Remote front-end for a multi-antenna station
A multi-antenna station has multiple remote front-ends coupled to multiple antennas. Each remote front-end includes a power amplifier (PA), a low noise amplifier (LNA), and first and second coupling units. On the transmit path, a first RF signal is received via a first port, routed by the first coupling unit to the power amplifier, amplified to obtain the desired output power level, and routed by the second coupling unit to a second port for transmission via the antenna. On the receive path, a second RF signal is received via the second port, routed by the second coupling unit to the LNA, amplified to obtain a higher signal level, and routed by the first coupling unit to the first port for transmission to the transceiver.
The present Application for Patent claims priority to Provisional Application Ser. No. 60/615,891, entitled “Remote Front-End for a Multi-Antenna Station,” filed Oct. 4, 2004, assigned to the assignee hereof, and expressly incorporated herein by reference.
BACKGROUND1. Field
The present invention relates generally to electronics, and more specifically to a wireless multi-antenna station.
2. Background
A multiple-input multiple-output (MIMO) communication system employs multiple (T) transmit antennas at a transmitting station and multiple (R) receive antennas at a receiving station for data transmission. A MIMO channel formed by the T transmit antennas and R receive antennas may be decomposed into S spatial channels, where S≦min{T, R}. The S spatial channels may be used to transmit data in parallel to achieve higher throughput and/or redundantly to achieve greater reliability.
A multi-antenna station is equipped with multiple antennas that may be used for data transmission and reception. Each antenna is typically associated with a transceiver that includes (1) transmit circuitry used to process a baseband output signal and generate a radio frequency (RF) output signal suitable for transmission via the antenna and (2) receive circuitry used to process an RF input signal received via the antenna and generate a baseband input signal. The multi-antenna station also has digital circuitry for processing data for transmission and reception.
The antennas of the multi-antenna station may not be located near the transceivers for various reasons. For example, it may be desirable to place the antennas at different locations and/or with sufficient separation in order to (1) decorrelate the spatial channels as much as possible and (2) achieve good reception of RF input signals and transmission of RF output signals. As another example, the multi-antenna station may be designed such that it is not possible to locate the antennas near their associated transceivers. In any case, if the antennas are not located near the transceivers, then relatively long RF cables or transmission lines are needed to connect the antennas to the transceivers. A fair amount of signal loss may result from the long connection between the antennas and the transceivers. This signal loss increases the receiver noise figure on the receive path and lowers the transmit power level on the transmit path. These effects make the system less power efficient and degrade performance.
There is therefore a need in the art for techniques to connect the antennas to the transceivers.
SUMMARYTechniques for connecting multiple antennas to multiple transceivers in a multi-antenna station are described herein. According to an embodiment of the invention, a station equipped with multiple antennas is described which includes multiple transceivers and multiple remote front-ends. Each transceiver performs signal conditioning for RF signals transmitted and received via an associated antenna. Each remote front-end couples to an associated transceiver and an associated antenna, amplifies a first RF signal received from the associated transceiver to generate a first amplified RF signal for transmission from the associated antenna, and further amplifies a second RF signal received from the associated antenna to generate a second amplified RF signal for transmission to the associated transceiver.
According to another embodiment, a station equipped with multiple antennas is described which includes means for performing signal conditioning for RF signals transmitted and received via the antennas, means for power amplifying RF modulated signals received from the means for performing signal conditioning to generate amplified RF modulated signals for transmission from the antennas, and means for low noise amplifying RF input signals received from the antennas to generate amplified RF input signals for transmission to the means for performing signal conditioning. The means for power amplifying and the means for low noise amplifying are separate from the means for performing signal conditioning.
According to yet another embodiment, an apparatus suitable for use with a station equipped with multiple antennas is described which includes first and second amplifiers and first and second coupling units. The first amplifier receives and amplifies a first radio frequency (RF) signal and provides a first amplified RF signal. The second amplifier receives and amplifies a second RF signal and provides a second amplified RF signal. The first coupling unit couples the first RF signal from a first port to the first amplifier and couples the second amplified RF signal from the second amplifier to the first port. The second coupling unit couples the first amplified RF signal from the first amplifier to a second port and couples the second RF signal from the second port to the second amplifier.
