KR100664256B1 - An apparatus for improving receive sensitivity of digital multimedia broadcasting - Google Patents

Abstract

An apparatus for improving the receive sensitivity of a DMB(Digital Multimedia Broadcasting) is provided to improve receive sensitivity by using a diversity technique when a mobile terminal having a single antenna receives a DMB signal. When the quality of a reception signal is lower than a reference level, the first RFIC(Radio Frequency Integrated Circuit) unit(60) controls the gain of an RF(Radio Frequency) signal and converts it into an IF(Intermediate Frequency) signal. When the quality of a reception signal is greater than the reference level, the second RF IC unit(70) controls the gain of an RF signal and converts it into an IF signal. A baseband unit(80) receives the IF signals of the first and second RF IC units(60,70), and restore them.

Description

Device for improving reception sensitivity of digital multimedia broadcasting {AN APPARATUS FOR IMPROVING RECEIVE SENSITIVITY OF DIGITAL MULTIMEDIA BROADCASTING}

1 is a block diagram of a conventional DMB terminal.

2 is a block diagram of a DMB terminal according to the present invention;

** Description of the symbols for the main parts of the drawings **

10: antenna 20: low noise filter

30: tracking filter 40: first variable amplifier

50: second variable amplifier 60: first RF IC

70: second RF IC 80: baseband portion

81: analog-to-digital converter 82: buffer

The present invention relates to an apparatus for improving reception sensitivity of a digital multimedia broadcasting, and more particularly, to an apparatus for improving reception sensitivity of a digital multimedia broadcasting using a diversity technique in a terminal equipped with one antenna.

DMB (Digital Multimedia Broadcasting) is a new title for DAB (Digital Audio Broadcasting), commercially available in Europe and the United States for mobile TV. Whereas DAB refers to audio-oriented digital radio broadcasting, DMB extends the concept of digital radio broadcasting to 'seeing and listening' multimedia broadcasting. The Ministry of Information and Communication recently renamed the DAB to DMB to take advantage of the features of multimedia broadcasting, and it is divided into free terrestrial DMB and satellite DMB, which is to be paid for, depending on the use of satellites and service bands.

The satellite DMB provides a multimedia broadcasting service including audio, additional data, or video to a fixed and mobile portable receiver through a satellite. It is a next-generation service that can provide a wide range of quality audio broadcasting services at low cost and use satellites to greatly expand the audible range of existing broadcasting by covering a large area. In the age of convergence of telecommunication and broadcasting, it has emerged as a representative service of 'digital convergence'.

In addition, the terrestrial DMB is a mobile multimedia broadcasting service capable of providing high quality voice and video services anytime and anywhere, thereby extending the concept of radio broadcasting from 'hearing broadcast' to 'viewing and listening broadcast'. Based on excellent mobile reception characteristics, various contents such as music, text and video are delivered through portable terminals such as small TVs and PDAs. In addition, by establishing a complementary relationship with digital terrestrial TV broadcasting pursuing high quality and high sound quality, it is possible to create a breakthrough demand for mobile terminals through combined services with PDAs and mobile communication terminals.

The terrestrial DMB system transmits a 200MHz band broadcasting signal from the terrestrial broadcasting relay station, and the transmitted broadcasting signal propagates through the air and is attenuated by geographic obstacles such as buildings, houses, and mountains. Occurs. The signals reflected and diffracted by such obstacles do not propagate through one path, but propagate through several paths. Since the lengths of the paths of the signals radiated from the broadcast repeaters are different from each other, a difference in time to reach the DMB terminal occurs, and different attenuation and phase differences occur for each signal reached. The DMB terminal should receive all of these multipath signals at the base station in order to output the broadcast image. However, when the DMB terminal receives multiple signals having different attenuation and phase difference, the amplitude of the received signal increases and decreases. This phenomenon is called multipath fading. If the multipath fading occurs severely, the stability of the wireless network is degraded and the broadcasting is interrupted. Therefore, a technique for reducing multipath fading is essential in a mobile communication system.

In particular, since the terrestrial DMB system is limited to one broadcast repeater, many weak electric field environments in which a broadcast signal does not reach far away from the broadcast repeater are generated.

