KR100235352B1 - Improved composite tuner for broadcasting - Google Patents

Abstract

The present invention relates to an improved broadcast composite tuner capable of adaptively receiving satellite and cable broadcasts by using a simple circuit configuration that does not require band pass filtering control for selective reception of satellite and cable broadcasts. To this end, the present invention is to extract the RF signal of a specific band through the band pass filtering in a predetermined band for the received satellite broadcast signal or cable broadcast signal, and in response to the oscillation control signal based on the user broadcast selection signal Means for generating a corresponding oscillation frequency and generating an IF signal by mixing the extracted RF signal with the oscillation frequency signal; Means for converting the IF signal into an intermediate frequency of satellite broadcasting through surface acoustic wave filtering, and automatically adjusting a gain of the intermediate frequency signal converted according to a gain control signal from the outside; An oscillator for selectively generating one fixed oscillation frequency for generating an intermediate frequency for cable broadcasting or another fixed oscillation frequency for generating an intermediate frequency for satellite broadcasting based on a user broadcast selection signal; The baseband for the intermediate frequency signal of the tuned cable broadcasting channel having a preset band or the tuned satellite channel having the preset band by mixing the converted intermediate frequency provided by the adjusting means with the oscillation frequency signal provided by the oscillator A second frequency mixer for generating an I signal of; A switching block for selectively switching the output of the second frequency mixer based on the user broadcast selection signal; A second band pass filter for band-filtering the intermediate frequency signal of the tuned cable broadcast channel provided through the switching block when the user broadcast selection signal is a cable broadcast to remove noise inserted in the signal component; A first low pass filter for low-pass filtering the baseband I signal for the tuned satellite channel provided through the switching block to remove noise embedded in the signal component when the user broadcast selection signal is a satellite broadcast; A shifter for shifting the oscillation frequency generated by the oscillator by 90 degrees; When the user broadcast selection signal is a satellite broadcast, a third frequency for generating a baseband Q signal for the tuned satellite channel through a mixture of the converted intermediate frequency provided by the adjusting means and the shifted oscillation frequency signal provided by the shifter; Mixer; And a second low pass filter for low pass filtering the baseband Q signal for the tuned satellite channel provided from the third frequency mixer to remove noise embedded in the signal components.

Description

Advanced broadcast tuner

The present invention relates to a broadcast composite tuner, and more particularly, to an improved broadcast composite tuner suitable for adaptively receiving cable broadcast signals as well as satellite broadcast signals.

In recent years, the broadcast method using satellites, which is rapidly expanding in use, is a method of providing broadcast signals to a wider area by using satellites (communication satellites) located at an altitude of about several tens to hundreds of kilometers from the surface of the earth. In this satellite broadcasting system, for example, an old band RF signal having a frequency band of 11.7 GHz to 12.0 GHz is used.

To this end, an antenna for satellite broadcasting reception is provided with a low noise blockdown converter for converting a radio frequency (RF) signal into an intermediate frequency (IF) signal, which is a high frequency RF signal. Is converted into an IF (intermediate frequency) signal in the hundreds to thousands of MHz bands (e.g., 950 MHz-2050 MHz) receivable by a satellite broadcasting receiver (receiver).

Therefore, in the satellite broadcasting tuner provided in the satellite broadcasting receiver (receiver), the channel selected by the user is tuned by inputting the IF signal received through the low noise converter.

On the other hand, in recent years, the cable broadcasting method using a cable as well as satellite broadcasting has been rapidly spreading, and if a subscriber (that is, one receiver) wants to receive all of these types of broadcast signals, Since the frequency bands are different, it may be necessary to separately install both a satellite tuner and a cable broadcast tuner.

Accordingly, in order to accommodate various types of broadcasts as described above, various types of internal or external tuners may be provided or two types of broadcasts may be provided in separate signal processing paths (that is, satellite broadcast signal processing paths and cable broadcast signals). It may be considered that the receiver adopts an integrated complex tuner to process through the processing path, but this causes not only a problem of unnecessarily increasing hardware of the receiver itself but also an excessive increase in the cost of the receiver. Is caused.

On the other hand, in view of the above, a composite tuner capable of simultaneously receiving satellite and cable broadcast signals through a single tuning path has been developed. It is filed under the name “and is pending.

The composite tuner controls the passband of the received signal and tunes the bandpassed signal based on the user's selection signal when receiving a satellite or cable broadcast signal at the input side. By tuning the oscillation frequency to tune the corresponding channel of the desired broadcast signal, these tuned signals are each configured to be provided to the corresponding demodulator through the separate signal processing path (BS path, DSR path, CATV path) have. In this case, the BS signal processing path and the cable broadcasting signal processing path are provided with respective small filters, and these two signals are provided to corresponding demodulators after surface acoustic wave filtering through the respective small filters.

