Patent Description:
In modern cellular devices, high transmitter linearity helps avoid interference between nearby devices. Specific levels of transmitter linearity may be required by certain standards or governing bodies. For example, the 3rd Generation Partnership Project (3GPP) imposes stringent counter-intermodulation (CIM) requirements. Some types of transmitters may meet new CIM requirements better than other types. For example, such CIM requirements may be met with, e.g., a multi-phase transmitter design. A multi-phase transmitter is sometimes referred to as "N-phase" transmitter, where N is an integer number. Such transmitters implement N transmission paths to generate an up-converted output signal. A <NUM>-Phase transmitter is sometimes referred to as a differential quadrature transmitter, but higher-level phased transmitters, such as <NUM>-Phase transmitters, may also be used.

Document <CIT> relates to an apparatus and method for improving the efficiency of a power amplifier operating on the basis of a signal of a large peak-to-average power ratio (PAR). According to this document, a main amplification part detects envelope values of an input baseband signal, reduces a peak value of the envelope values of the baseband signal to generate a peak reduced signal, amplifies the generated peak reduced signal, and outputs a first amplified signal. An error correction amplification part amplifies an error signal indicating a difference between the baseband signal and the peak reduced signal, and outputs a second amplified signal. A summing part combines the first amplified signal from the main amplification part and the second amplified signal from the error correction amplification part, such that high amplification efficiency is produced and an amplified output signal with reduced spectral regrowth in which an error is corrected can be outputted.

The present invention relates to a device and is set out by the set of appended claims.

The present invention is set out by the set of appended claims. In the following, parts of the description and drawing referring to examples or implementations, which are not covered by the claims are not presented as embodiments of the invention, but as illustrative examples useful for understanding the invention. The embodiments of the invention are determined by the appended claims.

The figures are drawn to clearly illustrate the relevant aspects of the examples and are not necessarily drawn to scale.

The making and using of examples of this disclosure are discussed in detail below. It should be appreciated, however, that the concepts disclosed herein can be embodied in a wide variety of specific contexts, and that the specific examples discussed herein are merely illustrative and do not serve to limit the scope of the claims.

<FIG> is a diagram of a network <NUM> for communicating data. The network <NUM> comprises a base station <NUM> having a coverage area <NUM>, a plurality of mobile devices <NUM>, and a backhaul network <NUM>. As shown, the base station <NUM> establishes uplink (dashed line) and/or downlink (dotted line) connections with the mobile devices <NUM>, which serve to carry data from the mobile devices <NUM> to the base station <NUM> and vice-versa. Data carried over the uplink/downlink connections may include data communicated between the mobile devices <NUM>, as well as data communicated to/from a remote-end (not shown) by way of the backhaul network <NUM>. As used herein, the term "base station" refers to any component (or collection of components) configured to provide wireless access to a network, such as an enhanced base station (eNB), a macro-cell, a femtocell, a Wi-Fi access point (AP), or other wirelessly enabled devices. Base stations may provide wireless access in accordance with one or more wireless communication protocols, e.g., long term evolution (LTE), LTE advanced (LTE-A), High Speed Packet Access (HSPA), Wi-Fi <NUM>. 11a/b/g/n/ac, etc. As used herein, the term "mobile device" refers to any component (or collection of components) capable of establishing a wireless connection with a base station, such as a user equipment (UE), a mobile station (STA), and other wirelessly enabled devices. In some examples, the network <NUM> may comprise various other wireless devices, such as relays, low power nodes, etc..

