Out-of-band radio frequency emissions filtering

Abstract

This application relates to a method and system for out-of-band radio frequency (RF) emission filtering. A system filters out out-of-band RF emissions generated by a first transmitter's wireless transmission of a first signal from a second transmitter's wireless transmission. The first signal is transmitted from the first transmitter to the second transmitter via one or more wired connections. The out-of-band portion of the modulated first signal is inverted to generate an inverted out-of-band component signal. The inverted out-of-band component signal is combined with a second signal from the second transmitter to produce a filtered second signal. The filtered second signal is wirelessly transmitted from the second transmitter concurrently with the first transmitter's wireless transmission of the first signal, wherein the second transmitter's wireless transmission of the inverted out-of-band component signal in the filtered second signal is synchronized with the first transmitter's wireless transmission of the first signal.

Description

[0001] This invention patent application is a divisional application of the invention patent application with international application number PCT / US2021 / 026744, international application date of April 10, 2021, application number 202180038822.7 that entered the Chinese national phase, and titled "Out-of-band Radio Frequency Emission Filtering". Background Technology

[0002] Modern electronic communication devices typically provide component circuitry systems for multiple wireless communication modes, such as Bluetooth, Wi-Fi, LTE, and 5G. In some implementations, a wireless transmitter (e.g., Bluetooth) labeled as an "attacker" transmitter can emit pseudo-out-of-band radio frequency (RF) emissions residing outside the channel bandwidth (e.g., caused by modulation processes and nonlinearities in the transmitter). For example, an out-of-band RF emission from an RF source (e.g., a Bluetooth transmitter) might include the second and third harmonics of a carrier signal located outside the channel bandwidth (e.g., outside the 2.402 GHz to 2.480 GHz range). Summary of the Invention

[0003] The described technique filters out out-of-band radio frequency emissions generated by the wireless transmission of a first signal by a first transmitter from the wireless transmission of a second transmitter. The first signal is transmitted from the first transmitter to the second transmitter via one or more wired connections. The out-of-band portion of the modulated first signal is inverted to generate an inverted out-of-band component signal. This inverted out-of-band component signal is combined with a second signal from the second transmitter to produce a filtered second signal. The filtered second signal is wirelessly transmitted from the second transmitter concurrently with the wireless transmission of the first signal by the first transmitter, wherein the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter is synchronized with the wireless transmission of the first signal by the first transmitter.

[0004] This summary is provided to introduce, in a simplified form, some concepts that will be further described in the following detailed embodiments. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0005] This article also describes and lists other implementations. Attached Figure Description

[0006] Figure 1 An example communication device including a first transmitter and a second transmitter is illustrated.

[0007] Figure 2 An example system is illustrated for filtering out out-of-band radio frequency emissions generated by the attacker's wireless transmission of RF signals from the victim's transmitter's wireless transmissions.

[0008] Figure 3 An example operation for filtering out out-of-band radio frequency emissions is illustrated.

[0009] Figure 4 Examples of various signal components related to filtering out out-of-band radio frequency emissions are shown.

[0010] Figure 5 An example operating environment and system for filtering out out-of-band radio frequency emissions are illustrated. Detailed Implementation

[0011] Out-of-band radio frequency (RF) emissions can then couple with signals in nearby Wi-Fi transmitters (“victim” transmitters), for example, as noise. Unintentionally, the power amplifier of a Wi-Fi transmitter amplifies noise as it transmits its own Wi-Fi signal, which might be centered at 2.4 GHz or 5 GHz. This combination results in the amplification of the victim transmitter's out-of-band RF emissions. Thus, out-of-band RF emissions degrade the performance of a Wi-Fi transmitter by introducing and amplifying noise into the Wi-Fi transmission. Hardware bandpass filters can be used to attempt to mitigate the negative effects of such out-of-band RF emissions, but these are expensive, inefficient if the antenna uses a close frequency, and ineffective at filtering out out-of-band RF emission noise coupled within the victim transmitter's RF power amplifier (the power amplifier). An RF power amplifier is an electronic amplifier that converts a low-power RF signal into a higher-power signal to drive the transmitter antenna. The described techniques can be implemented in hardware, software, or a combination of both to filter out out-of-band RF emissions without relying on such hardware bandpass filters.

[0012] The Bluetooth and Wi-Fi wireless technologies described herein are used as example wireless communication technologies, but it should be understood that the described technologies can be used with other wireless communication technologies, including but not limited to various mobile phone standards (e.g., LTE, 5G). In one implementation, Bluetooth wireless technology uses shortwave UHF RF waves from 2.402 GHz to 2.480 GHz to exchange data over short distances, while Wi-Fi wireless technology uses a radio frequency range including 900 MHz, 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, 5.9 GHz, and 60 GHz bands to exchange data. When the channel bandwidth used by neighboring wireless transmitters is similar, out-of-band RF emissions from an “attacker” wireless transmitter may “leak” out of the attacker’s wireless transmitter and couple with the transmitted signal of the “victim” wireless transmitter, resulting in out-of-band RF emissions from the victim’s wireless transmitter. In some cases, such coupling may occur within the power amplifier of the victim’s wireless transmitter, resulting in the out-of-band RF emissions being amplified in the victim’s wireless transmission.

