External Timebase Trials for Phase Coherency of a Bistatic Transfer Function Measurement Setup

In this paper a comparison between several external timebase references for clock synchronization and phase coherency between the transmitter and receiver of a bistatic complex transfer function measurement setup is presented. In order to derive rural environmental clutter models, the complex transfer function (amplitude and phase response) of rural environments e.g. forests or farmland is estimated from measurement data. The transmitter and receiver are separated to be able to measure the rural scenes at different spatial points. For the estimation of the phase response, a phase coherency between the transmitter and receiver clocks is required. Therefore, the internal transmitter and receiver clocks must be synchronized to an external timebase reference signal. One possibility of achieving this is to distribute an external 10 MHz clock signal, which replaces the internal timebase references. We have investigated several methods for generating and distributing the 10 MHz signal between the transmitter and receiver of the measurement system and present the resulting phase error distributions.