According to some examples, one or more of the mobile devices <NUM> use a hybrid transmitter for performing transmissions. A hybrid transmitter may be a multi-phase transmitter structure that operates in multiple ("hybrid") modes. The hybrid transmitter may be controlled to operate as an <NUM>-Phase transmitter or a <NUM>-Phase transmitter. When operating as an <NUM>-Phase transmitter, the hybrid transmitter consumes more power but may also achieve high linearity performance. When operating as a <NUM>-Phase transmitter, the hybrid transmitter consumes less power. <NUM>-Phase operation may be performed in situations where linearity requirements are relaxed, and <NUM>-Phase operation may be performed in situations where high linearity is needed. Linearity requirements for a transmission may be determined according to the resource block (RB) and/or channel configuration for the transmission. By reducing power consumption when linearity requirements are relaxed, the average power consumption of the transmitter may be reduced while still satisfying CIM requirements. By reducing power consumption, the battery life of the mobile device <NUM> may be increased.

<FIG> is a block diagram of portions of a mobile device <NUM>, in accordance with some examples. The illustrated portions of the mobile device <NUM> include a baseband integrated circuit (IC) <NUM>, a transmitter <NUM>, one or more amplifiers <NUM>, one or more filters <NUM>, one or more antennas <NUM>, and a power controller <NUM>. The baseband IC <NUM> includes processors, memories, and the like, which may be executing firmware or software. For example, the baseband IC <NUM> may include general-purpose processors, field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), or the like. In an example, the baseband IC <NUM> comprises a baseband processor that generates outgoing signals for transmission and communicates the outgoing signals to the transmitter <NUM> using one or more signals <NUM>. The signals <NUM> may include control signals and the outgoing signals, and are inputted to the transmitter <NUM> as baseband signals. The outgoing signals inputted to the transmitter <NUM> are represented by quadrature signals that include an in-phase portion (I) and a quadrature portion (Q).

The transmitter <NUM> generates an output signal for transmission according to the outgoing baseband signal. The transmitter <NUM> also includes front-end output circuitry, such as summers and a variable gain amplifier (VGA), for producing an upconverted radio frequency (RF) signal. The output signal is then amplified by the amplifiers <NUM>. The amplifiers <NUM> may include a power amplifier (PA) or the like, and may be part of the transmitter <NUM> or may be separate from the transmitter <NUM>. In an example, the amplifiers <NUM> include a PA that is separate from the transmitter <NUM>. Once amplified, the filters <NUM> may optionally be used to remove noise from the output signal. Finally, the output signal is transmitted using the antennas <NUM>. During operation, the power controller <NUM> performs transmission power control for the transmitter <NUM> and amplifier <NUM>. Parameters for a transmission, such as the current frequency band, the target antenna power, and the current LTE RB configuration, are communicated to the power controller <NUM>, which performs transmission power control based on the communicated parameters. Although the power controller <NUM> is separately illustrate, it should be appreciated that, in some examples, the power controller <NUM> is part of the baseband integrated circuit (IC) <NUM>.

In accordance with some examples, the transmitter <NUM> is a hybrid transmitter that may be configured for <NUM>-Phase or <NUM>-Phase operation by the power controller <NUM> in conjunction with a mode selection circuit <NUM> (see <FIG>, discussed further below), according to control signals from the power controller <NUM>. In an example, the transmitter <NUM> is an <NUM>-Phase transmitter that may be configured to implement <NUM>-Phase operation. Particular features (or devices) of the <NUM>-Phase transmitter may be powered off such that the features (or devices) remaining powered on form a <NUM>-Phase transmitter. The operating mode of the transmitter <NUM> may be controlled based on several factors. In accordance with some examples, the power controller <NUM> receives parameters of a transmission, which may include the current frequency band, the target antenna power, and the current LTE RB configurations of a transmission that will be performed by the transmitter <NUM>. The power controller <NUM> determines whether the transmitter <NUM> should operate in <NUM>-Phase or <NUM>-Phase operation according to the transmission parameters. An example method for determining the mode of operation is described further below with respect to <FIG>. Once the mode is determined, the power controller <NUM> sends the control signals to the mode selection circuit <NUM>, which configures the transmitter <NUM> to operate in the selected mode.

