The presented technology generally relates to wireless communication, particularly to a radio frequency (RF) loop test method and apparatus for testing frequency division duplexing (FDD) transceiver in a radio communication system, and a communication node comprising the apparatus.
Radio frequency (RF) loop test is a method commonly used in radio systems, especially for frequency division duplexing (FDD) radio transceiver, where the transmitter (TX) and receiver (RX) are connected to a common antenna via a duplex filter as illustrated in
A simplified RF loop test implementation is shown in
A major problem with the existing solutions is that they can only test and monitor part of the transceiver, that is, the test loop fails in including the duplex filter and the connections between the duplex filter and the transmitter and receiver. The present RF loop test circuit always has two ports, one for TX coupling and one for RX coupling, it's impossible to cover duplex filter part where TX and RX share one port.
U.S. Pat. No. 7,062,235 provides a test method that permits not only to test the TX and RX, but also the cable connecting the TX and RX to the duplex filter and the duplex filter itself. But there are some limitations, for example the duplex filter attenuation at the out band test frequency should be consistent and manageable, TX and RX operational bandwidth shall be wide enough to cover the out band test frequency. These limitations heavily depend on the duplex frequency as illustrated in
Therefore, it is an object to solve at least one of the above-mentioned problems.
According to an aspect of the embodiments, there is provided a radio frequency (RF) loop test apparatus for testing Frequency Division Duplexing (FDD) transceiver in a radio communication system. The apparatus comprises a first directional coupling means and a mixer, the first directional coupling means is operably coupled with a duplex filter of the transceiver to receive, at a first port of the first directional coupling means, a test signal from a transmitter via the duplex filter; the mixer is operably coupled with the first directional coupling means on both sides to receive the test signal from a second port of the first directional coupling means, convert the frequency of the test signal from the transmitter to a frequency that is receivable by a receiver, and to output the converted test signal to the first directional coupling means; and the first directional coupling means is operably coupled to receive, at a third port of the first directional coupling means, the converted test signal from the mixer and output, at the first port of the first directional coupling means, the converted test signal to the receiver via the duplex filter.
According to an aspect of the embodiments, there is provided a communication node comprising a transmitter, a receiver, a duplex filter and a common antenna in a radio communication system, the duplex filter couples the input of the receiver and the output of the transmitter to the common antenna, and the communication node further comprises an RF loop test apparatus as described above.
According to another aspect of the embodiments, there is provided a method for testing FDD transceiver in a radio communication system, the method establishes a test loop between a transmitter and a receiver, where the test loop includes a duplex filter, a directional coupling means, a synthesizer and a mixer, the duplex filter and the directional coupling means provide two-way transmission path for the test loop; then transmits a test signal from the transmitter to the test loop via the duplex filter; converts the frequency of the test signal to a frequency that is receivable by the receiver; receives the converted test signal from the test loop via the duplex filter; and subsequently acquires a loop test result based on the received test signal.
In the embodiments, the loop test can provide a fully coverage of the function and performance of the radio transceiver. Meanwhile, the loop test is not constrained by the duplex frequency, in particular, the overlapping frequency point between RX and TX frequency band. Furthermore, since the test signal can be transmitted on the in band frequency used for the normal signal transmission and reception by the transceiver, the loop test accuracy and effectiveness is guaranteed.
The technology will now be described, by way of example, based on embodiments with reference to the accompanying drawings, wherein:
Embodiments herein will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments are shown. This embodiments herein may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like numbers refer to like elements throughout.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The present technology is described below with reference to block diagrams and/or flowchart illustrations of methods, apparatus (systems) and/or computer program products according to the present embodiments. It is understood that blocks of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, may be implemented by computer program instructions. These computer program instructions may be provided to a processor, controller or controlling circuit of a general purpose computer, special purpose computer, and/or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer and/or other programmable data processing apparatus, create means for implementing the functions/acts specified in the block diagrams and/or flowchart block or blocks.
