Method and apparatus for filtering a mobile high-definition link signal

A method and an apparatus perform Mobile High-definition Link (MHL) signal filtering. The method of performing the Mobile High-definition Link (MHL) signal filtering in a terminal includes determining whether a transmission device for MHL signal transmission is connected; determining whether a call continues when the transmission device is connected; and determining whether to perform the MHL signal filtering in the terminal based on whether the call continues. Accordingly, there is an advantage of improving picture quality of an image output from a multimedia device by effectively removing a common mode noise even when an RF weak electric field is formed due to call generation.

CLAIM OF PRIORITY

This application claims, pursuant to 35 U.S.C. §119(a), priority to and the benefit of the earlier filing date of Korean Application Serial No. 10-2012-0101588, which was filed in the Korean Intellectual Property Office on Sep. 13, 2012, the entire contents of which are hereby incorporated by reference.

BACKGROUND

1. Field of the Invention

The present invention relates generally to a method and an apparatus for filtering a signal, and more particularly, to a method and an apparatus for filtering a Mobile High-definition Link (MHL) signal.

2. Description of the Related Art

In the prior art, due to development of multimedia technology and communication technology, a terminal such as a smart phone or the like can transmit media to a relatively large size multimedia device such as a monitor, a television or the like. Accordingly, a user transmits media stored in the terminal to the relatively large size multimedia device in real time, and thus enjoys the media with the relatively large size multimedia device.

For high quality transmission of the media, a Mobile High-definition Link (MHL) technique has been developed. The MHL technique is a technique enabling compatibility between a micro Universal Serial Bus (USB) and a High Definition Multimedia Interface (HDMI).

As illustrated inFIGS. 1A-1D, the MHL technique can simultaneously transmit a common mode clock (CLK) component of 7.5 MHz and a differential mode data component of 2.2 Gbps by using a pair of differential signals. Accordingly, based on the MHL technique, the number of signals for media transmission is reduced, which corresponds to a greater advantage in allocating pins of a connector.

FIGS. 1A to 1Dillustrate examples for describing the MHL technique in the prior art.FIG. 1Aillustrates an example of a signal transmission circuit according to the MHL technique,FIG. 1Billustrates an example of an MHL signal according to the MHL technique,FIG. 1Cillustrates an example of a common mode clock component included in the MHL signal, andFIG. 1Dillustrates an example of a differential mode data component included in the MHL signal.

Since the MHL technique transmits a differential mode data component and a common mode clock component by using a pair of differential signals (hereinafter, referred to as an “MHL signal”), the common mode clock component is distorted when common mode noise flows in, and accordingly, an entire MHL signal is distorted. In particular, shaking of an output screen may be generated or the output screen may be turned off under an RF weak electric field.

In order to solve the above problems, a method of reinforcing shielding of a transmission device (for example, a dongle) is used for transmitting the MHL signal, but the method cannot achieve perfect blocking of the common mode noise.

Meanwhile, in order to satisfy a Radiated Emission (RE) standard, a common mode filter for blocking the common mode noise is applied to a terminal transmitting the MHL signal. However, even in this case, since an RF transmission signal generated in the terminal passes through the common mode filter employed in the terminal and then flows in the common mode clock, the common mode clock component will be distorted. It is because, while the common mode clock component is a signal switched to 400 mV, the RF transmission signal forming the RF weak electric field is a signal corresponding to a maximum of 10 V (33 dBm). Accordingly, even though some RF transmission signal flows in, the common mode clock component will be distorted, thereby resulting in distorting of the entire MHL signal.

SUMMARY

Accordingly, the present invention provides a method capable of effectively filtering an MHL signal.

Other objects desired to be provided in the present invention will be grasped through the following exemplary embodiments.

In accordance with an aspect of the present invention, a method of performing Mobile High-definition Link (MHL) signal filtering in a terminal is provided. The method including determining whether a transmission device for MHL signal transmission is connected; determining whether a call continues when the transmission device is connected; and determining whether to perform the MHL signal filtering in the terminal based on whether the call continues.

