Patent Description:
A global navigation satellite system (GNSS) receiver receives a satellite signal transmitted from a GNSS satellite constellation through an antenna. Before arrival at the antenna, the satellite signal may be scattered, reflected, or refracted in space, for example, by mountains or buildings, causing multipath interference at the antenna. Or the antenna may suffer from a spoofing attack that deceives the receiver with false signals. Or the antenna may suffer from noise broadcasted from a jamming device on the same frequency used by one or more satellites of the GNSS satellite constellation.

Multipath interference, spoofing, and jamming may be mitigated by null steering in which the GNSS receiver steers away from an unwanted signal in one direction and focuses on another direction. Null steering may be accomplished by adding hardware (e.g., a multi-antenna array) in the receiver's frontend and additional signal processing blocks in the receiver's backend. However, this increases the size and cost of the receiver. For example, <CIT> discloses a GNSS receiver with a plurality of antennas. A multiplexer switch is connected to the antennas and controlled by a control signal generator in such a way as to cyclically select the signals produced by the antennas one at a time and to multiplex samples of the signals produced by the antennas in a time-multiplexed signal.

According to some embodiments of the present disclosure, there is provided an apparatus according to claim <NUM>.

According to some embodiments of the present disclosure, there is also provided a method for operating a device, according to claim <NUM>.

According to some embodiments of the present disclosure, there is further provided a computer program according to claim <NUM>. The computer program may be stored in a computer readable medium. The computer readable medium may be non-transitory.

Instead, they are merely examples of systems, apparatuses, and methods consistent with aspects related to the present disclosure as recited in the appended claims.

Multipath interference causes severe problems in GNSS navigation solutions, especially in a complex propagation environment (e.g., mountains, buildings, urban canyons, foliage, etc.). A GNSS satellite transmits a right hand circularly polarized (RHCP) electromagnetic wave. However, in a complex propagation environment, the direction of rotation of the electric field vector of the RHCP electromagnetic wave can be changed due to an interaction of the electromagnetic wave with the environment. This may cause difficulty in determining polarization of the electromagnetic wave transmitting in a complex propagation environment.

Spoofing attacks or jamming attacks are another challenge in GNSS navigation solutions. For example, a spoofing signal transmitted from an unknown source attempts to deceive a GNSS receiver. A jamming signal transmitted on the same frequency as a signal transmitted by a GNSS satellite deteriorates the ability of a GNSS receiver to receive the GNSS satellite signal. Accordingly, multipath interference, spoofing, and jamming are significant threats to autonomous vehicles that rely on trustworthy global position information.

Multipath interference, spoofing, and jamming in a GNSS receiver may be mitigated by null steering or beam steering in which the GNSS receiver blocks unwanted signals from one direction or focuses on desired signals from another direction. Null steering (or beam steering) may be accomplished by adding hardware in the receiver's frontend, for example, using a multiple-antenna array, and additional signal processing blocks in the receiver's backend. However, this increases the size of the system and adds cost to the system design. Moreover, null steering may only be performed globally, that is, the null steering is simultaneously applied to all satellites signals, thereby affecting accuracy and flexibility of the mitigation.

Embodiments of the present disclosure provide an apparatus including an antenna assembly and a receiver. The antenna assembly includes an antenna having a plurality of feed points that generate a plurality of corresponding polarized signals having respective polarization directions different from each other. The antenna assembly also includes a switching circuit including a switch that periodically switches between the plurality of feed points to select a corresponding one of the polarized signals among the plurality of polarized signals at a point in time to form a time-division multiplexed signal. The receiver generates a switching signal that controls the switch in the antenna assembly. The time-division multiplexed signal is filtered and amplified in the antenna assembly and then transmitted to the receiver. The receiver processes the time-division multiplexed signal in the digital domain and then controls generation of the switching signal based on the processing. For example, the receiver determines a desired amplitude and a desired phase for each of the plurality of polarized signals, and assigns a complex weight to each of the plurality of polarized signals based on the determined desired amplitude and phase for each of the polarized signals. The receiver includes a correlator having a plurality of correlator channels. Each of the plurality of correlator channels is assigned to a different one of a plurality of signals respectively transmitted from a plurality of different satellites. Each of the plurality of correlator channels independently processes a corresponding one of the plurality of satellite signals.

