AoD Direction Finding Transmitter Antenna Soft Switching Solution

Abstract

This invention relates to an antenna soft-switching system (310, 1000, 1200) for a launch angle (AoD) direction-finding transmitter unit (300). The soft-switching system (310, 1000, 1200) includes: a timing unit (301) for at least obtaining the start time of a switching event; a switching network (303) disposed on a radio frequency (RF) signal path between an RF port (304) and a first antenna port (306a) and a second antenna port (306b); and a generator unit (302) for generating at least one waveform for controlling the switching network (303). The generator unit (302) is configured to control the switching network (303) such that the amplitude of the RF signal switches substantially smoothly from the first antenna port (306a) to the second antenna port (306b), thereby reducing undesirable transmission levels of the transmitted RF spectrum of the AoD direction-finding transmitter unit (300). The present invention also relates to an AoD direction finding transmitter unit (300) including an antenna soft switching system (310, 1000, 1200) and an antenna soft switching method for the AoD direction finding transmitter unit (300).

Description

Technical Field

[0001] This invention generally relates to the field of direction-finding system technology. In particular, this invention relates to soft switching of direction-finding transmitters. Background Technology

[0002] Indoor positioning and navigation technologies have received widespread attention in recent years. While outdoor navigation is largely based on Global Navigation Satellite System (GNSS) satellite services, there is currently no universally applicable technology or service to facilitate indoor navigation. Existing indoor navigation solutions are mainly based on wireless LAN, Bluetooth Low Energy (BLE), visible light, or infrared light. The coverage and positioning accuracy of these solutions are limited to varying degrees.

[0003] An emerging indoor positioning technology solution is based on radio direction finding systems. For this purpose, radio direction finding systems can be divided into systems using the angle of arrival (AoA) method and the angle of departure (AoD) method. Both methods utilize antenna arrays consisting of several different antenna elements (physically separated from each other). Having more antennas in the antenna array generally improves positioning accuracy and the positioning system's tolerance to impairments caused by the radio signal propagation environment. In a simple direction finding solution, one of the antenna elements in the antenna array is active for a given time, and the active antenna changes over time.

[0004] In the AoA method, an antenna array is used for reception. The receiver antenna elements are varied to find the direction of the incoming radio wave array from the transmitter, and the position is defined based on the observed phase difference collected from the receiver antenna elements. Figure 1 A simplified example illustrating the principle of an AoA direction finding system 100 is shown schematically. The AoA radio direction finding system 100 includes a transmitter unit 102 and a receiver unit 104. The transmitter unit 102 includes a transmitting antenna 106 and an RF transmitter 108, such as a BLE transmitter. The receiver unit 104 includes a receiving antenna array, which in this simplified example includes four antenna elements 110a-110d. Furthermore, the receiver unit 104 includes an antenna switching unit 112 for switching between antenna elements 110a-110d, an RF receiver 114 (e.g., a BLE receiver), and an AoA estimation unit 116. The AoA estimation unit 116 of the receiver unit 104 estimates the angle of arrival of a signal using sampled receiver signals.

[0005] In the AoD method, an antenna array is used for transmission. The transmitter signal is continuously fed to each antenna element of the antenna array for a short period to generate a signal at the receiver. The transmitted signal is switched between antenna elements according to a predetermined antenna switching mode. The antenna switching mode defines the order in which the antennas in the antenna array are activated. This switching produces a directional, phase-modulated radiated signal that can be used to define the estimated relative direction between the transmitter and receiver at a distance. The estimation is based on the received signal, and the receiver does not need to have a directional antenna. Figure 2 A simplified example illustrating the principle of an AoD direction finding system 200 is provided. The AoD radio direction finding system 200 includes a transmitter unit 202 and a receiver unit 204. The transmitter unit 202 includes a transmitting antenna array, which in this simplified example includes four antenna elements 206a-206d. Furthermore, the transmitter unit 202 includes an antenna switching unit 212 for switching the transmitted signal between the antenna elements 206a-206d and an RF transmitter 208 (e.g., a BLE transmitter). The receiver unit 204 includes a receiving antenna 210, an RF receiver 214 (e.g., a BLE receiver), and an AoD estimation unit 216. The AoD estimation unit 216 of the receiver unit 204 estimates the angle of arrival of a signal using sampled receiver signals.

[0006] In the AoD (Aspect-of-Device) approach, if the switching occurs too quickly, the transmission signal may unnecessarily spread across the radiated RF spectrum as it transitions from one antenna element to another. This spread can interfere with other radio receivers near the AoD transmitter and may violate spectrum emission regulations or result in non-compliance with relevant standards (such as Bluetooth).

[0007] In the AoA method, rapid switching from one antenna element to another can lead to unwanted false responses from nearby radio transmitters.

[0008] Typically, soft handover has been used in commercial direction-finding receivers, such as AoA receivers.

[0009] However, further solutions are needed to reduce the radiated spectrum emissions of the AoD transmitter. Summary of the Invention

[0010] To provide a basic understanding of some aspects of various embodiments of the invention, a simplified summary is presented below. This summary is not a broad overview of the invention. It is neither intended to identify key or critical elements of the invention nor to depict its scope. The following summary presents only some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplary embodiments of the invention.

[0011] The purpose of this invention is to provide an antenna soft-switching system, an AoD direction-finding transmitter unit, and an antenna soft-switching method for the AoD direction-finding transmitter unit. Another purpose of this invention is to reduce interference to radio receivers in nearby systems caused by the antenna soft-switching system, the AoD direction-finding transmitter unit, and the antenna soft-switching method for the AoD direction-finding transmitter unit.

[0012] The objective of this invention is achieved through the antenna soft-switching system, AoD direction-finding transmitter unit, and antenna soft-switching method as defined in their respective independent claims.

[0013] According to the first aspect, an antenna soft-switching system for a departure angle (AoD) direction-finding transmitter unit is provided, wherein the soft-switching system includes: a timing unit for obtaining at least the start time of a switching event; a switching network disposed on a radio frequency (RF) signal path between an RF port and a first antenna port and a second antenna port; and a generator unit for generating at least one waveform for controlling the switching network, wherein the generator unit is configured to control the switching network such that the amplitude of the RF signal switches substantially smoothly from the first antenna port to the second antenna port, thereby reducing undesirable transmission levels of the transmitted RF spectrum of the AoD direction-finding transmitter unit.

