A satellite receiver with positioning capability and method for using the same

Abstract

A satellite receiver (200) for satellite positioning, the satellite receiver (200) comprising a first phased array antenna (210), a control unit (220), and a database (230). The database comprises data relating to orbits of one or more satellites (120). The first phased array antenna (210) is arranged to receive one or more signals from one or more satellites (120). The receiver (200) is arranged to subsequently determine a direction of arrival, DOA, of at least one signal of the one or more signals, and to estimate a position of the satellite receiver (200) corresponding to the DOA of the at least one signal given the data relating to orbits of one or more satellites (120).

Description

[0001] TITLE

[0002] A satellite receiver with positioning capability and method for using the same

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to satellite positioning and communication systems. There are disclosed devices and methods for positioning using satellite signals not originally intended for that purpose.

[0005] BACKGROUND

[0006] The ability to obtain reliable positioning information is crucial in many technical applications, most notably in transportation where accurate positioning enables efficient navigation for ground vehicles, aircraft, and ships. Global navigation satellite systems (GNSS) such as GPS or Galileo are most commonly used to provide location and timing information, enabling numerous essential applications. However, GNSS systems can produce unreliable results or no results under some circumstances, such as in areas where the signals are partially or fully blocked or due to intentional jamming or spoofing of the satellite signals. Under such circumstances, it is an advantage to have access to an alternative means of positioning.

[0007] Alternative positioning methods may entail using available signals or data not originally intended for positioning. Such methods are sometimes referred to as opportunistic positioning and leverage signals from various sources, such as cellular base stations and non-navigation satellites. Alternative positioning methods can provide the ability to perform positioning in the absence of GNSS services. However, this requires the development of efficient and reliable methods for performing opportunistic positioning with high precision.

[0008] US11729583 B2 discloses opportunistic position estimation using available signals, primarily signals originating from cellular base stations.

[0009] Orabi et al., “Opportunistic Navigation with Doppler Measurement from Iridium Next and Orbcomm Leo Satellites”, 2021 IEEE Aerospace Conference, discloses methods for position estimation using the Doppler shift of signals from low Earth orbit satellites.

[0010] Still, there is a need for methods and devices that can perform positioning more efficiently. SUMMARY

[0011] It is an objective of the present disclosure to provide improved alternative positioning methods, which, i.a., offer faster and more efficient position estimation. This objective is at least in part obtained by a satellite receiver for satellite positioning. The receiver comprises a first phased array antenna, a control unit, and a database which in turn comprises data relating to orbits of one or more satellites. The first phased array antenna is arranged to receive one or more signals from one or more satellites. The receiver is arranged to determine a direction of arrival, DOA, of at least one signal of the one or more signals, and to find a position of the receiver corresponding to the DOA of the at least one signal and the data relating to orbits of one or more satellites.

[0012] Determining the DOA of at least one signal gives an estimated position of the satellite receiver relative to the satellite from which the signal originates. The position of the satellite can be derived from data relating to the orbit of the satellite, as comprised in the database. In combination, this can be used to produce an estimate of the position of the satellite receiver. The satellite can be any satellite that transmits signals towards the surface of the Earth, such as a communication satellite. That is, it does not have to be a satellite that is intended to be used for positioning.

[0013] Communication satellites are generally part of larger satellite constellations. While the signals from a single satellite can only be received in a limited area, the constellation as a whole may transmit signals that cover most or all of the surface of the Earth. Furthermore, the satellite receiver may be arranged to use signals from multiple satellite constellations. Thus, the satellite receiver will be able to receive satellite signals and produce an estimate of its position also in remote areas.

[0014] Determining the DOA of a signal can be performed quickly and does not require an extended measurement time. This is an advantage compared to some other methods of determining the relative location of a receiver to a satellite. As an example, Doppler tracking requires the satellite to be tracked for an extended period of time as it uses the Doppler shift of a signal to determine the point at which the satellite is closest to the receiver.

[0015] The satellite receiver may be arranged to determine a signal quality of each of the one or more signals, and to determine the DOA of signals that meet predetermined signal quality acceptance criteria.

[0016] Advantageously, introducing signal quality acceptance criteria makes it possible to discard signals that, for example, are weak or have a low signal-to-noise ratio. The computational resources required for determining the DOA can then be allocated only to signals with sufficient signal quality. The estimated DOA can also be more accurate for a signal with a high signal-to-noise ratio, which is an advantage.

[0017] Preferably, the first phased array antenna is a two-dimensional phased array antenna. With a two-dimensional array the DOA can be determined in terms of two angles, such as the azimuth angle and elevation angle relative to the array, which is an advantage.

[0018] According to some alternatives, the first phased array antenna is configured to receive signals within a first frequency band. The first frequency band may be any of the Ka or Ku bands.

[0019] The Ka and Ku bands occupy the frequency ranges 26.5 to 40 GHz and 12 to 18 GHz respectively. They are frequently used in satellite communication (SATCOM) applications, so that there are a lot of available satellite signals within these frequency bands. Furthermore, the Ka and Ku frequency bands are far removed from the frequencies used by dedicated positioning systems such as GPS and Galileo, which use the L1 , L2, and L5 bands at 1575.42 MHz, 1227.6 MHz and 1176 MHz respectively. Interference, jamming, or spoofing in the L1 , L2, and L5 bands would thus not affect the Ka and Ku bands the way it might affect an adjacent frequency band.

[0020] The satellite receiver may comprise a second phased array antenna configured to receive signals in a second frequency band. Preferably, the second frequency band is different from the first frequency band used by the first phased array antenna.

[0021] Use of two or more phased array antennas configured for different frequency bands increases the number of satellite signals that can be used for positioning, as it enables the use of satellite signals in different frequency bands. The second frequency band may for example be any of the Ka and Ku bands.

[0022] The satellite receiver may also comprise at least one auxiliary sensor. Here, the auxiliary sensor may be any of an accelerometer, a gyroscope, a magnetometer, and an altitude sensor, or it may be any other suitable sensor.

[0023] The auxiliary sensors can be used to measure quantities such as the altitude at which the satellite receiver is located, the direction of gravitational acceleration, the orientation of the first and / or second phased array antenna, etc. Such measurements can be used in combination with the estimated DOA of a satellite signal to estimate the position of the satellite receiver, e.g. by providing data on the orientation of the first and second phased array antennas in relation to a global coordinate system. This may improve the quality of the position estimate, or it can be used to reduce the number of satellite signals needed to obtain a sufficiently accurate estimate of the position of the receiver. Accordingly, the satellite receiver may be arranged to obtain a measurement data from at least one auxiliary sensor, and to estimate the position of the satellite receiver based at least in part on the measurement data.

