WO2006117583A1

WO2006117583A1 - System for receiving and processing television signals

Info

Publication number: WO2006117583A1
Application number: PCT/IB2005/001014
Authority: WO
Inventors: Hayati V. Kamhi
Original assignee: Farimex S.A.
Priority date: 2005-04-29
Filing date: 2005-04-29
Publication date: 2006-11-09
Also published as: ITTO20050108U1; TR200504148U

Abstract

The present invention relates to a system for receiving and processing television signals comprising a tuner, a SAW filter, a television signals processor (101) for providing video, audio and synchronisms signals and a microcontroller; the invention also relates to a television set comprising said system. The invention is characterized in that said system is assembled on a single board inside a metallic box.

Description

SYSTEM FOR RECEIVING AND PROCESSING TELEVISION SIGNALS

DESCRIPTION

The present invention relates to a system for receiving and processing television signals according to the preamble of claim 1 and to a television receiver comprising said system.

Systems for receiving and processing television signals are known since the invention of the television.

In order to receive and display a TV signal, TV receivers comprise a main board on which is contained, among other components, a tuner, an amplifying circuit at intermediate frequency, a processor detecting audio and video signals and a microcontroller . At the present state of the art, the tuner is usually assembled inside a metallic box that shields the components (capacitors, coils etc..) from external signals and avoids irradiating signals to the outside.

The tuner is considered to be a critical component of the television receiver: at radio frequency, capacitors and inductances cannot be considered as concentrate elements, so the bigger is the tuner, the harder is to have always a good tuning on the desired TV channel.

In order to improve the performances of tuners, both the dimension of the components and of the board have been reduced. Nowadays the tuner is made with SMD (surface mounted device) components and integrated circuits, exception made for some capacitors and coils. The global dimension of the tuner are thus kept very small.

The tuner, together with other components as for example the power supply, the integrated circuits for the video processing and the microcontroller, is installed on a main board inside the chassis of the television receiver. In order to provide a plurality of different and always new products on the market, manufacturers of television sets have proposed television sets that integrate also DVD/DIVx/VideoCD/mpeg readers or DVD+RW modules; such products are known on the market as Combi TV. The integration of a DVD reader requires space for the loaders and for the additional electronics that has to be mounted on the main board of the television set. As competition increases on the market, manufacturers have both the necessity for reducing costs, especially with regards to manufacturing time, and the necessity to provide appliances integrating always more functionalities.

A first aim of the present invention is to disclose a system that requires shorter manufacturing times, and consequently lower costs, as compared to the prior art.

Integrating new functionalities into the same television receiver, presents several problems, between those the availability of space on the main board for electronics circuitry that has to be added in order to support the additional functionalities.

Such a problem is bigger especially for small screen television sets (14-15 inches), wherein there's not sufficient place on the main board to add multiple modules such as DVD+RW board and DVB board at the same time.

Usually, on the main board there is enough space for the Loader and the MPEG board, but there is no space left for additional modules such as DVB boards,

JPEG&Photo viewer boards, and any other modules, which can bring an additional feature to the combi TV product.

The use of existing combo loaders (integrating the MPEG board inside the loader) is not useful since they have considerable higher width than the separate loader and

MPEG board combination.

It is thus a further aim of the present invention to solve the problem of space availability on the main board of television receivers, particularly on small screen television sets.

The above aims are solved according to a system and an apparatus comprising the features of the enclosed claims, which form integral part of the present specification.

Further aims and advantages of the present invention will be clear from the following specification and from the enclosed drawings (which present non limitative embodiments of the present invention) wherein:

Fig. 1, shows a television set.

Fig. 2, shows a schematic representation of the main board of a television receiver according to the prior art. Fig. 3, shows a schematic representation of the main board of a television receiver according to the invention.

Fig. 4, shows a schematic representation of a system for receiving and processing television signals according to the invention. Figure 1 shows a television set 1 that, as known to any person skilled in the art, comprises a screen 2 for displaying the television signals broadcasted and received from an antenna 3.

