Directional coupler with high directivity using metallic cylinders on microstrip line

High Directivity Microstrip Coupler Using Variable Width Structure

“…Delay lines [8] were used, but the coupler occupies more space than the conventional one. The Re-entrant mode structure [9], periodic metallic cylinders [10], and metamaterial [11] were also reported to improve the isolation, where the coupler construction is complex. Periodic floating conductors [12] were used to improve the directivity for a wide bandwidth for a maximum directivity of 30 dB.…”

High Directivity Microstrip Coupler with Asymmetric Structure

“…Delay lines [8] were used, but the coupler occupies more space than the conventional one. The reentrant mode structure [9], periodic metallic cyl inders [10], and metamaterial [11] were also reported to improve the directivity, where the coupler construction is complex. Periodic floating conductors [12] were used to improve the directivity for a wide bandwidth, for a maximum directivity of 30 dB only.…”

“…The advantages of the coupler are, that the structure is planar, there is no special fabrica tion technique needed, no vias are used, and the con struction is simpler when compared to other methods [7,[9][10][11], and it does not require any iteration design process [3,4].…”

A Directivity-Enhanced Directional Coupler Using Epsilon Negative Transmission Line

“…Some of these methods are not easy to fabricate [10]- [12], [17], [18] and some of them do not have closed-form design equations [11]- [14]. The lumped-element compensation method leads to broad directivity bandwidth, but the parasitic effects of lumped elements affect the coupler performance at high frequencies [2]- [7].…”