Abstract: In a satellite ranging system predetermined bit sequence or group of bit sequence in a transport stream, which is a digital signal are used to generate trigger signals on the basis of which the delay introduced into the transport stream by the travel path from a satellite ground station to the satellite and back or to another satellite ground station is determined allowing a calculation of the distance between the ground station(s) and the satellite. The predetermined bit sequence or group of bit sequences may be inserted into the transport stream at the uplink site, for example as a specific payload P. In order to avoid insertion of additional packets the transport stream or part of it may be used as a predetermined bit sequence.

Abstract: The invention refers to an apparatus for generating a reference frequency depending on a timing information extracted from a data stream. In order to generate a carrier frequency in a user station of a satellite TDMA network at low costs which is accurate and stable and which meets stringent phase noise requirements, it is suggested to use at least one free-running oscillator. The frequency deviation with regard to the timing information extracted from the data stream is estimated by an estimation means. At least two oscillation signals are derived from the at least one oscillation means and are linked together by a linking means yielding said reference frequency. A frequency correction value is applied to at least one of the oscillation signals such that the timing information given by the reference frequency corresponds to the timing information extracted from said data stream.

Abstract: A satellite cluster and method for operating the same. A first module satellite has as a pay load component a receiver unit and/or a transmitter unit for communication with subscriber stations and/or base stations. A second module satellite has as a pay load component a signal processing unit for communication with subscriber and/or base stations. The signal processing unit is integrated in the second module satellite separately from the receiver and transmitter units of the first module satellite. Communication devices for the interaction of the pay load components are included in the module satellites. Each module satellite is controllable separately as an aerospace vehicle such that each respective module satellite is maneuverable out of the cluster and is replaceable by a new module satellite. In one module satellite, the signal processing unit may be integrated as a pay load component separately from the receiver and transmitter units.

Abstract: For determining characteristics of components of a communication channel, for example of a transponder in a communication satellite, a clean carrier signal f(t) is modulated with a pseudo noise signal PN(t) and transmitted through the communication channel at a level below the level of a payload signal which is transmitted via the communication channel simultaneously. The received signal s′(t) is correlated with same pseudo noise signal PN(t) to obtain a recovered carrier signal f′(t). Both the clean carrier signal f(t) and the recovered carrier signal f′(t) can be used to determine the desired characteristics. Since the PN modulated clean carrier signal s(t) is transmitted at a low level, it is possible to perform measurements without switching off the payload signal.

Abstract: The invention refers to an apparatus for generating a reference frequency depending on a timing information extracted from a data stream. In order to generate a carrier frequency in a user station of a satellite TDMA network at low costs which is accurate and stable and which meets stringent phase noise requirements, it is suggested to use at least one free-running oscillator. The frequency deviation with regard to the timing information extracted from the data stream is estimated by an estimation means. At least two oscillation signals are derived from the at least one oscillation means and are linked together by a linking means yielding said reference frequency. A frequency correction value is applied to at least one of the oscillation signals such that the timing information given by the reference frequency corresponds to the timing information extracted from said data stream.

Abstract: The invention refers to a method and an apparatus for determining characteristics of components of a communication channel.

Abstract: In a satellite ranging system predetermined bit sequence or group of bit sequence in a transport stream, which is a digital signal are used to generate trigger signals on the basis of which the delay introduced into the transport stream by the travel path from a satellite ground station to the satellite and back or to another satellite ground station is determined allowing a calculation of the distance between the ground station(s) and the satellite. The predetermined bit sequence or group of bit sequences may be inserted into the transport stream at the uplink site, for example as a specific payload P. In order to avoid insertion of additional packets the transport stream or part of it may be used as a predetermined bit sequence.

Abstract: For determining the operating point of a non-linear amplifier 2 of a communication channel 1, for example of a transponder in a communication satellite, a first input signal I1 is transmitted through the communication channel 1 at a power level PI1 which drives the non-linear amplifier 2 in a non-linear operation mode. In addition, a second input signal i2 is transmitted through the communication channel 1 simultaneously with the first input signal I1. The second input signal i2 is transmitted at a level below the level of the first input signal I1. If the contribution of the second input signal i2 to the total input of the non-linear amplifier is small, the operating point of the non-linear amplifier is determined almost only by the first input signal. Therefore, the output power P02 corresponding to the second signal i2 is determined most strongly by the input power PI1 of the first signal I1.