WO2020151004A1

WO2020151004A1 - Method and apparatus for obtaining standing wave ratio

Info

Publication number: WO2020151004A1
Application number: PCT/CN2019/073209
Authority: WO
Inventors: Ang FENG; Yahui ZHAO
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2019-01-25
Filing date: 2019-01-25
Publication date: 2020-07-30

Abstract

The present invention generally relates to radio engineering and telecommunications. More particularly, the present invention relates to a method for obtaining standing wave ratio (SWR). The present invention also relates to an apparatus adapted for the same purpose. According to one aspect of the present invention, an apparatus for obtaining standing wave ratio (SWR) comprises: a reference circuit; a connecting unit configured to be selectively connected between a transmission line and a load, or between the transmission line and the reference circuit; a receiver unit connected to the connecting unit and configured to receive a first reflection signal from the load associated with a first radio frequency (RF) signal on the transmission line, or a second reflection signal from the reference circuit associated with a second RF signal on the transmission line; and a processing unit configured to receive the first reflection signal and the second reflection signal from the receiver unit and determine the SWR based on the first reflection signal and the second reflection signal.

Description

Method and Apparatus for Obtaining Standing Wave Ratio

TECHNICAL FIELD

The present invention generally relates to radio engineering and telecommunications. More particularly, the present invention relates to a method for obtaining standing wave ratio (SWR) . The present invention also relates to an apparatus adapted for the same purpose.

BACKGROUND

In radio engineering and telecommunications, SWR is a measure of impedance matching of loads to the characteristic impedance of a transmission line or waveguide. Checking the SWR is a standard procedure in a radio station, e.g., a base station (BS) in 5G systems featured with massive multiple-input multiple-output (MIMO) .

Figure 1 is a diagram illustrating voltage stand wave ratio (VSWR) measurement used in BSs. As shown in Fig. 1, a directional coupler 120 is connected between a transceiver 110 and an antenna 130.

Receivers

140A and 140B are connected to the coupler 120 for receiving an RF signal from the transceiver 110 (hereinafter also referred to as forward signal or reference signal) and a reflection signal from the antenna 130 (hereinafter also referred to as backward signal) , respectively. A processing unit 150 determines SWR on the basis of the forward and backward signals. In order to compensate unexpected leakage, calibration shall be performed in advance.

In the solution as shown in Fig. 1, accurate synchronization shall be kept between the receivers. However, this goal is not easy to achieve as it requires cautious design for both of local oscillators and serial links, otherwise, compensation will be invalid because of inaccurate calibration for leakage. Moreover, with the use of large scale antenna in MIMO, it is a challenge to integrate numerous components within compact size and achieve cost reduction at the same time.

SUMMARY

According to one aspect of the present invention, an apparatus for obtaining standing wave ratio (SWR) comprises:

a reference circuit;

a connecting unit configured to be selectively connected between a transmission line and a load, or between the transmission line and the reference circuit;

a receiver unit connected to the connecting unit and configured to receive a first reflection signal from the load associated with a first radio frequency (RF) signal on the transmission line, or a second reflection signal from the reference circuit associated with a second RF signal on the transmission line; and

a processing unit configured to receive the first reflection signal and the second reflection signal from the receiver unit and determine the SWR based on the first reflection signal and the second reflection signal.

According to another aspect of the present invention, a base station (BS) comprises:

a transceiver unit;

an antenna array;

a processing unit; and

a radio distribution network disposed between the transceiver unit and the antenna array, comprising:

a reference circuit;

a connecting unit configured to be selectively connected between

a transmission line and a load, or between the transmission line and the reference circuit,

wherein an air interference (AI) transceiver in the radio distribution network or a receiver in the transceiver unit is connected to the connecting unit and configured to receive a first reflection signal from the load associated with a first radio frequency (RF) signal on the transmission line, or a second reflection signal from the reference circuit associated with a second RF signal on the transmission line; and

wherein the processing unit is configured to receive the first reflection signal and the second reflection signal from the AI transceiver or the receiver and determine the SWR based on the first reflection signal and the second reflection signal.

According to another aspect of the present invention, a method for obtaining standing wave ratio (SWR) comprises:

obtaining a first reflection signal from the load associated with a first radio frequency (RF) signal on the transmission line and a second reflection signal from the reference circuit associated with a second RF signal on the transmission line by using a receiver unit; and

determining the SWR based on the first reflection signal and the second reflection signal.

