Amplitude comparison DF apparatus for measuring the direction of incoming signals. The apparatus comprises an omnidirectional ring antenna for receiving incoming RF signals. The antenna consists of a ring of air spaced coaxial cable having a plurality of radiating elements symmetrically spaced and positioned about the circumference of the ring in an energy coupling relationship with respect to the ring. Probe apparatus are provided for sampling the coupled energy at selectively predetermined points on the circumference of the ring antenna. Comparison apparatus are provided for comparing the amplitudes of the coupled energy at several sampling points whereby the direction of the incoming RF signal can be determined.
A direction sensitive energy detecting apparatus characterized by having a pair of energy receiving and transmitting devices of different polar characteristics and so disposed that they define together one end of a path in such a way as to be coincident with each other; with the sensor being adapted to give two first outputs at least one of which is variable as a function of the direction of the path and the detector having ratiometric means for generating a second output which is a function of the ratio of the two first outputs and is variable only in response to changes in direction.
Two pairs of signals determinative of bearing to a transmitter are developed from two pairs of directional antennas. The signals, converted to digital form, are compared to each other to develop a result signal. The result signal is used to select a primary pair out of the original two pair of signals. The non-primary pair of signals are compared to each other to develop a binary sign bit. The primary signal pair, the result signal and the sign signal are applied to a table to develop a bearing quantity related to the bearing to the transmitter.