[0013] Figure 1 An example communication device 100 is illustrated, including a first transmitter 102 and a second transmitter 104. The transmitters are positioned adjacent to each other within the frame of the communication device 100. The two transmitters have different channel bandwidths. In one example, the first transmitter 102 is a Bluetooth transmitter with a channel bandwidth in the range of 2.402 GHz to 2.480 GHz, while the second transmitter 104 is a Wi-Fi transmitter with a channel bandwidth centered at 2.4 GHz or 5 GHz.

[0014] As shown by the dashed circle representing radiation emitted from the first transmitter 102, a first radio frequency (RF) signal 106 can be radiated from the first transmitter 102 and reach the second transmitter 104. Typically, the channel bandwidths of the first transmitter 102 and the second transmitter 104 do not overlap or are otherwise protected against in-band noise from the other transmitter. However, some transmitter leakage can reach out-of-band RF emissions (e.g., second and / or third harmonics) from a nearby transmitter. In this sense, "out-of-band" refers to transmitted RF energy outside the transmitter's channel bandwidth (e.g., energy emitted by a Bluetooth transmitter outside the 2.402 GHz to 2.480 GHz range, or energy emitted by a Wi-Fi transmitter outside the 2.4 GHz or 5 GHz channel).

[0015] A transmitter whose out-of-band radio frequency (RF) emissions are leaked and coupled into another transmitter is referred to herein as the “attacker” transmitter. A transmitter experiencing such coupling of the attacker’s RF emissions is referred to herein as the “victim” transmitter. The attacker’s RF emissions can electromagnetically couple to components of the transmitter (e.g., a power amplifier), thereby introducing noise into the victim transmitter’s transmission. For example, in the case where the component is a power amplifier, the out-of-band noise can actually be amplified in the victim transmitter’s wireless transmission.

[0016] It should be understood that a victim transmitter can also leak out-of-band radio frequency emissions and inject out-of-band noise into the transmission of another victim transmitter in communication equipment 100. The RF emission energy 108 of the second transmitter 104 is in Figure 1 As shown in the image.

[0017] Figure 2An example system 200 is illustrated for filtering out out-of-band radio frequency (RF) emissions 202 generated by the wireless transmission of RF signals by the attacker transmitter 204 from the wireless transmissions of the victim transmitter 206. Typically, the channel bandwidths of the attacker transmitter 204 and the victim transmitter 206 do not overlap or are otherwise protected against in-band noise from other transmitters (e.g., hardware filters). However, some transmitter leakage can reach out-of-band RF emissions (e.g., second and / or third harmonics) from another nearby transmitter. In this sense, "out-of-band" refers to transmitted RF energy outside the transmitter's channel bandwidth (e.g., energy transmitted by a Bluetooth transmitter outside the 2.402 GHz to 2.480 GHz range, or energy transmitted by a Wi-Fi transmitter outside the 2.4 GHz or 5 GHz channel).

[0018] Figure 2 The example scenario presented depicts an attacker transmitter 204 (e.g., a Bluetooth transmitter) leaking out-of-band radio frequency emission 202 (i.e., RF energy) coupled to components of the victim transmitter 206. The attacker transmitter 204 and the victim transmitter 206 are connected via one or more wired connections within a communication device. For example, a synchronization signal 208 and an attacker signal 210 are transmitted between the attacker transmitter 204 and the victim transmitter 206 via one or more wired connections.

[0019] The victim transmitter 206 includes a power amplifier 212 (power amplifier) ​​that amplifies low-power RF signals for transmission via antenna 214. During transmission, the victim transmitter 206 and antenna 214 typically transmit in-band RF energy within the channel bandwidth of the victim transmitter 206 (e.g., within the Wi-Fi frequency range). During transmission, the attacker transmitter 204 and its corresponding antenna 216 typically transmit in-band RF energy within the channel bandwidth of the attacker transmitter 204 (e.g., within the Bluetooth frequency range). However, in some scenarios, the attacker transmitter 204 may also transmit out-of-band RF energy during transmission (referred to as out-of-band RF emission 202 or out-of-band RF emission). Such out-of-band RF emission 202 can be coupled to the circuitry in the victim transmitter 206 and introduced as noise into the wireless transmission of the victim transmitter 206.

[0020] In various implementations, system 200 can cancel or reduce such noise in the wireless transmission of victim transmitter 206. Before wirelessly transmitting a signal (e.g., attacker signal 210), attacker transmitter 204 first transmits attacker signal 210 to victim transmitter 206 via one or more wired connections. Victim transmitter 206 combines aspects of attacker signal 210 with its own transmitted signal to filter out or eliminate out-of-band RF emissions from its wireless transmission.

