WO2008023896A1

WO2008023896A1 - Receiving apparatus

Info

Publication number: WO2008023896A1
Application number: PCT/KR2007/003882
Authority: WO
Inventors: Hye Ryung Lee
Original assignee: Lg Innotek Co., Ltd
Priority date: 2006-08-24
Filing date: 2007-08-14
Publication date: 2008-02-28
Also published as: CN101331759A; KR100872550B1; KR20080018364A; EP2055098A1; EP2055098A4

Abstract

A receiving apparatus comprises: a tuner receiving first and second broadcasting signals to output predetermined signals; first and second demodulators demodulating and outputting the first and second broadcasting signals output from the tuner, respectively; a first automatic gain controller (AGC) detecting the signals output from the tuner to output a first automatic gain control signal; and a switching unit providing the tuner with the first automatic gain control signal or a second automatic gain control signal output from the first demodulator according to the broadcasting signals received by the tuner.

Description

RECEIVING APPARATUS

Technical Field

[1] The embodiment relates to a receiving apparatus.

Background Art

[2] A receiving apparatus comprises a tuner receiving broadcasting signals. The tuner converts a radio frequency (RF) signal, received through an antenna, to an intermediate frequency (IF) signal. A demodulator connected with the tuner demodulates the input IF signal to a baseband signal, thereby outputting a video signal, an audio signal, and so on.

[3] The receiving apparatus is able to receive the broadcasting signals based on various broadcasting systems, and requires suitable amplification of the RF signal depending on the received broadcasting system-based broadcasting signals. Disclosure of Invention Technical Problem

[4] The embodiment provides a receiving apparatus.

[5] The embodiment provides a receiving apparatus capable of receiving broadcasting signals based on various broadcasting systems with receive sensitivity improved.

[6] The embodiment provides a receiving apparatus, which reduces an influence of noise. Technical Solution

[7] According to an embodiment, a receiving apparatus comprises: a tuner receiving first and second broadcasting signals to output predetermined signals; first and second demodulators demodulating and outputting the first and second broadcasting signals output from the tuner, respectively; a first automatic gain controller (AGC) detecting the signals output from the tuner to output a first automatic gain control signal; and a switching unit providing the tuner with the first automatic gain control signal or a second automatic gain control signal output from the first demodulator according to the broadcasting signals received by the tuner.

[8] According to an embodiment, a receiving apparatus comprises: a tuner receiving a plurality of broadcasting signals to output intermediate frequency (IF) signals; a plurality of demodulators demodulating and outputting the IF signals output from the tuner; a first automatic gain controller (AGC) detecting the IF signal output from the tuner to output a first automatic gain control signal; and a switching unit providing the tuner with the first automatic gain control signal or a second automatic gain control signal output from one of the plurality of demodulators according to the broadcasting signals received by the tuner.

[9] According to an embodiment, a receiving apparatus comprises: a tuner receiving a plurality of broadcasting signals to output intermediate frequency (IF) signals; a plurality of demodulators demodulating and outputting the IF signals output from the tuner; and an automatic gain controller (AGC) providing the tuner with a first automatic gain control signal detected from the IF signal output from the tuner or a second automatic gain control signal detected from a baseband signal of one of the plurality of demodulators according to the broadcasting signals received by the tuner.

Advantageous Effects

[10] According to the embodiments, the receiving apparatus can receive the broadcasting signals based on various broadcasting systems with receive sensitivity improved. [11] The receiving apparatus can reduce an influence of noise.

[12] The receiving apparatus can be readily designed and produced.

Brief Description of the Drawings [13] FIG. 1 is a block diagram for explaining a receiving apparatus according to an embodiment; [14] FIG. 2 is a view for explaining a tuner of a receiving apparatus according to an embodiment; [15] FIG. 3 is a view for explaining the first demodulator of a receiving apparatus according to an embodiment; [16] FIG. 4 is a view for explaining the second AGC of a receiving apparatus according to an embodiment; [17] FIG. 5 is a view for explaining the first AGC and the switching unit of a receiving apparatus according to an embodiment; and [18] FIG. 6 is a circuit diagram for explaining the first AGC and the switching unit of a receiving apparatus according to an embodiment.

