Description:TECHNICAL FIELD
[0001] The present disclosure, in general, relates to managing calibration of radio frequency (RF) components in a wireless communication network, and in particular, relates to automatic calibration of RF chains in a base station.
BACKGROUND
[0002] The fifth-generation (5G) new radio (NR) base station (BS) consists of numerous feedback paths to ensure optimal system performance. These feedback paths are used for Digital Pre-Distortion (DPD) correction, transmit power adjustment, Voltage Standing Wave Ratio (VSWR) measurement, receiver automatic gain control (AGC), etc. The feedback paths need to be identical and free from interference or coupling. However, achieving this goal in hardware is difficult due to component parameter variance, trace length differences in the Printed Circuit Board (PCB), electrical coupling from other signals, environmental conditions, etc. As a result, the signals reaching back to the baseband system on chip (SoC) may consist of different power even if the main chains are operating with identical power. Moreover, the presence of the transmit chain or power line near the feedback paths leads to coupling problems. This significantly impacts the ability of the system to detect the actual radio frequency (RF) power level in the output port. The availability of the RF signal with identical power plays a key role in ensuring Multiple Input Multiple Output (MIMO) performance. 5G offers multi-antenna-based MIMO features that demand more complex transceiver systems. This complexity further increases with an increase in the number of transmit chains. The array of switches is used to multiplex the feedback signals to SoC. These switches are also vulnerable to channel leakage and temperature variation, and may degrade the integrity of the feedback signals. The more the transmit chains, the more the feedback paths and the chances of coupling.
[0003] FIG. 1 illustrates a conventional system architecture of 5G NR MIMO BS 100.
[0004] Referring to FIG. 1, the base station 100 includes N number of transceiver chains. A baseband system or System on Chip (SoC) 102 contains a
processing system and a programming logic for baseband processing of incoming data and other control functions. Higher layer (104-1 … 104-N) consists of Medium Access Control (MAC) and Radio Link Control (RLC) layers. Further, physical (PHY) layer and Digital Front End (DFE) (106-1 … 106-N) processes the incoming bits from the higher layers (104-1 … 104-N) into In-phase and Quadrature (IQ) symbols before converting them to analog domain. Furthermore, Digital to Analog Converter (DAC) (108-1 … 108-N) may convert the digital signal into an analog signal.
[0005] Referring to FIG. 1, a power amplifier (110-1 … 110-N) may amplify the signal with desired output power before transmission. Further, a coupler (112-1 … 112-N) may provide coupled output for the feedback path. A switch matrix 114 multiplexes the feedback path of all N chains. The switch matrix 114 may consist of a series of switches depending on the design requirements. Furthermore, an observation Analog to Digital Converter (ADC) 116 converts the analog signal to a digital signal of the feedback paths.
[0006] FIG. 2 illustrates a representation 200 of conventional gain compression versus output power of power amplifier.
[0007] Conventionally, the problem of calibration is addressed by manually calibrating RF paths at the time of manufacturing and then operating the BS with manually calibrated data. The calibration coefficients for each unit may have a slight variation. Different batches of the same component may have slight variations, as shown in FIG. 2. Hence, every piece of equipment manufactured needs to be manually calibrated and tested after assembly. This manual practice of calibration for each unit is not practically possible. As a result, for a batch of manufactured units utilizing the same batch of components, only a small number of units are used for calibration, and an average value of the calibration coefficients is arrived at. These average values are used in the run-time software control systems. This leads to performance variation from unit to unit, as every unit may have a slight variation of the coefficients when compared with the average value. This issue is further amplified in the field environment. In the field, the BS may undergo dynamic environmental conditions. In such conditions, the property of the RF
components may change dynamically, which leads to degradation in the BS performance with one-time manually calibrated coefficients. Once the BS is deployed, it is difficult to calibrate the BS manually again, as it involves external measurement instruments, and the BS is mounted in the cell tower. Technically, it is possible to collect the calibration related data for different environmental conditions, like temperature, humidity, etc., in a simulation environment as part of the design process. However, an average value approach may be prone to inaccuracy as every unit may have its unique characteristics. Hence, there is a need to find a way to calibrate the transceiver chains to deal with the dynamic behavior of the RF signals for optimal BS performance during the operating phase.