In one or more embodiments of the present invention, two reflection signals are received by one single receiver during their respective time periods and thus it has no need to consider synchronization in two-receivers configuration. Moreover, an air interference transceiver (AI TRX) or a receiver (RX) may be reused as the single receiver for the SWR measurement. This is advantageous to reducing cost and simplifying structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of the invention would be apparent from the following more particular description of preferred embodiments as illustrated in the accompanying drawings in which:

Figure 1 is a diagram illustrating voltage stand wave ratio (VSWR) measurement used in BSs.

Fig. 2 is a block diagram illustrating a base station according to one or more embodiments of the present invention.

Fig. 3 is a block diagram illustrating an apparatus for obtaining SWR according to one exemplary embodiment of the present invention.

Fig. 4 is a block diagram illustrating an apparatus for obtaining SWR according to another exemplary embodiment of the present invention.

Fig. 5 is a block diagram illustrating an apparatus for obtaining SWR according to another exemplary embodiment of the present invention.

Fig. 6 is a flow diagram illustrating a process for obtaining SWR according to one embodiment of the present invention.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as a process; an apparatus; a system; a composition of matter; a computer program product embodied on a computer readable storage medium; and/or a processor, such as a processor configured to execute instructions stored on and/or provided by a memory coupled to the processor. In this specification, these implementations, or any other form that the invention may take, may be referred to as techniques. In general, the order of the steps of disclosed processes may be altered within the scope of the invention. Unless stated otherwise, a component such as a processor or a memory described as being configured to perform a task may be implemented as a general component that is temporarily configured to perform the task at a given time or a specific component that is manufactured to perform the task. As used herein, the term "processor" refers to one or more devices, circuits, and/or processing cores configured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention is provided below along with accompanying figures that illustrate the principles of the invention. The invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. These details are provided for the purpose of example and the invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured.

As used herein, the term "antenna element" refers to a subset of an antenna array, consisting of a single radiating element or a group of radiating elements.

As used herein, the term "transceiver unit" refers to an active unit consisting of transmitter and/or receiver which transmits and/or receives radio signals.

As used herein, the term "receiver unit" or "receiver" refers to an active unit which receives radio signals.

As used herein, the term "transmission line" refers to a cable or other structure for connecting transmitters or receivers with their antennas.

Fig. 2 is a block diagram illustrating a base station according to one or more embodiments of the present invention. As shown in Fig. 2, a base station 20 comprises a transceiver unit 210, an antenna array 220 connected to the transceiver unit via a transmission line, a radio distribution network 230 disposed between the transceiver unit 210 and the antenna array 220, and a processing unit 240 communicatively coupled to the transceiver unit 210 and the radio distribution network 230.

With reference to Fig. 2, the radio distribution network 230 comprises a reference circuit 231 and a connecting unit 232. The connecting unit 232 is configured to be selectively connected between the transceiver unit 210 and one of antenna elements in the antenna array 220, or between the transceiver unit 210 and the reference circuit 231, e.g., under the control of the processing unit 240.

In the BS as shown in Fig. 2, the component of a standing wave on the transmission line consists of a forward wave from the transceiver unit 210 and a reflection wave from either an antenna element of the antenna array 220 or the reference circuit 231 depending on the connective state of the connecting unit 232. In one or more embodiments of the present invention, two reflection signals are received by one single receiver during their respective time periods. Specifically, the single receiver is configured to separately receive one or more reflection signals from the reference circuit 231 (hereinafter also referred to as first reflection signal) and a reflection signal from a load, e.g., an antenna element or a radiating element of the antenna array 220 (hereinafter also referred to as second reflection signal) . In other words, the first and second reflection signals are not received at the same time. Then, the processing unit 240 determines SWR based on the first and second reflection signals. With the above single-receiver configuration, it has no need to consider synchronization in two-receivers configuration.

In one or more embodiments of the present invention, preferably, an air interference transceiver (AI TRX) in the radio distribution network 230 or a receiver (RX) in the transceiver unit 210 is reused as the single receiver. Since the AI TRX and RX are essential components for an active antenna system (AAS) , the sharing is advantageous to reducing cost and simplifying structure.

With reference to Fig. 3, the apparatus 310 comprises a reference circuit 311 including reference impedances Z ⁽¹⁾ _L and Z ⁽¹⁾ ₀, a connecting unit 312 including a circulator 3121, switches SW1 and SW2, a coupler 3122 and a signal combiner 3123, a receiver unit 313, e.g., AI transceiver and a processing unit 314, e.g., digital ASIC/FPGA, for determining SWR.

The apparatus 310 is disposed between an transceiver unit 320 and an antenna elements, e.g., denoted as 330, in an antenna array. The transceiver unit 320 comprises a transmitter 321 and a receiver 322, which are under control of the processing unit 314. In the present embodiment, preferably, the apparatus 310 shares the AI transceiver and the digital ASIC/FPGA with other unit (s) or functionality in a BS. Alternatively, it can use a receiver or a processing unit dedicated to SWR measurement instead.

