WO2004071086A1

WO2004071086A1 - Multi-channel wireless tv receiving apparatus

Info

Publication number: WO2004071086A1
Application number: PCT/KR2003/000284
Authority: WO
Inventors: Keun Seo Park; Keun Hu
Original assignee: Rf Korea Inc.
Priority date: 2003-02-10
Filing date: 2003-02-10
Publication date: 2004-08-19
Also published as: AU2003207129A1; MXPA04012548A

Abstract

Multi-channel wireless TV receiving apparatus includes a first down-converter for converting a first signal having a first frequency bandwidth into a second signal having a second frequency bandwidth, a second down-converter for converting the second signal into a third signal having a third frequency bandwidth, a demodulator for extracting from the third signal a control data signal to be used in controlling the receiving apparatus, a memory for storing variables used in controlling the receiving apparatus and a controller for shifting a reference frequency of the first down-converter by a predetermined frequency based on the control data. The control data may include an identification number for a subscriber of the receiving apparatus, which is to be compared with an identification number stored in the memory. By shifting the reference frequency and verifying the identification number, the receiving apparatus can prevent an unauthorized person from watching TV programs.

Description

ULTI-CHANNEL WIRELESS TV RECEIVING APPARATUS

Technical Field

The present invention relates to a multi-channel wireless television receiving apparatus; and, more particularly, to a multi-channel wireless television receiving apparatus, which converts a signal with an MMDS (multi-channel multipoint distribution service) band into a signal with a watchable frequency VHS/UHF (very high frequency/ultrahigh frequency) band, identifies an address, which is used to identify a subscriber to a wireless TV service, from the signal with a watchable frequency band, and performs the functions of frequency band conversion and shutdown, thus preventing the illegal watching of CATV programs .

Background Art

Early CATV (cable televisions) were developed as an auxiliary means for assisting users, which reside in fringe areas of general terrestrial broadcast TVs, in watching the general terrestrial broadcast TVs. Recently, however, CATV programs are being provided through a variety of channels, and there are being developed technologies of providing an interactive multimedia service in which two-way information exchange can be enabled between users and a broadcasting station.

For a wireless CATV service capable of supporting such an interactive multimedia service having been commercialized and being currently developed, there are LMDS (local multipoint distribution service) and MMDS (multi-channel multipoint distribution service) . LMDS is a technology of transmitting and receiving video, audio and general data between a transmitter of a broadcasting service provider and terminals of subscribers using a millimeter wave with a frequency band of 24-28 GHz, and is capable of providing a broadcasting service for a relatively small cell with a radius of 2-4 km. In contrast, MMDS is a technology of wirelessly transmitting and receiving multimedia data between a transmitter of a broadcasting service provider and the terminals of subscribers using a signal with a frequency band of 2.5-2.7 GHz, and is capable of providing a service over an area with a radius of 50-100 km.

In general, each of the CATV subscribers utilizing MMDS is provided with a broadcasting service through a receiving system having a configuration as shown in FIG. 1. That is, when a TV signal is received through a receiving antenna installed outdoors, the received signal is input to a down-converter 120. In this case, the received signal includes a signal with a frequency band of 2.5-2.7 GHz, and the down-converter 120 converts the frequency band of the received signal into a watchable frequency band, that is, a frequency band of several ten to several hundred MHz. A signal with the converted frequency band is input to a set- top box 130. The set-top box 130 amplifies, demodulates and/or decodes a part of the input signal, which has a frequency band corresponding to a channel selected by the subscriber, and provides the amplified, demodulated and/or decoded signal to a TV 140. In this case, the frequency band corresponding to the channel selected by the user is fixed to a constant value, so that the set-top box 130 previously stores the information of frequency bands corresponding to various channels and performs a function of searching for channels using the information.

However, since a prior art receiving apparatus for receiving signals with a MMDS band performs a search for a frequency band corresponding to each of the channels based on the previously stored, fixed information of frequency bands, a problem arises in that it is easy for users, who do not subscribe to the CATV broadcasting service, to acquire such frequency information and illegally watch CATV programs.

Disclosure of Invention

It is, therefore, an object of the present invention to provide a multi-channel wireless TV receiving apparatus, which converts a MMDS frequency band into a watchable frequency band using a down-converter, allocates addresses to subscribers to a CATV broadcasting service to identify them, and performs the functions of frequency band conversion and shutdown, thus preventing the illegal watching of CATV programs.

