Hybrid distortion suppression system and method

Abstract

A method for reducing distortion in a radio frequency (RF) system includes: configuring multiple mixers to convert multiple phase signals and multiple RF signals; configuring a first mixer among the multiple mixers to operate in a six-phase operation mode to reduce distortion in the RF system; and configuring a second mixer among the multiple mixers to operate in a three-phase operation mode to reduce power consumption of the RF system.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 080,198, filed on September 18, 2020, entitled “Hybrid Distortion Suppression System and Method,” the contents of which are incorporated by reference into this application. Technical Field

[0003] The present invention generally relates to reducing distortion and improving power consumption in radio transmitters and / or receivers (or transceivers in general). Background Art

[0004] Wireless communication systems are widely used to provide voice and data services to multiple users through various access terminals (e.g., cellular phones, laptops, and various multimedia devices). Such communication systems may include local area networks, such as IEEE801.11 networks, cellular phones, and / or mobile broadband networks. Communication systems may use one or more multiple access technologies, such as frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), etc. Mobile broadband networks may comply with a variety of standards, such as Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), etc.

[0005] A wireless network may include wireless devices and multiple base stations. The wireless device may be a laptop, a mobile phone or a personal digital assistant (PDA), a media player, a gaming device, etc. The base station communicates with the wireless device via multiple wireless channels coupled between the wireless device and the base station (e.g., downlink channels from the base station to the wireless device). The wireless device may send information including channel information back to the base station via multiple feedback channels (e.g., uplink channels from the wireless device to the base station).

[0006] The wireless device may include a processor, a transmitter, and a receiver. The transmitter may be coupled to at least one transmit antenna. The receiver may be coupled to at least one receive antenna. The at least one transmit antenna and the at least one receive antenna may be the same antenna or different antennas. One of the main functions of the receiver is to suppress unwanted noise, such as signals including harmonics from adjacent channels and interference in general, so that the useful signal can be better recovered from the wide spectrum signal from the receive antenna.

[0007] As wireless technology has further developed, three-phase transmitters / receivers for harmonic suppression have become another option in mobile phones. One advantageous feature of three-phase transmitters / receivers is that they are able to eliminate many unwanted distortions in wireless networks.

[0008] One unfavorable characteristic of three-phase transmitters / receivers is that some distortion will still be present in the three-phase transmitter / receiver, for example, there will be second order counter intermodulation (CIM2). As the demand for large amounts of data communications increases, the requirement for lower distortion in RF systems becomes increasingly important. In such scenarios, CIM2 distortion may become the dominant factor in the handset, potentially causing interference and resulting in degraded performance of the handset. Therefore, it would be beneficial to reduce this distortion level to improve the performance of the RF system. Summary of the invention

[0009] Preferred embodiments of the present invention provide an integrated motor drive and isolated battery charger system that generally solves or circumvents these and other problems, and generally achieves technical advantages.

[0010] According to one embodiment, a method for reducing distortion in a radio frequency (RF) system includes: configuring multiple mixers to convert multiple phase signals and multiple RF signals; configuring a first mixer among the multiple mixers to operate in a six-phase operation mode to reduce distortion in the RF system; configuring a second mixer among the multiple mixers to operate in a three-phase operation mode to reduce power consumption of the RF system; and processing the multiple phase signals and the multiple RF signals with reduced distortion by configuring the first mixer among the multiple mixers to operate in the six-phase operation mode.

[0011] The plurality of mixers are in a transmitter of the RF system. The first mixer and the second mixer are both coupled to a single-ended power amplifier (PA), and the protected frequency band is adjacent to a first transmit frequency of a first RF signal generated by the first mixer and is away from a second transmit frequency of a second RF signal generated by the second mixer.

[0012] The plurality of mixers are in a transmitter of the RF system. The first mixer is coupled to a single-ended PA. The second mixer is coupled to a differential PA. The protected frequency band is adjacent to a second transmit frequency of a second RF signal generated by the second mixer.

[0013] The plurality of mixers are in a transmitter of the RF system. The first mixer and the second mixer are both coupled to a single-ended PA, and the protected frequency band is adjacent to a second transmit frequency of a second RF signal generated by the second mixer. The enabled digital pre-distortion algorithm is used to reduce a second order counter intermodulation (CIM2) component.

[0014] The plurality of mixers are in a receiver of the RF system, a blocking signal is adjacent to a second harmonic or a fourth harmonic of a first local oscillator (LO) frequency used by the first mixer, and a blocking signal is not adjacent to a second harmonic or a fourth harmonic of a second LO frequency used by the second mixer.

[0015] A second transmission frequency of the second RF signal processed by the second mixer is greater than a first transmission frequency of the first RF signal processed by the first mixer.

[0016] The method also includes: receiving a digital in-phase signal and an orthogonal phase signal; converting the digital in-phase signal and the orthogonal phase signal into a first phase digital signal having a phase shift of 0 degrees from the digital in-phase signal, a second phase digital signal having a phase shift of 120 degrees from the digital in-phase signal, and a third phase digital signal having a phase shift of 240 degrees from the digital in-phase signal; converting the first phase digital signal, the second phase digital signal, and the third phase digital signal into six phase baseband signals that are shifted by 60 degrees from each other through three digital-to-analog converters; and generating a first RF signal processed by the first mixer based on the six phase baseband signals and multiple LO signals.

[0017] The method also includes: generating three LO signals in a three-phase operation mode of the second mixer, wherein the three LO signals are offset by 120 degrees from each other, and the duty cycles of the three LO signals are approximately 33.33%; and generating six LO signals in a six-phase operation mode of the first mixer, wherein the six LO signals are offset by 60 degrees from each other, and the duty cycles of the six LO signals are approximately 16.67%.

[0018] The method further includes generating a voltage-controlled oscillator (VCO) signal in a phase-locked loop, wherein the VCO signal is used to generate the three LO signals in a three-phase operation mode of the second mixer and to generate the six LO signals in a six-phase operation mode of the first mixer.

[0019] The method further includes: in the six-phase operation mode, configuring the first mixer to mix the six-phase baseband signal with six LO signals to generate a first RF signal; in the three-phase operation mode, configuring the second mixer to mix the six-phase baseband signal with three LO signals to generate a second RF signal.

[0020] According to another embodiment, a method for reducing distortion in a radio frequency (RF) system includes: a local oscillator (LO) generator generates six LO signals, wherein the six LO signals are fed into a plurality of mixers; configuring a first mixer among the plurality of mixers to operate in a six-phase operation mode to reduce distortion in the RF system; configuring a second mixer among the plurality of mixers to operate in a three-phase operation mode to reduce power consumption of the RF system; and processing an RF signal of the RF system with reduced distortion by configuring the first mixer among the plurality of mixers to operate in the six-phase operation mode.

[0021] The plurality of mixers are in a transmitter of the RF system. The plurality of mixers are all coupled to a single-ended power amplifier (PA). A protected frequency band is adjacent to a first transmit frequency of a first RF signal generated by the first mixer, and the protected frequency band is not adjacent to a second transmit frequency of a second RF signal generated by the second mixer.

[0022] The method further includes configuring the first mixer to generate a first RF signal in a first frequency band, and configuring the second mixer to generate a second RF signal in a second frequency band greater than the first frequency band.

[0023] The method also includes: receiving a digital in-phase signal and an orthogonal phase signal; converting the digital in-phase signal and the orthogonal phase signal into a first phase digital signal with a phase shift of 0 degrees from the digital in-phase signal, a second phase digital signal with a phase shift of 120 degrees from the digital in-phase signal, and a third phase digital signal with a phase shift of 240 degrees from the digital in-phase signal; converting the first phase digital signal, the second phase digital signal, and the third phase digital signal into six phase baseband signals with a phase shift of 60 degrees from each other through three digital-to-analog converters; generating six LO signals in a six-phase operation mode of the first mixer, wherein the six LO signals are shifted by 60 degrees from each other and the duty cycles of the six LO signals are all about 16.67%; and generating a first RF signal generated by the first mixer according to the six phase signals and the six LO signals.

