Abstract:
A satellite receiver is switchable between an operating mode wherein the receiver is capable of generating an output signal using received signals from one or a plurality of satellites, aid another operating mode wherein the receiver generates an output signal using signals received from only one satellite. The former operating mode is useful when the receiver is operating in a mobile environment. The latter operating mode is useful when the receiver is operating in a fixed environment. The receiver is configured to detect the mode in which it is operating. The receiver comprises at least two recevier arms for processing a broadcast signal from a selected one of two satellites. The receiver disables one of the arms when the receiver is stationary.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Related subject matter is disclosed and claimed in co-pending patent U.S. patent application Ser. No. 09/263,207, filed by Stelios Patsiokas on Mar. 5, 1999; and in a co-pending U.S. patent application Ser. No. 09/310,352, filed by Anh Nguyen et al on May 12, 1999; both of said applications being expressly incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for switching a satellite receiver between two operating modes depending on whether the receiver is stationary or mobile. 
     BACKGROUND OF THE INVENTION 
     Satellite digital audio radio service (SDARS), a satellite broadcast service established by the U.S. Federal Communications Commission (FCC), has been proposed using satellite transmission of digital audio programs to radio receivers. The radio receivers can be stationary receivers, in which case a receiver antenna can be pointed for optimal line of sight (LOS) reception from a satellite. In contrast, the position of the receiver antenna relative to the satellite changes with mobile receivers (e.g., a receiver that is hand-carried by a user or is mounted in a vehicle), and LOS reception from one satellite is not always available. Accordingly, mobile receivers are generally configured to receive broadcast signals from more than one satellite. 
     Service outages can occur in systems which broadcast data, video, audio and other information using radio frequencies. These outages can prevent receivers, and particularly mobile receivers, from receiving the broadcast service altogether, or cause them to receive a signal so degraded that the service is rendered unacceptable. These outages are generally due to physical blockage of transmission paths between the transmitter and receiver (e.g., due to mountainous terrain or long tunnels) and multipath fading and reflection of the transmission path. Satellite broadcast systems can use two transmission channels to provide diversity for mitigating service outages due to multipath, physical blockages and interference in mobile broadcast receivers. Terrestrial repeaters can also be provided to repeat satellite signals in geographic areas where LOS reception is obscured by tall buildings, hills and other obstructions. 
     The receivers are configured with first and second receiver arms for receiving signals transmitted from the respective satellites. The recovered data streams from the satellites can be used singly or optimally combined. In satellite systems that are reinforced with terrestrial repeaters, the receiver can also be configured for dual-mode operation to receive both satellite signals and terrestrial signals and to combine or select one of the signals as the receiver output. When the receiver is stationary, only one of the satellite signals is generally required. When the receiver is in a mobile environment, the option of using one or plural received satellite signals for output signal generation is advantageous, particularly when no terrestrial repeater signal is available. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a satellite receiver is switchable between an operating mode wherein the receiver is capable of generating an output signal using received signals from one or a plurality of satellites, and another operating mode wherein the receiver generates an output signal using signals received from only one satellite. The former operating mode is useful when the receiver is operating in a mobile environment (i.e., installed in a vehicle). The latter operating mode is useful when the receiver is operating in a fixed environment (e.g., installed at a user&#39;s home or otherwise operated at a stationary position). 
     In accordance with another aspect of the present invention, the receiver is configured to detect the mode (i.e., fixed or mobile) in which it is operating. The receiver comprises at least two receiver circuit arms. Each arm is configured for receiving, downconverting and demodulating a broadcast signal from a selected one of the satellites. The receiver is operable to disable at least a portion of one of the two arms when the receiver operating mode corresponding to fixed or stationary use is detected. 
     The mobile or fixed mode can be detected depending on whether the receiver is powered on via a DC power supply (e.g., 12 volts or greater from a vehicle battery via the cigarette lighter receptacle or power receptacle) or a residential power supply circuit (e.g., AC power or DC power of 9 volts), respectively. A circuit is provided to detect the signal level from the power source and operate a relay which selectively enables and disables components in respective receiver arms. 