As show in Fig. 3, the transmitter 321 is coupled to a first port P11 of the coupler 3122 via the circulator 3121 and a filter 340 and to the reference impedance Z ⁽¹⁾ ₀ or the receiver 322 via the circulator 3121 and the switch SW2. On the other hand, a second port P12 of the coupler 3122 is coupled to the antenna element 330 or the reference impedance Z ⁽¹⁾ _L via the switch SW1, and a third port P13 and a fourth pot P14 are coupled to the AI transceiver 314 via the signal combiner 3123.

In the present embodiment, a calibration is performed when the transmitter 321 is coupled to the reference impedance Z ⁽¹⁾ ₀ via the switch SW2 and the port 12 of the coupler 3122 is coupled to the reference impedance Z ⁽¹⁾ _L via the switch SW1. During the calibration, a calibration measurement or a first measurement is carried out by receiving at the AI transceiver 313 a first reflection signal from the reference impedance Z ⁽¹⁾ _L and an RF signal from the filter 340 or the transmitter 321. Preferably, the measurement is made over a frequency range so as to reduce time. Additional benefits include availability of group delay and initial phase and compensation for timing error.

In case SWR is frequency-dependent, the first measurement can be represented as follows:

where M ⁽¹⁾ _1, k represents the first measurement at frequency k, S ⁽¹⁾ _31, k represents an S-parameter from the port P13 to the port P11 at the frequency k, S ⁽¹⁾ _32, k represents an S-parameter from the port P13 to the port P12 at the frequency k, S ⁽¹⁾ _41, k represents an S-parameter from the port P14 to the port P11 at the frequency k, S ⁽¹⁾ _42, k represents an S-parameter from the port P14 to the port P12 at the frequency k, Z ⁽¹⁾ _L, k represents the impedance of Z ⁽¹⁾ _L at the frequency k, and Z ⁽¹⁾ ₀ represents the impedance of Z ⁽¹⁾ ₀ or the impedance to the ground for the transmission line, θ ⁽¹⁾ _TX, k represents the phase of a RF signal transmitted at the transmitter 321, andθ ⁽¹⁾ _RX, k represents the phase of a RF signal received at the AI transceiver or receiver unit 313.

On the other hand, for carrying out an SWR measurement or a second measurement, the transmitter 321 is coupled to the reference impedance Z ⁽¹⁾ ₀ via the switch SW2 and the port P12 of the coupler 3122 is coupled to the antenna element 330 via the switch SW1. The AI transceiver 313 receives a first reflection signal from the antenna element 330 and an RF signal from the filter 340 or the transmitter 321. Since SWR is frequency-dependent, the second measurement or the SWR measurement can be represented as follows:

where M ⁽¹⁾ _2, k represents the second measurement at the frequency k, S ⁽¹⁾ _31, k represents an S-parameter from the port P13 to the port P11 at the frequency k, S ⁽¹⁾ _32, k represents an S-parameter from the port P13 to the port P12 at the frequency k, S ⁽¹⁾ _41, k represents an S-parameter from the port P14 to the port P11 at the frequency k, S ⁽¹⁾ _42, k represents an S-parameter from the port P14 to the port P12 at the frequency k, Γ ⁽¹⁾ _R, k represents a reflection factor from the antenna element 330, θ ⁽¹⁾ _TX, k represents the phase of a RF signal transmitted at the transmitter 321, and θ ⁽¹⁾ _RX, k represents the phase of a RF signal received at the AI transceiver or receiver unit 313.

The phases θ ⁽¹⁾ _TX, k andθ ⁽¹⁾ _RX, k can be cancelled by combining equations (1) and (3) into the following equation:

Furthermore, equation (4) can be rewritten as follows:

Thus, SWR at the frequency k can be determined as follows:

In the present embodiment, the processing unit 314 is connected to the AI receiver and is configured to determine SWR from the first measurement and the second measurement in the manner as described above.

In equation (5) , it assumes that the phase and the amplitude of the RF signal from the transmitter 321 and the RF signal received at the receiver unit 313 are unchanged or fixed between the calibration measurement and the SWR measurement. However, this is not compulsory. Indeed, a similar equation can be obtained as long as the RF signals from the transmitter 321 during the calibration measurement and the SWR measurement have a predetermined relationship in phase and amplitude, and the reflection signals during the calibration measurement and the SWR measurement have a predetermined relationship in phase and amplitude.

