Patent Description:
<CIT> describes a system using multiple communication technologies for concurrent transmission is disclosed. The system includes a first technology modem, a second technology modem, and a transmit chain. The first technology modem is configured to provide a first technology signal for transmission using a first communication technology. The second technology modem is configured to provide a second technology signal for transmission using a second communication technology. The second communication technology is varied from the first communication technology. The transmit chain is configured to develop a combined envelope and to generate a transmit signal from the first technology signal and the second technology signal using the combined envelope.

<CIT> describes embodiments provide WiFi and WiMAX tailored transceiver radio frequency (RF) filtering techniques and configurations to enable coexistence between WiFi and WiMAX transceivers operating in close proximity. In particular, embodiments provide filtering techniques to reject emissions from WiMAX into WiFi, and vice versa. The filtering techniques eliminate the need for additional isolation between WiMAX and WiFi antennas (approximately <NUM> dB), which is beyond what is achievable in practice. Embodiments can be tailored according to different use cases of the WiFi and WiMAX transceivers (e.g., fixed CPE, portable router, smart phone with tethering).

<CIT> describes a method and apparatus that mitigates self-interference among various receivers and transmitters in a multifunction radio includes a transmitter operating in a first frequency band and a receiver operating in a second frequency band, different from the first frequency band. Jamming factors for multiple frequency channels in the first frequency band are calculated based on possible interference with the second frequency band by artifacts of the respective frequency channels. The frequency channel having the smallest jamming factor is selected as the frequency to be used by the transmitter.

The described technology filters out-of-band radio frequency emissions generated by wireless transmission of a first signal by a first transmitter from a wireless transmission of a second transmitter. The first signal is communicated from the first transmitter to the second transmitter via one or more wired connections. An out-of-band portion of a modulated format of the 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 of the second transmitter to create a filtering second signal. The filtering second signal is wirelessly transmitted from the second transmitter concurrently with wireless transmission of the first signal by the first transmitter, wherein the wireless transmission of the inverted out-of-band component signal in the filtering second signal by the second transmitter is synchronized with the wireless transmission of the first signal by the first transmitter.

This summary is provided to introduce a selection of concepts in a simplified form that is further described below in the Detailed Description.

Out-of-band radio frequency emissions can then couple with signals in a nearby Wi-Fi transmitter (a "victim" transmitter), for example, as noise. Unintentionally, the power amplifier of the Wi-Fi transmitter can then amplify the noise as it transmits its own Wi-Fi signals, which may be centered at <NUM> or <NUM>, for example. This combination results in amplified out-of-band RF emissions from the victim transmitter. As such, out-of-band radio frequency emissions can degrade the performance of the Wi-Fi transmitter by introducing and amplifying noise to the Wi-Fi transmission. Hardware bandpass filters may be used in attempts to mitigate the negative effects of such out-of-band radio frequency emissions, but such hardware filters are costly, less effective if the antennas are using close frequencies, and ineffective at filtering out-of-band radio frequency emission noise coupling within an RF power amplifier (power amp) of a victim transmitter. An RF power amplifier is a type of electronic amplifier that converts a low-power radio-frequency signal into a higher power signal to drive the antenna of a transmitter. The described technology can be implemented in hardware, software, or a combination of hardware and software to filter out-of-band radio frequency emissions without reliance on such hardware bandpass filters.

Example Bluetooth and Wi-Fi wireless technologies are used as example wireless communications technologies herein, but it should be understood that the described technology may be employed for other wireless communication technologies, including without limitation varieties of mobile telephone standards (e.g., LTE, <NUM>). In one implementation, Bluetooth wireless technology exchanges data over short distances using short-wave UHF RF waves from <NUM> to <NUM>, and Wi-Fi wireless technology exchanges data using radio frequency ranges including the <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> bands. When the channel bandwidths used by proximate wireless transmitters are close, out-of-band radio frequency emissions from an "aggressor" wireless transmitter can "leak out" of the aggressor wireless transmitter and couple with a transmission signal of a "victim" wireless transmitter, resulting in out-of-band radio frequency emissions from the victim wireless transmitter. In some circumstances, such coupling may occur within the power amplifier of the victim wireless transmitter, causing the out-of-band radio frequency emissions to be amplified in the wireless transmissions of the victim wireless transmitter.

