Antenna Multi-Band Enhancement by Employing Negative Impedance Converters

This thesis presents the implementation of a Negative Impedance Converter (NIC) integrated with a planar monopole antenna, originally centered at 2.9 GHz, to create a multi-band network. The network exhibits resonances at frequencies of 0.9 GHz, 1.5 GHz and 1.9 GHz. The work highlights the design process of pairing a NIC with a capacitive, single-band antenna, addressing key challenges such as overcoming the limitations associated with low self-resonant frequency (SRF) inductors. The design process included the use of measurement-based component models and radio-frequency simulations using Keysight Advanced Design Systems (ADS). The developed NIC emulates a -0.99 pF capacitor using two BFR93A transistors. The boards were fabricated on Rogers RT/duroid 5880, laser machined using a picosecond laser and subsequently tested for its scattering parameters. Performance measurements at both, without DC bias and 10 V, revealed a notable difference in matching between the active and passive states, confirming that the NIC effectively supersedes the passive matching of its components.