Embodiments disclosed herein have one or more technical effects. By using a switch in order to switch between the plurality of antenna feed points, time-division multiplexing the plurality of signals having different polarization directions, and processing the time-division multiplexed signal in the digital domain in the receiver, a need for recombining the polarized signals using hardware in the RF domain is eliminated, leading to a reduced size, a reduced cost, and reduced power consumption of the receiver. Performing filtering and amplification of the time-division multiplexed signal in the antenna assembly, rather than in the receiver, provides enhanced immunity of the operation to temperature fluctuation. By determining the desired phase and the desired amplitude for each of the plurality of polarized signals and assigning the complex weight including the desired phase and the desired amplitude to each of the plurality of polarized signals, null steering is accomplished during correlation of the signals. By assigning each of the plurality of correlator channels to a different one of the plurality of signals respectively transmitted from a plurality of different satellites and applying the complex weight individually to each signal in each of the plurality of correlator channels, null steering is performed individually for each of the satellite signals, leading to enhanced accuracy of mitigation of multipath interference, jamming, and spoofing.

<FIG> is a schematic diagram illustrating an apparatus <NUM> including an antenna assembly and a receiver, consistent with some embodiments of the present disclosure. Referring to <FIG>, apparatus <NUM> includes an antenna assembly <NUM>, a receiver <NUM>, and an antenna cable <NUM> that connects antenna assembly <NUM> and receiver <NUM>. Antenna assembly <NUM> includes an antenna <NUM> and a switching circuit <NUM>. Antenna <NUM> is configured to receive a GNSS signal <NUM>. In an embodiment, GNSS signal <NUM> may be a single satellite band signal transmitted from a single satellite. The single satellite signal may have a corresponding pseudo-random noise (PRN) code. In another embodiment, GNSS signal <NUM> may include a plurality of satellite signals respectively transmitted from a plurality of satellites, and each of the plurality of satellite signals may have a corresponding PRN code. In an embodiment, GNSS signal <NUM> may also include signals originating from one or more virtual sources that reflect and/or scatter satellite signals. In an embodiment, GNSS signal <NUM> may include satellite signals reflected at an interface between two mediums. However, the signals received by antenna <NUM> are not limited to satellites signals, and can be any electromagnetic waves transmitted from any sources, for example, wireless cellular signals.

Antenna <NUM> includes a first feed point (not shown) that generates a first polarized signal <NUM>, a second feed point (not shown) that generates a second polarized signal <NUM>, and a third feed point (not shown) that generates a third polarized signal <NUM>. In an embodiment, polarization of first polarized signal <NUM>, second polarized signal <NUM>, and third polarized signal <NUM> may form three orthogonal modes, for example, transverse magnetic <NUM> (TM01) mode, transverse magnetic <NUM> (TM10) mode, and transverse magnetic <NUM> (TM11) mode. However, the number of the feed points in antenna <NUM> is not limited to three, and can be any other number, for example, two or any number greater than three. Antenna <NUM> may be any antenna (e.g., a patch antenna, a helix antenna, a crossed bow antenna, orthogonally placed monopole antennas, etc.) that can have a plurality of feed points.

Polarization at the plurality of feed points in antenna <NUM> may be described using complex vectors (i.e., polarization vectors) representing directions of the electric field. For a number of feed points that is three, the polarization vectors may be configured so that they can be orthogonal to each other. For a number of feed points that is greater than three, the polarization vectors may be configured so that they can be orthogonalized to achieve a vector rank of three.

Switching circuit <NUM> includes a switch <NUM> that periodically switches between the first feed point, the second feed point, and the third feed point to select, for sampling, a polarized signal from each of first polarized signal <NUM>, second polarized signal <NUM>, and third polarized signal <NUM> at points in time, to form a time-division multiplexed signal. As a result, the time-division multiplexed signal is a combination of the sampled first polarized signal <NUM>, the sampled second polarized signal <NUM>, and the sampled third polarized signal <NUM> that form a single signal path. The switching may be done at a rate sufficiently high for the sampled signals to be recoverable by signal processing at receiver <NUM>. For example, a switching period may be less than <NUM>. The switching in switch <NUM> is controlled by a switching signal that is generated by a switching signal generator <NUM> of receiver <NUM> and transmitted via antenna cable <NUM>.