Although specific terms in some specifications are used here, such as base station, it should be understand that the embodiments are not limited to those specific terms but may be applied to all similar entities, such as macro base station, femto base stations, NodeB and eNodeB
Embodiments herein will be described below with reference to the drawings.
As shown in
Here, the directional coupler 51 couples a defined amount of the electromagnetic power in a transmission line to a port enabling the signal to be used in another circuit. An essential feature of the directional coupler is that they only couple power flowing in one direction. Power entering the output port is not coupled to the input port. The directional coupler 51 is described in detail with reference to the
The mixer 52 is a nonlinear electrical circuit that creates new frequencies from two signals applied to it. In its most common application, two signals at frequencies f1 and f2 are applied to the mixer, and it produces new signals at the sum f1+f2 and difference f1−f2 of the original frequencies. Generally, the mixer is used to shift signals from one frequency range to another. Preferably, the mixer 52 is a broadband mixer. The synthesizer 53 acts as a source providing the mixer with the local oscillator signal that aids to create the signal with the new frequency.
Now returning to
In the loop test, the transmitter in the transceiver sends out a known test signal, which is lead through the duplex filter to the directional coupler 51. The direction coupler 51 receives the test signal at the port 1 (the directional coupler 51 works in mode 1 for the test signal), and the directional coupler 51 couples the test signal and feeds it to the mixer 52 through the port 4, where the frequency of test signal is converted from the transmission frequency to the reception frequency that is receivable by the receiver. Then the frequency-converted test signal is passed back to the directional coupler 51 via the port 2 (the directional coupler 51 works in mode 2 for frequency-converted test signal), and the frequency-converted test signal is directed to the duplex filter through the port 1 of the directional coupler 51, subsequently it proceeds to the receiver. In this way, the RF loop test signal goes through the transmitter, duplex filter and receiver in the transceiver.
During the loop test, the transmitter in the transceiver sends out a known test signal, which is lead through the duplex filter to the directional coupler 61. The direction coupler 61 receives the test signal at the port 1 (the directional coupler 61 works in mode 1 for the test signal), and the directional coupler 61 couples the test signal and feeds it to the mixer 62 through the port 2, where the frequency of test signal is converted from the transmission frequency to the reception frequency that is receivable by the receiver. Then the frequency-converted test signal is passed back to the directional coupler 61 via the port 4 (the directional coupler 61 works in mode 3 for frequency-converted test signal), and the frequency-converted test signal is directed to the duplex filter through the port 1 of the directional coupler 61, subsequently it proceeds to the receiver. In this way, the RF loop test signal also goes through the transmitter, duplex filter and receiver in the transceiver.
Due to a small number of elements used, the RF loop test apparatus can be designed to have smaller size and run on battery power. It's also easy to configure the apparatus just by setting the synthesizer frequency. This makes it suitable to replace expensive portable RF instrument for radio base station (RBS) site maintenance and radio unit trouble shooting. It can also be used for radio transceiver lab verification, function test and so on.
Alternatively, in the RF loop test apparatus, the directional coupler can be substituted with a power divider, such as a 3 DB power divider. As well known, power dividers and directional couplers are in all essentials the same class of device. Directional coupler tends to be used for 4-port devices that are loosely coupled, that is, a fraction of the input power appears at the coupled port. Power divider is used for devices with tight coupling (commonly, a power divider will provide half the input power at each of its output ports—a 3 dB divider) and is usually considered a 3-port device with isolated port terminated with a matching load. Hence, both the directional coupler and the power divider are applicable to the embodiment.
In the above embodiments, the RF loop test apparatus is implemented as a separate apparatus. Note that the RF loop test apparatus also can be implemented as a component within a communication node, such as transceiver. Alternatively, the RF loop test apparatus can be implemented as a circuit integrated within the duplex filter of the transceiver.