[0008] The existing solutions fail to disclose an efficient mechanism for adaptive auto-calibration of the RF chains in a MIMO system. Thus, there is a need for an efficient and adaptive mechanism for auto-calibration of RF chains that considers all the factors for calibration that may possibly lead to degradation in the overall system performance.
OBJECTS OF THE PRESENT DISCLOSURE
[0009] It is an object of the present disclosure to provide an efficient solution for adaptive automatic calibration of radio frequency (RF) paths of a base station in real time.
[0010] It is an object of the present disclosure to provide an efficient mechanism that can be implemented for any wireless technology that leverages Multiple Input Multiple Output (MIMO) transceivers.
[0011] It is an object of the present disclosure to provide an efficient mechanism that can be implemented for both time division duplex (TDD) and frequency division duplex (FDD) mode.
[0012] It is an object of the present disclosure to consider all possible factors for automatic calibration that may lead to degradation in the overall system performance.
SUMMARY
[0013] In an aspect, the present disclosure relates to a method for automatically calibrating radio frequency (RF) transmit chains in a base station, where the method includes monitoring, by a processor, a value of a number of resource block set by a higher layer in the base station, updating, by the processor, a configuration of each of a plurality of RF transmit chains associated to the base station based on the value of the number of resource block, monitoring, by the processor, an antenna output power of said each of the plurality of RF transmit chains, comparing, by the processor, the antenna output power with a pre-defined error threshold for said each of the plurality of RF transmit chains, determining, by the processor, one or more RF transmit chains of the plurality of RF transmit chains that violate the pre-defined error threshold for the number of resource block based on the comparison, and automatically calibrating, by the processor, the determined one or more RF transmit chains in an operating phase of the base station.
[0014] In an embodiment, the updating may include updating, by the processor, a configuration of a variable gain amplifier (VGA) and/or a digital to analog converter (DAC) for said each of the plurality of RF transmit chains based on respective calibrated values, determined during automatic calibration of said each of the plurality of RF transmit chains in a start phase of the base station, corresponding to the value of the number of resource block.
[0015] In an embodiment, for the automatic calibration of said each of the plurality of RF transmit chains in the start phase of the base station, the method may include for said each of the plurality of RF transmit chains: setting, by the processor, a multiplexer to send test data on a given RF transmit chain of the plurality of RF transmit chains, determining, by the processor, a power measured by a power detector at a coupled output port of a coupler on the given RF transmit chain, calculating, by the processor, the antenna output power using the determined power, determining, by the processor, a difference between the antenna output power and a target power, comparing, by the processor, the difference with the pre-defined error threshold, responsive to the difference being greater than or equal to the pre-defined error threshold, updating, by the processor, a start phase configuration of
the given RF transmit chain to compensate the difference, and responsive to the difference being less than the pre-defined error threshold, storing, by the processor, the start phase configuration of the given RF transmit chain in a database associated with the base station.
[0016] In an embodiment, wherein determining, by the processor, the one or more RF transmit chains may include monitoring, by the processor, a temperature of a power amplifier, comparing, by the processor, the temperature of the power amplifier with a pre-defined operating temperature threshold, and determining, by the processor, the one or more RF transmit chains that violate the pre-defined operating temperature threshold and the pre-defined error threshold, wherein the one or more RF transmit chains may be determined based on the temperature of the power amplifier being greater than the pre-defined operating temperature threshold and the antenna output power being greater than the pre-defined error threshold for a given RF transmit chain of the plurality of RF transmit chains.
[0017] In an embodiment, wherein in response to the temperature of the power amplifier being less than the pre-defined operating temperature threshold and the antenna output power being less than the pre-defined error threshold, the method may include continuing, by the processor, to monitor the value of the number of resource block for a pre-defined monitoring time interval and update the configuration of said each of the plurality of RF transmit chains based on the value of the number of resource block.
[0018] In an embodiment, the method may include automatically calibrating, by the processor, the determined one or more RF transmit chains in the operating phase of the base station, during a guard period of a special time slot in a radio frame, and setting, by the processor, a multiplexer to send test data with the number of resource block on each of the determined one or more RF transmit chains during the guard period, or automatically calibrating, by the processor, the determined one or more RF transmit chains in the operating phase of the base station, during a synchronization signal (SS) or a physical broadcast channel (PBCH) symbol in a radio frame.
