Development of broadband forward-wave directional couplers loaded by periodic patterned ground structure

Abstract

In this paper two wideband Forward‐Wave Directional Couplers (FWDCs) with 0 dB and 3 dB coupling level are proposed. Using periodic patterned ground structure in a microstrip coupled lines by a new unit cell; even‐ and odd‐mode characteristic impedances of the couplers are equal over a wide frequency range. Moreover, it provides a constant phase difference between even and odd‐modes. The proposed cell is modeled using the equivalent circuit model and a design procedure is introduced for designing FWDCs for an arbitrary value of coupling level. The introduced couplers are numerically investigated and a prototype of both couplers is made. It is shown that for 0 dB coupling level, the measured coupling is 0.85 dB with 1 dB flatness over fractional bandwidth of 96% bandwidth. In case of 3 dB coupling, the measured coupling level is 3.5 dB at 7.42 GHz with 1 dB flatness over fractional bandwidth of 67.1%.

Wideband directional coupler based on zigzag coupling and wedge structure for isolation enhancement

“…In terms of achieved isolations, Reference 14 provides similar performance over a very wide bandwidth, but a multilayer based process is required. Using a patterned ground, Reference 21 also reports a directional coupler with an octave bandwidth under an isolation response of 15 dB, where the patterned ground also features multilayer processes. In this contribution, the developed coupler presents simple and planar layout, symmetric topology, symmetric coupling and isolation responses (this is the basic difference among many reported works), wide operation bandwidth with a pure planar transmission line technology and more importantly, the wedge structure can be independently designed, as compared with the capacitance and inductance compensations presented in References 5–11.…”

“…Based on the patterned ground that is achieved by destroying an integral ground with some patterns, studies show it can also be utilized to design a directional coupler with enhanced performance. 20,21 On the other hand, by folding the coupled line in the coupling region, results indicate the tight-coupled coupler with high directivity can be developed, as studied by Zheng et al 22,23 For a directional coupler with enhanced performance, other techniques include the use of fragment coupling, 24,25 the substrate integrated waveguide (SIW), 26 and by combining the branch line with coupled line. 27,28 With the increasing demand for microwave components with stringent requirements, there is the need for the continuous improvement in the design and performance of the basic components.…”

“…Based on the patterned ground that is achieved by destroying an integral ground with some patterns, studies show it can also be utilized to design a directional coupler with enhanced performance 20,21 . On the other hand, by folding the coupled line in the coupling region, results indicate the tight‐coupled coupler with high directivity can be developed, as studied by Zheng et al 22,23 …”

Development of a New Backward Directional Coupler Based on Perforated Substrates

“…Tabatabaeian et al [13] designed a forward-wave directional coupler using periodic patterned ground structure in microstrip coupled lines with a 96% bandwidth, while the coupling flatness is 1 dB and return loss is not better than 10 dB. Tabatabaeian et al [14] proposed a directional coupler using periodic shunt shortcircuited stubs.…”