WO2013039634A2

WO2013039634A2 - Monitoring antenna transmit operations

Info

Publication number: WO2013039634A2
Application number: PCT/US2012/050719
Authority: WO
Inventors: John S. RUCKI
Original assignee: Andrew Llc
Priority date: 2011-09-16
Filing date: 2012-08-14
Publication date: 2013-03-21
Also published as: WO2013039634A3

Abstract

An antenna system having n antenna sub-systems, each sub-system having a transceiver configured to a corresponding antenna element. Each transceiver has a transmit path, a receive path, a duplexer configured to interconnect the transmit and receive paths with the antenna element. Switch circuitry in the transceiver enables the sub-system to be configured in either (i) a normal operating mode in which an incoming signal from the antenna element is processed by the receive path to recover incoming data or (ii) a local transmitter monitoring mode in which the outgoing signal generated by the transmit path is tapped and fed to the receive path to characterize and possibly adjust the operations of the transmit path. In one embodiment, the switch circuitry enables outgoing signals from other antenna elements to be applied to the local receive path to support an external antenna monitoring mode.

Description

MONITORING ANTENNA TRANSMIT OPERATIONS

Cross-Reference to Related Applications

This application claims the benefit of the filing date of U.S. provisional application no. 61/535,747, filed on 09/16/11 as attorney docket no. 9457-329-PR, the teachings of which are incorporated herein by reference in their entirety.

BACKGROUND

Field of the Invention

The invention relates to antenna systems and, more specifically but not exclusively, to techniques for monitoring the operations of such antenna systems.

Description of the Related Art

This section introduces aspects that may help facilitate a better understanding of embodiments of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.

FIG. 1 shows a schematic block diagram of a conventional multi-element (e.g., active, phase- array) antenna system 100 (e.g., for use in a cellular telephone network as a base station antenna) that employs a dedicated monitoring receiver 110 to monitor the RF (radio frequency) transmissions from the antenna system, e.g., to regulate RF output power and/or control digital pre-distortion. As shown in FIG. 1, in addition to monitoring receiver 110, antenna system 100 has a digital signal processor (DSP) 120 and n antenna subsystems 130(1)-130(«), where each antenna subsystem 130 comprises a (e.g., dipole) antenna element 140 and a transceiver 150. Each transceiver 150 includes (i) a transmit path 160 for generating downlink signals for transmission (i.e., radiation) by the corresponding antenna element 140, (ii) a receive path 180 for processing uplink signals received at the corresponding antenna element 140, and (iii) a duplexer 152 for coupling the transmit and receive paths with the corresponding antenna element.

In the transmit (a.k.a. downlink or outgoing) direction, DSP 120 receives, processes, and distributes outgoing (e.g., baseband or intermediate frequency (IF)) digital data (DATA OUT) to the n transmit paths 160 of the n transceivers 150. In particular, the transmit path 160 of each transceiver 150 has a digital-to-analog converter (DAC) 162 that converts the outgoing digital data into an analog signal, an upconverter 164 that upconverts the analog signal to the RF domain, a power amplifier (PA) 166 that amplifies the RF signal, a coupler 168 that taps off a small portion of the amplified RF signal (described further below), and a circulator 170 that blocks signals from duplexer 152 from flowing any further into the transmit path. Duplexer 152 applies the outgoing, amplified RF signal from the transmit path for transmission by antenna element 140. In the receive (a.k.a. uplink or incoming) direction, the n receive paths 180 of the n transceivers 150 receive, process, and apply n incoming signals to DSP 120. In particular, the receive path 180 of each transceiver 150 has a low-noise amplifier (LNA) 182 that amplifies the incoming RF signal received from the corresponding antenna element 140 via duplexer 152, a downconverter 184 that converts the amplified RF signal into an IF or baseband domain, and an analog-to-digital converter (ADC) 196 that digitizes the downconverted signal into the digital domain for application to DSP 120, which processes the n digital signals received from the n receive paths 180 to generate incoming digital data (DATA IN).

Dedicated monitoring receiver 110 is provided to selectively monitor the transmit operations of individual transceivers 150. In particular, monitoring receiver 110 has an (nxl) configurable RF switch matrix (i.e., multiplexer) 112 that receives the n tapped outgoing RF signals from the n couplers 168 of the n transceivers 150 and outputs the tapped signal corresponding to the particular transceiver currently selected for monitoring. Downconverter 114 downconverts the selected RF signal, and ADC 116 digitizes the downconverted signal to apply a digital monitoring signal to DSP 120. Depending on the particular implementation, either DSP 120 or some processing element(s) downstream of DSP 120 process the monitoring signal to characterize and possibly adjust the transmit operations of the selected transceiver 150.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, features, and advantages of the invention will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawings in which like reference numerals identify similar or identical elements.