<FIG> illustrates an example communication device <NUM> including a first transmitter <NUM> and a second transmitter <NUM>. The transmitters are positioned in proximity to one another in the bezel of the communication device <NUM>. The two transmitters have different channel bandwidths. In one example, the first transmitter <NUM> is a Bluetooth transmitter with a channel bandwidth in the <NUM> to <NUM> range, and the second transmitter <NUM> is a Wi-Fi transmitter with a channel bandwidth centered at <NUM> or <NUM>.

As shown by the radiating dashed-line circles emanating from the first transmitter <NUM>, a first radio frequency (RF) signal <NUM> can radiate from the first transmitter <NUM>, reaching the second transmitter <NUM>. Generally, the channel bandwidths of the first transmitter <NUM> and the second transmitter <NUM> do not overlap or are otherwise protected from in-band noise emanating from other transmitters. However, some transmitters leak out-of-band radio frequency emissions (e.g., <NUM>nd and/or <NUM>rd harmonics) that can reach another nearby transmitter. In this sense, "out-of-band" refers to emitted RF energy that is outside the channel bandwidth of the transmitter (e.g., energy emitted by a Bluetooth transmitter outside of the <NUM> to <NUM> range, energy emitted by a Wi-Fi transmitter outside of the <NUM> or <NUM> channels).

A transmitter that leaks out-of-band radio frequency emissions that couple into another transmitter is referred to herein as an "aggressor" transmitter. A transmitter that experiences such coupling of the out-of-band radio frequency emissions of an aggressor transmitter is referred to herein as a "victim" transmitter. The out-of-band radio frequency emissions of the aggressor transmitter can electromagnetically couple to components (e.g., a power amplifier) of the transmitter to introduce noise into transmissions of the victim transmitter. In the case where the component is a power amplifier, for example, the out-of-band noise can actually be amplified in the wireless transmission of the victim transmitter.

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 the communication device <NUM>. RF transmission energy <NUM> of the second transmitter <NUM> is shown in <FIG>.

<FIG> illustrates an example system <NUM> for filtering out-of-band radio frequency emissions <NUM> generated by wireless transmission of an RF signal by an aggressor transmitter <NUM> from a wireless transmission of a victim transmitter <NUM>. Generally, the channel bandwidths of the aggressor transmitter <NUM> and the victim transmitter <NUM> do not overlap or are otherwise protected from in-band noise emanating from other transmitters (e.g., hardware filters). However, some transmitters leak out-of-band radio frequency emissions (e.g., <NUM>nd and/or <NUM>rd harmonics) that can reach another nearby transmitter. In this sense, "out-of-band" refers to emitted RF energy that is outside the channel bandwidth of the transmitter (e.g., energy emitted by a Bluetooth transmitter outside of the <NUM> to <NUM> range, energy emitted by a Wi-Fi transmitter outside of the <NUM> or <NUM> channels).

The example scenario presented in <FIG> depicts an aggressor transmitter <NUM> (e.g., a Bluetooth transmitter) that is leaking out-of-band radio frequency emissions <NUM> (i.e., RF energy) that are coupling with components of the victim transmitter <NUM>. The aggressor transmitter <NUM> and the victim transmitter <NUM> are connected by one or more wired connections within a communication device. For example, the synchronization signal <NUM> and the aggressor signal <NUM> are communicated between the aggressor transmitter <NUM> and the victim transmitter <NUM> via one or more wired connections.

The victim transmitter <NUM> includes a power amp <NUM> (power amplifier) that amplifies a low-power RF signal for transmission via an antenna <NUM>. When transmitting, the victim transmitter <NUM> and antenna <NUM> generally emit in-band RF energy within a channel bandwidth of the victim transmitter <NUM> (e.g., within a Wi-Fi frequency range). When transmitting, the aggressor transmitter <NUM> and its corresponding antenna <NUM> generally emit in-band RF energy within a channel bandwidth of the aggressor transmitter <NUM> (e.g., within a Bluetooth frequency range). However, in some scenarios, the aggressor transmitter <NUM> can also emit out-of-band RF energy (referred to as out-of-band radio frequency emissions <NUM> or out-of-band RF emissions) while transmitting. Such out-of-band radio frequency emissions <NUM> can couple to the circuitry in the victim transmitter <NUM> and be introduced as noise in the wireless transmissions of the victim transmitter <NUM>.

