Signal processing chain for GNSS receiver to process signal received by antenna array and distribute the signal to GNSS receiver

Abstract

To distribute navigation satellite signals received by an antenna array to at least three GNSS receivers that receive different frequency channels with the lowest possible insertion loss, inter-band aliasing, and group delay.SOLUTION: A signal processing chain for a GNSS receiver includes a diplexer 4 that divides signals received by an antenna array 1 to main paths 13, 14, and a Wilkinson distributor 7 that divides signals in the main path 13 to sub paths 15, 16. GNSS receivers 91, 92, 93 are connected to the sub path 15, the sub path 16, and the main path 14, respectively. The diplexer 4 is configured such that at least two different frequency channels of the GNSS receivers 91, 92 are transmitted to the main path 13. The pass-band width of band-pass filters 61, 62 connected to the main paths 13, 14 is set in consideration of at least one GNSS receiver on the downstream side. Low-pass filters 3, 51, 52 connected to the main paths 13, 14 can reduce the high-frequency interference components of the received signals.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Conventional technology The present invention relates to a signal processing chain for a GNSS receiver for processing and distributing signals received by an antenna array to at least three GNSS receivers, in particular to a GNSS receiver and position location system comprising such a signal processing chain, as well as to a method for processing and distributing GNSS signals received by an antenna array. [Background technology]

[0002] Global Navigation Satellite System (GNSS) is a system for locating and navigating on the ground and in the air by receiving navigation satellite signals. Navigation satellite signals contain positioning information encoded on specific carrier frequencies. For highly accurate location, multi-frequency systems are currently used, which simultaneously receive multiple navigation satellite signals on different carrier frequencies.

[0003] In today's GNSS receivers, navigation satellite signals are typically received by an antenna array and then reach the GNSS receiver via a signal processing chain. To implement a multi-frequency system, it is desirable to have a signal processing chain that is compatible with navigation satellite signals at different carrier frequencies, processes these navigation satellite signals with the lowest possible insertion loss, inter-band aliasing, and group delay, and then distributes each navigation satellite signal to the appropriate GNSS receiver.

[0004] Additionally, it would be desirable to have a compactly structured multi-frequency GNSS receiver that simultaneously receives navigation satellite signals at different carrier frequencies. Summary of the Invention [Means for solving the problem]

[0005] Disclosure of the Invention Based on this, a signal processing chain for a GNSS receiver device is described for frequency selectively processing and distributing signals received by an antenna array to at least three GNSS receivers for receiving different frequency channels, wherein: the signal processing chain comprises a common input for signals received by the antenna array, a first signal splitting unit having a diplexer for splitting the signals into a first main path and a second main path, and a second signal splitting unit having a Wilkinson splitter for splitting the signals from the first main path into a first sub-path and a second sub-path, wherein the first GNSS receiver is connected to the first sub-path, the second GNSS receiver is connected to the second sub-path, and the third GNSS receiver is connected to the second main path; the diplexer is configured so that at least two different frequency channels for the first GNSS receiver and the second GNSS receiver are transmitted on the first main path; - one band-pass filter is connected to each of the first main path and the second main path, and the pass bandwidth of the band-pass filter is set taking into account at least one GNSS receiver connected downstream of the band-pass filter; A low-pass filter is further connected to each of the first main path and the second main path, and the low-pass filter is capable of suppressing high-frequency interference components of the signals received by the antenna array.

[0006] The described signal processing chain can be particularly well used in the RF front end of a GNSS receiver, in particular a three-frequency GNSS receiver, to frequency-selectively process signals received by an antenna array and distribute the processed signals frequency-selectively to the GNSS receiver of the GNSS receiver.

[0007] Currently, the following Global Navigation Satellite Systems (GNSS) are available: -NAVSTAR GPS (Global Positioning System) in the United States - GLONASS (Global Navigation Satellite System) of the Russian Federation -Galileo of the European Union -Beidou of the People's Republic of China is available.

