Receivers for an aircraft landing system

Claim 1

A RECEIVER FOR USE IN AN AIRCRAFT LANDING SYSTEM OF THE TYPE WHICH YIELDS TWO DOUBLE SIDEBAND GUIDANCE SIGNALS THE RELATIVE AMPLITUDES OF WHICH ARE INTENDED TO BE A MEASURE OF THE POSITION OF A RECEIVER RELATIVE TO A PREFERRED APPROACH PATH, AND COMPRISING: A SUPERHETERODYNE RADIO RECEIVER FOR RECEIVING AN ILS GUIDANCE SIGNAL; RESOLVING MEANS CONNECTED TO THE SUPERHETERODYNE RADIO RECEIVER FOR DERIVING TWO UPPER SIDEBAND SIGNALS OF AMPLITUDES RESPECTIVELY RELATED TO THE AMPLITUDES OF THE TWO UPPER SIDEBAND COMPONENTS OF TWO DOUBLE SIDEBAND GUIDANCE SIGNALS AND FOR DERVING TWO LOWER SIDEBAND SIGNALS OF AMPLITUDES RESPECTIVELY RELATED TO THE AMPLITUDES OF THE TWO LOWER SIDEBAND COMPONENTS OF THE TWO DOUBLE SIDEBAND GUIDANCE SIGNALS; FIRST MEASURING MEANS CONNECTED TO THE RESOLVING MEANS FOR DERIVING FROM THE SAID TWO UPPER SIDEBAND SIGNALS A FIRST DIFFERENCE SIGNAL INDICATING THE DIFFERENCE IN THE AMPLITUDES OF THE SAID TWO UPPER SIDEBAND COMPONENTS OF THE TWO DOUBLE SIDEBAND GUIDANCE SIGNALS; SECOND MEASURING MEANS CONNECTED TO THE RESOLVING MEANS FOR DERIVING FROM THE SAID TWO LOWER SIDEBAND SIGNALS A SECOND DIFFERENCE SIGNAL INDICATING THE DIFFERENCE IN THE AMPLITUDES OF THE SAID TWO LOWER SIDEBAND COMPONENTS OF THE TWO DOUBLE SIDEBAND GUIDANCE SIGNALS; AND INDICATING MEANS CONNECTED TO THE FIRST MEASURING MEANS AND TO THE SECOND MEASURING MEANS, FOR INDICATING A DISCREPANCY BETWEEN THE FIRST DIFFERENCE SIGNAL AND THE SECOND DIFFERENCE SIGNAL.