[0019] In an embodiment, for a time division duplex (TDD) mode, the method may include automatically calibrating, by the processor, the determined one or more RF transmit chains in the operating phase of the base station, during a guard period of a special time slot in a radio frame, or during a synchronization signal (SS) or a physical broadcast channel (PBCH) symbol in the radio frame, and setting, by the processor, a multiplexer to send test data with the number of resource block on each of the determined one or more RF transmit chains, and for a frequency division duplex (FDD) mode, the method may include automatically calibrating, by the processor, the determined one or more RF transmit chains in the operating phase of the base station, during the SS or the PBCH symbol in the radio frame.
[0020] In an embodiment, for automatically calibrating, by the processor, the determined one or more RF transmit chains in the operating phase, the method may include for each of the determined one or more RF transmit chains: determining, by the processor, a power measured by a power detector at a coupled output port of a coupler on a given RF transmit chain of the determined one or more RF transmit chains, calculating, by the processor, the antenna output power using the determined power, determining, by the processor, a difference between the calculated antenna output power and a target power, comparing, by the processor, the difference with the pre-defined error threshold, responsive to the difference being greater than or equal to the pre-defined error threshold, updating, by the processor, an operating phase configuration of the given RF transmit chain in real time to compensate the difference, and responsive to the difference being less than the pre-defined error threshold, storing, by the processor, the operating phase configuration of the given RF transmit chain in a database associated with the base station.
[0021] In an embodiment, the antenna output power may be based on an output power of the power amplifier, a summed insertion loss of components between an output of the power amplifier and an antenna input, a trace loss from the output of the power amplifier and the antenna input, a coupler coupling loss, and a power measured by a power detector at a coupled output port of a coupler.
[0022] In another aspect, the present disclosure relates to a method for automatically calibrating RF transmit chains in a start phase of a base station, where the method includes setting, by a processor, a multiplexer to send test data on a given RF transmit chain of a plurality of RF transmit chains, determining, by the processor, a power measured by a power detector at a coupled output port of a coupler on the given RF transmit chain, calculating, by the processor, an antenna output power using the determined power, determining, by the processor, a difference between the antenna output power and a target power, comparing, by the processor, the difference with a pre-defined error threshold, responsive to the difference being greater than or equal to the pre-defined error threshold, updating, by the processor, a start phase configuration of the given RF transmit chain to compensate the difference, and responsive to the difference being less than the pre-defined error threshold, storing, by the processor, the start phase configuration of the given RF transmit chain, corresponding to a value of a number of resource block, in a database associated with the base station.
[0023] In another aspect, the present disclosure relates to a method for automatically calibrating radio frequency (RF) feedback chains in a base station, where the method includes for each of a plurality of RF feedback chains: monitoring, by a processor, a value of a number of resource block set by a higher layer in the base station, updating, by the processor, a configuration of each of a plurality of RF transmit chains and a configuration of said each of the plurality of RF feedback chains associated to the base station, based on the value of the number of resource block, determining, by the processor, a power measured by a power detector at an end of a given RF feedback chain of the plurality of RF feedback chains, calculating, by the processor, a feedback power at an input of an observation analog to digital converter based on the determined power measured by the power detector, determining, by the processor, a difference between the feedback power at the input of the observation analog to digital converter and a reference power, comparing, by the processor, the difference with a pre-defined accuracy threshold, and automatically calibrating, by the processor, the given RF feedback chain based on the comparison in an operating phase of the base station.
[0024] In an embodiment, the updating may include updating, by the processor, a configuration of a variable gain amplifier (VGA) and/or a digital to analog converter (DAC) for said each of the plurality of RF transmit chains and a configuration of at least a digital step attenuator (DSA) for said each of the plurality of RF feedback chains based on respective calibrated values, determined during automatic calibration of the plurality of RF transmit chains and the plurality of RF feedback chains in a start phase of the base station, corresponding to the value of the number of resource block.