[0008] Each GNSS includes multiple GNSS satellites, each of which emits a GNSS satellite signal at a fixed carrier frequency in the form of electromagnetic waves. For example, a GPS satellite can emit a GPS satellite signal at the L1-carrier frequency (1575.42 MHz) or the L2-carrier frequency (1227.60 MHz).

[0009] Furthermore, satellite-based augmentation systems (SBAS) are now available that can support GNSS. SBAS provide additional information, in particular corrections related to GNSS, which can improve the reliability, accuracy and availability of position determination. These corrections are also often emitted in the form of electromagnetic waves at fixed carrier frequencies from geostationary satellites. Such corrections in the form of electromagnetic waves will be referred to below as GNSS correction signals.

[0010] To determine a position with high accuracy, a GNSS receiver can receive and evaluate GNSS satellite signals and GNSS correction signals at different carrier frequencies, for example, GPS satellite signals at the L1-carrier frequency and GPS satellite signals at the L2-carrier frequency, as well as GPS correction signals at the L-carrier frequency.

[0011] In order to compactly structure the GNSS receiver, it is proposed here to receive GNSS satellite signals and GNSS correction signals at different frequencies by a common antenna array. Therefore, the signals received by the antenna array may contain different frequency components (e.g., L1+L2+L). In the following, the signals received by the antenna array will be referred to as antenna signals.

[0012] Preferably, in order to decode the positioning information or correction information encoded at a fixed carrier frequency, an antenna signal containing different frequency components (e.g., L1+L2+L) is split into partial signals each containing a portion of the entire frequency spectrum of the original antenna signal (e.g., L1 or L2 or L).

[0013] The signal processing chain is mainly used here to split the antenna signal containing various frequency components into partial signals and distribute these partial signals to the respective GNSS receivers, each partial signal containing only one frequency component containing one positioning or correction information at the input to the GNSS receiver. In this case, the number of GNSS receivers may be the same as the number of partial signals. Each GNSS receiver therefore receives only partial signals with fixed frequency components, which are input to a control device for, for example, decoding and / or evaluating the positioning or correction information contained in the partial signals. Each GNSS receiver can be structurally and functionally designed according to the partial signals it receives.

[0014] The signal processing chain is coupled between the antenna array and the GNSS receiver of the GNSS receiving device and includes an input for receiving signals from the antenna array, a first signal splitter, a second signal splitter, and multiple outputs for connecting the individual GNSS receivers. The input of the signal processing chain is directly connected downstream of the antenna array and configured as a common input for antenna signals at different frequencies. The input may optionally be provided with a DC power feed. Weak antenna signals may be amplified for further processing and / or noise components of the antenna signals may be suppressed. The first and second signal splitters of the signal processing chain are connected downstream of the common input and form multiple frequency channels for transmitting the split partial signals separately from each other. The multiple outputs are coupled to the GNSS receiver. Preferably, only partial signals having frequency components containing positioning information or correction information are present at each output.

[0015] The first signal splitting unit is structurally and functionally different from the second signal splitting unit, and is connected upstream of the second signal splitting unit.

[0016] The first signal splitting unit includes the diplexer described above, which is connected downstream of the input side and splits the signal into a first main path and a second main path, and can initially split an antenna signal containing different frequency components (e.g., L1+L2+L) into two partial signals at the two outputs of the diplexer. In this case, each of the two partial signals contains a part of the entire original frequency spectrum. For example, if the antenna signal contains L1-, L2-, and L-frequency components, it can be assumed that a partial signal containing L1- and L-frequency components appears at one output of the diplexer, and a partial signal containing L2-frequency components appears at the other output.

[0017] The second signal splitting unit may include a Wilkinson splitter, which may be connected downstream of the output side of the diplexer and further splits the partial signal present in the first main path into a first sub-path and a second sub-path. For example, it may be assumed that a partial signal having L1- and L-frequency components present at the output side of the diplexer is further split into two further partial signals by a Wilkinson splitter connected downstream of this output side, one partial signal containing the L1-frequency component and the other partial signal containing the L-frequency component.

