Apparatus and method for facilitating terrestrial transmissions at frequencies also used for satellite transmissions to a common geographic area

• US 6,208,834 B1
• Filed: 12/31/1997
• Issued: 03/27/2001
• Est. Priority Date: 10/11/1996
• Status: Expired due to Term

• Current Assignee: Broadband Investments Limited
• Original Assignee: Northpoint Technology Limited
• Inventors: Tawil, Saleem, Tawil, Carmen
• Primary Examiner(s): VO, NGUYEN THANH
• Application Number:
  US09/001,766
• Time in Patent Office: 1,182 Days
• Field of Search: 455/3.2, 455/13.3, 455/427, 455/430, 455/12.1, 455/63, 455/272, 455/188.1, 455/179.1, 455/562, 348/6, 348/12, 348/13, 343/879, 343/893, 343/878, 343/840
• US Class Current: 455/3.02
• CPC Class Codes: H04B 7/18523 Satellite systems for providing broadcast service to terrestrial stations, i.e. broadcast satellite service arrangements specially adapted for satellite broadcast receiving H04H40/90; picture transmission via satellite H04N1/00103; television transmission via satellite H04N7/20
• CPC Class Codes: H04B 7/18563 Arrangements for interconnecting multiple systems data switching networks H04L12/00
• CPC Class Codes: H04H 40/90 specially adapted for satellite broadcast receiving
• CPC Class Codes: H04N 7/20 Adaptations for transmission via a GHz frequency band, e.g. via satellite
• CPC Class Codes: H04W 4/06 Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
• CPC Class Codes: H04W 84/06 Airborne or Satellite Networks space-based or airborne stations H04B7/185

Abstract

A satellite receiving antenna (16) at a user location (14) receives satellite signals at a first frequency from a satellite (12). The satellite signals travel along a satellite signal route (42) within a look angle about the centerline (28) of the antenna (16). A terrestrial transmitter (20) transmits signals at the first frequency along a wireless transmission route (40) from the transmitter to the user location (14). The terrestrial transmitter (20) is located with respect to the user location (14) so that the wireless transmission route (40) is at a relatively large angle to the centerline (28) of the first antenna (16). The angle of the wireless transmission route (40) to the satellite antenna centerline (28) is large enough so that the terrestrial signals present at the location (14) result in terrestrial input signals from the antenna (16) which are less than an interference level with respect to satellite input signals produced by the antenna. Thus, the terrestrial signals do not interfere with the satellite signals even though they are transmitted at a common frequency.

Claims

1. A method for reusing a first transmission frequency already in use for transmitting satellite signals from a satellite along a satellite signal route to a first location for reception at a satellite receiving antenna which may be at the first location, the satellite receiving antenna producing a maximum gain for signals received along a satellite receiving antenna centerline and less gain at angles from said centerline, the satellite signals having a signal power level at the first location such that, when the satellite receiving antenna is placed in a satellite reception position in which the satellite transmission route lies within a satellite reception look angle about the satellite receiving antenna centerline, the satellite signals produce satellite input signals from the satellite receiving antenna which are at least at a minimum usable satellite input signal level, the method comprising the steps of:

(a) substantially continuously detecting the satellite signal power level at a location near a first terrestrial transmitter;

(b) setting the transmission power of the first terrestrial transmitter to a non-interfering level based upon the satellite signal power level detected near the first terrestrial transmitter, the non-interfering level being a level ensuring that substantially each location within an effective transmission area around the first terrestrial transmitter receives terrestrial signals from the first terrestrial transmitter at a power level to produce non-interfering terrestrial input signals from a satellite receiving antenna aligned to receive satellite signals at said location, the non-interfering terrestrial input signals being at a power level less than an interference level with respect to the satellite input signals produced by the satellite receiving antenna at said location; and

(c) transmitting terrestrial signals at the first transmission frequency from the first terrestrial transmitter, the terrestrial signals being transmitted in directions including a wireless transmission route from the first terrestrial transmitter to the first location, and the wireless transmission route lying at an angle from the satellite receiving antenna centerline, when the satellite receiving antenna is in the satellite reception position, such that the terrestrial signals present at the first location result in terrestrial input signals from the satellite receiving antenna which are at a power level less than the interference power level with respect to the satellite input signals, the terrestrial signals present at the first location having a power level at least at a minimum usable terrestrial signal level.