[0025] In an embodiment, for the automatic calibration of said each of the plurality of RF feedback chains in the start phase of the base station, the method may include for said each of the plurality of RF feedback chains: setting, by the processor, a multiplexer to send test data on a given RF transmit chain of the plurality of RF transmit chains, updating, by the processor, a configuration of the given RF transmit chain of the plurality of RF transmit chains based on the value of the number of resource block, determining, by the processor, the power measured by the power detector for a given RF feedback chain of the plurality of RF feedback chains, calculating, by the processor, the feedback power based on the power measured by the power detector, comparing, by the processor, a difference between the feedback power and the reference power with the pre-defined accuracy threshold, responsive to the difference being greater than or equal to the pre-defined accuracy threshold, updating, by the processor, a start phase configuration of the given RF feedback chain in real time to compensate the difference, and responsive to the difference being less than the pre-defined accuracy threshold, storing, by the processor, the start phase configuration of the given RF feedback chain in a database associated with the base station.
[0026] In an embodiment, responsive to the difference being greater than or equal to the pre-defined accuracy threshold, the method may include storing, by the processor, the configuration of the given RF feedback chain in a database associated with the base station, and responsive to the difference being less than the pre-defined accuracy threshold, determining, by the processor, one or more defected RF feedback chains of the plurality of RF feedback chains for automatic calibration.
[0027] In an embodiment, the method may include automatically calibrating, by the processor, each of the one or more defected RF feedback chains, during a guard period of a special time slot in a radio frame, and setting, by the processor, a multiplexer to send test data with the number of resource block on said each of the one or more defected RF feedback chains during the guard period, or automatically calibrating, by the processor, each of the one or more defected RF feedback chains, during a synchronization signal or a physical broadcast channel (PBCH) symbol in a radio frame.
[0028] In an embodiment, for a time division duplex (TDD) mode, the method may include automatically calibrating, by the processor, each of the one or more defected RF feedback chains, during a guard period of a special time slot in a radio frame, or during a synchronization signal (SS) or a physical broadcast channel (PBCH) symbol in the radio frame, and setting, by the processor, a multiplexer to send test data with the number of resource block on said each of the one or more defected RF feedback chains during the guard period, and for a frequency division duplex (FDD) mode, the method may include automatically calibrating, by the processor, each of the one or more defected RF feedback chains, during the SS or the PBCH symbol in the radio frame.
[0029] In an embodiment, for automatically calibrating, by the processor, said each of the one or more defected RF feedback chains, the method may include for each of the determined one or more defected RF feedback chains: determining, by the processor, the power measured by the power detector for a given defected RF feedback chain of the determined one or more defected RF feedback chains, calculating, by the processor, the feedback power based on the power measured by the power detector, comparing, by the processor, a difference the feedback power and the reference power with the pre-defined accuracy threshold, responsive to the difference being greater than or equal to the pre-defined accuracy threshold, updating, by the processor, an operating phase configuration of the given defected RF feedback chain in real time to compensate the difference, and responsive to the difference being less than the pre-defined accuracy threshold, storing, by the
processor, the operating phase configuration of the given defected RF feedback chain in the database.
[0030] In another aspect, the present disclosure relates to a base station for automatic calibration of radio frequency (RF) transmit chains, including a processor, and a memory operatively coupled to the processor, wherein the memory comprises processor-executable instructions which, when executed by the processor, cause the processor to monitor a value of a number of resource block set by a higher layer in the base station, update a configuration of each of a plurality of RF transmit chains associated to the base station based on the value of the number of resource block, monitor an antenna output power of said each of the plurality of RF transmit chains, compare the antenna output power with a pre-defined error threshold for said each of the plurality of RF transmit chains, determine one or more RF transmit chains of the plurality of RF transmit chains that violate the pre-defined error threshold for the number of resource block based on the comparison, and automatically calibrate the determined one or more RF transmit chains in an operating phase of the base station.
BRIEF DESCRIPTION OF DRAWINGS
[0031] The accompanying drawings, which are incorporated herein, and constitute a part of this disclosure, illustrate exemplary embodiments of the disclosed methods and systems which like reference numerals refer to the same parts throughout the different drawings. Components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Some drawings may indicate the components using block diagrams and may not represent the internal circuitry of each component. It will be appreciated by those skilled in the art that disclosure of such drawings includes the disclosure of electrical components, electronic components, or circuitry commonly used to implement such components.
