Background: This paper presents the design and implementation of an ultra-wideband
transition from double-sided micro-strip to parallel-strip line which is usually used as balanced antenna
Methods: This transmission is composed of a near-optimum taper of metal on top layer and exponential
taper of ground on bottom layer. The transmissions were simulated and optimized by CST Microwave
Studio and then they are fabricated. Finally, the results of simulations and measurements are compared.
Results: The measured results show that the performance of two back-to-back near-optimum taper
transmission possesses a return loss of better than 10 dB and insert loss of one transition less than 1 dB
over a bandwidth from 1.20 to 5.75 GHz (1:4.8). For a wider bandwidth, an insert loss of one transition
less than 3 dB and return loss better than 10 dB can be achieved from 1.20 to 9.68 GHz (1:8.1). With
100 ohm resistor loading, the return loss of near-optimum taper transmission better than 10 dB can be
received from 0.86 to 11 GHz (1:12.8).