In addition, the composite tuner performs automatic gain control on the wideband before band pass filtering on at least hundreds to thousands of MHz band frequency signals provided by the antenna's low noise converter.

However, the prior art as described above is not only required to separately provide tuning and tuning circuits for channel tuning according to user selection, but also is designed to adaptively control the pass band of the band pass filter to correspond to the broadcasting mode according to the user selection. As a result, the problem of avoiding the complexity of circuit implementation and control complexity was inevitable.

In addition, the prior art, which is configured to perform automatic gain control in the wideband (hundreds to thousands of MHz band) before bandpass filtering, has a problem that it is very difficult to implement an amplifier that can accommodate it because the gain control must be performed over the wideband. In addition, there is a problem in that the gain is automatically controlled even in a band other than the frequency band actually required, which may result in deterioration of filter characteristics.

The present invention is to solve the above problems of the prior art, it is possible to adaptively receive satellite broadcasting and cable broadcasting using a simple circuit configuration that does not require band pass filtering control for selective reception of satellite broadcasting and cable broadcasting. An object of the present invention is to provide an improved broadcast composite tuner.

In order to achieve the above object, the present invention provides a broadcast composite that tunes a satellite channel selected by a user in a satellite broadcast signal received through a satellite antenna and tunes a cable channel selected by a user in a cable broadcast signal received through a cable. A tuner comprising: a first band pass filter for extracting an RF signal of a specific band through band pass filtering in a predetermined band with respect to the received satellite broadcast signal or the cable broadcast signal; An oscillator for channel selection, having an oscillation frequency band capable of tuning the cable broadcasting and the satellite broadcasting, and generating an oscillation frequency corresponding to the oscillation control signal based on a user broadcast selection signal; A first frequency mixer for generating an IF signal by mixing an RF signal from the band pass filter with an oscillation frequency signal provided from the channel tuning oscillator; Means for converting the generated IF signal into the intermediate frequency of the satellite broadcasting through surface acoustic wave filtering and automatically adjusting the gain of the converted intermediate frequency signal according to a gain control signal from the outside; An oscillator for selectively generating one fixed oscillation frequency for generating the intermediate frequency for cable broadcasting or another fixed oscillation frequency for generating the satellite broadcasting based on the user broadcast selection signal; For a medium frequency signal of a tuned cable broadcast channel having a predetermined band or a tuned satellite channel having a predetermined band by mixing the converted intermediate frequency provided by the adjusting means with the oscillation frequency signal provided by the oscillator. A second frequency mixer for generating a baseband I signal; A switching block for selectively switching the output of the second frequency mixer based on the user broadcast selection signal; A second band pass filter which band-filters an intermediate frequency signal of the tuned cable broadcast channel provided through the switching block to remove noise embedded in a signal component when the user broadcast selection signal is a cable broadcast; A first low pass filter for low-pass filtering baseband I signals for the tuned satellite channels provided through the switching block to remove noise inserted in signal components when the user broadcast selection signal is satellite broadcasting; A shifter for shifting the oscillation frequency generated by the oscillator by 90 degrees; When the user broadcast selection signal is a satellite broadcast, a baseband Q signal for the tuned satellite channel is generated by mixing the converted intermediate frequency provided by the adjusting means with the shifted oscillation frequency signal provided by the shifter. A third frequency mixer; And a second low pass filter for low-pass filtering the baseband Q signal for the tuned satellite channel provided from the third frequency mixer to remove noise embedded in the signal components.

1 is a block diagram of an improved broadcast composite tuner according to a preferred embodiment of the present invention.

<Description of the code | symbol about the principal part of drawing>

102,210: band pass filter 104,204: oscillator

106,202,216: Frequency mixer 108,114,206,218: Amplifier

110: small filter 112: automatic gain controller

208 switch 214 shifter

The above and other objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

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

1 shows a block diagram of an improved broadcast composite tuner according to a preferred embodiment of the present invention.

As shown in the figure, the composite tuner of the present invention is a band pass filter (BPF1) 102, oscillator 104, frequency mixer 106, amplifier (AMP1) 108, small filter (SAW) 110 ), Automatic gain controller (AGC) 112, amplifier (AMP2) 114, frequency mixer 202, oscillator 204, amplifier (AMP3) 206, switch 208, band pass filter (BPF2) 210, low pass filter (LPF1) 212, shifter 214, frequency mixer 216, amplifier (AMP4) 218, and low pass filter (LPF2) 220.

Referring to FIG. 1, the received signal input to the band pass filter 102 may be a satellite broadcast signal received through a satellite broadcasting antenna (not shown) or a cable broadcast signal received through a cable (not shown) which is a transmission medium.

