Patent Application
20120225626
The present invention generally relates to a system and associated method for providing attenuation of a received signal in a two-way communication circuit without the use of a separate switchable attenuator. Specifically, the attenuation provided by a transmit/receive switch set to the transmit position during reception is used to provide attenuation to a signal reception path.
This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Television programming is commonly received from satellite or cable sources. Received signals are generally delivered through the home via coaxial cable to a set-top box associated with a television display device. In some environments, multiple set-top boxes are present, each generally connected to a separate display. One or more of the set-top boxes may contain digital video recorder (DVR) capability. A user of one of the set-top boxes may wish to view programming that has been recorded on another set-top box. To facilitate such viewing, various networking schemes, such as the Multimedia over Coax Alliance (MoCA™) standard, have been created to allow one set-box to display content provided by another.
In some cases, the signal received from another set-top device may be stronger than desired for reliable reception. Attenuation of the received signal may therefore be required before the signal is processed by the receiving circuitry. The addition of a switchable attenuator to the set-top box circuitry, however, can add to the cost, complexity, and size of the set-top box. A method is therefore needed to reduce cost by eliminating the need for a switchable attenuator by employing an already existing portion of the circuitry. The invention described herein addresses this and/or other problems.
In order to solve the problems described above, the present invention concerns a system and associated method for providing attenuation of a received signal in a two-way communication circuit without the use of a separate switchable attenuator. Specifically, the attenuation provided by a transmit/receive switch set to the transmit position during reception is used to provide attenuation to a signal reception path. This and other aspects of the invention will be described in detail with reference to the accompanying Drawings.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent, and the invention will be better understood, by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
The exemplifications set out herein illustrate preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
As described herein, the present invention provides a system and associated method for providing attenuation of a received signal in a two-way communication circuit without the use of a separate switchable attenuator. Specifically, the attenuation provided by a transmit/receive switch set to the transmit position during reception is used to provide attenuation to a signal reception path.
While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
The present invention may be implemented in a set-top box or video decoder that is capable of receiving satellite signals, cable television signals, or other transmitted television signals. The signals may comprise encoded packets of data representing video and audio information in compressed form. The signals are encoded such that a video signal can be generated and viewed upon being properly decoded.
Satellite 110 receives signals from uplink transmitters and then rebroadcasts the signals back to earth using a set of transponders utilizing a variety of transmission frequencies. The altitude of the transmitting satellite 110 allows subscribers in a wide geographical area to receive the signal.
The distance from the earth and the severe power conservation requirements of the satellite result in a relatively weak signal being received at the antenna 120. It is therefore critical that the signal be amplified as soon as possible after it is received by the antenna. This requirement is achieved through the placement of a low noise block downconverter (LNB) 130 at the feed horn of the parabolic dish antenna 120. In a simple single set-top box configuration, the selected signal from the LNB 130 may travel along a coaxial cable to a digital satellite set-top box 140, which tunes a desired channel for presentation on television display device 150.
In more complex installations, a single-wire multi-switch (SWM) 135 may be used to multiplex signals from multiple LNBs and their multiple polarities onto a single coaxial cable for delivery into the home. Splitters 145 and 165 may be used to split the signals to cables running to other set top boxes 160 and 180, connected to television display devices 170 and 190, respectively. A similar configuration may exist in a cable-based installation. A single feed from the local cable distribution system may enter the house and be split to coaxial cables running to multiple cable set-top boxes.
The cabling and splitters used to carry received satellite signals from SWM 135 to set-top boxes 140, 160, and 180, and carry control information back to the SWM 135, may also be used for communication between set-top boxes. For instance, a set-top box 140 containing a DVR may provide access to recorded content to other set-top boxes 160 and 180 in the home. The Multimedia over Coax Alliance (MoCA™) standard describes one method of providing such functionality. In the case of a satellite television system, these digital home networking (DHN) communications between boxes occur at frequencies below those for SWM-to-set-top communications. In the case of cable, DHN communications may occur at frequencies above those of the cable television transmissions. A band-stop filter may be present within or near SWM 135 to prevent interference of DHN communications with satellite signal reception and processing.
In this example, the set-top box provides an additional connection for a legacy non-SWM LNB feed. The LNB signal is fed through a high-pass filter 206, balanced by balun 264, and then also processed by the satellite analog front end 260. In most cases, if an SWM is feeding the primary input, this additional LNB connection will not be used.
The satellite SoC is connected via a bus to the DHN data path 210. The DHN path provides two-way communication between set-top box 200 and other set-top boxes or other devices. A band pass filter 212 provides bidirectional filtering and passes the incoming and outgoing data signals. A transmit/receive switch 215 is used to switch the DHN path between transmission and reception modes. Switch 215 is controlled by the DHN firmware and provides a low-loss connection for the selected data path. An amplifier 225 amplifies signals to be transmitted. Baluns 230 and 232 provide conversion from unbalanced to balanced signals, and vice-versa, for received and transmitted signals, respectively. Up/down converter 235 converts signals to an appropriate frequency band for either transmission to another set-top box or processing by the DHN system IC 240.
In the receive path, a switchable attenuator 220 is used to attenuate received data signals when required, for instance, when the signal level is above the linearity limitations of the receiver. An example of such an attenuator is the MaCom AT267. Typical attenuation requirements may be in the range of 15 dB-25 dB, depending on the transmission power of the DHN system, though more or less attenuation may be required.
The switchable attenuator 220 may add cost, complexity, or size to the DHN path and the set-top box. It would therefore be desirable to eliminate the need for the switchable attenuator.
In accordance with the present invention, it is possible to eliminate the switchable attenuator 220 by selectively utilizing the attenuation of the signal provided to the reception path by the TX/RX switch 215 when the switch is set to the transmission position. This may advantageously reduce the complexity, cost, and/or size of the set-top box electronics.
A switchable attenuator corresponding to element 220 of
Thus, the subsystem of
While the present invention has been described in terms of a specific embodiment, it will be appreciated that modifications may be made which will fall within the scope of the invention. For example, various processing steps may be implemented separately or combined, and may be implemented in general purpose or dedicated data processing hardware or in software. Furthermore, while the present invention has been described with respect to communication between set-top boxes, the technique of using a switch to provide attenuation to a path which is not selected by that switch may be used in other data communication contexts.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US09/06150 | 11/17/2009 | WO | 00 | 5/16/2012 |