In order to receive and process television signals, the television set is provided with a main board 4 on which are mounted several electric and electronic components for receiving television signals, processing them according to control signals received from a local or remote controller and displaying the relative images. For sake of simplicity, the connections between said main board 4 and the other components (e.g. the Cathode Ray Tube if it is the case of a CRT television) of the television set 1 are not shown in figure 1 since they are known to any person skilled in the art of television sets.

As an example, the main board 4 according to the state of the art is schematically shown in figure 2; said main board 4 comprises:

• a power supply module 5 that provides different power supplies for the different components of the main board.

• A tuner 6 that receives the television signals and tunes the television set on a desired channel; the tuner 6 receives RF signals from the antenna 3 and outputs a signal at an intermediate frequency IF that depends upon the standard (e.g. PAL, NTSC). The tuner 6 has a very compact design and is contained inside a metallic box that is usually mounted on the main board in vertical position. The tuner 6 comprises a surface acoustic wave (SAW) filter.

• A television signals processor 7 that receives the television signals at intermediate frequency (IF) amplify and process them in order to extract the RGB video signals, the audio signal and the horizontal and vertical synchronisms.

• A sound processor 8 that processes the audio signal received by television signals processor.

• Horizontal 9 and Vertical 10 deflection modules that comprise the circuitry for operating the Cathode Ray Tube of the television set. • A memory area 11, usually an electrically erasable programmable read only memory (EEPROM) for storing the settings of the television set.

• A microcontroller 12 that receives the inputs of the user (e.g. from an infrared remote controller or from a control panel) and controls the tuner 6, the television signals processor 7, the sound processor 8, the vertical 10 and horizontal 9 deflection modules. The microcontroller 12 is connected to the memory area 11 for accessing the data contained therein.

In order to connect all the components of the main board, a plurality of cables and connections (jumpers, printed lines, etc ..) are required. These connections presents several disadvantages since the longer and the more the connections, the higher the costs (material and mounting during the manufacturing phase) and the electromagnetic compatibility (EMC) problems.

In order to save space on the main board, for example to add further electronics for additional functionalities of the television receiver, an immediate and obvious solution would be that of using vertical boards to increase the overall surface supporting electronic components.

This solution does not proves to be effective and creates problems to keep the set conform to EMC requirements. The present invention discloses a television set comprising a main board on which is mounted an improved system for receiving and processing television signals; said system being assembled on a single board inside a metallic box and comprising a tuning module, a SAW filter, a television signals processor and a microcontroller. The television set and the system for receiving and processing television signals according to the invention, provides several advantages like saving space on the main board 4, reducing the costs for manufacturing the television set and improving the electromagnetic compatibility level of the set.

Figure 3 shows the main board 400 of a television set according to the present invention. As it can be easily seen comparing figure 2 and figure 3, the main board 400 is simpler and presents less components with respect to the main board 4; this means that additional space is available on the main board 400 for further electronic modules that support further functionalities of the television set. The main board 400 comprises a system 401 for receiving and processing television signals, horizontal 402 and vertical 403 deflection modules, a sound processor 404 and a power supply module 405.

A schematic representation of the system 401 for receiving and processing television signals according to an embodiment of the invention is presented in figure 4, wherein the four main blocks composing the system 401 are presented. The deflection modules 402 and 403 and the sound processor 404 are connected in known way to relative actuators not shown in figure 4; these connections are indicated by dashed arrows.