Mode for the Invention [19] Hereinafter, a receiving apparatus according to an embodiment will be described with reference to the accompanying drawings. [20] FIG. 1 is a block diagram for explaining a receiving apparatus according to an embodiment, and FIG. 2 is a view for explaining a tuner of a receiving apparatus according to an embodiment. [21] Referring to FIGS. 1 and 2, the receiving apparatus according to an embodiment comprises a tuner 100 that receives ones selected from a plurality of broadcasting signals to output intermediate frequency (IF) signals, first and second demodulators

200 and 300 that demodulate the IF signals output from the tuner 100, a first automatic gain controller (AGC) 400 that detects the IF signals output from the tuner 100 to output a first automatic gain control signal, and a switching unit 500 that selectively provides the tuner 100 with the first automatic gain control signal output from the first

AGC 400 and a second automatic gain control signal output from the first demodulator

200. [22] Further, the tuner 100 comprises a radio frequency (RF) signal processor 110, a local oscillator circuit 120, and a mixer 130 that mixes an oscillating frequency output from the local oscillator circuit 120 with an RF signal output from the RF signal processor

110 to output the IF signals, and an IF signal processor 140. [23] The RF signal processor 110 comprises a filter 111, an input tunning part 112, an RF amplifier 113, and an RF tunning part 114. The IF signal processor 140 comprises an

IF tunning part 141 filtering the IF signals output from the mixer 130, and an IF amplifier 142 amplifying the IF signals output from the IF tunning part 141. [24] The filter 111 passes the signals of a desired frequency band as a circuit having good frequency selectivity. The filter 111 has a series resonant circuit or a parallel resonant circuit. [25] The input tunning part 112 comprises a circuit for impedance matching between the filter 111 and the RF amplifier 113, and is designed to minimize insertion loss. [26] The RF amplifier 113 comprises a circuit for amplifying the RF signal, and varies a degree of amplification of the RF signal according to the input automatic gain control signal. [27] The RF tunning part 114 comprises a double-tuned circuit, selects a desired RF signal, and make a frequency characteristic flat. [28] Meanwhile, the receiving apparatus can receive the broadcasting signals transmitted at a plurality of frequency bands. In the embodiment, the receiving apparatus receives an ultrahigh frequency (UHF) signal, a very high frequency (VHF)-High signal, and a

VHF-Low signal. [29] As illustrated in FIG. 2, in order to receive these UHF, VHF-High, and VHF-Low signals, the tuner 100 has three RF signal processors 110, or may have one or two RF signal processors 110 that are commonly used by switching. [30] In the embodiment, the tuner 100 has the respective RF signal processors 110, which are indicated in FIG. 1 by one block. [31] Further, the receiving apparatus has a plurality of demodulators so as to receive and output the broadcasting signals based on a plurality of broadcasting systems. In the embodiment, the receiving apparatus has two demodulators, i.e. the first and second demodulators 200 and 300. However, the number of demodulators is not limited to two. [32] For example, the first demodulator 200 may function as an analog demodulator, and the second demodulator 300 may function as a digital demodulator or an FM radio de- modulator.

[33] The first demodulator 200 demodulates the IF signals, output from the tuner 100, to baseband signals, and outputs the demodulated signals. The first demodulator 200 senses the baseband signals to output an automatic gain control signal.

[34] The second demodulator 300 demodulates the IF signals, output from the tuner 100, to the baseband signals, and outputs the demodulated signals.

[35] Here, the first demodulator 200 and the second demodulator 300 demodulate the broadcasting signals based on different broadcasting system, and output the demodulated signals. For example, in the case in which the tuner 100 receives the broadcasting signal based on an analog broadcasting system, the first demodulator 200 demodulates the analog broadcasting signal. In contrast, in the case in which the tuner 100 receives the broadcasting signal based on a digital broadcasting system, the second demodulator 300 demodulates the digital broadcasting signal.