Switching circuit <NUM> may include a switching signal detector <NUM> that detects the switching signal. Switching signal detector <NUM> can be selected based on a type of the switching signal. For example, if the switching signal consists of different amplitude levels, a comparator can be used as the switching signal detector.

Switching circuit <NUM> may include a low noise amplifier (LNA) <NUM> that is coupled to switch <NUM> and configured to amplify the time-division multiplexed signal. LNA <NUM> may be supplied with a direct current (DC) bias provided by receiver <NUM>. A low pass filter (LPF) <NUM> may be implemented in the path of the DC bias so that the switching signal, which is superimposed on the DC bias, can be filtered out before the DC bias is supplied to LNA <NUM>. In an embodiment, LNA <NUM> may include a controller that controls parameters of an amplified signal. The parameters may include at least one of: gain, noise, linearity, bandwidth, output dynamic range, slew rate, rise rate, overshoot, or stability factor.

Switching circuit <NUM> may include a bandpass filter (BPF) <NUM> that is coupled to LNA <NUM> and configured to filter the amplified signal to suppress frequencies outside a range of interest. The filtered and amplified time-division multiplexed (TDM) signal is then transmitted to receiver <NUM>, via antenna cable <NUM> and shown as a TDM signal <NUM>, for further processing in the digital domain by receiver <NUM>.

Antenna cable <NUM> electrically connects antenna assembly <NUM> and receiver <NUM> to transmit time-division multiplexed signal from antenna assembly <NUM> to receiver <NUM>, and the switching signal and the DC bias signal from receiver <NUM> to antenna assembly <NUM>. Antenna cable <NUM> may be a coaxial RF cable or any other cable suitable for transmitting an RF signal.

By using a switch in order to switch between the multiple antenna feed points and time-division multiplex the signals having different polarization directions, and processing the time-division multiplexed signal in the digital domain at the receiver, a need for recombining the different polarized signals in the RF domain is eliminated. This allows for a reduced size, a reduced cost, and reduced power consumption of apparatus <NUM>. In addition, performing filtering and amplification of the time-division multiplexed signal on the antenna side and digitally processing the signal at the receiver, provides enhanced immunity of the signal reception and processing to temperature fluctuation.

In an embodiment, at least one of LNA <NUM> and BPF <NUM> may be implemented in the receiver side, rather than in the antenna side. In another embodiment, both receiver <NUM> and antenna assembly <NUM> include an LNA and a BPF.

Receiver <NUM> includes a bias tee (bias T) circuit <NUM> that provides the DC bias signal that is superimposed on the switching signal and transmitted to LNA <NUM> of switching circuit <NUM> of antenna assembly <NUM> via antenna cable <NUM>.

Receiver <NUM> includes switching signal generator <NUM> that generates the switching signal that drives switching circuit <NUM> of antenna assembly <NUM>. Switching signal generator <NUM> may be a pulse signal generator or an AC signal generator. The switching signal may be a synchronized signal formed by mixing a signal generated by switching signal generator <NUM> with a local oscillating signal provided by a local oscillator (not shown). A switching period may be in the order of <NUM>.

In an embodiment, the generated switching signal includes a plurality of signals having respective frequencies different from each other. Each of the plurality of polarized signals is provided with a corresponding one of the plurality of switching signals having respective frequencies different from each other.

In another embodiment, the switching signal may include a plurality of signals having respective signal magnitudes different from each other. Each of the plurality of polarized signals is provided with a corresponding one of the plurality of switching signals that have respective signal magnitudes different from each other. For example, the switching signal may be a pulse signal including a plurality of pulses having respective magnitudes different from each other.

In an embodiment, a supply bias may be added to the generated switching signal such that a positive pulse drives the switching and a negative pulse resets the switch sequence, or vice versa.