[0024] According to a preferred alternative, the satellite receiver may comprise a timekeeping device or clock with a low degree of clock drift. The clock may according to some examples comprise a crystal oscillator, such as a MEMS oscillator or an oven- controlled crystal oscillator (OCXO). An accurate timekeeping device enables the satellite receiver to determine the expected position of the satellite with higher accuracy, which is an advantage.

[0025] The satellite receiver may comprise a global navigation satellite system, GNSS, device, and be arranged to detect an abnormal condition in the operation of the GNSS device. An abnormal condition in the operation of the GNSS device may be any condition indicating that the functionality of the device is impeded. Advantageously, if the satellite receiver comprises a GNSS device, detecting an abnormal condition in the operation enables switching to using the position estimate produced based on DOA of satellite signals as described above rather than that produced by the GNSS device. This can for example help mitigate the negative effects of GNSS signal jamming or spoofing.

[0026] The satellite receiver may be part of a satellite communication (SATCOM) terminal configured for two-way communication with a satellite. Accordingly, the satellite receiver may be arranged to transmit a transmit signal to at least one satellite.

[0027] Optionally, the satellite receiver may be arranged to determine the Doppler shift of at least one signal from at least one satellite and to track the position of the receiver relative to the at least one satellite by means of the Doppler shift.

[0028] The objective is also obtained at least in part by a method for operating a satellite receiver for satellite positioning. The satellite receiver comprises a first phased array antenna, a control unit, and a database. The database comprises data relating to an orbit of one or more satellites. The method comprises receiving, by the first phased array antenna, one or more signals from one or more satellites. The method also comprises determining, by the receiver, a direction of arrival, DOA, of at least one signal of the one or more signals, and finding, by the satellite receiver, a position of the receiver corresponding to the DOA of the at least one signal and the data relating to orbits of one or more satellites.

[0029] Finding a position of the receiver may comprise obtaining a current time and determining a position of the one or more satellites using the data relating to orbits and the current time. The current time can for example be obtained from a timekeeping device comprised in the satellite receiver.

[0030] The method may also comprise determining a signal quality of each of the one or more signals and comparing the determined signal quality to predetermined signal quality acceptance criteria. Advantageously, this allows for discarding signals that are weak or have low signal to noise ratio.

[0031] According to some alternatives, the satellite receiver comprises a second phased array antenna. The method then comprises receiving, by the second phased array antenna, one or more signals from one or more satellites, and determining, by the satellite receiver, a DOA of at least one signal of the one or more signals received by the second phased array antenna. Advantageously, the second phased array antenna may operate in a different frequency band compared to the first phased array antenna, thereby allowing the satellite receiver to receive signals in two frequency bands.

[0032] The method may also comprise evaluating a signal quality of each of the one or more signals received by the second phased array antenna and comparing it to the predetermined signal acceptance criteria.

[0033] According to some aspects, the method comprises obtaining a measurement from at least one auxiliary sensor and finding the position of the satellite receiver based at least in part on the measurement data. Finding the position of the satellite receiver based at least in part on such measurement data may entail obtaining the altitude of the receiver from an altitude sensor, finding the direction of gravitational acceleration using one or more accelerometers, and(or identifying an orientation of the first and / or second phased array antenna by means of accelerometers, gyroscopes, and similar sensors.

[0034] The method may also comprise detecting an abnormal condition in the operation of a GNSS device comprised in the satellite receiver. An abnormal condition may be any condition impeding the function of the GNSS device and / or rendering the position estimate produced by it less reliable. Detecting an abnormal condition may comprise comparing a position estimation produced by the GNSS device to that produced based on the DOA of at least the first signal. Advantageously, this enables the satellite receiver to identify whether the position estimate produced by the GNSS device starts to shift away from that produced based on the DOA estimate.

[0035] According to some aspects, the method may also comprise operating the satellite receiver according to the estimated position of the satellite receiver. This may for example entail displaying the estimated position by means of a graphical user interface or using the estimated position for navigation.

[0036] Optionally, the method may comprise transmitting a transmit signal to at least one satellite.

[0037] According to some alternatives, the method may comprise determining a Doppler shift of at least one signal from at least one satellite and tracking the position of the satellite receiver relative to the at least one satellite by means of the Doppler shift.

[0038] There is also herein disclosed a satellite transceiver for satellite communication. The satellite transceiver comprises a first transceiver antenna arranged to transmit and / or receive signals in a first frequency band and a second transceiver antenna arranged to transmit and / or receive signals in a second frequency band. Here, the second frequency band is different from the first frequency band. The satellite transceiver also comprises at least a first modem and an antenna control unit, where the antenna control unit is arranged to control transmission of a first signal from the first transceiver antenna and transmission of a second signal from the second transceiver antenna, and / or to process a signal received by the first transceiver antenna and a signal received by the second transceiver antenna.

[0039] The methods disclosed herein are associated with the same advantages as discussed above in connection to the different apparatuses. There is also disclosed herein computer programs, computer program products, and control units associated with the above-mentioned advantages.

[0040] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realizes that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.

[0041] BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present disclosure will now be described in more detail with reference to the appended drawings, where:

[0043] Figure 1 schematically illustrates vehicles in communication with a satellite constellation;

[0044] Figure 2 schematically illustrates a satellite receiver;

[0045] Figure 3 provides a schematic illustration of an antenna array;

[0046] Figure 4 illustrates satellites in communication with a satellite receiver;

[0047] Figure 5 shows a satellite terminal;

[0048] Figure 6 schematically illustrates a control unit;

[0049] Figure 7 is a flow chart illustrating methods;

[0050] Figure 8 schematically illustrates a satellite transceiver; and

[0051] Figure 9 is a flow chart illustrating methods.

[0052] DETAILED DESCRIPTION

[0053] Aspects of the present disclosure will now be described more fully with reference to the accompanying drawings. The different devices and methods disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

[0054] The terminology used herein is for describing aspects of the disclosure only and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Positioning is mostly performed using dedicated positioning systems and devices. The most common example of this is using a Global Navigation Satellite System (GNSS) such as GPS, Galileo, or GLONASS. GNSS satellites send out radiofrequency signals comprising data that can be used to obtain accurate timing and location information. A GNSS device or GNSS receiver is configured to calculate its distance from the satellite based on this information. Using signals from a plurality of satellites, the position of the receiver can be determined.

