Abstract:
A method and device for adapting an existing analog television receiver to receive and decode both analog and digital television signals. A digital module is provided within the analog television receiver and its output is provided to the picture-in-picture (PIP) interface of an analog module within the receiver. The digital signal then has the benefit of using the picture improvement circuitry located within the analog module and there is no need to modify the analog module which has been in the cost optimization process for years.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to integrated analog/digital television receivers and in particular to a low cost method and device of providing a digital television receiver module in an existing analog television receiver. 
     2. Description of the Prior Art 
     Digital television services are presently being provided along with analog television services. During the time period of changeover from analog to digital it is necessary to have televisions which are able to operate in both the analog and digital environment. 
     The introduction of these digital television (“DTV”) services presents architecture issues to the design of integrated digital/analog TV products. Since the initial integrated digital/analog television production volume is low, it does not make commercial sense to alter existing analog television components to accommodate functional integration of DTV components. This is because conventional analog television has been on the cost optimization process for many years and the fundamental analog architecture development has been following the functional integration path. More and more digital processing technologies have gradually replaced analog techniques for better performance and featuring and the analog functional integration is on the path toward a single IC execution with tightly coupled functionality and cross-sharing of processing blocks. While this approach enables the continued cost optimization of a conventional analog television set, the integration of DTV with analog TV poses a significant cost penalty. DTV employs compression-based techniques and it does not share much commonality with analog signal processing. To fully integrate DTV with conventional analog TV functionality based on existing analog chassis requires modifications to the analog chassis that are expensive. If the analog chassis is not modified, then in order to integrate DTV with the analog TV and have a high quality DTV signal, duplicate circuitry is needed so the output of the DTV module can be supplied directly to the display, thereby bypassing the analog chassis. 
     FIG. 1 shows a television  4  which includes an analog chassis  10  and a picture-in-picture (PIP) module  20 . The traditional analog chassis  10  is an integrated circuit with a limited number of inputs and outputs including i) RF in  3  ii) the AV jack panel  2  attached directly to the analog chassis comprising AV 1  in and AV 2  in, iii) the host controller  19  inputs and outputs for control of all modules within the analog chassis  10  and PIP module  20 , vi) the output to display  5 , and vii) the inputs  11  and outputs  12  associated with the PIP functionality (“PIP interface”). Included within the analog chassis  10  is a tuner  15 , an analog decoder  16 , a multiplexer  18  and picture improvement circuitry  17 . In order to incorporate the DTV module  30  in the present integrated analog/DTV receivers the DTV module  30  includes duplicate picture improvement circuitry  38  and the signal is multiplexed through multiplexer  40  on the output of the analog chassis  10  so that redesign of the analog chassis  10  is not necessary. Because the duplication of the picture improvement circuit is so expensive, many times this duplication is not even included in the design and the un-improved DTV signal at the output of the digital decoder  37  is provided directly to the display  5 . 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a low cost digital/analog television which does not necessitate redesigning the analog chassis and also enables the use of the same picture improvement circuitry in the analog chassis for the DTV signal. This object is achieved by providing a switched signal to the PIP interface of the analog chassis. 
     It is another object of the invention to provide a switched digital PIP input signal to the analog chassis, while preserving the same user experience with respect to the analog PIP. Thus digital PIP is an added feature without requiring the user to learn to operate additional keys on the remote control to turn on the digital PIP. 
     Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification. 
     The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     For a better understanding of the invention, reference is made to the following drawings. 
     FIG. 1 shows a prior art integrated analog/DTV receiver; 
     FIG. 2 shows a preferred embodiment of the instant invention; 
     FIG. 3 shows a remote control in accordance with a preferred embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2 shows a preferred embodiment of the instant invention. A television  4  is provided with an analog chassis  10 , a PIP module  20  and a DTV module  30 . The analog chassis contains a tuner  15 , an analog television demo/decoder  16  and picture improvement circuitry  17 . The tuner  15  processes terrestrial broadcast channels in the UHF and VHF bands. The tuner is controlled by the host controller  19  to select any channel out of the RF spectrum. The analog television demo/decoder  16  rejects interference from picture and sound carriers in adjacent channels and separates out the sound carriers and synchronization signals from the video of the tuned channel. The picture improvement circuitry  17  improves the brightness, contrast etc. of the video signal before it is displayed on the display  5 . A multiplexer  18  within the analog chassis  10  selects between the output of the analog decoder  16  and the PIP functionality. 
     The input  3  of the analog chassis is coupled to an antenna or NTSC coaxial cable or some other analog video source. The jack panel  2  attached directly to the analog chassis  10  receives alternative or legacy video source inputs from such as VCR, DVD, etc. The host controller  19  provides control functionality for analog chassis  10  components, PIP module  20  components and DTV module  30  components. Multiplexer  18  has an input  11  for the output of the PIP module  20  for providing the composite PIP main signal  28 . There is also an output provided to the display  5  for deflection circuitry and audio amplifiers. 