The transmitter <NUM> may be controlled by the power controller <NUM> to comply with CIM requirements. CIM requirements may be imposed on the mobile devices <NUM> to limit spurious emissions to nearby mobile devices <NUM> operating at close frequencies. Spurious emission limits are often defined as an absolute level (e.g., in dBm). Spurious emissions may depend on the output power of the transmitter <NUM>. CIM requirements may vary based on the output power, such that higher output powers have higher CIM requirements. From the perspective of the transmitter <NUM>, achieving a target spurious emission level (e.g., in dBc) between the desired signal and unwanted spurious outputs is more difficult at high output power levels and easier at low output power levels. In other words, maintaining sufficiently low spurious emissions is easier at lower power levels. As such, in accordance with some examples, the operating mode of the transmitter <NUM> may be changed while performing transmitter automatic power control (TX APC) for the transmitter <NUM>, which may be performed by the power controller <NUM> during operation (e.g., on-the-fly) based on the target transmission power for the antenna <NUM>. In particular, a predetermined threshold is determined by the power controller <NUM> based on the transmission parameters, and is compared to current target transmission power for the antenna <NUM>. When the current target antenna power is higher than the predetermined threshold, <NUM>-Phase operation is enabled. When the current target antenna power is less than or equal to the predetermined threshold, <NUM>-Phase operation is enabled. A main cause of CIM distortion is mixing of fundamental signals with third or fifth harmonics of the signals. An <NUM>-Phase transmitter cancels the third and fifth harmonics, and a <NUM>-Phase transmitter does not. As such, <NUM>-Phase operation may provide better CIM performance, but may do so at the cost of higher power consumption.

The transmitter <NUM> may also be controlled by the power controller <NUM> according to the operating frequency used. CIM performance is frequency band dependent (depending on the protection needed for nearby frequency band), and so the mode of the transmitter <NUM> may be switched at predefined switching point thresholds. As such, in accordance with some examples, the predetermined threshold for the current target antenna power is frequency-band-dependent. Different predetermined thresholds may be used by the power controller <NUM> in different frequency bands.

The transmitter <NUM> may also be controlled by the power controller <NUM> according to the LTE resource block configuration used for transmissions. Typically more stringent CIM requirements are only applied to certain LTE RBs, such as RBs at edges of the frequency channel. RBs located at the edge of the frequency channel tend to be concentrated in a narrow bandwidth (e.g., have a higher energy density), and such RBs may cause greater CIM distortion than RBs that are more evenly spread across the frequency channel. For other cases, CIM requirements may be relaxed. Such cases include those where a full RB is used, or when a partial RB in the center of the channel is used. In such cases, <NUM>-Phase operation may be used while maintaining CIM compliance. RB configuration information is made available to transmitter <NUM> by, e.g., the baseband IC <NUM>, and may be used for mode selection to further optimize power consumption.

<FIG> is a system diagram of the transmitter <NUM>, in accordance with some examples. The transmitter <NUM> has a digital baseband portion <NUM> and an analog transceiver portion <NUM>. The digital baseband portion <NUM> is realized as software, firmware, an ASIC, or the like, and the analog transceiver portion <NUM> is realized as a circuit. The connections in the analog transceiver portion <NUM> are balanced pairs of signals. The transmitter <NUM> includes a plurality of quadrature modulators, which produce the output signal according to the I and Q components of the outgoing baseband signal. In particular, the transmitter <NUM> includes a first quadrature modulator and a second quadrature modulator. As further discussed below, the I and Q components may be digitally processed by a signal compensation and correction module <NUM> before they are modulated by the first and second quadrature modulators. The first and second quadrature modulators modulate the I and Q components with a carrier signal from a carrier clock generator <NUM>, which is also discussed further below. The resulting signals are then combined by an output circuit <NUM>. The output circuit <NUM> includes additional RF circuitry, such as summers for combining the signals from the first and second quadrature modulators to produce the output signal, and a VGA for amplifying the output signal. In some examples, the output circuit <NUM> is a VGA, where the output of the mixers 316A-316B and 322A-322B are directly connected to the VGA input. Because the output of the mixers 316A-316B and 322A-322B do not overlap, they may be directly connected without the need for a summer. The output of the VGA may be transmitted to the antenna <NUM>.