[0018] The partial signals at the two outputs of the diplexer have a frequency spectrum that is broader than the desired carrier frequency. Therefore, the carrier frequency must be filtered out of this frequency spectrum. This is achieved by using band-pass filters. A band-pass filter may then be connected downstream of each output of the diplexer, with a passband width that corresponds to the frequency components of the partial signals present at that output that contain the localization information and / or correction information. Therefore, the frequency components of the partial signals that are above the passband width and those that are below the passband width can be at least partially filtered out by the band-pass filters.

[0019] However, bandpass filters are usually unable to suppress high-frequency interference components, especially those above 4 GHz. For this purpose, at least one low-pass filter is connected upstream or downstream of each bandpass filter to suppress such high-frequency interference components. It is particularly advantageous if at least one low-pass filter is connected upstream of each bandpass filter. Here, for example, a low-pass filter may be provided on the common input side and upstream of the diplexer. This low-pass filter is then used as a common low-pass filter for each bandpass filter. It is also possible to provide low-pass filters downstream of the diplexer and upstream of each bandpass filter. This low-pass filter is then used as an individual low-pass filter for each bandpass filter, with its parameters individually designed for the associated bandpass filter.

[0020] The signal processing chain described as an RF front end can be particularly advantageously integrated into a high-precision triple-frequency GNSS receiver, which is particularly suitable for GNSS-aided positioning systems for the positioning and navigation of vehicles, especially autonomously driven automobiles.

[0021] The described signal processing chain ensures the lowest possible insertion loss and group delay of GNSS satellite signals and GNSS correction signals within the upper and lower GNSS frequency bands, i.e., 1525 MHz to 1606 MHz or 1196 MHz to 1251 MHz, and filtering of out-of-band interference components.

[0022] The described signal processing chain is particularly advantageous for processing antenna signals up to 6 GHz. The use of a low-pass filter is particularly advantageous for suppressing high-frequency interference components above 4 GHz that cannot be suppressed by a band-pass filter. By using first and second signal splitting units connected in series, only two band-pass filters are required for at least three GNSS receivers. This reduces inter-band aliasing compared to using three band-pass filters for three GNSS receivers.

[0023] By using the described signal processing chain, it is possible to adapt at least three GNSS receivers as needed independently of each other and to connect them in a data-conducting manner to a common antenna array via DC-decoupling capacitors.

[0024] Preferably, each bandpass filter is configured conjugately with two lowpass filters, where one lowpass filter is connected upstream of the diplexer for first-order suppression and the other lowpass filter is connected downstream of the diplexer for second-order suppression of high-frequency interference components.

[0025] In this case, one low-pass filter can be connected directly downstream of the antenna array and upstream of the diplexer at the common input of the signal processing chain as a common low-pass filter. This allows high-frequency interference components of the antenna signals to be suppressed once upstream of the diplexer. This improves and facilitates the first signal division using the diplexer. Particularly preferably, additional low-pass filters are connected downstream of the diplexer and upstream of each band-pass filter. This allows high-frequency interference components that cannot be suppressed by the common low-pass filter to be suppressed again in a relatively narrow frequency band by the additional low-pass filters. This is particularly advantageous for subsequent signal processing.

[0026] Preferably, the bandpass filter is a SAW filter. Surface acoustic wave filters (SAW filters) can be used in the frequency range from approximately 35 MHz to approximately 3000 MHz and can be used particularly advantageously in the described signal processing chains due to their small dimensions, low insertion loss, high reliability and high mechanical stability.

[0027] Preferably, the low-pass filter connected upstream of the diplexer is a π-low-pass filter. This π-low-pass filter may be connected downstream of the phantom feed of the antenna array, in particular downstream of the DC decoupling capacitor for the phantom feed. The π-low-pass filter consists of one coil and two capacitors, and their parameters can be designed to block as many frequency components as possible that exceed the upper limit of the GNSS frequency band of all GNSS receivers connected downstream.