FIG. 1 shows a schematic block diagram of a conventional multi-element antenna system that employs a dedicated monitoring receiver to monitor the RF transmissions from the antenna system;

FIG. 2 shows a schematic block diagram of a transceiver of an antenna system according to one embodiment of the invention; and

FIG. 3 shows a schematic block diagram of a transceiver of an antenna system according to another embodiment of the invention. DETAILED DESCRIPTION

FIG. 2 shows a schematic block diagram of a transceiver 250 of an antenna system according to one embodiment of the invention. In theory, the antenna system can have any number n of instances of transceiver 250 (including only one instance) configured to n corresponding (e.g., dipole) antenna elements (not shown) and operating in parallel to transmit outgoing data as n downlink RF signals and receive incoming data as n uplink RF signals in a manner analogous to that of multi- element antenna system 100 of FIG. 1. Also not shown in FIG. 2 is a digital signal processor analogous to DSP 120 of FIG. 1.

As shown in FIG. 2, like each transceiver 150 of FIG. 1, transceiver 250 has a transmit path 260, a receive path 280, and a duplexer 252. Transmit path 260 comprises DAC 262, upconverter 264, amplification stage 266, coupler 268, and circulator 270, which operate analogous to the corresponding elements of transmit path 160 of FIG. 1. Similarly, receive path 280 comprises LNA 282, downconverter 284, and ADC 296, which operate analogous to the corresponding elements of receive path 180 of FIG. 1. Furthermore, duplexer 252 operates analogous to duplexer 152 of FIG. 1.

In addition and different from transceiver 150 of FIG. 1, transceiver 250 includes switches SW1-SW3, and downconverter 284 is implemented with a mixer 286 that downconverts the received RF signal to the IF domain, a variable attenuator 288 that attenuates the IF signal, an IF amplifier 290 that amplifies the IF signal, switches SW4 and SW5, and IF band-pass filters (BPF) 292 and 294. These elements enable transceiver 250 to be selectively configured in either (i) a normal operating mode in which receive path 280 functions analogous to receive path 180 of FIG. 1 or (ii) a local transmitter monitoring mode in which receive path 280 functions analogous to monitoring receiver 110 of FIG. 1.

In particular, for the normal operating mode, single-throw, single -pole switch SW3 is open, (2x1) switch SWl is configured to select the receiver (Rx) traffic from LNA 282, (2x1) switch SW2 is configured to select the receiver local oscillator (LO) signal (Rx_LO), (1x2) switch SW4 is configured to apply the amplified IF signal from IF amplifier 290 to IF BPF 294, and (2x1) switch SW5 is configured to apply the filtered output from BPF 294 to ADC 296.

On the other hand, for the local transmitter monitoring mode, switch SW3 is closed, (2x1) switch SWl is configured to select the tapped transmit (Tx) monitoring signal from switch SW3, (2x1) switch SW2 is configured to select the feedback LO signal (Fdbk_LO), (1x2) switch SW4 is configured to apply the amplified IF signal from IF amplifier 290 to IF BPF 292, and (2x1) switch SW5 is configured to apply the filtered output from BPF 292 to ADC 296.

The architecture of FIG. 2 enables the antenna system to support local transmit monitoring operations without requiring a dedicated monitoring receiver, such as monitoring receiver 110 of FIG. 1. When transceiver 250 is configured in the local transmitter monitoring mode, receive path 280 is not able to participate in the recovery of the incoming data (DATA IN). However, during those time periods, the remaining (n-l) receive paths 280 of the (n-l) other transceivers 250 can be configured to support that process. By sequentially configuring each of the n different individual transceivers 250 in the local transmitter monitoring mode, the entire antenna system can be monitored for

characterization and optional tuning of its RF transmit operations. Note that, in theory, it is possible simultaneously to configure any number (from 0 to n) of the n transceivers 250 in the local transmitter monitoring mode with the remaining transceivers 250 configured in the normal operating mode. In a typical communications application, the transmit frequency band is different from the receive frequency band. In that case, the transmitter LO signal (Tx_LO) applied to upconverter 264 will have a different frequency than the receiver LO signal (Rx_LO). Furthermore, depending on the particular implementation, the feedback LO signal (Fdbk_LO) may have a frequency that is the same as or different from that of the receiver LO signal (Rx_LO). In implementations in which the feedback and receiver LO signals are the same signal, switch SW2 can be omitted.

