1. W. A. Tyrrell, "Hybrid circuits for microwaves", Proc. IRE., vol. 35, pp. 1294-1306, Nov. 1947.
 
2. S. B. Cohn, "The re-entrant cross section and wide-band 3-dB hybrid couplers", IEEE Trans. Microw. Theory Techn., vol. MTT-11, no. 4, pp. 254-258, Jul. 1963.
 
3. B. Sheleg, B. E. Spielman, "Broadband (7–18 GHz) 10 dB overlay coupler for MIC application", Electron. Lett., vol. 11, no. 8, pp. 175-176, Apr. 1975.
 
4. G. H. Zhai, W. Hong, K. Wu, J. X. Chen, P. Chen, J. Wei, H. J. Tang, "Folded half mode substrate integrated waveguide 3 dB coupler", IEEE Microw. Wireless Compon. Lett., vol. 18, no. 8, pp. 512-514, Aug. 2008.
 
5. A. A. Sakr, W. M. Dyab, K. Wu, "Theory of polarization-selective coupling and its application to design of planar orthomode transducers", IEEE Trans. Antennas Propag., vol. 66, no. 2, pp. 749-762, Feb. 2018.
 
6. A. A. Sakr, W. M. Dyab, K. Wu, "Design methodologies of compact orthomode transducers based on mechanism of polarization selectivity", IEEE Trans. Microw. Theory Techn., vol. 66, no. 3, pp. 1279-1290, Mar. 2018.
 
7. S. I. Shams, A. A. Kishk, "Design of 3-dB hybrid coupler based on RGW technology", IEEE Trans. Microw. Theory Techn., vol. 65, no. 10, pp. 3849-3855, Oct. 2017.
 
8. M. M. M. Ali, S. I. Shams, A. Sebak, "Ultra-wideband printed ridge gap waveguide hybrid directional coupler for millimetre wave applications", IET Microw. Antennas Propag., vol. 13, no. 8, pp. 1181-1187, Jul. 2019.
 
9. M. Farahani, M. Akbari, M. Nedil, T. A. Denidni, A. R. Sebak, "A novel low-loss millimeter-wave 3-dB 90° ridge-gap coupler using large aperture progressive phase compensation", IEEE Access, vol. 5, pp. 9610-9618, 2017.
 
10. F. Boccardi, R. W. Heath, A. Lozano, T. L. Marzetta, P. Popovski, "Five disruptive technology directions for 5G", IEEE Commun. Mag., vol. 52, no. 2, pp. 74-80, Feb. 2014.
 
11. A. Vosoogh, P. S. Kildal, V. Vassilev, " Wideband and high-gain corporate-fed gap waveguide slot array antenna with ETSI class II radiation pattern in V -band ", IEEE Trans. Antennas Propag., vol. 65, no. 4, pp. 1823-1831, Apr. 2017.
 
12. A. Vosoogh, P.-S. Kildal, "Corporate-fed planar 60-GHz slot array made of three unconnected metal layers using AMC pin surface for the gap waveguide", IEEE Antenna Wireless Propag. Lett., vol. 15, pp. 1935-1938, Dec. 2015.
 
13. D. Zarifi, A. Farahbakhsh, A. U. Zaman, P. S. Kildal, "Design and fabrication of a high-gain 60-GHz corrugated slot antenna array with ridge gap waveguide distribution layer", IEEE Trans. Antennas Propag., vol. 64, no. 7, pp. 2905-2913, Jul. 2016.
 
14. A. Polemi, S. Maci, P.-S. Kildal, "Dispersion characteristics of a metamaterial-based parallel-plate ridge gap waveguide realized by bed of nails", IEEE Trans. Antennas Propag., vol. 59, no. 3, pp. 904-913, Mar. 2011.
15. P.-S. Kildal, E. Alfonso, A. Valero-Nogueira, E. Rajo-Iglesias, "Local metamaterial-based waveguides in gaps between parallel metal plates", IEEE Antennas Wireless Propag. Lett., vol. 8, no. 4, pp. 84-87, Apr. 2009.
 
16. A. Polemi, S. Maci, "Closed form expressions for the modal dispersion equations and for the characteristic impedance of a metamaterial-based gap waveguide", IET Microw. Antennas Propag., vol. 4, no. 8, pp. 1073-1080, Aug. 2010.
 
17. A. T. Hassan, M. A. Moharram, A. A. Kishk, "Empirical analysis formulae of microstrip ridge gap waveguide", Proc. IEEE Int. Symp. Antennas Propag. USNC/URSI Nat. Radio Sci. Meeting, pp. 423-424, Jul. 2018.
 
18. M. M. M. Ali, S. I. Shams, A.-R. Sebak, "Printed ridge gap waveguide 3-dB coupler: Analysis and design procedure", IEEE Access, vol. 6, pp. 8501-8509, 2017.
 
19. A. Beltayib, I. Afifi, A.-R. Sebak, " \$4 times4\$ -element cavity slot antenna differentially-fed by odd mode ridge gap waveguide ", IEEE Access, vol. 7, pp. 48185-48195, 2019.

20. H. J. Riblet, "The short-slot hybrid junction", Proc. IRE, vol. 40, no. 2, pp. 180-184, Feb. 1952.
 Show Context View Article Full Text: PDF (3442KB) Google Scholar 
21. R. F. Harrington, Time-Harmonic Electromagnetic Fields, Hoboken, NJ, USA:Wiley, 2001.
 
22. R. Mongia, I. J. Bahl, P. Bhartia, RF and Microwave Coupled-line Circuits, Norwood, MA, USA:Artech House, 2007.
 
23. T. Oyedokun, R. Geschke, T. Stander, "A tunable Ka-band planar groove gap waveguide resonant cavity", Proc. IEEE Radio Antenna Days Indian Ocean (RADIO), pp. 1-2, Sep. 2017.
 
24. A. A. Brazález, A. U. Zaman, P.-S. Kildal, "Investigation of a microstrip-to-ridge gap waveguide transition by electromagnetic coupling", Proc. IEEE Int. Symp. Antennas Propag., pp. 1-2, Jul. 2012.
 
25. A. U. Zaman, T. Vukusic, M. Alexanderson, P.-S. Kildal, "Design of a simple transition from microstrip to ridge gap waveguide suited for MMIC and antenna integration", IEEE Antennas Wireless Propag. Lett., vol. 12, pp. 1558-1561, 2013.
 
26. A. Brazález, J. Flygare, J. Yang, V. Vassilev, M. Baquero-Escudero, P. Kildal, " Design of F -band transition from microstrip to ridge gap waveguide including Monte Carlo assembly tolerance analysis ", IEEE Trans. Microw. Theory Techn., vol. 64, no. 4, pp. 1245-1254, Apr. 2016.