[0024] The method also includes: receiving a digital in-phase signal and an orthogonal phase signal; converting the digital in-phase signal and the orthogonal phase signal into a first phase digital signal with a phase shift of 0 degrees from the digital in-phase signal, a second phase digital signal with a phase shift of 120 degrees from the digital in-phase signal, and a third phase digital signal with a phase shift of 240 degrees from the digital in-phase signal; converting the first phase digital signal, the second phase digital signal, and the third phase digital signal into six phase baseband signals with a phase shift of 60 degrees from each other through three digital-to-analog converters; generating three LO signals in a three-phase operation mode of the second mixer, wherein the three LO signals are shifted by 120 degrees from each other, and the duty cycles of the three LO signals are all about 33.33%; and generating a second RF signal generated by the second mixer according to the six phase signals and the three LO signals.

[0025] According to yet another embodiment, a radio frequency (RF) system includes: a local oscillator (LO) generator for generating a plurality of LO signals; a first mixer for receiving six phase signals offset by 60 degrees from each other and six LO signals generated by the LO generator, wherein the first mixer is configured to operate in a six-phase mode, in which the six phase signals are mixed with the six LO signals to generate a first RF signal; and a second mixer for receiving the six phase signals and the three LO signals generated by the LO generator, wherein the second mixer is configured to operate in a three-phase mode, in which the six phase signals are mixed with the three LO signals to generate a second RF signal.

[0026] The system further includes: a third mixer, configured to receive the six phase signals and the six LO signals. The third mixer is configured to operate in the six-phase mode, wherein the six phase signals are mixed with the six LO signals in the six-phase mode to generate a third RF signal, wherein the first RF signal is in a low frequency band, the second RF signal is in an ultra-high frequency band, and the third RF signal is in a high frequency band.

[0027] The local oscillator includes: a voltage controlled oscillator (VCO) for generating a VCO signal; and a frequency LO generator for generating the multiple LO signals.

[0028] The system also includes: an IQ source for providing digital I and Q signals; an IQ to three-phase converter for converting the VCO digital I and Q signals into a first phase digital signal, a second phase digital signal and a third phase digital signal; a first digital-to-analog converter, a second digital-to-analog converter and a third digital-to-analog converter (voltage controlled oscillator, DAC) for converting the first phase digital signal, the second phase digital signal and the third phase digital signal into a first differential pair, a second differential pair and a third differential pair analog signal; a first filter, a second filter and a third filter for filtering the first differential pair, the second differential pair and the third differential pair analog signals and generating the six phase signals.

[0029] The system further includes a single-ended PA coupled to an output of the first mixer.

[0030] An advantage of an embodiment of the present invention is a hybrid mixer including a three-phase mixer and a six-phase mixer. The six-phase mixer is used to eliminate or reduce distortion in an RF system. The three-phase mixer is used to reduce power consumption in an RF system.

[0031] The foregoing has been a fairly extensive overview of the features and technical advantages of the present invention in order to better understand the detailed description of the disclosure below. Additional features and advantages of the present invention that form the subject of the claims of the present invention will be described below. It will be appreciated by those skilled in the art that the disclosed concepts and specific embodiments may be readily used as a basis for modifying or designing other structures or processes for achieving the same purpose of the present invention. It will also be appreciated by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the present invention as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] For a more complete understanding of the present invention and its advantages, reference is made to the following description in conjunction with the accompanying drawings, in which:

[0033] Figure 1 An exemplary wireless network provided by various embodiments of the present invention is shown;

[0034] Figure 2 The various embodiments of the present invention provide Figure 1 A block diagram of a UE shown in FIG.

[0035] Figure 3 The various embodiments of the present invention provide Figure 1 A block diagram of a base station shown in FIG.

[0036] Figure 4 The various embodiments of the present invention provide Figure 2 and Figure 3 A block diagram of a first implementation of a transmitter shown in FIG.

[0037] Figure 5 The various embodiments of the present invention provide Figure 2 and Figure 3 A block diagram of a second implementation of a transmitter shown in FIG.

[0038] Figure 6 The various embodiments of the present invention provide Figure 2 and Figure 3 A block diagram of a third implementation of a transmitter shown in FIG.

[0039] Figure 7 The various embodiments of the present invention provide Figure 4 A block diagram of a frequency synthesizer shown in;

[0040] Figure 8 The various embodiments of the present invention provide Figure 4 A block diagram of an IQ to three-phase converter is shown in FIG.

[0041] Fig. 9 The various embodiments of the present invention provide Figure 4 A block diagram of a six-phase / three-phase mixer is shown in FIG.

[0042] Fig.10 is a schematic diagram of a three-phase mixer provided by various embodiments of the present invention;

[0043] Fig.11 is a schematic diagram of a six-phase mixer provided by various embodiments of the present invention;

[0044] Fig.12 are multiple LO signals and accompanying duty cycles provided by various embodiments of the present invention;

[0045] Fig.13 is a general square waveform provided by various embodiments of the present invention;

[0046] Fig.14 is a block diagram of a receiver provided by various embodiments of the present invention;

[0047] Fig.15 is a flow chart of a method for reducing distortion provided by various embodiments of the present invention.

[0048] Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated.The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION

[0049] The manufacture and use of the currently preferred embodiments are discussed in detail below. However, it should be understood that the present invention provides many applicable inventive concepts that can be embodied in a variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to manufacture and use the present invention and do not limit the scope of the present invention.

[0050] The present invention will be described in a specific context with respect to a preferred embodiment, namely a hybrid mixer for improving the performance of a wireless network including multiple wireless devices (e.g., mobile phones) and multiple base stations. The hybrid mixer includes a first mixer, which is used to operate in a six-phase mode to eliminate or reduce distortion in an RF system. The hybrid mixer also includes a second mixer, which operates in a three-phase mode to reduce power consumption in the RF system. However, the present invention can also be applied to various radio frequency (RF) systems. In the following, various embodiments will be explained in detail with reference to the accompanying drawings.

[0051] Figure 1An exemplary wireless network provided by various embodiments of the present invention is shown. The wireless network 100 includes a base station 110, a plurality of mobile devices 120, and a backhaul network 130. The mobile device 100 can be implemented as any suitable end-user device, such as user equipment / device, a wireless transmitting / receiving unit, a mobile station, a laptop, a mobile phone, a personal digital assistant (PDA), a media player, a gaming device, a wireless sensor, a wearable device, etc. The mobile device 100 may include a receiver, a transmitter, an antenna, and other suitable components. Throughout the description, the mobile device may also be referred to as user equipment (UE).

[0052] A base station may refer to any component (or set of components) used to provide wireless access to a wireless network. A base station may be implemented as a base transceiver station (BTS), a 3G base station (NodeB), an evolved NodeB (eNB), a fifth generation (5G) base station, a home base station (Home NodeB), a macro cell, a femto cell, an access point (AP), or other wireless enabling devices.

[0053] like Figure 1 As shown, the base station 110 establishes an uplink connection and / or a downlink connection (dashed line) with the mobile device 120, which are used to transmit data from the mobile device 120 to the base station 110, and vice versa. The data transmitted through the uplink / downlink connection may include data transmitted between the mobile devices 120 and data transmitted to and from a remote (not shown) terminal through the backhaul network 130.

[0054] The mobile device 100 can transmit and receive wireless signals modulated based on various communication protocols (e.g., Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), LTE Advanced (LTE-A), and LTE Multimedia Broadcast Multicast Service (MBMS). In addition, the wireless signals can be modulated based on other standards such as Worldwide Interoperability for Microwave Access (WiMAX), Wireless Local Area Network (WLAN), and Ultra Wideband (UWB). In addition, the base station and the mobile device can be used to implement other suitable wireless protocols.

[0055] In some embodiments, the mobile device 120 and the base station use a hybrid transmitter and / or a hybrid receiver to perform transmissions. More specifically, the mixers of the hybrid transmitter and / or the hybrid receiver can be configured to operate in multiple ("hybrid") modes. Specifically, the mixers can be controlled to operate as three-phase mixers or six-phase mixers. When operating as a six-phase mixer, the hybrid transmitter / receiver consumes more power, but can also eliminate or reduce distortion in the RF system. When operating as a three-phase transmitter, the hybrid transmitter / receiver consumes less power.

[0056] Three-phase operation can be performed with relaxed distortion requirements, while six-phase operation can be performed with strict distortion requirements. The distortion requirements for transmission can be determined based on whether the protected frequency band is adjacent to the transmit frequency of the mixer. When the frequency band is not adjacent to the transmit frequency of the mixer, the distortion requirements are relaxed. Three-phase operation can be performed in the mixer to reduce power consumption. Throughout the description, six-phase operation can also be referred to as a six-phase operation mode. Three-phase operation can also be referred to as a six-phase operation mode.

