Technique for surface to surface communications using high frequency

Abstract

A high frequency (HF) communications buoy that employs HF surface wave, and sky wave, communication and spread spectrum modulation to suppress multipath fading and to decrease the undesired detectability of transmitted signals. The buoy comprises a water-tight floatable enclosure that may be deployed from a flying vehicle or a submerged vessel. An HF communications transceiver is disposed within the enclosure that is capable of transmitting and receiving signals employing high frequency (HF) band surface wave and sky wave propagation. The transceiver further comprises spread spectrum modulation and demodulation circuitry for modulating transmitted signals utilizing spread spectrum modulation and for demodulating received signals encoded by means of spread spectrum modulation. The spread spectrum modulation and demodulation circuitry is provided to suppress multipath fading and decrease the probability of detection of transmitted signals. An antenna is coupled to the transceiver and supports the transmission and reception of the high frequency (HF) spread spectrum modulated signals. The use of HF surface wave communications in conjunction with the spread spectrum modulation of the transmitted signals provides for networking of a plurality of buoys. The use of HF spread spectrum communications also reduces the probability of exposing the presence and location of the transmitting terminal and eliminates multipath interference between ground wave and sky wave transmissions, or transmissions reflected from different sky wave layers. In addition, utilization of the underwater communication circuitry permits a submerged vehicle to take advantage of the relatively secure communications link provided by the present invention.