In various implementations, the system <NUM> can cancel out or decrease such noise in the wireless transmissions of the victim transmitter <NUM>. Before wirelessly transmitting a signal (e.g., the aggressor signal <NUM>), the aggressor transmitter <NUM> first sends the aggressor signal <NUM> to the victim transmitter <NUM> via one or more wired connections. The victim transmitter <NUM> combines aspects of the aggressor signal <NUM> with its own transmission signal to filter or cancel out the out-of-band RF emissions from its wireless transmission.

There are various implementations for allocating signal processing operations between the aggressor transmitter <NUM> and the victim transmitter <NUM>. In one implementation, the aggressor signal <NUM> receives (e.g., via a wired connection) a sequence of symbols in an unmodulated format. The victim transmitter <NUM> receives the aggressor signal <NUM> in the unmodulated format. A signal modulator <NUM>, which can include hardware and software, modulates an out-of-band portion of the aggressor signal <NUM> into a modulated format of the victim transmitter (e.g., Wi-Fi format) signal. A signal inverter <NUM>, which can include hardware and software, inverts the modulated out-of-band portion of the aggressor signal <NUM>. A signal combiner <NUM>, which can include hardware and/or software, combines the modulated, inverted out-of-band portion of the aggressor signal <NUM> to the victim transmitter's own transmission signal to create a filtering second signal, which cancels out the effects of the out-of-band RF emissions <NUM> from its own transmission. In other implementations, the victim transmitter <NUM> modulates its own signal and the inverted symbols from the aggressor transmitter <NUM> together, without the need for a separate hardware signal combiner <NUM>. Instead, the signal combiner <NUM> may be part of a modulator in the victim transmitter <NUM>. Other implementations are also contemplated.

As discussed below, the transmission timing of the modulated, inverted out-of-band portion of the aggressor signal <NUM> is synchronized with the wireless transmission of the aggressor signal by the aggressor transmitter <NUM> to satisfy a synchronization timing condition. In one example, if the transmission timings are synchronized enough to match or be highly-correlated, they satisfy a synchronization timing condition, although other synchronization timing conditions may be defined. Such conditions may be determined based on their effectiveness in canceling or reducing aggressor-transmitter-induced out-of-band noise in the victim transmitter's wireless transmission (e.g., an out-of-band noise condition).

In addition, the modulated, inverted out-of-band portion of the aggressor signal <NUM> combined into the victim transmitter's wireless transmission signal is amplitude-matched (or highly correlated) with the out-of-band RF emissions <NUM> received by the victim transmitter <NUM> to satisfy an amplitude-match condition. In one example, if the amplitudes are sufficiently matched or highly-correlated, they satisfy an amplitude-match condition, although other amplitude-match conditions may be defined. Such conditions may be determined based on their effectiveness in canceling or reducing aggressor-transmitter-induced out-of-band noise in the victim transmitter's wireless transmission (e.g., an out-of-band noise condition).

In combination, satisfaction of the synchronization timing condition and/or the amplitude-matched condition results in a level of out-of-band noise in the victim transmitter's wireless transmission signal that satisfies an overall out-of-band noise condition (e.g., the level of out-of-band noise is below a designated threshold). In this manner, noise resulting from the coupling of an aggressor transmitter's out-of-band RF emissions into a victim transmitter's transmission signal can be cancelled out or diminished without the need for additional hardware bandpass filters.