In the embodiment, the RF loop test is generally carried out when there is no traffic and the frequency channel is free for a certain time period. It should be appreciated that other suitable criteria to initiate the RF loop test can also be applied to the embodiment. For example, the RF loop test can be initiated upon request.
As illustrated in
The transmitter and receiver are connected to the duplex filter, which couples the input of the receiver and the output of the transmitter to the common antenna. As for the RF loop test apparatus, the directional coupler 74 is operably coupled between the duplex filter and the antenna, where the port 1 of the second directional coupler 74 is coupled to the antenna port of the duplex filter and the port 2 is coupled to the antenna. In normal operation, the input and output signals will be transmitted via the directional coupler 74. The directional coupler 71 in the apparatus is coupled to the port 4 of the directional coupler 74 by the port 1 of the directional coupler 71, and coupled to the mixer 72 with the port 4 in connection with the input of the mixer 72, and the port 2 in connection with the output of the mixer 72. Alternatively, the directional coupler 71 may be coupled to the mixer 72 with the port 2 in connection with the input of the mixer 72, and the port 4 in connection with the output of the mixer 72.
In the loop test, the transmitter sends out a known test signal, which is lead through the duplex filter to the directional coupler 74. The direction coupler 74 receives the test signal at the port 1 and directs the test signal to the directional coupler 71 through the port 4 of the directional coupler 74. The direction coupler 71 receives the test signal at the port 1 (the directional coupler 71 works in mode 1 for the test signal), then couples the test signal and feeds it to the mixer 72 through the port 4, where the frequency of test signal is converted from the transmission frequency to the reception frequency that is receivable by the receiver. Subsequently the frequency-converted test signal is passed back to the directional coupler 71 via the port 2 (the directional coupler 71 works in mode 2 for the frequency-converted test signal), and proceeds via the port 1 of the directional coupler 71 to the directional coupler 74, to the duplex filter and finally reaches the receiver. Thus, the transmitter, the duplex filter and the receiver are covered by the loop test.
Optionally, a switch 75, 76 is coupled between the directional coupler 71 and the mixer 72 on both sides of the mixer 72. The switch is closed only during the RF loop test, in other words, the test loop will be cut off during normal operation of the communication node. Since the RF loop test circuit is placed after the duplex filter and close to the antenna port, it is important to control the level of the spurious signal originating from the active components in the RF loop circuit, such that it will not violate the spurious emission required by the antenna port. Therefore, the switches 75, 76 are open during normal operation to isolate the active components in the RF loop circuit from the antenna port.
Optionally, an attenuator 77, 78 coupled between the directional coupler 71 and the mixer 72 on both sides of the mixer 72, which can be used to control the test signal level for both the test signal from the transmitter and the frequency-converted test signal by the mixer. The test signal level should be low enough to ensure that the signal attenuated in the test loop satisfies the antenna port spurious emission requirements, meanwhile, high enough to ensure that it remains above the sensitivity threshold of the receiver so as to be detected and analyzed by the receiver. Thus the test signal level should be within the range as below:
RX Sensitivity≦Test Signal Level≦Spurious Emission Requirements+Directional Coupler Directivity
Where RX Sensitivity refers to the sensitivity threshold of the receiver, and the Directional Coupler Directivity is the power at the “coupled” port divided by the power at the “isolated” port of the directional coupler 74. In decibels, the directivity is equal to the isolation minus the coupling.
Furthermore, the attenuator 77 coupled on the output side of the mixer 72 may also be used to attenuate the level of the test signal transmitted in the reverse direction, i.e. the direction from the port 2 of the directional coupler 71 to the mixer 72 output, such that the interference resulted from the signal transmission in the reverse direction can be alleviated. Alternatively, an isolator 79 can be set between the first coupler 71 and the mixer 72 on the output side of the mixer 72, which only allows the frequency-converted test signal transmission in one direction from the mixer 72 output to the first directional coupler 71 and blocks the signal transmitted in the direction from the first directional coupler 71 to the mixer 72 output.
