Patent Application
20140194074
1. Field
The present disclosure is directed to a method and apparatus for wireless communication device multiband tunable radio architecture. More particularly, the present disclosure is directed to tunable filtering for a multiband wireless communication transceiver.
2. Introduction
Presently, a wireless communications multiband transceiver can transmit and receive wireless signals in multiple different frequency bands over a wireless communication network. The wireless communications multiband transceiver requires a dedicated duplex filter for each band. For a multiple antenna architecture, an additional antenna switch port or diplexing is also needed for each duplex filter. The wireless communications multiband transceiver must also provide isolation between transmit and receive frequencies to avoid transmit and receive signals from interfering in each other's signal paths.
Unfortunately, as the number of different frequency bands increase, the existing architecture becomes undesirable.
In order to describe the manner in which advantages and features of the disclosure can be obtained, a more particular description of the disclosure briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the disclosure and are not therefore to be considered to be limiting of its scope, the disclosure will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
A method and apparatus provide a wireless communication device multiband tunable radio architecture. The apparatus can include a multiband transceiver configured to transmit and receive wireless communication signals. The apparatus can include a tunable transmit notch filter coupled to the multiband transceiver. The tunable transmit notch filter can provide low insertion loss in a transmit band and attenuation at a receive frequency. The apparatus can include a tunable circulator coupled to the tunable transmit notch filter. The tunable circulator can provide transmit to receive isolation. The apparatus can include a tunable receive filter coupled to the multiband transceiver. The tunable receive filter can provide low insertion loss at a receive frequency and attenuation at other frequencies.
The WCN 100 includes wireless communications device (WCD) 102, which can be a mobile device, mobile station, a cell phone, a smartphone, a laptop, a tablet, or any other wireless enabled device. In one embodiment, WCD 102 is a subscriber device to WCN 100 and wirelessly connects to the infrastructure of WCN 100 via base station (BS) 105, which can include a base station antenna 106 and a base station controller 108. Base station antenna 106 provides an access point to WCN 100 for WCD 102. In addition to the base station components 106 and 108, the infrastructure of WCN 100 can include the MSC 110, which is connected to BSC 108 as well as to a backbone of interconnected functional servers (not shown) of WCN 100. As shown, MSC 110 connects to and communicates with several other known network components (not shown) and with gateway 116. BSC 108, MSC 110, and other servers in a network 140 operate according to any of the mentioned protocols. The WCD 102 is able to connect to services provided by server 112 as well as connect to other WCD and other telecommunication equipment through the network 140 and other networks 145.
The display 240 can be a liquid crystal display (LCD), a light emitting diode (LED) display, a plasma display, or any other means for displaying information. The transceiver 250 may include a transmitter and/or a receiver. The audio input and output circuitry 230 can include a microphone, a speaker, a transducer, or any other audio input and output circuitry. The user interface 260 can include a keypad, buttons, a touch pad, a joystick, an additional display, or any other device useful for providing an interface between a user and an electronic device. The memory 270 may include a random access memory, a read only memory, an optical memory, a subscriber identity module memory, or any other memory that can be coupled to a wireless communication device.
The tunable circulator 400 can operate at both the first carrier frequency and the second carrier frequency. The tunable circulator 400 can provide for carrier aggregation where one antenna can operate at both the first carrier frequency and the second carrier frequency. For example, for carrier aggregation, there can be multiple simultaneous transmissions and receptions. Two receive carriers at different carrier frequencies can be simultaneously received. The tunable circulator 400 can operate in two receive frequencies or bands at the same time. A tunable matching circuit 420 can provide an impedance match between the circulator 410 and the antenna 430 and can function at both of the receive carrier frequencies. Similarly two transmit signals can be simultaneously transmitted. The circulator 410 can operate in two transmit frequencies or bands at the same time. The tunable matching circuit 420 can provide an impedance match between the circulator 410 and the antenna 430 and can function at both of the transmit carrier frequencies.
