output the number of required ADCs of the second signal path 532 is reduced. For example, only a single ADC may be needed. In other embodiments there may be an ADC for each output of the crossbar array 540. By having an ADC for each output of the crossbar array 540 the conversion from analogue to digital domain may be faster with some cost as ultimately the digital processor still needs to perform parallel to serial conversion for listing. In some embodiments herein the wireless receiver 500 is configured to identify the beam direction of the received beam. This will be discussed further below. Figure 5b illustrates a further block diagram of the wireless radio-frequency receiver 500. Figure 5b discloses further optional circuits and elements of the wireless radio-frequency receiver 500. The beamforming radio circuit 520 may comprise a respective sub-circuit per antenna element corresponding to the branches of the first signal path mentioned above. The respective analogue beamforming radio circuit 520 may comprise an LNA 521. The respective analogue beamforming radio circuit 520 may further comprise a coupler 522. The coupler 522 may be used to collect the input signal to the analogue crossbar array 540. The coupler 522 may be arranged after the LNA 521 but before a phase shifter 523 of the analogue beamforming radio circuit 520. The coupler 522 may in some embodiments be arranged before the LNA 521. The coupling of the coupler may be as low as -20 dB. The phase shifter 523 may be a vector modulator phase shifter. A vector modulator phase shifter may comprise a 90-degree hybrid such that the coupler 522 may be an integral part of the phase shifter 523. In such a design the coupler 522 may collect the input to the clocked-buffered rf signal to be fed to the crossbar array 540 at the phase shifter 523 before the gain / attenuation block for each path of the phase shifter 523. A vector modulator can be used to perform a phase shift function, with the added benefit of amplitude control. A signal is split into two signals that are 90 degrees apart (in phase and quadrature). There are many ways to generate quadrature signals. The two halves of the signal are then passed through independent variable attenuators, which can also provide 180 degree phase shift. The respective analogue beamforming radio circuit 520 may also comprise a respective mixer 526 for frequency conversion. In Figure 5b the second signal path 532 further comprises a quadrature circuit 541 to translate the radio signal, received by an antenna element, to its in-phase and quadrature components. In some embodiments herein the quadrature circuit 541 is a hybrid coupler. As mentioned above the phase shifter 523 may comprise a hybrid coupler. Thus, the quadrature circuit 541 may be part of the phase shifter 523. Figure 5c illustrates a first part of the wireless radio-frequency receiver 500 connected to a first antenna element 511 of the multiple antenna elements 511-514. Figure 5c also discloses further optional circuits of the wireless radio-frequency receiver 500. In Figure 5c the second signal path 532 further comprises a clock buffer 542, such as a sample and hold circuit, arranged between the antenna elements 511-514 and the crossbar array 540. The clock buffer 542 may be arranged between the quadrature circuit 541 and the crossbar array 540. There may be a clock buffer 542 per component of the input signal to the analogue crossbar array 540. Thus, there may be a clock buffer 542 for the in-phase component and another clock buffer 542 for the quadrature component per antenna element, that is for each antenna branch. The clock buffer 542 may collect an instantaneous value of the radio signal. The clock buffer 542 may have a certain integration time during which it collects the input signal for the analogue crossbar array 540. The integration time to the different clock buffers 542 may need to be synchronized. As an example, the integration time of the clock buffer 542 may be 30 % of the period of the RF signal’s carrier frequency. Scaling with gain block and offset with additional DC voltage level to be applied to have a desired response level from the crossbar. For example, an ADC following the crossbar array 540 may operate with a certain range, such as a certain voltage range. A first clock signal may be provided by the digital baseband processor 530 to the clock buffer 542. The first clock signal may have a clock frequency ranging from 1 MHz to 10 GHz, e.g.256 MHz. Thus, the input signal to the analogue crossbar array 540 may be provided with the same frequency as the first clock signal. A second clock signal may be provided by the digital baseband processor 530 to the parallel to serial circuit 550 to collect the output information from the crossbar array 540 in a synchronized manner such that the value of each crossbar output are for the same time instance. The second clock signal may have a clock frequency ranging from 1 MHz to 10 GHz, e.g.256 MHz. Figure 5c illustrates further optional circuits of the wireless radio-frequency receiver 500. In Figure 5c the second signal path further comprises a scale and offset circuit 544. The scale and offset circuit 544 may scale and offset the input signal to the analogue crossbar array 540. By scaling and offsetting the input signal the input signal may be tuned to a certain input range that the analogue crossbar array 540 can handle. The corresponding digital values of all the input samples as well as the DFT coefficients may be represented using equation 2’s complement binary representation. In this way, all