[0014] The switching network may include at least two switching elements, wherein the at least two switching elements are resistive switching devices, fully reactive switching devices, partially reactive switching devices, or active switching devices.

[0015] At least two switching devices may utilize a junction-gate field-effect transistor (JFET); a metal-oxide-semiconductor field-effect transistor (MOSFET); a metal-semiconductor field-effect transistor (MESFET); a pseudomorphic high electron mobility transistor (PHEMT); a PIN diode; or any other suitable RF switching device.

[0016] The generator unit may include a simulated ramp generator.

[0017] Alternatively, the generator unit may include a digital waveform generator, a digital-to-analog converter, and a reconstruction filter.

[0018] At least two switching devices can be digitally controlled attenuators.

[0019] The generator unit may include a digital waveform generator and a waveform encoder, which are configured to convert the waveform generated by the digital waveform generator into a control signal for a digitally controlled attenuator.

[0020] Alternatively, the generator unit may include a counter, and the waveform may be encoded into at least two switching devices.

[0021] The switching network can be implemented as part of an antenna switch, configured to change the active antenna port from a first antenna port to a second antenna port during a switching event, wherein the generator unit can be configured to control the switching network such that the amplitude of the RF signal at the first antenna port decreases substantially smoothly, and simultaneously, the amplitude of the RF signal at the second antenna port increases substantially smoothly.

[0022] Alternatively, the switching network can be a separate switching network providing a centralized soft switching system, wherein the generator unit can be configured to control the switching network so that: the amplitude of the RF signal at the first antenna port decreases substantially smoothly; and simultaneously, the amplitude of the RF signal at the reference port increases substantially smoothly, wherein the antenna switch can be configured to change the active antenna port while the RF signal is directed to the reference port; and wherein the generator unit can also be configured to control the switching network such that the amplitude of the RF signal at the reference port decreases substantially smoothly while the amplitude of the RF signal at the second antenna port increases substantially smoothly.

[0023] Alternatively, the switching network can be an independent switching network that provides a centralized soft switching system, and the first antenna port can belong to the first antenna group, and the second antenna port can belong to the second antenna group, wherein the generator unit can be configured to control the switching network such that: the amplitude of the RF signal in the first antenna group decreases substantially smoothly, while the amplitude of the RF signal in the second antenna group increases substantially smoothly, wherein the second antenna port is pre-selected as an active antenna of the second antenna group.

[0024] According to the second aspect, a departure angle (AoD) direction finding transmitter unit is provided, wherein the AoD direction finding transmitter unit includes the aforementioned antenna soft switching system.

[0025] According to a third aspect, an antenna soft-switching method for an AoD direction-finding transmitter unit is provided, wherein the method includes controlling a switching network by a waveform generated by a generator unit, such that the amplitude of the radio frequency (RF) signal is switched substantially smoothly from a first antenna port to a second antenna port, thereby reducing undesirable transmission levels of the transmitted RF spectrum of the AoD direction-finding transmitter unit.

[0026] The switching network can be implemented as part of an antenna switch that changes the active antenna port from a first antenna port to a second antenna port during a switching event, wherein the control of the switching network may include: substantially smoothly reducing the amplitude of the RF signal at the first antenna port and simultaneously substantially smoothly increasing the amplitude of the RF signal at the second antenna port.

[0027] Alternatively, the switching network may be a separate switching network providing a centralized soft handover system, wherein control of the switching network may include: substantially smoothly reducing the amplitude of the RF signal at the first antenna port; simultaneously substantially smoothly increasing the amplitude of the RF signal at the reference port; switching the active antenna port from the first antenna port to the second antenna port via the switching network of the antenna switch, while directing the RF signal to the reference port; substantially smoothly reducing the amplitude of the RF signal at the reference port; and simultaneously substantially smoothly increasing the amplitude of the RF signal at the second antenna port.

[0028] Alternatively, the switching network may be an independent switching network providing a centralized soft handover system, and the first antenna port may belong to a first antenna group, and the second antenna port may belong to a second antenna group. The method may include: substantially smoothly reducing the amplitude of the RF signal in the first antenna group while substantially smoothly increasing the amplitude of the RF signal in the second antenna group, wherein the second antenna port is preselected as an active antenna of the second antenna group.

[0029] Various exemplary and non-limiting embodiments of the invention, including structures and methods of operation, as well as additional objects and advantages of the invention, will be best understood from the following description of specific exemplary and non-limiting embodiments when read in conjunction with the accompanying drawings.

[0030] The verbs “comprising” and “including” are used in this document as disclosure restrictions, neither excluding nor requiring the presence of features not listed. Unless otherwise expressly stated, the features recited in the dependent claims may be freely combined with each other. Furthermore, it should be understood that the use of “a” or “an” in this document, i.e., the singular form, does not exclude the plural form. Attached Figure Description

[0031] Embodiments of the present invention are shown in the accompanying drawings by way of example rather than by way of limitation.

[0032] Figure 1 This illustrates a simple example of the principle of an angle of arrival (AoA) direction finding system.

[0033] Figure 2 This illustrates a simple example of the principle of an angle of departure (AoD) direction finding system.

[0034] Figure 3 An example of a direction-finding transmitter unit with an angle of departure (AoD) according to the present invention is shown schematically.

[0035] Figure 4 An example structure of the CTE framework is illustrated schematically.

[0036] Figure 5 An example of a transmitted RF spectrum with instantaneous switching is illustrated.

[0037] Figures 6A to 6D An example of an antenna soft-switching system according to the present invention is illustrated schematically.

[0038] Figure 7A An example of the time-domain amplitude of the RF waveform of a switching device with a linear ramp waveform is schematically shown.

[0039] Figure 7B An example of the time-domain amplitude of an RF waveform with a quantized linear ramp waveform switching is shown schematically.