In accordance with another aspect of the present invention, a method of performing Mobile High-definition Link (MHL) signal filtering by a transmission device for MHL signal transmission is provided. The method includes receiving the MHL signal from a terminal; calculating a noise value included in the received MHL signal; and determining whether to perform the MHL signal filtering based on the calculated noise value.

In accordance with another aspect of the present invention, a method of performing Mobile High-definition Link (MHL) signal filtering by a transmission device for MHL signal transmission is provided. The method includes receiving a control signal for instructing whether to perform an MHL signal filtering from a terminal; and determining whether to perform the MHL signal filtering based on the received control signal.

In accordance with another aspect of the present invention an apparatus for performing Mobile High-definition Link (MHL) signal filtering in a terminal is provided. The apparatus includes a connection port connectable with a transmission device for MHL signal transmission; and a controller for determining whether a call continues when the transmission device is connected and performing the MHL signal filtering in the terminal based on whether call continues.

In accordance with another aspect of the present invention, an apparatus for performing Mobile High-definition Link (MHL) signal filtering in a transmission device for MHL signal transmission is provided. The apparatus includes a connection port for receiving an MHL signal, the connection port being connected to a terminal; a controller for calculating a noise value included in the received MHL signal and determining whether to perform the MHL signal filtering based on the calculated noise value; and a filter unit for performing the MHL signal filtering under a control of the controller.

In accordance with another aspect of the present invention, an apparatus for performing Mobile High-definition Link (MHL) signal filtering in a transmission device for MHL signal transmission is provided. The apparatus includes a connection port for receiving an MHL signal and a control signal for instructing whether to perform the MHL signal filtering, the connection port being connected to a terminal; a controller for determining whether to perform the MHL signal filtering based on the received control signal; and a filter unit for performing the MHL signal filtering under a control of the controller.

According to the present invention, there is an advantage of improving a picture quality of an image output from a multimedia device by effectively removing common mode noise even when an RF weak electric field due to call generation is formed.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, a detailed explanation of known related functions and constructions may be omitted to avoid unnecessarily obscuring the subject matter of the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. In addition, terms described herein, which are defined with reference to the functions of the present invention, may be implemented differently depending on a user or operator's intention and practice. Therefore, the terms should be understood on the basis of the disclosure throughout the specification. The principles and features of this invention may be employed in varied and numerous embodiments without departing from the scope of the invention.

The same reference numbers are used throughout the drawings to refer to the same or like parts. Furthermore, although the drawings represent exemplary embodiments of the invention, the drawings are not necessarily to scale and certain features may be exaggerated or omitted in order to more clearly illustrate and explain the present invention.

As described above, the MHL signal filtering method in the prior art cannot effectively block a distortion of the common mode clock component. In particular, a signal distortion under an RF weak electric field causes a serious distortion of an output screen.

Accordingly, the present invention provides a method of blocking a distortion of the common mode clock component of the MHL signal. Specifically, the present invention provides a method of filtering the MHL signal by simultaneously applying a filtering apparatus for filtering the MHL signal to both a media device and a transmission device such as a dongle or the like.

Meanwhile, as described above, a filter for filtering common mode noise is applied to a terminal in the prior art in order to satisfy an RE standard. At this time, filtering the MHL signal in the transmission device such as the dongle or the like other than the media device is contrary to an MHL specification. Accordingly, a method of satisfying both the RE standard and the MHL specification is required.

In the RE standard, whether to satisfy a reference is an issue when in a state where a call is not connected, and an MHL signal distortion issue is generated in a state where the call is connected. Accordingly, the exemplary embodiments of the present invention provide the method of satisfying both the RE standard and the MHL specification separately in the state where the call is connected and the state where the call is not connected.

That is, the present invention provides the method in which the terminal filters the MHL signal in the state where the call is not connected and the transmission device such as the dongle or the like filters the MHL signal in the state where the call is connected.

