Wideband reconfigurable antennas

The work described in this thesis concerns the combining of wideband and reconfigurable narrow band functionality into a single antenna. This concept may be useful in reducing size and to give flexibility to a wireless terminal to operate in several different modes. The approach also offers additional pre-filtering to the front-end, which reduces the interference levels at the receiver, giving them a significant advantage over fixed non reconfigurable transceivers. Wideband-narrowband reconfiguration is potentially useful for future wireless communications such as software defined radio and cognitive radio, since they may employ wideband sensing and reconfigurable narrowband communications. Five novel reconfigurable antennas are presented. One is a switchable log periodic patch array and four are Vivaldi antennas with various forms of reconfiguration. The log periodic is reconfigured by placing switches between the patches and the feed line whilst the Vivaldi antenna has switched resonators controlling the current in the edges of the tapered slots. Wideband to various narrowband functions, wideband with a tunable band rejection having a very wide tuning ratio, and combined three function wide, narrow and tunable band rejection in a single antenna are demonstrated. Prototypes are presented with PIN diode switches, varactors, fixed capacitor or hard wire switches. Measured and simulated results with a very good agreement are presented, thus verifying the proposed concepts.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Switchable filtering in vivaldi antenna

Presented is a new frequency switchable Vivaldi antenna that has a capability to operate in a wideband mode (1-3 GHz) and reconfigure to six different subbands of operations. The reconfiguration is realised by coupling and changing the effective electrical length of ring slots inserted in the structure by means of pin diode switches. To examine antenna performances, simulated and measured results are presented. Good impedance matches and radiation patterns have been achieved. The proposed antenna is suitable for wideband and multimode radio applications

Switched-band vivaldi antenna

A novel Vivaldi antenna with added switched band functionality to operate in a wideband or narrowband mode is presented. The antenna reconfiguration is realized by inserting four pairs of switchable ring slots into the ground plane of the structure. A wide bandwidth mode from 1.0-3.2 GHz and three narrowband modes can be selected. A fully functional prototype with PIN diodes switches has been developed. Measured results shows good performance of the proposed designs. The antenna could be a suitable solution for a multimode application requiring wideband and frequency reconfigurable antennas, such as in military applications and cognitive radio

Multiband CPW-fed slot antenna for WLAN/WiMAX applications

A square slot antenna fed by a coplanar waveguide (CPW) is presented in this paper. The design consist of two pairs of “F” shaped planar strips placed within a square slotted ground. The strips are used to excite multiple resonant frequencies, the strips are connected to the ground plane by means of ideal switches. The proposed antenna has achieved multiple resonant frequencies of 2.4/5.2/5.8 GHz for WLAN and 3.5/5.5 for WiMAX applications. The measured results shows a good agreement with the simulated results in terms of return loss, radiation pattern and gain. The proposed antenna is designed for the frequency range of 2 GHz to 7 GHz which makes it suitable for Bluetooth, WLAN and WiMAX applications

Band-pass Filter with Harmonics Suppression Capability

This paper presents a Band-pass Filter (BPF) with a very wide suppressions band. The filter design is based on a modified U-shaped slot. Two pair of U-shaped slots is used to ensure that the filter can suppress the unwanted frequencies up to 4th harmonics. In order to achieve sharp skirt, two transmission zeroes are created near the passband area. Additional transmission zeroes are introduced to deepen the stopband area. Therefore, the passband range starts from 1.3 to 3.3 GHz and the stopband range from 3.3 GHz up to 9 GHz are achieved. The filter performances are verified through simulated and measured results

Compact wideband frequency reconfigurable metamaterial antenna design

This paper presents the design of compact wideband frequency reconfigurable metamaterial (MTM) antenna. The design is based on the idea of obtaining single and multi-bands in wideband metamaterial antenna within the range of bandwidth. This is achieved by introducing capacitive slots which neutralize inductive properties and generate left handed capacitive parameter. The three series slots in the patch contribute for bandwidth enhancement while two PIN Diode Switches provide multi-bands operation. Computer Simulation Technology (CST) software is used to determine the operation and effectiveness of the proposed antenna. The approach has several notable merits which include improvement of spectrum utilization, minimize spectrum congestion, interference and provide bands selectivity. From the simulation results, it was found that, bandwidth was improved to 2.8 GHz which is equivalent to 82% fractional bandwidth. Also, it can switch to seven different frequency bands of operation with only two number of switches. The realized peak gain is 2.44 dBi and 3.15 dBi at 2.4 GHz and 5.0 GHz respectively with average efficiency of 95%. The antenna can be utilized for wireless communication and cognitive radio application