According to yet another embodiment, an apparatus suitable for use with a station equipped with multiple antennas is described which includes means for amplifying a first RF signal to generate a first amplified RF signal, means for amplifying a second RF signal to generate a second amplified RF signal, means for coupling the first RF signal from a first port to the means for amplifying the first RF signal, means for coupling the first amplified RF signal to a second port, means for coupling the second RF signal from the second port to the means for amplifying the second RF signal, and means for coupling the second amplified RF signal to the, first port.
According to yet another embodiment, a transceiver module for use in a station equipped with multiple antennas is described which includes first and second transceivers, an oscillator, and a driver. Each transceiver performs signal conditioning for RF signals transmitted and received via an associated set of at least one antenna.
The oscillator generates local oscillator (LO) signals used by the first and second transceivers for frequency conversion between baseband and RF. The driver receives the LO signals from the oscillator and drives the LO signals from the transceiver module.
According to yet another embodiment, a transceiver module for use in a station equipped with multiple antennas is described which includes means for performing signal conditioning for RF signals transmitted and received via at least two antennas, means for generating LO signals used for frequency conversion between baseband and RF, and means for driving the LO signals from the transceiver module.
Various aspects and embodiments of the invention are described in further detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.
Multi-antenna station 100 includes a MIMO unit 110 and N remote front-ends (RFEs) 140a through 140n for N antennas 150a through 150n, respectively. MIMO unit 110 includes a MIMO processor 120 and N transceivers 130. MIMO processor 120 performs digital processing for data transmission and reception. N transceivers 130 perform signal conditioning (e.g., amplification, filtering, frequency upconversion/downconversion, and so on) on the RF signals for the N antennas 150. N transceivers 130 couple to N remote front-ends 140a through 140n via cables 142a through 142n, respectively. Remote front-ends 140a through 140n further couple to N antennas 150a through 150n, respectively, via cables 144a through 144n, respectively. Antennas 150 may be located either close to or some distance away from MIMO unit 110, depending on the design of multi-antenna station 100.
Remote front-ends 140 condition (e.g., amplify and filter) RF modulated signals received from transceivers 130 and generate RF output signals for transmission from antennas 150. Remote front-ends 140 also condition RF input signals received from antennas 150 and generate conditioned RF input signals for transceivers 130. Remote front-ends 140 are located as close as possible to antennas 150 to reduce the signal loss in cables 144 between remote front-ends 140 and antennas 150.
Remote front-ends 140 may be optional, and may or may not be installed depending on various factors such as the supported applications, the desired performance, cost, and so on. Remote front-ends 140 may be installed to reduce signal loss between antennas 150 and transceivers 130, which may be desirable or necessary if the distance between the antennas and the transceivers is relatively long and the supported applications require high data rates. Remote front-ends 140 may be omitted for lower rate applications and/or if the distance between antennas 150 and transceivers 130 is relatively short. If remote front-ends 140 are omitted, then antennas 150 couple directly to transceivers 130 via cables 142.
For the embodiment shown in
The transmit and receive portions are indicated by the T/R control signal. Switch 210 allows remote front-end 140v to receive an RFE input signal from transceiver 130 and send an RFE output signal to the transceiver via a single port. This simplifies the connection between remote front-end 140v and transceiver 130.
For the transmit path, which is active during the transmit portion, switch 210 receives an RF modulated signal (which is the RFE input signal) from transceiver 130 via the first port and routes this RFE input signal to power amplifier 220. Power amplifier 220 amplifies the RFE input signal with a fixed or variable gain and provides the desire output signal level. Switch 240 receives the amplified RFE input signal from power amplifier 220 and routes this signal to filter 250. Filter 250 filters the amplified RFE input signal to remove out-of-band noise and undesired signal components and provides an RF output signal via the second port to antenna 150.
For the receive path, which is active during the receive portion, filter 250 receives an RF input signal from antenna 150 via the second port, filters this RF input signal, and provides a filtered RF input signal to switch 240. Switch 240 routes the filtered RF input signal to LNA 230, which amplifies the signal. LNA 230 may also have a fixed or variable gain and is designed to provide the desire performance (e.g., to have the desired noise figure). Switch 210 receives the amplified RF input signal (which is the RFE output signal) from LNA 230 and provides the RFE output signal via the first port to transceiver 130.