     The mode can be detected depending on the position of a switch operated by a user. The receiver can also be operated in conjunction with a pedestal base which actuates a switch or detector in the receiver. The pedestal base is installed in a vehicle (e.g., on the dashboard of the vehicle). The switch or detector is actuated when the portable receiver is placed on the pedestal. 
     In accordance with yet another aspect of the present invention, the receiver is provided with a power supply sensor for determining if the receiver is operating in a stationary or mobile environment. The receiver is provided with an AC power port for connection via a power cord to an AC power outlet. The receiver is also provided with a DC power port for connection to a DC power source such as a car battery via the cigarette lighter receptacle or power receptacle. One or both of the ports can be provided with a mechanical, magnetic, electromagnetic, semiconductor, electronic or other type of switch or detector that is actuated when the port is connected to its corresponding power source. 
     In accordance with still another aspect of the present invention, the receiver can also be provided with a motion sensing device. The motion sensing device can be implemented as a vibration sensor (e.g., for sensing when the receiver is being subjected to vibrations induced by a vehicle engine or contact of the vehicle with a road surface), an encoding compass or heading indicator, an encoding gyroscopic device, a mercury switch device, among other devices. 
     In accordance with an aspect of the present invention, a satellite receiver is configured to be portable for use within a vehicle, as well as for stationary use. The receiver is provided with a vehicle antenna which can be affixed to a vehicle window, for example. The receiver is also provided with a separate antenna for use when the receiver is stationary. An operating mode determining device can be implemented using a mechanical magnetic, electromagnetic, semiconductor, electronic or other type of switch or detector which is actuated when the stationary antenna is deployed and/or when vehicle antenna is connected to a vehicle antenna port on the receiver. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various aspects, advantages and novel features of the present invention will be more readily comprehended from the following detailed description when read in conjunction with the appended drawings, in which: 
     FIG. 1 illustrates a satellite broadcast system; 
     FIG. 2 illustrates a receiver unit constructed in accordance with an embodiment of the present invention; 
     FIG. 3 illustrates an exemplary installation of the receiver unit depicted in FIG. 2 in a vehicle; 
     FIG. 4 is a block diagram of a two-arm satellite broadcast receiver for use with the satellite broadcast system depicted in FIG. 1 in accordance with an embodiment of the present invention; 
     FIG. 5 is a block diagram of a three-arm satellite broadcast receiver for use with the satellite broadcast system depicted in FIG. 1 in accordance with an embodiment of the present invention; 
     FIG. 6 is a schematic diagram of an operating mode detection device in accordance with an embodiment of the present invention; 
     FIG. 7 is a schematic diagram of an operating mode detection device in accordance with an embodiment of the present invention; and 
     FIG. 8 illustrates an operating mode detection device in accordance with an embodiment of the present invention. 
     Throughout the drawing figures, like reference numerals will be understood to refer to like parts and components. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 depicts a satellite broadcast system  10  which comprises at least one geostationary satellite  12  for line of sight (LOS) satellite signal reception at receiver units indicated generally at  14 . The satellite broadcast system  10  can be used for SDARS, for example. Another geostationary satellite  16  at a different orbital position is provided for diversity purposes. One or more terrestrial repeaters  17  can be provided to repeat satellite signals from one of the satellites in geographic areas where LOS reception is obscured by tall buildings, hills and other obstructions. 
     A receiver unit  14  can be configured for stationary use (e.g., on a subscriber&#39;s premises), or for mobile use, or both. With reference to FIG. 2, a receiver unit  14  constructed in accordance with the present invention comprises at least one satellite antenna  18  for receiving signals from at least one of the satellites  12  and  16 . The antenna  18  is, for example, a satellite S-band antenna operable at about 2.3 gigaHertz (GHz) for receiving satellite broadcast signals. As will be described below in connection with FIG. 4, the satellite antenna  18  is sufficiently broadband to receive first and second satellite channels from the satellites  12  and  16 , respectively, on different frequencies. The antenna  18  is preferably detachable and is useful for operating the receiver unit  14  in a stationary environment and is directed and pointed for LOS signal reception with a satellite  12  or  16 . 