The apparatus 410 comprises a reference circuit 411 including reference impedances Z ⁽²⁾ _L, Z ⁽²⁾ _L' and Z ⁽²⁾ ₀, a connecting unit 412 including a circulator 4121 and switches SW3, SW4, SW5, a receiver unit and a processing unit 413, e.g., digital ASIC/FPGA, for determining SWR.

The apparatus 410 is disposed between a transceiver unit 420 and an antenna elements, e.g., denoted as 430, in an antenna array. The transceiver unit 420 comprises a transmitter 421 and a receiver 422, which are under control of the processing unit 413. In the present embodiment, preferably, the apparatus 410 and the transceiver unit 420 share the receiver 422 and the digital ASIC/FPGA 413. Alternatively, a dedicated receiver or a dedicated processing unit is available for SWR measurement.

As show in Fig. 4, the transmitter 421 is connected to a first port P21 of the circulator 4121. A second port P22 and a third port P23 of the circulator 4121 are connected to the switches SW4 and SW3, respectively. The port P23 can be coupled to the receiver 422 or the reference impedance Z ⁽²⁾ ₀ via the switch SW3. The port P22 can be coupled to the reference impedance Z ⁽²⁾ _L or a filter 440 via the switch SW4. In turn, the filter 440 can be coupled to the antenna element 430 or the reference impedance Z ⁽²⁾ _L' via the switch SW5.

In the present embodiment, two-step calibration is carried out. During a first calibration, the port P23 is coupled to the receiver 422 via the switch SW3, and the port P22 or the transmitter 421 is coupled to the reference impedance Z ⁽²⁾ _L via the switch SW4. A reflection signal from the reference impedance Z ⁽²⁾ _L is received at the receiver 422. Meanwhile, an RF signal from the transmitter 421 is known for the processing unit 413. In case SWR is frequency-dependent, a measurement for the first calibration can be represented as follows:

where M ⁽²⁾ _1, k represents the measurement for the first calibration at frequency k, S ⁽²⁾ _31, k represents an S-parameter from the port P23 to the port P21 at the frequency k, S ⁽²⁾ _21, k represents an S-parameter from the port P22 to the port P21 at the frequency k, S ⁽²⁾ _32, k represents an S-parameter from the port P23 to the port P22 at the frequency k, Z ⁽²⁾ _L, k represents the impedance of Z ⁽²⁾ _L at the frequency k, and Z ⁽²⁾ ₀ represents the impedance of Z ⁽²⁾ ₀ or the impedance to the ground for the transmission line, θ ⁽²⁾ _TX, k represents the phase of a RF signal transmitted at the transmitter 421, andθ ⁽²⁾ _RX, k represents the phase of a RF signal received at the receiver 422.

During a second calibration, the port P23 is coupled to the receiver 422 via the switch SW3, and the transmitter 421 is coupled to the reference impedance Z ⁽²⁾ _L' via the switch SW4, the filter 440 and the switch SW5. A reflection signal from the reference impedance Z ⁽²⁾ _L' is received at the receiver 422 and an RF signal from the transmitter 421 is known to the processing unit 413. Thus, a measurement for the second calibration can be represented as follows:

where M ⁽²⁾ _2, k represents the measurement for the second calibration at frequency k, S ⁽²⁾ _31, k represents an S-parameter from the port P23 to the port P21 at the frequency k, S ⁽²⁾ _21, k represents an S-parameter from the port P22 to the port P21 at the frequency k, S ⁽²⁾ _42, k represents an S-parameter from a port P24 of the filter 440, which connects to the switch SW5, to the port P22 at the frequency k, S ⁽²⁾ _24, k represents an S-parameter from the port P22 to the port P24 at the frequency k, S ⁽²⁾ _32, k represents an S-parameter from the port P23 to the port P22 at the frequency k, Z ⁽²⁾ _L', k represents the impedance of Z ⁽²⁾ _L’ at the frequency k, and Z ⁽²⁾ ₀ represents the impedance of Z ⁽²⁾ ₀ or the impedance to the ground for the transmission line, θ ⁽²⁾ _TX, k represents the phase of a RF signal transmitted at the transmitter 421, andθ ⁽²⁾ _RX, k represents the phase of a RF signal received at the receiver 422.