First, the band pass filter 102 filters a frequency of a predetermined band from a received broadcast signal (satellite broadcast signal or cable broadcast signal), that is, a predetermined band (for example, a frequency band of 950 MHz to 2050 MHz). Pass only frequency to generate RF signal. Thus, such band pass filtering primarily removes noise and the like.

Next, the frequency mixer 106 generates an IF signal through the mixing of the RF signal provided from the band pass filter 102 and the oscillation frequency signal from the oscillator 104, that is, the RF signal and the oscillation frequency signal. An intermediate frequency (IF) signal is generated, and the IF signal generated in this way is amplified to a predetermined level via the amplifier 108, and then output to the small filter 110.

At this time, the oscillator 104 generates an oscillation frequency of 552 MHz to 2530 MHz to accommodate (tuning) both satellite broadcasting and cable broadcasting, and oscillates from a controller (for example, a microprocessor) not shown. The oscillation frequency is controlled based on the control signal. That is, tuning of a channel desired by a user is performed by the oscillation frequency generated by the oscillator 104, and the tuning frequency is from 54 MHz to 2050 MHz.

Then, the small filter 110 converts the tuned broadcast frequency provided from the amplifier 108 into an intermediate frequency of 479.5 MHz through surface acoustic wave filtering, where the signal converted into the intermediate frequency signal is converted into the automatic gain controller 112. The gain is automatically adjusted so that its output is constant. At this time, the gain adjustment here is automatically performed under control from a controller (eg, a microprocessor) not shown, and the gain-adjusted output signal (ie, the tuned frequency signal) is a first signal. It is connected to the processing path 200 and the second signal processing path 300 at the same time.

Meanwhile, in the composite tuner of the present invention, one oscillator 204 is used to generate an oscillation frequency (435.5 MHz) for extracting intermediate frequencies for cable broadcasting, and also generate an oscillation frequency (479.5 MHz) for extracting intermediate frequencies for satellite broadcasting. do.

That is, in the oscillator 204, based on the oscillation control signal from the not shown controller (e.g., microprocessor) based on the user broadcast selection signal, the tuned cable broadcast of 435.5 MHz when the user selects the cable broadcast. Generate an oscillation frequency for the channel, and generate an oscillation frequency for the tuned satellite broadcast of 479.5 MHz when the user selects the satellite broadcast, the oscillation frequency generated here being provided to the frequency mixer 202 and the shifter 214, respectively.

In addition, the composite tuner of the present invention shares a path for extracting the intermediate frequency of the tuned cable broadcasting channel and a path for extracting the baseband I signal of the tuned satellite channel. That is, the circuit of the composite tuner can be further simplified by configuring to process these two signals using the one signal processing path, that is, the tuned cable broadcasting channel signal and the baseband I signal of the tuned satellite channel. .

To this end, in the frequency mixer 202, when the user selects the cable broadcasting channel, the mixture of the 479.5 MHz intermediate frequency signal provided by the amplifier 114 and the 435.5 MHz oscillation frequency signal provided by the oscillator 204 are mixed. And generate a 44 MHz cable broadcasting intermediate frequency signal, which is a difference signal between the two signals, wherein the generated 44 MHz cable broadcasting intermediate frequency signal is amplified to a predetermined level through an amplifier 206 and then switched 208. It is connected to the fixed contact a of. In addition, in the frequency mixer 202, when the user selects the satellite broadcasting channel, the mixing of the 479.5 MHz intermediate frequency signal provided by the amplifier 114 and the 479.5 MHz oscillation frequency signal provided by the oscillator 204 is performed. Generates a baseband I signal, which is amplified to a predetermined level through an amplifier 206 and then connected to the fixed contact a of the switch 208.

On the other hand, the switch 208 switches the output contact based on a switching control signal CS from a controller (e.g., a microprocessor), which is not shown, and the contact point when the user selects a channel broadcasting channel. ab is connected and the contact ac is connected when the user selects a station of the satellite broadcasting channel.

Accordingly, in the band pass filter 210, when a user selects a channel of a cable broadcasting channel, noise is removed during signal processing through filtering a frequency of a predetermined band provided through the variable contact b of the switch 208. In other words, only the frequencies of the tuned specific channel bands (channel signals having an intermediate frequency of 44 MHz and a 6 MHz band) are passed, and the analog broadcast signals of the tuned channels output from the band pass filter 208 are sent to the monitor. Provided to the cable broadcast decoder not shown for display.

Further, in the low pass filter 212, when the user selects a station of the satellite broadcast channel, the high pass is filtered by filtering the baseband I signal of the tuned satellite broadcast channel provided through the variable contact c of the switch 208. Noise is removed, such as components, wherein the I signal of the tuned satellite broadcast channel from which the noise is removed is provided to a satellite broadcast decoder, not shown, for display on a monitor.