     The antenna  18  is preferably connected to a chassis  20  containing other components of the receiver unit  14 . With continued reference to FIG. 2, the chassis  20  is configured for detachable connection to a mobile antenna  26 , that is, an antenna that can be mounted on a vehicle for mobile use. The antenna  26  and its associated circuitry (e.g., a low noise amplifier) can be connected internally or externally with respect to a vehicle. As shown in FIG. 3, the antenna  26  can be mounted on the roof  27  or rear window  28  of a vehicle  29 , for example. A cable  30  connects the antenna  26  to the chassis  20 . To avoid having to drill a hole in the truck or car  29  to install the cable  30 , a device  31  can be mounted on the exterior of the vehicle&#39;s rear window  28  using an adhesive material. The device  31  supports the antenna  26  and contains any associated circuitry. The device  31  can be capacitively coupled with another device  32  which is connected to the cable  30 . The other device  32  can be mounted on the inside of the window  28  opposite the first device  31  using the same adhesive material. Alternatively, the antenna  26  can be clipped onto a vehicle window as described in the co-pending U.S. patent application Ser. No. 09/317,947, filed May 25, 1999. 
     As shown in FIG. 2, the receiver unit  14  can be provided with one or more loudspeakers, indicated generally at  34 , which are either detachable or integral with respect to the chassis  20 . The loudspeakers are preferably detachable to allow the receiver unit  14  to be more portable and adaptable for use in a vehicle. When used in a vehicle, the receiver unit can playback received satellite broadcast programs via the AM/FM tuner  36 , antenna  40  and vehicle loudspeakers  38  as described in the above-referenced co-pending U.S. patent application Ser. No. 09/263,207, filed Mar. 5, 1999, and in the above-referenced co-pending U.S. patent application Ser. No. 09/310,352, filed May 12, 1999, both of which are incorporated herein by reference for all purposes. Other methods of playing satellite broadcast programs via a standard audio system installed in a vehicle can be used. Depending on the method chosen, the received satellite broadcast program can be provided to the vehicle tuner  36  and loudspeaker  34  via a wireless or wireline link. An exemplary wireless link can be implemented by modulating the broadcast program on an open AM or FM frequency channel in the operating range of the tuner  36 . An exemplary wireline link can be implemented by sending broadcast program signals on a DC power link, which also provides power from the vehicle DC power supply. The components in the receiver unit  14  for processing the received satellite broadcast signal for playback on the existing audio system of a vehicle are indicated in FIG. 2 at  42 . These components and the exemplary links are described in the afore-mentioned co-pending applications. 
     As shown in FIG. 2, the receiver unit  14  is provided with a microcontroller  44 , a display  46  and a user input device  48  such as a number of buttons and dials. The user input device  48  can comprise satellite broadcast channel selection buttons, as well as volume control and tuning buttons or dials. The microcontroller  44  can receive data from a satellite receiver  50  connected to the antenna  18  or  26 . The data is received via an input line  52  and provides information relating to SDARS, which can include, for example, satellite broadcast channel number, artist name, audio program title and data channel information. The microcontroller  44  can also indicate via the display  46  the signal strength (i.e., RSSI) of satellite or terrestrially repeated SDARS signals, and visual effects (e.g., a dynamic bar graph display corresponding to the output levels of the audio program from the auxiliary audio source), among other displayable information. 
     The receiver unit  14  is configured for stationary use by pointing the antenna  18  to the satellite  12  or  16  which provides the best LOS reception and therefore the best satellite signal. The microcontroller  44  can be programmed to determine the strength of both of the satellite signals via the RSSI data received via the line  52  from the satellite receiver  50  and to select the strongest one of the satellite channels (i.e., receiver arms  54  and  56 ) for reception when operating in the stationary mode. The receiver unit  14  does not change satellite channels until it is powered down and then powered up again, in which case the operating mode remains unchanged from the previous mode before the receiver unit  14  was powered down. A reset button  98  can be provided which, when depressed, causes the microcontroller  44  to commence determining the strongest of the two satellite signals to lock onto. The microcontroller  44  can also be programmed to automatically default to one of the receiver arms  54  and  56  without reference to signal quality when in the stationary mode. A toggle button  55  can be provided to toggle between the two receiver arms  54  and  56  to allow a user to switch to the other receiver arm when sound quality deteriorates using the active receiver arm. 