According to the present invention, there are advantages of satisfying both the RE standard and the MHL specification and effectively removing the common mode noise.

Hereinafter, in a description of the exemplary embodiments of the present invention, a device such as the dongle or the like, which receives the MHL signal from the terminal, converts the received MHL signal to an HDMI signal and then transmits the HDMI signal to a multimedia device, is referred to as the transmission device.

Hereinafter, the exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

First, an MHL signal filtering apparatus according to the exemplary embodiments of the present invention will be described with reference toFIGS. 2A and 2B.FIGS. 2A and 2Bare block diagrams for describing the MHL signal filtering apparatus according to the exemplary embodiments of the present invention.

As described above, in the exemplary embodiments of the present invention, each of a terminal210and a transmission device220have a common mode filter which uses known methods for filtering common mode noise from signals. Further, according to whether an RF weak electric field is formed, the terminal210or the transmission device220performs MHL signal filtering. The two cases are separately described.

Referring first toFIG. 2A,FIG. 2Aillustrates the case where the RF weak electric field is not formed. That is, in the state where the call is not generated, the terminal210turns on the common mode filter for filtering the MHL signal, and the transmission device220turns off the common mode filter for filtering the MHL signal.

As described above, the MHL signal filtering in both the terminal210and the transmission device220is contrary to the MHL specification. However, as illustrated inFIG. 2A, the MHL specification is satisfied when the terminal210performs the MHL filtering and the transmission device220does not perform the MHL signal filtering in the state where the call is not generated. Further, in this case, the RE standard is satisfied.

Meanwhile, referring toFIG. 2B,FIG. 2Billustrates the case where the RF weak electric field is formed. That is, in the state where the call is generated, the terminal210turns off the common mode filter for filtering the MHL signal, and the transmission device220turns on the common mode filter for filtering the MHL signal.

As illustrated inFIG. 2B, when the terminal does not perform the MHL signal filtering and the transmission device220performs the MHL signal filtering in the state where the call is generated, there are advantages in that the MHL specification is satisfied and a signal distortion due to the RF weak electric field is reduced.

In the above description, the MHL signal filtering apparatus according to the exemplary embodiments of the present invention has been discussed with reference toFIGS. 2A-2B. Hereinafter, an MHL signal filtering apparatus according to the exemplary embodiment of the present invention will be described with reference toFIG. 3.

FIG. 3is a block diagram for describing the MHL signal filtering apparatus ofFIGS. 2A-2Bin greater detail according to the exemplary embodiment of the present invention.FIG. 3illustrates the terminal210for transmitting the MHL signal and the transmission device220for receiving the MHL signal from the terminal210, converting the MHL signal to a HDMI signal, and then transmitting the HDMI signal to a multimedia device, as shown inFIGS. 2A-2B.

First, a configuration of the terminal210will be described. Referring toFIG. 3, the terminal210according to the exemplary embodiment of the present invention includes a controller212, an MHL signal transmitter214, a common mode filter216, and a connection port218.

The controller212determines whether the transmission device220is connected. That is, when a set signal is received from the transmission device220through the connection port218, it is recognized that the transmission device220is connected.

Further, the controller212controls the MHL signal transmitter214such that media selected by a user is converted to the MHL signal and then the MHL signal is output.

In addition, the controller212controls an on/off state of the common mode filter216. At this time, the controller212controls the on/off state of the common mode filter216by determining whether the RF weak electric field is formed on the terminal210. In the exemplary embodiment, the fact of whether the RF weak electric field is formed may be determined by whether the call is generated. For example, it is determined that the RF weak electric field is formed when the call is generated, and it is determined that the RF weak electric field is not formed when the call is terminated. To this end, the controller212may receive a signal for determining whether the call is generated or terminated from a transceiver connected to or included in the controller212for transmitting and receiving an RF signal. Accordingly, the controller212turns on the common mode filter216located in the terminal210when it is determined that the call is not generated in the terminal210, and turns off the common mode filter216located in the terminal210when it is determined that the call is generated. Further, when it is determined that the call is generated, the controller212generates a control signal and transmits the control signal to the transmission device220so that the common mode filter226located in the transmission device220is turned on. In addition, after the call is generated in the terminal210, it is determined whether the call is terminated. When it is determined that the call is terminated, the controller212turns on the common mode filter216located in the terminal210, and generates a control signal for instructing to turn off the common mode filter226located in the transmission device220and transmits the control signal to the transmission device220.