[0021] Various implementations exist for distributing signal processing operations between attacker transmitter 204 and victim transmitter 206. In one implementation, attacker signal 210 receives (e.g., via a wired connection) an unmodulated symbol sequence. Victim transmitter 206 receives the unmodulated attacker signal 210. A signal modulator 220, which may include hardware and software, modulates the out-of-band portion of attacker signal 210 into a modulated (e.g., Wi-Fi format) signal from the victim transmitter. A signal inverter 224, which may include hardware and software, inverts the modulated out-of-band portion of attacker signal 210. A signal combiner 226, which may include hardware and / or software, combines the modulated, inverted out-of-band portion of attacker signal 210 into the victim transmitter's own transmitted signal to produce a filtered second signal that cancels out the effect of the out-of-band RF transmission 202 on its own transmission. In other implementations, victim transmitter 206 modulates its own signal together with the inverted symbols from attacker transmitter 204 without requiring a separate hardware signal combiner 226. Conversely, the signal combiner 226 could be part of the modulator in the victim transmitter 206. Other implementations are also envisioned.

[0022] As discussed below, the transmission timing of the modulated, inverted out-of-band portion of the attacker's signal 210 is synchronized with the wireless transmission of the attacker's signal by the attacker's transmitter 204 to satisfy synchronization timing conditions. In one example, they satisfy synchronization timing conditions if the transmission timings are sufficiently synchronized to match or be highly correlated, although other synchronization timing conditions may be defined. Such conditions can be determined based on their effectiveness in eliminating or reducing out-of-band noise (e.g., out-of-band noise conditions) induced by the attacker's transmitter in the victim's wireless transmission.

[0023] Furthermore, the modulated, inverted out-of-band portion of the attacker's signal 210 in the wireless transmission signal combined with the victim transmitter 206 is amplitude-matched (or highly correlated) with the out-of-band RF transmission 202 received by the victim transmitter 206 to satisfy an amplitude matching condition. In one example, they satisfy an amplitude matching condition if the amplitudes are sufficiently matched or highly correlated, although other amplitude matching conditions can be defined. Such conditions can be determined based on their effectiveness in eliminating or reducing out-of-band noise (e.g., out-of-band noise conditions) induced by the attacker transmitter in the victim transmitter's wireless transmission.

[0024] In combination, the satisfaction of synchronization timing conditions and / or amplitude matching conditions results in the out-of-band noise level in the victim transmitter's wireless transmission signal meeting an overall out-of-band noise condition (e.g., the out-of-band noise level is below a specified threshold). In this way, noise generated by the attacker's out-of-band RF emissions coupled into the victim transmitter's transmission signal can be canceled or reduced without the need for additional hardware bandpass filters.

[0025] In another implementation, most of the signal processing for the attacker's signal 210 can be performed by the attacker transmitter 204. In this implementation, the attacker's signal 210 is modulated by a signal modulator 222 in the attacker transmitter 204, which may include both hardware and software. The signal modulator 222 modulates the out-of-band portion of the attacker's signal 210 in the modulation format of the victim transmitter 206. Furthermore, before the attacker transmitter 204 transmits the attacker's signal 210 to the victim transmitter 206 in the modulated format, a signal inverter 225 in the attacker transmitter 204 inverts the modulated out-of-band portion of the attacker's signal 210. This implementation can also eliminate or reduce noise generated by the coupling between the attacker's out-of-band RF transmission and the victim transmitter's transmitted signal without requiring an additional hardware bandpass filter.

[0026] In other implementations, modulation and inversion operations can be assigned in various combinations between the attacker transmitter 204 and the victim transmitter 206. This implementation can also eliminate or reduce noise generated by the coupling of the attacker transmitter's out-of-band RF emissions with the victim transmitter's transmitted signals without the need for additional hardware bandpass filters.

[0027] As discussed above, the amplitude of the inverted out-of-band component signal in the filtered second signal is adapted to match or be highly correlated with the amplitude of the out-of-band RF transmission actually coupled into the victim transmitter 206. In one implementation, the amplitude matcher 227 may monitor the received out-of-band RF transmission 202 actually received by the victim transmitter 206 from the attacker transmitter 204, estimate the power density of the received out-of-band RF transmission 202, and adjust the amplitude of the modulated, inverted out-of-band portion of the attacker signal 210, combined with the victim transmitter's own transmission signal, to match or be highly correlated with the amplitude of the received out-of-band RF transmission 202.