     In the mobile operating mode, the receiver unit  14  is operable to dynamically select either one of satellite signals for output, or to combine the two satellite signals. Since terrestrial signals are typically stronger than received satellite signals, output signals from the receiver unit  14  can be generated using only the terrestrial signal in either the stationary or the mobile operating mode if terrestrial repeaters  17  are employed in the satellite broadcast system  10 . 
     As described below in connection with FIGS. 4 and 5, the satellite receiver  50  comprises at least two receiver arms  54  and  56 . In accordance with two embodiments of the present invention described below with reference to FIGS. 6 and 7, respectively, the satellite receiver  50  can be configured with one of two different and exemplary power detection devices for energizing a relay to selectively disable one of the receiver arms. Additional embodiments of the present invention are then described with further reference to FIG. 2 whereby the microcontroller  44  is programmable to receive input signals from one or more operating mode detection devices. The microcontroller  44  is operable in response to these input signals to generate control signals, as indicated at line  53 , for transmission to the satellite receiver  50 . The control signals are operable to disable a receiver arm  54  or  56  in the satellite receiver  50  using a corresponding switching device  58  and  60 , as will now be described in connection with FIG.  4 . For example, one of the arms  54  and  56  can be disabled when the receiver unit  14  is operating in a stationary environment. 
     As shown in FIG. 4, the receiver arms  54  and  56  each receive a signal from a splitter  62 , following signal reception by the antenna  18  or  26  and amplification by a low noise amplifier (LNA)  64 . The receiver arm  54  comprises a downconverter  66  and an analog-to-digital converter (ADC)  68 . A demodulation device  70  is provided which can have a demultiplexing function for processing time division multiplexed (TDM) broadcast signals. Similarly, the receiver arm  56  comprises a downconverter  78 , an ADC  80  and a demodulation device  82 . The data streams from the two arms  54  and  56  are combined via a satellite-satellite combiner  74 . The output of the combiner  74  is processed by a forward error correction (FEC) decoder  76  and an audio or service layer decoder  78 . 
     FIG. 5 depicts an exemplary satellite receiver  50  having three receiver arms, that is, receiver arms  54  and  56  and a receiver arm  84  for processing signals received via a terrestrial repeater  17 . The arm  84  receives signals from a received satellite broadcast via the splitter  62 . A downconverter  86  and an ADC  88  and a demodulation device  90  are provided which operate in substantially the same manner as those described above in connection with the satellite receiver arms  54  and  56 . The demodulation device  90 , however, can employ a different demodulation method if the modulation method used at the terrestrial repeater  17  differs from that used for the satellite broadcast signals. The demodulated stream is processed by an FEC decoder  92 . The outputs of the FEC decoder  92  and the FEC decoder  76  are combined via the terrestrial-satellite combiner  96  prior to being decoded by the audio or service layer decoder  77 . 
     The embodiments of the present invention exemplified by FIGS. 6 and 7, respectively, operate with receiver components which are implemented as an integrated circuit (IC) hereinafter referred to as a channel decoder IC  100 . For exemplary purposes, the IC  100  is illustrated as having three receiver arms  54 ,  56  and  84 , as described above with reference to FIG.  5 . The IC  100  preferably comprises the corresponding downconverters  66 ,  78  and  86 , and the ADCs  68 ,  80  and  88  for each receiver arm  54 ,  56  and  84 , as indicated by the RF front end devices  102  and  104  for satellite and terrestrial signal processing, respectively. The IC  100  also comprises the demodulators  70 ,  82  and  90  for each receiver arm and the baseband processing devices, as indicated at  106  (e.g., the combiners  74  and  96 , the FEC decoders  76  and  92 , and the service layer decoder  77 ). 
