Broadband Impedance Transformer Based on Asymmetric Coupled Transmission Lines in Nonhomogeneous Medium

Abstract

-A new broadband quarter-wavelength impedance transformer based on an asymmetric coupled line section is presented. The bandwidth of the coupled line transformer is extended with the help of an interconnecting transmission line. An analytical model for the transformer is developed. The analysis of the structure reveals that a fractional bandwidth of more than 100% at -20 dB reflection level can be achieved with such a structure. An experimental transformer circuit has been designed, fabricated and tested. Theoretical and experimental results are fair agreement and confirm the established theory. The achieved bandwidth is almost 3 times larger as compared with standard matching circuits.

Coupled Transmission Lines as Impedance Transformer

“…The wideband impedance transformer proposed in this section is derived on the basis of asymmetric, uniformly coupled lines in a nonhomogeneous medium [5]. A microstrip line is one of the most commonly used classes of transmission lines in a nonhomogeneous medium.…”

“…In [5] a broadband impedance transformer based on coupled transmission lines is presented. The synthesis procedure for this circuit is explained.…”

Compact multiband antenna fed with wideband coupled line impedance transformer for improvement of impedance matching

“…A general coupled line configuration and broad band impedance transformer are presented by Pozer . Figure shows the general coupled line configuration.…”

“…Figure shows the general coupled line configuration. The Z ‐matrix for four port open circuit coupled line section is given in terms of even and odd mode impedances Z 0E , Z 0O , and electrical length in radian 6 as, where …”

“…The WCLIT proposed in this section is asymmetric uniform coupled line in a non homogeneous medium, The proposed WCLIT is a, λ/4 wavelength long and provide three times wider frequency range compare to QWT . The matching properties of WCLIT depend on coupled line parameter as well as load at port 2 and port 4.…”