The generated switching signal is then transmitted to switching circuit <NUM> of antenna assembly <NUM> through antenna cable <NUM>. The switching signal may be superimposed on the DC bias signal for transmission to antenna assembly <NUM>.

Receiver <NUM> includes a control engine <NUM> that determines a desired null direction (θ<NUM>, φ<NUM>). Control engine <NUM> may determine the desired null direction using a control loop that is operated to find a position or a direction of a source of interference by optimizing signal level and minimizing interference indicators in the receiver. For example, GNSS signal <NUM> by antenna <NUM> is a spread spectrum signal, and control engine <NUM> may determine a direction of a dominant multipath interference by operation of the control loop, and then determine the direction of the dominant multipath interference as the desired null direction. In addition to the desired null direction, control engine <NUM> may further determine a beam direction.

In an embodiment, based on the determination of the desired null direction, control engine <NUM> may further determine a desired amplitude and a desired phase for each of the plurality of polarized signals included in the time-division multiplexed signal. In an embodiment, control engine <NUM> may determine the desired amplitude and the desired phase for each of the plurality of polarized signals based on the desired null direction, a desired beam direction, a direction of a source of interference, or a direction of a dominant multipath interference, or any combination thereof. Control engine <NUM> may determine the desired amplitude and the desired phase for each of the plurality of polarized signals based on an optimization on-the-fly, if an antenna pattern (gain, phase, etc.) is known. Alternatively, control engine <NUM> may determine the desired amplitude and the desired phase for each of the plurality of polarized signals by using a model, for example, but not limited to, a low-order polynomial model.

In an embodiment, control engine <NUM> may be implemented as software and the operations of control engine <NUM> can be accomplished by a program stored in a computer-readable storage medium and executed by a processor. The processor may be implemented inside receiver <NUM>. In another embodiment, control engine <NUM> may be implemented as hardware that includes the program and a processor configured to execute the program to perform the functions of the control engine.

Receiver <NUM> includes a steering engine <NUM> that assigns a complex weight to each of the plurality of polarized signals included in the incoming TDM signal <NUM>. In an embodiment, the complex weight includes a weight of an amplitude (a<NUM>, a<NUM>, a<NUM>, etc.) and a weight of a phase (ψ<NUM>, ψ<NUM>, ψ<NUM>, etc.) of each of the plurality of polarized signals. For example, steering engine <NUM> may assign a complex weight (a<NUM>, ψ<NUM>) to first polarized signal <NUM>, a complex weight (a<NUM>, ψ<NUM>) to second polarized signal <NUM>, and a complex weight (a<NUM>, ψ<NUM>) to third polarized signal <NUM>.

In another embodiment, steering engine <NUM> may assign the complex weight to each of the plurality of polarized signals based on the desired null direction determined by control engine <NUM>. For example, for a known antenna pattern (gain and phase), steering engine <NUM> may run an optimization on-the-fly to assign the complex weight to each of the plurality of polarized signals. Alternatively, steering engine <NUM> may use a model such as, for example, a low-order polynomial model to map the desired null direction to the complex weight of each of the plurality of polarized signals. Alternatively, steering engine <NUM> may obtain the complex weight corresponding to the desired null direction from a look-up table included in receiver <NUM>. In this embodiment, determination of the desired amplitude and the desired phase for each of the plurality of polarized signals may not be performed by control engine <NUM>.

Steering engine <NUM> also generates a switching control signal for switching signal generator <NUM>. The generated switching control signal is then transmitted to switching signal generator <NUM> and controls signal generation at switching signal generator <NUM>. In an embodiment, under control of the switching control signal, switching signal generator <NUM> may generate a switching signal such that the complex weight assigned for each of first polarized signal <NUM>, second polarized signal <NUM>, and third polarized signal <NUM> is reflected by operation of switch <NUM>.

In an embodiment, steering engine <NUM> may be implemented as software and the operations of steering engine <NUM> can be accomplished by a program stored in a computer-readable storage medium and executed by a processor. The processor may be a processor implemented inside receiver <NUM>. In another embodiment, steering engine <NUM> may be hardware that includes the program and a processor configured to execute the program to perform the functions of the steering engine.

