Apparatus and method for supporting calibration for radio frequency circuit in communication device

A method for calibration for a Radio Frequency (RF) circuit in a communication device is provided. The method includes performing an independent RF-circuit calibration, storing calibration data generated through the calibration, in an external storage unit, and downloading, to the communication device, partial calibration data among the calibration data stored in the external storage unit.

PRIORITY

This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed on Feb. 13, 2012 in the Korean Intellectual Property Office and assigned Serial No. 10-2012-0014273, the contents of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a communication device. More particularly, the present invention relates to calibration in a communication device.

2. Description of the Related Art

In recent years, there is a trend of supporting multi-band and multi-mode, and concurrently minimizing cost and power consumption, in a mobile communication system. To meet this trend, a transceiver structure of a Mobile Station (MS) may use a direct conversion scheme. A transceiver employing the direct conversion scheme has a simple structure, and has an advantageous feature in size and cost, and has a reconfigurable structure that is easy to use. However, the direct conversion scheme has a characteristic of being sensitive to circuit impairment such as In-phase/Quadrature-phase (IQ) mismatch, Transmitter Local Oscillator (TX LO) feed-through, RX Direct Current (DC)-offset and the like. The imperfection of the aforementioned Radio Frequency (RF) processing means is one cause of transceiver performance deterioration. Accordingly, calibration is performed to compensate for the aforementioned imperfection.

Also, as the commercialization of a next-generation system having a high data rate makes progress, a transceiver supporting the high data rate is being developed. To provide the high data rate, the transceiver requires lower Error Vector Magnitude (EVM) performance than a legacy system. To meet the low EVM, a distortion of the transceiver generated while a signal goes through the whole system should be minimized. The distortion of the transceiver results in the deterioration of a Signal to Noise Ratio (SNR) of a signal. Mostly, the distortion of the transceiver is generated while a signal goes through an analog and RF circuit. In order to remove the impairment of the analog and RF circuit to guarantee performance, calibration for the analog and RF circuit is performed.

In general, the calibration for the analog and RF circuit is controlled in a digital block processing a digital signal. For instance, the digital block includes a modulator/demodulator (modem). For example, the calibration for the analog and RF circuit is carried out by a control signal from the modem, in a state where the analog and RF circuit and the modem interwork with each other. In this case, it is difficult to achieve an accurate measurement for analog and RF circuit performance, because self-calibration of a chip level including the analog and RF circuit is not performed. Accordingly, when the analog and RF circuit goes beyond a performance difference assumed as a margin upon interworking with the modem, in other words, when the calibration for the analog and RF circuit is performed in a situation where the analog and RF circuit and the modem interwork with each other, there is a possibility that a situation occurs in which the performance of the analog and RF circuit does not meet the required system standard. Also, the calibration for the analog and RF circuit performed in a state where the analog and RF circuit and the modem interwork with each other consumes a relatively higher cost than a test at a chip level.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages below. Accordingly, an aspect of the present invention is to provide an apparatus and method for reducing a cost for calibration in a communication device.

Another aspect of the present invention is to provide an apparatus and method for performing effective calibration for a Radio Frequency (RF) circuit in a communication device.

A further aspect of the present invention is to provide an apparatus and method for performing effective calibration for an RF circuit before the RF circuit and a modulator/demodulator (modem) interwork with each other in a communication device.

Yet another aspect of the present invention is to provide an apparatus and method for performing calibration of a chip level in a communication device.

Still another aspect of the present invention is to provide an apparatus and method for transceiving a signal by using result data of a calibration carried out at a chip level in a communication device.

Still another aspect of the present invention is to provide an apparatus and method for performing calibration supporting a multi-band in a communication device.

Still another aspect of the present invention is to provide an apparatus and method for exchanging result data of calibration with an external server in a communication device.

Still another aspect of the present invention is to provide an apparatus and method for providing only data corresponding to a mode supported by a Mobile Station (MS) among result data of calibration stored in an external server, in a communication device.

The above aspects are addressed by providing an apparatus and method for supporting calibration for an RF circuit in a communication device.

In accordance with one aspect of the present invention, a method of calibration for an RF circuit in a communication device is provided. The method includes performing an independent RF-circuit calibration, storing calibration data generated through the calibration, in an external storage unit, and downloading, to the communication device, partial calibration data among the calibration data stored in the external storage unit.

