Abstract:
Multi-tuner receivers with cross talk reduction are disclosed. In one embodiment, a multi-tuner receiver with cross talk reduction includes a low noise amplifier, a set of interstage filters and a set of corresponding tuners. In an alternative embodiment, a multi-tuner receiver with cross talk reduction includes a passive splitter, a set of interstage filters and a set of corresponding tuners. The interstage filters can be low-pass, high-pass or band-pass filters depending on the particular frequency range of interest. Typical embodiments can have two or three tuners, however, the invention applies to multi-receiver tuners with more than three tuners. The multi-tuner receivers can be used within television, cable set top boxes and other devices that receive multiple video signals.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to video receivers, and more particularly, to multi-tuner receivers with cross talk reduction. 
   2. Background of the Invention 
   Increasingly, televisions and cable set top boxes for receiving cable television and satellite signals, including broadcast programming and Internet services, can provide the ability to receive multiple channels simultaneously. This capability permits features such as simultaneous television and Internet service, picture-in-picture displays, and distributing service to multiple rooms in one household. 
   The set top boxes and televisions for processing multiple channels require multi-tuner receivers, which extract multiple cable or satellite signals. The multi-tuner receivers select the desire channels for demodulation and further signal processing. An architecture for set top boxes or televisions requiring multiple tuners uses a passive splitter to receive and distribute an RF signal to multiple tuners. An alternative architecture for set top boxes or televisions requiring multiple tuners uses a low noise amplifier (LNA) to amplify an incoming RF signal and distribute the signal to multiple tuners. In general, there may be one or multiple outputs for the LNA with each output driving one tuner or multiple tuners in parallel. The LNA architecture avoids loss and reduction in noise figure that results when a passive splitter is used to drive multiple channels. 
   In either case, one difficulty associated with the use of multi-tuner receivers relates to the leakage of electromagnetic energy among tuners, which is often referred to as cross talk. Various signals generated in one tuner can leak from the tuner input to an LNA output, and from the LNA output to another tuner input. Such leakage can result in undesired levels of spurious signals at the output of the second tuner. This type of cross talk can also occur in a multi-tuner system using a passive splitter at the front end, since passive splitters also have finite isolation. 
   What is needed is a cost-effective multi-tuner receiver with cross talk reduction. 
   SUMMARY OF THE INVENTION 
   The invention discloses multi-tuner receivers with cross talk reduction. In one embodiment, a multi-tuner receiver with cross talk reduction includes a low noise amplifier, a set of interstage filters and a set of corresponding tuners. In an alternative embodiment, a multi-tuner receiver with cross talk reduction includes a passive splitter, a set of interstage filters and a set of corresponding tuners. The interstage filters reduce the electromagnetic leakage among tuners, and can be low-pass, high-pass or band pass filters depending on the particular frequency range of interest. Typical embodiments can have two or three tuners, however, the invention applies to multi-tuner receivers with more than three tuners, as well. The multi-tuner receivers can be used within televisions, cable set top boxes and other devices that receive multiple video signals. 
   Use of the invention can greatly reduce electromagnetic energy leakage among tuners in a multi-tuner receiver. The reduction in leakage, referred to as cross talk, can greatly increase the quality of the output signals in a multi-tuner receiver. 
   Further embodiments, features, and advantages of the invention, as well as the structure and operation of the various embodiments of the invention are described in detail below with reference to accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
     The invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. The drawing in which an element first appears is indicated by the left-most digit in the corresponding reference number. 
       FIG. 1  is a diagram of a multi-tuner receiver with a low noise amplifier. 
       FIG. 2  is a diagram of a multi-tuner receiver with a splitter. 
       FIG. 3  is a diagram of a multi-tuner receiver with a low noise amplifier, according to an embodiment of the invention. 
       FIG. 4  is a diagram of a multi-tuner receiver with a splitter, according to an embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those skilled in the art with access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the invention would be of significant utility. 
     FIG. 1  is a diagram of multi-tuner receiver  100  with a low noise amplifier. Multi-tuner receiver  100  includes low noise amplifier  110  and a set of tuners represented by tuners  120 ,  130  and  140 . The number of tuners can range from two to several hundred. Typically, the number of tuners is either two or three in current television or cable set top boxes. Low noise amplifier  110  receives an RF input, such as RF input  150 . The output of low noise amplifier  110  is coupled to each of the inputs of tuners  120 ,  130 , and  140 . The output of tuners  120 ,  130  and  140  are transmitted out of multi-tuner receiver  100 , typically to demodulators. 
