Evaluation of an ultra-wideband diplexer for simultaneous UHF and X-band operation using modulated Gaussian pulses

Multi-band antennas are rarely well-matched between feedpoint and transceiver when the antenna bands are separated by more than an octave. Often, multiple antennas, each assigned its own band, are substituted for a single antenna when the frequency ratio is prohibitively large. To realize a common multi-frequency architecture, the antennas and transceiver are linked by a multi-band matching network. Dual-band radio-frequency matching networks currently achieve frequency ratios up to approximately 6:1. RF networks designed to operate in two bands whose frequencies differ by more than 6:1 are not yet well-established. In this paper, an ultra-wideband diplexer is presented as the matching network to achieve operation at X-band and UHF frequencies at a ratio of 7:1. Dual-band operation is demonstrated in simulation using a time-frequency technique: modulated Gaussian-envelope pulses ported between Matlab, PSpice, and Fourier-transformed to calculate scattering parameters.