negative values may be converted to corresponding analogue-domain values to be used in the crossbar array 540. Also, the magnitude of the DFT coefficients may always be less than one, which may be mapped to the conductance levels of the crossbar elements. Similarly, the magnitude of the input signals may be mapped in the same range as the values of the crossbar elements to achieve more accurate computations. In absence of any filter the noise may be very high at the clock buffer 542 to distort estimation of the beam direction. However, the antenna may have an interface to the input of the LNA which will have limited bandwidth. Typically, a natural passive network may have 10% fractional bandwidth, i.e. a bandwidth equal to 10% of the carrier frequency. Thus, it is expected to have 3-5 GHz bandwidth at each of the antenna interfaces for a 28 GHz ABF receiver. Additionally, to mitigate white noise to the clock buffer 542, embodiments herein may include a filter at the input to each of the clock buffers 542. The filter will help when the channel is noisy, e.g. with SNR as low as - 20 dB. Figure 5d illustrates a further block diagram of the first part of the wireless radio-frequency receiver 500 connected to the first antenna element 511 of the multiple antenna elements 511-514. Figure 5d discloses further optional circuits of the wireless radio-frequency receiver 500. In particular, Figure 5d discloses a circuit block diagram of a single antenna element 511 and its interface to the crossbar array 540. In Figure 5d the second signal path 532 further comprises a radio-frequency filter 543 arranged between the antenna elements 511-514 and the crossbar array 540. In particular, the radio-frequency filter 543 may be arranged between the antenna elements 511-514 and the clock buffer 542. More in particular, the filter 543 may be arranged between the quadrature circuit 541 and the clock buffer 542. The radio-frequency filter 543 may be a bandpass filter or a low-pass filter. The filter may be a 1-2 order Butterworth filter with broadband response. In an example averaging is set at 50, a bandwidth of the radio-frequency filter 543 is 0.2 GHz and an antenna matching bandwidth is 10 GHz. However, realistically the bandwidth of the radio-frequency filter 543 may need to cover the entire bandwidth the receiver 500 is designed for. Then 1 or 3 GHz bandwidth of the radio- frequency filter 543 may be reasonable. Figure 6 illustrates an example of clock pulses as a function of time. The upper part of Figure 6 illustrates clock pulses for the clock buffer 542. The same clock pulse may be used to collect rf components from all of the antenna elements 511-514. Therefore, there may be need for synchronization / time alignment or corresponding calibration. The second path 532 may comprise a time calibration circuit 545, shown in Figure 5c, which performs synchronization of the clock pulses to the different branches of the second path. The width of the clock pulses may define the integration duration for the clock buffer 542. The bottom timing diagram of Figure 6 shows clock pulses for parallel to serial conversion (muxing) of the output of the analogue crossbar array 540. The number of outputs may depend on the angular resolution for beam directions Figure 7 illustrates a flowchart of a method, performed by the wireless radio frequency receiver 500, or by a network node or a wireless device comprising the wireless radio frequency receiver 500, for providing output signals based on received radio signals according to embodiments herein. The wireless receiver 500 has been described above. The method of Figure 7 may be used in a live scenario, as well as sequentially. In a live scenario, the digital baseband processor 530of the device may continuously feed the information about the alternate beam. Thus, it may adopt the next beam link immediately in case of any beam link failure. In case of any beam failure, the processor performs sequential steps to take the input from the analogue crossbar array 540 to identify the next beam and reestablish beam communication. Thus, the method may start after a beam link failure. The wireless receiver 500 may determine that a beam link failure has occurred or obtain an indication of an occurred beam link failure. Action 701 The wireless receiver 500 may set values of the crossbar elements of the crossbar array 540 based on the position of the antenna elements 511-514 and further based on an angular resolution of the beam directions to be determined. The values of the crossbar elements of the crossbar array 540 may be set such that a respective provided output signal represents signal strength in a beam direction when a respective input signal represents signal strength at a position of an antenna element. Action 702 The wireless receiver 500 obtains input signals of the analogue crossbar array 540 by collecting a part of the radio signal, to perform calculations on the collected input signal. For example, the wireless receiver 500 may use the coupler 522 to collect the input signal. In some embodiments disclosed herein the wireless receiver 500 processes the input signal, e.g. according to the description below. In some embodiments disclosed herein the wireless receiver 500 splits the radio signal into its in-phase and quadrature components. Thus, the input signals of the analogue crossbar array 540 may comprise sampled in- phase and quadrature components of the received radio signals. The wireless receiver 500 may further filter the radio signal. In some embodiments disclosed herein the wireless receiver 