Military satellite communications systems may be implemented with varying levels of satellite on-board processing. For frequency-hop (FH) spread-spectrum signals two options are the dehop-rehop transponder (DRT) and the symbol regenerative processor (SRP). This paper considers FH,M-ary FSK modulation in the presence of full band and worst case partial-band noise jamming. The relationships among end-to-end signal-to-noise ratio (SNR) performance or probability of bit errors and the uplink and downlink SNR are derived. For a DRT, an additional parameter is the satellite filter bandwidth Wssince this may differ from the despread modulation bandwidth Wrfor a particular user access under TDMA variable-data-rate operation. The SNR performance in this case depends upon the ratioW_{s}/W_{r}a well as the uplink and downlink SNR. The resulting penalty in the link budget of the weaker of the uplink or downlink is much less than the mismatched ratioW_{s}/W_{r}and diminishes as the links become unbalanced. The SRP slightly outperforms the DRT but it is more complex and does not as easily accommodate variable data rates.

The rationale and a preliminary design concept are presented for a new mobile ground-to-ground communications system to support tactical command and control. Survivability is attained through high connectivity, antenna directivity, and spread-spectrum signals. Each node of the proposed network is equipped with a circular cylindrical array antenna capable of steering a narrow beam in the direction of one of its several neighbors. A single transceiver operates half-duplex m a flexible time-division format among the multiple links at a node. Each link uses a unique pseudonoise code, and the network as a whole employs code-division multiple access. Mobility and survivability are enhanced because a single equipment supports multiple links while providing the benefits of high antenna gain and directivity. Network entry and synchronization schemes are considered. System parameters are defined and link power budgets for signal-to-jammer and signal-to-noise ratios are calculated. Implementation prospects are addressed drawing on technology developments in antenna arrays, surface-acoustic wave signal processing, and adaptive routing in packet networks.

The synthesis of radar ambiguity functions is approached by minimizing the integrated square error between an arbitrary desired function and a realizable ambiguity function. The approximation is carried out via an orthonormal signal basis which generates an "induced basis" over the time-frequency plane consisting of all pair-wise cross-ambiguity functions of the signal basis. The minimum mean-square error and the corresponding signal are determined through an eigenvalue problem for 1) approximation by complex autoambiguity function and 2) approximation by complex cross-ambiguity function. A new form of the realizability theorem shows that the conditions for cross-ambiguity functions differ from those for autoambiguity functions only in the absence of the symmetry condition:F(\tau, \omega) = F^{\ast}(-\tau, -\omega). Moreover, the approximations by cross- and autoambiguity functions coincide whenever the desired function has the above symmetry. When an ambiguity function realizable by a known signal is to be approximated on a finite basis, least-square approximation in signal space or in ambiguity-function space leads to equivalent results. The relation between the mean-square errors in the two spaces is obtained. For the phase incoherent radar case an iteration procedure is presented for successively modifying the arbitrary phase assigned to the desired function. Convergence is proved in the sense that the error is nonincreasing at each stage of the iteration, but arrival at the best approximation to the desired magnitude is not guaranteed. As an aid in numerical applications, a formulation based on a discrete sample grid in the time-frequency plane is derived. With the appropriate grid dimensions, the analytic procedures carry over directly into sampled-data representation.

A matched filter communication system is described whose underlying principles are based on the Rake. The point-to-point synchronous teletype system employs complex lumped-parameter networks to generate and receive a pair of long-duration, broadband signals representing Mark and Space respectively. The receiver contains a pair of matched filters whose output is a narrow pulse when the matching waveform is applied. One advantage of the system, arising from the long duration of the signals, is an increase in energy per teletype baud when operating under a peak power limitation. Another is that multiple propagation paths due to ionospheric reflection are resolved by the broadband signals, resulting in the appearance of the multipath pattern at the output of the Mark or Space matched filter. Recombination of paths is achieved by means of a recirculating delay line tuned to the teletype baud rate in conjunction with parallel multiplier-integrators in the Mark and Space channels. The combination acts as a self-adjusting correlation detector for the multipath pattern.