This paper presents a bidirectional coupler which is designed by combining nonuniform wiggly lines and the reflected power canceller (RPC) method. The combination not only brings about a high directivity but also makes a wideband structure with a compact size. Although, in the RPC method, an idle port is used to produce a reflected signal in order to achieve a high directivity, there are not any idle ports in the proposed coupler. The coupler was built on an FR4 substrate. The measurement results show that this structure is suitable to monitor forward and reflected signals in high power applications. The fabricated coupler has the directivity of more than 22 dB and the coupling flatness of ±0.12 dB in the forward and backward signals in a wide frequency range of 140 MHz-190 MHz.
2. Chun, Y., J. Moon, S. Yun, and J. Rhee, "Microstrip line directional couplers with high directivity," Electronics Letters, Vol. 40, No. 5, 317-318, March 4, 2004.
3. Moscoso-Martir, A., I. Molina-Fernandez, and A. Ortega-Monux, "High performance multi-section corrugated slot-coupled directional couplers," Progress In Electromagnetics Research, Vol. 134, 437-454, 2013.
4. Hrobak, M., M. Sterns, E. Seler, M. Schramm, and L. Schmidt, "Design and construction of an ultrawideband backward wave directional coupler," IET Microwaves, Antennas & Propagation, Vol. 6, No. 9, 1048-1055, June 19, 2012.
5. Sohn, S., A. Gopinath, and J. T. Vaughan, "A compact, high power capable, and tunable high directivity microstrip coupler," IEEE Transactions on Microwave Theory and Techniques, Vol. 64, No. 10, 3217-3223, Oct. 2016.
6. Pelaez-Perez, A. M., P. Almorox-Gonzalez, J. I. Alonso, and J. Gonzalez-Martın, "Ultra-broadband directional couplers using microstrip with dielectric overlay in millimeter-wave band," Progress In Electromagnetics Research, Vol. 117, 495-509, 2011.
7. Yıldırım, B. S. and K. Karayahsi, "Broadband UHF microstrip coupler," AEU --- International Journal of Electronics and Communications, Vol. 108, 2019.
8. Maloratsky, L. G., Passive RF & Microwave Integrated Circuits, Elsevier/Newnes, Amsterdam, 2004.
9. Singh, S., R. P. Yadav, and A. Jain, "Miniaturized dual-band branch-line coupler with folded stubs," 2019 IEEE 5th International Conference for Convergence in Technology (I2CT), Bombay, India, 2019.
10. Coromina, J., P. Velez, J. Bonache, and F. Martın, "Branch line couplers with small size and harmonic suppression based on non-periodic step impedance shunt stub (SISS) loaded lines," IEEE Access, Vol. 8, 67310-67320, 2020.
11. Liu, G.-Q., L.-S. Wu, and W.-Y. Yin, "A compact microstrip rat-race coupler with modified lange and T-shaped arms," Progress In Electromagnetics Research, Vol. 115, 509-523, 2011.
12. Kirschning, M. and R. H. Jansen, "Accurate wide-range design equations for the frequency-dependent characteristic of parallel coupled microstrip lines," IEEE Transactions on Microwave Theory and Techniques, Vol. 32, No. 1, 83-90, Jan. 1984.
13. Uysal, S., Nonuniform Line Microstrip Directional Couplers and Filters, Artech House, 1993.