[0032] FIG. 1 illustrates a conventional system architecture of 5G Multiple Input Multiple Output (MIMO) base station.
[0033] FIG. 2 illustrates a representation of conventional gain compression versus output power of power amplifier.
[0034] FIG. 3 illustrates an exemplary system architecture of a base station for implementing the proposed mechanism, in accordance with an embodiment of the present disclosure.
[0035] FIG. 4 illustrates an exemplary system architecture of a base station for automatic calibration of radio frequency (RF) transmit chains, in accordance with an embodiment of the present disclosure.
[0036] FIG. 5 illustrates a flow chart of an exemplary method for automatic calibration of RF transmit chains during the start phase, in accordance with an embodiment of the present disclosure.
[0037] FIG. 6 illustrates an exemplary representation of a 5G New Radio (NR) Time Division Duplex (TDD) radio frame, in accordance with an embodiment of the present disclosure.
[0038] FIG. 7 illustrates a flow chart of an exemplary method for automatic calibration of RF transmit chains during operating phase of base station in TDD mode, in accordance with an embodiment of the present disclosure.
[0039] FIG. 8 illustrates a flow chart of an exemplary method for automatic calibration of RF transmit chains during operating phase of base station in Frequency Division Duplex (FDD) mode, in accordance with an embodiment of the present disclosure.
[0040] FIG. 9 illustrates an exemplary system architecture of a base station for automatic calibration of RF feedback chains, in accordance with an embodiment of the present disclosure.
[0041] FIG. 10 illustrates a flow chart of an exemplary method for automatic calibration of RF feedback chains during the start phase, in accordance with an embodiment of the present disclosure.
[0042] FIG. 11 illustrates a flow chart of an exemplary method for automatic calibration of RF feedback chains during operating phase of base station in TDD mode, in accordance with an embodiment of the present disclosure.
[0043] FIG. 12 illustrates a flow chart of an exemplary method for automatic calibration of RF feedback chains during operating phase of base station in FDD mode, in accordance with an embodiment of the present disclosure.
[0044] FIG. 13 illustrates an exemplary computer system in which or with which embodiments of the present disclosure may be implemented.
[0045] The foregoing shall be more apparent from the following more detailed description of the disclosure.
DETAILED DESCRIPTION
[0046] In the following description, for the purposes of explanation, various specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent, however, that embodiments of the present disclosure may be practiced without these specific details. Several features described hereafter can each be used independently of one another or with any combination of other features. An individual feature may not address all of the problems discussed above or might address only some of the problems discussed above. Some of the problems discussed above might not be fully addressed by any of the features described herein.
[0047] The ensuing description provides exemplary embodiments only and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the ensuing description of the exemplary embodiments will provide those skilled in the art with an enabling description for implementing an exemplary embodiment. It should be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the disclosure as set forth.
[0048] The various embodiments throughout the disclosure will be explained in more detail with reference to FIGs. 3-13.
[0049] FIG. 3 illustrates an exemplary system architecture of a base station 300 for implementing the proposed mechanism, in accordance with an embodiment of the present disclosure.
[0050] In particular, the exemplary system architecture may represent a communication system such as a 5G or next-generation communications system 300. As depicted, the architecture 300 includes N number of transceiver chains. The System on Chip (SoC) 302 contains a processing system (or interchangeably referred to as a processor) and a programming logic for baseband processing of incoming data and other control functions.
[0051] Further, higher layer and high Physical (PHY) layer (304-1 … 304-N) may consist of Media Access Control (MAC) and Radio Link Control (RLC) layers, including functionality of the PHY layer. Low PHY and Digital Front End (DFE) (306-1 … 306-N) may process incoming frequency domain In-phase and Quadrature (IQ) symbols into time domain IQ symbols before converting to analog domain. Further, a Digital to Analog Converter (DAC) (308-1 … 308-N) may convert digital signal into analog signal. In some embodiments, the DAC (308-1 … 308-N) present in the SoC 302 may have the option of an inbuilt Variable Gain Amplifier (VGA), Digital Step Attenuator (DSA), or variable current to change radio frequency (RF) power of the signal at the DAC output (308-1 … 308-N). It can be controlled digitally by the SoC 302. The initial values can be set as per the design implementation. It is useful for tuning the output power at the micro level, depending on the design implementation.