In the exemplary embodiment, the control signal for instructing to turn on or turn off the common mode filter of the transmission device220may be transmitted using an NC pin.

Referring back toFIG. 3, the MHL signal transmitter214converts media selected by the user to the MHL signal and transmits the MHL signal to the common mode filter216under a control of the controller212.

The common mode filter216in an on state filters the MHL signal received from the MHL signal transmitter214. That is, the common mode filter216performs filtering for removing a common mode noise component. The on/off state of the common mode filter216is controlled by the controller212.

The connection port218is connected to a connection port228aof the transmission device220and is used for transmitting a signal for recognition of the connection between the terminal210and the transmission device220, the MHL signal, and the control signal.

Hereinafter, a configuration of the transmission device220will be described. Referring toFIG. 3, the transmission device220according to the exemplary embodiment of the present invention includes connection ports228aand228b, the common mode filter226, and an MHL to HDMI converter224.

The connection port218ais connected to the connection port218of the terminal210and used for transmitting the signal indicating recognition of the connection between the terminal210and the transmission device220, the MHL signal, and the control signal.

The common mode filter226in an on state filters the MHL signal received from the terminal210. That is, the common mode filter226performs filtering for removing the common mode noise component. The on/off state of the common mode filter226is controlled by the control signal received from the terminal210. That is, the common mode filter226is turned on when the control signal for instructing to turn on the common mode filter226is received from the terminal210, and the common mode filter226is turned off when the control signal for instructing to turn off the common mode filter226is received from the terminal210. To this end, the common mode filter226may include a switch therein for changing the on/off state of the common mode filter226according to the control signal received from the terminal210. Alternatively, a switch located may be included in a front end or a rear end of the common mode filter226to change the on/off state of the common mode filter226according to the control signal received from the terminal210.

The MHL to HDMI converter224converts the MHL signal received from the common mode filter226to the HDMI signal and outputs the HDMI signal to the connection port228b.

The connection port228bmay be connected to a multimedia device for an HDMI image output and used for transmitting the HDMI signal received from the MHL to HDMI converter224to the multimedia device.

In the above description, the MHL signal filtering apparatus according to the exemplary embodiment of the present invention has been discussed with reference toFIG. 3. Meanwhile, as described with reference toFIG. 3, the terminal210may control the on/off state of the common mode filter226located in the transmission device220, but the transmission device220may directly control the on/off control of its own common mode filter226according to alternative exemplary embodiments. The exemplary embodiments will be described below with reference to associated drawings.

FIG. 4is a block diagram for describing an MHL signal filtering apparatus according to an alternative exemplary embodiment of the present invention. In the alternative exemplary embodiment described with reference toFIG. 4, a description of the same components as those ofFIG. 3will be omitted as necessary.

First, the configuration of the terminal210will be described. Referring toFIG. 4, the terminal210according to the alternative exemplary embodiment of the present invention includes the controller212, the MHL signal transmitter214, the common mode filter216, and the connection port218.

Operations of the terminal210in the alternative exemplary embodiment ofFIG. 4are the same as those described with reference toFIG. 3except that the controller212does not generate the control signal for controlling the common mode filter226located in the transmission device220and so the control signal is not transmitted. Accordingly, a detailed description of the terminal210is herein omitted.

Hereinafter, the configuration of the transmission device220will be described. Referring toFIG. 4, the transmission device according to the alternative embodiment of the present invention includes the connection ports228aand228b, the common mode filter226, and the MHL to HDMI converter224.