On the other hand, for carrying out an SWR measurement, the port P23 is coupled to the receiver 422 via the switch SW3, and the transmitter 421 is coupled to the antenna element 430 via the switch SW4, the filter 440 and the switch SW5. A reflection signal from the antenna element 430 is received at the receiver 422 while an RF signal from the transmitter 421 is known to the processing unit 413. Thus, the SWR measurement can be represented as follows:

where M ⁽²⁾ _3, k represents the SWR measurement at the frequency k, S ⁽²⁾ _31, k represents an S-parameter from the port P23 to the port P21 at the frequency k, S ⁽²⁾ _21, k represents an S-parameter from the port P22 to the port P21 at the frequency k, S ⁽²⁾ _42, k represents an S-parameter from a port P24 of the filter 440, which connects to the switch SW5, to the port P22 at the frequency k, S ⁽²⁾ _24, k represents an S-parameter from the port P22 to the port P24 at the frequency k, S ⁽²⁾ _32, k represents an S-parameter from the port P23 to the port P22 at the frequency k, Γ ⁽²⁾ _R, k represents a reflection factor from the antenna element 430, θ ⁽²⁾ _TX, k represents the phase of a RF signal transmitted at the transmitter 421, and θ ⁽²⁾ _RX, k represents the phase of a RF signal received at the receiver 422.

Assuming that the phase and amplitude of the RF signals from the transmitter 521 and the receiver 522 are unchanged or fixed during the calibration and SWR measurement, the following equation is obtained by combining equations (7) and (9) :

Likewise, assuming that the phase and amplitude of the RF signals from the transmitter 521 and the receiver 522 are unchanged or fixed during the calibration and SWR measurement, the following equation is obtained by combining equations (7) and (11) :

However, the assumption is not compulsory. Indeed, the equations in similar form can be obtained as long as the RF signals from the transmitter 421 during the calibration measurement and the SWR measurement have a predetermined relationship in phase and amplitude, and the reflection signals during the calibration measurement and the SWR measurement have a predetermined relationship in phase and amplitude.

Furthermore, equations (12) and (13) can be respectively rewritten as follows:

Thus, the reflection factorΓ ⁽²⁾ _R, k can be represented as follows:

where

Note that when determining the reflection factor as defined by equation (16) , it has no need to consider the S-parameters S ⁽³⁾ _42, k and S ⁽³⁾ _42, k, which are difficult to obtain in production.

And SWR at the frequency k can be determined as follows from the following equation:

In the present embodiment, the processing unit 413 is connected to the receiver 422 and is configured to determine SWR from the calibration measurement and the SWR measurement in the manner as described above.

The apparatus 510 comprises a reference circuit 511 including reference impedances Z ⁽³⁾ _L and Z ⁽³⁾ ₀, a connecting unit 512 including a circulator 5121 and switches SW6, SW7, a receiver unit and a processing unit 513, e.g., digital ASIC/FPGA, for determining SWR.

The apparatus 510 is disposed between a transceiver unit 520 and an antenna elements, e.g., denoted as 530, in an antenna array. The transceiver unit 520 comprises a transmitter 521 and a receiver 522, which are under control of the processing unit 513. In the present embodiment, preferably, the apparatus 510 and the transceiver unit 520 share the receiver 522 and the digital ASIC/FPGA 513. Alternatively, a dedicated receiver or a dedicated processing unit is available for SWR measurement.

As show in Fig. 5, the transmitter 521 is connected to a first port P31 of the circulator 5121. A third port P33 of the circulator 5121 is connected to the switches SW6 and a second port P32 of the circulator 5121 is coupled to the switch SW7 via a filter 540. Thus, the port P32 can be coupled to the reference impedance Z ⁽³⁾ _L or the antenna element 530 via the switch SW7.

In the present embodiment, a single-step calibration is carried out. During calibration, the port P33 is coupled to the receiver 522 via the switch SW6, and the port P32 or the transmitter 521 is coupled to the reference impedance Z ⁽³⁾ _L via the filter 540 and the switch SW7. A reflection signal from the reference impedance Z ⁽³⁾ _L is received at the receiver 522. Meanwhile, an RF signal from the transmitter 521 is known for the processing unit 513. In case SWR is frequency-dependent, a measurement for the calibration can be represented as follows:

where M ⁽³⁾ _1, k represents the measurement for the calibration at frequency k, S ⁽³⁾ _31, k represents an S-parameter from the port P33 to the port P31 at the frequency k, S ⁽³⁾ _21, k represents an S-parameter from the port P32 to the port P31 at the frequency k, S ⁽³⁾ _32, k represents an S-parameter from the port P33 to the port P32 at the frequency k, Z ⁽³⁾ _L, k represents the impedance of Z ⁽³⁾ _L at the frequency k, and Z ⁽³⁾ ₀ represents the impedance of Z ⁽³⁾ ₀ or the impedance to the ground for the transmission line, θ ⁽³⁾ _TX, k represents the phase of a RF signal transmitted at the transmitter 521, and θ ⁽³⁾ _RX, k represents the phase of a RF signal received at the receiver 522.