[0055] Other radio-frequency signals can also be used to obtain the position of a receiver, although the signals may not be originally intended for positioning. As an example, signals used for communication and data transfer can be used. This includes signals transmitted from ground-based transmitters such as base stations, but also signals from communication satellites.

[0056] Communication satellites operate by receiving signals from ground stations, amplifying them, and retransmitting the signals to receivers at different locations on the ground or in space. These satellites facilitate a range of communication services. Examples of communication satellite constellations include Iridium, Starlink, OneWeb, O3b, and Inmarsat.

[0057] The signals received from communication satellites do not comprise the type of data provided by GNSS systems, such as GPS codes and navigation messages, that enables a GNSS receiver to determine its position. Positioning using communication satellites instead relies on being able to identify the satellite, find the position of the specific satellite at the time when the signal was transmitted, and determine a relative direction of the satellite relative to the receiver.

[0058] Figure 1 shows a scenario in which a vehicle 110 equipped with a satellite communication (SATCOM) terminal 111 receives signals from two satellites 120. The signals received from each satellite will generally contain data indicating the identity of the satellite. Once the identity of each satellite is known, its orbit can be found. Communication satellites occupy orbits specific to each individual satellite. The parameters of these orbits, also known as orbital elements, are available to users of the satellites e.g. in the form of two-line element sets (TLE) that enable the user to calculate the position of a satellite at a given point in time. Thus, a control unit comprised in the terminal 111 can identify the two satellites and determine the position currently occupied by each satellite. If the relative position of the vehicle to each satellite were known, this data could then be used to estimate an absolute position of the vehicle in terms of coordinates on the Earth’s surface, i.e. latitude and longitude. However, the relative position of a SATCOM terminal to the satellite is not generally obtained during normal communication with the satellite, at least not to a high degree of accuracy.

[0059] Figure 2 is a schematic illustration of a satellite receiver 200 for satellite positioning. The receiver 200 comprises a first phased array antenna 210, a control unit 220, and a database 230, where the database comprises data relating to orbits of one or more satellites 120. The first phased array antenna 210 is arranged to receive one or more signals from one or more satellites 120, while the receiver 200 is arranged to determine a direction of arrival, DOA, of at least one signal of the one or more signals, and to find a position of the receiver 200 corresponding to the DOA of the at least one signal given the data relating to orbits of one or more satellites 120.

[0060] Note that the position of the receiver 200 found by these means will be referred to as the DOA-based estimated position and / or the DOA-based position estimate in this description.

[0061] The satellite receiver 200 as shown in Figure 2 may also comprise a second antenna array 240, one or more auxiliary sensors 250, a GNSS device 260, a graphical user interface, GUI, 270, and a connection 280 for ethernet mesh integration. These units will be discussed in more detail below.

[0062] A phased array antenna is a type of antenna system comprising multiple individual antenna elements arranged in a specific configuration. When a phased array antenna receives a signal, the phase of the signal at each element is registered. Thus, the difference in phase between elements can be determined, enabling the estimation of the DOA of the signal. By comparing the phase differences across multiple antenna elements, the system can infer the angle of arrival of the incoming signal relative to the array.

[0063] Various methods have been developed for estimating the DOA of signals using phased array antennas. These methods include but are not limited to: the Multiple Signal Classification (MUSIC) algorithm, which utilizes eigenvalue decomposition to identify the angles of arrival; the Estimation of Signal Parameters via Rotational Invariance Techniques (ESPRIT), which relies on the rotational properties of the signal subspace to provide accurate DOA estimates; and the Beamforming or Capon approach, which involves adjusting the antenna weights to form a directional response that maximizes signal reception in the desired direction. Additionally, subspace-based methods and maximum likelihood estimation techniques are commonly employed to enhance accuracy in complex environments with multipath interference or low signal-to-noise ratios. These techniques provide a robust means of determining the direction of incoming signals.

[0064] In the example of Figure 2, the first phased array antenna 210 is shown as comprising a plurality of individual elements 211 arranged at regular intervals on a plane to form a two-dimensional array. According to other examples, the first phased array antenna 210 may have antenna elements that are arranged differently, e.g. at irregular intervals or with alternating longer and shorter intervals.

[0065] A two-dimensional array as shown in Figure 2 has the advantage that both the azimuthal angle and the elevation angle of the signal can be determined, giving the full direction of arrival. Therefore, according to a preferred alternative, the first phased array antenna 210 is a two-dimensional phased array antenna. However, the first phased array antenna 210 may also be a one-dimensional array antenna.

[0066] The first phased array antenna 210 is configured to receive signals within a first frequency band. Herein, a frequency band is a range of frequencies dedicated to a specific purpose, such as satellite communications. A frequency band may be defined in terms of its maximum and minimum frequency, or in terms of a centre frequency and a bandwidth. According to some examples, the first frequency band is any of the Ka or Ku bands. The Ka band is defined within the field of radio and satellite communications as encompassing frequencies between 26.5 and 40 GHz, while the Ku band comprises frequencies between 12 and 18 GHz.

[0067] While the first phased array antenna is arranged to receive signals within a frequency band, signal processing is frequently carried out at baseband frequencies. The first phased array antenna therefore comprises processing circuitry 212, which in turn comprises means for converting a signal between baseband and the first frequency band. The processing circuitry 212 may also comprise analog-to-digital converters, a satellite modem, and any other processing circuitry necessary for processing the incoming signal.

[0068] According to some examples, the satellite receiver 200 is arranged to determine a signal quality of each of the one or more signals. The signal quality of a signal received from a satellite can for example be measured in terms signal strength, or in terms of a signal to noise ratio (SNR). The signal quality can vary depending on factors such as the distance to the satellite, weather conditions, whether the satellite is about to pass beneath the horizon from the point of view of the receiver 200, etc.

[0069] The satellite receiver 200 may also be arranged to determine the DOA only of signals that meet predetermined signal quality acceptance criteria. This can be used to ensure that only signals with sufficient quality are used to determine the position of the satellite receiver 200. According to one example, the signal quality acceptance criteria comprises that the strength and / or SNR of the signal must exceed predetermined strength and SNR thresholds. According to another example, the signal quality acceptance criteria comprise ranking the signals according signal quality and using the N signals with the highest quality, where N is a predetermined desired number of signals. Thus, if six signals are received and N is set to four, the four signals with the highest signal quality will be used. According to a third example, a signal quality acceptance criterion involving a probabilistic element may be used, such that an increased signal quality leads to a higher probability of acceptance.