In accordance with another aspect of the present invention, a method of calibration for an RF circuit in a communication device is provided. The method includes generating calibration data for a plurality of frequency bands through calibration, and providing the calibration data for the plurality of frequency bands, to an external storage unit.

In accordance with a further aspect of the present invention, a method of managing calibration data for a communication device is provided. The method includes receiving calibration data for a plurality of frequency bands, storing the received calibration data, and providing calibration data for a partial frequency band among the calibration data.

In accordance with yet another aspect of the present invention, a method of calibration for an RF circuit in a communication device is provided. The method includes downloading calibration data from an external storage unit, and determining additional calibration data through a calibration, in a state where the RF circuit having applied the calibration data and a modem interwork with each other.

In accordance with still another aspect of the present invention, an operation method of a communication device is provided. The method includes retrieving at least one compensation value corresponding to an operation state from calibration data that is determined through a calibration implemented independently by an RF circuit provided in the communication device and, by using the compensation value, controlling at least one of a magnitude and a phase of at least one of a transmission signal and a reception signal to compensate for a distortion generated in the RF circuit.

In accordance with still another aspect of the present invention, a communication device is provided. The device includes an RF circuit and a modem. The RF circuit performs an independent RF-circuit calibration, and stores calibration data generated through the calibration, in an external storage unit. The modem downloads, to the communication device, partial calibration data among the calibration data stored in the external storage unit.

In accordance with still another aspect of the present invention, an RF circuit apparatus in a communication device is provided. The apparatus includes a controller and an output unit. The controller generates calibration data for a plurality of frequency bands through a calibration. The output unit provides the calibration data for the plurality of frequency bands, to a server.

In accordance with still another aspect of the present invention, an apparatus for managing calibration data for a communication device is provided. The apparatus includes a storage unit and a communication unit. The storage unit stores calibration data for a plurality of frequency bands. The communication unit receives the calibration data, and for transmitting calibration data for a partial frequency band among the calibration data.

In accordance with still another aspect of the present invention, a modem apparatus for a communication device is provided. The apparatus includes a storage unit and a controller. The storage unit stores calibration data downloaded from an external server. The controller determines additional calibration data through a calibration, in a state where a RF circuit having applied the calibration data and the modem interwork with each other.

In accordance with still another aspect of the present invention, a communication device is provided. The device includes a storage unit and a controller. The storage unit stores calibration data that is determined through a calibration implemented independently of an RF circuit provided in the communication device. The controller retrieves at least one compensation value corresponding to an operation state from the calibration data and, by using the compensation value, controls at least one of a magnitude and a phase of at least one of a transmission signal and a reception signal to compensate for a distortion generated in the RF circuit.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A technology for calibration for a Radio Frequency (RF) circuit in a communication device is described herein.

Herein, an effective calibration technique applicable to an RF circuit is proposed. The RF circuit can be referred to as an ‘RF Integrated Circuit (RFIC)’. In detail, through two-step processes, calibration according to an exemplary embodiment of the present invention minimizes a calibration procedure to be carried out in a state of interworking with a modulator/demodulator (modem). That is, most processes of calibration are carried out as RF circuit self-calibration, i.e., an independent RF-circuit calibration and therefore, the calibration is performed in an RF-circuit chip state in which the RF circuit is not installed in a Mobile Station (MS). According to this, testing the performance of the RF circuit is carried out before the RF circuit interworks with the modem, thereby decreasing the uncertainty for the performance of the RF circuit and reducing a calibration procedure for the MS, which would incur a relatively high cost for testing. A calibration according to an exemplary embodiment of the present invention is described below in detail.

FIG. 1conceptually illustrates calibration in a communication device according to an exemplary embodiment of the present invention.

Referring toFIG. 1, calibration according to an exemplary embodiment of the present invention includes a first calibration step110and a second calibration step130and further, includes a step120of storing calibration data determined through the first calibration step110. The first calibration step110is a calibration implemented in a chip state of no interworking with a modem, and the second calibration step130is a calibration implemented in a state of interworking with the modem. That is, the first calibration step110is performed in a state where an RF circuit is not connected with other circuits (e.g., the modem) included in the communication device. The first calibration step110includes calibration for frequencies of all bands supported by the communication device. In detail, the first calibration step110includes calibration of predefined items for constituent elements of the RF circuit in each of all frequency bands. For example, the calibration of the predefined items can include a calibration for at least one of Transmitter/Receiver (TX/RX) gain step error, TX/RX In-phase/Quadrature-phase (IQ) mismatch, TX Local Oscillator (LO) feed-through, RX Direct Current (DC)-offset, a Voltage Controlled Oscillator (VCO), etc.

