Ambiguity Plane Research Articles

Wideband signal Doppler and epoch estimation

The authors propose a preamble signalling method for Doppler and epoch estimation that does not require searching on the two dimensional ambiguity plane, but rather is accomplished by simple and sequential one dimensional searches. This method is based on a relatively new class of functions.

Impact of the ocean acoustic transfer function on the coherence of undersea propagations

Multipath propagation, in conjunction with source motion, creates a splitting and spreading of the received source-signal energy over the time register time scale-factor (ambiguity) plane. This splitting of the received signal energy is manifested as correlation interactions between both; the set of eigenray signal arrivals (comprising the multipaths) at each receiving sensor, and the set of eigenray signal correlation pairs comprising two (or more) sensors. The more tightly the sets of eigenray signals are clustered in the ambiguity plane, the stronger will be the signal component interactions at each sensor and the less will be the expected correlation degradation between sensors. However, the greater will be the variance. Conversely, the more diffuse the clustering, the weaker will be the signal component interactions and the greater will be the expected intersensor coherence degradation. Also, the less will be the variance. Criteria which define the degree of signal component interactions in terms of the signal and the ocean transfer function parameters have been defined and are displayed in graphical form.

Optimum Signals for Radar

The research reported herein deals with the general problem of the selection of radar waveforms. The investigation is specifically concerned with the synthesis of radar signals which are optimum in the sense that they are characterized by ambiguity surfaces minimized over certain predetermined regions of the ambiguity plane. The weighted ambiguity surface is utilized as the weighted error criterion. This error criterion is mathematically tractable and pertinent to radar system performance but is not unduly restrictive as some orientation parameters are left unspecified for subsequent cost or penalty function analysis. The signal optimization is approached by variational techniques augmented by equality and inequality constraints, for example, limiting the amount of bandwidth or frequency modulation to be less than some system requirement. Several examples are presented demonstrating the optimization techniques and providing a minimum error for the stated problem. It is shown that for any given type of amplitude modulation of the radar signal, the variance or dispersion of the ambiguity surface is not decreased for any type of phase modulation added. The optimum signal for an elliptical weighting function is derived for several cases. The minimum error is shown to depend upon the constraints and the unspecified orientation parameters and, for one case, on the second moment of the signal.