Switch SW3 is optional, but may be provided to increase the signal isolation between the transmit and receive paths during the normal operating mode.

Switches SW4 and SW5 and IF filters 292 and 294 are provided to enable the application of different filtering depending on which mode is selected. For example, in one implementation, an anti- alias filter used for IF BPF 292 during the local transmitter monitoring mode is wider than a relatively narrow filter used for IF BPF 294 during the normal operating mode. Wider filters may be needed for the local transmitter monitoring mode to pass transmit carriers and the wide-band distortion signals around those carriers, when the transmitters employ pre-distortion in which linearization is performed on spectral content beyond the transmit carriers. If such different filtering for different operating modes is not needed, then switches SW4 and SW5 and one of the IF filters may be omitted.

As shown in FIG. 2, the antenna system includes a controller 254 that controls the configurations of switches SW1 -SW5. In one embodiment, controller 254 is implemented by the antenna system's DSP (not shown) that is analogous to DSP 120 of FIG. 1.

FIG. 3 shows a schematic block diagram of a transceiver 350 of an antenna system according to another embodiment of the invention. Like the antenna system of FIG. 2, the antenna system of FIG. 3 can have any number n of instances of transceiver 350 (including only one instance) configured to n corresponding (e.g., dipole) antenna elements (not shown) and operating in parallel to transmit outgoing data as n downlink RF signals and receive incoming data as n uplink RF signals in a manner analogous to that of the antenna system of FIG. 2. Also not shown in FIG. 3 is a digital signal processor analogous to the DSP of the multi-element antenna system of FIG. 2.

Transceiver 350 is substantially identical to transceiver 250 of FIG. 2 except that (i) switch SW3' is a (2x1) switch instead of a single-throw, single-pole switch and (ii) transceiver 350 includes a second coupler 372 connected to switch SW3'. The configuration of FIG. 3 enables the antenna system to support a third operating mode (i.e., an external transmitter monitoring mode) in addition to modes analogous to the normal operating mode and the local transmitter monitoring mode of the antenna system of FIG. 2.

In particular, for the external transmitter monitoring mode, switch SW3' is configured to select the signal from second coupler 372. Second coupler 372 is configured to tap a portion of any RF signal received from the corresponding antenna element (not shown) via duplexer 352 and applied to circulator 370, which terminates that received RF signal, e.g., via a resistor (not shown) to ground. Under normal operating conditions, each antenna element in a multi-element array will pick up (i.e., be energized by, receive) the RF downlink signals radiated by the (n-l) other antenna elements in the array. Second coupler 372 enables a portion of each of those received RF downlink signals to be tapped prior to being terminated by circulator 370. With switch SW3' configured to select those tapped signals in the external transmitter monitoring mode, receive path 380 can be used to monitor the transmit operations of the (n-l) other (i.e., external) transmit paths 360.

Depending on the implementation, switches SW4 and SW5 could be configured to select the relatively wide, anti-alias BPF 392 during the external transmitter monitoring mode. If appropriate, a different switch arrangement could be provided along with a third BPF filter to enable that third BPF filter to be applied during the external transmitter monitoring mode.

Although the invention has been described in the context of antenna systems in which there is one antenna element for each transceiver, in alternative embodiments, there may be two or more antenna elements associated with specific transceivers.

The invention may be implemented as (analog, digital, or a hybrid of both analog and digital) circuit-based processes, including possible implementation as a single integrated circuit (such as an ASIC or an FPGA), a multi-chip module, a single card, or a multi-card circuit pack. As would be apparent to one skilled in the art, various functions of circuit elements may also be implemented as processing blocks in a software program. Such software may be employed in, for example, a digital signal processor, micro-controller, general-purpose computer, or other processor.

Also for purposes of this description, the terms "couple," "coupling," "coupled," "connect,"

"connecting," or "connected" refer to any manner known in the art or later developed in which energy is allowed to be transferred between two or more elements, and the interposition of one or more additional elements is contemplated, although not required. Conversely, the terms "directly coupled," "directly connected," etc., imply the absence of such additional elements.

Signals and corresponding nodes or ports may be referred to by the same name and are interchangeable for purposes here.

Embodiments of the invention can be manifest in the form of methods and apparatuses for practicing those methods. Embodiments of the invention can also be manifest in the form of program code embodied in tangible media, such as magnetic recording media, optical recording media, solid state memory, floppy diskettes, CD-ROMs, hard drives, or any other non-transitory machine -readable storage medium, wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. Embodiments of the invention can also be manifest in the form of program code, for example, stored in a non-transitory machine -readable storage medium including being loaded into and/or executed by a machine, wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. When implemented on a general-purpose processor, the program code segments combine with the processor to provide a unique device that operates analogously to specific logic circuits.