On the other hand, for carrying out an SWR measurement, the port P33 is coupled to the receiver 522 via the switch SW6, and the transmitter 521 is coupled to the antenna element 530 via the filter 540 and the switch SW7. A reflection signal from the antenna element 530 is received at the receiver 522 while an RF signal from the transmitter 521 is known to the processing unit 513. Thus, the SWR measurement can be represented as follows:

where M ⁽³⁾ _2, k represents the SWR measurement at the frequency k, S ⁽³⁾ _31, k represents an S-parameter from the port P33 to the port P31 at the frequency k, S ⁽³⁾ _21, k represents an S-parameter from the port P32 to the port P31 at the frequency k, S ⁽³⁾ _42, k represents an S-parameter from a port P34 of the filter 440, which connects to the switch SW7, to the port P32 at the frequency k, S ⁽³⁾ _24, k represents an S-parameter from the port P32 to the port P34 at the frequency k, S ⁽³⁾ _32, k represents an S-parameter from the port P33 to the port P32 at the frequency k, Γ ⁽³⁾ _R, k represents a reflection factor from the antenna element 530, θ ⁽³⁾ _TX, k represents the phase of a RF signal transmitted at the transmitter 521, and θ ⁽³⁾ _RX, k represents the phase of a RF signal received at the receiver 522.

Assuming the phase and amplitude of the RF signals from the transmitter 521 and the receiver 522 are unchanged or fixed during the calibration and SWR measurement. Thus, the following equation is obtained by combining equations (19) and (21) :

Moreover, equation (22) can be rewritten as follows:

The above assumption is not compulsory. Indeed, a similar equation can be obtained as long as the RF signals from the transmitter 521 during the calibration measurement and the SWR measurement have a predetermined relationship in phase and amplitude, and the reflection signals during the calibration measurement and the SWR measurement have a predetermined relationship in phase and amplitude.

From equation (23) , in determining the reflection factor, it has no need to consider the S-parameters S ⁽³⁾ _42, k and S ⁽³⁾ _42, k, which are difficult to obtain in production.

Thus, SWR at the frequency k can be determined as follows:

In the present embodiment, the processing unit 513 is connected to the receiver 522 and is configured to determine SWR from the calibration measurement and the SWR measurement in the manner as described above.

In the embodiments as described with reference to Figs. 3-5, only the S-parameters of the coupler or the circulator are used in determining SWR. Generally, the S-parameters are available from component vendors. There is a concern on the performance difference between fixture and on board. To mitigate the performance gap, components vendor may develops the fixture based on a PCB layout actually used in a product, assemble an isolator with the fixture and then perform measurement. In this way, the S-parameters for the fixture is aligned with the on-board performance and could be taken as a reference for compensation.

Furthermore, compared with those conventional solutions for SWR measurement, no calibration step needs in production, and thus the cost for production further decreases.

For illustrative purpose, the following description is made with reference to the apparatus as shown in Figs. 2-5. However, one skilled artisan in the art would recognize that the present invention is not limited to any specific apparatus.

As shown in Fig. 6, at step S610, a processing unit, e.g., the

unit

240, 315, 413 or 513, obtains a reflection signal from a reference circuit, e.g., the

circuit

231, 311, 411 or 511, for calibration or performs a calibration measurement by using a receiver unit. As described above, the receiver unit may be an AI transceiver, a receiver in a transceiver unit or a dedicated receiver.

Then, at step S620, the processing unit obtains a reflection signal from a load, e.g., the

antenna element

330, 430 or 530, by using the receiver unit.

At step S630, the processing unit determines SWR based on the reflection signal from the reference circuit and the reflection signal from the load. For illustrative purpose, the specific examples of determining the SWR, which are described above with reference to Figs. 2-5, are applicable.

It should be noted that the aforesaid embodiments are illustrative of this invention instead of restricting this invention, substitute embodiments may be designed by those skilled in the art without departing from the scope of the claims enclosed. The wordings such as “include” , “including” , “comprise” and “comprising” do not exclude elements or steps which are present but not listed in the description and the claims. It also shall be noted that as used herein and in the appended claims, the singular forms “a” , “an” , and “the” may include plural referents unless the context clearly dictates otherwise. This invention can be achieved by means of hardware including several different elements or by means of a suitably programmed computer. In the unit claims that list several means, several ones among these means can be specifically embodied in the same hardware item. The use of such words as first, second, third does not represent any order, which can be simply explained as names. While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any implementation or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular implementations. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The above described embodiments are given for describing rather than limiting the disclosure, and it is to be understood that modifications and variations may be resorted to without departing from the scope of the disclosure as those skilled in the art readily understand. Such modifications and variations are considered to be within the scope of the disclosure and the appended claims. The protection scope of the disclosure is defined by the accompanying claims.

