Browsing by Subject "Sheet resistance"

Now showing 1 - 3 of 3

Open Access
Accurate and process-tolerant resistive load
(IEEE, 2020) Sütbaş, Batuhan; Özbay, Ekmel; Atalar, Abdullah
Resistive terminations cannot preserve high-quality matching at high frequencies due to the parasitic effects of the nonideal resistor. Moreover, resistance values of the termination resistors in integrated circuits are subject to process variations. Therefore, it is difficult to obtain accurate and process-tolerant terminations that are crucial for high performance in microwave circuits. We propose a new resistive network that compensates for the high-frequency parasitic effects of the resistors to improve the bandwidth of the termination. In addition to maintaining accuracy, the presented network provides tolerance to variation in the resistor values. The accuracy and tolerance of the proposed structure is analytically shown and experimentally verified by three test structures at the X-band fabricated on a GaN technology. The experimental results show that a small size and wideband 50-Ω load with a return loss better than 25 dB can be obtained, while the resistor value changes ±30%.
Open Access
Accurate isolation networks in quadrature couplers and power dividers
(IEEE, 2021) Sütbaş, Batuhan; Özbay, Ekmel; Atalar, Abdullah
When quadrature couplers and power dividers are implemented in integrated circuits, accurate isolation networks can not be realized due to the nonideal resistors and the process variations. We present an isolation network design technique which cancels the resistor parasitic effects and also increases the tolerance to variations in the resistance values. A Lange coupler and a power divider are designed at Ka-band using the proposed accurate and process-tolerant isolation networks. The improvement is analytically shown and empirically verified with our in-house GaN-based microstrip MMIC process. For the coupler, the measured return losses and isolation are better than 20 dB from DC to 40 GHz. The power divider achieves 20 dB return losses and isolation in a fractional bandwidth of 50%. Both devices maintain 20 dB performance even when the variation in sheet resistance is as high as 30%.
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.