Any suitable processor-usable/readable or computer-usable/readable storage medium may be utilized. The storage medium may be (without limitation) an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device. A more- specific, non-exhaustive list of possible storage media include a magnetic coupler, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM) or Flash memory, a portable compact disc read-only memory (CD-ROM), an optical storage device, and a magnetic storage device. Note that the storage medium could even be paper or another suitable medium upon which the program is printed, since the program can be electronically captured via, for instance, optical scanning of the printing, then compiled, interpreted, or otherwise processed in a suitable manner including but not limited to optical character recognition, if necessary, and then stored in a processor or computer memory. In the context of this disclosure, a suitable storage medium may be any medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

The functions of the various elements shown in the figures, including any functional blocks labeled as "processors," may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term "processor" or "controller" should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), and non volatile storage. Other hardware, conventional and/or custom, may also be included. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context.

It should be appreciated by those of ordinary skill in the art that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the invention.

Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown. Embodiments of the invention can also be manifest in the form of a bitstream or other sequence of signal values stored in a non-transitory recording medium generated using a method and/or an apparatus of the invention.

Unless explicitly stated otherwise, each numerical value and range should be interpreted as being approximate as if the word "about" or "approximately" preceded the value of the value or range.

It will be further understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated in order to explain the nature of this invention may be made by those skilled in the art without departing from the scope of the invention as expressed in the following claims.

The use of figure numbers and/or figure reference labels in the claims is intended to identify one or more possible embodiments of the claimed subject matter in order to facilitate the

interpretation of the claims. Such use is not to be construed as necessarily limiting the scope of those claims to the embodiments shown in the corresponding figures.

It should be understood that the steps of the exemplary methods set forth herein are not necessarily required to be performed in the order described, and the order of the steps of such methods should be understood to be merely exemplary. Likewise, additional steps may be included in such methods, and certain steps may be omitted or combined, in methods consistent with various embodiments of the invention.

Although the elements in the following method claims, if any, are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term "implementation."

The embodiments covered by the claims in this application are limited to embodiments that (1) are enabled by this specification and (2) correspond to statutory subject matter. Non-enabled embodiments and embodiments that correspond to non-statutory subject matter are explicitly disclaimed even if they fall within the scope of the claims.

Claims

What is claimed is:

1. Apparatus having a first transceiver comprising:

a transmit (TX) path configured to generate an outgoing TX signal;

a receive (RX) path configured to receive an incoming RX signal; and

switch circuitry configured to selectively apply a portion of the outgoing TX signal to the RX path instead of the incoming RX signal. 2. The invention of claim 1, wherein:

the apparatus comprises a controller (e.g., 254) and a plurality of instances of the first transceiver; each instance of the first transceiver is connected to a corresponding antenna element of a multielement antenna array; and

the controller is configured to selectively control at least one instance of the first transceiver to apply the portion of the corresponding outgoing TX signal to the corresponding RX path, while each other instance of the first transceiver is configured to apply the corresponding incoming RX signal to the corresponding TX path.

3. The invention of claim 2, wherein the controller is configured to sequentially configure each different instance of the first transceiver to apply the portion of the corresponding outgoing TX signal to the corresponding RX path.

4. The invention of claim 1, wherein:

the apparatus comprises at least one other transceiver; and

the switch circuitry is further configured to selectively apply a portion of an outgoing TX signal received from the at least one other transceiver to the RX path of the first transceiver.

5. The invention of claim 1, wherein:

the first transceiver comprises a duplexer (e.g., 252) configured to (i) apply the outgoing TX signal received from the TX path to a first antenna element associated with the first transceiver and (ii) apply the incoming RX signal received from the first antenna element to the RX path;

the transmit path comprises:

a first coupler (e.g., 268) configured to tap off the portion of the outgoing TX signal; and a circulator (e.g., 270) configured between the first coupler and the duplexer to allow the outgoing TX signal to pass to the duplexer while blocking signals received from the duplexer; and the switch circuitry comprises a first (2x1) switch (SW1) configured to (a) receive (i) the portion of the outgoing TX signal tapped by the first coupler and (ii) the incoming RX signal from the duplexer and (b) selectively pass one of those two signals along the RX path. 6. The invention of claim 5, wherein:

the RX path comprises a mixer (e.g., 286) configured to downconvert the signal received from the first (2x1) switch; and

the switch circuitry further comprises a second (2x1) switch (SW2) configured to (a) receive (i) a feedback local oscillator (LO) signal (e.g., Fdbk_LO) associated with the portion of the outgoing TX signal and (ii) a receiver LO signal (e.g., Rx_LO) associated with the incoming RX signal and (b) selectively pass one of those two LO signals to the mixer for use in downconverting the signal received from the first (2x1) switch.