Next, the step120of storing the calibration data determined through the first calibration step110in a separate external server is performed. Here, the calibration data includes correction values for distortion. The calibration data stored in the external server includes calibration data for all frequency bands. The external server includes a communication unit for transceiving the calibration data with the external server and a storage unit for storing the calibration data. The communication unit receives the calibration data through a wired interface or a wireless interface. According to an exemplary embodiment of the present invention, the external server can be implemented in various forms. For example, the external server can be implemented using a Personal Computer (PC), a flash memory, a Universal Serial Bus (USB) memory and the like.

The second calibration step130includes calibration for a frequency of at least one band supported by an MS in which the RF circuit is to be installed. For the sake of the second calibration step130, only calibration data for at least one band supported by the MS among the calibration data for all frequency bands stored in the external server is downloaded to the MS, and calibration for the entire MS is performed in a state where the downloaded calibration data is applied to the RF circuit. Most of the calibration is completed through the first calibration step110, and the second calibration step130takes a scheme of seeking an offset value for correcting a difference between a measurement value of a chip alone and a measurement value of the entire MS.

An aspect of the present invention is to reduce a measurement time in a state of interworking with a modem, through the aforementioned process. Also, according to an exemplary embodiment of the present invention, Error Vector Magnitude (EVM) and spectrum mask characteristics of the RF circuit are accurately measured after calibration for TX/RX IQ mismatch, TX/RX DC-offset and the like on a chip of an RF circuit is completed. Therefore, uncertainty is reduced compared to a related-art scheme of measuring the EVM characteristic and the like of the RF circuit after interworking with the modem.

For the sake of the first calibration step1110described above with reference toFIG. 1, the RF circuit can be constructed as described below.

FIG. 2is a block diagram illustrating a construction of an RF circuit in a communication device according to an exemplary embodiment of the present invention.

Referring toFIG. 2, the RF circuit includes a calibration controller210, a feedback path220, an RF register230, and an RF processor240. The calibration controller210generates a reference signal for calibration, and analyzes the reference signal. The reference signal denotes an input signal for observing an output result of the RF processor240. For example, the reference signal, which is a transmission signal, a reception signal, or a control signal, can be provided to the RF processor240. And, the calibration controller210generates calibration data by using the analysis result on the reference signal. Here, the calibration data includes compensation values for distortion.

The feedback path220provides the calibration controller210with a result of processing the reference signal in the RF processor240. For example, if the reference signal is provided as a transmission signal, a value after the reference signal passes through a transmission path is provided to the calibration controller210through the feedback path220. Or, if the reference signal is provided as a reception signal, a value after the reference signal passes through a reception path is provided to the calibration controller210through the feedback path220. Or, if the reference signal is provided as a control signal, a signal generated due to an operation of an RF element controlled by the reference signal is provided to the calibration controller210through the feedback path220.

According to an instruction of the calibration controller210, the RF register230generates a physical signal controlling RF elements included in the RF processor240. The RF processor240performs RF processing for a transmission signal or a reception signal. For example, the RF processor240performs at least one of analog-digital conversion, digital-analog conversion, filtering, mixing, and gain control. In other words, the RF processor240includes at least one of an oscillator, a mixer, an amplifier, a gain control element, a Digital to Analog Converter (DAC), an Analog to Digital Converter (ADC), and a filter. For example, a transmission path can include the DAC, the filter, the mixer, the gain control element and the like and, among them, the DAC to the mixer are constructed by two paths of an In-phase (I) channel and a Quadrature-phase (Q) channel. Also, a reception path can include the gain control element, the mixer, the filter, the ADC and the like and, among them, the mixer to the ADC are constructed by two paths of an I channel and a Q channel. The RF circuit can further include, although not illustrated inFIG. 2, an output unit for providing the calibration data to an external server.

According to an exemplary embodiment of the present invention, the first calibration can be carried out as described below.

