RESUMO
An improved mutual coupling compensation in circularly polarized (CP) multi-input multi-output (MIMO) dielectric resonator antenna (DRA) is presented in this paper. Using trimming approach, the mutual coupling (MC) between closely spaced DRA units at 0.3λ has been significantly reduced while axial ratio performance has been maintained. Mutual coupling reduction is obtained by trimming the DRA to ensure low mutual coupling below -20dB. The exclusive features of the proposed MIMO DRA include wide impedance matching bandwidth (BW), triple band circular polarization, and suppressed MC between the radiating elements. The impedance bandwidth matches perfectly with a triple band's 3 dB axial ratio (AR). It is designed with characteristic mode analysis with good agreement of the measurement that has been obtained. Using the probe feed method, the DRA and patch strip are coupled together to allow bandwidth widening of the pro-posed DRA. An impedance bandwidth of 34% at a lower frequency to around 2% at a higher frequency was achieved in all resonance frequencies. Thus, we refer to our newly designed DRA as a proposed method for effectively reducing the mutual coupling between DRAs. Additionally, the 3 dB AR bandwidth matched at 3.3 GHz, 4.6 GHz, and 6.3 GHz with a percentage of 11.66%, 3.04%, and 2.22% obtained at the three different frequencies. Note that the proposed DRA exhibits low mutual coupling (below -20 dB) at the targeted frequencies, which is suitable for better signal reception for MIMO applications. By computing, the metrics envelop correlation coefficient, diversity gain, channel capacity loss, and total active reflection coefficient, the MIMO performance of the proposed antenna is verified. The experiments show a close result between simulated and computed validation of the proposed DRA.
RESUMO
OBJECTIVE: In Malaysia, optometrists' role in the private sector is limited compared to their counterparts elsewhere. Primary eye care (PEC) is still not widely offered in private practises despite its demand to reduce the public's eye morbidity. This study aims to explore the challenges perceived by the private sector optometrists in implementing PEC in Malaysia. MATERIALS AND METHODS: In-depth interview using semistructured open-ended questions were designed to explore the challenges of implementing PEC. Fifteen private optometrists across Malaysian were interviewed via purposive sampling until the data were saturated. The interviews were audio-recorded, transcribed and analysed. RESULTS: Four major themes emerged: working environment, support and recognition, self-sufficiency and customer influence. The first major theme identified a lack of time and equipment in the workplace as a barrier to PEC implementation. The second major theme acknowledges the lack of support and recognition for PEC practise from financial bodies, the government, Malaysian Optical Council (MOC) and other eye professionals. Meanwhile, some practising optometrists faced significant challenges due to their lack of self-sufficiency regarding skills, knowledge and confidence. The final major theme, customer influence, reflects the customer's role in shaping eye care delivery through their perception and acceptance of PEC. CONCLUSION: Each of the issues identified played a significant impact in impeding PEC implementation in Malaysia. This study is the first step toward developing tailored interventions to improve eye care delivery in Malaysia.
