Receiver adjacent channel overload projection

A filter system that filters WCS signals received by a satellite radio antenna if the WCS signals have a high enough signal strength where they could overwhelm the satellite radio signals and prevent the satellite radio from operating. The filter system includes a coupling circuit that couples off a small portion of the signal received by the antenna and sends it to a detector that detects the signal strength of the coupled off portion of the signal. If the signal strength exceeds a predetermined threshold, the detector provides a control signal to a switch that directs the signal received by the antenna to a WCS filter to filter out the WCS signals, where the switch otherwise causes the signal received by the antenna to be sent directly to the radio.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates generally to a system and method for filtering signals in a frequency band adjacent to a frequency band being employed for radio reception and, more particularly, to a system and method for filtering wireless communications service (WCS) signals broadcast in a frequency band that is adjacent to a satellite radio frequency band being received by a vehicle satellite radio.

Discussion of the Related Art

Mobile wireless cellular devices are everywhere. Cellular devices allow for the wireless transmission and reception of video, audio and data, and are relied on by users for many purposes. Those purposes and the technology, such as 4G long term evolution (LTE), to provide the services are increasing, which requires an increasing need for more wireless bandwidth and data throughput. With the explosion in demand for cellular data and voice services, there is an increasing burden on the existing frequency bands allocated for these services, where the available cellular bandwidth is becoming insufficient to meet those demands. Providing additional frequency bands for cellular services has a direct and often times measurable impact on commercial progress.

The Federal Communications Commission (FCC) regulates which frequency bands are used for what purposes in the United States. Thus, there has been significant pressure on the FCC to allocate more frequency bands for cellular services, which also provides significant revenue. In response, the FCC has recently reallocated the WCS frequency band for cellular services, where the 2305-2320 MHz frequency band is now being used for signals transmitted from mobile cellular devices to a cellular tower and the 2345-2360 MHz frequency band is now being used for signals transmitted from the cellular tower to the mobile devices.

Satellite radio, specifically Sirius and XM, have also been allocated a certain frequency band by the FCC, where Sirius satellite radio operates in the 2320-2332.50 MHz frequency band and XM satellite radio operates in the 2332.50-2345 MHz frequency band. As is apparent, the XM frequency band is contiguous and adjacent to the WCS frequency band used for signals transmitted by the cellular tower and the Sirius frequency band is contiguous and adjacent to the WCS frequency band used for signals transmitted by the mobile devices.

Satellite radios receive signals from satellites from which certain audio can be played. Those signals are at relatively low power when received by the radio. Cellular towers broadcast cellular signals to the mobile wireless devices within a certain range of the tower. Those signals are broadcast at a relatively high power from the tower to be received by the mobile devices some distance away at the appropriate data rate throughput. If a vehicle having a satellite radio is travelling within a certain proximity to a cellular tower that is broadcasting cellular signals in the WCS frequency band, those signals are received by the satellite radio antenna on the vehicle at a relatively high power, for example, possibly five magnitudes larger than the satellite radio signals being received by the antenna. For XM satellite radio signals that may be directly adjacent to the WCS signals from the cellular tower, the WCS frequency signals can overwhelm and block the satellite radio signals, where the satellite radio on the vehicle may go mute.

Also, if a vehicle having a satellite radio is travelling within a certain proximity of a mobile cellular device that is transmitting cellular signals in the WCS frequency band, where the cellular device may be in the vehicle, those signals are received by the satellite radio antenna on the vehicle and possibly at a higher power level than the satellite radio signals. For Sirius satellite radio signals that may be directly adjacent to the WCS signals from the cellular device, the WCS frequency signals can overwhelm and block the satellite radio signals, where the satellite radio on the vehicle may go mute.

SUMMARY OF THE INVENTION

The present invention discloses and describes a filter system that filters WCS signals received by a satellite radio antenna if the WCS signals have a high enough signal strength where they could overwhelm the satellite radio signals and prevent the satellite radio from operating. The filter system includes a coupling circuit that couples off a small portion of the signal received by the antenna and sends it to a detector that detects the signal strength of the coupled off portion of the signal. If the signal strength exceeds a predetermined threshold, the detector provides a control signal to a switch that directs the signal received by the antenna to a WCS filter to filter out the WCS signals, where the switch otherwise causes the signal received by the antenna to be sent directly to the radio.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following discussion of the embodiments of the invention directed to a WCS filter system for filtering WCS signals in a satellite radio is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses. For example, as discussed herein, the satellite radio is on a vehicle. However, as will be appreciated by those skilled in the art, the satellite radio may be on other mobile platforms or otherwise.