[0040] Figure 8A An example of the transmitted RF spectrum obtained with an analog soft-switching system according to the present invention is shown.

[0041] Figure 8B An example of the transmitted RF spectrum obtained by a digital soft-switching system according to the present invention is shown.

[0042] Figure 8C An example of adjacent channel leakage ratio (ACLR) with instantaneous handover and digital soft handover according to the present invention is shown.

[0043] Figure 9 An example of a switching device implemented as a digitally controlled attenuator is illustrated.

[0044] Figure 10 Another example of an antenna soft-switching system according to the present invention is shown.

[0045] Figure 11 The diagram schematically illustrates the RF waveform of a switching device and an example of a virtual load with a quantized linear ramp waveform.

[0046] Figure 12 Another example of an antenna soft-switching system according to the present invention is shown.

[0047] Figures 13 to 16 An example of the method according to the present invention is shown. Detailed Implementation

[0048] Figure 3An example of an AoD (Aspect-of-Depth) direction-finding transmitter unit 300 according to the present invention is illustrated schematically. As will be described in this application, the AoD direction-finding transmitter unit 300 may include an antenna soft-switching system 310, 1000, 1200 according to any embodiment of the present invention. The AoD transmitter unit 300 also includes at least one radio frequency (RF) transmitter module 320 for generating at least one RF signal to be transmitted; and at least one antenna array 330 including at least two antenna elements 332a-332n, through which at least one RF signal 305 is transmitted by continuously feeding at least one RF signal 305 to each antenna element 332a-332n of the at least one antenna array 330. The antenna soft-switching system 310 may be implemented as part of an antenna switch configured to perform switching between antenna elements 332a-332n, i.e., the antenna switch includes a switching network formed by a plurality of switching devices configured to continuously select antenna elements 332a-332n in the at least one antenna array 330 for transmitting RF signals. In other words, the antenna switch is configured to activate each antenna element 332a-332n of at least one antenna array 330 sequentially. The AoD transmitter unit 300 can transmit RF signals via the active antenna elements, causing each antenna element to be continuously changed (i.e. switched) to be an active antenna element. Each antenna element 332a-332n can be connected to a corresponding antenna port 306a-306n to connect the antenna array 330 to the antenna soft-switching system 310 and the antenna switch. This means that the number of antenna elements 332a-332n of at least one antenna array 330 determines the number of antenna ports 306a-306n. For example, if at least one antenna array 330 includes 10 single-ended antenna elements, the number of antenna ports 306a-306n is 10. According to another example, if at least one antenna array 300 includes 10 differentially fed balanced antenna elements 332a-332n, the number of antenna ports 306a-306n is 20. According to another example, if at least one antenna array 330 includes 10 differentially fed balanced antenna elements 332a-332n and 10 single-ended antenna elements 332a-332n, then the number of antenna ports 306a-306n is 30. The antenna switch may include a conversion unit configured to provide a single-ended to differential conversion of at least one RF signal for providing at least one positive-phase RF signal RF+ and at least one negative-phase RF signal RF- for each differentially fed balanced antenna element 332a-332n of the at least one antenna array 330.

[0049] In the AoD transmitter unit 300, if the switching is instantaneous, switching from an RF signal transmitted by one antenna element, i.e., the first antenna element 332a, to another antenna element, i.e., the second antenna element 332b, may result in an unwanted spread of the transmitted RF spectrum, i.e., unwanted transmission. Undesirable transmission of the transmitted RF spectrum can be out-of-channel spectrum transmission, i.e., transmission at frequencies deviating from the transmission frequency. This spread may cause interference to radio receivers of other systems near the AoD transmitter unit 300, may potentially violate regulatory requirements for spectrum transmission, and / or may lead to non-compliance with relevant standards, such as Bluetooth. The AoD function in direction finding is already included in Bluetooth SIG standard version 5.1. The AoD function of the direction finding system is implemented by adding a so-called Constant Tone Spread (CTE) period, i.e., CTE frame 400, to the end of the transmitted Bluetooth Low Energy (BLE) advertising packet frame. Figure 4 The example structure of a CTE frame 400 as defined in BLE 5.1 ​​is shown. A CTE frame may include the following structure: a guard period 410, a reference period 420, and multiple alternating switching slots 430a-430n and sampling slots 440a-440b. The guard period 410 is the first part of the CTE, and no useful information is transmitted during the guard period. The duration of the guard period 410 is 4 microseconds. The reference period 420 is a phase reference used for subsequent measurements. The duration of the reference period 420 is 8 microseconds. Each sampling slot 440a-440n is the time reserved from the active antenna element for phase measurement (i.e., the actual measurement). The duration of each sampling slot 440a-440n is 1 microsecond or 2 microseconds. Each switching slot 430a-430n is the time reserved for changing (i.e., switching) the active antenna port. The duration of each switching slot 430a-430n is 1 microsecond or 2 microseconds. This means that the switching of the transmitted RF signal from the first antenna element 332a to the second antenna element 332b needs to be performed within 1 microsecond or 2 microseconds, which can be considered as an instantaneous switch and results in a broadband spread of the transmitted RF spectrum. Figure 5 An example of transmitted RF spectrum is shown, where a momentary switching causes an expansion of the transmitted RF spectrum, which can be considered as high out-of-channel emission of the RF spectrum. In this example, for a small offset frequency (less than ±2.5 MHz from the transmit frequency), the out-of-channel emission level is likely to be between -30 dB and -15 dB; for a larger offset frequency (between ±2.5 MHz and ±10 MHz), the out-of-channel emission level is likely to be between -45 dB and -30 dB.