In another implementation, much of the signal processing of the aggressor signal <NUM> can be performed by the aggressor transmitter <NUM>. In this implementation, the aggressor signal <NUM> is modulated by a signal modulator <NUM>, which can include hardware and software, in the aggressor transmitter <NUM>. The signal modulator <NUM> modulates an out-of-band portion of the aggressor signal <NUM> in the modulation format of the victim transmitter <NUM>. In addition, a signal inverter <NUM> in the aggressor transmitter <NUM> inverts the modulated out-of-band portion of the aggressor signal <NUM> before the aggressor transmitter <NUM> sends the aggressor signal <NUM> to the victim transmitter <NUM> in a modulated format of the victim transmitter <NUM>. This implementation can also cancel out or diminish noise resulting from the coupling of an aggressor transmitter's out-of-band RF emissions from a victim transmitter's transmission signal without the need for additional hardware bandpass filters.

In other implementations, the modulation and inverting operations may be allocated in various combinations between the aggressor transmitter <NUM> and the victim transmitter <NUM>. These implementations can also cancel out or diminish noise resulting from the coupling of an aggressor transmitter's out-of-band RF emissions from a victim transmitter's transmission signal without the need for additional hardware bandpass filters.

As previously discussed, the magnitude of the inverted out-of-band component signal in the filtering second signal is adapted to match or highly correlate the amplitude of the out-of-band RF emissions actually coupling into the victim transmitter <NUM>. In one implementation, an amplitude matcher <NUM> can monitor the received out-of-band RF emissions <NUM> actually received by the victim transmitter <NUM> from the aggressor transmitter <NUM>, estimate the power density of the received out-of-band RF emissions <NUM>, and adjust the amplitude of the modulated, inverted out-of-band portion of the aggressor signal <NUM> that is combined with the victim transmitter's own transmission signal to match or highly correlate the amplitude of the received out-of-band RF emissions <NUM>.

As previously discussed, the timing of the wireless transmission by the aggressor transmitter <NUM> and the victim transmitter <NUM> are synchronized so that the aggressor signal is transmitted by the aggressor transmitter <NUM> at the same time as the inverted out-of-band portion of the aggressor signal <NUM> by the victim transmitter <NUM>. Accordingly, a transmitter synchronizer <NUM>, which can include hardware and software, generates the synchronization signal <NUM> to synchronize the wireless transmission of the inverted out-of-band component signal in the filtering second signal by the victim transmitter with the wireless transmission of the aggressor signal by the aggressor transmitter. The transmitter synchronizer <NUM> communicates the synchronization signal <NUM> to the transmitter synchronizer <NUM> of the aggressor transmitter <NUM> to match or highly correlate the timing of the respective wireless transmissions.

The timing error between the aggressor signal and the filtering second signal can be reduced or eliminated in one implementation by shifting the modulated signal timing of the victim transmitter <NUM> until the out-of-band power density satisfies a power density condition (e.g., is below a programmable threshold). Once the proper timing is determined, the victim transmitter <NUM> can, if needed, ask the aggressor transmitter <NUM> to send its symbols in the proper timing. The better matched the synchronization is between the aggressor signal and the inverted out-of-band portion of the aggressor signal, the better the noise is cancelled or diminished from the victim transmitter <NUM>.

In another implementation, the victim transmitter <NUM> can receive time synchronization information corresponding to out-of-band symbol timing and sent by the aggressor transmitter <NUM>. The victim transmitter <NUM> can then use the time synchronization information for clock-based synchronization between the two transmitters to synchronize the transmission of the filtering second signal by the victim transmitter <NUM> with the transmission of the corresponding symbols by the aggressor transmitter <NUM>.

In one implementation, the synchronization signal <NUM> may include a shift delay indicating a time period or number of clock cycles that the aggressor transmitter <NUM> is to delay wireless transmission of the aggressor signal so that the out-of-band radio frequency emissions <NUM> synchronize with the wireless transmission of the inverted out-of-band component signal in the filtering victim signal. In one implementation, the synchronization may be implemented using an adaptive filter to adjust the synchronization signal <NUM> based on a power density measurement or estimation of the out-of-band energy in the wireless transmission by the victim transmitter <NUM>, although other synchronization methods may also be employed. These varying implementations allow for variations in transmitter design, such that either or both transmitters can be responsible for the synchronization of the filtering victim signal with the aggressor signal's out-of-band RF emissions <NUM>.