In an alternative embodiment, control engine <NUM> and steering engine <NUM> may be merged into one operation that optimizes receiver parameters, for example, a carrier-to-noise density (C/N0) or a signal-to-noise ratio (SNR) of receiver <NUM>.

Receiver <NUM> includes a correlator <NUM>. Correlator <NUM> includes a plurality of correlator channels. Each of the plurality of correlator channels receives the incoming TDM signal <NUM>. Each of the plurality of correlator channels includes a pseudo-random noise (PRN) code generator and a numerically controlled oscillator (NCO) coupled to a mixer. For example, correlator channel <NUM> includes a PRN code NCO <NUM> coupled to a mixer <NUM>. In each correlator channel, the PRN code generator generates a unique PRN code for the incoming TDM signal <NUM>.

In an embodiment, GNSS signal <NUM> received by antenna <NUM> is a signal transmitted from a single GNSS satellite, and correlator channel <NUM> (or any other correlator channel) is assigned to process the incoming TDM signal <NUM>. The PRN code generator of correlator channel <NUM> generates a PRN code corresponding to the PRN code of the GNSS signal <NUM> from the single GNSS satellite. In correlator channel <NUM>, the incoming TDM signal <NUM> is mixed by mixer <NUM> with a local oscillating signal generated by NCO <NUM> of correlator channel <NUM>. The complex weight assigned to each of first polarized signal <NUM>, second polarized signal <NUM>, and third polarized signal <NUM> is applied to each signal. A weight of a phase for each signal may be applied by shifting the phase of each signal in the NCO based on the weight of the phase in the complex weight. A weight of an amplitude for each signal may be applied by adjusting the amplitude of each signal based on the weight of the amplitude in the complex weight. For example, in the complex weight (a<NUM>, ψ<NUM>) that is assigned to first polarized signal <NUM>, a<NUM> may indicate an amount to be multiplied with a current amplitude of first polarization signal <NUM>, and ψ<NUM> may indicate a phase shift to be applied to a current phase of first polarized signal <NUM>. The current amplitude and the current phase of first polarization signal <NUM> is adjusted based on a<NUM> and ψ<NUM>. In this way, null-steering or beam steering can be accomplished by determining a desired null direction or desired beam direction, and assigning and applying complex weights to the plurality of polarized signals forming a time-division multiplexed signal during correlation.

The amplitude and/or phase adjusted polarized signals are correlated in the correlator channel <NUM> to form output signals for further processing. For example, correlated plurality of polarized signals may be recombined for tracking or positioning purpose.

In another embodiment, GNSS signal <NUM> received by antenna <NUM> includes a plurality of signals respectively transmitted from a plurality of different satellites. The plurality of different satellites may correspond to one or more satellite frequency bands. For example, the plurality of satellites may respectively correspond to a plurality of satellite frequency bands. In this embodiment, each of the plurality of correlator channels is assigned to a different one of the plurality of satellites. For example, receiver <NUM> may include a receiver manager (not shown) that assigns each of the plurality of correlator channels to a different one of the plurality of satellites based on a plurality of PRN codes respectively corresponding to the plurality of satellites. In an embodiment, the receiver manager may be implemented as software and the operations of assigning the plurality of satellite signals can be accomplished by a program stored in a computer-readable storage medium and executed by a processor. The processor may be a processor implemented inside the receiver. In this embodiment, control engine <NUM> may determine different desired null directions for the plurality of correlator channels, and steering engine <NUM> may assign a complex weight for each of a plurality of polarized signals in each correlator channel based on a desired null direction determined for each correlator channel. Each of the plurality of correlator channels may independently perform signal processing on the signal received from the corresponding one of the plurality of satellites. In this way, null steering can be performed on a local scale, for example, null steering can be applied to an individual satellite, rather than to a plurality of satellites, leading to an enhanced mitigation of multipath interference, spoofing, and jamming.