The alternative exemplary embodiment ofFIG. 4is different from the exemplary embodiment ofFIG. 3in that another controller222is formed within the MHL to HDMI converter224inFIG. 4. Unlike the exemplary embodiment described with reference toFIG. 3, in the alternative exemplary embodiment illustrated inFIG. 4, the transmission device220does not receive the control signal for controlling the on/off state of the common mode filter226from the terminal210, but directly controls the on/off state of the common mode filter226using the controller222. Since other operations of the alternative exemplary embodiment ofFIG. 4are the same as those described with reference toFIG. 3, detailed descriptions thereof will be herein omitted. Hereinafter, only a configuration ofFIG. 4where the transmission device220directly controls the on/off state of the common mode filter226will be described.

The transmission device220according to the alternative exemplary embodiment of the present invention includes the controller222formed within the MHL to HDMI converter224to control the on/off state of the common mode filter226.

The controller222calculates a noise value included in the input MHL signal and determines whether to filter the MHL signal based on the calculated noise value. For example, it is determined to perform the MHL signal filtering when the calculated noise value is equal to or greater than a predetermined setting value, and it is determined not to perform the MHL signal filtering when the calculated noise value is less than the predetermined setting value. Further, the controller222controls the on/off state of the common mode filter226according to the determination. To this end, a switch for changing the on/off state of the common mode filter226may be included within the common mode filter226or between the common mode filter226and the controller222.

The noise value included in the MHL signal may be calculated through various known methods. For example, the controller222may use a fast Fourier Transform (FFT) technique known in the art for calculating the noise value. That is, the received MHL signal is fast Fourier transformed, and a noise value of the fast Fourier transformed MHL signal may be calculated. Further, when a noise value of the fast Fourier transformed MHL signal in a particular bandwidth is equal to or greater than a predetermined setting value, it is determined to perform the MHL signal filtering and accordingly, the common mode filter226may be turned on. For example, when a noise value of the fast Fourier transformed MHL signal in a bandwidth of 1 GHz to 2 GHz is equal to or greater than the predetermined setting value, the controller222determines to perform the MHL signal filtering. Otherwise, the controller222may determine not to perform the MHL signal filtering.

Further, the controller222continuously measures the noise value of the MHL signal while the common mode filter226is in the on state, and identifies whether the measured noise value is less than the predetermined setting value. Such an operation may be performed every set period having a predetermined and repeated time duration. The noise value less than the predetermined setting value indicates that the call is terminated in the terminal210. When the call is terminated in the terminal210, the common mode filter216located in the terminal210is turned on and thus the controller222turns off the common mode filter226of the transmission device220as described above. Accordingly, the MHL specification is satisfied.

In the alternative exemplary embodiment described with reference toFIG. 4, since the control signal transmitted to the transmission device220from the terminal210to filter the MHL signal is not necessary, the processing to perform the signaling may be reduced or eliminated in comparison with the exemplary embodiment described with reference toFIG. 3.

Meanwhile, in the alternative exemplary embodiment described with reference toFIG. 4, it has been described that the common mode filter226is located in the front end of the MHL to HDMI converter224, but in another alternative embodiment shown inFIG. 5, the common mode filter226may be located within the MHL to HDMI converter224. That is, the common mode filter226may be integrally formed with the MHL to HDMI converter224, which will be described inFIG. 5. Since the operations of components illustrated inFIG. 5are the same as those described with reference toFIG. 4, detailed descriptions thereof will be omitted.

In the above description, the MHL signal filtering apparatus according to exemplary embodiments of the present invention has been discussed with reference toFIGS. 3 to 5. Hereinafter, an MHL signal filtering process according to exemplary embodiments of the present invention will be described with reference to associated drawings.

FIG. 6is a flowchart for describing an MHL signal filtering process according to the exemplary embodiment of the present invention. InFIG. 6, the flowchart is described based on operations performed in the terminal210shown inFIG. 3.