[0057] Figure 2 The various embodiments of the present invention provide Figure 1 UE 110 can be implemented as a mobile phone, but can be a combination of the above Figure 1 Any suitable wireless device as described herein. Figure 2As shown, UE 110 includes a transmitter 202, a receiver 204, a memory 206, a processor 208, an input / output device 212, and an antenna 210. It should be noted that for simplicity, Figure 2 Only relevant components of UE 110 are shown. UE 100 may include other suitable components. Figure 2 One element is shown (eg, one processor 208), but UE 110 may include any number of such elements.

[0058] The processor 208 may implement various processing operations of the UE 110. For example, the processor 208 may perform signal encoding, data processing, power control, input / output processing, etc. The processor 208 may include any suitable processing device or computing device for performing one or more operations. For example, the processor 208 may include a microprocessor, a microcontroller, a digital signal processor, a field programmable gate array, an application specific integrated circuit, etc. The memory 206 may be implemented as a non-transitory memory.

[0059] The transmitter (TX) 202 is used to modulate data or other content for transmission through the antenna 210. Before feeding the signal to the antenna 210 for transmission, the transmitter 202 can receive a baseband digital signal, convert the baseband digital signal to an analog signal, filter the analog signal, up-convert the filtered analog signal to a radio frequency signal, and amplify the radio frequency signal. The amplified radio frequency signal is transmitted through the antenna 210.

[0060] Receiver (RX) 204 is used to demodulate data or other content received via antenna 210. Receiver 204 is used to receive an RF signal from antenna 210, amplify the RF signal, down-convert the RF signal to a baseband frequency analog signal, filter the baseband frequency analog signal, and convert the filtered baseband frequency analog signal into a baseband digital signal. The baseband digital signal is sent to a baseband processor for further processing to output voice or data. Receiver 204 may include any suitable structure for processing wirelessly received signals. Antenna 210 may include any suitable structure for transmitting and / or receiving wireless signals. The same antenna 210 may be used to transmit and receive RF signals, or alternatively, different antennas 210 may be used to transmit signals and receive signals.

[0061] It should be understood that one or more transmitters 202 may be used in the UE 110, one or more receivers 204 may be used in the UE 110, and one or more antennas 210 may be used in the UE 110. Although the at least one transmitter 202 and the at least one receiver 204 are shown as separate blocks or components, they may be combined into a transceiver. Therefore, a separate block of a transceiver may be shown instead of being shown in FIG. Figure 2The individual blocks of the transmitter 202 and the individual blocks of the receiver 204 are shown in FIG.

[0062] The input / output device 212 facilitates interaction with the user. The input / output device 212 includes any suitable structure for providing information to or receiving information from the user, such as a speaker, microphone, keyboard, display, touch screen, and any combination thereof.

[0063] The memory 206 stores instructions and data used, generated, or collected by the UE 110. For example, the memory 206 may store software instructions or firmware instructions executed by the processor 208. The memory 206 may be implemented as any suitable volatile and / or non-volatile storage and retrieval device, such as a random access memory (RAM), a read only memory (ROM), a hard disk, an optical disk, a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc.

[0064] Figure 3 The various embodiments of the present invention provide Figure 1 . The base station 120 includes a processor 308, a transmitter 302, a receiver 304, one or more antennas 310, and a memory 306. The processor 308 implements various processing operations, such as signal encoding, data processing, power control, input / output processing, etc. The processor 308 includes any suitable processing device or computing device for performing one or more operations. The processor 308 can be implemented as a microprocessor, a microcontroller, a digital signal processor, a field programmable gate array, an application specific integrated circuit, etc. The memory 306 is a non-transitory memory.

[0065] Transmitter 302 includes any suitable structure for generating signals for wireless transmission to one or more UEs 110 or other devices. The function of transmitter 302 is similar to Figure 2 The functions of the transmitter 202 shown in FIG. 1 are not described in detail. The receiver 304 includes any suitable structure for processing signals wirelessly received from one or more UEs 110 or other devices. The functions of the receiver 304 are similar to Figure 2 The functions of the receiver 204 shown in the figure are not described in detail. Although the transmitter 302 and the receiver 304 are shown as separate blocks or components, they can be combined into a transceiver. The antenna 310 includes any suitable structure for transmitting and / or receiving wireless signals. Figure 3A common antenna 310 is shown coupled to the transmitter 302 and the receiver 304, but more antennas 310 may be used according to different design requirements. The memory 306 may be implemented as any suitable volatile and / or non-volatile storage and retrieval device.

[0066] Figure 4 The various embodiments of the present invention provide Figure 2 and Figure 3 In some embodiments, the transmitter 400 may be configured to Figure 2 Alternatively, the transmitter 400 may also be used in a UE Figure 3 Furthermore, transmitter 400 may be used in any suitable radio frequency system.

[0067] like Figure 4 As shown, the transmitter 400 includes an IQ source 402, an IQ to three-phase converter 404, digital-to-analog converters (DAC) 412, 422 and 432, low pass filters (LPF) 414, 424 and 434, a six-phase / three-phase mixer 406, variable gain amplifiers (VGA) 413, 415, 423, 425, 433 and 435, transformers 410, 420 and 430, switches 416, 426 and 436, power amplifiers (PA) 417, 419, 427, 429, 437 and 439, a filter 409, an antenna 401 and a frequency synthesizer 408.

[0068] The IQ source 402 is used to provide a digital in-phase (I) signal and a digital quadrature-phase (Q) signal that are offset by 90 degrees from each other. More specifically, the IQ source 402 receives a digital input signal and converts the input signal into a digital in-phase signal and a digital quadrature-phase signal. In some embodiments, the digital input signal may be a voice signal and / or a data signal. Before the voice / data signal is converted into a digital in-phase signal and a digital quadrature-phase signal, the voice / data signal may undergo some suitable signal processing stages, such as frequency conversion, amplification, etc.

[0069] like Figure 4 As shown, the digital in-phase signal and the digital quadrature-phase signal are fed into an IQ to three-phase converter 404. The IQ to three-phase converter 404 converts the digital in-phase signal and the digital quadrature-phase signal into a first phase digital signal, a second phase digital signal, and a third phase digital signal.

[0070] like Figure 4 As shown, the first phase digital signal is phase-shifted by 0 degrees from the digital in-phase signal. The first phase digital signal can also be referred to as a 0-degree phase signal. The second phase digital signal is phase-shifted by 120 degrees from the digital in-phase signal. The second phase digital signal can also be referred to as a 120-degree phase signal. The third phase digital signal is phase-shifted by 240 degrees from the digital in-phase signal. The third phase digital signal can also be referred to as a 240-degree phase signal. Figure 8 The structure and operation principle of the IQ to three-phase converter 404 are described in detail.

[0071] Each DAC has a single-ended input and multiple differential outputs. At each DAC, two output differential analog signals are generated. The two output differential analog signals are offset 180 degrees from each other, one of which can be called a positive (P) signal and the other can be called a negative (N) signal.

[0072] like Figure 4 As shown, the first phase digital signal is fed into the first DAC 412. Through the first DAC 412, the first phase digital signal is converted into two baseband analog signals that are offset by 180 degrees from each other (0 degrees and 180 degrees, respectively, as shown in FIG. Figure 4 Similarly, the second phase digital signal is fed into the second DAC 422. Through the second DAC 422, the second phase digital signal is converted into two baseband analog signals that are 180 degrees offset from each other (120 degrees and 300 degrees, respectively, as shown in FIG. Figure 4 The third phase digital signal is fed into the third DAC 432. Through the third DAC 432, the third phase digital signal is converted into two baseband analog signals that are 180 degrees offset from each other (240 degrees and 60 degrees, respectively, as shown in FIG. Figure 4 shown).

[0073] Through these three DACs, the first phase digital signal, the second phase digital signal and the third phase digital signal are converted into six baseband analog signals that are offset by 60 degrees from each other, such as Figure 4 As shown. Throughout the description, these six baseband analog signals may also be referred to as phase baseband signals. These six baseband analog signals are fed into the six-phase / three-phase mixer 406 through LPFs 414, 424, and 434. LPFs 414, 424, and 434 are used to attenuate unwanted frequency components generated in the digital-to-analog conversion.