     As shown in FIG. 6, receptacles  108  and  110  are provided on the receiver unit  14 . The receptacle  108  is connected to the coil of a relay  112 , the contacts of which are normally open or in the OFF position. When the contacts are closed, a voltage is applied to the outputs from the relay  112  which are connected to respective ones of the demodulators  70  and  82 . When an automotive power source (e.g., a car battery) is connected to the receptacle  108 , the relay is actuated and enables both of the demodulators  70  and  82 . When a house or consumer battery (e.g., 9 volts or less) input is connected to the receptacle  110 , the relay is not actuated and the contacts remain in the OFF position. A selector switch  114  is provided which allows a user to selectively enable only one of the demodulators  70  or  82  and therefore only one of the receiver arms  54  or  56  for satellite signals. 
     With reference to FIG. 7, another embodiment of the present invention is depicted which comprises the IC  100 , the relay  112  and the selector switch  114  described above with reference to FIG. 6; however, only one receptacle  120  is provided in lieu of two independent receptacles  108  and  110  for the supply of automotive or household/battery power to the receiver unit  14 . The receptacle  120  can be configured to have a number of different types of plugs or sockets to accommodate connections to different types of power sources. A single output, however, is connected to a comparator  122 . In the illustrated example, V+ is assumed to be 5 volts. An automotive power source such as a car battery is typically 12 volts or more, and household power or consumer battery sources are typically 9 volts. 
     With continued reference to FIG. 7, the comparator  122  is selected to trigger (e.g., go high) when the voltage on its positive input terminal (V+) is greater than the voltage on the negative terminal thereof. If resistors R 1  and R 2  are both 10 kilo-ohms (k ), then V REF  is one-half the power source input voltage V IN . Thus, when the input voltage V IN  exceeds 10 volts, as for automotive battery power, the V REF  value becomes more positive than the V+ value. The output signal from the comparator  122 , that is, the mobile mode enabled signal, is true (e.g., goes high) and therefore energizes the relay  112  to enable the demodulators  70  and  82  in both of the receiver arms  54  and  56 . The receiver unit  14  is therefore operable in the mobile use mode when connected to an automotive power source. When the input voltage V IN  is less than 10 volts, as in the stationary mode, the V REF  value becomes less than V+ on the comparator  122 . Accordingly, the mobile mode enabled signal is false (e.g., remains low). Only one of the demodulators  70  and  82  can therefore be enabled using the selector switch  114 . 
     It is to be understood that the receiver unit  14  can be implemented differently than with an IC  100  and that receiver arm disabling devices be configured for use in different places along the processing paths of the receiver arms  54  and  56  or other components of the satellite receiver  50  than at the demodulators, as shown in FIGS. 6 and 7. For example, FIGS. 4 and 5 both depict the exemplary use of switching devices  58  and  60  in the receiver arms  54  and  56 . The switching devices  58  and  60  can be controlled, for example, by the microcontroller  44  to selectively open or close the connection of the corresponding arm  54  and  56  to the output of the splitter  58 . The switching devices can also be independently operated using a relay, comparator, or other type of device. 
     Different operating mode detection devices will now be described for providing input signals to the microcontroller  44  or otherwise independently enabling a selected one or both of the satellite receiver arms  54  and  56  in the satellite receiver  50  in accordance with the present invention. These devices will be described in connection with FIGS. 2 and 8. While several of these devices are illustrated for use with one receiver unit  14  in FIG. 2, it is to be understood that the receiver unit  14  need only be equipped with one such device to operate in accordance with the present invention. 
     In accordance with one method for detecting whether the receiver unit  14  is operating in a stationary or mobile environment, the antenna  18  is removably attached to the chassis  20 . The chassis is provided with an antenna port  130  for receiving the detachable stationary receiver antenna  18 . The antenna port  130  is provided with a sensing device  132  such as a mechanical, magnetic, electromagnetic, semiconductor, electronic or other type of switch or detector to detect when the end of the coaxial cable or other conductor connected to the receiver antenna  18  has been inserted into the port  130 . The sensing device  132  provides an output signal which can be used by the microcontroller  44  or another device (e.g., relay) to disable one of the receiver arms  54  or  56  (e.g., the arm that provides the weakest signal). The antenna  26  is also preferably removably attached to the chassis  20  at a port  134 . The sensing device  132  can be provided at the port  134 , as opposed to the port  130 . Accordingly, the receiver unit  12  can be configured to operate in the stationary mode until the end of the coaxial cable or other conductor connected to the antenna  26  is connected to the port  134 . If desired, sensing devices  132  can be provided at both of the antenna ports  130  and  134 . 