Remote front-end 140v may be used to provide low loss for the RF signals sent between the remote front-end and transceiver 130. Remote front-end 140v may also be used to provide the desired output power level for the RF output signal transmitted from antenna 150. For example, transceiver 130 may be implemented on an RFIC and may be capable of providing low or medium output power level for the RF modulated signal sent to remote front-end 140v. Power amplifier 220 within remote front-end 140v may then provide amplification and high output power level for the RF output signal.
Power amplifier 220 and/or LNA 230 may be powered down whenever possible to reduce power consumption. For example, power amplifier 220 (and possibly LNA 230) may be powered down when multi-antenna station 100 is idle. To further reduce power consumption, power amplifier 220 may be powered down during the receive portion based on the T/R control signal, and LNA 230 may be powered down during the transmit portion based on the T/R control signal, as indicated by the dashed line in
For the embodiment shown in
At transceiver 130x, an AC coupling/DC blocking capacitor 302 couples the RF signals between transceiver 130x and coaxial cable 310. An inductor 304 couples the DC supply voltage from a power source 306 to coaxial cable 310. Capacitor 302 and inductor 304 at transceiver 130x perform the same function as capacitor 202 and inductor 204, respectively, at remote front-end 140x.
For the embodiment shown in
Messenger cable 320 has a center conductor 322 that carries the T/R control signal from MIMO processor 120 to remote front-end 140x. Messenger cable 320 may share/utilize outer shield 314 of coaxial cable 310 (as shown in
The DC supply may be shut off if the remote front-ends are not installed. A sensing circuit within power source 306 in MIMO unit 110 can detect whether the remote front-ends are installed. This detection may be achieved in various manners. For example, the amount of current being consumed may be sensed, and no current consumption would indicate that the remote front-ends are not installed. As another example, the impedance of the wire carrying the DC supply may be sensed, and high or open impedance would indicate that the remote front-ends are not installed. If the remote front-ends are not installed, then power source 306 can shut off the DC supply.
For the embodiment shown in
The use of complementary types of connectors (e.g., female connector 620 and male connector 630) for the first and second ports of remote front-end 140x also allows for optional installation of remote front-end 140x. For example, remote front-end 140x may be installed if lower loss is desired for applications requiring high data rates. Remote front-end 140x may be omitted for applications that can tolerate more loss. In this case, cable 142x would couple directly to antenna 150x via connectors 610 and 640.
When transceiver modules 710a and 710b are used to support four antennas, transceiver module 710a serves as the master module and transceiver module 710b is the slave module. VCO 820a and PLL 830a within transceiver module 710a are enabled and generate local oscillator (LO) signals used by all four transceivers 810a through 810d for frequency upconversion and downconversion. VCO 820b and PLL 830b within transceiver module 710b are disabled, driver 834b and buffer 832a are also disabled, and driver 834a and buffer 832b are enabled. The LO signals from VCO 820a are provided via driver 834a and buffer 832b to transceivers 810c and 810d in the slave transceiver module 710b.
2×2 transceiver modules (as oppose to modules with more transceivers) may be efficiently used for multi-antenna stations with different numbers of antennas. For a multi-antenna station equipped with two antennas, only one 2×2 transceiver module 710 is needed, and no additional and unnecessary circuitry is wasted. In this case, VCO 820 and PLL 830 are enabled to generate the LO signals for the two transceivers 810 in the transceiver module, and driver 834 and buffer 832 are disabled. For a multi-antenna station equipped with four antennas such as the one shown in
Within transmitter unit 960, a digital-to-analog converter (DAC) 962 receives a stream of digital chips (which is the baseband input signal) from MIMO processor 120z, converts the chips to analog, and provides an analog baseband signal. A filter 964 then filters the analog baseband signal to remove undesired images generated by the digital-to-analog conversion and provides a filtered baseband signal. An amplifier (Amp) 966 amplifies and buffers the filtered baseband signal and provides an amplified baseband signal. A mixer 968 modulates a TX_LO signal from VCO 820a with the amplified baseband signal and provides an upconverted signal. A power amplifier 970 amplifies the upconverted signal and provides an RF modulated signal, which is routed through a switch (SW) 972 and provided to an associated remote front-end 140 for one antenna.