[0070] Herein, data relating to orbits of one or more satellites refers to any data that can be used to predict the position of a satellite at a relevant point in time, such as the time when the signal is transmitted from the satellite. The data may for example comprise orbital elements of relevant satellite constellations.

[0071] In order to be able to determine a relevant position of the satellite, an accurate estimate of the current time must be obtained by the satellite receiver 200. According to one alternative, the satellite receiver may comprise a timekeeping device or clock with a low degree of clock drift. The clock may for example comprise an accurate crystal oscillator, such as a microelectromechanical (MEMS) oscillator or an oven- controlled crystal oscillator. The estimate of the current time provided by this timekeeping device could be used to obtain an approximate position of each satellite from which a signal is received. If the estimate of the current time provided by the timekeeping device is accurate enough, this may be sufficient to determine the position of the satellite receiver 200.

[0072] If the estimate of the current time is not in itself sufficiently accurate, it can still be used to estimate approximate positions of the satellites. This information, along with the DOA of each signal, can then be used to refine the estimate of the current time and obtain the position of the satellite receiver 200. Put another way, a system of equations can be formulated in which the coordinates of the satellite receiver 200 and the current time are variables which can be solved for. This is analogous to a GNSS receiver performing positioning by determining the pseudorange to four GNSS satellites and using said pseudoranges to obtain accurate positioning and timing information.

[0073] Note that whether the estimate of the current time is sufficiently accurate depends on a desired accuracy of the position of the satellite receiver 200. If knowing the position of the satellite receiver 200 within a hundred meters is sufficient, this places lower demands on the time estimate compared to if the position must be known with an accuracy of tens of meters. The database may comprise data relating to all available communication satellite constellations, or it may comprise data relating to a subset of satellite constellations. The subset may for example comprise satellite constellations that transmit signals at a frequency which the first phased antenna array 210 is configured to receive, i.e. , within the first frequency band.

[0074] Referring again to Figure 2, the satellite receiver 200 may comprise a second phased array antenna 240. The second phased array antenna comprises a plurality of antenna elements 241 and processing circuitry 242 arranged to perform up- and down-conversion of signals, analog-to-digital conversion, and similar processing operations. The first phased array antenna 210 and the second phased array antenna 240 are configured to receive signals in a respective first and second frequency band. Preferably, the second frequency band is different from the first frequency band.

[0075] Having the satellite receiver 200 comprise two separate phased array antennas arranged to receive signals in different frequency bands opens the possibility of accessing a larger number of satellites, as the second phased array antenna may be able to receive signals from satellite constellations that are not accessible to the first phased array antenna and vice versa. This increases the probability of obtaining a sufficient number of signals with sufficient signal quality and therefore facilitates obtaining an accurate DOA-based estimated position.

[0076] As an example, consider a scenario in which the first phased array antenna 210 receives three signals, of which only one meets the abovementioned predetermined signal quality acceptance criteria. If the second phased array antenna 240 receives three signals in the second frequency band and one or two of these signals meet the quality acceptance criteria, the positioning information from signals received by the first phased array antenna 210 and signals received by the second phased array antenna 240 can be combined in order to increase the accuracy of the DOA-based estimated position. In this case, the database 230 should naturally comprise information relating to the orbits of satellites that transmit signals in either of the first and second frequency bands. According to one alternative, the second frequency band is any of the Ka and Ku bands.

[0077] The satellite receiver 200 is configured to find in which direction, relative to the receiver 200, a satellite is to be found. This is accomplished by determining the direction of arrival, DOA, of incoming signals by means of beamforming methods as mentioned above. That is, the satellite receiver 200 is arranged to register the difference in the phase of the signal at different antenna elements and determine the DOA based on these differences.

[0078] The DOA is generally defined in relation to the array. Figure 3 shows a phased array antenna 210, 240 with the coordinate system of the array, Ca, indicated by the dashed arrows. Note that the zaaxis of the array coordinate system is perpendicular to the array surface. The DOA of an incoming signal Si can according to one example be obtained in terms of an angle 0i relative to the zaaxis and an angle q>1relative to the xaaxis. Meanwhile, the position of the satellite will generally be known in terms of longitude, latitude, and altitude, i.e. in terms of a global coordinate system Cgiobai. In order to use the DOA for positioning, the relation between the array coordinate system Caand the global coordinate system Cgiobai must be known. Furthermore, the distance between the satellite and the receiver 200 cannot be obtained from one signal alone.

[0079] According to a preferred alternative, multiple signals from multiple satellites are used to estimate the position. Figure 4 illustrates how the directions of arrival corresponding to two signals Si and S2 define two lines, which intersect in a point Pa. If the receiver 200 receives the two signals and obtains these two directions of arrival it should therefore occupy a position near the point Pa. The circle 410 schematically indicates an uncertainty in the position of the receiver 200 around the point Pa. The uncertainty depends e.g. on the uncertainty of the DOA measurements and the precision of the orbital data available for the satellites 120. If a larger number of signals are used, the DOA measurements from the additional signals may be used to reduce the uncertainty. With reference to Figure 3, larger number of measurements can also be used to determine the orientation of the antenna array 210, 240 relative to the global coordinate system. According to some examples, at least 3 to 4 signals may be used to find the position of the satellite receiver 200. It may be noted that alternative methods of determining the relative position of the receiver 200 to a satellite exists. One such method is to measure the Doppler shift of the signal as the satellite passes the receiver. Based on a time series of measurements of the Doppler shift it is possible to determine at which point the satellite is closest to the receiver 200, and a combination of several such Doppler shift measurements can then be used to estimate the position of the receiver 200.

[0080] Accordingly, the satellite receiver 200 may be arranged to determine the Doppler shift of at least one signal from at least one satellite and to track the position of the receiver 200 relative to the at least one satellite by means of the Doppler shift. However, using the Doppler shift to track the position relative to a satellite may require a longer measurement time as the satellite must pass the receiver 200. Positioning using DOA estimation may therefore be more efficient.

