Accession Number : ADA195445

Title :   Frequency Hopping With Analog Messages.

Descriptive Note : Master's thesis,

Corporate Author : NAVAL POSTGRADUATE SCHOOL MONTEREY CA

Personal Author(s) : Kardisan, Suwito

PDF Url : ADA195445

Report Date : Mar 1988

Pagination or Media Count : 43

Abstract : Frequency hopping (FH) is used by the military as an electronic counter-counter-measure (ECCM) technique. The carrier frequency is caused to vary from one value to another over a range of values in usually a random or pseudo-random manner. The message is converted to binary form. In slow FH, several bits are sent per hop. In fast FH, several hops occur per bit. This research considers use of analog messages (voice) with FH. No analog to digital conversion is used. An important consequence is that there is no clock in the system. Hopping can be and should be random in time as well as in frequency. A FH transmitter and receiver were built and tested using analog messages. The message is carried using amplitude modulation. This permits recovery of the message asynchronously in the receiver using an envelope detector. Further, an envelope detector is relatively insensitive to variation in frequency of the carrier. Clocked (pseudo random) FH is used with receiver hopping synchronization provided by hard wire. The voice signal was recovered (heard) with little apparent distortion. Random hopping is also employed with noise determining each hop time. A receiver self synchronizing circuit was designed and used in this case. Because of the chosen design, interference and amplitude fluctuation of the recovered audio (intelligible) is experienced. Keywords: Theses; Circuit computations.

Descriptors :   *MESSAGE PROCESSING, *PSEUDO RANDOM SYSTEMS, *SYNCHRONIZATION(ELECTRONICS), *VOICE COMMUNICATIONS, *WIRE, AMPLITUDE, AMPLITUDE MODULATION, ANALOG TO DIGITAL CONVERTERS, CARRIER FREQUENCIES, CIRCUITS, COMPUTATIONS, DETECTORS, DISTORTION, ELECTRONIC COUNTER COUNTERMEASURES, ENVELOPE(SPACE), FREQUENCY, HARDNESS, RECEIVERS, RECOVERY, SENSITIVITY, SIGNALS, THESES, VALUE, VARIATIONS

Subject Categories : Voice Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE