Modified rectangular oscillating patch antenna with bipolar transistor

A new self-oscillating antenna built by integrating a bipolar transistor and a line impedance transformer in a rectangular opening inside a rectangular patch is presented. This compact and low cost design showed a very linear change of the oscillating frequency with the DC bias voltage. A clean spectrum was observed in the whole tuning range. The radiation patterns show no degradation in comparison to a non-modified patch. The cross-polarization levels in both the E and H planes are low. The possibility of external injection locking has been demonstrated.