[0081] The satellite receiver 200 may also comprise at least one auxiliary sensor 250. The auxiliary sensor 250 may for example be any of an accelerometer, a gyroscope, a magnetometer, and an altitude sensor. The auxiliary sensor may also comprise a combination of multiple accelerometers and gyroscopes arranged to measure acceleration and rotation in three dimensions, such as in an IMU. Such an IMU may also comprise magnetometers.

[0082] Auxiliary sensor data can be combined with the DOA of satellite signals to reduce the number of satellite signals needed and / or provide improved accuracy and precision. As an example, knowing the altitude of the receiver 200 can enable determining the distance to a satellite once the DOA of the corresponding signal is known. Auxiliary sensors can also be used to determine, at least in part, the relation between the array coordinate system and the global coordinate system shown in Figure 3. For example, an accelerometer can be used to find the vertical by measuring the direction of gravitational acceleration, and methods are known in the art for finding true north using gyroscopes and / or magnetometers. Additionally, if the satellite receiver 200 is in motion while positioning is performed, this motion can be tracked and accounted for.

[0083] Thus, the satellite receiver 200 may be arranged to obtain a measurement data from at least one auxiliary sensor 250, and to estimate the position of the receiver 200 based at least in part on the measurement data.

[0084] According to some aspects, the satellite receiver 200 may be part of a larger unit such as a SATCOM terminal. In this case, the satellite receiver 200 may also be a satellite transceiver and be arranged to also transmit a transmit signal to at least one satellite 120, in addition to receiving signals. According to some examples, the first phased array antenna 210 and / or the second phased array antenna 240 may be arranged to transmit signals in addition to receiving signals. The processing circuitry 212, 242 may then be adapted to this purpose. According to other examples, the satellite receiver 200 may comprise one or more additional antennas configured for transmitting a signal to at least one satellite 120. Preferably, the transmit antennas are also phased array antennas. The transmit antennas may for example be arranged to transmit signals in the Ka and / or Ku frequency bands.

[0085] Figure 5 illustrates an example SATCOM terminal 500. The terminal 500 comprises a housing 510 formed in part by a radome panel 515. The radome panel is formed in a material which allows radio waves to pass without significant attenuation.

[0086] Common materials used for radomes include fiberglass, different types of plastics, or composite materials.

[0087] The terminal 500 has a flat form factor with a rectangularly shaped radome panel having dimensions on the order of 300-600mm by 550-950mm, and preferably about 450mm by 800mm. The radome panel 515 forms an upper lid of the housing 510 on the SATCOM terminal 500.

[0088] The SATCOM terminal 500 can be configured to support communication in, e.g., the Ka and the Ku satellite communication frequency bands. The example terminal shown in Figure 5 is intended for use in outdoor environments, such as on land vehicles and on ships. Thus, ingress protection is important. The housing 510 is a sealed housing, which means that it is dust proof and also resistant to ingress of water. According to a preferred embodiment, the housing, including the radome and the interface 520 is categorized as an IP65 or IP66 sealed housing, which means that the sealed housing is dust proof and resistant to severe water spray and strong waterjets for at least 3 minutes.

[0089] The SATCOM terminal comprises an interface 520 configured to support transfer of data signals to and from the terminal 500, and also electrical power. The interface is a sealed interface that provides ingress protection at the connectors. This can be achieved, e.g., by the use of gaskets at the connectors of the interface 520. Figure 5 also shows the terminal 500 comprising cooling modules 530, fans 540, and a venting valve 550 arranged to equalize pressure inside and outside the housing 510.

[0090] The satellite receiver 200 may also comprise a global navigation satellite system, GNSS, device 260. This is particularly the case if the satellite receiver 200 is part of a larger system or device such as the SATCOM terminal mentioned above.

[0091] Global navigation satellite systems (GNSS) are satellite-based systems that provide geospatial positioning information to receivers on the Earth’s surface. A GNSS uses a specialized constellation of satellites that transmit signals containing precise timing and location data, which can be processed by receivers to determine their position, velocity, and time. Common GNSS systems include GPS, GLONASS, Galileo, and BeiDou. GNSS technology is widely used in e.g. transportation, telecommunications, agriculture, and scientific research.

[0092] The functionality of GNSS systems can be impeded by environmental factors, such as if the GNSS receiver is in a location where the satellite signals are partially or fully blocked. Interference from other signal sources that operate at similar frequencies can also degrade GNSS performance. Furthermore, there is a risk of intentional jamming or spoofing of GNSS signals. Jamming refers to deliberate attempts to cause interference by producing strong signals that drown out the signals from GNSS satellites, while spoofing involves the transmission of signals that emulate satellite signals in order to produce an erroneous position estimate in the GNSS receiver.

[0093] The satellite receiver 200 may be arranged to detect an abnormal condition in the operation of the GNSS device 260. Here, an abnormal condition in the operation of the GNSS device 260 is taken to mean a condition indicating that the GNSS receiver is unable to produce a reliable estimate of the position of the satellite receiver 200. In some cases, this could mean that the GNSS receiver produces no estimate at all, as may be the case if the signals are jammed or physically blocked. In other cases, it may be that the received GNSS signal is abnormally strong or displays other characteristics that indicate a spoofed signal. An abnormal condition may also be detected if the position estimate produced by the GNSS receiver undergoes abrupt changes that cannot be explained by a corresponding movement of the satellite receiver 200. According to some examples, the GNSS receiver 260 may be the default device used to obtain an estimate of the position of the satellite receiver 200. In such a scenario, the satellite receiver 200 may be arranged to start obtaining the DOA-based position estimate using signals from communication satellites in the manner described above only after an abnormal condition of operation is detected in the GNSS device 260.

[0094] According to other examples, the satellite receiver 200 may be configured to continuously produce DOA-based position estimates based on signals from communication satellites also when the GNSS device 260 is functioning normally. This has the advantage of providing redundant position estimates. Furthermore, in such a scenario an abnormal condition of operation in the GNSS device 260 may be detected by comparing the two position estimates. If the position estimate produced by the GNSS device 260 starts to deviate substantially from that produced based on signals from communication satellites, it may indicate the presence of a spoofed GNSS signal or some other error.

[0095] When the GNSS device 260 functions optimally, it provides an estimate of the current time in addition to an estimate of the position. This can be used to provide an improved estimate of the current time even when there is an error in the GNSS device operation. For example, if the satellite receiver 200 comprises another timekeeping device with a known clock drift, this can be used in combination with the last time estimate provided by the GNSS device to determine the current time. The satellite receiver 200 may also comprise a GPS- or GNSS-disciplined oscillator, which may provide accurate timing information for a limited time after the GPS I GNSS signal is lost.