[0028] As discussed previously, the timing of the wireless transmissions of the attacker transmitter 204 and the victim transmitter 206 is synchronized, such that the victim transmitter 206 transmits the inverted out-of-band portion of the attacker signal 210 simultaneously with the attacker transmitter 204 transmitting the attacker signal. Therefore, a transmitter synchronizer 228, which may include hardware and software, generates a synchronization signal 208 to synchronize the victim transmitter's wireless transmission of the inverted out-of-band component of the filtered second signal with the attacker transmitter's wireless transmission of the attacker signal. The transmitter synchronizer 228 passes the synchronization signal 208 to the transmitter synchronizer 230 of the attacker transmitter 204 to match or highly correlate the timing of the respective wireless transmissions.

[0029] In one implementation, the timing error between the attacker's signal and the filtered second signal can be reduced or eliminated by timing-shifting the modulated signal of the victim transmitter 206 until the out-of-band power density meets a power density condition (e.g., below a programmable threshold). Once the appropriate timing is determined, the victim transmitter 206 can request the attacker transmitter 204 to transmit its symbols at the appropriate timing, if necessary. The better the synchronization match between the attacker's signal and the inverted out-of-band portion of the attacker's signal, the better the noise is eliminated or reduced from the victim transmitter 204.

[0030] In another implementation, the victim transmitter 206 may receive time synchronization information corresponding to out-of-band symbol timing and transmitted by the attacker transmitter 204. The victim transmitter 206 may then use this time synchronization information to perform clock-based synchronization between the two transmitters, so that the transmission of the filtered second signal by the victim transmitter 206 is synchronized with the transmission of the corresponding symbol by the attacker transmitter 204.

[0031] In one implementation, the synchronization signal 208 may include a shift delay instructing the attacker transmitter 204 to delay the wireless transmission of its attacker signal by a period of time or a number of clock cycles, so that the out-of-band RF transmission 202 is synchronized with the wireless transmission of the inverted out-of-band component signal in the filtered victim signal. In one implementation, synchronization may be achieved using an adaptive filter to adjust the synchronization signal 208 based on power density measurements or an estimate of the out-of-band energy of the victim transmitter 206 in the wireless transmission, although other synchronization methods may also be employed. These different implementations allow for variations in transmitter design, enabling any one or two transmitters to be responsible for synchronizing the out-of-band RF transmissions 202 of the filtered victim signal with the attacker signal.

[0032] Figure 3An example operation 300 for filtering out-of-band radio frequency transmissions is illustrated. Communication operation 302 transmits a first signal (e.g., an attacker's signal) from a first transmitter to a second transmitter via one or more wired connections. The transmitted attacker's signal may be a symbol sequence to be transmitted by the first transmitter or a signal-processed version of those symbols (e.g., inverted and / or modulated in the modulation format of the second transmitter). If the first transmitter's signal modulator does not modulate the first signal into the modulation format of the second transmitter, the second transmitter's signal modulator will perform modulation on the out-of-band portion of the attacker's signal.

[0033] Inversion operation 304 inverts the out-of-band portion of the first signal to generate an inverted out-of-band component signal. Typically, inversion can be performed by either transmitter. Examples include using a 180-degree phase-shifted version of the signal and applying an inverter to a modulated signal without phase change. In one implementation, inversion operation 304 can be performed by a signal inverter in the first transmitter. If the out-of-band portion of the first signal is not inverted by the first transmitter (e.g., by a signal inverter), then the signal inverter of a second transmitter will perform the inversion. In another implementation, inversion can be performed before modulation by either transmitter, for example, in the form of a 180-degree phase change applied to each symbol.

[0034] Combination operation 306 combines the inverted out-of-band component signal with the second signal from the second transmitter to generate a filtered signal. Synchronous transmission operation 308 concurrently transmits the filtered second signal wirelessly from the second transmitter with the first signal transmitted wirelessly from the first transmitter. Performing concurrent wireless transmission synchronizes the wireless transmission of the inverted out-of-band component signal from the filtered second signal by the second transmitter with the wireless transmission of the first signal by the first transmitter.

[0035] In another implementation, the attacker transmitter sends information about the frequency distribution of its signal, such as identifying out-of-band transmission bands or subcarrier frequencies. In one implementation, the attacker transmitter sends information about the second harmonic frequency of its signal to the victim transmitter, which uses this information to place inverted symbols at the appropriate subcarrier frequency.

[0036] In one implementation, an adjustment operation (not shown) adjusts the amplitude of the inverted out-of-band component signal to satisfy an amplitude condition. In one implementation, the amplitude condition is satisfied if the amplitude of the inverted out-of-band component signal matches or is highly correlated with the amplitude of the out-of-band RF transmission received from the first transmitter in a wireless transmission of the first signal. In another implementation, the amplitude condition is satisfied if the amplitude of the out-of-band energy in the RF signal transmitted by the second transmitter is below an acceptable threshold. Other variations of the amplitude condition may also be employed. The better the amplitude matching, the better the noise cancellation or reduction effect from the victim transmitter.