In an embodiment, the signal received by antenna <NUM> includes a first signal corresponding to a first frequency band and a second signal corresponding to a second frequency band. In this embodiment, the receiver manager assigns a first correlator channel of correlator <NUM> to the first frequency band signal based on a PRN code of the first frequency band signal and a second correlator channel of correlator <NUM> to the second frequency band signal based on a PRN code of the second frequency band signal.

Receiver <NUM> may include other components, such as an analog-to-digital converter (ADC). For brevity, descriptions of these components are omitted here.

By using single antenna <NUM> having a plurality of feed points that support different polarizations, time-division multiplexing the plurality of polarized signals using a switch, and then processing the time-division multiplexed signal in the digital domain at the receiver, there is no need to use an antenna array. As a result, size and cost associated with the antenna is reduced. The assignment of a complex weight including a weight of an amplitude and a weight of a phase to each of the plurality of polarized signals enables null steering for a satellite signal during correlation using the single antenna. By using the plurality of correlator channels of correlator <NUM> for the plurality of satellite signals, null steering is performed individually for each of the satellite signals, enabling enhanced accuracy of mitigation of multipath interference, jamming, and spoofing. In addition, superimposing multiple signals (e.g., the switching signal and the DC bias signal) carried by antenna cable <NUM> obviates the need for multiple antenna cables, which leads to reduced cost and size.

<FIG> is a flow chart illustrating an exemplary method <NUM> for processing a signal, consistent with some embodiments of the present disclosure. The method may be performed by an apparatus, such as apparatus <NUM> of <FIG>. Referring to <FIG>, method <NUM> includes a step S210 of generating a switching signal. For example, the switching signal may be generated by a receiver, such as receiver <NUM> of <FIG>. The switching signal may be synchronized by mixing with a local oscillating signal provided by a local oscillator. The generated switching signal may be transmitted to an antenna assembly, such as antenna assembly <NUM>, via antenna cable <NUM>.

Method <NUM> includes a step S220 of controlling a switch in the antenna assembly based on the switching signal. For example, the switching signal transmitted to antenna assembly <NUM> is used to control switch <NUM> of switching circuit <NUM> of antenna assembly <NUM>.

Method <NUM> includes a step S230 of time-division multiplexing the plurality of polarized signals using the switch. For example, under the control of the switching signal, switch <NUM> of switching circuit <NUM> of antenna assembly <NUM> periodically switches between the plurality of feed points of antenna <NUM> and selects a signal at a point in time, thereby time-division multiplexing the plurality of polarized signals. The time-division multiplexed signal is then transmitted to receiver <NUM> for processing in the digital domain, for example, by a software-based signal processing at the receiver, for example, by control engine <NUM> and steering engine <NUM>. In an embodiment, the time-division multiplexed signal may be amplified and filtered at antenna assembly <NUM> before transmitting to the receiver <NUM>.

Method <NUM> includes a step S240 of determining a desired amplitude and a desired phase for each of the plurality of polarized signals in the time-division multiplexed signal. For example, the desired amplitude and the desired phase for each of the plurality of polarized signals in the time-division multiplexed signal may be determined by a control engine, such as control engine <NUM> of receiver <NUM>, or by a steering engine, such as steering engine <NUM> of receiver <NUM>. The desired amplitude and the desired phase for each of the plurality of polarized signals may be determined based on at least one of: a desired null direction, a desired beam direction, a direction of a source of interference, or a direction of a dominant multipath interference. The desired amplitude and the desired phase for each of the plurality of polarized signals may be determined by using an optimization on the fly or a model.

Method <NUM> includes a step S250 of assigning a complex weight to each of the plurality of polarized signals in the time-division multiplexed signal. The complex weight may include a weight of an amplitude and a weight of a phase of each of the plurality of polarized signals. In an embodiment, the complex weight for each of the plurality of polarized signals may be assigned by a steering engine, such as steering engine <NUM> of receiver <NUM> of <FIG>. For example, the steering engine may obtain the complex weight corresponding to the desired null direction from a look-up table included in receiver <NUM>. In another embodiment, the complex weight of each of the plurality of polarized signals may be assigned by the control engine. For example, the control engine may perform a sequential optimization procedure to determine on-the-fly a complex weight to be used for a given correlator channel.