500 further integrates the input signals of the analogue crossbar array 540 within a time interval. This may be done to collect an instantaneous value of the radio signal. The time interval may be 10-490 % of a period of the received radio signal’s carrier frequency, preferably 30- 70 % of the period of the received radio signal’s carrier frequency. The wireless receiver 500 may further scale and / or offset the input signal to the crossbar array 540. Action 703 The wireless receiver 500 provides output signals from the analogue crossbar array 540 by matrix multiplying input signals of the analogue crossbar array 540. The wireless receiver 500 may provide output signals in the form of signal strength of a received radio signal as a function of a beam direction when a respective input signal represents signal strength of the received radio signal at a position of a corresponding antenna element. The output signal may be provided for specific directional angles, such as specific azimuth and elevation angles. The wireless receiver 500 may identify a beam direction of the received radio signal. The wireless receiver 500 may identify a beam direction of the received radio signal based on the provided output signals from the analogue crossbar array 540. Action 704 In some embodiments disclosed herein the wireless receiver 500 further averages the output signals of the analogue crossbar array 540 within a time interval. The time interval may be a time interval where the beam direction of the received beam and / or an orientation of the wireless receiver 500 is stable, or within a pre- determined time interval of a received reference signal. By averaging the wireless receiver 500 is able to suppress noise. The averaging may be performed by the baseband processor 530 of the wireless receiver 500. For SSB detection, continuous measurements and averaging may be done within the interval of each SSB time slot. Action 705 In some embodiments disclosed herein the wireless receiver 500 further adapts the analogue beamforming radio circuit 520 based on the signal outputs of the analogue crossbar array 540. Adapting the analogue beamforming radio circuit 520 based on the signal outputs of the analogue crossbar array 540 may comprise: analysing the outputs of the analogue crossbar array 540 with the digital baseband processor 530, and setting beam weighting factors of the antenna elements 511-514 with the digital baseband processor 530 based on analysing the outputs. Thus, setting beam weighting factors of the antenna elements 511-514 may be based on an analysis of the outputs of the crossbar array 540. Analysing the outputs of the analogue crossbar array 540 with the digital baseband processor 530 may comprise determining a strongest beam direction. Then setting beam weighting factors of the antenna elements 511-514 with the digital baseband processor 530 may be based on the determined strongest beam direction. Analysing may further comprise filtering out directions where Fourier transform values are strong. The beam weighting factors may be changed by adjusting phase or gain or both of the radio signal. The phase shifter 523 may adjust the phase and / or gain of the radio signal. In some embodiments herein the baseband processor 530 extracts a list of highest output values from the crossbar array 540 with some distribution (no overlapping). Then the baseband processor 530 will try a beam with the highest output values, check if it is the right signal or noise. If it turns out to be noise it tries the beam corresponding to the next highest values from the list. As an example, if the angular resolution of beam direction is 5 degrees, and the beam scanning area is -60 to 60 degrees for azimuth and -15 to 15 degrees in elevation, then the total number of outputs would be 25x7= 175. Then within one calculation period, 175 clock pulse may be needed for MUXing to collect the beam information. As the output of the crossbar array 540 is DC within one calculating period and in a less noisy environment, sample and hold integration time is not a critical parameter. It is expected to have certain delay between input clock and the starting of a MUX pulse at output. If required resolution of beam direction is 5 degrees for Radio Access Network (RAN), scanning -60 degree to 60 in azimuth, -15 to 15 degrees in elevation, the number of a directional values set will be 175. If the clock speed is 256 MHz a total time needed for serial to parallel conversion of the output from the crossbar array 540 is 683.6 ns. So within 1 microsecond, a set of beam direction measurements may be done. If a required resolution is 10 degrees for a UE, scanning -45 degrees to 45 degrees in azimuth, -45 to 45 degrees in elevation, the number of the directional values set will be 100. If the clock speed is 20 MHz, total time needed for serial to parallel is 5 microseconds. So within 10 microseconds, a set of beam direction measurements may be done. Thus, the above example may be suitable for each SSB. However, each time there is movement of the UE, averaging may need to be restarted. The disclosed embodiments have the following advantages: • Fewer data converters since the required computations are performed in the analogue domain. • Less power consumption, since memristor devices are very power efficient • Fast identification of different beam directions • Fast beam recovery Performing DFT / IDFT using a crossbar array will: Reduce the computational complexity significantly compared to prior art methods. Enable parallel computation, which means that calculation of the beam