Self-calibration on a chip of an RF circuit minimizes the use of an external equipment to shorten a required time. Because the external equipment is not used, generation and analysis of a signal for calibration are performed through a control block within the RF circuit. Here, the control block can be constructed as a digital circuit. For example, the control block includes the calibration controller210ofFIG. 2. The first calibration, which is a step of correcting a characteristic of the RF circuit and measuring the performance of the RF circuit, is carried out on the chip of the RF circuit.

FIG. 3illustrates a first calibration procedure in a communication device according to an exemplary embodiment of the present invention.

Referring toFIG. 3, in step301, an initial setting is carried out. The initial setting is a process of supplying power, a bias current and the like such that elements becoming calibration targets can operate. That is, before calibration is performed, a predefined bias current value is supplied to each analog and RF circuit.

After the initial setting is completed, in step303, calibration for a VCO is carried out. Here, the calibration for the VCO includes calibration for a transmission VCO and calibration for a reception VCO. For instance, the calibration for the VCO can be carried out as follows. The VCO outputs a reference signal, e.g., a frequency signal corresponding to an inputted voltage value. The frequency signal can include at least one of a square wave, a triangular wave, a sawtooth wave, a sine wave, etc. Therefore, the control block inputs a specific voltage value to the VCO, and determines whether an intended frequency signal is output. If the determination result is that the intended frequency signal and an outputted frequency signal are different from each other, the control block determines at least one compensation value for an inputted voltage value corresponding to a distortion of the outputted frequency signal.

If the calibration for the VCO is completed, in step305, a frequency for performing calibration for a TX/RX path is set. The RF circuit can be used in a plurality of frequency bands. According to the frequency bands, a distortion and noise characteristic needing calibration can appear different. In which frequency band an RF circuit is used after the RF circuit is installed in an MS is different according to which frequency band the MS supports. However, because the first calibration process is performed as independent RF-circuit calibration, it cannot be known whether the RF circuit is installed in an MS supporting which frequency band. Therefore, the first calibration is carried out for all frequency bands. As a result, calibration for each frequency band is iteratively performed. Therefore, the control block selects one frequency band for performing calibration. However, according to another exemplary embodiment of the present invention, only calibration for a partial frequency band can be carried out, if a frequency band to be supported by the RF circuit can be specified before the RF circuit is installed in the MS.

After the frequency is set, calibration of predefined items is performed for a transmission path and a reception path through step307to step311, which is described below. According to an exemplary embodiment of the present invention, the sequence of operations of steps included in step307to step311described below can be different.

In step307, calibration for transmission and reception gains is performed. In detail, calibration is performed for a maximum gain of the RF circuit and also, calibration is performed for matching a gain variance by a gain step defined for each gain control element within the RF circuit with a variance on design. For instance, for the sake of the calibration for the maximum gain, the control block grants a control signal for allowing the gain control element to grant the maximum gain, and determines if a maximum gain according to design is granted. If the result of the determination is that the intended maximum gain and a granted gain are different from each other, the control block determines at least one compensation value corresponding to an amount of difference for a transmission signal or a reception signal. Here, the control signal of the gain control element can be referred to as a ‘control word’. For example, for the sake of the calibration for the gain variance by gain step, the control block changes a control signal of each gain control element, provides a reference signal, and determines if a gain according to design is granted. If the determination result is that the intended gain and a granted gain are different from each other, the control block determines at least one compensation value corresponding to an amount of difference for a transmission signal or a reception signal. In the case of a transmission gain, the compensation value can be a pre-compensation value applied before being supplied to an analog and RF circuit and, in the case of a reception gain, the compensation value can be a post-compensation value applied after the reception signal is digitized.

In step309, calibration for TX/RX IQ mismatch is performed. For example, the control block outputs reference signals to each of an I-channel path and a Q-channel path, and determines the matching or mismatching of the reference signals passing through each of the I-channel path and the Q-channel path. For example, the control block can analyze signals mixed after passing through the I-channel path and Q-channel path and, in the analysis result, determine the matching or mismatching through the generation or non-generation of a signal of a specific frequency representing the TX/RX IQ mismatch. For example, the analysis can include envelope detection. If the mismatch occurs, the control block determines at least one compensation value corresponding to the amount of mismatch for a transmission signal or a reception signal. The compensation value can include at least one of a phase value and a magnitude value for an I-channel signal or a Q-channel signal.