The first quadrature modulator includes digital-to-analog converters (DACs) 312A-312B, low-pass filters (LPFs) 314A-314B, and mixers 316A-316B. The DACs 312A-312B, respectively, receive the I and Q signals in digital form and each produce a corresponding balanced pair of signals. The LPFs 314A-314B remove noise from the balanced analog I and Q signals. The mixers 316A-316B multiply the analog I and Q signals with the carrier signal. The carrier signal provided to the mixers 316A-316B is a quadrature signal, such that the signal provided to the mixer 316A is <NUM>° out of phase with the signal provided to the mixer 316B. The resulting signals are then combined in the output circuit <NUM>.

The second quadrature modulator includes DACs 318A-318B, LPFs 320A-320B, and mixers 322A-322B. The DACs 318A-318B, respectively, receive modified I and Q signals in digital form and each produce a corresponding balanced pair of signals. The modified I signal is produced by determining the difference between the I and Q signals at a summer 324A, and multiplying the difference by a constant <NUM> at the mixer 328A. The modified Q signal is produced by determining the difference between the Q and I signals at a summer 324B, and multiplying the difference by the constant <NUM> at the mixer 328B. The constant <NUM> is a predetermined value that, when multiplied by the difference between the I and Q signals, allows the second quadrature modulator to output the same signal level as the first quadrature modulator. The constant <NUM> may be, e.g., <MAT>. The LPFs 320A-320B remove noise from the balanced analog modified I and Q signals. The mixers 322A-322B multiply the analog modified I and Q signals with the carrier signal. The carrier clock provided to the mixers 322A-322B is a quadrature signal, such that the signal provided to the mixer 322A is <NUM>° out of phase with the signal provided to the mixer 322B. The resulting signals are then combined in the output circuit <NUM>. Combining the differences between the I and Q signals (e.g., from the second quadrature modulator) with the I and Q signals (e.g., from the first quadrature modulator) results in cancellation of the third or fifth harmonics of the fundamental I and Q signals, reducing CIM distortion.

The carrier clock generator <NUM> provides clock signals for the first and second quadrature modulators, and may provide up to eight signals: two signals to each of the mixers 316A- 316B and 322A-322B. As such, the carrier clock generator <NUM> may be said to be operating in <NUM>-Phase mode when both the first and second quadrature modulators are active, and in <NUM>-Phase mode when only the first quadrature modulator is active. The carrier clock generator <NUM> includes a first portion that provides clock signals in <NUM>-Phase operation and a second portion that provides clock signals in <NUM>-Phase operation. Power consumption of the carrier clock generator <NUM> may be reduced when it operates in <NUM>-Phase mode.

During operation, a mode selection circuit <NUM> turns features of the transmitter <NUM> on and off to seamlessly switch between <NUM>-Phase and <NUM>-Phase operation. The mode selection circuit <NUM> changes modes of the transmitter <NUM> based on a control signal received from the baseband IC <NUM> (e.g., with the signals <NUM> via the power controller <NUM>). When the mode selection circuit <NUM> receives the control signal, it controls the digital baseband portion <NUM> and analog transceiver portion <NUM> accordingly. The mode selection circuit <NUM> may be a demultiplexer, a microcontroller, a series of logic gates, or the like, which turn features of the transmitter <NUM> on or off depending on the control signal. If the transmitter should operate in <NUM>-Phase mode, the functions of the digital baseband portion <NUM> are controlled to operate in <NUM>-Phase mode, all the modulators and associated circuits of the analog transceiver portion <NUM> are turned on, and the carrier clock generator <NUM> is controlled to produce <NUM>-Phase clock signals. If the transmitter should operate in <NUM>-Phase mode, the functions of the digital baseband portion <NUM> are controlled to operate in <NUM>-Phase mode, the second quadrature modulator and associated circuits of the analog transceiver portion <NUM> are turned off, and the carrier clock generator <NUM> is controlled to produce <NUM>-Phase clock signals.