<FIG> illustrates example operations <NUM> for filtering out-of-band radio frequency emissions. A communicating operation <NUM> communicates a first signal (e.g., the aggressor signal) from the first transmitter to the second transmitter via one or more wired connections. The communicated aggressor signal may be a sequence of symbols to be transmitted by the first transmitter or some signal processed version of those symbols (e.g., inverted and/or modulated in the modulation format of the second transmitter). If the first signal is not modulated into the modulation format of the second transmitter by a signal modulator of the first transmitter, then a signal modulator of the second transmitter will perform the modulation on an out-of-band portion of the aggressor signal.

An inversion operation <NUM> inverts an out-of-band portion of the first signal to generate an inverted out-of-band component signal. Generally, inversion may be performed by either transmitter. Examples include using a <NUM>-degree phase-shifted version of the signal and applying an inverter to the modulated signal without a phase change. In one implementation, the inversion operation <NUM> may be performed by a signal inverter in the first transmitter. If the out-of-band portion of the first signal is not inverted (e.g., by a signal inverter) of the first transmitter, then a signal inverter of the second transmitter will perform the inversion. In another implementation, inversion, e.g., in the form of a <NUM>-degree phase change applied to each symbol, may be performed prior to the modulation by either transmitter.

A combining operation <NUM> combines the inverted out-of-band component signal with a second signal of the second transmitter to create a filtering signal. A synchronized transmission operation <NUM> wirelessly transmits the filtering second signal from the second transmitter concurrently with wireless transmission of the first signal by the first transmitter. The concurrent wireless transmissions are performed such that the wireless transmission of the inverted out-of-band component signal in the filtering second signal by the second transmitter is synchronized with the wireless transmission of the first signal by the first transmitter.

In another implementation, the aggressor transmitter sends information about the frequency profile of its signal, such as frequency band or a sub-carrier frequency at which the out-of-band emissions are to be found. In one implementation, the aggressor transmitter sends information about the frequency of the second harmonic of its signal to the victim transmitter, which uses this information to place the inverted symbols at the proper sub-carrier frequencies.

In one implementation, an adjusting 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 highly correlates the amplitude of out-of-band radio frequency emissions received from the wireless transmission of the first signal by the first transmitter. 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 amplitudes are matched, the better the noise is cancelled or diminished from the victim transmitter.

<FIG> illustrates various signal components <NUM> relating to filtering out-of-band radio frequency emissions. A first graph, entitled "transmitting information as digital signal," depicts a digital signal (the aggressor signal) represented as a sequence of symbols. A second graph, entitled "serial symbol for M-array QAM modulation at transmitter," depicts the sequence of symbols corresponding to the digital signal in the first figure.

A third graph, entitled "waveform for M-array QAM modulation according to symbolic information," depicts an out-of-band portion of the aggressor signal in the modulated format of a victim transmitter. A fourth graph, entitled "waveform for M-array QAM modulation according to inverted symbolic information," depicts an inverted version of the out-of-band portion of the aggressor signal in the modulated format of a victim transmitter. A fifth graph, entitled "OOB Cancellation Using Inverse Modulation Techniques," depicts a result of the transmission of the aggressor signal by the aggressor transmitter synchronized with transmission of the inverted version of the out-of-band portion of the aggressor signal in the modulated format of a victim transmitter. As shown in the fifth graph, the out-of-band (OOB) energy is canceled out. A sixth graph, entitled "OOB Cancellation Using ½ symbol shifted Inverse Modulate Techniques," depicts non-zero OOB energy resulting from a lack of synchronization between transmission of the aggressor signal by the aggressor transmitter and transmission of the inverted version of the out-of-band portion of the aggressor signal in the modulated format of a victim transmitter.

<FIG> illustrates an example communication device <NUM> for implementing the features and operations of the described technology. The communication device <NUM> may be a client device, such as a laptop, mobile device, desktop, tablet; a server/cloud device; an internet-of-things device; an electronic accessory; or another electronic device. The communication device <NUM> includes one or more processor(s) <NUM> and a memory <NUM>. The memory <NUM> generally includes both volatile memory (e.g., RAM) and nonvolatile memory (e.g., flash memory). An operating system <NUM> resides in the memory <NUM> and is executed by the processor(s) <NUM>.