[36] The first AGC 400 detects the IF signals output from the tuner 100, and determines and outputs a first automatic gain control signal.

[37] Meanwhile, the switching unit 500 selectively provides the first automatic gain control signal output from the first AGC 400 and the second automatic gain control signal output from the first demodulator 200 to the RF amplifier 113 of the RF signal processor 110.

[38] When the tuner 100 receives the broadcasting signal demodulated and output through the first demodulator 200, the switching unit 500 is switched according to a control signal, and then provides the second automatic gain control signal output from the first demodulator 200 to the RF amplifier 113.

[39] In contrast, when the tuner 100 receives the broadcasting signal demodulated and output through the second demodulator 300, the switching unit 500 is switched according to a control signal, and then provides the first automatic gain control signal output from the first AGC 400 to the RF amplifier 113.

[40] In the receiving apparatus according to an embodiment, the first demodulator 200 demodulates the broadcasting signal of the broadcasting system sensitive to a noise component. For example, the first demodulator 200 demodulates the broadcasting signal of the analog broadcasting system.

[41] It is assumed that the tuner 100 receives the broadcasting signal of the analog broadcasting system demodulated and output through the first demodulator 200, the switching unit 500 is switched according to a control signal, provides the first automatic gain control signal output from the first AGC 400 to the RF amplifier 113, and then amplifies the RF signal,

[42] In this case, when the level of a desired broadcasting signal is actually low, and when the level of an interference signal having a frequency band adjacent to that of the desired broadcasting signal is high, the automatic gain control signal should be determined on the basis of the level of the desired broadcasting signal. Nevertheless, the automatic gain control signal is determined on the basis of the high level of the interference signal, thereby providing a degree of amplification to the RF amplifier 113.

[43] In other words, the IF signals output from the tuner 100 have a band width of 20

MHz to 30 MHz, thus having a high possibility of getting an influence of the interference signal adjacent to the desired broadcasting signal. Hence, regardless of the level of the desired signal, the automatic gain control signal is determined by a highest level of the output IF signals. In other words, although the desired signal has a low level, it is recognized as a strong electric field signal when the adjacent interference signal has a high level, and thus the amplification degree of the RF amplifier 113 is lowered.

[44] Consequently, because the desired signal is amplified with a low amplification degree rather than a high amplification degree in spite of the low level thereof, the receive sensitivity is lowered, and screen noise occurs. Especially, in the case of the analog demodulator vulnerable to background noise, the desired signal is greatly influenced by such noise.

[45] Accordingly, in the receiving apparatus according to an embodiment, in the case in which the tuner 100 receives the analog broadcasting system-based broadcasting signal demodulated and output from the first demodulator 200, the second automatic gain control signal output from the first demodulator 200 is provided to the RF amplifier 113.

[46] The baseband signals, that determine the second automatic gain control signal at the first demodulator 200, have a band width of about 6 MHz, thus having a low possibility of getting an influence of the interference signal. Therefore, the automatic gain control signal according to the level of the desired broadcasting signal is provided to the RF amplifier 113.

[47] FIG. 3 is a view for explaining the first demodulator of a receiving apparatus according to an embodiment.

[48] In the embodiment, the first demodulator 200 that demodulates the broadcasting signal based on the analog broadcasting system is shown in a block diagram.

[49] The first demodulator 200 comprises a surface acoustic wave (SAW) filter 201, a video intermediate frequency (VIF) amplifier 202, a video detector 203, a voltage controlled oscillator (VCO) 204, an automatic frequency tuning (AFT) 205, a sound intermediate frequency (SIF) trap filter 206, a SIF filter 207, a sound detector 208, a video equalizer (EQ) 209, and a second AGC 210.

