Active antenna arrays using tunnel devices

The heterostructure interband tunnel diode (HITD), when appropriately biased, exhibits RF negative resistance and can be used in VCOs, mixers and active antenna circuits. However, the DC instability issues associated with the diodes prevent them from being used in RF applications. To overcome the instability, the DC blocking capacitors are used to enforce individual bias conditions for the diodes in this work. A five-elements active antenna array is designed, fabricated, and tested. Experimental results are presented and compared with simulations. The beam steering can be achieved, by either controlling the number of the working diodes, or changing the phase difference between the two signals applied to the two end-elements.