Within receiver unit 980, an LNA 982 receives an RFE output signal from the associated remote front-end 140 or an RF input signal from an associated antenna 150 via switch 972. LNA 982 amplifies the received RF signal and provides a conditioned signal having the desired signal level. A mixer 984 demodulates the conditioned signal with an RX_LO signal from VCO 820a and provides a downconverted signal. A filter 986 filters the downconverted signal to pass the desired signal components and to remove noise and undesired signals that may be generated by the frequency downconversion process. An amplifier 988 amplifies and buffers the filtered signal and provides an analog baseband signal. An analog-to-digital converter (ADC) 990 digitizes the analog baseband signal and provides a stream of samples (which is the baseband output signal) to MIMO processor 120z.
For clarity, the description above shows each remote front-end being coupled to one antenna, and each transceiver processing the RF signals for one antenna. In general, each remote front-end and/or each transceiver may be associated with a set of one or more antennas. If a remote front-end or transceiver is associated with multiple antennas, then these antennas may be viewed as a single (distributed) “antenna” for the remote front-end or transceiver.
The remote front-ends and transceiver modules described herein may be implemented on RF integrated circuits (RFICs), with discrete components, and so on.
For example, each remote front-end may be implemented on one RFIC. Each transceiver module may be implemented on one RFIC, or multiple transceiver modules may be implemented on one RFIC, possibly along with other circuitry. The remote front-ends and transceiver modules may be fabricated with various integrated circuit (IC) processes such as complementary metal oxide semiconductor (CMOS), bipolar, bipolar-CMOS (Bi-CMOS), gallium arsenide (GaAs), and so on. For example, each remote front-end may be fabricated on one GaAs RFIC. Certain circuit components (e.g., inductors) may be printed on an IC die or implemented with Micro-Electro-Mechanical Systems (MEMS) technologies.
For simplicity, the control signals used to control the operation of the remote front-ends and the transceiver modules are shown as being generated by MIMO processor 120 in the description above. In general, these control signals may be generated by various units such as, for example, an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing devices (DSPD), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a micro-controller, a microprocessor, or some other electronic unit designed to perform the functions described herein.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these 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 embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. An apparatus comprising:
- a first amplifier to receive and amplify a first radio frequency (RF) signal and provide a first amplified RF signal;
- a second amplifier to receive and amplify a second RF signal and provide a second amplified RF signal;
- a first coupling unit to couple the first RF signal from a first port to the first amplifier and to couple the second amplified RF signal from the second amplifier to the first port; and
- a second coupling unit to couple the first amplified RF signal from the first amplifier to a second port and to couple the second RF signal from the second,port to the second amplifier.
2. The apparatus of claim 1, wherein the first and second coupling units are switches.
3. The apparatus of claim 1, wherein the first and second coupling units couple the first RF signal from the first port to the first amplifier and couple the first amplified RF signal from the first amplifier to the second port during a transmit portion, and further couple the second RF signal from the second port to the second amplifier and couple the second amplified RF signal from the second amplifier to the first port during a receive portion.
4. The apparatus of claim 1, wherein the first and second coupling units are duplexers.
5. The apparatus of claim 1, wherein the first amplifier is a power amplifier (PA).
6. The apparatus of claim 1, wherein the second amplifier is a low noise amplifier (LNA).
7. The apparatus of claim 1, wherein the first amplifier, the second amplifier, or both the first and second amplifiers are disabled when not used for communication.
8. The apparatus of claim 1, wherein the first amplifier is disabled during a receive portion, and wherein the second amplifier is disabled during a transmit portion.
9. The apparatus of claim 1, wherein the second port is coupled to one of the multiple antennas in the station.
10. The apparatus of claim 1, wherein the first port is coupled to a transceiver in the station.
11. The apparatus of claim 1, wherein the first and second ports are coupled to different types of connectors.
12. The apparatus of claim 1, wherein the first and second ports are coupled to complementary types of connectors.
13. The apparatus of claim 1, wherein the first and second amplifiers and the first and second coupling units are fabricated on an RF integrated circuit (RFIC).
14. The apparatus of claim 1, wherein the first and second amplifiers and the first and second coupling units are fabricated on a gallium arsenide (GaAs) integrated circuit (IC).
15. An apparatus comprising:
- means for amplifying a first radio frequency (RF) signal and generating a first amplified RF signal;
- means for amplifying a second RF signal and generating a second amplified RF signal;
- means for coupling the first RF signal from a first port to the means for amplifying the first RF signal;
- means for coupling the first amplified RF signal to a second port;
- means for coupling the second RF signal from the second port to the means for amplifying the second RF signal; and
- means for coupling the second amplified RF signal to the first port.