weights will be done very fast. Enable flexibility in terms of variable DFT sizes in case that the beamforming parameters are changed. Figure 8 schematically illustrates a network node 1511 for a wireless communications network 100, the network node 1511 comprising the wireless receiver 500. Figure 9 schematically illustrates a wireless communications device 1613, comprising the wireless receiver 500. The wireless communications device 1613 may be a User Equipment. The network node 1511 and the wireless communications device 1613 may be configured to perform the method actions of Figure 7 above. The embodiments herein may be implemented through a processor or one or more processors, such as the processor 1504, 1604 of a processing circuitry in the network node 1511 and the wireless communications device 1613 respectively, and depicted in Figure 8 and 9 together with computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the network node 1511 and the wireless communications device 1613 respectively. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the network node 1511 and the wireless communications device 1613 respectively. The network node 1511 and the wireless communications device 1613 respectively may further comprise a memory 1502, 1602 comprising one or more memory units. The memory comprises instructions executable by the processor in the network node 1511 and the wireless communications device 1613 respectively. The respective memory 1502, 1602 is arranged to be used to store e.g. information, data, configurations, and applications to perform the methods herein when being executed in the network node 1511 and the wireless communications device 1613 respectively. In some embodiments, a computer program 1503, 1603 comprises instructions, which when executed by the at least one processor, cause the at least one processor of the network node 1511 and the wireless communications device 1613 respectively to perform the actions above. In some embodiments, a carrier 1505, 1605 comprises the computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium. The network node 1511 and the wireless communications device 1613 respectively may further comprise an input and output interface, I / O, 1506, 1606 configured to communicate with other devices. The input and output interface 1506, 1606 may comprise a receiver, such as a wireless receiver, (not shown) and a transmitter, such as a wireless transmitter, (not shown). Those skilled in the art will also appreciate that the units described above may refer to a combination of analogue and digital circuits, and / or one or more processors configured with software and / or firmware, e.g. stored in the network node 1511 and the wireless communications device 1613 respectively, that when executed by the respective one or more processors such as the processors described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC). Figure 10 illustrates a wireless communications network 170 in which embodiments herein may be implemented. The wireless communications network 170 may use a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, 5G, New Radio (NR), Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications / enhanced Data rate for GSM Evolution (GSM / EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. Embodiments herein relate to recent technology trends that are of particular interest in a 5G context. However, embodiments are also applicable in further development of other existing wireless communication systems such as e.g. WCDMA and LTE and in future wireless communication systems, such as 6G systems. Network nodes operate in the wireless communications network 170 such as the network node 1511. The network node 1511 provides radio coverage over a geographical area, a service area referred to as a cell 15, which may also be referred to as a beam or a beam group of a first radio access technology (RAT), such as 5G, LTE, Wi-Fi or similar. There may be more than one cell. For example, there may be a second cell 16 as well. The network node 1511 may be a NR-RAN node, transmission and reception point e.g. a base station, a radio access node such as a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access controller, a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), a gNB, a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit capable of communicating with a wireless device within the service area depending e.g. on the radio access technology and terminology used. The respective network node 1511 may be referred to as a serving radio access node and communicates with a UE with Downlink (DL) transmissions to the UE and Uplink (UL) transmissions from the UE. A number of wireless communications devices operate in the wireless communication network 10, such as the wireless communications device 1613. The wireless communications device 1613 may be a mobile station, a non-access point (non-AP) STA, a STA, a user equipment and / or a wireless terminal, a wireless communication terminal, a Machine Type Communication (MTC) device, a Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a small base station communicating within a cell, that communicate via one or more Access Networks (AN), e.g. RAN, e.g. via the network node 1511 to one or more core networks (CN) e.g. comprising a CN node 13, for example comprising an Access Management Function (AMF). When using the word "comprise" or “comprising” it shall be interpreted as non- limiting, i.e. meaning "consist at least of". The embodiments herein are not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used.