[0037] Figure 4 Various signal components 400 related to filtering out out-of-band radio frequency transmissions are illustrated. The first figure, titled "Transmitting Information with Digital Signals," depicts a digital signal (attacker signal) represented as a symbol sequence. The second figure, titled "Serial Symbols Modulated by M-Array QAM at the Transmitter," depicts the symbol sequence corresponding to the digital signal in the first figure.

[0038] The third figure, titled "M-array QAM Modulation Waveform Based on Symbol Information," depicts the out-of-band portion of the attacker's signal in the victim transmitter's modulation format. The fourth figure, titled "M-array QAM Modulation Waveform Based on Inverted Symbol Information," depicts the out-of-band portion of the attacker's signal in the victim transmitter's modulation format after inversion. The fifth figure, titled "OOB Cancellation Using Inverse Modulation Techniques," depicts the result of synchronizing the attacker's transmission of the attacker's signal with the inverted version of the attacker's signal in the victim transmitter's modulated format. As shown in the fifth figure, out-of-band (OOB) energy is canceled. The sixth figure, titled "OOB Cancellation Using ½ Symbol Shift Inverse Modulation Techniques," depicts the non-zero OOB energy resulting from the lack of synchronization between the victim transmitter's transmission of the attacker's signal and the inverted version of the attacker's signal in the victim transmitter's modulated format.

[0039] Figure 5 An example communication device 500 for implementing the described technology is shown. The communication device 500 can be a client device, such as a laptop, mobile device, desktop computer, tablet; server / cloud device; Internet of Things device; electronic accessory; or other electronic device. The communication device 500 includes one or more processors 502 and a memory 504. The memory 504 generally includes both volatile memory (e.g., RAM) and non-volatile memory (e.g., flash memory). An operating system 510 resides in the memory 504 and is executed by the processors 502.

[0040] In example communication device 500, such as Figure 5 As shown, one or more modules or segments (such as communication software 550, application modules, transmitter synchronizers, amplitude matchers, signal combiners, signal inverters, signal modulators, and other modules) are loaded into the operating system 510 on memory 504 and / or storage 520 and executed by processor 502. Storage 520 may store communication parameters, signal data, and other data and may be local to communication device 500, or it may be remote and communicatively connected to communication device 500.

[0041] The communication device 500 includes a power supply 516, which is powered by one or more batteries or other power sources and supplies power to other components of the communication device 500. The power supply 516 may also be connected to an external power source for overclocking or recharging the built-in battery or other power source.

[0042] The communication device 500 may include one or more communication transceivers 530, which can be connected to one or more antennas 532 to provide network connectivity (e.g., mobile phone networks, Wi-Fi®, Bluetooth®) to one or more other server and / or client devices (e.g., mobile devices, desktop computers, or laptop computers). The communication device 500 may further include a network adapter 536, which is a type of communication device. The communication device 500 can use this adapter and any other type of communication device to establish connections on a wide area network (WAN) or local area network (LAN). It should be understood that the network connections shown are exemplary, and other communication devices and apparatuses for establishing communication links between the communication device 500 and other devices can be used.

[0043] The communication device 500 may include one or more input devices 534 (e.g., a keyboard or mouse) that allow a user to input commands and information. These and other input devices may be coupled to the server via one or more interfaces 538, such as a serial port interface, a parallel port, or a universal serial bus (USB). The communication device 500 may also include a display 522, such as a touchscreen display.

[0044] The communication device 500 may include a wide variety of tangible processor-readable storage media and intangible processor-readable communication signals. Tangible processor-readable storage can be embodied by any available medium accessible to the communication device 500, and includes both volatile and non-volatile storage media, and removable and non-removable storage media. Tangible processor-readable storage media excludes communication signals, but includes volatile and non-volatile, removable and non-removable storage media implemented using any method or technology for storing information such as processor-readable instructions, data structures, program modules, or other data. Tangible processor-readable storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic tape cassettes, magnetic tape, disk storage or other magnetic storage devices, or any other tangible medium that can be used to store desired information and is accessible to the communication device 500. In contrast to tangible processor-readable storage media, intangible processor-readable communication signals can embody processor-readable instructions, data structures, program modules, or other data using modulated data signals such as carrier waves or other signal transmission mechanisms. The term "modulated data signal" refers to a signal in which one or more characteristics are set or altered by encoding information in the signal. As an example, and not a limitation, intangible communication signals include signals that propagate through wired media (such as wired networks or direct wired connections) and wireless media (such as acoustic, RF, infrared, and other wireless media).

[0045] Although this specification contains numerous specific implementation details, these should not be construed as limiting the scope of any invention or potentially claimed content, but rather as descriptions of features specific to particular embodiments of the described techniques. In this specification, certain features described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable sub-combination. Furthermore, while features may be described above as operating in certain combinations and even initially claimed in this way, one or more features from a claimed combination may be removed from that combination in some cases, and the claimed combination may be for sub-combinations or variations thereof.

