Browsing by Subject "CPW"

Now showing 1 - 3 of 3

Open Access
Design of GaN-based coplanar multi-octave band medium power power MMIC amplifiers
(2013) Eren, Gülesin
Wideband amplifiers are employed in many applications such as military radar, electronic warfare and electronic instrumentations and systems, etc. This thesis project aims to build a wideband medium power monolithic microwave integrated circuits (MMIC) amplifier which operates between 6 and 18 GHz by using 0.25 µm Gallium Nitride (GaN) based high electron mobility transistor (HEMT) technology. Fully monolithic microwave integrated circuits realized with gallium nitride (GaN) high electron mobility transistors are preferred for designing and implementing microwave and millimeter wave power amplifiers due to its superior properties like high breakdown voltage, high current density, high thermal conductivity and high saturation current. Large band gap energy and high saturation velocity of AlGaN/GaN high electron mobility transistors (HEMTs) are more attractive features for high power applications in comparison to the conventional material used in industry for power applications- gallium arsenide (GaAs). Besides the high power capability of GaN enables us to make devices with relatively smaller sizes than of GaAs based devices for the same output power. Device impedances in GaN technology are higher than the GaAs technology which makes broadband matching easier. Firstly, GaN material properties are overviewed by mentioning the design and characterization process of the AlGaN/GaN epitaxial layers grown by Bilkent NANOTAM. After the microfabrication process carried out by Bilkent NANOTAM is explained step by step. It is followed by characterization of the fabricated HEMTs. As a final step before going through the design phase, the small signal and large signal modeling considerations for GaN based HEMTs are presented. In the last part, designs of three different multi-octave MMIC amplifier realized with coplanar waveguide (CPW) elements are discussed. In order to extend the bandwidth and to obtain a flat gain response, two different design approaches are followed, the first one is realized with Chebyshev impedance matching technique without feedback circuit (CMwoFB) and the other one is utilized by Chebyshev Impedance matching technique with negative shunt feedback (CMwFB), respectively. To maximize the output power, two transistors in parallel (PT) are used by introducing Chebyshev matching circuit and negative feedback circuit. The design topology which consists of two parallel transistors (PT) is modified to fulfill all the design requirements and it is implemented by taking process variations and the previously obtained measurement results into account. The measurement and the simulation results match each other very well, the small signal gain is 7.9 ± 0.9 dB and the saturation output power in the bandwidth is higher than 27 dBm in this second iteration.
Open Access
X-band CPW high power amplifier design by GAN based MMIC technology
(2016-06) Yılmaz, Burak Alptuğ
The developments in defense industry, telecommunication and satellite systems have gradually increased the necessities for the small and compact Power Ampli- fiers (PAs) with high output powers and gains. Monolithic Microwave Integrated Circuits (MMICs), that are fabricated by using Gallium Nitride (GaN) on Silicon Carbide (SiC) substrate, achieve the system requirements. GaN based MMIC technology gives chance to produce high power capable and compact PAs. Moreover, suitable Wilkinson Power Dividers (WPDs) with low Insertion Loss (IL) assist in transferring output power of the device with combining MMIC PAs. Presented designs in this thesis work have been fabricated in Bilkent University NANOTAM with GaN on SiC process. Fabricated X-band Coplanar Waveguide (CPW) PA works from 7.9 GHz to 8.4 GHz as intended and its efficiency equals to 40 % at 8.4 GHz under 2.1 dB compression. Measurements of fabricated PA show that output power of the device is equal to 37.8 dBm under 2.1 dB compression and it has 9.8 dB minimum gain in the operating band. Furthermore, equal, three-way WPD device was designed and fabricated with the same process and it works at wide-band range with approximately 0.9 dB IL. It is advantageous that the total dimension of paralleled MMIC PAs can be adjusted by scaling branches of the designed WPD with the aim of performance optimization.
Open Access
X-band low phase noise mmic vco & high power mmic spdt design
(2014) Osmanoğlu, Sinan
Generally the tuning bandwidth (BW) of a VCO is smaller than the tuning BW of the resonant circuit itself. Using proper components with right topology can handle this problem. In order to overcome this problem and improve the tuning BW of the VCO, common-base inductive feedback topology with Gallium Arsenide (GaAs) Heterojunction Bipolar Transistor (HBT) is used and an optimized topology for tank circuit is selected to minimize the effect of bandwidth limiting components. Designed VCO with this topology achived -117 dBc/Hz at 1 MHz offset phase noise with 9-13 dBm output power between 8.8-11.4 GHz band. Second part of the thesis composed of Single Pole Double Throw (SPDT) RF Switch design. From mesa resistors to SPDT fabrication, everything is fabricated using Bilkent University NANOTAM Gallium Nitride (GaN) on Silicon Carbide (SiC) process. Switching HEMTs are fabricated to generate a model to design SPDTs and the final design works between DC-12 GHz with less than 1.4 dB insertion loss (IL), -20 dB isolation and 14.5 dB return loss (RL) at worst case. The power handling of the switches are better than 40 dBm at output with 0.2 dB compression, which is measured with continuous wave (CW) signal at 10 GHz.