The system 401 for receiving and processing television signals according to the present invention comprises a tuning module 100 which is used to receive RF television signals, a television signals processing unit 101 to extract RGB and CVBS video signals, a microcontroller unit 102 to control of all the basic processes in a TV set and a SAW filter 103 to extract the television and sound signals required for the television signals processor 101 and sound processor 104 from the output of the tuning module 100. The above said modules could be obtained with the use of the following integrated circuits:

- STV2238 from ST Microelectronics, for the television signals processing unit 101

- ST92195 from ST Microelectronics, for the microcontroller unit 102

- 6509A from PHILIPS ELECTRONICS for the tuning module 100 The system 401 for receiving and processing television signals is totally shielded by a metallic box 104 and therefore protected from interferences which will come from the power supply elements present on the main board and from external interferences coming from mobile phones or other electronic external devices. As a whole, the system 401 for receiving and processing television signals results in a compact unit receiving as input the RF signals from an antenna and the different supply lines (indicated in figure 4 with exemplificative values like 5 V, 30V, 8 V ...) for the different components (tuning module, television signals processor, micro controller) of the system. The output of the system 401 are the video (RGB and CVBS) and audio signals at band base frequency, the signals for the horizontal (H.DRV) and vertical (V.DRV) deflections. The system 401 is also connected bidirectionaly to an I²C bus.

Assembling all the above elements inside a single compact unit, creates several technical problems that have to be overcome. As already said, RF components are very sensitive to interferences and the presence of integrated circuits working with square signals, like the microcontroller 102 and the television signals processor 101, or oscillators, like the quartz oscillating at 4.43 MHz for detecting the colour in the television signal according to the PAL broadcasting standard, can create interferences that reduce the sensibility of the tuning. In order to reduce the problem of interferences, several provisions shall be taken; as an example, the tuning module 100 is separated from the other components of the system 401 by a square metallic shield 105 that reduces the interference. Since the currents and voltages inside the integrated circuits create low amplitude signals, and at the same time the operation frequency is much lower than the signal frequency in the VHF and UHF band, the interference has resulted to be weaker than expected, and a metallic shield that reduces of 5-10 db (preferably in the band from 30-900 MHz) the interference has proved to be effective for the present application. In order to reduce the interference which occurs due to the square waves generated by the integrated circuits and the 4.43 MHz oscillator, it is necessary to keep all the components of the system very close: distances in the printed circuit board of the system 401 have to be shortened and ground line is adopted to separate elements and signal lines on the main board. In a preferred embodiment, the SAW filter and the television signals processor are mounted close to said metallic shield, while the microcontroller 102 is more distant with respect to the tuning module 100 compared to the SAW filter 103 and the television signals processor 101.

Since the length of the lines carrying the RF signals between tuning module 100 and SAW filter 103 and between SAW filter 103 and television signal processor (101) is reduced with respect to the prior art, the present ionvention provides for good results with respect to EMC problems.

In the embodiment shown in figure 4, in order to improve the system 401, a section 106 the ground line surrounds the SAW filter; further sections of the ground lines can be adopted to surround IF output lines of the tuning module 100. An advantageous solution that allows a further improvement of the present invention, is to add to high pass filters at the RF input of the tuning module 100 in order to prevent the interference from the quartz circuitries entering into the tuner. A further advantageous solution according to the invention is to use power decoupling devices to prevent interference among components coming from the power supply lines.

High frequency filter units (ceramic capacitors) as well as coils are used close to the integrated circuits' power supply input pins and to the tuning module voltage inputs in order to reduce interferences and improve the overall operation of the system 401 for receiving and processing television signals. The high frequency filters obtained through said capacitors, are adapted to pass all the useful signals and to cut the undesired frequencies, to this purpose, the suppressive frequency is around few MHz, so that only the lower frequencies, like the supply voltage, pass. In a preferred embodiment, such filters are provided to cut signals with unwanted frequency, particularly from 1OkHz to 2MHz

Further problems can arise from the mutual interference between signals and synchronisms of the composite video signal; in order to solve such problems, parallel layout between lines carrying the signals and the synchronisms shall be avoided. Further improvements to solve such a problem can be obtained enlarging the distance between the lines and/ or adopting the ground line to separate signal lines and lines for the synchronisms.