[50] The SAW filter 201 passes only a desired signal of IF signals output from the tuner

100. The broadcasting signals have a band width of about 6 MHz, and the IF signals output from the tuner 100 have a band width of 20 MHz to 30 MHz. As such, the SAW filter 201 is allowed to pass only the broadcasting signals having a desired band width.

[51] For example, in the event that the broadcasting system is a National TV Standards

Committee (NTSC) US broadcasting system, the SAW filter passes a picture carrier of 45.75 MHz, a color carrier of 42.17 MHz, and a sound carrier of 41.25 MHz.

[52] The VIF amplifier 202 is implemented as a 3-stage AC-coupled differential amplifier, and has an amplification degree determined by the second AGC 210 such that the video and sound can have sufficient sensitivity.

[53] In the case of the NTSC US broadcasting system, the video detector 203 converts the

IF signals of the picture carrier of 45.75 MHz, color carrier of 42.17 MHz, and sound carrier of 41.25 MHz to a baseband signal of 0 MHz to 4.5 MHz.

[54] The VCO 204 is called voltage controlled oscillator, and transmits a control signal to the AFT such that the tuner 100 can control frequencies.

[55] The AFT 205 indicates how much an input signal frequency is distorted using direct current (DC) voltage, so as to correct the distorted frequency.

[56] The SIF trap filter 206 filters a sound signal band, while the SIF filter 207 passes the sound signal band.

[57] The sound detector 208 performs signal processing such that a sound signal is output.

[58] The video EQ 209 optimizes a quality of image frequency.

[59] The second AGC 210 functions to set the amplification degree of the tuner 100 as well as the amplification degree of the VIF amplifier 202, and outputs a second automatic gain control signal.

[60] FIG. 4 is a view for explaining the second AGC 210 of a receiving apparatus according to an embodiment.

[61] The second AGC 210 comprises an AGC detector 211 that detects a level of the baseband signal output from the SIF trap filter 206 and outputs a voltage value, an IF AGC 212 that provides an amplification degree to the VIF amplifier 202 according to the output of the AGC detector 211 and controls a level of the signal reduced at the SAW filter 201, and an RF AGC 213 that outputs a second automatic gain control signal according to the output of the IF AGC 212.

[62] FIG. 5 is a view for explaining the first AGC and the switching unit of a receiving apparatus according to an embodiment.

[63] The first AGC 400 can be included in a mixer oscillator phase locked loop

(MOPLL), detects the IF signals output from the mixer 130, determines the first automatic gain control signal according to programmed software, and outputs the determined signal to the RF amplifier 113 through the switching unit 500.

[64] FIG. 6 is a circuit diagram for explaining the first AGC and the switching unit of a receiving apparatus according to an embodiment. [65] The first AGC 400 comprises first, second and third transistors Ql, Q2 and Q3, first through tenth resistors Rl through RlO, and first and second capacitors Cl and C2, so as to detect and output the IF signals output from the tuner 100.

[66] The switching unit 500 comprises a signal output unit 520 including the fifth transistor Q5, fourteenth and fifteenth resistors R 14 and Rl 5, and fourth and fifth capacitors C4 and C5, all of which cause the second automatic gain control signal output from the first demodulator 200 to be output, when the tuner 100 receives the broadcasting signal demodulated and output by the first demodulator 200. Further, the switching unit 500 comprises a signal interrupter 510 including the fourth transistor Q4, and eleventh through thirteenth resistors RI l through R 13, all of which interrupt the second automatic gain control signal output from the first demodulator 200 so as to cause the first automatic gain control signal output from the first AGC 400 to be output, when the tuner 100 receives the broadcasting signal demodulated and output by the second demodulator 300.

[67] According to the design, the switching unit 500 may be implemented as a switch using a relay.

[68] The receiving apparatus according to an embodiment can receive and output a broadcasting signal based on a plurality of broadcasting systems.

