Patent Application
20150194944
1. Field
The present invention relates generally to impedance matching within a wireless communication device.
2. Background
A wireless communication device (e.g., a cellular phone or a smart phone) in a wireless communication system may transmit and receive data for two-way communication. The wireless communication device may include a transmitter for data transmission and a receiver for data reception. For data transmission, the transmitter may modulate a radio-frequency (RF) carrier signal with data to obtain a modulated signal, amplify the modulated signal to obtain an output RF signal having the proper output power level, and transmit the output RF signal via an antenna to a base station. For data reception, the receiver may obtain a received RF signal via the antenna and may condition and process the received RF signal to recover data sent by the base station.
The transmitter may include various circuits such as a power amplifier (PA), a filter, etc. The receiver may also include various circuits such as a low noise amplifier (LNA), a filter, etc. An antenna tuner (i.e. impedance matching circuit) may be coupled between the antenna and the transmitter and/or the receiver and may perform tuning (i.e. impedance matching) for the antenna, the power amplifier, or the LNA. The impedance matching circuit may have a large impact on the performance of the wireless communication device.
Transmitters often incorporate a balun for converting a differential signal into a single-ended signal. For example, wireless transmit circuitry may employ a balun for converting a differential signal generated by the wireless transmit circuitry into a single-ended signal for further amplification and transmission over a wireless channel. A common balun implementation includes two mutually coupled inductive elements, configured such that a differential voltage across the first (primary) balun element generates a corresponding single-ended voltage across the second (secondary) balun element. A balun is usually either placed at the antenna feed, prior to interfacing with active elements (i.e., the elements for processing the signals transmitted and received over an antenna) or directly implemented as an active element.
A need exists for an enhanced communication device. More specifically, a need exists for enhanced impedance matching within a radio-frequency circuit of a wireless communication device.
The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention can be practiced. The term “exemplary” used throughout this description means “serving as an example, instance, or illustration,” and should not necessarily be construed as preferred or advantageous over other exemplary embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary embodiments of the invention. It will be apparent to those skilled in the art that the exemplary embodiments of the invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the novelty of the exemplary embodiments presented herein.
As will be appreciated by a person having ordinary skill in the art, impedance matching multiple cellular frequency bands with a single balun topology may be challenging.
By engaging various inductors of device 100, tuning for three distinct frequency bands can be achieved. Although a wide tuning range can be achieved, silicon area increases due to two separate coils used. Furthermore, switches S, which are used to engage or disengage inductors, may be subjected to full signal swing when an inductor is inactive, which may cause distortion and reliability issues. Also, due to requiring two switches for differential implementation, insertion loss increases and floor planning complexity may also increase.
By closing switches S1 & S2, values of inductors L1 and L2 may be decreased, and hence, multiband tuning may be achieved. After closing of switches S1 and S2, the inductor values of L1 and L2 reduce by a factor of 1-k*k, where k is a coupling coefficient. However, inductors L3 & L4 significantly load primary inductors L1 & L2, which may increase insertion loss. For example, for 1:2 tuning range, value of inductors L1 and L2 drop to one-fourth of their original value, which may increase insertion loss by roughly 6 dB due to Q falling to one-fourth of its original value.
Exemplary embodiments, as described herein, are directed to a device, which may be configured for wideband matching within a wireless communication device. The device, which may comprise a single, area efficient, balun, may include a single reactive passive element and be configured for providing impedance matching for multiple cellular frequency bands. By way of example, and not limitation, the device may be configured for impedance matching a frequency range of substantially 600 MHz to 2.9 GHz. As a more specific example, the device may be configured to provide matching for a power amplifier (PA) of a wireless transmitter.
It is noted that although some of the exemplary embodiments of the present invention are described herein as being implemented with a wireless transmitter, the present invention is not so limited. Rather, the present invention may be applied to any RF circuit that requires wideband tuning. As non-limiting examples, the device may provide tuning (i.e., matching) for mixers, RF amplifiers, voltage controlled oscillators (VCOs), and the like.
According to one exemplary embodiment, a device may include a primary winding including a first plurality of inductors in series. Further, the device may include a first switch coupled to the primary winding and configured to tune the primary winding according to a selected frequency band. In addition, the device may include a secondary winding including a second plurality of inductors in series. The device may also include a second switch coupled to the secondary winding and configured to tune the secondary winding according to the selected frequency band.