In step311, calibration for a DC noise is performed. The calibration for the DC noise includes calibration for TX LO feed-through and calibration for RX DC-offset. The TX LO feed-through and the RX DC-offset represent a distortion adding a DC component noise in a signal processing process. For example, the control block outputs a reference signal, and determines the addition or non-addition of a DC noise. For example, to measure the TX LO feed-through, the control block can analyze a signal passing through a transmission path and, in the analysis result, determine the addition or non-addition of a DC noise through the generation or non-generation of a signal of a specific frequency representing the DC noise. For example, the analysis can include envelope detection. Also, to measure the RX DC-offset, the control block can analyze a signal passing through a reception path and, in the analysis result, determine the addition or non-addition of the DC noise through the generation or non-generation of a signal of a specific frequency representing the DC noise. If a DC noise is generated, the control block determines at least one compensation value corresponding to the DC noise for a transmission signal or a reception signal.

After the calibration of each item for the set frequency band of step305is completed in step311, in step313, it is determined whether calibration for all bands are completed. If the calibration for all bands is not completed, in other words, if an RF frequency not calibrated remains, step305and the subsequent steps are again performed. For example, after changing the frequency band setting as much as Δf in step305, the control block repeats subsequent step307to step311. Step305to step311are repeated for each frequency band and, by doing so, calibration data for all modes and all bands supported by the RF circuit are acquired. Whenever calibration for each frequency band is completed, calibration data can be stored in the form of a Look Up Table (LUT).

If it is determined in step313that the calibration for all bands is completed, in step315, calibration data for all bands are provided to an external server. At this time, in order to identify and index the RF circuit within the external server, the calibration data can be provided along with identification information of the RF circuit. For the sake of this, the RF circuit can have a memory recording the identification information.

According to an exemplary embodiment of the present invention, the resulting value of the first calibration can be managed as follows. Calibration data determined through the first calibration includes resulting values for all standards, all bands, and all modes. But, an MS is not designed to always support all bands. That is, a communication standard supported by the MS is fixed, and a supported band and mode can be different for every MS. In this case, if all calibration data determined through the first calibration are stored in a memory within a modem or RF circuit, even calibration data for a mode and a band not supported by the MS are stored. This causes a waste of memory due to the storing of unnecessary data and, as a result, becomes the cause of increasing a size of the modem or RF circuit. Particularly, if the modem or the RF circuit uses a non-volatile memory, the size increase becomes a bigger problem. As the kinds of the communication standards, the modes, and the bands supported by the RF circuit are increased, the extent of the size increase is increased accordingly. To fix the aforementioned data storage problem, the present exemplary embodiment uses the external server.

FIG. 4illustrates a procedure of managing calibration data in a communication device according to an exemplary embodiment of the present invention.

Referring toFIG. 4, in step401, a server receives and stores calibration data for all bands. The calibration data for all bands are determined in an RF circuit chip self-measurement process through the aforementioned first calibration. That is, resulting values for all standards, all modes, and all bands determined in the RF circuit chip self-measurement process through the first calibration are stored in the server.

After that, in step403, the server provides calibration data for at least one band supported by the communication device. That is, the server provides the calibration data for at least one band to the communication device. In other words, calibration data for a standard, a mode, and a band supported by the communication device in which an RF circuit is to be installed are downloaded from the server to the communication device. That is, after the server determines inputted identification information of an RF circuit and information indicating a selected band, the server outputs calibration data for the selected band among the determined calibration data of the RF circuit. Here, the information indicating the band can be replaced with information indicating a standard or information indicating a mode. For example, as the server receives a request from the communication device, the server can output calibration data for at least one band. For another example, according to a user's instruction through an input means, the server can output calibration data for at least one band.

According to an exemplary embodiment of the present invention, the second calibration can be carried out as follows. In the second calibration, the calibration data determined through the first calibration is used as raw calibration data for the chip. That is, the second calibration is performed in a state of storing only calibration data for a band supported by the communication device among the raw calibration data. According to this, it is not required to store measurement values for all bands in a memory of the communication device and thus, a memory size of the communication device can be reduced. A difference between the first calibration and the second calibration generated after an RF circuit chip is installed in the communication device is measured and, by using the measured difference between the first calibration and the second calibration, an offset value for the first calibration is determined.

FIG. 5illustrates a second calibration procedure in a communication device according to an exemplary embodiment of the present invention.