Method <NUM> includes a step S260 of correlating the plurality of time-division multiplexed polarized signals. The correlating may be performed by a correlator, such as correlator <NUM> of receiver <NUM>, that includes a plurality of correlator channels. In each correlator channel, an incoming time-division multiplexed signal is mixed by a mixer with a local oscillating signal generated by an NCO of the correlator channel. In each correlator channel, a unique PRN code corresponding to a signal transmitted from a satellite may be generated and the complex weight may be applied to each of the plurality of polarized signals.

<FIG> is a block diagram of an exemplary device <NUM>, consistent with some embodiments of the present disclosure. Referring to <FIG>, device <NUM> may take any form, including but not limited to, a laptop computer, a Global Positioning System (GPS), a wireless terminal including a mobile phone, a wireless handheld device, or wireless personal device, or any other forms. Device <NUM> includes a receiver <NUM>, an antenna <NUM> coupled to receiver <NUM>, a processor <NUM>, a memory <NUM>, a local clock <NUM>, and an Input/Output device <NUM>.

Receiver <NUM>, coupled to antenna <NUM>, is configured to receive a signal from one or more signal sources. In some embodiments, receiver <NUM> may be part of a transceiver modem which includes a transmitter configured to transmit data to an external device. Local clock <NUM> provides a time of a local place at which device <NUM> is disposed.

In an embodiment, similar to receiver <NUM> of <FIG>, receiver <NUM> may implement a correlator including a plurality of correlator channels, such as correlator <NUM> of <FIG>. Each of the plurality of correlator channels may be assigned to a different one of a plurality of signals transmitted from a corresponding one of a plurality of satellites. In each correlator channel, an incoming time-division multiplexed signal may be mixed by a mixer with a local oscillating signal generated by an NCO of the correlator channel.

In an embodiment, similar to receiver <NUM> of <FIG>, receiver <NUM> may include a control engine, such as control engine <NUM> of <FIG>, that determines a desired phase and a desired amplitude for each of the plurality polarized signal. Receiver <NUM> may also include a steering engine, such as steering engine <NUM>, that assigns a complex weight for each of the plurality of polarized signals. The PRN code may be generated by a PRN code generator in each of the correlator channels. The control engine and/or the steering engine may be implemented as a program stored in a computer-readable storage of the receiver. Receiver <NUM> may include a built-in processor (not shown) configured to execute the program and performs the functions of the control engine and steering engine.

Receiver <NUM> may include a switching signal generator that generates a switching signal, such as switching signal generator <NUM> of <FIG>. The generation of the switching signal may be controlled by the steering engine. Receiver <NUM> may include other components, such as a bias signal generator. For brevity, descriptions of these components are omitted here.

Processor <NUM> may include one or more dedicated processing units, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or various other types of processors or processing units. In an embodiment, the processor that is disposed inside receiver <NUM> may be a front-end processor that performs signal processing in receiver <NUM>, and processor <NUM> may be a back-end processor that receives the signal processing results from receiver <NUM> and provides feedback to receiver <NUM>. In this embodiment, processor <NUM> may also perform a portion of the digital domain signal processing of receiver <NUM>. Processor <NUM> may perform additional computation, for example, for determining position of the receiver. Processor <NUM> may be further configured to control the performance of Input/Output device <NUM>, clock <NUM>, and memory <NUM>. In another embodiment, receiver <NUM> does not have the built-in processor, and processor <NUM> performs all the functions of the built-in processor. In another embodiment, device <NUM> does not have processor <NUM>, and the built-in processor of receiver <NUM> performs all the functions of processor <NUM>.

Memory <NUM> may be any type of computer-readable storage medium including volatile or non-volatile memory devices, or a combination thereof. Memory <NUM> may store information related to identities of device <NUM> and the GNSS signals received by receiver <NUM>. Memory <NUM> may also store post processing signals, for example, the correlated signals. Memory <NUM> may also store computer-readable program instructions and mathematical models that are used in signal processing in receiver <NUM> and computations performed in processor <NUM>. Memory <NUM> may further store computer-readable program instructions for execution by processor <NUM> to operate device <NUM>.