Claims

CLAIMS 1. A wireless radio-frequency receiver (500) comprising multiple antenna elements (511-514) for receiving a radio signal, an analogue beamforming radio circuit (520), a digital baseband processor (530), a first signal path (531) and a second signal path (532) from the multiple antenna elements (511-514) to the digital baseband processor (530), wherein the first signal path (531) comprises the analogue beamforming radio circuit (520) and wherein the second signal path (532), which is at least partly parallel to the first signal path (531), comprises an analogue crossbar array (540), wherein a respective antenna element (511-514) is connected to a corresponding input of the analogue crossbar array (540), the analogue crossbar array (540) being configured to provide output signals that is the result of a matrix multiplication of input signals of the analogue crossbar array (540).

2. The wireless receiver (500) according to claim 1, wherein crossbar elements of the analogue crossbar array (540) are configured such that a respective provided output signal represents signal strength of a received radio signal in a beam direction when a respective input signal represents signal strength of the received radio signal at a position of a corresponding antenna element.

3. The wireless receiver (500) according to claim 2, wherein the wireless receiver (500) is configured to: identify the beam direction of the received beam.

4. The wireless receiver (500) according to any of claims 1-3, wherein the second signal path (532) further comprises a quadrature circuit (541) to translate a radio signal, received by an antenna element, to its in-phase and quadrature components.

5. The wireless receiver (500) according to claim 4, wherein the quadrature circuit (541) is a hybrid coupler.

6. The wireless receiver (500) according to any of the claims 1-5, wherein the second signal path (532) further comprises a clock buffer (542) arranged between the antenna elements (511-514) and the crossbar array (540).

7. The wireless receiver (500) according to any of claims 1-6, wherein the second signal path (532) further comprises a radio-frequency filter (543) arranged between the antenna elements (511-514) and the crossbar array (540).

8. The wireless receiver (500) according to claim 7, wherein the radio-frequency filter (543) is arranged between the antenna elements (511-514) and the clock buffer (542).

