Alarm system for a Costas loop used in a digital radio relay transmission device

摘要

Alarm device capable of indicating the condition of release or of incorrect blocking of a Costas' loop. The saturated eyes (X1, Y1) of each of the two quadrature channels (X, Y) of the demodulated signal are applied to a differentiator (28, 29) of their rising and falling fronts, the output signals (30, 31) of which are applied to an "OR" gate. If the margins of these eyes (X1, Y1) are partially or fully closed, series of pulse doublets are obtained, which are separated by the bit width, which is detected by a circuit comprising a divider by four (41) and a reset-to-zero oscillator (43). The presence, in this case, of broad output pulses (S) is detected by an integrator (47) followed by a threshold circuit (50). IMAGE