The compensation and correction module <NUM> corrects the I and Q outgoing baseband signals before they are transmitted. Among other correction operations, the compensation and correction module <NUM> may perform phase compensation and impairment correction. Parameters of the phase compensation and impairment correction operations may be changed by the mode selection circuit <NUM> according to the operating mode of the transmitter <NUM>.

For impairment correction, <NUM>-Phase operation and <NUM>-Phase operation may call for different impairment correction values. Examples of impairment correction include image distortion correction, DC offset correction, correction of signal leakage from the carrier clock generator <NUM>, and the like. The correction values used may be selected according to the mode of operation. Different impairment correction values for <NUM>-Phase operation and <NUM>-Phase operation may be stored in the compensation and correction module <NUM>, and the appropriate impairment correction values may be selected based on the mode of operation. Image distortion correction may be implemented as two tap filters, where the impairment correction values are the tap filter coefficients. Image distortion correction may also be implemented as a multiplier with a delay adjustment, where the impairment correction values are the multiplier and delay values. The DC offset correction may be implemented through addition of a DC value, where an impairment correction value is the added DC value.

For phase compensation, transitioning between <NUM>-Phase and <NUM>-Phase operation may cause a phase shift from the carrier clock generator <NUM>. The carrier clock generator <NUM> circuit produces a constant phase shift between <NUM>-Phase and <NUM>-Phase operation. A constant phase shift may be added to the outgoing baseband signals to compensate for the phase shift introduced by the carrier clock generator <NUM>, as well as other phase shifts introduced by other circuit in the transmission path of the transmitter <NUM>. The phase shift compensation value used may be selected according to the mode of operation. Different phase compensation values for <NUM>-Phase operation and <NUM>-Phase operation may be stored in the compensation and correction module <NUM>, and the appropriate phase compensation values may be selected based on the mode of operation.

<FIG> and <FIG> show the transmitter <NUM> during operation, in accordance with some examples. In <FIG>, the first quadrature modulator and related circuits/functions are enabled and the second quadrature modulator and related circuits/functions are not turned on, such that the transmitter <NUM> is in <NUM>-Phase operation. Enabling the first quadrature modulator includes turning on power to the components of the first quadrature modulator (indicated in the figure by hashing) and related circuits/functions, and turning off or refraining from turning on the second quadrature modulator includes turning off power to the components of the second quadrature modulator and related circuits/functions. In <FIG>, the first and second quadrature modulators and related circuits/functions are enabled, such that the transmitter <NUM> is in <NUM>-Phase operation. Enabling the first and second quadrature modulators includes turning on power to the components of the first and second quadrature modulators (indicated in the figure by hashing) and related circuits/functions.

<FIG> is a flow diagram of a method <NUM> for controlling spurious emission of a mobile device <NUM>, in accordance with some examples. The method <NUM> may be performed during operation, such as when controlling the transmitter <NUM> to perform a transmission. For example, the method <NUM> may be performed by the power controller <NUM>. The transmitter <NUM> is controlled according to CIM requirements. The current transmission parameters are obtained (step <NUM>). The transmission parameters include the current frequency band, the target antenna power, and the current LTE RB configurations. When the current RB configuration does not raise CIM concerns (step <NUM>), the mode is switch to <NUM>-Phase operation to save power (step <NUM>). <NUM>-Phase operation is enabled by turning on the first quadrature modulator and related circuits/functions and turning off the second quadrature modulator and related circuits/functions. Conversely, when the current RB configuration raises CIM concerns, further inquiry is performed to determine the operating mode. The current threshold operating level is determined based on the current frequency band (step <NUM>). The current threshold may be determined based on a threshold lookup table indexed by the current frequency band. When the configured target antenna power exceeds the current threshold (step <NUM>), the mode is switch to <NUM>-Phase operation to achieve high CIM performance (step <NUM>). When the configured target antenna power is less than or equal to the current threshold, <NUM>-Phase operation is used.