[0074] The frequency synthesizer 408 is a local oscillator (LO) generator. The frequency synthesizer 408 is capable of generating multiple LO signals to the six-phase / three-phase mixer 406. The six-phase / three-phase mixer 406 may include multiple mixers. In some embodiments, at least one mixer of the six-phase / three-phase mixer 406 is used to operate in a six-phase operation mode to reduce distortion in the transmitter 400. On the other hand, at least one mixer of the six-phase / three-phase mixer 406 is used to operate in a three-phase operation mode to reduce power consumption of the transmitter 400.

[0075] In the three-phase operation mode, the frequency synthesizer 408 is used to generate three LO signals (e.g., 5 GHz LO signals). The three LO signals include a 0-degree LO signal, a 120-degree LO signal offset by 120 degrees from the 0-degree LO signal, and a 240-degree LO signal offset by 240 degrees from the 0-degree LO signal. The three LO signals have the same frequency (e.g., 5 GHz) and the same duty cycle (e.g., 33.33%).

[0076] In the six-phase operation mode, the frequency synthesizer 408 is used to generate six LO signals (e.g., a 5 GHz LO signal). The six LO signals include a 0-degree LO signal, a 120-degree LO signal offset by 120 degrees from the 0-degree LO signal, a 240-degree LO signal offset by 240 degrees from the 0-degree LO signal, a 60-degree LO signal offset by 60 degrees from the 0-degree LO signal, a 180-degree LO signal offset by 180 degrees from the 0-degree LO signal, and a 300-degree LO signal offset by 300 degrees from the 0-degree LO signal. The six LO signals have the same frequency (e.g., 5 GHz) and the same duty cycle (e.g., 16.67%). Figure 7 The detailed structure of the frequency synthesizer 408 is described.

[0077] The six-phase / three-phase mixer 406 may include a plurality of mixers. The six-phase / three-phase mixer 406 is used to receive six baseband analog signals and the LO signal generated by the frequency synthesizer 408. In some embodiments, the six-phase / three-phase mixer 406 includes: a first mixer for generating a radio frequency signal in a low frequency band; a second mixer for generating a radio frequency signal in an ultra-high frequency band; and a third mixer for generating a radio frequency signal in a high frequency band.

[0078] In some embodiments, the protected frequency band is adjacent to the first transmission frequency of the first radio frequency signal generated by the first mixer. The protected frequency band is far away from the second transmission frequency of the second radio frequency signal generated by the second mixer. In order to prevent the distortion in the transmitter from interfering with the protected frequency band, the first mixer is configured to operate in a six-phase operation mode to eliminate or reduce the distortion. On the other hand, since the protected frequency band is far away from the second transmission frequency of the second mixer, the second mixer is configured to operate in a three-phase operation mode to reduce power consumption.

[0079] In the present invention, the six-phase operation mode can eliminate or reduce the distortion in the transmitter. Fig.13 This advantage is described in detail. In this embodiment, the protected frequency band can be a frequency band owned by one of the two wireless carriers operating in the same area. For example, the first wireless carrier has a frequency band of 4.0 GHz to 4.5 GHz. The second wireless carrier has a frequency band of 4.5 GHz to 5.0 GHz. For the first carrier, the frequency band owned by the second wireless carrier (for example, a frequency band around 4.51 GHz) is a protected frequency band. High-level interference to this frequency band (for example, distortion caused by the wireless device of the first wireless carrier) is prohibited.

[0080] In some embodiments, the six-phase / three-phase mixer 406 includes three mixers. The first mixer is used to operate in a six-phase operation mode. The first mixer is used to receive six baseband analog signals and six LO signals, and up-convert the six baseband analog signals to generate a first RF signal in a low frequency band. The second mixer is used to operate in a three-phase operation mode. The second mixer is used to receive six baseband analog signals and three LO signals, and up-convert the six baseband analog signals to generate a second RF signal in an ultra-high frequency band. The third mixer is used to operate in a six-phase operation mode. The third mixer is used to receive six baseband analog signals and six LO signals, and up-convert the six baseband analog signals to generate a third RF signal in a high frequency band. The following will be combined with Fig. 9 The detailed structure of the six-phase / three-phase mixer 406 is described.

[0081] The first RF signal is fed into VGAs 413 and 415. VGAs 413 and 415 are used to adjust the amplitude of the first RF signal to a predetermined level. The output end of VGA 413 is connected to a first terminal of the primary winding of transformer 410. The output end of VGA 415 is connected to a second terminal of the primary winding of transformer 410. Through transformer 410, the differential signal from six-phase / three-phase mixer 406 is converted into a single-ended signal.

[0082] The single-ended signal from the secondary winding of transformer 410 is fed into switch 416. Depending on the frequency, the single-ended signal can be routed to differential PAs (e.g., PAs 417 and 419). The output of the PA is fed into antenna 401 through filter 409. Filter 409 may include multiple filter banks and switches, such as Figure 4 Filter 409 is used to attenuate unwanted frequency components and route the appropriate signal to the antenna.

[0083] The second RF signal is fed into VGAs 423 and 425. VGAs 423 and 425 are used to adjust the amplitude of the second RF signal to a predetermined level. The output end of VGA 423 is connected to the first terminal of the primary winding of transformer 420. The output end of VGA 425 is connected to the second terminal of the primary winding of transformer 420. Through transformer 420, the differential signal from six-phase / three-phase mixer 406 is converted into a single-ended signal.

[0084] The single-ended signal from the secondary winding of transformer 420 is fed into switch 426. Depending on the frequency, the single-ended signal can be routed to differential PAs (e.g., PAs 427 and 429). The output of the PA is fed to antenna 401 through filter 409. Filter 409 is used to attenuate unwanted frequency components and route the appropriate signal to the antenna.

[0085] The third RF signal is fed into VGAs 433 and 435. VGAs 433 and 435 are used to adjust the amplitude of the third RF signal to a predetermined level. The output end of VGA 433 is connected to the first terminal of the primary winding of transformer 430. The output end of VGA 435 is connected to the second terminal of the primary winding of transformer 430. Through transformer 430, the differential signal from six-phase / three-phase mixer 406 is converted into a single-ended signal.

[0086] The single-ended signal from the secondary winding of transformer 430 is fed into switch 436. Depending on the frequency, the single-ended signal can be routed to different PAs (e.g., PA 437 and 439). The output of the PA is fed to antenna 401 through filter 409. Filter 409 is used to attenuate unwanted frequency components and route the appropriate signal to the antenna.

[0087] Figure 5 The various embodiments of the present invention provide Figure 2 and Figure 3 A block diagram of a second implementation of a transmitter is shown in FIG. Figure 5 The transmitter 500 shown is similar to Figure 4The transmitter shown is only a differential PA used to attenuate distortion. In some embodiments, the protected frequency band is adjacent to the second transmission frequency of the second RF signal generated by the second mixer. The second mixer is used to operate in a three-phase operation mode to reduce power consumption. In order to avoid interference with the protected frequency band caused by distortion, a differential PA (e.g., PA 429) is used. More specifically, through differential operation, the differential PA can cancel the second order counter intermodulation (CIM2) distortion generated due to the second order nonlinearity of the PA. Due to the differential PA (e.g., PA 429), the CIM2 distortion at the antenna 401 has been reduced.

[0088] Figure 6 The various embodiments of the present invention provide Figure 2 and Figure 3 A block diagram of a third implementation of a transmitter is shown in FIG. Figure 6 The transmitter 600 shown is similar to Figure 4 The transmitter shown is only that a digital pre-distortion (DPD) algorithm has been used to reduce the CIM2 component. In some embodiments, the protected frequency band is adjacent to the second transmission frequency of the second RF signal generated by the second mixer. The second mixer is used to operate in a three-phase operation mode to reduce power consumption. In order to avoid interference of distortion on the protected frequency band, the DPD function unit 403 is placed between the IQ source 400 and the IQ to three-phase converter 404. More specifically, the DPD function unit 403 generates a digital signal with the same level as the distortion signal but with an opposite phase. In the digital signal path, the digital signal generated by DPD and the distortion signal cancel each other. Due to the DPD algorithm, the CIM2 distortion at the antenna 401 has been reduced. Compared with a conventional orthogonal IQ system (such as a four-phase system), this three-phase DPD is used to reduce CIM2. In a four-phase system, DPD is used to reduce CIM3. DPD for reducing CIM2 requires a lower bandwidth and a lower digital sampling frequency than DPD for reducing CIM3. Such lower bandwidth and lower digital sampling frequency can help reduce DPD power consumption.