[0046] Similarly, although operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring these operations to be performed in the specific order shown or in sequential order, or that all illustrated operations be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of the various system components in the above embodiments should not be construed as requiring such separation in all embodiments, but rather it should be understood that the described program components and systems can generally be integrated into a single software product or packaged into multiple software products.

[0047] An example method is provided for filtering out out-of-band radio frequency emissions generated by a wireless transmission of a first signal by a first transmitter from a wireless transmission of a second transmitter. The method includes: transmitting the first signal from the first transmitter to the second transmitter via one or more wired connections; inverting the out-of-band portion of the modulated first signal to generate an inverted out-of-band component signal; combining the inverted out-of-band component signal with a second signal from the second transmitter to generate a filtered second signal; and wirelessly transmitting the filtered second signal from the second transmitter concurrently with the wireless transmission of the first signal by the first transmitter, wherein the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter is synchronized with the wireless transmission of the first signal by the first transmitter.

[0048] Another example method of any of the foregoing methods is provided, wherein the transmission includes modulating the first signal into a modulated format at the first transmitter; and receiving the first signal in a modulated format from the first transmitter at the second transmitter.

[0049] Another example method of any of the foregoing methods is provided, wherein the transmission includes receiving the first signal as a symbol sequence from the first transmitter in an unmodulated format at the second transmitter; and in response to receiving the first signal, modulating the symbol sequence into the first signal in a modulated format at the second transmitter.

[0050] Another example of any of the foregoing methods further includes: transmitting a synchronization signal between the first transmitter and the second transmitter via the one or more wired connections, the synchronization signal indicating timing information for synchronizing the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter with the wireless transmission of the first signal by the first transmitter.

[0051] Another example method is provided for any of the foregoing methods, wherein the out-of-band portion of the modulated first signal includes energy outside the channel bandwidth of the second transmitter.

[0052] Another example method is provided for any of the foregoing methods, wherein the out-of-band portion of the modulated first signal includes energy outside the channel bandwidth of the first transmitter.

[0053] Another example of any of the foregoing methods further includes: adjusting the amplitude of the inverted out-of-band component signal to be highly correlated with the amplitude of the out-of-band radio frequency transmission received from the first transmitter in the wireless transmission of the first signal.

[0054] An example system for filtering out-of-band radio frequency (RF) emissions is provided, comprising: a first transmitter; a second transmitter; one or more wired connections configured to transmit a first signal from the first transmitter to the second transmitter; a signal inverter configured to invert an out-of-band portion of the modulated first signal to generate an inverted out-of-band component signal; a signal combiner configured to combine the inverted out-of-band component signal with a second signal from the second transmitter to generate a filtered second signal; and a transmitter synchronizer configured to wirelessly transmit the filtered second signal by the second transmitter concurrently with the wireless transmission of the first signal by the first transmitter, wherein the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter is synchronized with the wireless transmission of the first signal by the first transmitter.

[0055] Another example system is provided for any of the aforementioned systems, wherein the first transmitter is configured to modulate the first signal into a modulated format; and the second transmitter is configured to receive the first signal from the first transmitter in a modulated format at the second transmitter.

[0056] Another example system is provided for any of the aforementioned systems, wherein the second transmitter is configured to receive the first signal as a symbol sequence from the first transmitter in an unmodulated format and modulate the symbol sequence into the first signal in a modulated format.

[0057] Another example system is provided for any of the aforementioned systems, wherein the one or more wired connections are configured to transmit a synchronization signal between the first transmitter and the second transmitter, the synchronization signal indicating timing information for synchronizing the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter with the wireless transmission of the first signal by the first transmitter.

[0058] Another example system is provided for any of the aforementioned systems, wherein the out-of-band portion of the modulated first signal includes energy beyond the channel bandwidth of the second transmitter.

[0059] Another example system is provided for any of the aforementioned systems, wherein the out-of-band portion of the modulated first signal includes energy beyond the channel bandwidth of the first transmitter.

[0060] Another example system of any of the foregoing systems further includes: an amplitude matcher configured to adjust the amplitude of the inverted out-of-band component signal to be highly correlated with the amplitude of the out-of-band radio frequency transmission received from the first transmitter in the wireless transmission of the first signal.

[0061] A tangible processor-readable storage medium of one or more tangible articles encoding processor-executable instructions for execution on an electronic communication device provides a process for filtering out out-of-band radio frequency emissions generated by a wireless transmission of a first signal by a first transmitter from a wireless transmission of a second transmitter. The process includes: transmitting the first signal from the first transmitter to the second transmitter via one or more wired connections; inverting the out-of-band portion of the modulated first signal to generate an inverted out-of-band component signal; combining the inverted out-of-band component signal with a second signal from the second transmitter to generate a filtered second signal; and wirelessly transmitting the filtered second signal from the second transmitter concurrently with the wireless transmission of the first signal by the first transmitter, wherein the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter is synchronized with the wireless transmission of the first signal by the first transmitter.