FIG. 1is an illustration10showing a vehicle12having a satellite radio14, such as an XM satellite radio or a Sirius satellite radio, that receives satellite radio signals from a satellite16. The vehicle12may be traveling near a cellular tower18that may be broadcasting cellular signals in the WCS frequency band that may be adjacent to the frequency band of the signals broadcast by the satellite16. For example, the radio14may be an XM radio, the satellite16may be broadcasting XM signals in the 2332.50-2345 MHz frequency band, and the cellular tower18may be broadcasting WCS signals in the 2345-2360 MHz frequency band. As discussed above, the power of the signals from the cellular tower18may be high enough and close enough in frequency to the signals transmitted by the satellite16that the satellite radio signals are overwhelmed in the radio14and it goes mute. The vehicle12may also be traveling near a mobile cellular device28that may be transmitting cellular signals in the WCS frequency band that also may be adjacent to the frequency band of the signals broadcast by the satellite16, where the device28may be inside the vehicle12. For example, the radio14may be a Sirius radio, the satellite16may be broadcasting Sirius signals in the 2320-2332.50 MHz frequency band, and the cellular device28may be transmitting WCS signals in the 2305-2320 MHz frequency band. As discussed above, the power of the signals from the cellular device28may be high enough and close enough in frequency to the signals transmitted by the satellite16that the satellite radio signals are overwhelmed in the radio14and it goes mute.

FIG. 2is a block diagram of a satellite radio system20that includes a satellite radio22that receives satellite radio signals from, for example, the satellite16by an antenna24. As is known in the art, satellite radio antennas, as well as other antennas on a vehicle, are coupled to the particular receiver/transmitter by coaxial cables, where those cables may be coupled together in sections by in-line connectors, such as FAKRA connectors, so that the vehicle can be manufactured in parts, and then assembled together by connecting the connectors. The present invention proposes inserting a WCS filter system26between the antenna24and the radio22, where the system26includes, for example, a low-pass WCS filter30that filters out signals from the tower18received by the antenna24before they are able to be received by the radio22. In other embodiment, the filter may be a band-pass, notch or high-pass filter consistent with the discussion herein.

In this design, an in-line coaxial connector32that may have previously been coupled to an in-line coaxial connector34to connect the antenna24to the radio22may be disconnected, and the filter system26is connected between the antenna24and the radio22by connecting a coaxial connector36to the connector32and a coaxial connector38to the connector34as shown, where the filter system26may be mounted to any suitable location on the vehicle12. The WCS filter30is designed to block or reject signals above the XM frequency band so as to prevent the cellular signals transmitted by the tower18from being received by the radio22. In an alternate embodiment, the filter30may be a high-pass filter that is designed to block WCS signals in the 2305-2320 MHz frequency band so that they do not interfere with satellite radio signals for a Sirius satellite radio. The filter30can be any suitable low-pass, high-pass, band-pass, notch filter for the applications discussed herein, such as filter commercially available from Quorvo™ having part number QPQ1900Q. It is noted that because the XM or Sirius frequency band and the WCS frequency band being discussed herein are adjacent, the filter30needs to have a narrow transition frequency band to pass the desired signals and reject the undesired signals. The WCS filter30may be implemented on a printed circuit board wherein the filter response one of a lowpass filter, a highpass filter, a notch filter, or a bandpass filter. By using a notch filter configuration centered at the WCS frequency may provide adequate attenuation for acceptable attenuation. The filter may be implemented using Film Bulk Acoustic Resonator (FBAR) filter technology or a Surface Acoustic Wave (SAW) filter.

In the system20, the WCS filter30attenuates the satellite radio signals to some degree depending on how close there are in frequency to the WCS frequency band. Therefore, if the satellite radio signal is relatively weak, which may be caused by tree foliage, building, etc., the performance of the radio22may be reduced even in the absence of signals from the cellular tower18or the cellular device28. In other words, in order for the filter30to be acceptable for rejecting the WCS signals, some of the satellite radio signals may be attenuated because of their frequency proximity to the WCS frequency band. Therefore, the present invention proposes to only switch in the WCS filter30in the presence of the WCS signals from the cellular tower18.

FIG. 3is a block diagram of a WCS filter system40that can replace the filter system26, where the connectors32,34,36and38and the radio22are not shown. In this design, a small portion of the signal received by the antenna24is coupled off by a coupling circuit42and is sent to a detector44. The detector44detects the signal strength of the coupled off portion of the receive signal, and if it is greater than some predetermined threshold, indicating the presence of the WCS signal, the detector44sends a control signal that controls a switch46to direct the main part of the receive signal to the WCS filter30. The control signal from the detector44also causes a switch48to direct the signal output from the WCS filter30to the radio22. If the detector44does not detect the high signal power, then the switch46remains in the position where the main part of the signal from the antenna24is directed to line50to by-pass the WCS filter30, where the switch48is in the position to direct that signal to the radio22. Thus, the WCS signals are prevented from muting the radio22.

Some of the elements in the system40may be active elements, which require a power source beyond the power that may be available to provide power to the antenna24. For example, the detector44, the switches46and48, and possibly elements in the filter30may have active elements requiring power. Further, active elements may also be employed to amplify the satellite radio signal. To this end, the system40may include its own power supply52, such as a rechargeable battery, or may have an external connection to a power source (not shown).

In an alternate embodiment, shown inFIG. 4as WCS filter system60, where like elements are identified by the same reference number, the switch48can be replaced with an RF combiner62. In this design, if the main part of the antenna signal is coming through the WCS filter30, where no signal would be present on the line50, then the combiner62combines that signal with the no signal on the line50to provide the output to the radio22. Likewise, if the switch46switches the main part of the antenna signal onto the line50, where no signal is going through the WCS filter30, then the combiner62outputs the unfiltered signal.