1 illustrates a configuration of a terrestrial DMB terminal according to the prior art, and the illustrated DMB terminal receives a terrestrial broadcast signal, which is an RF signal of a 200 MHz band, through a terrestrial DMB antenna, and filters and signals through a tuner. After amplification and conversion to IF signal, it is transmitted to the TDMB baseband stage. The tuner generally includes an amplifier for amplifying an RF signal, a tracking filter for selecting a channel to which the signal is to be transmitted, and an integrated chip (IC) for converting an RF signal transmitted through the selected channel into an IF signal. The TDMB baseband terminal receiving the IF signal from the tuner A / D converts the IF signal to restore the broadcast signal.

Since the terrestrial DMB terminal configured as described above does not use a diversity scheme, broadcast reception sensitivity is low. In order to alleviate the multipath fading phenomenon in the mobile communication system, a diversity scheme is used at the base station. The basic concept of the diversity scheme is to obtain a plurality of fading waves using two reception antennas at the receiving end. Obtaining multiple fading waves in diversity reception is in addition to making an independent transmission path between the transmitter and the receiver. That is, the signals received by the two receiving antennas need to receive completely different signals. In this case, even if a deep fading phenomenon occurs in a signal received at one antenna, a small fading phenomenon occurs in a signal received at the other antenna, so that a signal can be reproduced by selecting a small fading signal.

However, the DMB terminal using the conventional diversity technique has a limitation in that two or more antennas should be mounted on the DMB terminal in order to increase reception sensitivity of digital multimedia broadcasting.

The present invention has been proposed to solve the above problems, and an object of the present invention is to further include an RF IC for converting an RF signal to an IF signal, when distortion may occur in signal recovery due to fading. The present invention provides an apparatus for improving the sensitivity of digital multimedia broadcasting reception by restoring a broadcast signal by an added RF IC.

In order to achieve the above object, in the terminal for receiving a digital multimedia broadcasting signal, the apparatus for improving the reception sensitivity according to the present invention, when the quality of the received signal is less than the reference to adjust the gain of the RF signal to the IF signal A first RF IC unit for converting, a second RF IC unit for adjusting the gain of the RF signal and converting it into an IF signal when the quality of the received signal is higher than a reference, and an IF signal of the first RF IC unit or the second RF IC unit Characterized in that consisting of the baseband unit for receiving and restoring the input.

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

2 illustrates a configuration of a DMB terminal according to the present invention. As shown in FIG. 2, an antenna 10 for receiving a digital multimedia broadcasting signal having a radio frequency (RF) and a low noise for amplifying the RF signal are illustrated in FIG. A low noise amplifier (LNA) 20, a tracking filter 30 for searching and selecting a channel for transmitting the RF signal, and a variable gain for the RF signal transmitted through the selected channel. A first variable amplifier 40 and a second variable amplifier 50 for amplifying a signal, a first RF IC 60 and a second RF IC 70 for converting the RF signal into an IF signal, and the first RF The baseband unit 80 converts the IF signal received from the IC or the second RF IC into an image signal outputable on the screen.

The antenna 10 may receive an RF digital multimedia broadcasting signal of about 200 Hz, and unlike other DMB terminals having a plurality of antennas for using a diversity scheme, the DMB terminal according to the present invention uses one antenna. do.

The first variable amplifier 40 and the second variable amplifier 50 amplify a signal received through the selected channel through the tracking filter 30 and adjust the gain according to the size of the received signal to variably. Can be amplified.

The first RF IC 60 and the second RF IC 70 respectively output a radio frequency (RF) signal amplified by the first variable amplifier 40 and the second variable amplifier 50, respectively. A signal is formed and forms an interface between the baseband unit 80 and a processor (not shown) for controlling the first RF IC and the second RF IC. The operation of the first RF IC 60 and the second RF IC 70 is determined by the control signals control_1 and control_2 of the processor that generally controls the DMB terminal.