[0096] Figure 7 is a flowchart illustrating a method for operating a satellite receiver 200 for satellite positioning. The satellite receiver 200 comprises a first phased array antenna 210, a control unit 220, and a database 230. The database 230 comprises data relating to an orbit of one or more satellites 120. The method comprises receiving S1 , by the first phased array antenna 210, one or more signals from one or more satellites 120, and determining S3, by the receiver 200, a direction of arrival, DOA, of at least one signal of the one or more signals. The method further comprises finding S5, by the satellite receiver 200, a position of the receiver 200 corresponding to the DOA of the at least one signal given the data relating to orbits of one or more satellites 120.

[0097] According to a preferred alternative, determining S3 a DOA of at least one signal comprises using DOA estimation methods and beamforming methods to extract the DOA from phase differences of the signal at the individual elements of the first phased array antenna 210. It may also be noted that finding a position of the receiver 200 corresponding to the DOA involves the steps of identifying the satellite from which the signal is received based on the information content of the signal, locating a corresponding entry in the database 230, and extracting a current position of the identified satellite using the data in the database 230.

[0098] Extracting the current position of the identified satellite generally comprises obtaining the current time. According to some examples, the current time may be obtained from a timekeeping device or clock with a low degree of clock drift. This first estimate of the current time may be refined e.g. by comparing DOA measurements of signals from multiple satellites.

[0099] The method may also comprise determining S2 a signal quality of each of the one or more signals and comparing the determined signal quality to predetermined signal quality acceptance criteria. Determining the signal quality of each signal may for example comprise determining a signal strength and / or signal SNR. Preferably, determining S3 a direction of arrival is only performed for signals that meet the predetermined signal quality acceptance criteria.

[0100] The satellite receiver 200 may also comprise a second phased array antenna 240, which can also be used to receive satellite signals. Preferably, the second phased array antenna 240 is arranged to receive satellite signals in a different frequency band than the first phased array antenna, as has been described previously. Consequently, the method may also comprise receiving S11 , by the second phased array antenna 240, one or more signals from one or more satellites 120, and determining S31 , by the satellite receiver 200, a DOA of at least one signal of the one or more signals received by the second phased array antenna 240.

[0101] Furthermore, the method may comprise evaluating S21 a signal quality of each of the one or more signals received by the second phased array antenna 240 and comparing it to the predetermined signal acceptance criteria. The signals received by the second phased array antenna 240 that meet the signal acceptance criteria can then be used to find the position of the satellite receiver 200.

[0102] According to some examples, the method comprises obtaining S4 a measurement from at least one auxiliary sensor 250 and finding S51 the position of the satellite receiver 200 based at least in part on the measurement data. Here, the auxiliary sensor may be any of an altitude sensor, one or more accelerometers, one or more gyroscopes, a magnetometer, or any other suitable sensor. Finding S51 the position of the satellite receiver 200 based at least on part on measurement data from the auxiliary sensor may comprise using the auxiliary sensor to find an altitude of the receiver 200 and / or finding an orientation of the first and / or second phased array antennas 210, 240 relative to a global coordinate system.

[0103] According to some alternatives, the satellite receiver 200 comprises a GNSS device arranged to obtain the position of the receiver 200 based on dedicated positioning signals from a GNSS satellite system such as GPS, Galileo, etc. In this case, the method may comprise detecting SO an abnormal condition in the operation of the GNSS device 260 comprised in the receiver 200. An abnormal condition in the operation of the GNSS device 260 may be any condition that impedes the function of the GNSS device. This may include scenarios where signals from GNSS satellites are physically blocked, but also instances of jamming or spoofing as previously described herein. Detecting SO an abnormal condition in the operation of the GNSS device 260 may comprise comparing S01 a position estimation produced by the GNSS device 260 to that produced based on the DOA of at least the first signal, i.e, to the DOA- based position estimate.

[0104] The method may also comprise operating S6 the satellite receiver 200 according to the estimated position of the satellite receiver. This can include displaying the estimated position by means of a graphical user interface, such as the GUI 270 shown in Figure 2. If an abnormal condition of operation of a GNSS device 260 is detected, operating S6 the satellite receiver 200 according to the estimated position may also comprise alerting an operator to the error. The position of the satellite receiver 200 may also be used e.g. for navigation.

[0105] The method may comprise transmitting a transmit signal to at least one satellite, either by means of the first or second phased array antenna 210, 240 or by means of at least one separate transmit antenna. That is, the satellite receiver 200 may be comprised in a satellite communication terminal.

[0106] Optionally, the method may comprise determining a Doppler shift of at least one signal from at least one satellite and to track the position of the satellite receiver 200 relative to the at least one satellite by means of the Doppler shift. This is an alternative method of finding the relative position of the satellite receiver 200 to one or more satellites.

[0107] There is also herein disclosed a computer program comprising program code means for performing the steps of the methods described above, when said program is run on a control system comprising one or more control units. Also, there is disclosed a computer readable medium carrying a computer program comprising program code means for performing the steps of the previously described method, when said program product is run on a control system comprising one or more control units. Additionally, a computer program product comprising such a computer program, and a computer readable storage medium on which the computer program is stored.

[0108] Figure 6 schematically illustrates, in terms of a number of functional units, the components of a control unit 220, 600 according to embodiments of the discussions herein. Processing circuitry 610 is provided using any combination of one or more of a suitable central processing unit CPU, graphics processing unit GPU, tensor processing unit TPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g., in the form of a storage medium 630. The processing circuitry 610 may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA. Particularly, the processing circuitry 610 is configured to cause the control unit 220, 600 to perform a set of operations, or steps, such as the methods discussed in connection to Figure 7, and generally herein. For example, the storage medium 630 may store the set of operations, and the processing circuitry 610 may be configured to retrieve the set of operations from the storage medium 630 to cause the control unit 220, 600 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 610 is thereby arranged to execute methods as herein disclosed.

[0109] The storage medium 630 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0110] The control unit 220, 600 may further comprise an interface 620 for communications with at least one external device. As such the interface 620 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline or wireless communication.

