Active-notch antennas stabilized with a slotline-ring resonator for wireless applications

This article discusses the design and measurements of two compact and low-cost Gunn-diode active-notch antennas and compares the results with a similarly configured passive antenna. The antennas feature a slotline-ring resonator for frequency stabilization and external Q improvement. The active antennas' radiation patterns compare well with those measured for a similar passive antenna. The active antenna can incorporate a varactor for frequency tuning with a frequency range of about 400 MHz or 4.2%. This circuit should have many applications in wireless communication, sensor, RF identification, or Doppler radar applications.