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Design and development of wideband 3dB/90 couper using multiple-rows vias substrate integrated waveguide (SIW) technique
No full textMaster of Science in Communication EngineeringSubstrate Integrated Waveguide (SIW) technique is a good candidate when designing a
3dB/90° coupler at high frequency as this technique exhibits low loss compared to
traditional microstrip. In microstrip technique, some of the electric and magnetic field is
propagating in the air (lower permittivity compared to substrate), which contributes to
the loss of the signal. The loss in microstrip is more significant when operating at high
frequency. In contrast, a signal is travelling inside a substrate in SIW technique, guided
by metallic vias at both side of the transmission lines. This propagation is similar to the
waveguide propagation where no signal is propagating in the air. The possibility of
signal loss can be happened through leakage between vias which lead to the
performance degradation of the SIW coupler. The presented techniques to enhance the
performance of SIW coupler in open literature either has limited bandwidth, larger
dimension, or limited to simulated performance only. Therefore, the multiple-rows vias
to enhance the operational bandwidth (>20%) of SIW coupler for high frequency
applications is presented in this thesis. The proposed SIW coupler technique are
designed, analysed and validated at two different frequency ranges, Ku-Band (11-17
GHz) and K-Band (20-26 GHz). Both designs are implemented on Roger RO4003c
with thickness (h) of 0.508 and relative permittivity (ɛr) of 3.55. The proposed SIW
coupler design optimization is investigated using CST Microwave Studio simulation
tool. The investigation is started by sweeping different values of d (diameter of vias)
and p (pitch between vias). Through the parametric study analysis, the optimum value
of d and p to achieve the minimum insertion loss (S21, S31) is d=0.6 mm and p=0.92
mm, respectively. These optimized dimensions values are then applied in the next
parametric study of the SIW couplers where at this stage, additional rows with different
number of metallic vias are applied at the centre of both edge side of the coupler
structure. It is revealed that the best performance of the SIW coupler can be achieved
when 3 rows of metallic vias implemented at the centre of both edge side of the coupler
structure. By considering return loss and isolation better than 10 dB, coupling
coefficient of 3±1.5 dB and phase difference between output port of 90°±5°, the
simulated results show an improved operational bandwidth of 43.88% at Ku-Band and
26.31% at K-Band. The experimental results of the proposed SIW coupler are
accomplished using Agilent PNA-X 5245A PNA Network Analyzer where the
measured results agree well with the simulated results. In overall, the proposed method
for the SIW coupler features wide bandwidth with flat coupling response and better
return loss and isolation. Accordingly, it has good potential to be implemented in high
frequency application
Komunikasi kesihatan berkenaan COVID-19 melalui akaun Twitter Datuk Seri Ismail Sabri Yaakob
No full textLink to publisher's homepage at https://johdec.unimap.edu.my/Media sosial seperti Twitter dapat dijadikan sebagai satu medium yang berkesan dalam
menyampaikan komunikasi kesihatan dan menyebarkan maklumat mengenai pandemik
COVID-19. Kajian lepas menunjukkan bahawa keberkesanan media sosial seperti Twitter
dalam mengubah persepsi masyarakat memerlukan strategi yang jitu iaitu pemilihan corak
topik dan teknik komunikasi yang bersesuaian dengan khalayak sasaran. Namun begitu,
kajian mengenai corak topik, jenis komunikasi visual dan teknik komunikasi dalam
melakukan komunikasi kesihatan untuk menghadapi pandemik COVID-19 masih belum
banyak dikaji. Selain itu, terdapat juga beberapa kumpulan dalam masyarakat yang
biasanya menghadapi masalah untuk memahami maklumat mengenai risiko kesihatan.
Namun, dengan penggunaan gambar, video, grafik interaktif dan 3D, bahan-bahan ini
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