A directivity-enhancement technique is demonstrated for a microstrip directional coupler. By loading the coupler with shunt inductors, the phase velocities of the even and odd modes are altered in such a way that an isolation null is achieved. Compared with other compensation techniques for directivity enhancements, the proposed method provides the advantages of being simple yet easily application to high frequencies. For a 10 dB directional coupler at 0.9 GHz, a maximum directivity improvement of nearly 38 dB is measured over the conventional counterpart.
Bibliographical noteFunding Information:
Manuscript received January 06, 2009; revised March 04, 2009. First published May 26, 2009; current version published June 05, 2009. This work was supported by the Defense Acquisition Program Administration and by the Agency for Defense Development of Korea, under Contracts 5ND0600407, UD-070054–AD, and UD-080040–GD.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Electrical and Electronic Engineering