In accordance with the present invention, there is provided a multi-channel wireless TV receiving apparatus including: a first down-converter for converting a signal with a first frequency band into a signal with a second frequency band; a second down-converter for converting a signal with the second frequency band into a signal with a third frequency band; a demodulator for demodulating control data, which is used for control of the TV receiving apparatus, from the signal with the third frequency band; a memory for storing variables related to the control of the TV receiving apparatus; and a controller converting a first reference frequency of the first down-converter using the control data output from the demodulator.

The first down-converter of the multi-channel wireless TV receiving apparatus in accordance with the present invention may include a first local oscillator for generating the first reference frequency; and a first mixer for generating the signal with the second frequency band by mixing the signal with the first frequency band and the signal with the first reference frequency generated by the first local oscillator. Further, the second down-converter of the multichannel wireless TV receiving apparatus in accordance with the present invention may include a second local oscillator for generating a second reference frequency; and a second mixer for generating the signal with the third frequency band by mixing the signal with the second frequency band and the signal with the second reference frequency generated by the second local oscillator.

The control data may include an instruction to convert the first reference frequency, and/or a subscriber ID (identification) .

Further, the controller may convert the first reference frequency of the first down-converter into a frequency shifted by a predetermined frequency magnitude according to the instruction to convert the first reference frequency.

The controller may compare the subscriber ID with the variables stored in the memory, and stop the reception of the wireless signals in the multi-channel wireless TV receiving apparatus if the subscriber ID does not coincide with any one of the variables.

Brief Description of Drawings

The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:

Fig. 1 is a diagram showing a prior art down-converter and a prior art set-top box for receiving a CATV signal; Fig. 2 illustrates a diagram showing a TV receiving apparatus in accordance with a preferred embodiment of the present invention;

Fig. 3 exhibits a circuit diagram showing a detailed configuration of the TV receiving apparatus shown in Fig. 2; Fig. 4 charts a flowchart showing a method for controlling the TV receiving apparatus in accordance with the preferred embodiment of the present invention; and

Fig. 5 provides a diagram showing a format of a control data packet used to control the TV receiving apparatus in accordance with the present invention.

Best Mode for Carrying Out the Invention

Preferred embodiments of the present invention are described in detail with reference to the accompanying drawings below.

Fig. 2 shows a configuration of a multi-channel wireless TV receiving system in accordance with a preferred embodiment of the present invention. A multi-channel wireless TV receiving apparatus 210 in accordance with the preferred embodiment of the present invention is constructed to perform all the functions of the down-converter 120 and the set-top box 130 used in the prior art multi-channel wireless TV receiving system shown in Fig. 1. The TV receiving apparatus 210 is connected to an MMDS antenna 230 for receiving signals with an MMDS frequency band (2.5-2.7 GHz) , and a VHF/UHF antenna 240 for receiving signals with a VHF (54-216 MHz) /UHF (470-890 MHz) band. Accordingly, the TV receiving apparatus 210 in accordance with the present invention is constructed to receive both signals with an MMDS frequency band and signals with a VHF/UHF frequency band, but may be connected only to the MMDS antenna 230 for receiving signal with an MMDS frequency band. The TV receiving apparatus 210 converts the frequency band of a signal received through the MMDS antenna 230 into a watchable (VHF/UHF) frequency band, and provides the signal with a watchable frequency band to a TV 220. An AC

(alternating current) power adaptor 260 can be connected between the TV receiving apparatus 210 and the TV 220 through a coaxial cable employing BIAS-T, and functions to supply power to the TV receiving apparatus 210.

Furthermore, the TV receiving apparatus 210 performs additional frequency conversion to extract a signal of a frequency band, which includes control data transmitted from a CATV integrated management center, from the signal with a watchable frequency (VHF/UHF) band converted from the signal with a MMDS band. The TV receiving apparatus 210 performs the functions of subscriber ID verification, frequency band conversion and shutdown using the extracted control data.

Fig. 3 is a circuit diagram showing the detailed configuration of the TV receiving apparatus 210 shown in Fig. 2. The configuration of the TV receiving apparatus 210 shown in Fig. 3 will be described in detail below.

