Comments on “Novel Broadband Artificial Magnetic Conductor With Hexagonal Unit Cell”

The above letter [1] stated that the planar artificial magnetic conductor (AMC) with square patch elements can be modeled by a distributed parallel LC network having one or more resonance frequencies. The resonant frequency is where the zero reflection phase or AMC condition occurs and the inphase reflection bandwidth is proportional to the square root of L/C. Therefore, more bandwidth can be obtained by reducing C, or increasing the gap between the patch elements. To prove the square patch element AMC bandwidth behaves just the opposite way, lets consider the AMC-PRS1 of Fig.5 in [1]. For a fair comparison of AMC bandwidth, the same dielectric as in [1], i.e. a Teflon substrate with thickness = 1.13 mm and dielectric constant = 2.2, is incorporated. By keeping the same period (4.5 mm) as in [1], while decreasing the gap dimension from 0.35 to 0.28 mm, Fig. 1 shows the full wave [2] simulated reflection phase results with the reflection bandwidth being increased from 11% (see Fig. 5 of [1]) to 29.3%. Note the resonant frequency is at 13.65 GHz where the curve crosses the zero phase line. Similar observation of increased AMC bandwidth with decreased gap between square patch elements is also demonstrated in Fig. 5 of [3].