Communications: radio wave antennas – Antennas – Balanced doublet - centerfed
Patent
1978-08-24
1980-12-16
Blum, Theodore M.
Communications: radio wave antennas
Antennas
Balanced doublet - centerfed
H04B 700
Patent
active
042400791
ABSTRACT:
A system for locating mobile objects in distress comprises emergency radio stations provided on the mobile objects and energized when these mobile objects are in distress, at least one low orbiting earth satellite for retransmission of the signals from the emergency stations, at least one control station for tracking the earth satellite and determining its ephemeris, and at least one receiving station connected with the control station by a communication link and designed for reproduction of the messages transmitted by the emergency stations and for location of the mobile craft. The emergency radio stations are divided into groups with a specified pattern of the two components of a phase-shift-keyed signal, alternating in accordance with the transmitted message, assigned to each group. The receiving station includes a receiver, a reference-frequency oscillator, a signal processing device, their number being equal to that of the groups of emergency stations, and a computer for calculation of the coordinates of the emergency stations, with the input of the computer connected to the communication link. Each of the signal processing devices comprises a first filter and a second filter matched with the first and the second components of the signal from one of the groups of emergency radio stations, respectively, and connected to the output of the receiver, first and second detectors with their inputs connected to the outputs of the first and second filters, respectively, an adder with the two inputs thereof connected, respectively, to the outputs of the first and second detectors, tracking systems provided with a second-order astaticism for measuring the running phase of the envelopes of the received signals from the emergency stations, one of the inputs of each tracking system being connected with the output of the reference-frequency oscillator, and one of its outputs being connected with the other input of the computer, gates with their number equal to that of the tracking systems, and decoders with their number also equal to that of the tracking systems, for decoding the messages transmitted by the emergency stations. The signal inputs of the gates are connected to the output of the adder, the output of each of the gates is connected with the other input of one of the tracking systems, the inhibit inputs of each gate being connected with the other outputs of the remaining tracking systems. Two inputs of each of the decoders are connected to the outputs of the first and second detectors, respectively, while the control input of each decoder is connected with the other output of one of the tracking systems. The proposed system provides the capability of simultaneous operation of a large number of emergency radio stations within one common frequency band.
REFERENCES:
patent: 4144495 (1979-03-01), Metzger
Blum Theodore M.
Nissen J. Harold
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