According to another exemplary embodiment, the present invention includes methods for wideband tuning. Various embodiments of such a method may include tuning a primary winding including a plurality of inductors in series according to a selected frequency band via a first switch coupled to the primary winding. The method may further include tuning a secondary winding including a second plurality of inductors in series according to the selected frequency band via a second switch coupled to the secondary winding.
Other aspects, as well as features and advantages of various aspects, of the present invention will become apparent to those of skill in the art through consideration of the ensuing description, the accompanying drawings and the appended claims.
Digital module 202 may comprise one or more processors 210 and memory 212.
RF module 204, which may comprise RF circuitry, may include a transceiver 205 including a transmitter 207 and a receiver 209 and may be configured for bi-directional wireless communication via an antenna 208. In general, electronic device 200 may include any number of transmitters and any number of receivers for any number of communication systems, any number of frequency bands, and any number of antennas. Further, according to an exemplary embodiment of the present invention, RF module 204, which may comprise, for example, a RF integrated circuit (RFIC), may include one or more of devices 300 (see
As illustrated in
According to one exemplary embodiment of the present invention, mixer 302, which, as noted above may comprise a Gilbert cell mixer, an amplifier, or both, may be used to drive an antenna load directly for area reduction, and device 304 may compensate for 3 db conversion loss and rejection for common mode noise of mixer 302. Furthermore, multiband tuning may be achieved by switching inductors of the balun windings. More specifically, for example, for low-frequency band (LB), switches S3 and S4 may be in an open configuration. For mid-band (MB) and high-band (HB) frequencies, switches S3 and S4 may be closed (i.e., shorted). Stated another way, for MB and HB frequencies, inductor L6 may be shorted out via closing switch S3, and inductor L8 may be shorted out via closing switch S4.
It is noted that in one exemplary embodiment, as illustrated in
As will be appreciated by a person having ordinary skill in the art, device 304, and, more specifically, primary winding 305 and secondary winding 307 together include a single reactive passive element for providing multiband impedance matching. Further, device 304 may provide for a multiband matching network while using relatively small silicon (Si) area. Further, compared to various conventional matching networks, device 304 may have reduced insertion loss. Also, as will be appreciated by a person having ordinary skill in the art, when switch S3 is open, a voltage across inductor L6 (“V_N2toN3”) (i.e., from node N2 to node N3) may be equal to a voltage across the plurality of inductors in primary winding 305 (“V_N1toN4”) (i.e., from node N1 to node N4)*[L6/(L5_A*L5_B+L6)]. Accordingly, a voltage swing across switch S3 is scaled by a factor of L6/(L5_A*L5_B+L6). Therefore, the switches of device 304 (i.e., switches S3 and S4) operate at lesser swings compared to conventional devices, and, thus, the reliability of switch operation in an “off” mode is enhanced. As will be appreciated by a person having ordinary skill in the art, when switch S3, which is across inductor L6, is open, voltage swings at node N2 and node N3 are of the same magnitude with opposite phases, which adds power efficiently in secondary winding 307. Further, when switch S3 is shorted, voltage swings at node N1 and node N4 are equal in magnitude and opposite in phase, which adds power efficiently in secondary winding 307. In contrast, if switch S3 is across either inductor L5_A or inductor L5_B and in an open configuration, voltage swings at node N1 and node N4 are not of the same magnitude and opposite phases, which may degrade power efficiency of a balun and may degrade harmonic cancellation as well. Further, in an embodiment wherein switch S3 is across either inductor L5 A or inductor L5 B and in a shorted configuration, a voltage swing at node N1 is lower than a voltage swing at node N4 by a factor of (L1/0.5*L2+1). These asymmetric voltage swings at node N1 and node N4 may degrade eventual power delivery by a balun and may also degrade harmonic rejections.
In addition, according to one example, device 400 includes coils 408, which may comprise inductor L5 of the primary winding (e.g., primary winding 305 of
As will be appreciated by a person having ordinary skill in the art, the present invention includes various advantages over conventional devices. For example, the present invention may require less area than device 100 (see
Those of skill in the art will understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.
Those of skill will further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the exemplary embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the exemplary embodiments of the invention.
The various illustrative logical blocks, modules, and circuits described in connection with the exemplary embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
The previous description of the disclosed exemplary embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these exemplary embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the exemplary embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
