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Pada penelitian ini, peningkat performansi antena mikrostrip MIMO dilakukan dengan menggunakan efek mutual coupling, maka dengan pencacatan bidang groundplane, atau yang biasa disebut dengan metode defected ground structure (DGS). Bentuk DGS yang digunakan adalah U-shape dan terbukti dapat mengurangi efek mutual coupling pada antena MIMO mencapai -22,833 dB dibandingkan dengan antena konvensional. Dengan menggunakan hingga 2 periodik, U-shape juga berhasil diperoleh pengurangan dimensi antena mencapai 29,89% dibandingkan dengan dimensi antena MIMO konvensional. Hal ini tentunya terbukti membuat metode DGS sesuai untuk digunakan pada antena dengan dimensi yang kecil dan mutual coupling yang baik pada massive MIMO pada aplikasi di perangkat portable. Kata Kunci: defected ground structure (DGS); antena mikrostrip; U-shape; mutual coupling

Antenna miniaturization has become one important research, especially in mobile communication technology development. This paper presents the development of a miniaturized antenna for RFID application (924 MHz). Meandering technique has been adopted to create a geometrically small antenna relative to its operating frequency. Measurement result shows that the fabricated antenna inherits low return loss, down to -25.915 dB. The geometry of the antenna is 25.54 mm x 16 mm, which is much smaller than its resonance wavelength (0.079? x 0.049?). The measured gain is relatively small, of about -12 dBi. Nevertheless, the obtained parameters are acceptable since the antenna is meant for near field communication application.

Annular ring antenna concept has been utilized in many applications. This paper presents the adoption of annular ring concept on a dual-band microstrip antenna. The antenna is designed to operate at 1.9 GHz and 2.1 GHz operating frequencies. The objective of this research is to observe the method potential of combining two patches operate at different frequencies as a single dual-band antenna. While the purpose of the annular concept is to enhance the bandwidth of an antenna, analysis from this work shows that for a dual-band antenna with operating frequencies close one to the other, the obtained bandwidths are relatively narrow, down to of about 5%. Nevertheless, the antenna is capable to operate at both designated frequencies with good return losses down to -24.40dB.

Filter is one of key module in a radio telescope system. This article present the development of VHF LC-passive filters meant to support a multiband antenna in a transient radio telescope system by reducing the bandwidth of each operating frequencies. The filters were developed by employing low-cost inductor and capacitor with low self-resonant frequency (SRF) an hence the characteristic are highly affected by the parasitic inductance of the capacitors an parasitic capacitance of the inductors. Therefore, general equation to develop an LC filters was no longer applicable in developing these filters. Nevertheless, three filters were successfully developed, operated at 38 MHz, 74 MHz and 152 MHz with relatively good quality factors up to of about 13.