[0050] The soft handover system 310 includes a timing unit 301, a generator unit 302, and a switching network 303. The switching network 303 is arranged on an RF signal path 305 between at least one RF port 304 and antenna ports 306a-306n. The antenna soft handover system 310 can be connected to an RF transmitter module 320 via at least one RF port 304 to provide at least one RF signal 305 from the RF transmitter module 320 to each antenna element connected to the corresponding antenna port via antenna ports 306a-306n each time. The timing unit 301 is configured to at least obtain the start time of the handover event and optionally also obtain the end time of the handover event. The timing unit 301 can be configured to at least define the start time of the handover event and optionally also define the end time of the handover event. Optionally or additionally, the timing unit 301 can receive, for example, the start time and / or the end time of the handover event as control signals from an external control unit (e.g., a switch control unit for an antenna switch). Optionally or additionally, the end time of the handover event can be defined by a waveform generated by the generator unit 302. Generator unit 302 is configured to generate at least one waveform for controlling switching network 303. Generator unit 302 is configured to control switching network 303 such that the amplitude of RF signal 305 switches substantially smoothly (i.e., gradually) from first antenna port 306a to second antenna port 306b, thereby reducing undesirable transmission levels in the transmitted RF spectrum of AoD transmitter unit 300 caused by the switching event. During the switching event, the impedance seen by at least one RF port 304 can remain constant. The term "switching event" throughout this application means switching RF signal 305 from one antenna port to another. A sequence of switching events, i.e., a switching sequence, comprises multiple switching events. The invention is defined above such that a switch from first antenna port 306a to second antenna port 306b occurs; however, the spirit of the invention is directly applicable to switching between any two antenna ports 306a-306n. Furthermore, since each antenna element 332a-332n of at least one antenna array 330 is connected to at least one antenna port 306a-306n, switching from one antenna port to another also results in switching from one antenna element to another, i.e., switching from the first antenna element 332a connected to the first antenna port 306a to the second antenna element 332b connected to the second antenna port 306b. The first antenna port 306a and the second antenna port 306b can be any two antenna ports 306a-306b. Specifically, the first antenna element 332a connected to the corresponding first antenna port 306a and the second antenna element 332b connected to the corresponding second antenna port 306b can be any two antenna elements 332a-332n of at least one antenna array 330.

[0051] Figure 6A An example embodiment of the antenna soft-switching system 310 according to the present invention is shown, wherein the switching network 303 is implemented as part of an antenna switch configured to perform switching of RF signals from a first antenna port 306a to a second antenna port 306b. That is, the switching network 303 is a switching network configured to change the active antenna port from the first antenna port 306a to the second antenna port 306b, and correspondingly change the active antenna element from the first antenna element 332a to the second antenna element 332b. In other words, the switching network 303 can be configured to activate the second antenna port 306b and the antenna element 332b connected to the second antenna port 306b, and deactivate (i.e., disconnect) the first antenna port 306a and the antenna element 332a connected to the first antenna port 306a. Generator unit 302 is configured to control switching network 303 during a switching event, such that the amplitude of the RF signal 305 at the first antenna port 306a decreases substantially smoothly (i.e., reduces), while the amplitude of the RF signal 305 at the second antenna port 306b increases substantially smoothly (i.e., increases). Switching network 303 may include at least two switching devices 602a, 602b. The at least two switching devices 602a, 602b may be resistive switching devices, fully reactive switching devices, partially reactive switching devices, or active switching devices. The at least two switching devices 602a, 602b may utilize junction-gate field-effect transistors (JFETs); metal-oxide-semiconductor field-effect transistors (MOSFETs); metal-semiconductor field-effect transistors (MESFETs); pseudocrystalline high electron mobility transistors (PHEMTs); PIN diodes; or any other suitable RF switch.

[0052] exist Figure 6AIn the example antenna soft-switching system 310, generator unit 302 includes an analog ramp generator, and the two switching devices 602a and 602b are JFET, MOSFET, MESFET, or PHEMT transistors. When used as switching devices 602a and 602b, the transistors can operate in a linear “transistor” region. In this region, the channels of switching devices 602a and 602b act as variable resistors, the value of which depends on the gate voltage (Vgs) of switching devices 602a and 602b. By slowly raising / lowering (i.e., increasing / decreasing) the gate voltage during switching events (i.e., during the switching slots 430a-430n), the RF attenuation of switching devices 602a and 602b also changes smoothly in proportion to the Rds / VGS transfer function of switching devices 602a and 602b, where Rds is the resistance of the transistor. Then, compared to the instantaneous on / off switching between the first antenna port 306a and the second antenna port 306b, this smooth switching reduces out-of-channel RF spectrum transmission. In this example antenna soft-switching system 310, when the gate voltage of switching device 602b rises, the gate voltage of switching device 602a falls, and vice versa. The waveforms of the gate voltages of switching devices 602a and 602b are used as control signals for switching devices 602a and 602b. Figure 7A An example of the time-domain amplitude of the RF waveform of the second switching device 602b during a switching event is schematically shown, wherein the control signal for the second switching device 602b is a linear ramp waveform generated by an analog ramp generator to smoothly boost the amplitude of the RF signal 305 at the second antenna port 306b. By placing an inverting component 604, such as an inverting amplifier arrangement with a voltage gain set to 1, between the generator unit 302 and the second switching device 602b, the same linear ramp waveform can be used to control the first switching device 602a and the second switching device 602b to invert the linear ramp waveform generated by the analog generator unit 302. As a result of the inversion, the waveform of the second switching device 602b is opposite to that of the first switching device 602a, so that the gate voltage of the switching device 602b decreases substantially smoothly as the gate voltage of the switching device 602b rises substantially smoothly. Figure 8A Demonstrates the use of Figure 6A The image shows an example of the transmitted RF spectrum obtained by the simulated soft-switching system 310. From... Figure 8A It can be seen that, with Figure 5 Compared to the instantaneous switching shown, the unwanted transmission level of the transmitted RF spectrum is reduced. Figure 8AIn the example, for smaller offset frequencies (less than ±2.5 MHz from the transmit frequency), the level of out-of-channel spectral emission may be between -40 dB and -8 dB; for larger offset frequencies (between ±2.5 MHz and ±10 MHz), the level of out-of-channel spectral emission may be between -60 dB and -40 dB.