Referring toFIG. 5, in step501, calibration data for at least one band supported by the communication device is downloaded from a server. For example, for the sake of the download, the communication device can send a request for the calibration data to the server. In detail, the communication device determines identification information of an installed RF circuit, and outputs the identification information of the RF circuit and information indicating a band to the server. Here, the information indicating the band can be replaced with information indicating a standard or information indicating a mode. For another example, the download can be triggered according to a request from a device other than the communication device or according to a user's instruction through an input means of the server.

After the calibration data for the at least one band is downloaded in step501, in step503, initial setting is performed. The initial setting is a process of supplying power, a bias current and the like such that elements becoming calibration targets can operate. That is, before calibration is performed, a predefined bias current value is supplied to each analog and RF circuit.

After the initial setting is completed in step503, in step505, calibration for transmission maximum output is performed. At this time, the calibration is performed in a state where the calibration data downloaded from the external server is applied to the RF circuit. In detail, a transmission maximum output value of a state where an RF circuit and a modem interwork with each other is measured, and the measured transmission maximum output value is compared with a transmission maximum output value measured on a chip. If there is a difference between the two transmission maximum output values, calibration data for correcting the difference is determined. Next, in step507, calibration for a reception maximum gain is performed. That is, a reception maximum gain value of a state where the RF circuit and the modem interwork with each other is measured, and the measured reception maximum gain value is compared with a reception maximum gain value measured on the chip. If there is a difference between the two reception maximum gain values, calibration data for correcting the difference, i.e., a compensation value is determined.

After that, in step509, offset values for transmission and reception gain steps are determined. Unlike the first calibration, measurement for all gain steps is not performed, and an offset value for a difference between the first calibration and the second calibration to be commonly applied to all gain steps is determined. For example, after a control block of the modem performs measurement for any one gain step, the control block calculates a variance of a gain value compared to the maximum gain value measured in step507. If the calculated variance and a variance measured in the first calibration are different from each other, the control block determines at least one offset value corresponding to a difference of a variance for a transmission signal or a reception signal. The extent of the gain can be measured as a Root Mean Square (RMS). The offset value is identically applied to all gain steps.

FIG. 6is a block diagram illustrating a construction of a communication device according to an exemplary embodiment of the present invention.

Referring toFIG. 6, the communication device includes a modem610, an RF circuit620, and a Front End Module (FEM)630.

The modem610converts data into a baseband signal and provides the baseband signal to the RF circuit620. Also, the modem610converts a baseband signal provided from the RF circuit620, into data. The modem610is composed of a digital circuit. That is, a baseband signal processor612within the modem610performs modulation and demodulation of a signal, generation and analysis of an I-channel signal and a Q-channel signal and the like. The modem610includes a storage unit614. The storage unit614stores calibration data. According to an exemplary embodiment of the present invention, the storage unit614can store calibration data determined through second calibration. According to another exemplary embodiment of the present invention, the storage unit614can store calibration data determined through second calibration and calibration data determined through first calibration. In this case, upon booting of the communication device, the modem610provides the calibration data determined through the first calibration and stored in the storage unit614, to the RF circuit620. According to another exemplary embodiment of the present invention, the modem610can further include, although not illustrated inFIG. 6, a controller performing an operation for compensation using calibration data. Also, the controller can perform the calibration procedure illustrated inFIG. 5.

The RF circuit620converts a digital baseband signal provided from the modem610into an analog signal, and performs processing at an RF band. Also, the RF circuit620performs processing at an RF band for a received RF signal, converts the RF signal into a digital signal, and provides the digital signal to the modem610. The RF circuit620includes an RF signal processor622. The RF signal processor622includes at least one of a DAC, an ADC, a filter, a gain control element, an oscillator, and a mixer. Particularly, the RF circuit620includes a storage unit624storing calibration data. According to an exemplary embodiment of the present invention, the calibration data can be stored in the storage unit624at the time of fabrication of the communication device. According to another exemplary embodiment of the present invention, upon booting of the communication device, the storage unit624can receive the calibration data from the modem610. Also, the RF circuit620includes a calibration controller626for performing calibration and compensating a signal according to the calibration data. The RF circuit620can further include, although not illustrated inFIG. 6, an RF register for generating a physical signal controlling RF elements included in the RF signal processor622. Also, the RF circuit620can further include a feedback path for providing the calibration controller626with a result of processing the reference signal generated in the calibration controller626, in the RF signal processor622.