[0111] The processing circuitry 610 controls the general operation of the control unit 220, 600, e.g., by sending data and control signals to the interface 620 and the storage medium 630, by receiving data and reports from the interface 620, and by retrieving data and instructions from the storage medium 630. Other components, as well as the related functionality, of the control node are omitted in order not to obscure the concepts presented herein. Figure 8 shows a satellite transceiver 800 for satellite communication which, among other applications, is particularly well suited for performing satellite positioning according to the methods discussed herein. The satellite transceiver 800 comprises a first transceiver antenna 810 arranged to transmit and / or receive signals in a first frequency band and a second transceiver antenna 840 arranged to transmit and / or receive signals in a second frequency band. The second frequency band is different from the first frequency band. The satellite transceiver 800 also comprises at least a first modem 891 and an antenna control unit 820, where the antenna control unit 820 is arranged to control transmission of a first signal from the first transceiver antenna 810 and transmission of a second signal from the second transceiver antenna 840, and / or to process a signal received by the first transceiver antenna 810 and a signal received by the second transceiver antenna 840.

[0112] The satellite transceiver 800 comprises a single antenna control unit 820 that controls both the first transceiver antenna 810 and the second transceiver antenna 840. This has the advantage of enabling more efficient control over transmission and reception to and from the satellite transceiver 800. Preferably, the first transceiver antenna 810 and / or the second transceiver antenna 840 is a phased array antenna. As previously described, a phased array antenna can be operated so as to transmit a signal in a given direction, where the direction is controlled by controlling the phase of the signal at each antenna element. Conversely, a phased array antenna can also be used to detect the direction of arrival of an incoming signal. This facilitates efficient communication between the transceiver 800 and one or more satellites as well as enabling satellite positioning according to the methods described herein.

[0113] According to some aspects, either the first frequency band or the second frequency band may be any of the Ka and Ku bands. Preferably, one of the frequency bands is the Ka band and the other is the Ku band. As the Ka and Ku bands are used by several communication satellite constellations, this leads to the satellite transceiver 800 being able to communicate with and use signals from a wide range of satellites and satellite constellations.

[0114] The antenna control unit 820 may be arranged to determine an availability of a satellite link in the first and / or second frequency band. That is, the antenna control unit 820 may be arranged to determine if communication with a satellite or satellite constellation is possible in the first frequency band and / or in the second frequency band, as well as in which frequency band the signal quality is highest. This information can then be used to select one of the first and second frequency bands for transmission of a signal. Determining an availability of a satellite link may comprise determining any of a signal strength, a signal-to-noise ratio, and an interference strength.

[0115] Preferably, the satellite transceiver 800 is arranged to transmit and / or receive signals to and from any of satellites in low Earth orbit, LEO, satellites in medium Earth orbit, MEO, or geostationary satellites, GEO.

[0116] According to some aspects, the satellite transceiver 800 is arranged to transmit and / or receive signals simultaneously in the first frequency band and the second frequency band. According to a first example, this is accomplished using the first modem 891 which then comprises a software defined radio, SDR, module 891a arranged to process signals in the first frequency band and the second frequency band. According to a second example, the satellite transceiver comprises a second modem 892. In this example, the first modem 891 is arranged to process signals in the first frequency band and the second modem 892 is arranged to process signals in the second frequency band.

[0117] The satellite transceiver 800 may comprise a third transceiver antenna 813 and a fourth transceiver antenna 843, wherein the third transceiver antenna 813 is arranged to transmit and / or receive signals in the first frequency band and the fourth transceiver antenna 843 is arranged to transmit and / or receive signals in the second frequency band.

[0118] Preferably, either the first transceiver antenna 810 or the third transceiver antenna 813 is arranged to transmit signals in the first frequency band, while the other is arranged to receive signals in the first frequency band. As an example, the first transceiver antenna 810 may be arranged to receive signals in the first frequency band and the third transceiver antenna 813 may be arranged to transmit signals in the first frequency band. Similarly, one of the second transceiver antenna 840 and the fourth transceiver antenna 843 may be arranged to receive signals in the second frequency band while the other transmits signals in the second frequency band.

[0119] In satellite communications, it is common to use a different part of the frequency band for transmitting signals to a satellite than for receiving signals from the satellite. This practice has multiple technical advantages that are well known in the art. Using separate transceiver antennas for sending and receiving allows for adapting the transmit and receive antennas to the specific frequencies used for transmission and reception respectively. According to one example, transmission in the Ka band is performed at frequencies between 27.5 and 31 GHz, while reception in the Ka band is performed at frequencies between 17.7 and 21.2 GHz. In the Ku band, transmission may for example be carried out at 13.75 to 14.5 GHz and reception at 10.7 to 12.75 GHz.

[0120] Preferably, the third transceiver antenna 813 and the fourth transceiver antenna 843 are phased array antennas.

[0121] The satellite transceiver 800 preferably comprises a housing, the housing being arranged to hold at least both the first transceiver antenna 810 and the second transceiver antenna 840. The satellite transceiver 800 may also comprise any of a user interface 870, a global navigation satellite system, GNSS, device 850, and an inertial measurement unit, IMU 860.

[0122] A method for operating a satellite transceiver 800 as described above is shown in Figure 9. The method comprises generating Sb1 , by the antenna control unit 820, a first output signal and a second output signal, modulating Sb2 the first and second output signal, and controlling Sb3, by the antenna control unit 820, the first transceiver antenna 810 to transmit the first output signal and the second transceiver antenna 840 to transmit the second output signal. The method may further comprise controlling Sb4, by the antenna control unit 820, the first transceiver antenna 810 to receive a first input signal and the second transceiver antenna 840 to receive a second input signal, demodulating Sb5 the first and second input signal, and processing Sb6, by the antenna control unit 820, the first and second input signal.

[0123] The method may also comprise determining Sb7, by the antenna control unit 820, an availability of a satellite link in the first and / or second frequency band. It should be noted that the method steps may not always be performed in the order listed, and in particular that determining Sb7 an availability of a satellite link in the first and / or second frequency band may therefore be performed before the steps of generating Sb1 the first and second output signals, or at least before controlling Sb3 the first and second transceiver antennas 810, 840 to transmit the first and second output signals. According to some examples, modulating Sb2 the first and second output signals comprises modulating Sb21 the first and second output signals by a software defined radio, SDR, module 891a comprised in the first modem 891. According to other examples, the method comprises modulating Sb2 the first and second output signals comprises modulating Sb22 the first output signal by the first modem 891 and a second output signal by a second modem 892.