In step601, the terminal210determines whether the transmission device220for transmitting the MHL signal is connected, and proceeds to step603when it is determined that the transmission device220is connected. Otherwise, the process loops back repeatedly to perform step601until the transmission device220is detected to be connected.

In step603, the terminal210determines whether the call continues. At this time, the call continuity refers to a case where a generated existing call continues and a case where a new call is generated. When it is determined in step603that the call does not continue, the terminal210proceeds to step613to start the MHL signal filtering. However, when it is determined in step603that the call continues, the terminal210proceeds to step605.

The terminal210generates the control signal for instructing to start the MHL signal filtering, and transmits the control signal to the transmission device220in step605performed as a result of the determination in step603, which is a determination that the call continues. After step605, the process then proceeds to step607.

The terminal210terminates the MHL signal filtering in step607, and then proceeds to step609. That is, in step607, the terminal terminates the MHL signal filtering when an existing MHL signal filtering is being performed, and maintains the state when the existing MHL signal filtering is not being performed.

The order of steps605and607may be switched or performed at the same time.

In step609, the terminal210determines whether the call is terminated. The terminal210proceeds to step611when it is determined that the call is terminated, or proceeds to step607to maintain the MHL signal filtering stop state when it is determined in step609that the call is not terminated.

In step611, the terminal210generates the control signal for instructing the transmission device220to terminate the MHL signal filtering, transmits the control signal to the transmission device220, and then proceeds to step613.

In step613, the terminal210starts the MHL signal filtering, and loops back to step603.

The order of steps611and613may be switched or performed at the same time.

In the above description, the MHL signal filtering operation performed in the terminal210according to the exemplary embodiment of the present invention has been discussed with reference toFIG. 6. Hereinafter, an MHL signal filtering operation performed in the transmission device220ofFIG. 3according to the exemplary embodiment of the present invention will be described with reference toFIG. 7.

FIG. 7is a flowchart for describing the MHL signal filtering operation performed in the transmission device220according to the exemplary embodiment of the present invention. The operations of the transmission device220illustrated inFIG. 7are operations performed in accordance with the operations of the terminal210described with reference toFIG. 6.

In step701, the transmission device220determines whether the control signal is received from the terminal210, and proceeds to step703when it is determined that the control signal is received. Otherwise, the process loops back repeatedly to perform step701until a control signal is received.

In step703, the transmission device220analyzes the received control signal, and then proceeds to step705.

In step705, the transmission device220determines whether the analyzed control signal is a signal for instructing to start or terminate the MHL signal filtering. As a result of the determination in step705, when the analyzed control signal is the signal for instructing to start the MHL signal filtering, the transmission device220proceeds to step707to start the MHL signal filtering, and the process loops back to step701.

Meanwhile, as a result of the determination in step705, when the analyzed control is the signal for instructing to terminate the MHL signal filtering, the transmission device220proceeds to step709to terminate the MHL signal filtering, and the process loops back to step701.

In the above description, the MHL signal filtering operations performed in the terminal210and the transmission device220according to the exemplary embodiment of the present invention have been discussed with reference toFIGS. 6 and 7. Hereinafter, an MHL signal filtering operation according to the alternative exemplary embodiment of the present invention will be described with reference to associated drawings.

FIG. 8is a flowchart for describing an MHL signal filtering process according to the alternative exemplary embodiment of the present invention. InFIG. 8, the flowchart is described based on the operations performed in the terminal210for the apparatus ofFIGS. 4-5.

The terminal210determines in step801whether the transmission device220for transmitting the MHL signal is connected, and proceeds to step803when it is determined that the transmission device220is connected. Otherwise, the process loops back repeatedly to perform step801until a control signal is received.

In step803, the terminal210determines whether the call continues. At this time, the call continuity refers to a case where a generated existing call continues and a case where a new call is generated. The terminal210proceeds to step809to start the MHL signal filtering when it is determined in step803that the call does not continue, and proceeds to step805when it is determined in step803that the call continues.

