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Dynamic Testing of Frequency Agile Radios BILL FLERCHINGER * TOM HIGGINS RF & Microwave Measurement Symposium and Exhibition Flin- HEWLETT ~e. PACKARD www.HPARCHIVE.com Bill Flerchinger Bill is a Regional Sales Engineer from t.he Spokane Division. lIe graduated from Washington State University with a BSEE and is currently working on his Master from WSU. Tom Higgins Tom received his BSEE from Montana State University in 1985. As ault&D eugineer, Tom worked on RF microcircuits for pulse generation in sigual generators, a rcfreuce loop and a floating am- plifier in a uew function generator. He is currently working on his Masters from WSU. 2 www.HPARCHIVE.com TESTING FREQUENCY AGILE RADIOS With the technology in communications advancing every day, more complex communications systems have emerged. These newer communications systems have been developed for several reasons. They allow a means to more efficiently send information, to resist interference from the surrounding environ- ments, to secure the information being sent from outside parties, to resist being jammed intentionally from a third party, etc. One of the methods used by radio manufacturers that give a user additional performance capability is to use spread spectrum techniques. Basically, the idea behind using spread spectrum is to take the normal bandwidth of the information being sent and either spread it out (that is to add additional signal to the transmitted information so that its effective bandwidth is increased consid- erably) or to take the normal R.F. occupancy and spread it over a large number of frequencies (being several octaves or even decades apart) or a combination of the two. In both cases, the information is being transmitted in a much wider bandwidth than if no spreading was used. This increased bandwidth makes the spread spectrum system more jam or interference resistant. It also helps avoid signal fading common in fixed frequency systems due to multi-path signal cancellations. Military tactical radios are a prime example of these techniques in use. The need for secure, jam resistant, reliable communications is extremely important in field use. Radio manufacturers like ITT, Magnavox, Racal, Thompson, B.E.L., Harris, Marconi, etc., are or have developed radios that change frequency from a few times a second, to thousands of times a second. While production of these radios has increased immensely in recent times, very little, if any commercial test equipment has been developed for testing these radios. Manufacturers have had to design custom test fixtures adapted from their own radio hardware that are expensive and limited in capability. These test fixtures allowed manufacturers to develop