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Two experimental models of a digital processing transceiver have been designed, constructed and tested. The transceiver modulation capability is multi-mode (AM, SSB, FM, PM, FSK) and the unit is capable of operation in the HF and VHF frequency bands. The concept of digital equivalent processing in terms of satisfying typical radio specification requirements in real time has been proven by extensive testing.

A modification to the network, the all-pass half-lattice network was studied for its variable time delay properties and implemented to obtain time delay variation of 72 nanoseconds in excess of a constant delay. Twenty sections were cascaded to obtain the delay variation. The controlled elements were 2 capacitors and 3 resistors. The cascade could be switched from one delay state to a second delay state within 10 microseconds. The signal bandwidth goal was 20 Mc. The signal bandwidth achieved was 40 Mc, the band extending from 20 Mc to 60 Mc. An all-pass resistance-capacitance section was developed, providing a simpler control of the time delay. A variable voltage applied to a varactor was the complete control mechanism for the section. A total of 18 sections were cascaded to demonstrate the feasibility of the technique. A time delay variation of 23 nanoseconds was available with a switching time of 5 microseconds to change the delay state. The signal bandwidth obtained exceeded that of the lattice network approach. A bandwidth of 65 Mc, the band extending from 15 Mc to 80 Mc, was achieved. (Author)

This report presents the results of a 12-month program to design, fabricate and test two identical, digitally variable, wideband, time delay units applicable to time delay steering of broadband arrays. A delay variation of 15 nanoseconds is obtained in each unit by electrically switching one of more strip transmission delay lines, into the signal path. The unique feature in the developed hardware is the use of an all-pass time delay network to provide straightforward control for triming of the incremental delay elements. This network provides a delay variation of 100 picoseconds and a 400 MHz signal bandwidth with measurement accuracy on the setting being + or - 5 picoseconds. (Author)