2. The method of claim 1 wherein the step of detecting the satellite signal power level includes the steps of:

(a) receiving the signals transmitted from the satellite at the first transmission frequency; and

(b) converting the signals transmitted from the satellite at the first transmission frequency to a representative signal which is representative of the satellite signal power level.

3. The method of claim 2 wherein the step of setting the transmission power level for the first terrestrial transmitter includes the step of:

(a) comparing the representative signal to a reference signal to produce a comparison output.

4. The method of claim 3 further including the step of:

(a) using the comparison output to control the transmission power level for the first terrestrial transmitter.

5. The method of claim 4 wherein the step of using the comparison output to control the transmission power level for the first terrestrial transmitter includes the step of:

(a) controlling a modulated signal level in the first terrestrial transmitter.

6. An apparatus for simultaneously providing terrestrially transmitted signals on a common frequency with satellite signals transmitted from a satellite along a satellite signal route to a first location, the satellite signals being transmitted at a first frequency for reception at a satellite receiving antenna which may be at the first location, the satellite receiving antenna producing a maximum gain for signals received along a satellite receiving antenna centerline and less gain at angles to said centerline, the satellite signals having a signal power level such that, when the satellite receiving antenna is placed in a satellite reception position in which the satellite transmission route lies within a satellite reception look angle about the satellite receiving antenna centerline, the satellite signals result in satellite input signals from the satellite receiving antenna which are at least at a minimum usable satellite input signal level, the apparatus comprising:

(a) a first terrestrial transmitter for transmitting signals at the first frequency along a wireless transmission route from a first terrestrial transmitter location to the first location, the wireless transmission route lying at an angle from the satellite receiving antenna centerline, when the satellite receiving antenna is in the satellite reception position, such that the terrestrial signals present at the first location result in terrestrial input signals from the satellite receiving antenna which are at a power level less than an interference level with respect to the satellite input signals, the terrestrial signals present at the first location having a power level at least at a minimum usable terrestrial signal level;

(b) satellite signal power monitoring means for substantially continuously detecting the satellite signal power level at a location near the first terrestrial transmitter; and

(c) transmission power adjusting means associated with the first terrestrial transmitter for setting the transmission power of the first terrestrial transmitter to a non-interfering level based upon the satellite signal power level detected by the satellite signal power monitoring means, the non-interfering level being a level ensuring that substantially each location within an effective transmission area around the first terrestrial transmitter receives terrestrial signals from the first terrestrial transmitter at a power level to produce non-interfering terrestrial input signals from a satellite receiving antenna aligned to receive satellite signals at said location, the non-interfering terrestrial input signals being at a power level less than the interference level with respect to the satellite input signals produced by the satellite receiving antenna at said location.

7. The apparatus of claim 6 wherein the satellite signal power monitoring means includes:

(a) a satellite signal receiving antenna aligned to receive signals transmitted from the satellite at the first transmission frequency; and

(b) a detector amplifier operatively connected to convert the signals received by the satellite signal receiving antenna to a representative signal which is representative of the satellite signal power level.

8. The apparatus of claim 7 wherein the satellite signal power monitoring means further includes:

(a) a comparator operatively connected to compare the representative signal to a reference signal to produce a comparison output.

9. The apparatus of claim 8 wherein the transmission power adjusting means includes a level control device operatively connected to the first terrestrial transmitter and wherein the comparator is connected to apply the comparison output to the level control device.

10. The apparatus of claim 9 wherein the level control device is operatively connected to an output of a modulator associated with the first terrestrial transmitter, the level control device for controlling a modulated signal level in the first terrestrial transmitter.

11. An apparatus for simultaneously providing terrestrially transmitted signals on a common frequency with satellite signals transmitted from a satellite, the satellite signals being transmitted at a first frequency along a satellite transmission route to a satellite receiving antenna at a location which may be anywhere within a geographic service area, the satellite receiving antenna producing a maximum gain for signals received along a satellite receiving antenna centerline and less gain at angles from said centerline, the satellite signals having a signal power level which, when the satellite receiving antenna is placed at a satellite reception position in which the satellite transmission route lies within a satellite reception look angle about the satellite receiving antenna centerline, results in satellite input signals from the satellite receiving antenna, the satellite input signals being at least at a minimum usable satellite input signal level, the apparatus comprising:

