Wide-band transhorizon channel sounding at X-band.
This thesis describes a wide-hand channel sounding experiment carried out at the X-hand
frequency over a transhorizon, sea path.
The design of a wide-band channel probe is described in detail based upon the following
operational requirements. "To capture as many sequential estimates of the transfer function of
a telecommunication channel as possible, over the widest possible band-width and in the
shortest time, subject to the constraint of low signal-to-noise ratio".
The design described includes generation of a specialised, band limited, spectrally clean,
synthesized test signal for bandwidth optimisation and the use of real-time, periodic averaging
for signal-to-noise ratio enhancement. An external frequency reference has been used in
preference to a carrier locked approach. The theoretical justification and hardware implications
of this design approach are carefully argued in the thesis.
Such a probe has been built, its dynamic performance assessed and compared with more
conventional transfer function analyser designs. In particular the frequency stability of the
unlocked system configuration and the problem of signal distortion due to excessi ve phase noise
are explored in detail.
The concept of time domain multi-ray modelling of a telecommunication channel has
stimulated the application of high resolution spectral analysis techniques for ray parameter
determination. A brief literature survey of various algorithms is presented and a comparison
with the conventional Fourier approach is given. Detailed derivation of the Singular Value
Decomposition - Prony (SVD-P) algorithm is presented together with an in-depth performance
assessment over a wide-variety of simulated channel conditions.
The measurement equipment was completed, tested in the laboratory and finally
commissioned in May 1993. A long-term data capture campaign was started using an existing
cross channel link; a large database of results has subsequently been obtained. Preliminary data
analysis has been carried out and the thesis describes the phenomenological characteristics of
the channel whilst subjected to a wide range of multipath propagation mechanisms.
The final chapter of the thesis highlights the novel achievements of the research, together with
a summary of the strengths and limitations of the experimental equipment and processing