[0028] Alternatively, the low-pass filter connected downstream of the diplexer is preferably an LC low-pass filter, which is composed of one coil and one capacitor, and the parameters of these components can be designed to block frequency components exceeding the passband width of the SAW filter connected downstream of the LC low-pass filter.

[0029] Preferably, the diplexer and the Wilkinson splitter each have two outputs, with the Wilkinson splitter connected downstream of the diplexer output. This allows for only two SAW filters to be required for at least three receivers, resulting in less inter-band aliasing than if three SAW filters were used for three receivers.

[0030] Furthermore, a GNSS receiving device is proposed that includes an antenna array, at least three GNSS receivers and the above-mentioned signal processing chain, where the signal processing chain is coupled between the antenna array and the at least three GNSS receivers and is capable of processing signals received by the antenna array and distributing them to the at least three GNSS receivers.

[0031] Preferably, the at least three GNSS receivers differ from one another in terms of bandwidth.

[0032] Here, the GNSS receiver may be configured as a triple-frequency GNSS receiver in order to receive and process GNSS navigation signals and GNSS correction signals at three different carrier frequencies. For this purpose, three receivers may be provided, each capable of receiving an antenna signal at a specific carrier frequency. For example, one receiver may be designed to have a frequency bandwidth between 1560 MHz and 1609 MHz for receiving GPS signals at the L1-carrier frequency, one receiver to have a frequency bandwidth between 1196 MHz and 1251 MHz for receiving GPS signals at the L2-carrier frequency, and one receiver to have a frequency bandwidth between 1525 MHz and 1559 MHz for receiving GPS correction signals at the L-carrier frequency. This allows the location to be determined with higher accuracy based on the so-called triple-frequency method.

[0033] Preferably, the antenna array is electrically powered and is capable of receiving GNSS signals at different frequencies.

[0034] The antenna array may be configured as an active antenna with a low noise amplifier (abbreviated as LNA). This LNA may be supplied with a direct current by a phantom power supply. This allows weak antenna signals to be amplified by 20 dB to 30 dB, taking into account the thermal noise level. The signal processing chain can therefore process the antenna signals with optimal strength, e.g., above 40 dB. Additionally, a DC-decoupling capacitor may be provided at the input of the signal processing chain to decouple the direct current.

[0035] Furthermore, a vehicle positioning system is proposed that includes the above-mentioned GNSS receiver.

[0036] Furthermore, a method is proposed for processing a signal received by an antenna array and distributing the processed signal to at least three GNSS receivers using the above-mentioned signal processing chain, in which the signal received by the antenna array is split by a diplexer and then split by a Wilkinson splitter connected downstream on the output side of the diplexer into at least three partial signals so that each partial signal contains frequency components of the entire frequency spectrum of the original signal received by the antenna array and includes the GNSS carrier frequency that is filtered out by a SAW filter, in which high-frequency interference components that cannot be suppressed by the SAW filter are suppressed by at least one low-pass filter.

[0037] In the following, the present invention and technical environment will be described based on the drawings. It should be noted that the drawings are schematic in nature. It should also be noted that the features shown in the drawings do not necessarily have to be used in the illustrated combinations, but rather partial features can be extracted and combined with other descriptions in the specification and / or other drawings. This is only true if the combination of essential features is explicitly shown in this specification. [Brief explanation of the drawings]

[0038] [Figure 1] FIG. 1 shows a schematic and exemplary signal processing chain for a GNSS receiver. DETAILED DESCRIPTION OF THE INVENTION

[0039] The GNSS receiving device includes an antenna array 1, three GNSS receivers 91, 92, and 93, and a signal processing chain that includes a π-low-pass filter 3, a diplexer 4, two LC-low-pass filters 51 and 52, two SAW filters 61 and 62, a Wilkinson splitter 7, and an RF matching circuit 8.