Claims

An apparatus for obtaining standing wave ratio (SWR) , be characterized in comprising:

a reference circuit;

a connecting unit configured to be selectively connected between a transmission line and a load, or between the transmission line and the reference circuit;

a receiver unit connected to the connecting unit and configured to receive a first reflection signal from the load associated with a first radio frequency (RF) signal on the transmission line, or a second reflection signal from the reference circuit associated with a second RF signal on the transmission line; and

a processing unit configured to receive the first reflection signal and the second reflection signal from the receiver unit and determine the SWR based on the first reflection signal and the second reflection signal.
The apparatus according to claim 1, wherein the first RF signal and the second RF signal have a predetermined relationship in phase and amplitude, and the first reflection signal and the second reflection signal have a predetermined relationship in phase and amplitude.
The apparatus according to claim 1, wherein the first reflection signal and the second reflection signal have the same frequency.
The apparatus according to claim 1, wherein the load is an antenna element and the receiver unit is an air interference (AI) transceiver.
The apparatus according to claim 4, wherein the connecting unit comprises a coupler and a first switch, a first port of the coupler is coupled to the transmission line, a second port of the coupler is configured to selectively coupled to the antenna element or a reference impedance of the reference circuit via the first switch, and a third port and a fourth port of the coupler are coupled to the AI transceiver.
The apparatus according to claim 1, wherein the load is an antenna element and the receiver unit is a receiver in a transceiver unit of a base station (BS) .
The apparatus according to claim 6, wherein the connecting unit comprises a circulator, a second switch and a third switch, a first port of the circulator is connected to the transmission line, a second port of the circulator is configured to selectively coupled to one of the following: a first reference impedance of the reference circuit via the second switch, the antenna element via the second switch and the third switch, or a second reference impedance of the reference circuit via the second switch and the third switch, and a third port of the circulator is coupled to the receiver.
The apparatus according to claim 6, wherein the connecting unit comprises a circulator and a fourth switch, a first port of the circulator is coupled to the transmission line, a second port of the circulator is configured to selectively coupled to a third reference impedance of the reference circuit via the fourth switch, or the antenna element via the fourth switch, and a third port of the circulator is coupled to the receiver.
A base station (BS) , be characterized in comprising:

a transceiver unit;

an antenna array;

a processing unit; and

a radio distribution network disposed between the transceiver unit and the antenna array, comprising:

a reference circuit;

a connecting unit configured to be selectively connected between a transmission line and a load, or between the transmission line and the reference circuit,

wherein an air interference (AI) transceiver in the radio distribution network or a receiver in the transceiver unit is connected to the connecting unit and configured to receive a first reflection signal from the load associated with a first radio frequency (RF) signal on the transmission line, or a second reflection signal from the reference circuit associated with a second RF signal on the transmission line; and

wherein the processing unit is configured to receive the first reflection signal and the second reflection signal from the AI transceiver or the receiver and determine the SWR based on the first reflection signal and the second reflection signal.
The BS according to claim 9, wherein the first RF signal and the second RF signal have a predetermined relationship in phase and amplitude, and the first reflection signal and the second reflection signal have a predetermined relationship in phase and amplitude.
The BS according to claim 9, wherein the first reflection signal and the second reflection signal have the same frequency.
The BS according to claim 9, wherein the connecting unit comprises a coupler and a first switch, a first port of the coupler is coupled to the transmission line, a second port of the coupler is configured to selectively coupled to the antenna element or a reference impedance of the reference circuit via the first switch, and a third port and a fourth port of the coupler are coupled to the AI transceiver.
The BS according to claim 9, wherein the connecting unit comprises a circulator, a second switch and a third switch, a first port of the circulator is connected to the transmission line, a second port of the circulator is configured to selectively coupled to one of the following: a first reference impedance of the reference circuit via the second switch, the antenna element via the second switch and the third switch, or a second reference impedance of the reference circuit via the second switch and the third switch, and a third port of the circulator is coupled to the receiver.
The BS according to claim 9, wherein the connecting unit comprises a circulator and a fourth switch, a first port of the circulator is connected to the transmission line, a second port of the circulator is configured to selectively coupled to a third reference impedance of the reference circuit via the fourth switch, or the antenna element via the fourth switch, and a third port of the circulator is coupled to the receiver.
A method for obtaining standing wave ratio (SWR) , be characterized in comprising:

obtaining a first reflection signal from the load associated with a first radio frequency (RF) signal on the transmission line and a second reflection signal from the reference circuit associated with a second RF signal on the transmission line by using a receiver unit; and