[0053] Different switching devices 602a and 602b require different control signals depending on their specific characteristics. For example, if switching devices 602a and 602b are PIN diodes, the switching resistance can be controlled by a DC or low-frequency current passing through the PIN diode. Similarly, if the waveform is generated by generator unit 302, the shape of the waveform can be limited to simple waveforms, such as linear ramp waveforms. Furthermore, the Rds / Vgs characteristics of switching devices 602a and 602b can affect the resulting RF waveform.

[0054] More complex waveforms can be generated digitally, and digital waveforms can be converted into analog waveforms using a digital-to-analog (D / A) converter. Figure 6B Another exemplary embodiment of the antenna soft-switching system 310 according to the present invention is shown, wherein the generator unit 302 includes a digital waveform generator 606, a D / A converter 608, and a reconstruction filter 610. The output of the D / A converter needs to be filtered to remove aliasing and fed to the switching devices 602a, 602b, such as the gates of transistor switching devices. Digitally generating waveforms requires some additional hardware, such as memory, for example, the memory of the generator unit 302 or the waveform generation function, the D / A converter 608, and the reconstruction filter 610, and the timing unit 301 needs to operate at a clock rate higher than the actual switching frequency. Furthermore, in digital soft-switching, the timing unit 301 can also be configured to time events of the entire switching event sequence, including timing for reading waveform samples from the memory of the generator unit 302, timing for updating control signals of the switching devices 602a, 602b, etc. Otherwise, Figure 6B Operation of the soft handover system 310 Figure 6A The soft switching system is similar to the 600.

[0055] Alternatively, instead of using resistive switching devices, at least two switching devices 602a and 602b can be digitally controlled attenuators. Figure 6CAnother exemplary embodiment of the antenna soft-switching system 310 according to the present invention is shown, wherein the switching network 303 includes at least two resistive switching devices 602a, 602b implemented as digitally controlled attenuators, and the generator unit 302 includes a digital waveform generator 606. The switching devices 602a, 602b implemented as digitally controlled attenuators can be composed of multiple resistive elements 902a-902n connected in series or parallel using controllable switching elements 904a-904n such as JFETs, MOSFETs, MESFETs, or PHEMT transistors. The topology of the digitally controlled attenuator can be series, parallel, L-network, PI-network, T-network, etc. Figure 9 An example of a switching device implemented as a digitally controlled attenuator is schematically shown. Controllable switching elements 904a-904n, used to select resistive elements 902a-902n, can be digitally controlled according to a predetermined timing pattern. Generator unit 302 may also include a waveform encoder 612 configured to convert the waveform generated by digital waveform generator 606 into control signals for each controllable switching element 904a-904n. In particular, when the number of controllable switching elements 904a-904n is greater than the word length of each sample of the waveform, the waveform encoder 612 is preferred over directly generating control signals for each controllable switching element or storing the control signals for each controllable switching element in the memory of generator unit 302. The resulting RF waveform resembles a step, i.e., a quantized waveform, with steps small enough to reduce the RF spectrum. In other words, the quantized waveform allows the amplitude of the RF signal 305 to switch substantially smoothly from the first antenna port 306a to the second antenna port 306b. Word length refers to the resolution of the acquired digital samples, i.e., dynamic precision. For example, word length can be 4 bits to 24 bits. Figure 7B An example of the time-domain amplitude of the RF waveform of switching device 602b during a switching event is schematically shown, wherein the control signal of the second switching device 602b is a quantized linear ramp waveform generated by generator unit 302, including digital generator 606 and waveform encoder 612, to substantially smoothly boost the amplitude of the RF signal 305 at the second antenna port 306b. The target waveform is represented by dashed lines, and the quantized waveform is represented by solid lines (stepped lines). Figure 7B As can be seen, although the quantization waveform is formed by small steps, it approximates the target ramp waveform, i.e., the quantization waveform, which allows for a substantially smooth increase in the amplitude of the RF signal 305 at the second antenna port 306b. In this example, 4-bit quantization is used, but any other quantization method could be used. Figure 8B Showing with Figure 6C An example of the transmitted RF spectrum obtained together with the digital soft-switching system 310 is shown in the figure. From Figure 8B It can be seen that, with Figure 5Compared to the instantaneous switching shown, the unwanted emission level of the transmitted RF spectrum is reduced, and the reduction in the unwanted emission level of the transmitted RF spectrum is almost equal to... Figure 8A The simulated soft handover shown works just as well. Figure 8B In the example, for smaller offset frequencies (less than ±2.5 MHz from the transmit frequency), the out-of-channel spectral emission level may be between -45 dB and -15 dB; for larger offset frequencies (between ±2.5 MHz and ±10 MHz), the out-of-channel spectral emission level may be between -60 dB. Figure 8C Showing with Figure 6C Examples of adjacent channel leakage ratio (ACLR) of the digital soft handover system 310 at the transmit frequency and different offset frequencies are shown. Figure 8C As shown, ACLR is compared with instantaneous handover. In this example, the improvement in ACLR using the digital soft handover system 310 at the offset frequency is 20 dB or more compared to instantaneous (i.e., hard) handover.

[0056] Figure 6D Another exemplary embodiment of the antenna soft-switching system 310 according to the present invention is shown, wherein the generator unit 302 includes a counter 614, and the waveform is encoded to at least two switching devices 602a, 602b, i.e., the values ​​of the resistive elements 902a-902n of the switching devices 602a, 602b can be defined such that when the control signal is only counted as rising or falling, the resulting RF waveform approximates the desired waveform. This simplifies the generator unit 302 because it is not necessary to store the waveform in the memory of the generator unit 302. Otherwise, Figure 6D Operation of the soft handover system 310 Figure 6C It is similar to the soft handover system 310.

[0057] Due to size, cost, or RF performance considerations, it may be impractical to have resistor switching elements 602a and 602b at antenna ports 306a and 306b. This is especially true for digitally controlled attenuators, for example in… Figure 6C and Figure 6D The example antenna soft-switching system 310 is shown. In this case, a single centralized antenna soft-switching system 1000 is preferably used together with a switching network 1010 of antenna switches, including a plurality of switching devices of antenna switches configured to sequentially select at least one antenna element 332a-332n of antenna array 330. In this case, antenna soft-switching system 1000 can direct RF signal 305 to virtual load 1020 of reference port 1030, and the change of antenna elements 332a, 332b occurs at the moment when RF signal 305 is not present at any antenna port 306a, 306b.