Circular polarization folded reflectarray antenna for 5G applications

Fifth-generation (5G) is a wireless connection built specifically to keep up with the rapid increase of devices that need a mobile internet connection. A system working on 5G band can provide higher bandwidth and faster data rate as compared to fourth-generation (4G) band. Thus, an antenna with higher gain and lower profile is required to support this system. On the other hand, the performance of circular polarization antenna is better than linear polarization antenna due to its ability to accept wave from different direction. In this project, a low profile circular polarization folded reflectarray antenna with operating frequency of 28 GHz is presented. This project is divided into two parts. In the first part, a linear polarization folded reflectarray antenna is designed. In this second part, a meander lines polarizer is used to convert the linear polarization antenna to circular polarization antenna. The antenna is fed by a linear polarized waveguide. Each radiating element of the antenna is in rectangular shape. The size of the radiating elements are selected according to obtain required phase delay to form a planar phase front in the far-field distance. Both of the antennas are simulated by using Computer Simulation Technology (CST) software. Finally, the results shows excellent performances with 16.81dB directivity and 1.49dB axial ratio at 28GHz. Thus, the antenna is very suitable for 5G applications

Prinsip kejuruteraan telekomunikasi

Telekomunikasi ialah proses penyampaian maklumat untuk jarak yang jauh, melebihi jarak yang boleh dicapai oleh suara manusia. Sejarah membuktikan manusia asalnya menyalurkan maklumat untuk jarak jauh melalui pelbagai kaedah primitif seperti menggunakan asap, bunyi atau surat sebagai perantara. Era sistem telekomunikasi moden tercetus apabila terciptanya telefon dan berkembang sehingga kepada komunikasi melalui internet. Sehubungan itu, buku ini meneroka prinsip asas sistem telekomunikasi yang merangkumi pemodulatan analog, digit dan kekunci. Konsep asas pemodulatan analog meliputi pemodulatan amplitud dan sudut, analisis isyarat dalam domain masa dan frekuensi, operasi litar penjana dan penerima, dan kesan hingar ke atas sistem pemodulatan. Perbincangan mengenai pemodulatan digit pula mencakupi teknik penukaran isyarat analog kepada digit seperti pemodulatan delta dan pemodulatan kod denyut yang melibatkan proses pensampelan, pengkuantuman dan pengekodan talian. Kaedah pemultipleksan dan pemodulatan kekunci isyarat digit turut disertakan untuk melengkapkan pengetahuan asas kejuruteraan telekomunikasi. Buku ini juga mengandungi contoh dan latihan di akhir setiap bab yang dapat membantu mengukuhkan kefahaman pembaca di samping mampu menjadi bahan rujukan bidang berkaitan

Wideband Frequency Selective Surface Based Transmitarray Antenna at X-Band

In this paper, a wideband multilayer transmitarray antenna is designed for Ku frequency band. The unit cell is designed at 12GHz using frequency selective surface structure. Double square ring with center patch based multilayer unit cell is simulated. The effect of substrate thickness variation on transmission coefficient magnitude and phase range is discussed. The horn antenna designed at X-band will be used as feed source for transmitarray antenna. Transmitarray simulation results show wide impedance bandwidth from 10 to 13GHz. Wide gain bandwidth of 1.975GHz with peak gain of 18.96dB is achieved. The proposed transmitarray design will find applications in high gain, directional, low profile antennas for X-band communication systems

X-band rectangular to square waveguide transition for transmitarray unit cell characterization

In this paper, a characterization setup for transmitarray unit cell analysis is designed in CST studio using rectangular to square waveguide transition for X-band applications. A wideband transmitarray unit cell is designed using split ring resonator and unit cell simulations show wide impedance matching bandwidth of 43.7%. In this simulation, the waveguide transition length is varied to reduce the reflection coefficient magnitudes below -20dB. Then, the square cross section area of waveguide is made variable and cutoff frequency variation over 4GHz is illustrated. Finally, the model for real time test setup is simulated along with the transmitarray unit cell and the results show high transmission magnitude of -O.23dB. This setup can also be used for other frequency selective surface unit cells characterization