[0052] Further, a VGA (310-1 … 310-N) provides variable gain to the RF signal in order to maintain the target output power. A gain of the VGA (310-1 … 310-N) may be controlled digitally by the SoC 302. Further, the VGA (310-1 … 310-N) provides another flexibility to tune the output power at the macro level, depending upon its characteristics. A power amplifier (PA) (312-1 … 312-N) may refer to an amplifier that amplifies the signal with the desired output power before transmission. Further, a coupler (314-1 … 314-N) may provide coupled output for a feedback path.
[0053] As depicted in FIG. 3, there is a power detector (PD) (316-1 … 316-N) present after every coupler (314-1 … 314-N). In some embodiments, the PD (316-1 … 316-N) may measure the power of the RF signal and send it to the SoC 302 in
binary format. The PD (316-1 … 316-N) may also forward the RF signal with little loss.
[0054] Further, a switch matrix 318 multiplexes the feedback path of all N chains. In some embodiments, the switch matrix 318 may include a series of switches depending on the design requirements. A PD 320 is present before the SoC 302, which may measure the power of the RF signal received from the switch matrix 318 and send it to the SoC 302 in binary format. The PD 320 may also forward the RF signal with little loss.
[0055] The SoC 302 may further include a DSA 322. The DSA 322 may be separate or inbuilt with an Analog to Digital Converter (ADC). The DSA 322 may change the RF power of the signal at the ADC input. Further, an observation (ORX) ADC 324 may convert the analog signal received from the DSA 322 to a digital signal.
[0056] In accordance with embodiments of the present disclosure, the SoC 302 may include an auto-calibration logic module implemented as a processing system or processor 326. It may be appreciated that the terms “auto-calibration logic module” and “processor” may be used interchangeably throughout the disclosure.
[0057] In some embodiments, during a start phase or a power-on-self-test (POST) of the base station 300, the processor 326 may measure the antenna output power and feedback power, and compare them with a pre-defined error threshold (????) and a pre-defined accuracy threshold (????), respectively. It may be appreciated that the terms “start phase” and “power-on-self-test (POST) may be used interchangeably throughout the disclosure. Further, the processor 326 may identify the appropriate configurations for each transmit chain, for example, VGA (310-1 … 310-N) and DAC (308-1 … 308-N) configurations for each transmit chain, and configurations for each feedback chain, for example, DSA 322 configuration for each feedback chain. In some embodiments, the base station 300 may store the configurations in a local database (not shown). In some embodiments, during an operating phase or user data transmission in real-time, based on the calculated values of the antenna power and feedback values, the processor 326 may identify control signals CS11 and CS21 to control DAC (308-1) and VGA (310-1),
respectively, for a first RF transmit chain, and similarly, CS1N and CS2N to control DAC (308-N) and VGA (310-N), respectively for the Nth RF transmit chain to adaptively control the output power of each of the RF paths (e.g., RF transmit chains). In some embodiments, the processor 326 may identify control signals CS3 and CS4 to control the switch matrix 318 and the DSA 322, respectively, to adaptively control the feedback path of each of the RF chains. In some embodiments, the processor 326 may control a multiplexer (330-1 … 330-N) in each transmit chain as per requirement. For example, in some embodiments, the processor 326 may generate test data 328 by a pseudo-random sequence for auto-calibration of RF chains. The multiplexer (330-1 … 330-N) may switch between user data from the higher layer (304-1 … 304-N) and test data 328 from the local database.
[0058] FIG. 4 illustrates an exemplary system architecture of a base station 400 for automatic calibration of RF transmit chains, in accordance with an embodiment of the present disclosure. It may be appreciated that the components depicted in FIG. 3 correspond to the components depicted in FIG. 4.
[0059] Referring to FIG. 4, the base station 400 may initiate a POST (i.e., start phase) after the bootup to validate and calibrate its features. After a successful POST, the base station 400 may operate in an operating phase, i.e. start data transmission. The RF transmit chains may be calibrated during the POST for smooth transmission. This will be explained in detail with reference to FIG. 5.