[0040] The antenna array 1 can receive GNSS signals at carrier frequencies in the L1-, L2-, or L-frequency band. In this case, GNSS signals at carrier frequencies in the L1-frequency band can reach the L1-GNSS receiver 91 via a signal processing chain, GNSS signals at carrier frequencies in the L2-frequency band can reach the L2-GNSS receiver 93 via a signal processing chain, and GNSS signals at carrier frequencies in the L-frequency band can reach the L-GNSS receiver 92 via a signal processing chain. The L1-frequency band is between 1560 MHz and 1609 MHz. The L2-frequency band is between 1196 MHz and 1251 MHz. The L-frequency band is between 1525 MHz and 1559 MHz. In this case, the L1-GNSS receiver 91 is suitable for receiving GNSS satellite signals at the L1-carrier frequency. The L2-GNSS receiver 93 is suitable for receiving GNSS satellite signals at the L2-carrier frequency. The L-GNSS receiver 92 is suitable for receiving GNSS correction signals at the L-frequency.

[0041] The frequency spectrum of the signals received by the antenna array 1 may include the L1-frequency band and / or the L2-frequency band and / or the L-frequency band and high frequency interference components.

[0042] The signal processing chain is used to split the signal received by the antenna array 1 into partial signals each having one of the above-mentioned frequency bands, distribute these partial signals to corresponding GNSS receivers 91, 92, 93, and suppress high-frequency interference components.

[0043] The signals received by the antenna array 1 are first filtered by a π-low-pass filter 3, which blocks frequency components above the upper limits of the L1-, L2- and L-frequency bands, i.e., above 1609 MHz, thereby minimizing high-frequency interference components.

[0044] Subsequently, the signal filtered by the π-low-pass filter 3 is split by the diplexer 4 into two partial signals at the two outputs of the diplexer 4, into a first main path 13 and a second main path 14, where one partial signal comprises the L1- and / or L-frequency bands and the other partial signal comprises the L2-frequency band.

[0045] The partial signal having the L1- and / or L-frequency band is first filtered by an LC-low-pass filter 51 and then by a SAW filter 61. In this case, frequency components above the upper limit of the L1- and L-band (i.e., above 1609 MHz) are blocked by the LC-filter 51, and the L1- and / or L-frequency band is filtered by the SAW filter 61. Furthermore, the LC-filter 51 can again suppress high-frequency interference components that were not suppressed by the π-low-pass filter 3. Subsequently, this partial signal is further split by a Wilkinson splitter 7 (in the first main path 13) into two partial signals, a first sub-path 15 and a second sub-path 16. One of these partial signals contains only the L1-frequency band and reaches the L1-GNSS receiver 91 via the RF matching circuit 8. The other partial signal contains only the L-frequency band and reaches the L-GNSS receiver 92 via the RF matching circuit 8.

[0046] The partial signal having the L2-frequency band is first filtered by the LC-low-pass filter 52 and then by the SAW filter 62, where frequency components above the upper limit of the L2-frequency band (i.e., above 1251 MHz) are blocked by the LC-filter 52, and the L2-frequency band is filtered by the SAW filter 62. Subsequently, this partial signal reaches the L2-GNSS receiver 93 via the RF matching circuit 8.

[0047] The antenna array 1 can be supplied with a DC current by a phantom power supply 2. For DC decoupling, a DC-decoupling capacitor 10 is provided, which is connected downstream of the antenna array 1 and upstream of the π-low-pass filter 3.

[0048] The signal processing chain is particularly advantageous for processing signals received by the antenna array 1 up to 6 GHz. The use of the π-low-pass filter 3 and the LC-low-pass filters 51, 52 is particularly advantageous for suppressing high-frequency interference components above 4 GHz that cannot be suppressed by the SAW filters 61, 62. By using the diplexer 4 and the Wilkinson splitter 7, only two SAW filters 61, 62 are required for the three GNSS receivers 91, 92, 93. This reduces inter-band aliasing compared to using three band-pass filters for the three GNSS receivers 91, 92, 93. By using this signal processing chain, the three GNSS receivers 91, 92, 93 can be adapted as needed independently of each other and can be connected to the common antenna array 1 in a data-conductive manner via the DC-decoupling capacitor 10. This allows for a compact and flexible construction of a GNSS receiver with the described signal processing chain.

