Polarisation indicator for radio direction finders - uses 90 degree phase shift and 180 degree hybrid circuit

摘要

The polarisation indicator for radio direction-finding systems consists of synchronised microwave switches connected to the horizontal (2) and vertical (3) antenna outputs. The aerial signals are switched alternately to a 90 deg. phase-shift network (10) and tuned line (12) or to a change-over switch (6) and terminating resistor (7). The phase-shifter and tune line are connected to a 180 deg. hybrid circuit (11) whose summing output (13) is connected to a change-over switch (8) and whose difference output (14) is terminated by a resistor (15). An amplitude comparator (9) is connected to the hybrid output or to the two-way microwave switch (6). Comparison of the amplitudes of the four signals provides an indication of horizontal, vertical, right and left circular, positive and negative linear 45 deg. and right and left elliptical polarisation.