[0058] Figure 10 An example embodiment of the antenna soft-switching system 1000 according to the present invention is shown, wherein the switching network 303 is a separate switching network providing the centralized antenna soft-switching system 1000. The switching network 303 is separate from the switching network 1010 of the antenna switch, i.e., a plurality of switching devices of the antenna switch are configured to sequentially select at least one antenna element 332a-332n of the antenna array 330. The generator unit 302 may be configured to control the switching network 303 such that the amplitude of the RF signal 305 at the first antenna port 306a decreases substantially smoothly, while the amplitude of the RF signal 305 at the reference port 1030 increases substantially smoothly. The switching network 1010 of the antenna switch is configured to change the active antenna port and active antenna element by connecting the RF signal path 305 from the first antenna port 306a to the second antenna port 306b while the RF signal 305 is directed to the dummy load 1020 of the reference port 1030. Subsequently, generator unit 302 can be configured to control switching network 303, such that the amplitude of RF signal 305 at reference port 1030 decreases substantially smoothly, while the amplitude of RF signal 305 at second antenna port 306b increases substantially smoothly. Figure 10 In the example antenna soft switching system 1000, the generator unit 302 includes a digital waveform generator 606 and a waveform encoder 612. Figure 11 An example time-domain amplitude of the RF waveforms of switching devices 602a, 602b and dummy load 1020 during a switching event is schematically shown, wherein the control signals of switching devices 602a and 602b are quantized linear ramp waveforms generated by generator unit 302 including digital generator 606 and waveform encoder 612.

[0059] A minor drawback of this embodiment is that the RF signal 305 entering the active antenna element (i.e., the first antenna element 332b) needs to be ramped down before the active antenna element is changed, and then ramped up again after activating the second antenna element 332b. This means that the uplink / downlink speed needs to be twice that of the embodiment, where the RF signal 305 switches from one antenna element to another. For example, in Figure 7A and Figure 7B In the example, the switching event lasts for 2 microseconds, during which the RF signal 305 switches from one antenna element to another. Figure 11 In the example, the duration of the switching event is also 2 microseconds, but during this time, the RF signal 305 switches from one antenna element to a dummy load and from the dummy load to another antenna element. However, if there is sufficient time for the switching event to complete, it is still possible to achieve an undesirable reduction in the transmitted RF spectrum.

[0060] According to an exemplary embodiment of the invention, if the transmitter module 320 is linear, or more precisely, nonlinear, the common centralized soft-switching system 1000 can also be implemented in the analog or digital baseband of the transmitter module 320. This eliminates the need for a dummy load 1020 to absorb RF signals and avoids losses at high power levels.

[0061] Figure 12 An example embodiment of the antenna soft-switching system 1200 according to the present invention is shown, wherein the switching network 303 is an independent switching network providing a centralized antenna soft-switching system 1200, and antenna ports 306a-306n and antenna elements 332a-332n are arranged into two groups, wherein the first antenna port 306a and the corresponding first antenna element 332a belong to the first antenna group 1210, and the second antenna port 306b and the corresponding second antenna element 332b belong to the second antenna port group 1220. The switching network 303 is separate from the switching networks 1010a of the first antenna group 1210 and 1010b of the second antenna group 1220 of the antenna switch, i.e., a plurality of switching devices of the antenna switch are configured to sequentially select at least one antenna element 332a-332n of the antenna array 330. Active antenna elements 332a-332n can be alternately selected from the first antenna group 1210 to form the second antenna group 1220. When the antenna group is not active, i.e., the RF signal 305 is not directed to the antenna group, selection of the active antenna ports and corresponding active antenna elements of the antenna group can be performed. For example, when the RF signal is directed to the first antenna group 1210, the second antenna port 306b can be pre-selected as an active antenna of the second antenna group 1220 by the switching network 1010b of the second antenna group 1220. Alternatively, when the RF signal 305 is directed to the second antenna group 1220, the first antenna port 306a can be pre-selected as an active antenna of the first antenna group 1210 by the switching network 1010a of the first antenna group 1220. To switch between the first antenna port 306a and the second antenna port 306b, the generator unit 302 can be configured to control the switching network 303 such that the amplitude of the RF signal 305 at the first antenna group 1210 (to which the first antenna port 306a belongs) decreases substantially smoothly, while the amplitude of the RF signal 305 at the second antenna group 1220 (to which the second antenna port 306b belongs) increases substantially smoothly, wherein the second antenna port 306b is preselected as the active antenna of the second antenna group 1220. This avoids the aforementioned drawbacks. If access from two RF paths is provided by antenna switches 1010a and 1010b, the two antenna groups 1210 and 1220 do not need to be exclusive; that is, any physical antenna element can belong to either group. Figure 12The dashed lines represent the switching network 1010b between the first antenna element 332a and the second antenna group 1220, and between the second antenna element 332b and the switching network 1010a of the first antenna group 1210. This allows for flexible switching sequences, where active antenna elements can be arbitrarily selected at each switching event.

[0062] The above describes different embodiments of the antenna soft-switching system 310, 1000, 1200 by referring to JFET, MOSFET, MESFET or PHEMT transistors, PIN diodes and / or digitally controlled attenuators as at least two resistive switching devices 602a, 602b. Optionally, fully or partially reactive, i.e., inductive or capacitive switching devices 602a, 602b can be used in any of the embodiments of the invention described above. Alternatively, in any of the embodiments of the invention described above, active switching elements 602a, 602b, such as amplifiers, can be used as at least two resistive switching devices 602a, 602b. The transfer function (i.e., gain) of the active switching device can be continuously variable (i.e., analog control signal) or digitally programmable (i.e., digital control signal).

[0063] Throughout this application, connections (i.e., communication couplings) between any components, modules, and / or units according to the invention (except between the transmitter unit and the receiver unit) can be based on any known wired communication technology. Communication between the transmitter unit and the receiver unit can be based on any known wireless communication technology, such as Bluetooth Low Energy (BLE).