determining the SWR based on the first reflection signal and the second reflection signal.
The method according to claim 15, wherein the receiver unit is connected to a connecting unit configured to be selectively connected between the transmission line and the load, or between the transmission line and the reference circuit.
The method according to claim 16, wherein the first RF signal and the second RF signal have a predetermined relationship in phase and amplitude, and the first reflection signal and the second reflection signal have a predetermined relationship in phase and amplitude.
The method according to claim 16, wherein the first reflection signal and the second reflection signal have the same frequency.
The method according to claim 16, wherein the load is an antenna element and the receiver unit is an air interference (AI) transceiver.
The method according to claim 19, wherein the connecting unit comprises a coupler and a first switch, a first port of the coupler is coupled to the transmission line, a second port of the coupler is configured to selectively coupled to the antenna element or a reference impedance of the reference circuit via the first switch, and a third port and a fourth port of the coupler are coupled to the AI transceiver.
The method according to claim 20, wherein the SWR is determined as:

M ⁽¹⁾ _1, k represents a first measurement at the frequency k where the second port is coupled to the reference impedance of the reference circuit via the first switch, M ⁽¹⁾ _2, k represents a second measurement at the frequency k where the second port is coupled to the antenna element via the first switch, S ⁽¹⁾ _31, k represents a S-parameter from the third port to the first port at the frequency k, S ⁽¹⁾ _32, k represents a S-parameter from the third port to the second port at the frequency k, S ⁽¹⁾ _41, k represents a S-parameter from the fourth port to the first port at the frequency k, S ⁽¹⁾ _42, k represents a S-parameter from the fourth port to the first port at the frequency k, Z ⁽¹⁾ _L, k represents the reference impedance of the reference circuit at the frequency k, and Z ⁽¹⁾ ₀ represents an impedance to the ground for the transmission line.
The method according to claim 16, wherein the load is an antenna element and the receiver unit is a receiver in a transceiver unit of a base station (BS) .
The method according to claim 22, wherein the connecting unit comprises a circulator, a second switch and a third switch, a first port of the circulator is connected to the transmission line, a second port of the circulator is configured to selectively coupled to one of the following: a first reference impedance of the reference circuit via the second switch, the antenna element via the second switch and the third switch, or a second reference impedance of the reference circuit via the second switch and the third switch, and a third port of the circulator is coupled to the receiver.
The method according to claim 23, wherein the SWR is determined as:

where SWR _k represents a standing wave ratio at a frequency k, M ⁽²⁾ _1, k represents a first measurement at the frequency k where the second port is coupled to the first reference impedance of the reference circuit via the second switch, M ⁽²⁾ _2, k represents a second measurement at the frequency k where the second port is coupled to the second reference impedance of the reference circuit via the second switch and the third switch, M ⁽²⁾ _3, k represents a third measurement where the second port is coupled to the antenna element via the second switch and the third switch, S ⁽²⁾ _31, k represents a S-parameter from the third port to the first port at the frequency k, S ⁽²⁾ _32, k represents a S-parameter from the third port to the second port at the frequency k, S ⁽²⁾ _21, k represents a S-parameter from the second port to the first port at the frequency k, Z ⁽²⁾ _L, k represents the first reference impedance of the reference circuit at the frequency k, Z ⁽²⁾ _L', k represents the second reference impedance of the reference circuit at the frequency k, and Z ⁽²⁾ ₀ represents an impedance to the ground for the transmission line.
The method according to claim 22, wherein the connecting unit comprises a circulator and a fourth switch, a first port of the circulator is coupled to the transmission line, a second port of the circulator is configured to selectively coupled to a third reference impedance of the reference circuit via the fourth switch, or the antenna element via the fourth switch, and a third port of the circulator is coupled to the receiver.
The method according to claim 25, wherein the SWR is determined as:

where SWR _k represents a standing wave ratio at a frequency k, M ⁽³⁾ _1, k represents a first measurement at the frequency k where the second port is coupled to the third reference impedance of the reference circuit via the fourth switch, M ⁽³⁾ _2, k represents a second measurement where the second port is coupled to the antenna element via the fourth switch, S ⁽³⁾ _31, k represents a S-parameter from the third port to the first port at the frequency k, S ⁽³⁾ _32, k represents a S-parameter from the third port to the second port at the frequency k, S ⁽³⁾ _21, k represents a S-parameter from the second port to the first port at the frequency k, Z ⁽³⁾ _L, k represents the third reference impedance of the reference circuit at the frequency k, and Z ⁽³⁾ ₀ represents an impedance to the ground for the transmission line.