Good results can be achieved by increasing from four to five times the usual distance between the lines carrying the signals and the synchronisms; preferably the distance between the lines shall be from 1.6 mm to 2.0 mm. The combinative use of such technical solutions for preventing interference problems inside the system 401, results in a system that, once mounted on the main board, provides for a television set with less problems of EMC. Compared to a standard television set, there are less integrated circuits, less cables and less printed lines on the main board, hence less unshielded components that are subject to EMC problems. As it is clear from the above description, the system 401 for receiving and processing video signals allows to save space on the main board 400.

Saving space, it is possible to add other functionalities to the television sets with lower manufacturing costs if compared to the known solutions. As an example, suppose that a DVD+RW has to be added to the television set, in this case there is a need for a second tuning module that enables the interaction of the main board with the DVD+ RW board.

Since in the known solution there's no space left on main board, this second tuning module has to be made on a board which has to be added on the main board as a separate vertical board (very critical because of space problem) or more realistically as a second horizontal board mounted on the top of the main board and connected to said main board by means of cables.

In any case a separate printed circuit board (PCB) is needed, connectors and cables are needed to connect it on the main board and on the DVD+RW board, some plastic housing is needed to put it on the main board and this board should also be shielded to prevent it from the interference with the power supply (FBT transformer) since it is close to the power supply module due to the space limitations. In addition vertical modules put on the main board are not very reliable from the point of view of contacts. Using the system according to the present invention, space problems are solved and the second tuning module can be directly realized on the main board using for example SMD devices.

Therefore the system according to the invention allows to eliminate several components, e.g. the separate PCB board for the second tuning module, connectors and cables which are needed to connect said second tuning module to the main board and the plastic housing that is needed to fix the separate PCB board on the main board.

In addition, since the second tuning module can be implemented on the main board, it can be placed far away from the supply module, so it is not necessary to shield it, and a further cost reduction can be obtained eliminating the metallic shield required by the prior solutions.

Notwithstanding that the above example has been taken in the case of the addition of a DVD+RW feature to a television set, it will be apparent to those skilled in the art that the present invention can be applied to add further different features on the television set, like for example the case in which a digital video broadcasting (DVB) is added.

A television set according to the invention, can thus comprise electronic means allowing the implementation of an additional feature with respect to a standard television set; said electronic means can be provided directly on the main board, for examples using at least in part SMD (surface mounted device) devices, which are small and require few space.

It is clear that many other variants can be achieved by the person skilled in the art without departing from the present invention as described and as claimed. For example additional other methods for avoiding interferences between the modules assembled on the main board can be used, as well as technologies that reduce the size of the electronic components.

Claims

1. System for receiving and processing television signals comprising a tuning module (100), a SAW filter (103), a television signals processor (101) for providing video, audio and synchronisms signals and a microcontroller (102), characterized in that said system (401) is assembled on a single board inside a metallic box (104).

2. System according to claim 1, characterized in that said tuning module (100) is separated from other components of the systems by a metallic shield (105).

3. System according to claim 2, characterized in that the SAW filter (103) and the television signals processor (101) are mounted close to said metallic shield (105).

4. System according to claim 3, characterized in that capacitors and/ or coils are connected to the power supply inputs of said tuning module (100) of said television signals processor (101) and of said microcontroller (102).

5. System according to claim 4, characterized in that said capacitors and/ or coils have a value adapted to cut signals with unwanted frequency, particularly from 10kHz to 2MHz.

6. System according to any of the previous claims, characterized in that said system comprises high pass filters at the RF input of the tuning module.

7. System according to any of the previous claims, characterized in that a section (106) of a ground line surrounds said SAW filter

8. System according to any of the previous claims, characterized in that a section (106) of a ground line surrounds IF output lines of said tuning module.

9. Television set comprising a system for receiving and processing television signals according to any one of the claims from 1 to 8.

10. Television set according to claim 9, characterized in that electronic means allowing the implementation of an additional feature with respect to a standard television set, is provided directly on the main board.

11. Television set according to claim 10, characterized in that said electronic means comprise surface mounted device (SMD).

12. Television set according to claim 10, characterized in that said electronic means comprise an additional tuning module.