Browsing by Subject "Microstrip"

Now showing 1 - 3 of 3

Open Access
Choices of expansion and testing functions for the method of moments applied to a class of electromagnetic problems
(IEEE, 1993-03) Aksun, M. I.; Mittra, R.
It is well known that the choice of expansion and testing functions plays an important role in determining the rate of convergence of the integrals associated with the moment method matrix, and that an improper choice can lead to erroneous results. The main objective of this paper is to critically examine this convergence issue and to provide criteria for the choice of these expansion and testing functions. The question of whether these functions need to satisfy the Holder condition is also investigated and the convergence behavior of the integrals involved in the spatial and spectral domain moment method is discussed for some representative expansion and testing functions.
Open Access
Improved Wilkinson power divider structures for millimeter-wave applications
(2019-01) Sütbaş, Batuhan
Communication systems, radars, electronic warfare and space applications desire integrated circuits with higher operating frequencies. Working at the millimeter-wave region increases data rates, provides a more efficient use of the spectrum and enables smaller products. Power dividers are used as building blocks for such applications to split and combine RF signals. Wilkinson power divider is one of the most commonly used topology, providing high return loss and isolation with low insertion loss. However, it occupies valuable chip area, has a limited bandwidth, requires accurate modeling and precise fabrication. In addition, the layout becomes complicated for three or more outputs and cannot be realized on a planar circuit. This work presents three techniques to address the drawbacks of the original Wilkinson divider. The first structure achieves a compact size without bandwidth degradation and provides additional physical isolation at the output. The second divider improves the bandwidth of operation and increases tolerance to sheet resistance variance, enabling robustness and higher yields. The third technique simplifies the layout of three-way dividers and allows a planar fabrication technology. The proposed structures are analyzed using even-odd mode analysis and design equations are derived. Three high performance dividers with 30 GHz center frequency are designed employing the developed methods. The circuits are realized using GaN based coplanar waveguide and microstrip monolithic microwave integrated circuit technology. Experimental results demonstrate good agreement with theory and simulations, proving that the presented improvements could be useful in future millimeter-wave RF applications.
Open Access
S-band GaN high power amplifier design and implementation
(2019-02) Kavuştu, Muhammet
High power RF Microwave amplifiers are becoming more important as the telecommunications, defense and aerospace industries' demands develop. GaN on SiC technology offers higher power and better form factors for these applications compared to GaAs. In addition, SiC provides better mechanical properties and thermal performance. Design, manufacturing and measurements of a S-Band Power Amplifier by using a GaN discrete bare die transistor are presented. GaN on SiC technology, fabrication process, amplifier fundamentals and design steps are explained in detail. PCB laminate properties, manufacturing, wire bonding and importance of heat management are explained. Design, tapeout, characterization of a fabricated HEMT and its packaging are also mentioned. Power amplifier's small-signal gain of 14.5 dB is measured at center frequency. 41.5 dBm RF power at P6dB is measured at 200 μs pulse width 10% duty cycle at 3 GHz, reaching a power density of 5:4W=mm. Small-signal gain, IP3 measurements under different biases, AMAM and AM-PM distortions are also investigated in detail. EM simulations are performed in Keysight ADS design environment. Amplifier design is based on small-signal and loadpull measurements. De-embedding of fixture effects during HEMT characterization and their models are also investigated. Another hybrid amplifier design by using a packaged commercial GaN on SiC bare die power HEMT is also presented. Small-signal and power measurements are also offered.