Note that the attenuator 77, 78 can be fixed attenuator or variable attenuator. If the attenuator is variable attenuator, the attenuator can be set to the maximum attenuation when the loop test is not in operation, so as to further isolate the active components in the RF loop circuit from the antenna port along with the switch 75, 76.
Optionally, a bandpass filter 70 can be coupled between the directional coupler 71 and the mixer 72 on the output side of the mixer 72, such that unwanted frequency products generated by the mixer 72 can be removed. Ideally, the pass frequency band is the same as the reception frequency band.
As illustrated in
In step 901, the process establishes a test loop between a transmitter and a receiver in the communication node 700. The test loop may include a duplex filter, a directional coupler 71, a mixer 72, and the like. As illustrated, the duplex filter and the directional coupler 72 provide two-way transmission path for the test loop. Establishing the test loop may comprise programming the synthesizer to generate a local oscillator signal which will be provided to the mixer. The frequency of local oscillator signal is the frequency difference of the transmitting frequency from the transmitter and the reception frequency receivable by the receiver.
In step 902, a known test signal is sent out from the transmitter and lead through the duplex filter to the test loop.
Then, in step 903, the frequency of the test signal is converted to a reception frequency (receivable by the receiver) by the mixer 72 in the test loop. From there, the frequency-converted test signal proceeds via the duplex filter to the receiver.
Consequently, the frequency-converted test signal is detected and received by the receiver in step 904.
In step 905, the loop test result is acquired based on the frequency-converted test signal received in step 904. Specifically, the received test signal may firstly be checked to determine whether the signal level is within the expected range. If not, a RF loop alarm will arise, otherwise, the received test signal will be compared with the original test signal transmitted from the transmitter to obtain the information such as error vector magnitude (EVM) and bit error rate (BER), which may indicate the state of the transceiver. The way to obtain the EVM and BER is known in the art, which will not be described in more detail for brevity. It should be appreciated that the above manner to acquire the loop test result is described by way of example, and any other suitable manners can be applied to the embodiment.
Optionally, the method may include utilizing a switch (e.g. 75, 76) to cut off the test loop when the loop test is not in operation, such that the active components in the RF loop circuit is isolated from the antenna port. Accordingly, the test loop establishing step 901 may further comprise closing the switch in the test loop.
Optionally, the method may include utilizing the attenuator (e.g. 78) coupled on the input side of the mixer to control the level of the test signal to the mixer and utilizing the attenuator (e.g. 77) coupled on the output side of the mixer to control the level of frequency-converted test signal by the mixer. The attenuator 77 may be further used to attenuate the level of the test signal transmitted in the reverse direction, i.e. the direction from the first directional coupler 71 to the mixer 72 output, such that the interference resulted from the signal transmission in the reverse direction can be alleviated.
Note that the attenuators 77, 78 can be fixed attenuator or variable attenuator. If the attenuator is variable attenuator, the method may include setting the attenuators to the maximum attenuation when the loop test is not in operation, so as to further isolate the active components in the RF loop circuit from the antenna port. Moreover, when the attenuator is variable attenuator, the test loop establishing step 901 may further comprise setting the attenuators to the appropriate attenuation value.
Optionally, the method may include utilizing a bandpass filter (e.g. 70) coupled between the directional coupler 71 and the mixer 72 on the output side of the mixer 72, such that unwanted frequency products generated by the mixer 72 can be removed. Ideally, the pass frequency band is the same as the reception frequency band.
While the embodiments have been illustrated and described herein, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the present technology. In addition, many modifications may be made to adapt to a particular situation and the teaching herein without departing from its central scope. Therefore it is intended that the present embodiments not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the present technology, but that the present embodiments include all embodiments falling within the scope of the appended claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CN2012/001228 | 9/3/2012 | WO | 00 | 2/27/2015 |