Analysis of coplanar waveguide radiating end effects using the integral equation technique

An integral equation technique solved by the moment method associated with the single one-port model is used to analyze radiating end effects of coplanar waveguides (CPWs). This analysis has the advantage of being performed in the space domain, which allows the electric and magnetic field distributions in the whole space to be determined directly without the use of an inverse Fourier transform. An experimental method is given for the measurement of the reactance of a CPW short circuit end that allows its radiation resistance to be determined. It is shown that this resistance increases with frequency. Two examples of calculated results that give the electric field distribution in the two slots are given. The first one represents a CPW mode (odd mode), while the second represent an even coupled slots mode. The normalized reactance obtained by the present theory is compared with previously obtained measurements. The comparison shows a very good agreement. The results of a comparative study of the short-end equivalent impedance for a slotline and a CPW having the same slot width operating once in the odd mode (coplanar mode) and another time in the even mode are given. The results clearly show that the CPW operating in the odd mode has very low radiation properties when compared with the slotline and coupled slotlines operating in the even mode