   Low noise amplifier  110  receives and amplifies an RF input signal. Typically, the RF input signal can include a set of television channels in the frequency range of 50 to 860 Mhz. Low noise amplifier  110  functions also as a splitter, and distributes the incoming RF signal to each of tuners  120 ,  130 , and  140 . A tuner, such as tuner  120 ,  130  and  140 , extracts the video and audio signal for the desired channel. For example, a program transmitted on channel  2  has a video carrier at 55.25 Mhz and an audio carrier at 59.75 Mhz. Thus, when an viewer wants to view channel  2 , a tuner would extract the frequencies associated with channel  2 . 
   Multi-tuner receiver  100  has the ability to extract three different channels at a given time. Each of tuners  120 ,  130  and  140  will extract a single channel. So, for example, if a user wanted to view a picture in a picture, tuner  120  can be set to channel  2  and tuner  130  can be set to channel  3  to display two pictures. In this case, tuner  140  would not be used. As discussed in the background section, a problem with this type of receiver is interference between tuners  120 ,  130  and  140  due to leakage of electromagnetic energy that occurs among the tuners. 
     FIG. 2  is a diagram of multi-tuner receiver  200  with a low noise amplifier. Multi-tuner receiver  200  includes splitter  210  and a set of tuners represented by tuners  220 ,  230  and  240 . Multi-tuner receiver  200  is the same as multi-tuner receiver  100 , except that a splitter is used instead of a low noise amplifier to distribute the incoming RF input signal. As in the case of multi-tuner receiver  100 , the number of tuners can range from two to several hundred. Typically, the number of tuners is either two or three in current television or cable set top boxes. 
   Splitter  210  receives an RF input, such as RF input  250 . The output of splitter  210  is coupled to each of the inputs of tuners  220 ,  230 , and  240 . The output of tuners  220 ,  230  and  240  are transmitted out of multi-tuner receiver  200 , typically to demodulators. 
   Splitter  210  receives and distributes an RF input signal. Typically, the RF input signal can include a set of television channels in the frequency range of 50 to 860 Mhz. In this example, splitter  210  distributes the incoming RF signal  250  to each of tuners  220 ,  230 , and  240 . 
   Multi-tuner receiver  200  has the ability to extract three different channels at a given time. Each of tuners  220 ,  230  and  240  will extract a single channel. So, for example, as in the case of multi-tuner receiver  100  if a user wanted to view a picture in a picture, tuner  220  can be set to channel  2  and tuner  230  can be set to channel  3  to display two pictures. In this case, tuner  240  would not be used. As discussed in the background section and with respect to multi-tuner receiver  100 , a problem with this type of receiver is interference between tuners  220 ,  230  and  240  due to leakage of electromagnetic energy that occurs among the tuners. 
     FIG. 3  is a diagram of multi-tuner receiver  300  with a low noise amplifier, according to an embodiment of the present invention. Multi-tuner receiver  300  includes low noise amplifier  310 ; a set of interstage filters represented by interstage filters  320 ,  330  and  340 ; and a set of tuners represented by tuners  350 ,  360  and  370 . Multi-tuner receiver  300  addresses interference problems that were discussed with reference to multi-tuner receiver  100 . As in the case of multi-tuner receiver  100 , the number of tuners can range from two to several hundred. Typically, the number of tuners is either two or three in current television or cable set top boxes. In an embodiment, for each tuner there will be a corresponding interstage filter. 
   Low noise amplifier  310  receives an RF input, such as RF input  380 . The output of low noise amplifier  310  is coupled to each of the inputs of interstage filters  320 ,  330  and  340 . The outputs of interstage filters  320 ,  330  and  340  are coupled to the inputs of corresponding tuners. For example, interstage filter  320  is coupled to tuner  350 , interstage filter  330  is coupled to tuner  360  and interstage filter  340  is coupled to tuner  370 . The outputs from tuners  350 ,  360  and  370  are transmitted out of multi-tuner receiver  300 , typically to demodulators. 
   Low noise amplifier  310  receives, amplifies and distributes an RF input signal. Typically, the RF input signal can include a set of television channels in the frequency range of 50 to 860 Mhz. In this example, low noise amplifier  310  distributes the incoming RF signal  380  to each of interstage filters  320 ,  330 , and  340 . 