7. The invention of claim 5, wherein the RX path comprises first and second switched, parallel band-pass (BP) filters (e.g., 292, 294), wherein:

the RX path is configured to apply the first BP filter when the first (2x1) switch (e.g., SW1) is configured to pass the portion of the outgoing TX signal; and

the RX path is configured to apply the second BP filter when the first (2x1) switch (e.g., SW1) is configured to pass the incoming RX signal.

8. The invention of claim 7, wherein the first BP filter has a wider bandwidth than the second BP filter.

9. The invention of claim 5, wherein:

the apparatus comprises at least one other transceiver;

the TX path further comprises a second coupler (e.g., 372) connected between the circulator and the duplexer to tap off a portion of an other TX signal transmitted by the at least one other transceiver and received from the duplexer; and

the switch circuitry comprises a third (2x1) switch (e.g., SW3') connected to (a) receive (i) the portion of the outgoing TX signal from the first coupler and (ii) the portion of the other TX signal from the second coupler and (b) selectively pass one of those two TX signals to the RX path via the first (2x1) switch.

10. The invention of claim 5, wherein:

the switch circuitry comprises a single-throw, single -pole switch (e.g., SW3) connected to selectively pass the portion of the outgoing TX signal from the first coupler to the RX path via the first (2x1) switch. -lO- l l. The invention of claim 1, wherein:

the apparatus comprises a controller (e.g., 254) and a plurality of instances of the first transceiver; each instance of the first transceiver is connected to a corresponding antenna element of a multi- element antenna array via a duplexer (e.g., 252) configured to (i) apply the outgoing TX signal received from the corresponding TX path to the corresponding antenna element and (ii) apply the incoming RX signal received from the corresponding antenna element to the corresponding RX path; the controller is configured to selectively control at least one instance of the first transceiver to apply the portion of its corresponding outgoing TX signal to its corresponding RX path, while each other instance of the first transceiver is configured to apply its corresponding incoming RX signal to its corresponding TX path;

the transmit path comprises:

a first coupler (e.g., 268) configured to tap off the portion of the outgoing TX signal; and a circulator (e.g., 270) configured between the first coupler and the duplexer to allow the outgoing TX signal to pass to the duplexer while blocking signals received from the duplexer;

the switch circuitry comprises a first (2x1) switch (e.g., SW1) configured to (a) receive (i) the portion of the outgoing TX signal tapped by the first coupler and (ii) the incoming RX signal from the duplexer and (b) selectively pass one of those two signals along the RX path;

the RX path comprises a mixer (e.g., 286) configured to downconvert the signal received from the first (2x1) switch;

the switch circuitry further comprises a second (2x1) switch (SW2) configured to (a) receive (i) a feedback local oscillator (LO) signal (e.g., Fdbk_LO) associated with the portion of the outgoing TX signal and (ii) a receiver LO signal (e.g., Rx_LO) associated with the incoming RX signal and (b) selectively pass one of those two LO signals to the mixer for use in downconverting the signal received from the first (2x1) switch;

the RX path further comprises first and second switched, parallel band-pass (BP) filters (e.g., 292, 294), wherein:

the RX path is configured to apply the first BP filter (e.g., 292) when the first (2x1) switch is configured to pass the portion of the outgoing TX signal;

the RX path is configured to apply the second BP filter (e.g., 294) when the first (2x1) switch is configured to pass the incoming RX signal; and

the first BP filter has a wider bandwidth than the second BP filter.

12. The invention of claim 11, wherein:

the switch circuitry comprises a single-throw, single -pole switch (e.g., SW3) connected to selectively pass the portion of the outgoing TX signal from the first coupler to the RX path via the first (2x1) switch (e.g., SW1). -l l- lS. The invention of claim 11, wherein:

the TX path further comprises a second coupler (e.g., 372) connected between the circulator and the duplexer to tap off a portion of an other TX signal transmitted by at least one other instance of the first transceiver and received from the duplexer; and

the switch circuitry comprises a third (2x1) switch (e.g., SW3') connected to receive (i) the portion of the outgoing TX signal from the first coupler and (ii) the portion of the other TX signal from the second coupler and selectively pass one of those two TX signals to the RX path via the first (2x1) switch.