9. The wireless receiver (500) according to any of the claims 1-8, wherein the respective analogue beamforming radio circuit (520) comprises a respective phase shifter (523) and a Low-Noise Amplifier, LNA (521).

10. A network node (1511) for a wireless communications network (100), the network node (1511) comprising the wireless receiver (500) of any of the claims 1-9.

11. A wireless communications device (1613), comprising the wireless receiver (500) of any of the claims 1-9.

12. The wireless communications device (1613) according to claim 11, wherein the wireless communications device (1613) is a User Equipment.

13. A method, performed by a wireless radio frequency receiver (500), for providing output signals based on received radio signals, the wireless receiver (500) comprising multiple antenna elements (511-514) for receiving the radio signals, an analogue beamforming radio circuit (520), a digital baseband processor (530), a first signal path (531) and a second signal path (532) from the multiple antenna elements (511-514) to the digital baseband processor (530), wherein the first signal path (531) comprises the analogue beamforming radio circuit (520) and wherein the second signal path (532), which is at least partly parallel to the first signal path (531), comprises an analogue crossbar array (540), wherein a respective antenna element (511-514) is connected to a corresponding input (541-644) of the analogue crossbar array (540), the method comprising: providing (703) output signals from the analogue crossbar array (540) by matrix multiplying input signals of the analogue crossbar array (540).

14. The method according to claim 13, wherein providing (703) output signals comprises providing (703) output signals in the form of signal strength of a received radio signal as a function of a beam direction when a respective input signal represents signal strength of the received radio signal at a position of a corresponding antenna element.

15. The method according to claim 13 or 14, further comprising: identifying a beam direction of the received radio signal.

16. The method according to any of the claims 13-15, further comprising: adapting (705) the analogue beamforming radio circuit (520) based on the signal outputs of the analogue crossbar array (540).

17. The method according to claim 16, wherein adapting (705) the analogue beamforming radio circuit (520) based on the signal outputs of the analogue crossbar array (540) comprises: analysing (705a) the outputs of the analogue crossbar array (540) with the digital baseband processor (530); and setting (705b) beam weighting factors of the antenna elements (511-514) with the digital baseband processor (530) based on analysing (705a) the outputs.

18. The method according to claim 17, wherein analysing (705a) the outputs of the analogue crossbar array (540) with the digital baseband processor (530) comprises: determining a strongest beam direction; and wherein setting (705b) beam weighting factors of the antenna elements (511-514) with the digital baseband processor (530) is based on the determined strongest beam direction.

19. The method according to any of the claims 13-18, further comprising: setting (701) values of crossbar elements of the crossbar array (540) based on the position of the antenna elements (511-514) and further based on an angular resolution of the beam directions to be determined.

20. The method according to claim 19, wherein the values of the crossbar elements of the crossbar array (540) are set such that a respective provided output signal represents signal strength in a beam direction when a respective input signal represents signal strength at a position of an antenna element.

21. The method according to any of the claims 13-20, wherein the input signals of the analogue crossbar array (540) comprise sampled in-phase and quadrature components of the received radio signals.

22. The method according to any of claims 13-21, further comprising: averaging (704) the output signals of the analogue crossbar array (540) within a time interval where the beam direction of the received beam and / or an orientation of the wireless receiver (500) is stable, or within a pre-determined time interval of a received reference signal.

23. The method according to any of claims 13-22, further comprising: integrating (702c) the input signals of the analogue crossbar array (540) within a time interval.

24. The method according to claim 23, wherein the time interval is 20-100 % of a period of the received radio signal’s carrier frequency, preferably 30-70 % of the period of the received radio signal’s carrier frequency.

25. A computer program (1503, 1603), comprising computer readable code units which when executed on a computer causes the computer to perform the method according to any one of claims 13-24.

26. A carrier (1505, 1605) comprising the computer program according to claim 25, wherein the carrier (1505, 1605) is one of an electronic signal, an optical signal, a radio signal and a computer readable medium.

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