[69] The broadcasting signals input through an antenna pass the filter 111 in the tuner

100, are selected by the input tunning part 112, and are amplified by the RF amplifier 113.

[70] Among the broadcasting signals amplified by the RF amplifier 113, desired broadcasting signals are selected. Channel frequencies of the desired broadcasting signals are selected by the RF tunning part 114, are mixed with an oscillating frequency through the mixer 130. Thereby the IF signals are output.

[71] The IF signals output from the mixer 130 are tuned, amplified, and output by the IF tunning part 141 and the IF amplifier 142.

[72] When the broadcasting signals demodulated by the first demodulator 200 are received into the tuner 100, the first demodulator 200 demodulates and outputs the IF signals input from the tuner 100, determines the second automatic gain control signal, and provides it to the switching unit 500. The switching unit 500 outputs the second automatic gain control signal to the RF amplifier 113 according to a control signal.

[73] When the broadcasting signals demodulated by the second demodulator 300 are received into the tuner 100, the first AGC 400 senses the IF signals output from the tuner 100, determines the first automatic gain control signal, and provides it to the switching unit 500. The switching unit 500 outputs the first automatic gain control signal to the RF amplifier 113 according to a control signal.

[74] When the broadcasting signals demodulated by the first modulator 200 are received, a low signal is applied to the signal interrupter 510 of the switching unit 500 and to the first AGC 400.

[75] The fourth transistor Q4 of the signal interrupter 510 is turned off by the low signal, and thus no driving voltage is applied to the first AGC 400.

[76] Accordingly, although the IF signals of the tuner 100 are applied to the first AGC

400, the first AGC 400 does not operate, so that the first automatic gain control signal for the IF signals of the tuner 100 is interrupted.

[77] In contrast, as the fourth transistor Q4 is turned off, the voltage of 5V is applied from the signal interrupter 510 to the fifth transistor Q5 of the signal output unit 520, so that the fifth transistor Q5 is turned on.

[78] In other words, because the driving voltage is applied from the signal interrupter 510 to the fifth transistor Q5, the second automatic gain control signal of the first demodulator 200 is input into the RF amplifier 113 of the tuner 100, thereby controlling the level of the RF signal.

[79] Meanwhile, when the broadcasting signals demodulated by the second demodulator

300 are received, a high signal is applied to the signal interrupter 510 of the switching unit 500 and to the first AGC 400.

[80] The fourth transistor Q4 of the signal interrupter 510 is turned on by the high signal, and thus the driving voltage of 5 V is earthed. Thus, the driving voltage applied to the signal output unit 520 is interrupted.

[81] Accordingly, the second automatic gain control signal output from the first demodulator 200 is applied to a base terminal of the fifth transistor Q5 of the signal output unit 520, but the driving voltage is not applied from the signal interrupter 510 to the fifth transistor Q5. For this reason, the fifth transistor Q5 is turned off, so that second automatic gain control signal of the first demodulator 200 is not output through the fifth transistor Q5.

[82] In contrast, the driving voltage can be applied to the first AGC 400 by the high signal, and thus the first AGC 400 operates. Thus, the first automatic gain control signal for the IF signals of the tuner 100 is provided to the RF amplifier 113.

[83] Accordingly, the first transistor Ql of the first AGC 400 is turned on by the applied high signal and the input IF signals of the turner 100, and thus the second and third transistors Q2 and Q3 are turned on. The first automatic gain control signal for the IF signals of the tuner 100 which are input to the first AGC 400 is determined by the first, second and third transistors Ql, Q2 and Q3, is input into the RF amplifier 113, and thereby controlling the level of the RF signal.

[84] Meanwhile, according to another embodiment, the receiving apparatus can selectively provide the automatic gain control signals to the turner 100 according to the levels of the plurality of baseband signals. [85] However, according to the embodiment illustrated in FIGS. 1 through 6, the amplification degree of the RF signals of the tuner 100 is determined using both the automatic gain control signal output according to the signals detected by the demodulators and the automatic gain control signal output according to the signals detected from the IF signals output from the tuner. This method facilitates design and production. Industrial Applicability

[86] The embodiment can be applied to the receiving apparatus having the tuner.