     The chassis  20  is provided with an AC power port  136  and a fixed power cord  138  extending between the AC power port  136  and an AC power outlet  139 . In accordance with another embodiment of the present invention, the power cord  138  is detachable, and a sensing device  140  such as a mechanical, magnetic, electromagnetic, semiconductor, electronic or other type of switch or detector is provided at the port  136 . The microcontroller  44  is programmed, or another device such as a relay is configured, to operate the receiver unit  14  in a stationary mode (i.e., to disable one of the receiver arms  54  and  56 ) when the sensing device  140  detects the presence of the power cord  138  at the port  136 . 
     As shown in FIG. 2, the chassis  20  is also provided with a DC power supply port  142 . The receiver unit  14  of the present invention can be used in conjunction with a DC power supply cord  144  having an adapter  146  at one end therefor which is configured for insertion in the cigarette lighter receptacle or auxiliary power socket  150  provided in most vehicles. Accordingly, the sensing device  140  can be located proximally with the port  142  to determine if a DC power supply is being used and therefore if the receiver unit  14  is operating in a mobile environment. 
     In accordance with another embodiment of the present invention, the chassis  20  is provided with a manual switch button  152  that can be operated by a user to select an operating mode. The button  152  can provide an input signal to the microcontroller  44  to disable one of the receiver arms  54  or  56  when activated (e.g., operating one of the switching devices  58  or  60 ). Alternatively, the button  152  can be used to complete a path between the input of a relay or similar device and a voltage source for actuation. The output of the relay or similar device can then be used as an enabling or disabling signal for one of the satellite receiver arm components. 
     The receiver unit  14  can also be provided with a motion sensing device  154  having an output connected, for example, to the microcontroller  44  to detect when the receiver unit  14  is being used in a mobile environment. The motion sensing device  154  can be an accelerometer, a sensor associated with the tachometer of the vehicle or other transit measuring device. In addition, the motion sensing device can be an encoding compass or heading indicator, an encoding gyroscope, a mercury switch, or a vibration sensor selected to have a sensitivity to distinguish between idle and vehicle motion. 
     In accordance with another aspect of the present invention, the receiver unit  14  is operated in conjunction with a pedestal base  155  that can be installed on the dashboard of a vehicle. The receiver unit  14  can be provided with a proximity sensing device  156  such as a Hall effect device (HED). The base can be provided with a magnet  158  which actuates the HED  156  when the portable receiver is mounted on the base in the vehicle. The microcontroller  44 , for example, can be programmed to operate the receiver unit  14  in a stationary mode (e.g., using only the arm  54  or  56  which provides the strongest satellite signal output) until actuation of the HED. The microcontroller  44  then operates the receiver unit  14  in a mobile operating mode until the microcontroller receives an indication that the receiver unit has returned to stationary use. Alternatively, the pedestal base can be configured to provide a circuit path to complete the connection of the antenna  26  to the receiver unit. The sensor  134  in FIG. 2 can then detect when the antenna  26  is configured to allow use of the receiver unit in a mobile environment using both receiver arms  54  and  56 . 
     As stated previously, the mode sensing device can be implemented as a device that detects differences in voltage and current characteristics of batteries or other power sources used in the receiver unit and in a vehicle electrical system. Alternatively, the receiver unit  14  can be provided with a device to dynamically measure the power level of a received satellite signal. If the signal power level is relatively constant, then the receiver unit  14  is determined by the microcontroller  44  to be operating in a stationary environment. The receiver unit  14  can also be configured to monitor signal strength to determine if a second satellite signal is needed. If the received signal strength drops below a predetermined level, then the non-operating arm  54  or  56  is activated. In addition, an input signal generated by the vehicle playback interface  42  can be provided to the microcontroller  44  to indicate that the receiver unit  14  is operating in a mobile environment. 
     Although the present invention has been described with reference to certain preferred embodiments thereof, it will be understood that the invention is not limited to the details thereof. Various modifications and substitutions have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. All such modifications and substitutions are intended to be embraced within the scope of the invention as defined in the appended claims.