The processor may recognize that a fading phenomenon occurs, and when a fading phenomenon occurs, the operation of the auto gain control (AGC) of the first RF IC 60 is stopped and the gain is constant. Generate a control_1 signal to maintain and a control_2 signal to cause the second RF IC 70 to perform AGC. Here, the processor recognizes that a fading phenomenon occurs when the power strength of the received RF signal is smaller than a threshold set in the DMB terminal. However, when the power intensity of the RF signal received by the DMB terminal is not smaller than the threshold value, the processor recognizes that no fading phenomenon occurs and causes the first RF IC 60 to perform an AGC and a control_1 signal. In addition, the control unit generates a control_2 signal to prevent the second RF IC 70 from being driven. The processor simultaneously transmits a control_1 signal that causes the first RF IC 60 to perform an AGC function and a control_2 signal that does not drive the second RF IC 70, and the first RF IC 60 constantly gains the gain. A control_1 signal for maintaining and a control_2 signal for allowing the second RF IC 70 to perform an AGC function are simultaneously transmitted. In this case, the processor may be configured to transmit the control_2 signal only when the second RF IC 70 is to be driven.

The first RF IC 60 receives the RF signal amplified from the first variable amplifier 40 and AGCs the RF signal according to the control_1 signal input from a processor (not shown) to the baseband unit 80. Transfer or keep the gain constant to transfer to the base band portion (80). The second RF IC 70 receives the amplified RF signal from the second variable amplifier 50 and transfers the RF signal to the baseband unit 80 by AGC according to the control_2 signal input from the processor. Do not. In this case, the second RF IC 70 may be driven only when the control_2 signal is input, and may not be driven unless the control_2 signal is input.

The baseband unit 80 includes an analog / digital converter (A / D) 81 and a buffer 82. The analog-to-digital converter 81 A / D converts an IF signal input from the first RF IC 60 or an IF signal input via the buffer 82. The buffer 82 time delays the IF signal so that the IF signal provided from the second RF IC 70 can be reproduced according to a fading time interval.

Referring to the operation of the DMB terminal according to the present invention configured as described above are as follows.

The RF DMB signal received through the antenna 10 is amplified by the low noise amplifier 20 and transmitted through the channel selected by the tracking filter 30. Since the intensity of the RF signal received through the antenna 10 is not constant, the RF signals having a constant intensity are output using the variable amplifiers 40 and 50. The variable amplifiers 40 and 50 may output a signal having a constant size by varying a gain depending on the strength of an input signal. Therefore, the gains of the variable amplifiers 40 and 50 are increased when a signal having a small signal strength is input and lowered when a signal having a large signal strength is input.

On the other hand, the processor (not shown) for controlling the overall DMB terminal according to the present invention compares the power strength of the RF DMB signal received through the antenna 10 with a threshold set in the terminal.

If the power strength of the received RF signal is less than the threshold value, the processor recognizes that a fading phenomenon occurs, and stops the AGC function of the first RF IC 60 to control1 signal to keep the gain constant. A control_2 signal is transmitted to the first RF IC 60, and a control_2 signal for driving the second RF IC 70 to perform an AGC function is transmitted to the second RF IC 70. Accordingly, the first RF IC 60 converts the RF signal into the IF signals IF_P1 and IF_N1 with the gain before receiving the control_1 signal as described above, and transmits the RF signal to the baseband unit 80 and the second RF. The IC 70 adjusts the gain of the RF signal and converts the RF signal into IF signals IF_P2 and IF_N2 to the baseband unit 80. Here, the IF_P1 signal and the IF_N1 signal are used as differential signals to be less affected by noise or other interference, and so are the IF_P2 signal and the IF_N2 signal. The IF_P1 and IF_N1 signals are transferred to the analog / digital converter 81 and undergo A / D conversion, and the IF_P2 and IF_N2 signals are transferred to the analog / digital converter 81 via the buffer 82. Therefore, the broadcast signal is reproduced by the IF_P2 signal and the IF_N2 signal when the distortion of the signal may occur when the broadcast signal is reproduced by the IF_P1 signal and the IF_N1 signal.