[0124] Demodulating Sb5 the first and second input signals may also comprise demodulating Sb51 the first and second input signals by a software defined radio, SDR, module 891a comprised in the first modem 891. Alternatively, demodulating Sb5 the first and second output signals comprises demodulating Sb52 the first output signal by the first modem 891 and a second output signal by a second modem 892.

[0125] There is also disclosed in connection to the satellite transceiver 800 a computer program comprising program code means for performing the steps of the abovementioned method, when said program is run on a control system comprising one or more control units. There is also disclosed a computer readable medium carrying a computer program comprising program code means for performing the steps of the method when said program product is run on a control system comprising one or more control units, as well as a computer program product comprising such a computer program, and a computer readable storage medium on which the computer program is stored.

Claims

25CLAIMS1. A satellite receiver (200) for satellite positioning, the satellite receiver (200) comprising a first phased array antenna (210), a control unit (220), and a database (230), the database comprising data relating to orbits of one or more satellites (120), the first phased array antenna (210) being arranged to receive one or more signals from one or more satellites (120), the receiver (200) being arranged to determine a direction of arrival, DOA, of at least one signal of the one or more signals, and to estimate a position of the satellite receiver (200) corresponding to the DOA of the at least one signal given the data relating to orbits of one or more satellites (120), the satellite receiver (200) being arranged to determine a signal quality of each of the one or more signals, and to determine the DOA of signals that meet predetermined signal quality acceptance criteria.

2. The satellite receiver (200) according to claim 1 , wherein the first phased array antenna (210) is a two-dimensional phased array antenna.

3. The satellite receiver (200) according to any previous claim, where the first phased array antenna (210) is configured to receive signals within a first frequency band, and wherein the first frequency band is any of the Ka or Ku bands.

4. The satellite receiver (200) according to any previous claim, comprising a second phased array antenna (240), where the first phased array antenna (210) and the second phased array antenna (240) are configured to receive signals in a respective first and second frequency band, and wherein the second frequency band is different from the first frequency band.

5. The satellite receiver (200) according to claim 4, wherein the second frequency band is any of the Ka and Ku bands.

6. The satellite receiver (200) according to any previous claim, comprising at least one auxiliary sensor (250).

7. The satellite receiver (200) according to claim 6, wherein the auxiliary sensor (250) is any of an accelerometer, a gyroscope, a magnetometer, and an altitude sensor.

8. The satellite receiver (200) according to claim 6 or 7, wherein the satellite receiver (200) is arranged to obtain a measurement data from at least one auxiliary sensor (250), and to estimate the position of the satellite receiver (200) at least in part by using the measurement data.

9. The satellite receiver (200) according to any previous claim, comprising a global navigation satellite system, GNSS, device (260).

10. The satellite receiver (200) according to claim 9, where the satellite receiver (200) is arranged to detect an abnormal condition in the operation of the GNSS device (260).11 . The satellite receiver (200) according to any previous claim, further arranged to transmit a transmit signal to at least one satellite (120).

12. The satellite receiver (200) according to any previous claim, further arranged to determine the Doppler shift of at least one signal from at least one satellite and to track the position of the receiver (200) relative to the at least one satellite by means of the Doppler shift.

13. A method for operating a satellite receiver (200) for satellite positioning, the satellite receiver comprising a first phased array antenna (210), a control unit (220), and a database (230), the database (230) comprising data relating to an orbit of one or more satellites (120), the method comprising: receiving (S1), by the first phased array antenna (210), one or more signals from one or more satellites (120), determining (S2) a signal quality of each of the one or more signals and comparing the determined signal quality to predetermined signal quality acceptance criteria, determining (S3), by the receiver (200), a direction of arrival, DOA, of at least one signal of the one or more signals, where the at least one signal meets the predetermined signal quality acceptance criteria, and estimating (S5), by the satellite receiver (200), a position of the receiver (200) corresponding to the DOA of the at least one signal given the data relating to orbits of one or more satellites (120).

14. The method according to any of claims 13, wherein the satellite receiver (200) comprises a second phased array antenna (240), the method comprising1 receiving (S11), by the second phased array antenna (240), one or more signals from one or more satellites (120), and determining (S31), by the satellite receiver (200), a DOA of at least one signal of the one or more signals received by the second phased array antenna (240).

15. The method according to claim 14, comprising evaluating (S21) a signal quality of each of the one or more signals received by the second phased array antenna (240) and comparing it to predetermined signal acceptance criteria.

16. The method according to any of claims 13 to 15, the method comprising obtaining (S4) a measurement from at least one auxiliary sensor (250) and finding (S51) the position of the satellite receiver (200) at least in part by using the measurement data.

17. The method according to any of claims 13 to 16, comprising detecting (SO) an abnormal condition in the operation of a GNSS device (260) comprised in the satellite receiver (200).

18. The method according to claim 17, comprising comparing (S01) a position estimation produced by the GNSS device (260) to an estimated position resulting from the DOA of at least the first signal.

19. The method according to any of claims 13 to 18, comprising operating (S6) the satellite receiver (200) according to the estimated position of the receiver.

20. The method according to any of claims 13 to 19, comprising transmitting a transmit signal to at least one satellite.

21. The method according to any of claims 13 to 20, comprising determining a Doppler shift of at least one signal from at least one satellite and to track the position of the satellite receiver (200) relative to the at least one satellite by means of the Doppler shift.

22. A computer program comprising program code means for performing the steps of any of claims 13 to 21 , when said program is run on a control system comprising one or more control units.

23. A computer readable medium carrying a computer program comprising program code means for performing the steps of any of claims 13 to 21 , when said program product is run on a control system comprising one or more control units.

24. A computer program product comprising a computer program according to claim 22, and a computer readable storage medium on which the computer program is stored.

25. A satellite transceiver (800) for satellite communication, the satellite transceiver (800) comprising a first transceiver antenna (810) arranged to transmit and / or receive signals in a first frequency band and a second transceiver antenna (840) arranged to transmit and / or receive signals in a second frequency band, the second frequency band being different from the first frequency band, the satellite transceiver (800) also comprising at least a first modem (891), and an antenna control unit (820), the antenna control unit (820) being arranged to control transmission of a first signal from the first transceiver antenna (810) and transmission of a second signal from the second transceiver antenna (840), and / or to process a signal received by the first transceiver antenna (810) and a signal received by the second transceiver antenna (840).

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