First, the TV receiving apparatus 210 performs a first stage of down-conversion on an RF (radio Frequency) signal received through the MMDS antenna 230 shown in FIG. 2. That is, the RF input signal is input to a band-pass filter 303, and only a part of the input signals, which has a MMDS frequency band, is passed therethrough and amplified by an amplifier 304. Although in Fig. 3, only the band-pass filter 303 and the amplifier 304 have been illustrated as existing between the input terminal for the RF signal and a mixer 305, various types of filters or amplifiers may be included therebetween according to a radio environment within a range that does not influence noise figure standards and other electrical characteristics. In the meantime, memory 328 stores programs and data used to perform the functions of subscriber ID verification, frequency band conversion and shutdown, and a CPU (central processing unit) 327 performs the functions of subscriber ID verification, frequency band conversion and shutdown by executing the programs stored in the memory 328. Furthermore, the CPU 327 controls a PLL (phase-locked loop) 325 to generate a constant tuning voltage by providing a control signal to the PLL 325, and the PLL 325 causes a first local oscillator 308 or a second local oscillator 324 to generate local oscillation signals with specific frequencies by providing the constant tuning voltage to the first local oscillator 308 and the second local oscillator 324.

In an initial stage, the first local oscillator 308 is controlled to generate a signal with a first frequency fl, e.g., 1889 MHz, or, if necessary, may be controlled to generate a signal with a second frequency f2, e.g., 1892 MHz, by shifting the first frequency fl by a frequency band of 3 MHz. After the first local oscillator 308 is set to generate the signal with a second frequency f2, the first local oscillator 308 can be set to generate the signal with the second frequency fl through 3 MHz frequency conversion, if necessary. 3 MHz, which is a frequency difference for the frequency conversion, corresponds to a half of a difference between center frequencies of two adjacent channels of a currently used CATV, and is a value set to prevent users from illegally watching CATV programs. The frequency difference for the frequency conversion can vary depending on a radio environment where the TV receiving apparatus of the present invention is used. The signal generated in the first local oscillator 308 is provided to the mixer 305. The mixer 305 mixes the output signal of the amplifier 304 with the output signal of the first local oscillator 308, thus forming a signal with an IF (intermediate frequency) (e.g., if fl = 1889, IF is 608-800 MHz) , and provides the signal with the IF to an attenuator 312. The signal input to the attenuator 312 is amplified by an amplifier 313, and the amplified signal is provided to the TV 220 as an audio/video signal. Although not shown in Fig. 3, a filter and an amplifier may be disposed between the mixer 305 and the attenuator 312 to filter out unnecessary high-frequency components, which may be generated when two signals are mixed together in the mixer 305.

In the meantime, although not shown in Fig. 3, a signal received through the VHF/UHF antenna 240 can be directly input to the TV 220 in the form of a signal with an IF on which the first stage down-conversion described above is not performed.

Meanwhile, the output signal of the mixer 305 includes control data, which will be used to perform the functions of subscriber ID verification, frequency conversion and shutdown, as well as an audio/video signal, which will be provided to the TV 220. Accordingly, a second stage of down-conversion is required to extract such control data. In order to extract such control data, a coupler 329, an amplifier 315, a mixer 317, the second local oscillator 324, a band-pass filter 318 and an amplifier 320 are included in the circuit shown in Fig. 3.

The coupler 329 extracts a carrier with a specific frequency (e.g., 650.14 MHz), which includes control data, from the output signal of the mixer 305, and provides the carrier to the amplifier 315. The signal provided to the amplifier 315 is amplified and input to the mixer 317. The mixer 317 mixes a signal with a specific local oscillation frequency (e.g., 639.44 MHz) provided from the second local oscillator 324 with the signal output from the amplifier 315, thus generating a signal with a specific frequency (e.g., 10.7 MHz), including the control data.

The signal generated in the mixer 317 is input to a demodulator 322 through the band-pass filter 318 and the amplifier 320. In this case, the carrier including the control data is a signal frequency-modulated prior to transmission at a transmitter, so that the carrier undergoes demodulation, which is a reverse conversion of the frequency modulation, at the demodulator 322, and data obtained through such demodulation is input to the CPU 327 and used for the verification of a subscriber ID and the control of the PLL 325.