[0049] The described signal processing chain ensures filtering of out-of-band interference components with the lowest possible insertion loss and group delay. The described signal processing chain can be particularly advantageously integrated into a high-precision triple-frequency GNSS receiver. A triple-frequency GNSS receiver with such a signal processing chain is particularly suitable for GNSS-aided positioning systems for the positioning and navigation of vehicles, in particular autonomously driven automobiles.

Claims

1. A signal processing chain for a GNSS receiver for frequency-selectively processing signals received by an antenna array (1) and distributing them to at least three GNSS receivers (91, 92, 93) for receiving different frequency channels, comprising: the signal processing chain comprises a common input for the signals received by the antenna array (1), a first signal splitter having a diplexer (4) for splitting the signals into a first main path (13) and a second main path (14), and a second signal splitter having a Wilkinson splitter (7) for splitting the signals from the first main path (13) into a first sub-path (15) and a second sub-path (16), a first GNSS receiver (91) being connected to the first sub-path (15), a second GNSS receiver (92) being connected to the second sub-path (16), and a third GNSS receiver (93) being connected to the second main path (14); - the diplexer (4) is configured so that at least two different frequency channels for the first GNSS receiver (91) and the second GNSS receiver (92) are transmitted to the first main path; a band-pass filter (61, 62) is connected to each of the first main path (13) and the second main path (14), and the passband width of the band-pass filter (61, 62) is set taking into account at least one GNSS receiver (91, 92, 93) connected downstream of the band-pass filter; a signal processing chain, further comprising one low-pass filter (3, 51, 52) connected to each of the first main path (13) and the second main path (14), said low-pass filters (3, 51, 52) being capable of suppressing high-frequency interference components of the signals received by the antenna array (1).

2. 2. A signal processing chain according to claim 1, wherein a low-pass filter (3) is connected upstream of the diplexer (4).

3. 2. The signal processing chain of claim 1, wherein each of the bandpass filters (61, 62) is a SAW filter (61, 62).

4. 2. The signal processing chain according to claim 1, wherein the low-pass filter (3) connected upstream of the diplexer (4) is a π-low-pass filter (3).

5. 2. The signal processing chain according to claim 1, wherein the low-pass filters (51, 52) connected downstream of the diplexer (4) in the first main path (13) and the second main path (14) are LC-low-pass filters (51, 52).

6. 6. A GNSS receiving device comprising an antenna array (1), at least three GNSS receivers (91, 92, 93), and a signal processing chain according to any one of claims 1 to 5, wherein the signal processing chain is coupled between the antenna array (1) and the at least three GNSS receivers (91, 92, 93) and is capable of processing signals received by the antenna array (1) and distributing them to the at least three GNSS receivers (91, 92, 93).

7. 7. The GNSS receiving device according to claim 6, wherein the at least three GNSS receivers (91, 92, 93) differ from one another in terms of frequency bandwidth.

8. GNSS receiving device according to claim 6, wherein the antenna array (1) is powered by an electric current and is capable of receiving GNSS signals at different frequencies.

9. A vehicle positioning system including the GNSS receiving device according to claim 6.

10. 6. A method for processing signals received by an antenna array and distributing the processed signals to at least three GNSS receivers (91, 92, 93) using a signal processing chain according to any one of claims 1 to 5, comprising: The signal received by the antenna array (1) is split by a diplexer (4), and then split into at least three partial signals by a Wilkinson splitter (7) connected downstream of the output side of the diplexer (4) so ​​that each partial signal contains frequency components of the entire frequency spectrum of the original signal received by the antenna array (1) and includes a GNSS-carrier frequency that is filtered by SAW filters (61, 62); The method, wherein high frequency interference components not suppressible by the SAW filters (61, 62) are suppressed by at least one low pass filter (3, 51, 52).

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