[0089] Figure 7 The various embodiments of the present invention provide Figure 4 4. The frequency synthesizer 408 includes a voltage controlled oscillator (VCO) 701. The VCO 701 is a part of a phase locked loop (PLL) 703. The VCO 701 is used to generate a VCO signal. In some embodiments, the duty cycle of the VCO signal generated by the VCO 701 is about 50%.

[0090] The VCO signal generated by VCO 701 is fed into the three-phase / six-phase generator 700. The three-phase / six-phase generator 700 is used as an LO generator. When the mixer is used to operate in the three-phase operation mode, the three-phase / six-phase generator 700 is used to generate a first LO signal clk0, a second LO signal clk120, and a third LO signal clk240. The three LO signals have the same frequency (e.g., 5 GHz) and the same duty cycle (e.g., 33.33%). The first LO signal clk0 can also be referred to as a 0-degree phase carrier signal. The second LO signal clk120 can also be referred to as a 120-degree phase carrier signal offset by 120 degrees from the 0-degree phase carrier signal. The third LO signal clk240 can also be referred to as a 240-degree phase carrier signal offset by 240 degrees from the 0-degree phase carrier signal. The three LO signals are fed into the mixer operating in the three-phase operation mode.

[0091] On the other hand, when the mixer is used to operate in the six-phase operation mode, the three-phase / six-phase generator 700 is used as a six-phase LO generator. More specifically, the six-phase LO generator is used to generate a first LO signal clk0, a second LO signal clk120, a third LO signal clk240, a fourth LO signal clk60, a fifth LO signal clk180, and a sixth LO signal clk300. These six LO signals have the same frequency (e.g., 5 GHz) and the same duty cycle (e.g., 16.67%).

[0092] The first LO signal clk0 may also be referred to as a 0-degree phase carrier signal. The second LO signal clk120 may also be referred to as a 120-degree phase carrier signal offset by 120 degrees from the 0-degree phase carrier signal. The third LO signal clk240 may also be referred to as a 240-degree phase carrier signal offset by 240 degrees from the 0-degree phase carrier signal. The fourth LO signal clk60 may also be referred to as a 60-degree phase carrier signal offset by 60 degrees from the 0-degree phase carrier signal. The fifth LO signal clk180 may also be referred to as a 180-degree phase carrier signal offset by 180 degrees from the 0-degree phase carrier signal. The sixth LO signal clk300 may also be referred to as a 300-degree phase carrier signal offset by 300 degrees from the 0-degree phase carrier signal. These six LO signals are fed into a mixer operating in a six-phase operation mode.

[0093] Figure 8 The various embodiments of the present invention provide Figure 4. The IQ to three-phase converter 404 includes mixers 702, 704, 706, and 708 and summers 710 and 712. The digital I signal is used to provide a 0 degree phase signal. The digital I signal is also fed into mixer 702, which weights the digital I signal by multiplying the digital I signal by 1 / 2. The digital I signal is also fed into mixer 708, where the digital I signal is weighted by the square root of 3 divided by 2.

[0094] The digital Q signal is fed into mixer 704, where the digital Q signal is weighted by the square root of 3 divided by 2. The digital Q signal is also fed into mixer 706, where the digital Q signal is weighted by 1 / 2. The outputs of mixers 702 and 704 are added by summer 710 to produce a 120 degree phase signal. The outputs of mixers 706 and 708 are added by summer 712 to produce a 240 degree phase signal.

[0095] It should be noted that Figure 8 The implementation of the IQ to three-phase converter shown in is only one example. Other techniques for providing an IQ to three-phase converter are also possible and within the scope of the embodiments described herein.

[0096] Fig. 9 The various embodiments of the present invention provide Figure 4 The six-phase / three-phase mixer 406 includes a first mixer 1002, a second mixer 1004 and a third mixer 1006. The three mixers are used to receive six baseband analog signals ( Fig. 9 0, 180, 120, 300, 240 and 60) and six LO signals (clk0, clk120, clk240, clk60, clk180 and clk300). Figure 4 The six baseband analog signals have been discussed, so I will not repeat them here. Figure 7 Six LO signals are discussed and therefore will not be repeated here.

[0097] In operation, in each mixer, the baseband analog signal and the LO signal are mixed to generate a radio frequency signal. In some embodiments, in order to reduce distortion in the transmitter, the first mixer 1002 and the third mixer 1006 are configured to operate in a six-phase operation mode. On the other hand, in order to reduce power consumption of the transmitter, the second mixer 1004 is configured to operate in a three-phase operation mode.

[0098] In operation, the first mixer 1002 is used to operate in a six-phase mode. The first mixer 1002 is used as a six-phase mixer. Fig.11 Describe the structure and operation of a six-phase mixer.

[0099] In the six-phase mode, the first mixer 1002 is used to receive six baseband analog signals and six LO signals. In the first mixer 1002, the six baseband analog signals are mixed with the six LO signals to generate a first RF signal. The first RF signal is in a low frequency band.

[0100] The second mixer 1004 is used to operate in a three-phase mode. The second mixer 1004 is used as a three-phase mixer. Fig.10 Describe the structure and operation principle of a three-phase mixer.

[0101] In the three-phase mode, the second mixer 1004 is used to receive six baseband analog signals and three LO signals (clk0, clk120 and clk240). In the second mixer 1004, the six baseband analog signals are mixed with the three LO signals to generate a second RF signal. The second RF signal is in the ultra-high frequency band. In other words, the second transmission frequency of the second RF signal processed by the second mixer 1004 is greater than the first transmission frequency of the first RF signal processed by the first mixer 1002.

[0102] In addition, the third mixer 1006 is used to operate in a six-phase mode. The third mixer 1006 is used as a six-phase mixer. In the six-phase mode, the third mixer 1006 is used to receive six baseband analog signals and six LO signals. In the third mixer 1006, the six baseband analog signals are mixed with the six LO signals to generate a third RF signal. The third RF signal is in a high frequency band. That is, the third transmission frequency of the third RF signal processed by the third mixer 1006 is between the first transmission frequency of the first RF signal processed by the first mixer 1002 and the second transmission frequency of the second RF signal processed by the second mixer 1004.

[0103] Fig.10 1 is a schematic diagram of a three-phase mixer provided by various embodiments of the present invention. The three-phase mixer includes mixers 111 to 116. A first baseband analog signal (with a phase shift of 0 degrees from the digital in-phase signal) and a first LO signal clk0 are fed to the mixer 111. The mixer 111 up-converts the frequency of the first baseband analog signal according to the first LO signal to generate a first p-type RF signal. A second baseband analog signal (with a phase shift of 180 degrees from the digital in-phase signal) and the first LO signal clk0 are fed to the mixer 114. The mixer 114 up-converts the frequency of the second baseband analog signal according to the first LO signal to generate a first n-type RF signal.

[0104] The third baseband analog signal (120 degrees phase-shifted from the digital in-phase signal) and the second LO signal clk120 are fed into the mixer 112. The mixer 112 up-converts the frequency of the third baseband analog signal according to the second LO signal to generate a second p-type RF signal. The fourth baseband analog signal (300 degrees phase-shifted from the digital in-phase signal) and the second LO signal clk120 are fed into the mixer 115. The mixer 115 up-converts the frequency of the fourth baseband analog signal according to the second LO signal to generate a second n-type RF signal.

[0105] The fifth baseband analog signal (phase-shifted 240 degrees from the digital in-phase signal) and the third LO signal clk240 are fed to the mixer 113. The mixer 113 up-converts the frequency of the fifth baseband analog signal according to the third LO signal to generate a third p-type RF signal. The sixth baseband analog signal (phase-shifted 60 degrees from the digital in-phase signal) and the third LO signal clk240 are fed to the mixer 116. The mixer 116 up-converts the frequency of the sixth baseband analog signal according to the third LO signal to generate a third n-type RF signal.

[0106] The first p-type RF signal generated by the mixer 111, the second p-type RF signal generated by the mixer 112, and the third p-type RF signal generated by the mixer 113 are combined together and fed into the VGA 433. The first n-type RF signal generated by the mixer 114, the second n-type RF signal generated by the mixer 115, and the third n-type RF signal generated by the mixer 116 are combined together and fed into the VGA 435.