<FIG> is a flow diagram of a method <NUM> for controlling spurious emission of a mobile device <NUM>, in accordance with some examples. The method <NUM> may be performed when controlling the transmitter <NUM> to perform a transmission. For example, the method <NUM> may be performed by the power controller <NUM>. In step <NUM>, parameters for a transmission are received. The transmission parameters include a current resource block configuration of a transmission to be performed by the transmitter <NUM>, a current transmission power of the transmission, and an operating band of the transmission. In step <NUM>, a threshold transmission power is determined according to an operating band of the transmission. In step <NUM>, a first quadrature modulator of the transmitter <NUM> is turned on. A second quadrature modulator of the transmitter <NUM> is refrained from being turned on, in response to the current resource block configuration being in the center of a channel for the transmission. In step <NUM>, the first and second quadrature modulators of the transmitter <NUM> are turned on, in response to the current transmission power being greater than the threshold transmission power.

<FIG> is a chart <NUM> showing power consumption of the transmitter <NUM> as a function of transmission output power. The chart <NUM> is a plot of experimentally collected test data. As can be seen, <NUM>-Phase operation is used at lower transmission output powers, greatly reducing power consumption. As transmission output power is increased, <NUM>-Phase operation is used. Power consumption is increased, however, using <NUM>-Phase operation may achieve sufficient CIM performance. On average, power consumption of a hybrid transmitter is <NUM>% lower than an <NUM>-Phase transmitter.

<FIG> is a block diagram of a processing system <NUM> for performing methods described herein, which may be installed in a host device. As shown, the processing system <NUM> includes a processor <NUM>, a memory <NUM>, and interfaces <NUM>-<NUM>, which may (or may not) be arranged as shown in <FIG>. The processor <NUM> may be any component or collection of components adapted to perform computations and/or other processing related tasks, and the memory <NUM> may be any component or collection of components adapted to store programming and/or instructions for execution by the processor <NUM>. In an example, the memory <NUM> includes a non-transitory computer readable medium. The interfaces <NUM>, <NUM>, <NUM> may be any component or collection of components that allow the processing system <NUM> to communicate with other devices/components and/or a user. For example, one or more of the interfaces <NUM>, <NUM>, <NUM> may be adapted to communicate data, control, or management messages from the processor <NUM> to applications installed on the host device and/or a remote device. As another example, one or more of the interfaces <NUM>, <NUM>, <NUM> may be adapted to allow a user or user device (e.g., personal computer (PC), etc.) to interact/communicate with the processing system <NUM>. The processing system <NUM> may include additional components not depicted in <FIG>, such as long term storage (e.g., nonvolatile memory, etc.).

In some examples, the processing system <NUM> is included in a network device that is accessing, or part otherwise of, a telecommunications network. In one example, the processing system <NUM> is in a network-side device in a wireless or wireline telecommunications network, such as a base station, a relay station, a scheduler, a controller, a gateway, a router, an applications server, or any other device in the telecommunications network. In other examples, the processing system <NUM> is in a user-side device accessing a wireless or wireline telecommunications network, such as a mobile station, a user equipment (UE), a personal computer (PC), a tablet, a wearable communications device (e.g., a smartwatch, etc.), or any other device adapted to access a telecommunications network.