[0064] The present invention relates to an antenna soft-switching system for an AoD direction-finding transmitter unit. Next, referring to... Figure 13 An example of an antenna soft-switching method according to the present invention is described. The method includes controlling the 1310 switching network 303 by means of a waveform generated by generator unit 302, so that the amplitude of the RF signal is switched substantially smoothly, i.e., gradually, from the first antenna port to the second antenna port, in order to reduce undesirable transmission levels of the radiated RF spectrum of the direction-finding transmitter as described above. During the switching event, the impedance seen by at least one RF port 304 can remain constant. Reference will be made to different embodiments of the method according to the present invention. Figures 14 to 16 Further description of control steps 1310.

[0065] In an exemplary embodiment of the method according to the invention, the switching network 303 is implemented as part of an antenna switch (configured to perform switching of the RF signal from the first antenna port 306a to the second antenna port 306b), i.e., the switching network 303 is an antenna switch (configured to change the active antenna port from the first antenna port 306a to the second antenna port 306b, and correspondingly change the active antenna element from the first antenna element 332a to the second antenna element 332b (e.g.)). Figures 6A-6D Example antenna soft-switching system 310) switching network. In other words, switching network 303 can be configured to switch RF signal 305 from first antenna port 306a to second antenna port 306b, so as to activate second antenna port 306b and antenna element 332b connected to second antenna port 306b, and deactivate (i.e. disconnect) first antenna port 306a and antenna element 332a connected to first antenna port 306a. As described above, control step 1310 may include: significantly and smoothly reducing (i.e. decreasing) the amplitude of RF signal 305 at first antenna port 306a 1410, and simultaneously significantly and smoothly increasing (i.e. increasing) the amplitude of RF signal 305 at second antenna port 306a 1420. This example embodiment of the method according to the invention... Figure 14 As shown in the image.

[0066] According to an example embodiment of the method of the present invention, the switching network 303 is a centralized soft handover system 1000 (e.g., Figure 10 A separate switching network (example antenna soft-switching system). The switching network 303 is separate from the switching network 1010 of the antenna switch, i.e., multiple switching devices of the antenna switch are configured to sequentially select at least one antenna element 332a-332n of the antenna array 330. Control step 1310 may include: substantially smoothly reducing the amplitude 1510 of the RF signal 305 at the first antenna port 306a, and simultaneously substantially smoothly increasing the amplitude 1520 of the RF signal 305 at the reference port 1030; as described above, changing (i.e. switching) the active antenna port and active antenna element 1530 by connecting the RF signal path from the first antenna port 306a to the second antenna port 306b through the switching network of the antenna switch, while directing the RF signal 305 to the virtual load 1020 of the reference port 1030, causing the amplitude of the RF signal 305 at the reference port 1030 to decrease substantially smoothly 1540, and simultaneously causing the amplitude of the RF signal 305 at the second antenna port 306b to increase substantially smoothly 1550. This example implementation of the method according to the invention is as follows: Figure 15 As shown.

[0067] Alternatively, according to an exemplary embodiment of the method of the present invention, the switching network 303 is an independent switching network providing a centralized antenna soft-switching system 1200, and the antenna ports 306a-306n and antenna elements 332a-332n are arranged into two groups, wherein the first antenna port 306a and the corresponding first antenna element 332a belong to the first antenna group 1210, and the second antenna port 306b and the corresponding second antenna element 332b belong to the second antenna port group 1220 (e.g., Figure 12 (Exemplary antenna soft-switching system). Control step 1310 may include: substantially smoothly reducing the amplitude 1610 of the RF signal 305 at the first antenna group 1210, and simultaneously substantially smoothly increasing the amplitude 1620 of the RF signal 305 at the second antenna group 1220, wherein, as described above, the second antenna port 306b is preselected as an active antenna of the second antenna group 1220. Figure 16 This example embodiment of the method according to the present invention is shown.

[0068] Besides the AoD transmitter unit 300, the antenna soft-switching system and method described above can also have other applications. For example, the antenna soft-switching system and method according to the present invention can be used to smooth transmitter power on / off transients in time-domain duplex (TDD) radios with a single antenna. Figure 10 Antenna soft switching system 1000 and Figure 15 The corresponding antenna soft-switching method may be best suited for this application. The antenna soft-switching system 1000 can be used at any point in a linear transmitter chain, or between a power amplifier (PA) and an antenna in the case of a nonlinear PA. Alternatively, the antenna soft-switching system and method according to the invention can be used as a programmable matched attenuator. The dimensions of at least two resistive switching designs 602a, 602b can be determined such that the switching network 303 maintains a constant impedance throughout the attenuation range. Figure 10 Antenna soft switching system 1000 and Figure 15 The corresponding antenna soft-switching method may be best suited for this application. Alternatively, the antenna soft-switching system and method according to the invention can be used to combine two or more antennas into a single transmitter or receiver port, with the power ratio between the two antennas adjustable. In the case of resistive switching devices, this would be a lossy combiner, but it may be useful in some applications, such as beamforming.

[0069] This invention includes antenna soft-switching systems 310, 1000, and 1200 for an AoD direction-finding transmitter unit, an antenna soft-switching method, and an AoD direction-finding transmitter unit including the antenna soft-switching systems 310, 1000, and 1200. All these aspects of the invention include the same sub-features, sub-components, and sub-functions included in the dependent system claims.

[0070] The specific examples provided in the description above should not be construed as limiting the applicability and / or interpretation of the appended claims. The lists and sets of examples provided in the description above are not exhaustive unless otherwise expressly stated.

Claims

1. An antenna soft-switching system (310, 1000, 1200) for a launch angle AoD direction finding transmitter unit (300), wherein, The antenna soft-switching system (310, 1000, 1200) is arranged between at least one radio frequency (RF) transmitter module (320) and at least one antenna array (330), and the antenna soft-switching system (310, 1000, 1200) includes: The timing unit (301) is used to obtain at least the start time of the switching event. The switching network (303) is configured on the RF signal path (305) between the RF port (304) and the first antenna port (306a) and the second antenna port (306b), and A generator unit (302) is used to generate at least one waveform for controlling the switching network (303). The generator unit (302) is configured to reduce the level of unwanted transmission of the RF spectrum of the AoD direction finding transmitter unit (300) by controlling the switching network (303) to smoothly switch the amplitude of the RF signal (305) from the first antenna port (306a) to the second antenna port (306b).