The tunable circulator 400 can operate at both the first carrier frequency and the second carrier frequency. For example, for carrier aggregation there can be multiple simultaneous transmissions and receptions. As a further example, two receive carriers at different carrier frequencies can be simultaneously received. Thus, the tunable circulator 400 can operate in two receive frequencies or bands at the same time. In particular, the tunable matching circuit 420 can provide an impedance match between the circulator 410 and the antenna 430 and can function at both of the receive carrier frequencies. Similarly two transmit signals can be simultaneously transmitted. The circulator 410 can operate in two transmit frequencies or bands at the same time and the tunable matching circuit 420 can provide an impedance match between the circulator 410 and the antenna 430 and can function at both of the transmit carrier frequencies.
The tunable receive filter 340 provides a tunable frequency selective receive path for attenuating blocking signals which can cause a loss of receiver sensitivity in the multiband transceiver 310. Blocking signals can be transmit signals from the transceiver 310, interference signals from the antenna 350, or other signals caused by intermodulation of interference signals and transmit signals. The following blocking signal frequencies are possible problematic frequencies, listed in order from lowest to highest frequency, where RX denotes the receive frequency and TX denotes the transmit frequency:
The “duplex image” and “half duplex” blocking signals can be especially problematic, since these occur closest to the receive frequency and may be difficult to attenuate with fixed or broadband filtering. In a preferred embodiment, the tunable receive filter 340 can include a first tunable receive notch filter 610 coupled to the multiband transceiver 310. The first tunable receive notch filter 610 can provide low insertion loss in a receive band and attenuation at a transmit frequency. The tunable receive filter 340 can include a second tunable receive notch filter 620 coupled to the multiband transceiver 310. The second tunable receive notch filter 620 can provide low insertion loss in a receive band and attenuation at a duplex image frequency, the duplex image frequency being two times a transmit frequency minus a receive frequency. The second tunable receive notch filter 620 can further provide low insertion loss in the receive band and can provide attenuation at a half-duplex frequency, where the half-duplex frequency can be the sum of the transmit and receive frequencies divided by two. The tunable receive filter 340 can include at least one third tunable receive notch filter 630 that can provide additional filtering, such as some of the filtering described above and other useful filtering.
For example, the multiband transceiver 310 can transmit signals in at least one transmit band and can receive signals in at least one different receive band. For example, the multiband transceiver 310 can transmit and/or receive at least 6, at least 7, at least from 8-10, or at least more than 10 bands. The tunable circulator 330 can provide transmit signals from the multiband transceiver 310 via the tunable transmit notch filter 320 to the antenna 350 via the tunable antenna impedance match circuitry 420 and can provide received signals from the antenna 350 via the tunable antenna impedance match circuitry 420 to the multiband transceiver 310 via the tunable receive notch filters 340. The tunable circulator 330 can be a passive non-reciprocal multiport device that transmits radio frequency signals entering any port to another port in rotation. The tunable circulator 330 can route signals transmitted from the multiband transceiver 310 to the antenna 350 via tunable antenna impedance match circuitry 420 and can route signals received from the antenna 350 via tunable antenna impedance match circuitry 420 to the multiband transceiver 310, while suppressing the passage of signals between transmit and receive circuitry. The notch filters 320, 610, 620, and 630 can be tuned to a frequency and can significantly attenuate, such as reject, frequencies in a frequency band, such as a range of frequencies.
The multiband transceiver 310 can include a multiband multimode radio frequency transceiver including a wideband transmit port 660 coupled to the tunable transmit notch filter 320 and a wideband receive port 650 coupled to the tunable receive filter 340. The power amplifier 640 can be a wideband power amplifier coupled between the multiband transceiver 310 and the tunable transmit notch filter 320. Tunable elements can be configured to operate in third generation partnership project bands from 1-41 and additional bands. The multiband transceiver 310 can provide tuning control for at least some of the tunable notch filters 320, 610, 620, and 630. The multiband transceiver 310 can also provide tuning control for other elements, including the tunable circulator 330 and the tunable antenna impedance match circuitry 420. For example, the multiband transceiver 310 can provide tuning control to adjust at least one tunable element based on operating conditions of the apparatus 600. The tuning and performance for each element can be adjusted for operating conditions. The operating conditions can include transmit signal level, receive signal level, interference signal frequency, blocker signal frequency, interference level, blocker level, and other operating conditions. Operating conditions can be monitored during operation of the receiver for determining the frequency and level of interfering or blocking signals. The frequency and level can be determined in the receiver itself and by special-purpose detectors.