16. The apparatus of claim 15, wherein the means for coupling the first RF signal and the means for coupling the first amplified RF signal are active during a transmit portion, and wherein the means for coupling the second RF signal and the means for coupling the second amplified RF signal are active during a receive portion.
17. The apparatus of claim 15, further comprising:
- means for disabling the means for amplifying the first RF signal; and
- means for disabling the means for amplifying the second RF signal.
18. A station equipped with a plurality of antennas, comprising:
- a plurality of transceivers, each transceiver performing signal conditioning for radio frequency (RF) signals transmitted and received via an associated antenna; and
- a plurality of remote front-ends, each remote front-end coupled to an associated transceiver and an associated antenna, each remote front-end amplifying a first RF signal received from the associated transceiver to generate a first amplified RF signal for transmission from the associated antenna and further amplifying a second RF signal received from the associated antenna to generate a second amplified RF signal for transmission to the associated transceiver.
19. The station of claim 18, further comprising:
- a plurality of cables, each cable coupling one transceiver to the associated remote front-end.
20. The station of claim 19, wherein each of the plurality of cables comprises
- a first cable to carry the first RF signal and the second amplified RF signal between the transceiver and the associated remote front-end.
21. The station of claim 20, wherein the first cable further carries DC power for the associated remote front-end.
22. The station of claim 20, wherein each of the plurality of cables further comprises
- a second cable to carry at least one control signal for the associated remote front-end.
23. The station of claim 22, wherein the first and second cables are bundled together.
24. The station of claim 18, wherein the plurality of transceivers are arranged in pairs, each pair of transceivers being implemented as a separate module.
25. The station of claim 24, wherein the module for each pair of transceivers comprises an oscillator to generate local oscillator (LO) signals for the transceivers in the pair.
26. The station of claim 24, wherein multiple modules are implemented for multiple pairs of transceivers, and wherein one module is designated to generate local oscillator (LO) signals for all transceivers in the multiple modules.
27. A station equipped with a plurality of antennas, comprising:
- means for performing signal conditioning for radio frequency (RF) signals transmitted and received via the plurality of antennas;
- means for power amplifying RF modulated signals received from the means for performing signal conditioning to generate amplified RF modulated signals for transmission from the plurality of antennas; and
- means for low noise amplifying RF input signals received from the plurality of antennas to generate amplified RF input signals for transmission to the means for performing signal conditioning, wherein the means for power amplifying and the means for low noise amplifying are separate from the means for performing signal conditioning.
28. The apparatus of claim 27, further comprising:
- means for coupling the means for performing signal conditioning to the means for power amplifying and the means for low noise amplifying.
29. A transceiver module, comprising:
- first and second transceivers, each transceiver performing signal conditioning for radio frequency (RF) signals transmitted and received via an associated set of at least one antenna;
- an oscillator to generate local oscillator (LO) signals used by the first and second transceivers for frequency conversion between baseband and RF; and
- a driver to receive the LO signals from the oscillator and to drive the LO signals from the transceiver module.
30. The transceiver module of claim 29, further comprising:
- a buffer to receive external LO signals and to provide buffered LO signals used by the first and second transceivers for frequency conversion between baseband and RF.
31. The transceiver module of claim 30, wherein the oscillator is disabled if the buffer is receiving the external LO signals.
32. The transceiver module of claim 29, further comprising:
- a phase locked loop (PLL) to control the oscillator to generate the LO signals at a predetermined frequency.
33. The transceiver module of claim 29 and fabricated on a single integrated circuit (IC) die.
34. A transceiver module, comprising:
- means for performing signal conditioning for radio frequency (RF) signals transmitted and received via at least two antennas;
- means for generating local oscillator (LO) signals used for frequency conversion between baseband and RF; and
- means for driving the LO signals from the transceiver module.
35. The transceiver module of claim 34, further comprising:
- means for buffering external LO signals and providing buffered LO signals used for frequency conversion between baseband and RF.
36. The transceiver module of claim 35, further comprising:
- means for disabling the means for generating the LO signals if the external LO signals are received.
Type: Application
Filed: Mar 7, 2005
Publication Date: Mar 23, 2006
Inventors: Xiangdon Zhang (Westford, MA), Jay Walton (Carlisle, MA)
Application Number: 11/075,005
International Classification: H04B 1/44 (20060101); H04B 1/38 (20060101);