Abstract: A communication satellite system (100) is established using one or more satellite constellations (110, 120). The two or more satellite groups (110, 120) are connected via long range crosslinks (145) which provide a communication path between the long range satellites (150, 170) in the two satellite groups (110, 120). Each satellite group (110, 120) comprises long range satellites (150, 170) and short range satellites (160, 180) which are interconnected using short range crosslinks (155, 175). A single antenna on each satellite provides both crosslinks. The long range crosslink (145) is established using the antenna's main beam and the short range crosslinks (155, 175) are established using the antenna's sidelobes.

Abstract: A geosynchronous satellite system (10) uses crosslinks (30) between geosynchronous satellites (16) which travel along the same ground path (18) or are located within a common orbital slot (32) in order to increase traffic-carrying capacity and decrease signal delays. The geosynchronous satellites (16) can have substantial angles of inclination to provide high quality coverage within a wide range of latitudes (40, 42). In addition, the orbits can be elliptical, resulting in concentrated network capacity in either the northern or southern hemisphere. For co-positioned satellites (171-174), orbit perturbations are introduced in order to eliminate crosslink blockage caused by intervening satellites (172, 173). Methods for deploying and operating the geosynchronous satellite system enable network capacity to be modified (708) and routing (804), crosslinks (1008), and handoffs (908) to be controlled.

Abstract: A method and apparatus for rapidly characterizing a communications channel is used to mitigate the effects of the communications channel as present in a received signal. A satellite (20) transmits a data signal (40) and a pilot signal (50). The data signal (40) and the pilot signal (50) are substantially orthogonally polarized. A user terminal (30) receives the orthogonally polarized data signal (40) and pilot signal (50). The user terminal includes a channel information recovery circuit (250) and a channel effects mitigation circuit (240). The channel information recovery circuit (250) characterizes the communications channel by analyzing the pilot signal (50), and then provides the channel information (260) to the channel effects mitigation circuit (240) which then mitigates the effects of the channel.

Abstract: A method and apparatus for detecting and tracking spread spectrum signals, such as Global Positioning System (GPS) signals, first obtain precision timing and frequency reference information from a relatively high-power, secondary signal, such as that emanating from a satellite of a low-earth orbit (LEO) satellite communications system, and then use such reference information to perform narrow-band detection of the GPS spread spectrum signal. Accordingly, spread spectrum signals are more efficiently detected and tracked, particularly in environments where they are attenuated by obstacles such as buildings or environmental barriers.

Abstract: A communication satellite system (100) is established using one or more satellite constellations (110, 120). The two or more satellite groups (110, 120) are connected via long range crosslinks (145) which provide a communication path between the long range satellites (150, 170) in the two satellite groups (110, 120). Each satellite group (110, 120) comprises long range satellites (150, 170) and short range satellites (160, 180) which are interconnected using short range crosslinks (155, 175). A single antenna on each satellite provides both crosslinks. The long range crosslink (145) is established using the antenna's main beam and the short range crosslinks (155, 175) are established using the antenna's sidelobes.

Abstract: A system facilitates global cellular communication by utilizing a gateway satellite (1000) which communicates with low-earth orbiting satellites (10, 20) via signalling links (1001, 1002). Switching is performed in each of the satellites (10, 20) and switching interconnections as well as voice path communications are switched via the gateway satellite (1000). With switching performed in a gateway satellite (1000), the use of a ground-based gateway network (74) is minimized and, in some cases, eliminated.

Abstract: A laser transmitter (200, 300) includes a femptosecond pulse forming circuit (214, 308) and an ultra high-speed optical switch (218, 304) which enable the transmitter (200, 300) to generate a modulated pulse stream having pulses with widths of under 200 femptoseconds. The transmitted pulse stream is processed by a laser detector (500), including a wideband optical detector (504) and pulse stretching circuit (506), that regenerates information included in the modulated pulse stream.

Abstract: A satellite communications system employs CDMA multiple access technology. Polarizations are associated with each spreading code to enhance separation between simultaneous users in the absence of perfectly orthogonal spreading codes. A satellite transmitter CDMA encodes(210) and carrier modulates(220) a user or block of users, and then assigns a polarization to the user of block of users. A CDMA reference signal also receives a polarization. A ground receiver (30,40) receives the polarized CDMA signals as transmitted by the satellite. The ground receiver ascertains the polarization of the reference signal and then computes the polarization of the desired polarized CDMA signal. The use of the reference signal negates the effects of the faraday rotation caused by the satellite signal(10,20) passing through the ionosphere.

Abstract: A method and apparatus for routing signals through a system (10) which has multiple destination nodes (12, 14) assigns one or more unique carrier frequencies to each destination node (12, 14). When a signal is received (502) by a transceiver (12), the transceiver (12) evaluates (504) the carrier frequency of the signal, and determines (506) to which destination node (12, 14) that carrier frequency is assigned. The determination (506) is made using a table (200) which associates carrier frequencies to destination nodes (12, 14). The table (200) is created (304) and updated by a control facility (20) which distributes (306) the table (200) to the transceivers (12). Once the transceiver (12) determines (506) the destination node (12, 14), the transceiver (12) can route the signal toward that destination node (12, 14).

Abstract: A constellation (12) of satellites (14) distributed around the earth supports satellite-based communication system (10) involved in global communication of subscriber units (24). Subscriber units (24) may potentially transmit from any location on earth. Some locations such as radio astronomy sites (28) may be interfered with by nearby transmissions from subscriber units (24) or transmissions from satellites (14). Subscriber units (24) located within a potentially interfering proximity to radio astronomy sites are prohibited from transmitting potentially interfering signals by reception of a non-interfering control signal transmitted by a radio astronomy special equipment located at radio astronomy sites. A radio astronomy special equipment (44) repeatedly transmits to a subscriber unit (24) a control signal synchronous with a control signal of a servicing satellite. The radio astronomy special equipment control signal (46), (48), and (54) is compatible with a subscriber unit's communication receiver.