[0107] Fig.11 1 is a schematic diagram of a six-phase mixer provided by various embodiments of the present invention. The six-phase mixer 1002 includes mixers 121 to 126 and mixers 131 to 136. A first baseband analog signal (with a phase shift of 0 degrees from the digital in-phase signal) and a first LO signal clk0 are fed to the mixer 121. The mixer 121 up-converts the frequency of the first baseband analog signal according to the first LO signal to generate a first p-type RF signal. A second baseband analog signal (with a phase shift of 180 degrees from the digital in-phase signal) and the first LO signal clk0 are fed to the mixer 131. The mixer 131 up-converts the frequency of the second baseband analog signal according to the first LO signal to generate a first n-type RF signal.

[0108] The third baseband analog signal (120 degrees phase-shifted from the digital in-phase signal) and the second LO signal clk120 are fed into the mixer 122. The mixer 122 up-converts the frequency of the third baseband analog signal according to the second LO signal to generate a second p-type RF signal. The fourth baseband analog signal (300 degrees phase-shifted from the digital in-phase signal) and the second LO signal clk120 are fed into the mixer 132. The mixer 132 up-converts the frequency of the fourth baseband analog signal according to the second LO signal to generate a second n-type RF signal.

[0109] The fifth baseband analog signal (phase-shifted 240 degrees from the digital in-phase signal) and the third LO signal clk240 are fed to the mixer 123. The mixer 123 up-converts the frequency of the fifth baseband analog signal according to the third LO signal to generate a third p-type RF signal. The sixth baseband analog signal (phase-shifted 60 degrees from the digital in-phase signal) and the third LO signal clk240 are fed to the mixer 133. The mixer 133 up-converts the frequency of the sixth baseband analog signal according to the third LO signal to generate a third n-type RF signal.

[0110] The sixth baseband analog signal (phase-shifted 120 degrees from the digital in-phase signal) and the fourth LO signal clk60 are fed to the mixer 124. The mixer 124 up-converts the frequency of the sixth baseband analog signal according to the fourth LO signal to generate a fourth p-type RF signal. The fifth baseband analog signal (phase-shifted 240 degrees from the digital in-phase signal) and the fourth LO signal clk60 are fed to the mixer 134. The mixer 134 up-converts the frequency of the fifth baseband analog signal according to the fourth LO signal to generate a fourth n-type RF signal.

[0111] The second baseband analog signal (180 degrees phase-shifted from the digital in-phase signal) and the fifth LO signal clk180 are fed into the mixer 125. The mixer 125 up-converts the frequency of the second baseband analog signal according to the fifth LO signal to generate a fifth n-type RF signal. The first baseband analog signal (0 degrees phase-shifted from the digital in-phase signal) and the fifth LO signal clk180 are fed into the mixer 135. The mixer 135 up-converts the frequency of the first baseband analog signal according to the fifth LO signal to generate a fifth n-type RF signal.

[0112] The fourth baseband analog signal (phase-shifted 300 degrees from the digital in-phase signal) and the sixth LO signal clk300 are fed to the mixer 126. The mixer 126 up-converts the frequency of the fourth baseband analog signal according to the sixth LO signal to generate a sixth n-type RF signal. The third baseband analog signal (phase-shifted 120 degrees from the digital in-phase signal) and the sixth LO signal clk300 are fed to the mixer 136. The mixer 136 up-converts the frequency of the third baseband analog signal according to the sixth LO signal to generate a sixth p-type RF signal.

[0113] The first p-type RF signal generated by the mixer 121, the second p-type RF signal generated by the mixer 122, the third p-type RF signal generated by the mixer 123, the fourth p-type RF signal generated by the mixer 124, the fifth p-type RF signal generated by the mixer 125, and the sixth p-type RF signal generated by the mixer 126 are combined together and fed into the VGA 413. The first n-type RF signal generated by the mixer 131, the second n-type RF signal generated by the mixer 132, the third n-type RF signal generated by the mixer 133, the fourth n-type RF signal generated by the mixer 134, the fifth n-type RF signal generated by the mixer 135, and the sixth n-type RF signal generated by the mixer 136 are combined together and fed into the VGA 415.

[0114] Fig.12 and Fig.13 The concept of using six-phase operation to reduce or eliminate distortion in RF systems is shown. This concept is useful for understanding some mixers (e.g., Fig. 9 The reason why the first mixer 1002 shown in FIG. 1 is used to operate in a six-phase operating mode is helpful.

[0115] Fig.12 1 shows multiple LO signals and the associated duty cycles provided by various embodiments of the present invention. In some embodiments, there are N LO signals. The LO frequency of each LO signal is denoted as fLO. The frequency of the clock is equal to fLO*N / 2. The clock is generated by a VCO. Due to the VCO duty cycle error, the duty cycle of the clock may not be equal to 50%. Fig.12 As shown, T1 is not equal to T2. The duty cycle of the clock is not equal to 50%. The associated N LO clock phases (Phase 1, Phase 2, ... Phase N) have an alternating pattern of on-times T1 and T2, as shown in FIG. Fig.12 To better understand the impact of duty cycle error (such as Fig.12 As shown in Figure 1, a generic square wave is used to analyze the distortion caused by duty cycle error and how the six-phase operation mode can eliminate or reduce the cause of the distortion.

[0116] Fig.13FIG. 1 shows a general square wave provided by various embodiments of the present invention. A general square wave having a duty cycle equal to α / π is shown in FIG. Fig.13 shown.

[0117] The signal between 0 and 2π can be expressed as:

[0118]

[0119] Based on Fourier transform, the fixed duty cycle square waveform can be written as:

[0120]

[0121]

[0122] In formula (2) and formula (3), is the DC term. The second term Indicates the basic clock. represents the second-order harmonic. Indicates the m-th order harmonic.

[0123] Image distortion is related to the fundamental clock. The second-order LO harmonic is related to the third term above. Duty cycle error may produce two different gain factors. The first gain factor can be expressed as The second gain coefficient can be expressed as In both gain factors, D is the duty cycle. Return to Reference Fig.12 , different phases may have different duty cycles. Tl can be considered as the duty cycle (D). In this case, T2 is equal to (1–D). In other words, some phases (e.g., Fig.12 The gain factor of the phase 1) shown in FIG. 1 is expressed as Other phases (e.g. Fig.12 The gain factor of the phase 2) shown in FIG. 2 is expressed as

[0124] Depending on the gain factor, the useful output signal (TX) and image distortion of the mixer can be expressed by the following formula:

[0125]

[0126]

[0127] In formula (4) and formula (5), b m is the signal level of the mth baseband signal. m is the phase error of the mth baseband signal. m is the signal level of the mth LO clock signal. m is the phase error of the mth LO clock signal. N is the total number of phases.

[0128] In some embodiments, only the LO duty cycle error exists. The VCO runs at a frequency equal to fLO*N / 2. The LO duty cycle error produces the final LO clock duty cycle error. The following formula can be satisfied: When m is an even number, When m is an odd number, b m is equal to b, b is a constant. m is equal to 0. m is equal to 0. After considering these formulas, formula (4) and formula (5) can be simplified to:

[0129]

[0130]

[0131] When N is greater than or equal to 3 and N is not equal to 4, the image value of formula (7) is equal to 0. Formula (7) indicates that the three-phase operation mode or the six-phase operation mode can eliminate image distortion.

[0132] According to the above analysis, in order to reduce image distortion, six-phase operation mode (N=6) or three-phase operation mode (N=3) can be used, because both operation modes can suppress image distortion caused by VCO duty cycle error, which is usually the main source of image distortion in traditional orthogonal IQ systems. Usually, in TX systems, the high N value of VCO does not cause low-frequency operation problems. This problem usually occurs at high frequencies of the LO signal. This means that the six-phase operation mode can be used in low band (LB) and high band (HB). In the ultra-high band (UHB), six phases or three phases can be used according to CIM requirements.