[87]

Claims

[1] A receiving apparatus comprising: a tuner receiving first and second broadcasting signals to output predetermined signals; first and second demodulators demodulating and outputting the first and second broadcasting signals output from the tuner, respectively; a first automatic gain controller (AGC) detecting the signals output from the tuner to output a first automatic gain control signal; and a switching unit providing the tuner with the first automatic gain control signal or a second automatic gain control signal output from the first demodulator according to the broadcasting signals received by the tuner.

[2] The receiving apparatus according to claim 1, wherein the first demodulator demodulates an analog broadcasting signal.

[3] The receiving apparatus according to claim 1, wherein the second demodulator demodulates one selected from a digital broadcasting signal and a frequency modulation (FM) radio signal.

[4] The receiving apparatus according to claim 1, wherein the tuner receives at least one selected from an ultrahigh frequency (UHF) signal, a very high frequency (VHF)-High signal, and a VHF-Low signal.

[5] The receiving apparatus according to claim 1, wherein the first demodulator comprises a second AGC, which detects a baseband signal of the first demodulator to control a degree of amplification of the signal input into the first demodulator, and which outputs the second automatic gain control signal.

[6] The receiving apparatus according to claim 1, wherein the first AGC comprised in a mixer oscillator phase locked loop (MOPLL), and is operated according to programmed software.

[7] The receiving apparatus according to claim 1, wherein the switching unit causes the second automatic gain control signal output from the first demodulator to be provided to the tuner when the tuner receives the first broadcasting signal, and causes the first automatic gain control signal output from the first AGC to be provided to the tuner when the tuner receives the second broadcasting signal.

[8] The receiving apparatus according to claim 1, wherein the switching unit comprises a relay.

[9] A receiving apparatus comprising: a tuner receiving a plurality of broadcasting signals to output intermediate frequency (IF) signals; a plurality of demodulators demodulating and outputting the IF signals output from the tuner; a first automatic gain controller (AGC) detecting the IF signal output from the tuner to output a first automatic gain control signal; and a switching unit providing the tuner with the first automatic gain control signal or a second automatic gain control signal output from one of the plurality of demodulators according to the broadcasting signals received by the tuner.

[10] The receiving apparatus according to claim 9, wherein the plurality of demodulators demodulate at least two selected from an analog broadcasting signal, a digital broadcasting signal, and a frequency modulation (FM) radio signal.

[11] The receiving apparatus according to claim 9, wherein, when any one of the plurality of demodulators demodulates an analog broadcasting signal, the switching unit provides the tuner with the second automatic gain control signal output from the demodulator demodulating the analog broadcasting signal.

[12] The receiving apparatus according to claim 9, wherein, when any one of the plurality of demodulators demodulates a digital broadcasting signal or a frequency modulation (FM) radio signal, the switching unit provides the tuner with the first automatic gain control signal.

[13] A receiving apparatus comprising: a tuner receiving a plurality of broadcasting signals to output intermediate frequency (IF) signals; a plurality of demodulators demodulating and outputting the IF signals output from the tuner; and an automatic gain controller (AGC) providing the tuner with a first automatic gain control signal detected from the IF signal output from the tuner or a second automatic gain control signal detected from a baseband signal of one of the plurality of demodulators according to the broadcasting signals received by the tuner.

[14] The receiving apparatus according to claim 13, wherein, when any one of the plurality of demodulators demodulates an analog broadcasting signal, the AGC provides the tuner with the second automatic gain control signal detected from the demodulator demodulating the analog broadcasting signal.

[15] The receiving apparatus according to claim 13, wherein, when any one of the plurality of demodulators demodulates a digital broadcasting signal or a frequency modulation (FM) radio signal, the AGC provides the tuner with the first automatic gain control signal.