[0060] FIG. 5 illustrates a flow chart of an exemplary method 500 for automatic calibration of RF transmit chains during the start phase, in accordance with an embodiment of the present disclosure.
[0061] Referring to FIG. 5, at step 502, an auto-calibration logic module or processor (e.g., 326) may set all multiplexers 330 to send test data 328 with different resource block (RB) allocations on each transmit chain during the start phase or POST. The test data may propagate through all the blocks of the transmit chain and reach an antenna port (refer FIG. 4). At step 504, a given RB allocation may be considered. Similarly, at step 506, a given RF transmit chain may be considered.
[0062] Further, at step 508, the processor 326 may determine a power measured by a PD 316 at a coupled port of a coupler 314. In some embodiments, the PD 316 may send the data to SoC 302, for example, to the processor 326 in the form of binary format. The processor 326 may convert the power detected by the PD 316 using a suitable conversion method. In some embodiments, the conversion may be provided by device manufacturers (power detector, device Integrated Circuit (IC) datasheet, or the like).
[0063] At step 510, the processor 326 may calculate an antenna output power at an antenna port using the detected power (from step 508). For example, the power at the antenna port ???????? may be given as follows:
????????=??????-(??????+????????????,????-??????)=??????-?????????????? ??????=????????+??????????????
( 1 )
where ??????????????=??????+????????????,????-??????, ?????? is a PA output power, ?????? is a summed insertion loss of all RF components between PA output to the antenna input, and ????????????,????-?????? is a trace loss from PA output to the antenna input.
After the conversion, the power measured by the power detector ?????? is given as follows: ??????=??????-?????? ??????=??????+??????
( 2 )
where ?????? is a coupler coupling loss,
Using ( 1 ) and Error! Reference source not found., the power at the antenna port is given as follows: ????????=??????+??????-??????????????
( 3 )
It may be appreciated that all powers are in dBm, and losses are in dB.
[0064] Referring to FIG. 5, at step 512, the processor 326 may determine a difference between the calculated ???????? and a target power. In some embodiments, the target power may be based on design implementation, RB allocations, and product requirements. Further, at step 514, the processor 326 may compare the
difference with a pre-defined error threshold (????). In an example, the value of the pre-defined error threshold may be 0.1 or 0.2 dB depending upon the design implementation. It may be appreciated that the value of the pre-defined error threshold is configurable and may be stored in a database for different configurations.
[0065] In some embodiments, if the difference is greater than or equal to the pre-defined error threshold (|???????? - ??????????????|= ????), then at step 516, the processor 326 may compensate the difference by updating start phase settings or configurations of a given RF transmit chain in real-time as per implementation, and repeat steps 508-514. In some embodiments, the processor 326 may update the start phase configuration of a DAC 308 and a VGA 310 of the given RF transmit chain in real-time to compensate the difference.
[0066] In some embodiments, if the difference is less than the pre-defined error threshold, (|???????? - ??????????????|< ????), indicating that the antenna output power is equivalent to the target power within the pre-defined error threshold, then at step 518, the processor 326 may store the start phase configuration of the given RF transmit chain in a local database. In some embodiments, the processor 326 may store the start phase configurations of the DAC 308 and the VGA 310 of the given RF transmit chain in the database.
[0067] Further, at step 520, the processor 326 may determine if the automatic calibration is completed for all RF transmit chains. If not, then the processor 326 may select the next transmit chain and repeat steps 508-518. If yes, then at step 522, the processor 326 may determine if the automatic calibration is completed for all RF transmit chains with different RB configurations. If no, then the processor 326 may select the next RB allocation and repeat steps 506-520. If yes, then all the configurations may be stored in the local database for use during an operating phase of the base station.
[0068] It may be appreciated that the method 500 is applicable for both time division duplex (TDD) and frequency division duplex (FDD) mode of the base station, i.e. automatic calibration of RF transmit chains during the start phase or POST.
[0069] FIG. 6 illustrates an exemplary representation of a 5G NR TDD radio frame 600, in accordance with an embodiment of the present disclosure.