[0062] One or more other examples of tangible processor-readable storage media are provided for any of the aforementioned storage media, wherein the transmission includes: modulating the first signal into a modulated format at the first transmitter; and receiving the first signal in a modulated format from the first transmitter at the second transmitter.

[0063] One or more other examples of tangible processor-readable storage media are provided for any of the aforementioned storage media, wherein the transmission includes: receiving the first signal as a symbol sequence from the first transmitter in an unmodulated format at the second transmitter; and modulating the symbol sequence into the first signal in a modulated format at the second transmitter in response to receiving the first signal.

[0064] One or more other examples of the aforementioned storage media are tangible processor-readable storage media, wherein the process further includes: transmitting a synchronization signal between the first transmitter and the second transmitter via the one or more wired connections, the synchronization signal indicating timing information for synchronizing the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter with the wireless transmission of the first signal by the first transmitter.

[0065] One or more other examples of tangible processor-readable storage media are provided, wherein the out-of-band portion of the modulated first signal includes energy beyond the channel bandwidth of the second transmitter.

[0066] One or more other examples of tangible processor-readable storage media are provided for any of the aforementioned storage media, wherein the process further includes: adjusting the amplitude of the inverted out-of-band component signal to be highly correlated with the amplitude of the out-of-band radio frequency transmission received from the first transmitter in the wireless transmission of the first signal.

[0067] An example system is provided for filtering out out-of-band radio frequency emissions generated by a first transmitter's wireless transmission of a first signal from a wireless transmission of a second transmitter. The system includes: means for transmitting the first signal from the first transmitter to the second transmitter via one or more wired connections; means for inverting the out-of-band portion of the modulated first signal to generate an inverted out-of-band component signal; means for combining the inverted out-of-band component signal with a second signal from the second transmitter to generate a filtered second signal; and means for wirelessly transmitting the filtered second signal from the second transmitter concurrently with the wireless transmission of the first signal by the first transmitter, wherein the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter is synchronized with the wireless transmission of the first signal by the first transmitter.

[0068] Another example system is provided for any of the aforementioned systems, wherein the means for transmission includes: means for modulating the first signal into a modulated format at the first transmitter; and means for receiving the first signal from the first transmitter in a modulated format at the second transmitter.

[0069] Another example system is provided for any of the aforementioned systems, wherein the means for transmission includes: means for receiving the first signal as a symbol sequence from the first transmitter in an unmodulated format at the second transmitter; and means for modulating the symbol sequence into the first signal in a modulated format at the second transmitter in response to receiving the first signal.

[0070] Another example system of any of the foregoing systems further includes: means for transmitting a synchronization signal between the first transmitter and the second transmitter via the one or more wired connections, the synchronization signal indicating timing information for synchronizing the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter with the wireless transmission of the first signal by the first transmitter.

[0071] Another example system is provided for any of the aforementioned systems, wherein the out-of-band portion of the modulated first signal includes energy beyond the channel bandwidth of the second transmitter.

[0072] Another example system is provided for any of the aforementioned systems, wherein the out-of-band portion of the modulated first signal includes energy beyond the channel bandwidth of the first transmitter.

[0073] Another example system of any of the foregoing systems further includes: means for adjusting the amplitude of the inverted out-of-band component signal to be highly correlated with the amplitude of the out-of-band radio frequency transmission received from the first transmitter in the wireless transmission of the first signal.

[0074] Therefore, specific embodiments of this subject matter have been described. Other embodiments are within the scope of the following claims. In some cases, the actions described in the claims can be performed in a different order and still achieve the desired result. Furthermore, the processes described in the drawings do not necessarily require the specific order or sequence shown to obtain the desired result. In some implementations, multitasking and parallel processing may be advantageous.

[0075] Several implementations of the described technology have been described. However, it should be understood that various modifications may be made without departing from the spirit and scope of the cited claims.

Claims

1. A method for filtering out out-of-band radio frequency emissions generated by a first transmitter's wireless transmission of a first signal from a second transmitter's wireless transmission, the method comprising: The out-of-band portion of the modulated first signal is inverted to generate an inverted out-of-band component signal. The inverted out-of-band component signal is combined with the second signal from the second transmitter to generate a filtered second signal; as well as The filtered second signal is wirelessly transmitted from the second transmitter concurrently with the first transmitter's wireless transmission of the first signal, wherein the wireless transmission of the out-of-band component signal of the filtered second signal by the second transmitter is synchronized with the wireless transmission of the first signal by the first transmitter.

2. The method as described in claim 1, characterized in that, Further includes: Before the phase inversion, the first signal is received at the second transmitter in a modulated format.

3. The method as described in claim 1, characterized in that, Further includes: The first signal is received as a symbol sequence at the second transmitter in an unmodulated format. as well as In response to receiving the first signal, before the inversion, the symbol sequence is modulated into the first signal in a modulated format at the second transmitter.