In some examples, one or more of the interfaces <NUM>, <NUM>, <NUM> connects the processing system <NUM> to a transceiver adapted to transmit and receive signaling over the telecommunications network. <FIG> is a block diagram of a transceiver <NUM> adapted to transmit and receive signaling over a telecommunications network. The transceiver <NUM> may be installed in a host device. As shown, the transceiver <NUM> comprises a network-side interface <NUM>, a coupler <NUM>, a transmitter <NUM>, a receiver <NUM>, a signal processor <NUM>, and a device-side interface <NUM>. The network-side interface <NUM> may include any component or collection of components adapted to transmit or receive signaling over a wireless or wireline telecommunications network. The coupler <NUM> may include any component or collection of components adapted to facilitate bi-directional communication over the network-side interface <NUM>. The transmitter <NUM> may include any component or collection of components (e.g., up-converter, power amplifier, etc.) adapted to convert a baseband signal into a modulated carrier signal suitable for transmission over the network-side interface <NUM>. The receiver <NUM> may include any component or collection of components (e.g., down-converter, low noise amplifier, etc.) adapted to convert a carrier signal received over the network-side interface <NUM> into a baseband signal. The signal processor <NUM> may include any component or collection of components adapted to convert a baseband signal into a data signal suitable for communication over the device-side interface(s) <NUM>, or vice-versa. The device-side interface(s) <NUM> may include any component or collection of components adapted to communicate data-signals between the signal processor <NUM> and components within the host device (e.g., the processing system <NUM>, local area network (LAN) ports, etc.).

The transceiver <NUM> may transmit and receive signaling over any type of communications medium. In some examples, the transceiver <NUM> transmits and receives signaling over a wireless medium. For example, the transceiver <NUM> may be a wireless transceiver adapted to communicate in accordance with a wireless telecommunications protocol, such as a cellular protocol (e.g., long-term evolution (LTE), etc.), a wireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or any other type of wireless protocol (e.g., Bluetooth, near field communication (NFC), etc.). In such examples, the network-side interface <NUM> comprises one or more antenna/radiating elements. For example, the network-side interface <NUM> may include a single antenna, multiple separate antennas, or a multi-antenna array configured for multi-layer communication, e.g., single input multiple output (SIMO), multiple input single output (MISO), multiple input multiple output (MIMO), etc. In other examples, the transceiver <NUM> transmits and receives signaling over a wireline medium, e.g., twisted-pair cable, coaxial cable, optical fiber, etc. Specific processing systems and/or transceivers may utilize all of the components shown, or only a subset of the components, and levels of integration may vary from device to device.

Claim 1:
A device comprising:
a first quadrature modulator configured to receive an in-phase portion of a baseband signal and a quadrature portion of the baseband signal, and to produce a first portion of an output signal according to the in-phase and quadrature portions of the baseband signal;
a second quadrature modulator configured to receive a first modified signal and a second modified signal, and to produce a second portion of the output signal according to the first and second modified signals;
an output circuit (<NUM>) configured to sum the first and second portions of the output signal, and to transmit the output signal to an antenna (<NUM>); and
a mode selection circuit (<NUM>) configured to turn on the first quadrature modulator, to receive a control signal, and to determine whether to turn on the second quadrature modulator according to the control signal;
wherein the mode selection circuit (<NUM>) is configured to be coupled to a controller (<NUM>), the controller (<NUM>) configured to receive parameters of a transmission, and to produce the control signal according to the parameters of the transmission, wherein the parameters of the transmission comprise a current resource block configuration of the transmission, a current transmission power of the transmission, and an operating band of the transmission,
wherein the mode selection circuit (<NUM>) is further configured to:
refrain from turning on the second quadrature modulator in response to the current resource block configuration being in the center of a channel for the transmission,
wherein the mode selection circuit (<NUM>) is further configured to:
turn on the second quadrature modulator in response to the current resource block configuration being at the edge of a channel for the transmission, and
wherein the mode selection circuit (<NUM>) is further configured to:
determine a threshold transmission power according to the operating band of the transmission; and
refrain from turning on the second quadrature modulator in response to the current transmission power of the transmission being less than or equal to the threshold transmission power.