In the following, a method for controlling the TV receiving apparatus in accordance with a preferred embodiment of the present invention will be described in detail. Fig. 4 is a flowchart illustrating a method for performing the functions of subscriber ID verification, frequency band conversion and shutdown through the use of the TV receiving apparatus 210 shown in Fig. 3.

First, the CPU 327 initializes variables related to the operation of the TV receiving apparatus 210 (step 402) . At this variable initializing step, the CPU 327 sets a period (e.g., 230 μs) for which it is examined whether control data is input, an initial frequency value of the first local oscillator 308 (e.g., 1892 MHz), and a value indicating ON/OFF of the function of shutdown (e.g., OFF). Thereafter, the CPU 327 controls the PLL 325 to generate a tuning voltage corresponding to the initial frequency value of the first local oscillator 308 (step 404). Consequently, the PLL 325 controls the first local oscillator 308 to generate a local oscillation frequency identical with its initial frequency. After the CPU 327 performs steps 402 and 404 as described above, the initializing steps of the method for controlling the TV receiving apparatus control method in accordance with the present invention are completed.

Thereafter, while steps 406 to 420 are repeatedly performed, which will be described in detail in the following, the functions of frequency band conversion, shutdown and subscriber ID verification in accordance with the present invention are performed.

That is, the CPU 327 examines whether control data has been input to the demodulator 322 (step 406) . Once the control data has been input to the demodulator 322, the control data is read into the memory 328 or a buffer of the CPU 327 (step S408) . Furthermore, it is checked whether the control data read into the memory 328 or the buffer has a format in conformity with a predetermined protocol (step 410).

For example, in the method for controlling the TV receiving apparatus 210 in accordance with a preferred embodiment of the present invention, a control data packet having a format, as shown in Fig. 5, may be employed. In the control data packet shown in FIG. 5, <STX> field, <GROUP> field, <ADDRESS> field, <CMD> field, <ETX> field and <BCC> field are included. Among these fields, the <STX> field may include a unique value, e.g., "FDh," indicating a head of the control data packet. Accordingly, the CPU 327 determines whether a signal input from the demodulator 322 is a control data packet having the format in accordance with the present invention by comparing the value of the <STX> field with the value previously stored in the memory 328 or the like. The <GROUP> field indicates the type of control data. For example, when the value of the <GROUP> field is "AAh, " it can be recognized that an instruction currently included in the <CMD> field is "3MHz frequency conversion" instruction.

Further, in the <ADDRESS> field of the control data packet, a subscriber ID transmitted from the CATV integrated management center is included. The CPU 327 determines whether a user currently using the TV receiving apparatus 210 is illegally watching CATV programs by comparing the value of the <ADDRESS> field with the values previously stored in the memory 328 or the like. The CATV integrated management center transmits all the IDs of current individual or group subscribers periodically or when necessary to prevent illegal watching. The TV receiving apparatus 210 determines whether the transmitted IDs having values identical with the previously stored values exist. If the value of the <ADDRESS> field does not coincide with any one of the values previously stored in the memory of the TV receiving apparatus 210, it can be determined that the user is illegally watching a CATV program.

The <CMD> field of the control data packet includes an instruction that the CPU 327 must execute immediately. The meanings of the respective bits of <CMD> field are as shown in Table 1.

<Table 1> Meanings of respective bits of CMD field

In Table 1, the error check bits (bit numbers 2 and 3) are used to check an error of the received control data packet by being compared with specific bits (e.g., bit numbers 1 and 5). The head end data (bit numbers 4-7) are not currently used, and are reserved for the addition of other functions later. The <ETX> field of the control data packet includes a unique value, e.g., "FEh," for indicating the end of the control data. Finally, the <BCC> field includes a bit value for examining whether the error of the control data has occurred. For example, the examination of whether the error of the control data has occurred can be performed as follows. That is, the value of the <BCC> field is compared with a value obtained by adding or subtracting a value, which is obtained by adding all bit values ranging from the <GROUP> field to the <CMD> field, to or from a value, which is obtained by performing an XOR operation between the values of the <STX> field and the <ETX> field. In this case, if the two values coincide with each other, it can be determined that an error has not occurred. If the two values do not coincide with each other, it can be determined that an error has occurred.

