 Melpar consultant, were held under secrecy along with the WICS patent until the mid-1970s. An unclas- sified discussion of an MF-SS system for use against multipath is given in [200]. Kathryn: Named after the daughter of the inventor, William Ehrich, and developed by General Atronics, Kathryn's novel signal processing effected Branches on the SS Tree OSCILLATOR RECEIVER MIXER FILTER CIRCUIT OSCILLATOR MIXER FILTER CIRCUIT SPACE MAGNETIC CONTROL FILTER PLAYER PROGRAM GENERATOR SYNCHRO SPACE FILTER PHASE STORAGE & LOGIC SHIFT FREQUENCY STANDARD TAPE PUNCHER Figure 2.30. The receiver block diagram redrawn from Wozencraft's patent applica- tion [197] is shown here with magnetic tape used for storage of independent pseudo- random FH signals for MARK and SPACE reception. The Historical Origins of Spread-Spectrum Communications TRANSMITTER F 27s F 34m F 14s F 23m MATCHED FILTER PULSE SHAPER CIRCUIT Figure 2.31. Guillemin's patented filter system design [199] is shown here imbed- ded in the transmitter's modulation generator described in the patent [198] of Kohlenberg, Sussman, and Van Meter. Filter sections were switched in and out according to a schedule recorded on an endless punched tape (and as shown here, punched tape was also used as a binary data source). The receiver contained a cor- responding matched filter, synchronously controlled by an identical tape. Branches on the SS Tree the transmission of the Fourier transform of a time-multiplexed set of chan- nel outputs combined with a PN signal. Upon reception, the inverse trans- form yielded the original PN X multiplexed-signal product, now multiplied by the propagation medium's system function, thereby providing good or bad channels in accordance with that function. When jamming is present, the data rate is reduced by entering the same data bit into several or all data chan- nels. In this case, a Rake-like combiner is used to remerge these channels at the output of the receiver's inverse Fourier transformer [148], [201]. The modern SS enhancement technique of a