If the power strength of the received RF signal is not less than the threshold, the processor sends a control_1 signal to the first RF IC 60 to cause the first RF IC 60 to perform an AGC function, and the second RF The control_2 signal is transmitted to the second RF IC 70 to prevent the IC 70 from being driven. Accordingly, only the first RF IC 60 transmits the IF signals IF_P1 and IF_N1 to the baseband unit 80, and the analog / digital converter A / D converts the IF signals to restore the broadcast image. Here, the second RF IC 70 may be set to a state in which the second RF IC 70 is basically not driven so that the second RF IC 70 is driven when the control_2 signal is input and not driven when the control_2 signal is not input.

In the above, the first RF IC and the second RF IC of the DMB terminal according to the present invention are described as being controlled by the control_1 signal and the control_2 signal of the processor, respectively, but the first RF IC and the second RF IC without the control of the processor itself It is also possible to operate with In this case, threshold information for recognizing a fading phenomenon is stored in the first RF IC and the second RF IC, and if the power strength of the received signal is smaller than the threshold value, the first RF IC stops the AGC function. The second RF IC performs an AGC function, and if the received signal power strength is not smaller than the threshold, the second RF IC performs an AGC function and the second RF IC is not driven.

Additionally, the processor or the RF IC may measure the power strength of the received signal to contrast with the threshold set in the terminal in order to recognize the fading phenomenon, but may measure the signal-to-noise ratio of the received signal and contrast it with the reference set in the terminal. .

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, the apparatus for improving the reception sensitivity of the digital multimedia broadcasting according to the present invention has an effect of improving the reception sensitivity by using a diversity technique even when receiving a DMB signal from a terminal equipped with one antenna There is.

Claims (12)

In the terminal for receiving a digital multimedia broadcasting signal, A first RF IC section for adjusting the gain of the RF signal and converting it to an IF signal when the quality of the received signal is below a reference; A second RF IC unit for adjusting the gain of the RF signal and converting it to an IF signal when the quality of the received signal is higher than a reference; And a baseband unit configured to receive and restore an IF signal of the first RF IC unit or the second RF IC unit. The method of claim 1, wherein the quality of the received signal is And the power intensity of the received signal is determined that the quality of the received signal is lower than a reference when the power intensity of the received signal is smaller than a threshold value. The method of claim 1, wherein the quality of the received signal is And a signal-to-noise ratio of the received signal, and when the signal-to-noise ratio is less than the reference value, the quality of the received signal is determined to be less than the reference value. The method of claim 1, wherein the first RF IC unit, And maintaining the gain of the RF signal constant and converting it to an IF signal when the received signal power strength is less than a threshold. The method of claim 1, wherein the second RF IC unit, And is not driven when the received signal power strength is not less than a threshold. The method of claim 1, And a processor for transmitting a control signal to the first RF IC unit and the second RF IC unit, respectively, according to a result of comparing the received signal power strength with a threshold value. 7. The system of claim 6, wherein the processor is When the received signal power strength is smaller than the threshold value, the control_1 signal for maintaining the first RF IC additional gain and the control_2 signal for performing the second RF IC additional gain control function is transmitted. Device for improved sensitivity. 7. The system of claim 6, wherein the processor is When the received signal power strength is not less than the threshold value, the reception sensitivity improvement characterized by transmitting a control_1 signal to the first RF IC unit to perform a gain adjustment function and a control_2 signal to prevent the second RF IC unit from being driven. Device for. The method of claim 1, And a processor for transmitting a control signal to the first RF IC unit and the second RF IC unit, respectively, according to a result of comparing the signal-to-noise ratio of the received signal with a reference value. 10. The system of claim 9, wherein the processor is When the signal-to-noise ratio of the received signal is less than a reference value, the control_1 signal for maintaining the first RF IC additional gain and the control_2 signal for performing the second RF IC additional gain adjusting function are transmitted. Device for improved sensitivity. 10. The system of claim 9, wherein the processor is If the signal-to-noise ratio of the received signal is not less than the reference value, the reception sensitivity improvement characterized by transmitting a control_1 signal for allowing the first RF IC unit to perform a gain adjustment function and a control_2 signal for preventing the second RF IC unit from driving Device for. The method of claim 1, wherein the base band portion An analog / digital converter that converts digital signals into analog signals, And a buffer for delaying the IF signal of the second RF IC unit and outputting the delayed signal to the analog-to-digital converter.

Images