The terminal210terminates the MHL signal filtering in step805performed by a result of the determination in step803, which is a determination that the call continues, and then proceeds to step807. That is, in step805, the terminal210terminates the MHL signal filtering when an existing MHL signal filtering is being performed, and maintains the state when the existing MHL signal filtering is not being performed.

The terminal210determines whether the call is terminated in step807. The terminal210proceeds to step809when it is determined in step807that the call is terminated, and proceeds to step805to maintain the MHL signal filtering stop state when it is determined in step807that the call is not terminated.

In step809, the terminal210starts the MHL signal filtering, and loops back to step803.

In the above description, the MHL signal filtering operation performed in the terminal210according to the alternative exemplary embodiment of the present invention has been discussed with reference toFIG. 8. Hereinafter, the MHL signal filtering operation performed in the transmission device220according to another alternative embodiment of the present invention will be described with reference toFIG. 9.

FIG. 9is a flowchart for describing the MHL signal filtering operation performed in the transmission device220according to the alternative exemplary embodiment of the present invention shown inFIGS. 4-5. The operations of the transmission device220illustrated inFIG. 9are operations performed in accordance with the operations of the terminal210described with reference toFIG. 8.

The transmission device220determines whether the MHL signal is received from the terminal in step901. When it is determined that the MHL signal is received, the transmission device220proceeds to step903. Otherwise, the process loops back repeatedly to perform step901until an MHL signal is received.

The transmission device220performs the FFT on the received MHL sign in step903, and then proceeds to step905.

The transmission device220calculates a noise value of the fast Fourier transformed MHL signal in step905, and then proceeds to step907.

The transmission device220compares the calculated noise value with a predetermined setting value in step907. When the calculated noise value is equal to or greater than the predetermined setting value, the transmission device220proceeds to step909. Otherwise, the transmission device220proceeds to step911. For example, in step907, the transmission device220compares a power value in a particular bandwidth of the fast Fourier transformed MHL signal, for example, a bandwidth of 700 MHz used in Long Term Evolution (LTE) communication or a bandwidth of 900 MHz used in Global System for Mobile (GSM) communication, with the predetermined setting value, and performs a next operation in steps909,911according to a result of the comparison.

The calculated noise value equal to or greater than the predetermined setting value indicates that the RF weak electric field is formed due to the call generation in the terminal210and thus an MHL signal distortion is generated.

When step909is performed by a result of the determination in step907which is a determination that the calculated noise value is equal to or greater than the predetermined setting value, the transmission device220starts the MHL signal filtering in step909.

Meanwhile, when step911is performed by a result of the determination in step907which is a determination that the calculated noise value is less than the predetermined setting value, the transmission device220terminates the MHL signal filtering in step911.

After the operations in steps909and911, the transmission device220proceeds to step903and continuously performs the FFT for calculating the noise value in order to determine whether to perform the MHL signal filtering. The FFT may be performed in every set period having a predetermined and repeated time duration.

In the above description, the MHL signal filtering operations performed in the terminal210and the transmission device220according to the alternative exemplary embodiments of the present invention have been discussed with reference toFIGS. 8 and 9. Hereinafter, an effect of the MHL signal filtering according to exemplary embodiments of the present invention will be described with reference to associated drawings.

FIG. 10illustrates an MHL signal filtering effect in a state where the common mode filter226is applied to the transmission device220according to exemplary embodiments of the present invention.

For implementing the present invention, tests have been performed in frequency bands of Personal Communication Systems (PCS)1900, GSM900, and Digital Cellular Service (DCS)1800in an electric field area ranging from −65 dBm to −70 dBm and a Transverse Electro Magnetic (TEM) cell. Further, the tests have been performed with impedances of 12, 35, 50, and 90 ohm of the common mode filter applied to the transmission device220.

As illustrated inFIG. 10, when the common mode filter226is not applied, the MHL signal filtering is below the standard. That is, a screen output is not normally performed.