[0070] In some embodiments, during data transmission or operating phase of the base station, output power at an antenna port changes dynamically depending on value of number of resource block ?????? that can be set by the higher layer (e.g., 304). Hence, it may be important to monitor the ?????? and update configurations of RF transmit chains (e.g., DAC and/or VGA configurations) with calibrated values based on ??????. The calibrated values may be computed using interpolation or curve fitting of the data collected during the POST (e.g., method 500 of FIG. 5). This helps in achieving the target power in real time. However, due to the change in environmental conditions, the behavior of RF components may change from their normal behavior, which may lead to degradation in the performance of the base station with earlier computed calibrated values. Therefore, there exists a need to re-calculate the calibrated values in real time. Operating the base station with a TDD radio frame provides an opportunity to determine the calibrated values in real time during special time slots. This provides leverage to the base station to achieve the target power in real time for the TDD mode.
[0071] Referring to FIG. 6, considering the 30kHz subcarrier spacing, the 10ms radio frame consists of 20 time slots, each having 14 Orthogonal Frequency Division Multiplexing (OFDM) symbols. The downlink (DL) may occupy 14 slots, and the uplink (UL) may occupy 4 slots out of 20 in normal conditions. The rest of the 2 slots may be used as special slots. The 14 OFDM symbols in each special slot may be configured as 10 for DL, 2 for guard period, and 2 for UL. In order to avoid information loss, the base station may utilize the guard period of the special time slots to determine the calibrated values in real time. This will be explained in detail with reference to FIG. 7.
[0072] FIG. 7 illustrates a flow chart of an exemplary method 700 for automatic calibration of RF transmit chains during operating phase of base station in TDD mode, in accordance with an embodiment of the present disclosure.
[0073] Referring to FIG. 7, at step 702, an auto-calibration logic module or processor 326 may monitor a value of number of resource block ?????? set by the
higher layer 304. At step 704, the processor 326 may update a configuration of each of a plurality of RF transmit chains in the base station based on the value of the number of resource block. In some embodiments, a configuration of DAC 308 and/or VGA 310 may be updated, based on Table 1. Table 1 provides DAC and VGA configuration for different RB allocations for each RF transmit chain for TDD mode of the base station. Table 1 may be generated by interpolating or curve-fitting the data collected for automatic calibration during POST for the TDD base station system (e.g., method 500 of FIG. 5).
Transmit Chain Index
#1
#2
?
#N-1
#N
RB Allocation (%)
10
V1,1
D1,1
V1,2
D1,2
?
V1,N-1
D1,N-1
V1,N
D1,N
20
V2,1
D2,1
V2,2
D2,2
?
V2,N-1
D2,N-1
V2,N
D2,N
?
?
?
?
?
?
90
V9,1
D9,1
V9,2
D9,2
?
V9,N-1
D9,N-1
V9,N
D9,N
100
V10,1
D10,1
V10,2
D10,2
?
V10,N-1
D10,N-1
V10,N
D10,N
Note:
1. Vi,j represents the VGA configuration for i% RB allocation and jth transmit antenna.
2. Vi,j can be in the form of VGA gain, attenuation, or N-bit codeword. It may depend on the VGA chip and design implementation.
3. Di,j represents the DAC configuration for i% RB allocation and jth transmit antenna.
4. Di,j can be in the form of DAC gain, attenuation, or current. It may depend on the DAC of the SoC chip and design implementation.
5. The RB allocation can be in terms of the range of number or %.
6. The step size of the RB allocation can be decided during the implementation, and it is not necessary to be a single step size.
Table 1
[0074] In some embodiments, after updating the configurations of the VGA 310 and/or DAC 308, the antenna port should have a target power corresponding to the RB configuration.
[0075] Referring to FIG. 7, at step 706, the processor 326 may monitor an antenna output power (????????) for each RF transmit chain, for example, to detect anomaly. Further, at step 708, the processor 326 may compare the antenna output power with a pre-defined error threshold (????). In some embodiments, the processor 326 may monitor a temperature of the PA 312 (????????????). It may be appreciated that the temperature may be monitored via a temperature sensor configured with the PA 312. Further, the processor 326 may compare the temperature of the PA 312 with a pre-defined operating temperature threshold (????h). If the temperature is less than the pre-defined operating temperature threshold and a difference of the antenna output power and a target power is less than the pre-defined error threshold for all RF transmit cains for the given ??????, i.e., ????????????