If the signal output from the demodulator 322 is a control data packet as described above, it is determined whether a current instruction indicates 3 MHz frequency conversion by examining the <CMD> field of the received control data packet (step 412) . If the current instruction indicates the 3 MHz frequency conversion, the CPU 327 transmits a control signal to the PLL 325 so that the local oscillation frequency of the first local oscillator 308 can be converted into a value (f2) shifted from the current value fl by 3 MHz (step S414). Furthermore, the PLL 325 controls the first local oscillator 308 to generate the signal with the converted frequency f2 in response to the control signal of the CPU 327. As described above, 3 MHz, which is a frequency conversion value, may vary to different values depending on the radio environment where the TV receiving apparatus 210 is used.

Thereafter, the CPU 327 compares the value of the <ADDRESS> field ^'of the received control data packet with the subscriber ID values previously stored in the memory 328 (step 416) . In this case, a case where any one of the previously stored subscriber ID values does not coincide with the value of the <ADDRESS> field of the received control data packet indicates that the person is an illegal viewer, so that the user of the TV receiving apparatus 210 must be prevented from illegally watching a CATV program by performing the shutdown function if necessary. Accordingly, the CPU 327 determines whether the currently received instruction indicates the performance of the shutdown function by examining the <CMD> field of the received control data field (step S418) . When the CPU 327 determines whether to perform the function of shutdown, the CPU 327 examines the second bit (bit number 1) of the <CMD> field of the received control data packet as illustrated in Table 1. That is, if the value of the second bit of the <CMD> field is "0", the function of shutdown is not performed. Otherwise, i.e., if the value of the second bit of the <CMD> field is "1", the function of shutdown is performed. Accordingly, if the value of the second bit of the <CMD> field is "1," the CPU 327 performs the function of shutdown, thus preventing the user from watching the CATV. The function of shutdown can be performed by controlling the attenuator 312 to reduce the intensity of signals being input to the TV 220, so that the TV 220 does not detect any signals to be input thereto.

In contrast, if the value of the <ADDRESS> field and the previously stored subscriber ID coincides with each other at step 416, or if, as a result of the examination of the value of the <CMD> field, the function of shutdown is turned off, it is not necessary to perform the function of shutdown. Therefore, the CPU 327 repeatedly performs steps 406 to 420 without performing the function of shutdown. As described above, the present invention provides the TV receiving apparatus and the control method thereof, which is capable of preventing the illegal watching of the CATV by performing the functions of subscriber ID verification, frequency conversion and shutdown using a control data packet transmitted from the CATV integrated management center. While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims .

Claims

1. A multi-channel wireless TV receiving apparatus comprising: a first down-converter for converting a signal with a first frequency band into a signal with a second frequency band; a second down-converter for converting a signal with the second frequency band into a signal with a third frequency band; a demodulator for demodulating control data, which is used for control of the TV receiving apparatus, from the signal with the third frequency band; a memory for storing variables for the control of the TV receiving apparatus; and a controller for converting a first reference frequency of the first down-converter using the control data output from the demodulator.

2. The apparatus of claim 1, wherein the first down- converter includes: a first local oscillator for generating the first reference frequency; and a first mixer for generating the signal with the second frequency band by mixing the signal with the first frequency band and the signal with the first reference frequency generated by the first local oscillator.

3. The apparatus of claim 1, wherein the second down- converter includes: a second local oscillator for generating a second reference frequency; and a second mixer for generating the signal with the third frequency band by mixing the signal with the second frequency band and the signal with the second reference frequency generated by the second local oscillator.

4. The apparatus of claim 1, wherein the first frequency band is an MMDS (multi-channel multipoint distribution service) frequency band, and the second frequency band is a VHF/UHF (very high frequency/ultrahigh frequency) band.

5. The apparatus of claim 1, wherein the control data includes an instruction to convert the first reference frequency, and/or a subscriber ID (identification) .

6. - The apparatus of claim 5, wherein the controller compares the subscriber ID with the variables stored in the memory, and stops reception of wireless signals in the multi-channel wireless TV receiving apparatus if the subscriber ID does not coincide with any one of the variables .

7. The apparatus of claim 5, wherein the controller shifts the first reference frequency of the first down-converter by a predetermined frequency magnitude according to the instruction to convert the first reference frequency.

8. The apparatus of claim 7, wherein the first frequency band is a MMDS frequency band, and the second frequency band is a VHF/UHF band.

9. The apparatus of claim 8, wherein the predetermined frequency magnitude is 3 MHz.