   As in the case of the previous receivers discussed, multi-tuner receiver  300  has the ability to extract three different channels at a given time. Each of tuners  350 ,  360 , and  370  will extract a video signal centered at a particular frequency. So, for example, if a user wanted to view a picture in a picture, tuner  350  can be set to the frequency for channel  2  and tuner  360  can be set to the frequency for channel  3  to display two pictures. In this case, tuner  370  would not be used. As discussed in the background section and with respect to multi-tuner receiver  100 , a problem with this type of receiver is interference between tuners  220 ,  230  and  240  due to leakage of electromagnetic energy that occurs among the tuners. 
   Interstage filters  350 ,  360  and  370  address this problem by reducing leakage of electromagnetic energy, such as crosstalk among the tuners by eliminating frequencies outside the frequency ranges of interest. The filters can be either low pass, band pass or high pass depending on the type of signal that is desired. For example, in one embodiment interstage filters  320  and  330  can be low pass interstage filters that pass signals up to a frequency of 860 Mhz, while interstage filter  340  can be a narrowband interstage filter with a center frequency in the range of 70–200 Mhz. In this embodiment, tuners  350  and  360  can be used to extract cable television video signals, while tuner  370  can be used to extract programming and control information from the control or out-of-band channel. 
     FIG. 4  is a diagram of multi-tuner receiver  400  with a splitter, according to an embodiment of the invention. Multi-tuner receiver  400  includes splitter  410 ; a set of interstage filters represented by interstage filters  420 ,  430  and  440 ; and a set of tuners represented by tuners  450 ,  460  and  470 . Multi-tuner receiver  400  addresses interference problems associated with multi-tuner receiver  200 . As in the case of multi-tuner receiver  200 , the number of tuners can range from two to several hundred. Typically, the number of tuners is either two or three in current television or cable set top boxes. In an embodiment, for each tuner there will be a corresponding interstage filter. 
   Splitter  410  receives an RF input, such as RF input  480 . The output of low noise amplifier  410  is coupled to each of the inputs of interstage filters  420 ,  430  and  440 . The outputs of interstage filters  420 ,  430  and  440  are coupled to the inputs of corresponding tuners. For example, interstage filter  420  is coupled to tuner  450 , interstage filter  430  is coupled to tuner  460  and interstage filter  440  is coupled to tuner  470 . Tuners  450 ,  460  and  470  are transmitted out of multi-tuner receiver  400 , typically to demodulators. 
   Splitter  410  receives and distributes an RF input signal. Typically, the RF input signal can include a set of television channels in the frequency range of 50 to 860 Mhz. In this example, splitter  410  distributes the incoming RF signal  480  to each of interstage filters  420 ,  430 , and  440 . 
   As in the case of the previous receivers discussed, multi-tuner receiver  400  has the ability to extract three different channels at a given time. Each tuner, such as tuner  450 ,  460  and  470  will extract a single channel. So, for example, if a user wanted to view a picture in a picture, tuner  450  can be set to the frequency for channel  2  and tuner  360  can be set to the frequency for channel  3  to display two pictures. In this case, tuner  470  would not be used. As discussed in the background section and with respect to multi-tuner receiver  200 , a problem with this type of receiver is interference between tuners  420 ,  430  and  440  due to leakage of electromagnetic energy that occurs within the tuners. 
   Interstage filters  450 ,  460  and  470  reduce leakage of electromagnetic energy, such as crosstalk among the tuners by eliminating frequencies outside the frequency ranges of interest. The filters can be either low pass, band pass or high pass depending on the type of signal that is desired. For example, in one embodiment interstage filters  420  and  430  can be low pass interstage filters that pass signals up to a frequency of 860 Mhz, while interstage filter  440  can be a narrowband interstage filter with a center frequency in the range of 70–200 Mhz. In this embodiment, tuners  450  and  460  can be used to extract cable television video signals, while tuner  470  can be used to extract programming and control information from the control or out-of-band channel. 
   Exemplary embodiments of digital headend conversion systems and methods that can be used to upconvert the frequency of a received digital television baseband signal to produce an RF multi-channel television spectrum for distribution. The present invention is not limited to these examples. These examples are presented herein for purposes of illustration, and not limitation. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the present invention.