ATLs (Artificial Transmission Lines) are a promising approach for the design of high performance microwave devices.
An ATL is an effectively homogeneous Transmission Line (TL) achieved by periodically loading a conventional TL with an L-C network either in a low pass topology (right-handed TL) or in a high pass topology (Composite Righ/Left-Handed). The use of ATLs in designing common microwave components adds a degree of freedom which can be exploited in order to achieve dual-band or broadband behaviour as well as a size miniaturization.
An example of ATL-based filter is shown in Fig. 1: a size reduction of 55% has been obtained .
The following figures illustrate some examples of devices which have been designed by the EML2 research group by combining RH ATLs with CRLH ATL. Fig. 2 shows a Rat-Race Coupler consisting of three RH ATLs and a CRLH ATL designed by using lumped L and C elements . Such a coupler is very compact and exhibits a broadband behaviour (see Fig. 3). The implementation of the same device by means of a distributed approach based on Metal Insulator Capacitors and short circuited stubs is illustrated in Fig. 4 .
As for the use of ATL in order to achieve dual-band behaviours, an example of application is given in Fig. 5 where a dual-band T-Junction Power Divider is illustrated .
1. L. Corchia, G. Monti, L. Tarricone, “MEMS-Reconfigurable Bandpass Filter”, Microwave and Optical Technology Letters, vol. 50, no. 8, pp.: 2096-2099, August 2008.
2. G. Monti, L. Tarricone, “Reduced-size broadband ATL-CRLH Rat-Race coupler”, in 2006 European Microwave Week (EuMC), Manchester (UK), September 10-15.
3. G. Monti, L. Tarricone, “Compact Broadband Monolithic 3-dB Coupler by using Artificial Transmission Lines”, Microwave and Optical Technology Letters (published by Wiley), Vol. 50, No. 10, pp.: 2662-2667, October 2008.
4. R. De Paolis, G. Monti, L. Tarricone, “Una Giunzione a T Dual-Band in Tecnologia Composite Right/Left-Handed”, XVII Riunione Nazionale di Elettromagnetismo, Lecce (Italy), September 15-19, 2008