[0133] The LO clock related harmonics in a generic N-phase system can be expressed as:

[0134]

[0135]

[0136]

[0137]

[0138] LOHD2n is the LO related second order harmonic. LOHD2n has the opposite sign of the useful TX baseband signal. LOHD2p is the LO related second order harmonic. LOHD2p has the same sign as the useful TX baseband signal. LOHD3n is the LO related third order harmonic. LOHD3n has the opposite sign of the useful TX baseband signal. LOHD3p is the LO related third order harmonic. LOHD3p has the same sign as the useful TX baseband signal.

[0139] Nonlinearity in RF systems can have multiple sources, such as nonlinearity of low-pass filters, nonlinearity of on-resistance of mixers, etc. Baseband second-order and third-order nonlinearity can generate second-order counter intermodulation (CIM2) and third-order counter intermodulation (CIM3). CIM2 and CIM3 can be expressed as:

[0140]

[0141]

[0142]

[0143]

[0144] Post-mixer nonlinearity can convert LOHDx (e.g., LOHD2n, LOHD2p, LOHD3n, and LOHD3p) to CIMx (e.g., CIM12 and CIM3). Equations (8) to (15) show that for a transmitter configured to operate in a six-phase operation mode, when the LO clock is ideally generated, CIM2n, CIM2p, CIM3n, CIM3p, LOHD2n, LOHD2p, LOHD3n, and LOHD3p are all canceled. For a transmitter configured to operate in a three-phase operation mode, when the LO clock is ideally generated, CIM2p, CIM3n, CIM3p, LOHD2p, LOHD3n, and LOHD3p are all canceled. In other words, the three-phase operation mode cannot eliminate or reduce LOHD2n and CIM2n.

[0145] In operation, LOHD2n and the desired TX signal will be mixed within the PA through second-order nonlinearity. If a single-ended PA is used, CIM2 distortion will be generated at the output of the PA.

[0146] Return to reference Figure 4, the combination of the three-phase operation mode and the six-phase operation mode can improve the performance of the RF system. More specifically, the CIM2 distortion under the single-ended PA can be tolerated because the strict frequency band (e.g., the protected frequency band) is not adjacent to the transmit frequency of the transmitter. The three-phase operation mode can be used to reduce the power consumption of the transmitter. On the other hand, when the protected frequency band is adjacent to the transmit frequency, the corresponding mixer is used to operate in the six-phase operation mode. Due to the operation in the six-phase mode, the clock-related second-order harmonics are cancelled. The CIM2 distortion at the antenna port has been reduced.

[0147] Return to reference Figure 5 , a differential PA can be used to reduce distortion. More specifically, because a differential PA can reduce distortion, it allows the mixer to operate in a three-phase operation mode even if there are strict CIM2 requirements (e.g., a protected frequency band is adjacent to the transmit frequency generated by the mixer). In some embodiments, the differential PA helps reduce CIM2 due to second-order nonlinearity through differential operation, thereby achieving low CIM2 at the antenna.

[0148] Return to reference Figure 6 , the DPD functional unit can be used to reduce distortion. More specifically, because the DPD functional unit can reduce distortion, the mixer is allowed to operate in a three-phase operation mode even if there are strict CIM2 requirements (e.g., the protected frequency band is adjacent to the transmit frequency generated by the mixer).

[0149] It is important to note that the distortion results above assume that the static mismatch has been removed. In other words, the digital correction circuitry and / or other appropriate correction circuitry is still used to remove the static portion of the image distortion. The static portion of the image distortion may be caused by various factors such as layout constraints. The static portion of the image correction can be determined from laboratory characterization, so factory-based part calibration is not required.

[0150] Fig.14 is a block diagram of a receiver provided by various embodiments of the present invention. In some embodiments, Figure 2 The receiver 1400 may be used in the UE shown. Alternatively, Figure 3 The receiver 1400 may also be used in the base station shown. Furthermore, the receiver 1400 may be used in any suitable radio frequency system.

[0151] Receiver 1400 includes a filter 459 , VGAs 467 , 469 , 477 , 479 , 487 and 489 , a six-phase / three-phase mixer 456 , a frequency synthesizer 458 , LPFs 464 , 474 and 484 , analog-to-digital converters (ADCs) 462 , 472 and 482 , and a three-phase to IQ converter 454 and IQ data 452 .

[0152] The VGA can be implemented as a low noise amplifier. The VGA applies appropriate gain to each RF signal. The output of the VGA is fed into a six-phase / three-phase mixer 456. The six-phase / three-phase mixer 456 is similar to Figure 4 The six-phase / three-phase mixer 406 is shown in FIG. 1 , and thus will not be described in detail again.

[0153] The mixers of the six-phase / three-phase mixer 456 are used to receive a plurality of LO signals from the frequency synthesizer 458. According to the LO signals, the mixers down-convert the frequency of the RF signal to a baseband frequency.

[0154] In some embodiments, a blocking signal may occur in the RF system. The blocking signal is a signal that is not in the signaling frequency band of interest but in other frequency bands. The blocking signal may block the signal of interest. In some embodiments, the blocking signal is adjacent to the second harmonic or fourth harmonic of the first LO frequency used by the first mixer of the six-phase / three-phase mixer 456, while the blocking signal is not adjacent to the second harmonic or fourth harmonic of the second LO frequency used by the second mixer of the six-phase / three-phase mixer 456. In response to the blocking signal, the first mixer of the six-phase / three-phase mixer 456 is used to operate in a six-phase operating mode to reduce distortion in the RF system. The second mixer of the six-phase / three-phase mixer 456 is used to operate in a three-phase operating mode to reduce power consumption of the RF system. The above has been combined Figure 4 The six-phase operation mode and the three-phase operation mode of the mixer have been discussed, so they will not be repeated here.

[0155] like Fig.14 As shown, the output of the six-phase / three-phase mixer 456 is filtered by the LPF and then converted by the ADC into a 0-degree digital signal, a 120-degree digital signal, and a 240-degree digital signal. In the three-phase to IQ converter 454, these three digital signals are converted into digital I and Q signals. The digital I and Q signals are fed into the IQ data 452.

[0156] Fig.15 is a flow chart of a method for reducing distortion provided by various embodiments of the present invention. Fig.15 The flowchart shown is merely an example, which should not unduly limit the scope of the claims. Those of ordinary skill in the art will recognize many variations, alternatives, and modifications. For example, Fig.15 The various steps shown in the drawings may be added, deleted, substituted, rearranged and repeated.

[0157] The radio frequency system includes a transmitter and / or a receiver. In the radio frequency system, a plurality of mixers are used to convert a baseband analog signal into radio frequency signals in different frequency bands. A first mixer among the plurality of mixers is used to convert the baseband analog signal into a first radio frequency signal in a low frequency band. A second mixer among the plurality of mixers is used to convert the baseband analog signal into a second radio frequency signal in an ultra-high frequency band. A third mixer among the plurality of mixers is used to convert the baseband analog signal into a third radio frequency signal in a high frequency band. In operation, the protected frequency band is adjacent to a first transmission frequency of a first RF signal generated by the first mixer. The protected frequency band is away from a second transmission frequency of a second RF signal generated by the second mixer.

[0158] In step 1502, multiple mixers are used to convert multiple phase signals and multiple RF signals. The multiple phase signals are Figure 4 Phase baseband signals generated by multiple DACs in the radio frequency system are shown. Multiple RF signals are signals to be transmitted by multiple antennas in the radio frequency system.

[0159] In step 1504, a first mixer among the plurality of mixers is configured to operate in a six-phase operation mode to reduce distortion in the radio frequency system. In the six-phase operation mode, the first mixer receives six LO signals and six baseband analog signals. Based on the six LO signals, the first mixer up-converts the six baseband analog signals into a first radio frequency signal in a low frequency band. The six-phase operation mode can eliminate or reduce distortion around the transmission frequency of the first radio frequency signal. Due to the presence of such distortion elimination, the radio frequency system does not interfere with the protected frequency band.

[0160] In step 1506, a second mixer among the plurality of mixers is configured to operate in a three-phase operation mode to reduce power consumption of the RF system. In the three-phase operation mode, the second mixer receives three LO signals and six baseband analog signals. According to the three LO signals, the second mixer up-converts the six baseband analog signals into a second RF signal in an ultra-high frequency band.