     The PIP module  20  accepts a plurality of inputs and includes a tuner  25  (although less expensive sets use the tuner from the VCR or some other video source) which selects any channel from the RF spectrum. An analog television demodulator/decoder  26  within the PIP module  20  rejects interferences from picture and sound carriers in adjacent channels and separates out the sound carrier and synchronization signals from the video of the tuned channel. The PIP IC  27  scales the video to 1/16 or 1/9 (or other arbitrary ratio) of its original size and combines the main signal  12  with the PIP signal received from analog decoder  26  such that the output of the PIP IC  27  contains a MAIN picture (from the analog chassis  10 ) with a smaller sub-picture in one quadrant (typically). The multiplexer  18  selects between the signal input from analog decoder  16  and the signal from the PIP module  20  provided on input  11 . 
     One of the few inputs to the analog chassis is the PIP interface  11 . Typically this input is reserved for the output of the PIP module  20 . The multiplexer  18  switches between either the main signal from the analog decoder  16  or the composite PIP signal from PIP module  20 . This PIP interface to the analog chassis  10  comprises one A/V output  11 , one input  12  and I 2 C control from host controller  19 . The PIP function in general is achieved by processing any of the two A/V inputs  22  to comprise a smaller combined video for output back to the analog chassis. 
     The digital television module  30  includes a digital tuner module  35  which receives digital ATSC broadcasts, performs IF filtering to reject adjacent channel interference and outputs a first or second IF signal to a digital demodulator  36 . The digital demodulator  36  recovers the pilot carrier and clocking information, demodulates the symbols from the signal and decodes it. The output of the demodulator  36  is an ATSC transport stream containing audio, video and other kinds of data. The digital decoder  37  processes the transport stream to separate out and decode the transport stream. The output of the digital module  30  is provided to the multiplexer  50 . Multiplexer  50  selects either the DTV signal from DTV module  30  or the PIP signal  28  from PIP module  20 . 
     As can be seen from FIG. 2, the DTV module  30  does not include the duplicate picture improvement circuitry as seen in FIG. 1 but takes advantage of the picture improvement circuitry  17  already available in the analog chassis  10  without modifying the analog chassis  10 . In this application the DTV video is picture-enhanced by the existing analog improvement circuitry  17  on-board the analog chassis  10 . Even though, it is not optimal to use analog picture improvement circuitry on a DTV signal, the overall viewer experience is preserved due to unified control and processing of video in the truest sense of an integrated TV and it provides an improved picture without the extra expense. In addition since a low cost integrated DTV typically will not have the display capability that is appropriate for HDTV video, any loss due to lower-performing picture improvement circuitry on the analog chassis is not very apparent. To achieve this result, the television  4 , is provided with an additional multiplexer  50 . This permits the PIP input  11  to be used for both PIP television and DTV as explained below. 
     The PIP module  20  has an output  28  that is provided to multiplexer  50 . The DTV module  30 , without additional picture improvement circuitry, also provides an output  39  to multiplexer  50 . Multiplexer  50  selects between the analog PIP signal  28  or the DTV signal  39 . The analog chassis  10  still sees only one signal on its input  11  from multiplexer  50 . If the DTV signal is selected by multiplexer  50  it gets the use of the analog chassis picture improvement circuitry  17 . This improvement allows for the clean, cost effective addition of a DTV module without the necessity of “breaking” into the analog chassis  10  and without adding additional picture improvement circuitry or alternatively displaying a much lower quality DTV signal. The digital TV decoder module  30  is thereby added as an additional A/V source to the analog chassis. The control of DTV reception and decoding is also performed by the host controller  19  located on the analog chassis. 
     Another benefit of the present invention is that it is not necessary to modify the PIP module  20  to accommodate the DTV signal if it is not cost effective to do so. Although if one wishes to add the multiplexer or switch  50  in the PIP module  20  this can also be an option. 
     The DTV decoder output  39  can also be a source for the PIP. This is achieved by adding a multiplexer  51  to select between the main and DTV module output for additional PIP featuring. The multiplexers  50  and  51  can be located on the DTV module  30  so that it is not necessary to modify the analog chassis  10  or PIP module  20 . 
     Operation of the television is explained as follows. A remote control  60  is provided to control the functionality of the television. This remote control contains all of the typical features of a remote control including channel up/down  61 , volume up/down  62 , power on/off  63 , PIP on/off  64 , input selectors  65  and numerical keys  66  etc. The remote control also contains a DTV on/off button  67 . If the PIP button  64  is depressed the tuner  25  provides an additional program to the PIP IC  27 . The multiplexer  50  then selects the output  28  of the PIP module as the input  11  to the analog chassis. The multiplexer  18  of the analog chassis selects the PIP input  11  as the input to be displayed. The buttons of the remote control  60  then control the functionality of the smaller PIP picture such as changing the channel. If the DTV button  67  is depressed the remote control  60  controls the DTV picture by causing the digital tuner  35  to select the requested DTV program. The DTV program is then provided to the multiplexer  50  and the multiplexer  50  selects the output  39  as the input  11  to the analog chassis  10 . The multiplexer  18  then selects the DTV signal as the signal to be displayed. The instant invention thereby provides a user friendly DTV experience. 
     It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above method and in the construction set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall not be interpreted in a limiting sense and the scope of the invention shall be set forth in the claims.