2. The soft handover system (310, 1000, 1200) according to claim 1, wherein, The switching network (303) includes at least two switching devices (602a, 602b), which are resistive switching devices, fully reactive switching devices, partially reactive switching devices, or active switching devices.

3. The soft handover system (310, 1000, 1200) according to claim 2, wherein, The at least two switching devices (602a, 602b) utilize junction-gate field-effect transistors (JFETs) and metal-oxide-semiconductor field-effect transistors (MOSFETs). Metal-Semiconductor Field-Effect Transistor (MESFET); Phenomoid High Electron Mobility Transistor (PHEMT); or PIN diode.

4. The soft handover system (310, 1000, 1200) according to any one of the preceding claims, wherein, The generator unit (302) includes a simulated ramp generator.

5. The soft handover system (310, 1000, 1200) according to any one of claims 1 to 3, wherein, The generator unit (302) includes a digital waveform generator (606), a digital-to-analog converter (608), and a reconstruction filter (610).

6. The soft handover system (310, 1000, 1200) according to any one of claims 1 or 2, wherein, At least two resistive switching devices (602a, 602b) are digitally controlled attenuators.

7. The soft handover system (310, 1000, 1200) according to claim 6, wherein, The generator unit (302) includes a digital waveform generator (606) and a waveform encoder (612), which is configured to convert the waveform generated by the digital waveform generator (606) into a control signal for the digital control attenuator.

8. The soft handover system (310, 1000, 1200) according to claim 6, wherein, The generator unit (302) includes a counter (614), and the waveform is encoded into the at least two switching devices (602a, 602b).

9. The soft handover system (310) according to any one of claims 1 to 3, wherein, The switching network (303) is implemented as part of an antenna switch configured to change the active antenna port from the first antenna port (306a) to the second antenna port (306b) during the switching event, wherein the generator unit (302) is configured to control the switching network (303) such that: The amplitude of the RF signal (305) at the first antenna port (306a) decreases smoothly, and at the same time, the amplitude of the RF signal (305) at the second antenna port (306b) increases smoothly.

10. The soft handover system (1000) according to any one of claims 1 to 3, wherein, The switching network (303) is a separate switching network providing a centralized soft handover system, wherein the generator unit (302) is configured to control the switching network (303) so as to: The amplitude of the RF signal (305) at the first antenna port (306a) decreases smoothly, and Simultaneously, the amplitude of the RF signal (305) at the reference port (1030) rises smoothly, wherein the antenna switch is configured to change the active antenna port while the RF signal (305) is directed to the reference port (1030), and The generator unit (302) is also configured to control the switching network (303) such that the amplitude of the RF signal (305) at the reference port (1030) decreases smoothly while the amplitude of the RF signal (305) at the second antenna port (306b) increases smoothly.

11. The soft handover system (1200) according to any one of claims 1 to 3, wherein, The switching network (303) is an independent switching network providing a centralized soft handover system, and the first antenna port (306a) belongs to the first antenna group (1210), and the second antenna port (306b) belongs to the second antenna group (1220), wherein the generator unit (302) is configured to control the switching network (303) such that: The amplitude of the RF signal (305) in the first antenna group (1210) decreases smoothly. Meanwhile, the amplitude of the RF signal (305) of the second antenna group (1220) rises smoothly, wherein the second antenna port (306b) is preselected as the active antenna of the second antenna group (1220).

12. A launch angle (AoD) direction finding transmitter unit (300) comprising the antenna soft switching system (310, 1000, 1200) according to any one of claims 1 to 11.

13. An antenna soft-switching method for an AoD direction-finding transmitter unit (300), wherein, The antenna soft switching is performed between at least one RF transmitter module (320) and at least one antenna array (330), and the method includes reducing the unwanted transmission level of the transmitted RF spectrum of the AoD direction finding transmitter unit (300) by smoothly switching the amplitude of the RF signal (305) from the first antenna port (306a) to the second antenna port (306b) through a waveform control (1310) switching network (303) generated by the generator unit (302).

14. The soft handover method according to claim 13, wherein, The switching network (303) is implemented as part of an antenna switch that changes the active antenna port from the first antenna port (306a) to the second antenna port (306b) during a switching event, wherein the control (1310) of the switching network (303) includes: Smoothly reduce (1410) the amplitude of the RF signal (305) at the first antenna port (306a), and At the same time, the amplitude of the RF signal (305) at the second antenna port (306b) is smoothly increased (1420).

15. The soft handover method according to claim 13, wherein, The switching network (303) is an independent switching network that provides a centralized soft switching system, wherein the control (1310) of the switching network (303) includes: Smoothly reduce (1510) the amplitude of the RF signal (305) at the first antenna port (306a), Simultaneously, the amplitude of the RF signal at the reference port (1030) is smoothly increased (1520). The active antenna port is changed (1530) from the first antenna port (306a) to the second antenna port (306b) by the switching network of the antenna switch, while the RF signal is directed to the reference port (1030). Smoothly reduce (1540) the amplitude of the RF signal (305) at the reference port (1030), and At the same time, the amplitude of the RF signal (305) at the second antenna port (306b) is smoothly increased (1550).

16. The soft handover method according to claim 13, wherein, The switching network (303) is an independent switching network providing a centralized soft handover system, and the first antenna port (306a) belongs to the first antenna group (1210), and the second antenna port (306b) belongs to the second antenna group (1220), wherein the method includes: Smoothly reduce (1610) the amplitude of the RF signal (305) in the first antenna group (1210), and Simultaneously, the amplitude of the RF signal (305) in the second antenna group (1220) is smoothly increased (1620), wherein the second antenna port (306b) is preselected as an active antenna of the second antenna group (1220).

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