According to an exemplary embodiment of the present invention, the calibration controller626can perform calibration during a process of fabricating the communication device. According to another exemplary embodiment of the present invention, the calibration controller626can perform the calibration during an operation of the communication device. For example, the calibration performed during the operation of the communication device can be triggered by meeting a predefined condition (e.g., an instruction, a temperature, the lapse of a constant period and the like). If calibration data is determined through the calibration during the operation of the communication device, the calibration controller626stores the calibration data in at least one of the storage unit624within the RF circuit620and the storage unit614within the modem610. Or, the calibration data can be transmitted to the external server.

According to an exemplary embodiment of the present invention, the calibration controller626compensates a signal transceived during the operation of the communication device, by using the calibration data stored in the storage unit614. Here, a target of compensation includes at least one of a transmission signal, a reception signal, and a control signal controlling an element within the RF signal processor622. In other words, the calibration controller626controls at least one of a magnitude and a phase of at least one of a transmission signal and a reception signal, by using a compensation value included in the calibration data in order to compensate for a distortion generated in the RF signal processor622. For example, according to a required oscillation frequency, the calibration controller626compensates a voltage value inputted to a VCO and, according to a required amount of gain, the calibration controller626compensates a value of a transmission signal and a value of a reception signal.

The FEM630transmits an RF signal by a wireless channel through an antenna, and receives an RF signal by the wireless channel through the antenna. The FEM630can include a duplexer, a Power Amplifier (PA), a Low Noise Amplifier (LNA) and the like.

FIG. 7illustrates an operation procedure of a communication device according to an exemplary embodiment of the present invention.

Referring toFIG. 7, in step701, the communication device retrieves a compensation value corresponding to a current operation state, from calibration data stored in an RF circuit chip. The compensation value includes a compensation value for an input voltage according to an oscillation frequency of a VCO, a compensation value for a transmission signal or a reception signal according to an amount of gain, and the like. The calibration data is defined by band, mode, or standard supported by the communication device. That is, the communication device determines at least one compensation value corresponding to a current operation state (e.g., an oscillation frequency, a gain control extent and the like) among calibration data corresponding to a current operation band, a mode, or a standard.

After retrieving the compensation value corresponding to the current operation state in step701, the communication device proceeds to step703and compensates a signal according to the retrieved compensation value. In other words, the communication device controls at least one of a magnitude and a phase of at least one of a transmission signal and a reception signal, by using the compensation value so as to compensate for a distortion generated in the RF circuit. For instance, the communication device controls at least one of a phase of a transmission signal and a magnitude thereof according to the compensation value. For example, the communication device controls at least one of a phase of a reception signal and a magnitude thereof according to the compensation value. For example, the communication device controls an input power value of a VCO according to the compensation value.

According to another exemplary embodiment of the present invention, although not illustrated inFIG. 7, the communication device can store calibration data, which is stored in a modem upon initial booting, in a storage unit within the RF circuit chip. In this case, the storage unit within the RF circuit chip can be a volatile memory.

Also, the communication device can determine whether a predefined condition (e.g., an instruction, a temperature, the lapse of a constant period and the like) is met during operation and, if the condition is met, perform calibration for the RF circuit. At this time, the calibration, which is an RF circuit self-calibration, is performed using a signal generated in the RF circuit, and even signal analysis is performed within the RF circuit. In this case, the communication device stores calibration data determined through the calibration, in a storage unit within a modem or a storage unit within the RF circuit. Or, the communication device can transmit the calibration data to an external server.

By performing most of calibration for an RF circuit before the RF circuit is installed in an MS, in a state of minimizing the uncertainty of the RF circuit, the RF circuit is installed in the MS, and an item of calibration performed in an MS state is greatly reduced. This results in a cost and time savings for the calibration. Also, the calibration data determined through an independent RF-circuit calibration is stored in the external server, and only data for a standard, a mode, and a band supported by an MS in which the RF circuit is to be installed is downloaded, thereby minimizing a size of an RF circuit chip.

Embodiments of the present invention according to the claims and description in the specification can be realized in the form of hardware, software or a combination of hardware and software.

Such software may be stored in a computer readable storage medium. The computer readable storage medium stores one or more programs (software modules), the one or more programs comprising instructions, which when executed by one or more processors in an electronic device, cause the electronic device to perform methods of the present invention.