(a) a plurality of spaced apart terrestrial transmitters, each terrestrial transmitter transmitting terrestrial signals at the first frequency, the plurality of spaced apart terrestrial transmitters being arranged such that substantially each respective location within the geographic service area has a wireless transmission route to one of the terrestrial transmitters, the wireless transmission route lying at an angle from the satellite receiving antenna centerline when the satellite receiving antenna is in the satellite reception position at the respective location such that the terrestrial signals present at the respective location are at least at a minimum usable terrestrial signal level but result in terrestrial input signals from the satellite receiving antenna which are at a power level less than an interference level with respect to the satellite input signals;

(b) satellite signal power monitoring means for substantially continuously detecting the satellite signal power level at a monitoring location within the geographic service area; and

(c) transmission power adjusting means associated with the terrestrial transmitters for setting the transmission power of the terrestrial transmitters to a non-interfering level based upon the satellite signal power level detected by the satellite signal power monitoring means, the non-interfering level being a level ensuring that substantially each location within the geographic service area receives terrestrial signals from each of the terrestrial transmitters at a power level to result in non-interfering terrestrial input signals from a satellite receiving antenna aligned to receive satellite signals at said location, the noninterfering terrestrial input signals being at a power level less than the interference level with respect to the satellite input signals produced by the satellite receiving antenna at said location.

12. The apparatus of claim 11 wherein the satellite signal power monitoring means includes:

(a) a satellite signal receiving antenna aligned to receive signals transmitted from the satellite at the first transmission frequency; and

(b) a detector amplifier operatively connected to convert the signals received by the satellite signal receiving antenna to a representative signal which is representative of the satellite signal power level.

13. The apparatus of claim 12 wherein the satellite signal power monitoring means further includes:

(a) a comparator operatively connected to compare the representative signal to a reference signal to produce a comparison output.

14. The apparatus of claim 13 wherein the transmission power adjusting means includes a level control device operatively connected to the first terrestrial transmitter and wherein the comparator is connected to apply the comparison output to the level control device.

15. The apparatus of claim 14 wherein the level control device is operatively connected to an output of a modulator associated with the first terrestrial transmitter, the level control device for controlling a modulated signal level in the first terrestrial transmitter.

16. A method for reusing a first transmission frequency already in use for transmitting satellite signals from a satellite along a satellite signal route to a first location for reception at a satellite receiving antenna which may be at the first location, the satellite receiving antenna producing a maximum gain for signals received along a satellite receiving antenna centerline and less gain at angles from said centerline, the satellite signals having a signal power level at the first location such that, when the satellite receiving antenna is placed in a satellite reception position in which the satellite transmission route lies within a satellite reception look angle about the satellite receiving antenna centerline, the satellite signals produce satellite input signals from the satellite receiving antenna which are at least at a minimum usable satellite input signal level, the method comprising the steps of:

(a) determining the satellite signal power level;

(b) setting the transmission power of a first terrestrial transmitter to a non-interfering level based upon the determined satellite signal power level, the non-interfering level being a level ensuring that substantially each location within an effective transmission area around the first terrestrial transmitter receives terrestrial signals from the first terrestrial transmitter at a power level to produce non-interfering terrestrial input signals from a satellite receiving antenna aligned to receive the satellite signals at said location, the non-interfering terrestrial input signals being at a power level less than an interference level with respect to the satellite input signals produced by the satellite receiving antenna at said location; and

(c) transmitting terrestrial signals at the non-interfering power level and first transmission frequency from the first terrestrial transmitter to the effective transmission area.

17. The method of claim 16 wherein the step of determining the satellite signal power level includes the steps of:

(a) receiving the signal transmitted from the satellite at the first transmission frequency; and

(b) converting the signal transmitted from the satellite at the first transmission frequency to a representative signal which is representative of the satellite signal power level.

18. The method of claim 17 wherein the step of setting the transmission power level for the first terrestrial transmitter includes the step of:

(a) comparing the representative signal to a reference signal to produce a comparison output.

19. The method of claim 18 further including the step of:

(a) using the comparison output to control the transmission power level for the first terrestrial transmitter.

20. The method of claim 19 wherein the step of using the comparison output to control the transmission power level for the first terrestrial transmitter includes the step of:

(a) controlling a modulated signal level in the first terrestrial transmitter.