Input/Output device <NUM> may be used to communicate a result of signal processing to a user or another device. Input/Output device <NUM> may include a user interface including a display and an input device to transmit a user command to processor <NUM>. The display may be configured to display a status of signal reception at device <NUM>, the data stored at memory <NUM>, a status of signal processing, and a result of the signal processing, etc. For example, the display may display results of null steering, beam steering, tracking, and positioning. The display may include, but is not limited to, a cathode ray tube (CRT), a liquid crystal display (LCD), a light-emitting diode (LED), a gas plasma display, a touch screen, or other image projection devices for displaying information to a user. The input device may be any type of computer hardware equipment used to receive data and control signals from a user. The input device may include, but is not limited to, a keyboard, a mouse, a scanner, a digital camera, a joystick, a trackball, cursor direction keys, a touchscreen monitor, or audio/video commanders, etc. Input/Output device <NUM> may further include a machine interface, such as an electrical bus connection or a wireless communications link.

The computer-readable storage medium of the present disclosure may be a tangible device that can store instructions for use by an instruction execution device. The computer-readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer-readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing.

The computer-readable program instructions of the present disclosure may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state-setting data, or source code or object code written in any combination of one or more programming languages, including an object-oriented programming language, and conventional procedural programming languages. The computer-readable program instructions may execute entirely on a computing device as a stand-alone software package, or partly on a first computing device and partly on a second computing device remote from the first computing device. In the latter scenario, the second, remote computing device may be connected to the first computing device through any type of network, including a local area network (LAN) or a wide area network (WAN).

The flowcharts and block diagrams in the figures illustrate examples of the architecture, functionality, and operation of possible implementations of systems, methods, and devices according to various embodiments. It should be noted that, in some alternative implementations, the functions noted in blocks may occur out of the order noted in the figures.

It is understood that the described embodiments are not mutually exclusive, and elements, components, materials, or steps described in connection with one example embodiment may be combined with, or eliminated from, other embodiments in suitable ways to accomplish desired design objectives.

Reference herein to "some embodiments" or "some exemplary embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment. The appearance of the phrases "one embodiment" "some embodiments" or "another embodiment" in various places in the present disclosure do not all necessarily refer to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments.

It should be understood that the steps of the example methods set forth herein are not necessarily required to be performed in the order described, and the order of the steps of such methods should be understood to be merely example. Likewise, additional steps may be included in such methods, and certain steps may be omitted or combined, in methods consistent with various embodiments.

As used in the present disclosure, the word "exemplary" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word is intended to present concepts in a concrete fashion.

As used in the present disclosure, unless specifically stated otherwise, the term "or" encompasses all possible combinations, except where infeasible. For example, if it is stated that a database may include A or B, then, unless specifically stated otherwise or infeasible, the database may include A, or B, or A and B. As a second example, if it is stated that a database may include A, B, or C, then, unless specifically stated otherwise or infeasible, the database may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

Additionally, the articles "a" and "an" as used in the present disclosure and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from context to be directed to a singular form.

Unless explicitly stated otherwise, each numerical value and range should be interpreted as being approximate as if the word "about" or "approximately" preceded the value of the value or range.

Although the elements in the following method claims, if any, are recited in a particular sequence, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

It is appreciated that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the specification, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the specification. Certain features described in the context of various embodiments are not essential features of those embodiments, unless noted as such.

Claim 1:
An apparatus (<NUM>), comprising:
an antenna assembly (<NUM>), comprising:
an antenna (<NUM>) configured to receive a signal (<NUM>) and generate, at a plurality of feed points of the antenna, a plurality of corresponding polarized signals (<NUM>, <NUM>, <NUM>) having respective polarization directions different from each other, using the received signal; and
a switching circuit (<NUM>) configured to periodically switch between the plurality of feed points to select a corresponding one of the polarized signals among the plurality of polarized signals at a point of time based on a switching signal,
wherein the switching signal controls a switch (<NUM>) in the switching circuit to switch between the plurality of feed points; and
wherein the switching circuit is configured to time-division multiplex the plurality of polarized signals based on the switching signal and generate a time-division multiplexed signal.