[0161] Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

[0162] In addition, the scope of the present invention is not intended to be limited to the specific embodiments of the processes, machines, manufactured products, material compositions, modules, methods and steps described in the specification. It will be readily understood by those skilled in the art from the disclosure of the present invention that processes, machines, manufactured products, material compositions, devices, methods or steps (including currently existing or later developed) that perform or achieve functions or results substantially the same as the corresponding embodiments described herein can be used according to the present invention. Therefore, the appended claims are intended to include these processes, machines, manufactured products, material compositions, modules, methods or steps within their scope. Therefore, the specification and the drawings are only regarded as an explanation of the present invention as defined by the appended claims, and are intended to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention.

Claims

1. A method for reducing distortion in a radio frequency (RF) system, characterized in that: The method comprises: A plurality of mixers are configured to convert a plurality of phase signals and a plurality of RF signals; configuring a first mixer of the plurality of mixers to operate in a six-phase operation mode to reduce distortion in the RF system; configuring a second mixer of the plurality of mixers to operate in a three-phase operation mode to reduce power consumption of the RF system; processing the plurality of phase signals and the plurality of RF signals with reduced distortion by configuring the first mixer of the plurality of mixers to operate in the six-phase operating mode; The multiple mixers are in a transmitter of the RF system, the first mixer and the second mixer are both coupled to a single-ended power amplifier (PA), and a protected frequency band is adjacent to a first transmission frequency of a first RF signal generated by the first mixer and is away from a second transmission frequency of a second RF signal generated by the second mixer; or, the multiple mixers are in a receiver of the RF system, a blocking signal is adjacent to a second harmonic or a fourth harmonic of a first local oscillator (LO) frequency used by the first mixer, and the blocking signal is not adjacent to a second harmonic or a fourth harmonic of a second LO frequency used by the second mixer.

2. The method according to claim 1, characterized in that A second transmission frequency of the second RF signal processed by the second mixer is greater than a first transmission frequency of the first RF signal processed by the first mixer.

3. The method according to claim 1 or 2, characterized in that: The method further comprises: receiving digital in-phase and quadrature-phase signals; Convert the digital in-phase signal and the quadrature-phase signal into a first phase digital signal having a phase shift of 0 degrees from the digital in-phase signal, a second phase digital signal having a phase shift of 120 degrees from the digital in-phase signal, and a third phase digital signal having a phase shift of 240 degrees from the digital in-phase signal; Converting the first phase digital signal, the second phase digital signal and the third phase digital signal into six phase baseband signals shifted by 60 degrees from each other through three digital-to-analog converters; A first RF signal processed by the first mixer is generated according to the six phase baseband signals and a plurality of LO signals.

4. The method according to claim 3, characterized in that The method further comprises: In a three-phase operation mode of the second mixer, three LO signals are generated, wherein the three LO signals are offset from each other by 120 degrees and the duty cycles of the three LO signals are all 33.33%; In the six-phase operation mode of the first mixer, six LO signals are generated, wherein the six LO signals are offset from each other by 60 degrees, and the duty cycles of the six LO signals are all 16.67%.

5. The method according to claim 4, characterized in that The method comprises: A voltage-controlled oscillator (VCO) signal is generated in a phase-locked loop, wherein the VCO signal is used to generate the three LO signals in a three-phase operation mode of the second mixer and to generate the six LO signals in a six-phase operation mode of the first mixer.

6. The method according to claim 4, characterized in that The method comprises: In the six-phase operation mode, configuring the first mixer to mix the six-phase baseband signal with six LO signals to generate a first RF signal; In the three-phase operation mode, the second mixer is configured to mix the six-phase baseband signal with three LO signals to generate a second RF signal.

7. A method for reducing distortion in a radio frequency (RF) system, characterized in that: The method comprises: A local oscillator (LO) generator generates six LO signals, wherein the six LO signals are fed into a plurality of mixers; configuring a first mixer of the plurality of mixers to operate in a six-phase operation mode to reduce distortion in the RF system; configuring a second mixer of the plurality of mixers to operate in a three-phase operation mode to reduce power consumption of the RF system; processing an RF signal of the RF system with reduced distortion by configuring the first mixer of the plurality of mixers to operate in the six-phase operating mode; The multiple mixers are in a transmitter of the RF system; the multiple mixers are all coupled to a single-ended power amplifier (PA); the protected frequency band is adjacent to a first transmission frequency of a first RF signal generated by the first mixer, and the protected frequency band is not adjacent to a second transmission frequency of a second RF signal generated by the second mixer.

8. The method according to claim 7, characterized in that The method further comprises: configuring the first mixer to generate a first RF signal in a first frequency band; The second mixer is configured to generate a second RF signal in a second frequency band greater than the first frequency band.

9. The method according to claim 7 or 8, characterized in that: The method further comprises: receiving digital in-phase and quadrature-phase signals; Convert the digital in-phase signal and the quadrature-phase signal into a first phase digital signal having a phase shift of 0 degrees from the digital in-phase signal, a second phase digital signal having a phase shift of 120 degrees from the digital in-phase signal, and a third phase digital signal having a phase shift of 240 degrees from the digital in-phase signal; Converting the first phase digital signal, the second phase digital signal and the third phase digital signal into six phase baseband signals shifted by 60 degrees from each other through three digital-to-analog converters; In a six-phase operation mode of the first mixer, six LO signals are generated, wherein the six LO signals are offset from each other by 60 degrees and the duty cycles of the six LO signals are all 16.67%; A first RF signal generated by the first mixer is produced according to the six phase baseband signals and the six LO signals.

10. The method according to claim 7 or 8, characterized in that: The method further comprises: receiving digital in-phase and quadrature-phase signals; Convert the digital in-phase signal and the quadrature-phase signal into a first phase digital signal having a phase shift of 0 degrees from the digital in-phase signal, a second phase digital signal having a phase shift of 120 degrees from the digital in-phase signal, and a third phase digital signal having a phase shift of 240 degrees from the digital in-phase signal; Converting the first phase digital signal, the second phase digital signal and the third phase digital signal into six phase baseband signals shifted by 60 degrees from each other through three digital-to-analog converters; In a three-phase operation mode of the second mixer, three LO signals are generated, wherein the three LO signals are offset from each other by 120 degrees and the duty cycles of the three LO signals are all 33.33%; A second RF signal generated by the second mixer is produced according to the six phase baseband signals and the three LO signals.

11. A radio frequency (RF) system, characterized in that: The system comprises: A local oscillator (LO) generator, for generating a plurality of LO signals; a first mixer for receiving six phase signals shifted by 60 degrees from each other and six LO signals generated by the LO generator, wherein the first mixer is configured to operate in a six-phase mode, and the six phase signals are mixed with the six LO signals in the six-phase mode to generate a first RF signal; a second mixer for receiving the six phase signals and the three LO signals generated by the LO generator, wherein the second mixer is configured to operate in a three-phase mode, and the six phase signals are mixed with the three LO signals in the three-phase mode to generate a second RF signal; The first mixer and the second mixer are in a transmitter of the RF system; the first mixer and the second mixer are both coupled to a single-ended power amplifier (PA); a protected frequency band is adjacent to a first transmission frequency of a first RF signal generated by the first mixer, and the protected frequency band is not adjacent to a second transmission frequency of a second RF signal generated by the second mixer.

12. The system according to claim 11, characterized in that The system further comprises: a third mixer, configured to receive the six phase signals and the six LO signals, wherein the third mixer is configured to operate in the six-phase mode, the six phase signals are mixed with the six LO signals in the six-phase mode to generate a third RF signal, the first RF signal is in a low frequency band, the second RF signal is in an ultra-high frequency band, and the third RF signal is in a high frequency band.

13. The system according to claim 11 or 12, characterized in that The local oscillator comprises: A voltage controlled oscillator (VCO) for generating a VCO signal; A frequency LO generator is used to generate the multiple LO signals.

14. The system according to claim 13, characterized in that The system further comprises: An IQ source, used for providing digital I and Q signals; An IQ to three-phase converter, configured to convert the digital I and Q signals into a first phase digital signal, a second phase digital signal and a third phase digital signal; A first digital-to-analog converter, a second digital-to-analog converter and a third digital-to-analog converter (DAC), configured to convert the first phase digital signal, the second phase digital signal and the third phase digital signal into a first differential pair, a second differential pair and a third differential pair analog signal; The first filter, the second filter and the third filter are used to filter the first differential pair, the second differential pair and the third differential pair analog signals and generate the six phase signals.

15. The system according to claim 14, characterized in that The system further comprises: A single-ended PA is coupled to the output of the first mixer.

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