On the other hand, the shifter 214 is 90 degrees to the 479.5 MHz oscillation frequency generated by the oscillator 204 for the phase recovery (restore) of the Q signal phase shifted 90 degrees at the transmitting side to prevent interference between the I signal and the Q signal Shifted, where the shifted oscillation frequency is provided to a frequency mixer 216 for baseband signal extraction of the satellite channel Q signal.

Accordingly, in the frequency mixer 218, when the user selects the satellite broadcasting channel, the mixing of the 479.5 MHz intermediate frequency signal provided by the amplifier 114 and the 90 degree shifted oscillation frequency provided by the shifter 214 is performed. A baseband Q signal is generated and then amplified to a predetermined level by the amplifier 218, where the amplified baseband Q signal is provided to the low pass filter 220 of the next stage.

Further, in the low pass filter 220, when the user selects a preset of the satellite broadcast channel, the high-band component is removed by filtering the baseband Q signal of the tuned satellite broadcast channel provided by the amplifier 218. The Q signal of the tuned satellite broadcast channel from which the noise is removed is provided to a satellite broadcast decoder, not shown, for display on a monitor.

Accordingly, in the present invention, when satellite broadcasting and cable broadcasting are configured to be received through one television (combined tuner), if the broadcasting selected by the user (or tuned in) is a cable broadcasting channel, the output through the frequency mixer 202 is performed. The tuned cable broadcast channel signal may be provided to a cable broadcast decoder (not shown), and if the broadcast selected by the user (or tuned) is a satellite broadcast channel, the tuner outputted through the frequency mixer 202 and the frequency mixer 216. The baseband I and Q signals of the satellite broadcast channel will be provided to the satellite broadcast decoder (not shown).

As described above, according to the present invention, the hardware of the composite tuner can be automatically tuned to the satellite broadcasting and the cable broadcasting selectively (or adaptively) without separately providing tuning and tuning circuits for channel tuning according to user selection. In addition, the complexity of the tuning control can be eliminated by eliminating the adaptive filtering band control of the band pass filter that converts the RF signal to the IF signal.

In addition, the conventional tuner, unlike the prior art that performs automatic gain control in a wideband (RF signal) before band pass filtering, is configured to automatically control the gain at the IF signal level to effectively prevent degradation of filter characteristics. Can be.

Furthermore, the composite tuner of the present invention comprises an oscillator for generating an oscillation frequency used to extract an intermediate frequency signal for tuned cable broadcasting and an oscillator for generating an oscillation frequency used for extracting the baseband signal of a tuned satellite broadcasting channel. By sharing with one oscillator, the circuit of the complex tuner can be further simplified.

Claims (1)

In the broadcast composite tuner tunes the satellite channel selected by the user from the satellite broadcast signal received through the satellite antenna, and the cable channel selected by the user from the cable broadcast signal received through the cable, A first band pass filter for extracting an RF signal of a specific band through band pass filtering in a predetermined band with respect to the received satellite broadcast signal or the cable broadcast signal; An oscillator for channel selection, having an oscillation frequency band capable of tuning the cable broadcasting and the satellite broadcasting, and generating an oscillation frequency corresponding to the oscillation control signal based on a user broadcast selection signal; A first frequency mixer for generating an IF signal by mixing an RF signal from the band pass filter with an oscillation frequency signal provided from the channel tuning oscillator; Means for converting the generated IF signal into the intermediate frequency of the satellite broadcasting through surface acoustic wave filtering and automatically adjusting the gain of the converted intermediate frequency signal according to a gain control signal from the outside; An oscillator for selectively generating one fixed oscillation frequency for generating the intermediate frequency for cable broadcasting or another fixed oscillation frequency for generating the satellite broadcasting based on the user broadcast selection signal; For a medium frequency signal of a tuned cable broadcast channel having a predetermined band or a tuned satellite channel having a predetermined band by mixing the converted intermediate frequency provided by the adjusting means with the oscillation frequency signal provided by the oscillator. A second frequency mixer for generating a baseband I signal; A switching block for selectively switching the output of the second frequency mixer based on the user broadcast selection signal; A second band pass filter which band-filters an intermediate frequency signal of the tuned cable broadcast channel provided through the switching block to remove noise embedded in a signal component when the user broadcast selection signal is a cable broadcast; A first low pass filter for low-pass filtering baseband I signals for the tuned satellite channels provided through the switching block to remove noise inserted in signal components when the user broadcast selection signal is satellite broadcasting; A shifter for shifting the oscillation frequency generated by the oscillator by 90 degrees; When the user broadcast selection signal is a satellite broadcast, a baseband Q signal for the tuned satellite channel is generated by mixing the converted intermediate frequency provided by the adjusting means with the shifted oscillation frequency signal provided by the shifter. A third frequency mixer; And And a second low pass filter for low-pass filtering the baseband Q signal for the tuned satellite channel provided from the third frequency mixer to remove noise embedded in the signal components.

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