The tunable antenna impedance match circuitry 420 can provide a return loss, such as within 10-25 dB, to the tunable circulator 410 at transmit and receive frequencies. According to another example, the tunable antenna impedance match circuitry 420 provides a return loss within 15-20 dB. Each combination of the tunable circulator 330 and each of one of at least one of the tunable receive notch filters 340 can provide at least 45 dB receive isolation for a tuned notch frequency of each receive notch filter. A combination of the tunable circulator 330 and one of at least one of the tunable receive notch filter provides 340 can also provide at least 45 dB receive isolation for a tuned notch frequency of the one of the tunable receive notch filters 340. According to another example, a combination of the tunable circulator 330 and one of the tunable receive notch filters 340 can provide at least 50 dB receive isolation. Furthermore, the tunable circulator 330 can provide isolation within 15-35% of the receive isolation and the tunable notch filters 340 can provides isolation within 65-85% of the receive isolation. For example, a transmit to receive isolation of 50+dB can be shared between the tunable notch filters 340 and the tunable circulator 330. Another possible partitioning can include 35-40 dB from the tunable notch filters 340 and 15-20 dB from the tunable circulator 330.
The tunable antenna impedance match circuitry 420 can provide impedance matching between the circulator 410 and the antenna 350. Impedance matching circuits can employ reactive components, such as inductors and capacitors, to transform the impedance of the antenna 350 to the impedance of the circulator 410, which can be 50 Ohms. The antenna 350 may be a narrow band antenna. Tunable impedance matching can be used to operate a narrow band antenna over a wide range of operating frequencies. Furthermore, the antenna impedance may be affected by a variety of factors, including the position of the apparatus 600 with respect to a user's body and a state of a communication system. When the impedance of the antenna 350 changes, the matching circuit 420 can be tuned in order to keep the impedances as closely matched as possible. The tunable impedance matching circuitry 420 can provide a complex conjugate match between an impedance of the circulator 410 and a complex impedance of the antenna 350, which can be different from 50 Ohms. In this way, power transfer between the circulator 410 and the antenna 350 can be maximized and reflected power can be minimized. Since reflected power is minimized, the return loss, which is the ratio of reflected power to incident power, can be maximized. When properly controlled to maximize return loss, a tuning network impedance at the antenna port can be set to the complex conjugate of the antenna impedance. In this condition, the impedance of the tuning network at the circulator port can be the complex conjugate of the circulator 410. Thus, the tunable matching circuit 420 can transform the circulator impedance to the complex antenna impedance, and can transform the complex antenna impedance to the circulator impedance. In this way, the tunable matching circuit 420 can minimize return loss of transmit signals coupling from the circulator 410 to the antenna 350, and can minimize return loss of receive signals coupling from the antenna 350 into the circulator 410, thereby matching the impedance of circulator 410 and the antenna 350.