In an example communication device <NUM>, as shown in <FIG>, one or more modules or segments, such as communication software <NUM>, application modules, transmitter synchronizers, amplitude matchers, signal combiners, signal inverters, signal modulators, and other modules, are loaded into the operating system <NUM> on the memory <NUM> and/or storage <NUM> and executed by processor(s) <NUM>. The storage <NUM> may store communication parameters, signal data, and other data and be local to the communication device <NUM> or may be remote and communicatively connected to the communication device <NUM>.

The communication device <NUM> includes a power supply <NUM>, which is powered by one or more batteries or other power sources and which provides power to other components of the communication device <NUM>. The power supply <NUM> may also be connected to an external power source that overrides or recharges the built-in batteries or other power sources.

The communication device <NUM> may include one or more communication transceivers <NUM> which may be connected to one or more antenna(s) <NUM> to provide network connectivity (e.g., mobile phone network, Wi-Fi®, Bluetooth®) to one or more other servers and/or client devices (e.g., mobile devices, desktop computers, or laptop computers). The communication device <NUM> may further include a network adapter <NUM>, which is a type of communication device. The communication device <NUM> may use the adapter and any other types of communication devices for establishing connections over a wide-area network (WAN) or local-area network (LAN). It should be appreciated that the network connections shown are exemplary and that other communication devices and means for establishing a communications link between the communication device <NUM> and other devices may be used.

The communication device <NUM> may include one or more input devices <NUM> such that a user may enter commands and information (e.g., a keyboard or mouse). These and other input devices may be coupled to the server by one or more interfaces <NUM>, such as a serial port interface, parallel port, or universal serial bus (USB). The communication device <NUM> may further include a display <NUM>, such as a touch screen display.

The communication device <NUM> may include a variety of tangible processor-readable storage media and intangible processor-readable communication signals. Tangible processor-readable storage can be embodied by any available media that can be accessed by the communication device <NUM> and includes both volatile and nonvolatile storage media, removable and non-removable storage media. Tangible processor-readable storage media excludes communications signals and includes volatile and nonvolatile, removable and non-removable storage media implemented in any method or technology for storage of information such as processor-readable instructions, data structures, program modules or other data. Tangible processor-readable storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CDROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other tangible medium which can be used to store the desired information and which can be accessed by the communication device <NUM>. In contrast to tangible processor-readable storage media, intangible processor-readable communication signals may embody processor-readable instructions, data structures, program modules or other data resident in a modulated data signal, such as a carrier wave or other signal transport mechanism. By way of example, and not limitation, intangible communication signals include signals traveling through wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared, and other wireless media.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular embodiments of a particular described technology.

Thus, particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. In certain implementations, multitasking and parallel processing may be advantageous.

Claim 1:
A method (<NUM>) of filtering out-of-band radio frequency emissions (<NUM>) generated by wireless transmission of a first signal (<NUM>) by a first transmitter (<NUM>) from a wireless transmission of a second transmitter (<NUM>), the method (<NUM>) comprising:
communicating (<NUM>) the first signal (<NUM>) from the first transmitter (<NUM>) to the second transmitter (<NUM>) via one or more wired connections (<NUM>, <NUM>);
inverting (<NUM>) an out-of-band portion of a modulated format of the first signal (<NUM>) to generate an inverted out-of-band component signal;
combining (<NUM>) the inverted out-of-band component signal with a second signal of the second transmitter to create a filtering second signal; and
wirelessly transmitting (<NUM>) the filtering second signal from the second transmitter (<NUM>) concurrently with wireless transmission of the first signal (<NUM>) by the first transmitter (<NUM>), wherein the wireless transmission of the inverted out-of-band component signal in the filtering second signal by the second transmitter (<NUM>) is synchronized with the wireless transmission of the first signal (<NUM>) by the first transmitter (<NUM>).