THEORY OF ACTIVE NONRECIPROCAL NETWORKS
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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The investigation sets forth theory and experimental data for active nonreciprocal networks. A simple way is shown of achieving nonreciprocity using a magnetic field device exhibiting small amounts of differential phase shift. In the theoretical treatment, use is made of scattering parameters. The effect on nonreciprocity of having cascaded and parallel connected elements is considered. How matching and scattering from various junctions influences nonreciprocity is included. Two simple devices exhibiting nonreciprocity are discussed in detail a differential amplifier, and a differential attenuator and a procedure is given for their use in active network synthesis. For these devices, the meander line is the nonreciprocal element utilizing a magnetic field. A new meander-line design is presented, realizing a desired impedance, based on recent data on odd- and even-mode velocities along coupled microstrips. From the experimental work, data are reported on a meander line showing impedance characteristics which are in good agreement with theory and showing the amount of differential phase shift possible. To realize an element with loss, an experimental bilateral microstrip attenuator is described whose resistances are short silver-deposited lines. Measurements show satisfactory matching for a 6-dB model. A complete design is given for a microstrip differential attenuator using the loss and nonreciprocal elements mentioned operating near 3 GHz. Scattering parameters measured on a model differential attenuator show very close agreement with theory. Data are presented on both the differential attenuation and the insertion loss of this realized model.
- Electrical and Electronic Equipment