The circulator 410 can be an n-port device (n>2) with properties of directivity, where a radio frequency signal entering any port can be coupled most strongly to the next port in rotation. For example, for a three port circulator, a signal applied to a first port 412 couples mostly to the second port 414, a signal applied to the second port 414 couples mostly to the third port 416, and a signal applied to the third port 416 couples mostly to the first port 412. The circulator 410 directivity can cause signals entering the transceiver 310 from the antenna 350 at the circulator second port 414 to couple most strongly to the third port 416, which is connected to the a receive port 650 of the transceiver 310. If the antenna impedance is not well matched, then a portion of the receive signal may get reflected back out of the second circulator port 414 and flow into the first circulator port 412, and thus, can be lost for use in the receiver which is connected at the third circulator port 416. Similarly, a signal exiting the transceiver port 660 from the transceiver 310 at the first circulator port 412 will couple most strongly to the second port 414, which is connected to the antenna 350. If the second circulator port 414 impedance is not well matched to the antenna 350, then a portion of the transmit signal can get reflected from the antenna 350 back into the second circulator port 414, which couples most strongly into the third circulator port 416. The reflection of signals can be averted by properly matching the antenna 350 to the second circulator port 414
The figure of merit of an antenna system is the system efficiency, which can be defined as the ratio of radiated power to power available from the source. The system efficiency can be denoted in dB units as ηsys:
ηsys=10*Log10 [(radiated power)/(Power Available from the Source)]
The system efficiency can be broken down into two components: Radiation Efficiency and Delivered Power. In dB units, the radiation efficiency can be denoted as ηrad, and the delivered power can be denoted as Gmatch.
ηsys=ηrad+Gmatch
The radiation efficiency, ηrad, can be a property of the antenna, and the delivered power, Gmatch, can be a property of both the antenna and the matching circuit. Gmatch can be the ratio of power delivered to the antenna to the power available from the source. The figure of merit for antenna matching circuits can be the delivered power, GMATCH:
G
match=10*Log10 [(Power Delivered)/(Power Available from the Source)]
From equation 2, GMATCH targets can be obtained by subtracting the radiation efficiency, ηrad, (in dB) from the requirements for system efficiency, ηsys. Thus, the matching circuit 350 can serve to match the impedance for the purpose of maximizing the delivered power, Gmatch.
However, physically small antennas of the types used in portable devices tend to have narrow bandwidth and cannot transmit and receive efficiently over a wide range of transmit and receive frequencies. Furthermore, the impedance of antenna 350 can be variable, depending on proximity to objects which can, for example, cause capacitive or dielectric loading such as metal surfaces, or a user's hand or body. Tunable matching can be employed to reduce mismatch caused by low antenna bandwidth and caused by changing antenna impedance. The circulator 410 combined with the tunable antenna impedance matching circuit 420 can be the tunable circulator 330 that provides the tunable matching.
The apparatus 600 can makes use of shared, wide bandwidth signal paths with common tunable band reject elements and duplexing through the tunable circulator 330. A transmit to receive isolation of about 50+dB can be shared between the notch filters 340 and the tunable circulator 330. For example, the notch filters 340 can provide 35-40 dB and the tunable circulator 330 can provide 15-20 dB. Some embodiments can simplify high band count multiband devices by eliminating fixed, band dedicated duplex filters and eliminating a high throw antenna switch. The isolation formerly met by duplex filters can be achieved with tunable notch filters 340, a tunable circulator 330, and tunable antenna match circuitry 420. The antenna match circuitry 420 can be tuned to achieve transmit to receive isolation across the circulator 330.
The method of this disclosure is preferably implemented on a programmed processor. However, the controllers, flowcharts, and modules may also be implemented on a general purpose or special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an integrated circuit, a hardware electronic or logic circuit such as a discrete element circuit, a programmable logic device, or the like. In general, any device on which resides a finite state machine capable of implementing the flowcharts shown in the figures may be used to implement the processor functions of this disclosure.
While this disclosure has been described with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. For example, various components of the embodiments may be interchanged, added, or substituted in the other embodiments. Also, all of the elements of each figure are not necessary for operation of the disclosed embodiments. For example, one of ordinary skill in the art of the disclosed embodiments would be enabled to make and use the teachings of the disclosure by simply employing the elements of the independent claims. Accordingly, the preferred embodiments of the disclosure as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure.
In this document, relational terms such as “first,” “second,” and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “a,” “an,” or the like does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. Also, the term “another” is defined as at least a second or more. The terms “including,” “having,” and the like, as used herein, are defined as “comprising.”