4. The method as described in claim 1, characterized in that, Further includes: A synchronization signal is transmitted between the first transmitter and the second transmitter via one or more wired connections. The synchronization signal indicates timing information for synchronizing the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter with the wireless transmission of the first signal by the first transmitter.

5. The method as described in claim 1, characterized in that, The out-of-band portion of the first signal in the modulated format includes energy outside the channel bandwidth of the second transmitter.

6. The method as described in claim 1, characterized in that, The out-of-band portion of the first signal in the modulated format includes energy outside the channel bandwidth of the first transmitter.

7. The method as described in claim 1, characterized in that, Further includes: The amplitude of the inverted out-of-band component signal is adjusted to be highly correlated with the amplitude of the out-of-band radio frequency transmission received from the first transmitter in the wireless transmission of the first signal.

8. A system for filtering out out-of-band radio frequency emissions, the system comprising: First transmitter; Second transmitter; A signal inverter configured to invert the out-of-band portion of a modulated first signal to generate an inverted out-of-band component signal; A signal combiner configured to combine the inverted out-of-band component signal with a second signal from the second transmitter to generate a filtered second signal; as well as A transmitter synchronizer is configured to wirelessly transmit the filtered second signal by the second transmitter concurrently with the wireless transmission of the first signal by the first transmitter, wherein the wireless transmission of the out-of-band component signal of the filtered second signal by the second transmitter is synchronized with the wireless transmission of the first signal by the first transmitter.

9. The system as described in claim 8, characterized in that, The second transmitter is configured to receive the first signal in the modulated format before the modulated first signal is inverted, and the second transmitter is configured to receive the first signal in the modulated format at the second transmitter.

10. The system as described in claim 8, characterized in that, The second transmitter is configured to receive the first signal as a symbol sequence in an unmodulated format before the modulated first signal is inverted, and to modulate the symbol sequence into the modulated first signal.

11. The system as described in claim 8, characterized in that, The system further includes one or more wired connections configured to transmit a synchronization signal between the first transmitter and the second transmitter. The synchronization signal indicates timing information for synchronizing the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter with the wireless transmission of the first signal by the first transmitter.

12. The system as described in claim 8, characterized in that, The out-of-band portion of the first signal in the modulated format includes energy outside the channel bandwidth of the second transmitter.

13. The system as described in claim 8, characterized in that, The out-of-band portion of the first signal in the modulated format includes energy outside the channel bandwidth of the first transmitter.

14. The system as described in claim 8, characterized in that, Further includes: An amplitude matcher is configured to adjust the amplitude of the inverted out-of-band component signal to be highly correlated with the amplitude of the out-of-band radio frequency transmission received from the first transmitter in the wireless transmission of the first signal.

15. A tangible processor-readable storage medium comprising one or more processor-executable instructions for execution on an electronic communication device to provide a process for filtering out out-of-band radio frequency emissions generated by a wireless transmission of a first signal by a second transmitter from a wireless transmission of a second transmitter, the process comprising: The out-of-band portion of the modulated first signal is inverted to generate an inverted out-of-band component signal. The inverted out-of-band component signal is combined with the second signal from the second transmitter to generate a filtered second signal; as well as The filtered second signal is wirelessly transmitted from the second transmitter concurrently with the first transmitter's wireless transmission of the first signal, wherein the wireless transmission of the out-of-band component signal of the filtered second signal by the second transmitter is synchronized with the wireless transmission of the first signal by the first transmitter.

16. The one or more tangible processor-readable storage media as claimed in claim 15, characterized in that, The process further includes: Before the phase inversion, the first signal is received at the second transmitter in a modulated format.

17. One or more tangible processor-readable storage media as claimed in claim 15, characterized in that, The process further includes: The first signal is received as a symbol sequence at the second transmitter in an unmodulated format; and In response to receiving the first signal, before the inversion, the symbol sequence is modulated into the first signal in a modulated format at the second transmitter.

18. The one or more tangible processor-readable storage media as claimed in claim 15, characterized in that, The process further includes: A synchronization signal is transmitted between the first transmitter and the second transmitter via one or more wired connections. The synchronization signal indicates timing information for synchronizing the wireless transmission of the inverted out-of-band component signal in the filtered second signal by the second transmitter with the wireless transmission of the first signal by the first transmitter.

19. One or more tangible processor-readable storage media as claimed in claim 15, characterized in that, The out-of-band portion of the first signal in the modulated format includes energy outside the channel bandwidth of the second transmitter.

20. One or more tangible processor-readable storage media as claimed in claim 15, characterized in that, The process further includes: The amplitude of the inverted out-of-band component signal is adjusted to be highly correlated with the amplitude of the out-of-band radio frequency transmission received from the first transmitter in the wireless transmission of the first signal.

Images