Meanwhile, when impedance of the common mode filter226is equal to or greater than 50 ohm, the MHL signal filtering satisfies the standard in all frequency bands. Accordingly, in order to meet the standard in all frequency bands, it is preferable to set an impedance of the common mode filter226to a value equal to or greater than 35 ohm. However, when the impedance of the common mode filter226is too high, a signal distortion due to the high impedance may be generated, and thus it is preferable to set the impedance of the common mode filter226to a value ranging from 35 to 50 ohm.

FIGS. 11A and 11Billustrate a signal state improved by applying the common mode filter226to the transmission device220according to exemplary embodiments of the present invention.

FIGS. 11A and 11Bshow a test result performed in a weak electric field environment of 33 dBm,FIG. 11Ashows a test result according to the filtering method in the prior art, andFIG. 11Bshows a test result according to the filtering method according to exemplary embodiments of the present invention.

Referring toFIG. 11A, the MHL_CLK spectrum in a frequency band of 225 MHz in the prior art corresponds to 0.177 dBm. Referring toFIG. 11B, the MHL_CLK spectrum in the same frequency band of 225 MHz for the present invention corresponds to −0.191 dBm. Accordingly, an effect has been improved by the present invention in comparison with the filtering method in the prior art.

Further, referring toFIG. 11A, the MHL_CLK spectrum in a frequency band of 1.8 GHz in the prior art corresponds to −5.373 dBm. Referring toFIG. 11B, MHL_CLK spectrum in the same frequency band of 1.8 GHz in the present invention corresponds to −15.127 dBm, which indicates that an effect has been improved in comparison with the filtering method in the prior art.

The above described exemplary embodiments of the present invention may be implemented in various methods. For example, the exemplary embodiments of the present invention may be implemented using hardware, software, or a combination thereof. When the exemplary embodiments of the present invention are implemented using software, the software may be executed on one or more processors using various operating systems or platforms. Additionally, the software may be configured using any of a plurality of appropriate programming languages, and may be compiled using a framework, an executable machine language executed in a virtual machine, or an intermediate code.

Further, when the exemplary embodiments of the present invention are executed on one or more processors, the exemplary embodiments may be implemented by a processor readable medium (for example, a memory, a floppy disk, a hard disk, a compact disk, an optical disk, a magnetic disk or the like) recording one or more programs to perform a method of implementing various exemplary embodiments of the present invention.

The above-described apparatus and methods according to the present invention can be implemented in hardware or firmware, or as software or computer code, or combinations thereof. In addition, the software or computer code can also be stored in a non-transitory recording medium such as a CD ROM, a RAM, a ROM whether erasable or rewritable or not, a floppy disk, CDs, DVDs, memory chips, a hard disk, a magnetic storage media, an optical recording media, or a magneto-optical disk or computer code downloaded over a network originally stored on a remote recording medium, a computer readable recording medium, or a non-transitory machine readable medium and to be stored on a local recording medium, so that the methods described herein can be rendered in such software, computer code, software modules, software objects, instructions, applications, applets, apps, etc. that is stored on the recording medium using a general purpose computer, a digital computer, or a special processor or in programmable or dedicated hardware, such as an ASIC or FPGA. As would be understood in the art, the computer, the processor, microprocessor controller or the programmable hardware include volatile and/or non-volatile storage and memory components, e.g., RAM, ROM, Flash, etc. that may store or receive software or computer code that when accessed and executed by the computer, processor or hardware implement the processing methods described herein. In addition, it would be recognized that when a general purpose computer accesses code for implementing the processing shown herein, the execution of the code transforms the general purpose computer into a special purpose computer for executing the processing shown herein. In addition, the program may be electronically transferred through any medium such as communication signals transmitted by wire/wireless connections, and their equivalents. The programs and computer readable recording medium can also be distributed in network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

Although the detailed exemplary embodiments of the present invention have been discussed in the description of the present invention, various modifications can be made without departing from the scope of the present invention. Therefore, the present invention is not limited to the above-described exemplary embodiments but defined by the appended claims and the equivalents thereof.