Abstract: Boeing achieves satellite diversity by having a large discrimination angle for a MEO constellation of communications satellites to limit interference in the Ku-band with GSO communications systems. Each satellite entering an exclusion zone over a GSO ground station terminates all transmissions to provide EPFD within acceptable limits. The Boeing MEO constellation preferably comprises 20 satellites, 5 in each orbit. The four orbits are inclined at about 57° with respect to the equator. Services include an Integrated Digital Service (IDS) and Backhaul Data Service (BDS) to accommodate the needs of different users.

Abstract: An error control decoder (44) for use in decoding signals encoded with an M-ary convolutional code and a method for decoding such a code. The error control decoder includes a branch metrics module (46) that determines differences between the correlation values of each of eight possible symbols used to represent data encoded and the largest of these correlation values. An add-compare-select module (50) determines path metric values for each of 64 states by adding selected branch metric values to prior state metrics for the two possible paths that lead to a current state metric. The minimum path metric of the two is then assigned as a new state metric, and a logic level identifying the selected path metric is stored in a path history module (62). This procedure is repeated for each of the 64 states. A minimum state metric from the prior symbol period is determined and used to normalize the current state metrics to avoid overflow.

Abstract: Apparatus and a method for transmitting a direct sequence, spread spectrum communication system signal. A transmitter (10) that receives a variable data rate information bearing input signal from a digital data source (12) includes a forward error correction encoder (80) that provides redundancy and an interleaver (82) that rearranges the input data. The forward error correction encoder and interleaver minimize the effect of errors that arise in the propagation of the transmitted signal. The output of the interleaver is applied to the input of a Hadamard encoder (84), which converts data words from the interleaver into one of N orthogonal codes, producing a Hadamard signal that varies at a bit rate that changes as the data rate of the information bearing signal varies. A pseudorandom number code generator (16) produces a code signal comprising a pseudorandom sequence of chips supplied at a constant chip rate.

Abstract: A charge-coupled device (CCD) used as a demodulator and a correlator in the receiver of a spread spectrum radio system. The device implements both functions in the charge domain, thereby avoiding unnecessary conversions between voltage and charge that would normally be required if the functions were separately implemented. In its preferred form, the demodulator and correlator include an in-phase filter (170), a quadrature filter (172), delay circuits (174, 176), decimation circuits (181-184), correlators (191-194), and signal combiners (200, 202). The delay circuits are used in the preferred embodiment to compensate a time shift between the in-phase and quadrature channels that result from the minimum shift keying modulation used, but would not necessarily be required for other types of modulation. The decimation circuits match the data rate of the in-phase and quadrature filters to the data rate used by the correlators, which is determined as a function of chip rate used to spread the data.