@article{jiang_ortiz_mortazawi_2004, title={A Ka-band power amplifier based on the traveling-wave power-dividing/combining slotted-waveguide circuit}, volume={52}, ISSN={["1557-9670"]}, DOI={10.1109/TMTT.2003.822026}, abstractNote={An eight-device Ka-band solid-state power amplifier has been designed and fabricated using a traveling-wave power-dividing/combining technique. The low-profile slotted-waveguide structure employed in this design provides not only a high power-combining efficiency over a wide bandwidth, but also efficient heat sinking for the active devices. The measured maximum small-signal gain of the eight-device power amplifier is 19.4 dB at 34 GHz with a 3-dB bandwidth of 3.2 GHz (f/sub L/=31.8 GHz, f/sub H/=35 GHz). The measured maximum output power at 1-dB compression (P/sub out/ at 1 dB) from the power amplifier is 33 dBm (/spl sim/2 W) at 32.2 GHz, with a power-combining efficiency of 80%. Furthermore, performance degradation of this power amplifier due to device failures has also been simulated and measured.}, number={2}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Jiang, X and Ortiz, SC and Mortazawi, A}, year={2004}, month={Feb}, pages={633–639} }
 @article{jin_ortiz_mortazawi_2004, title={Design and performance of a new digital phase shifter at X-band}, volume={14}, ISSN={["1531-1309"]}, DOI={10.1109/LMWC.2004.832049}, abstractNote={A new digital phase shifter design at X-band is presented. The phase shifter operates based on converting a microstrip line to a rectangular waveguide and thus achieving the phase shift by changing the wave propagation constant through the medium. As a proof of principle, a 3-b phase shifter has been designed and constructed using PIN diode switches. An average insertion loss of 1.95 dB and phase shift error of less than 4/spl deg/ at 10.6 GHz are achieved.}, number={9}, journal={IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS}, author={Jin, Z and Ortiz, S and Mortazawi, A}, year={2004}, month={Sep}, pages={428–430} }
 @article{jiang_liu_ortiz_bashirullah_mortazawi_2003, title={A K a-band power amplifier based on a low-profile slotted-waveguide power-combining/dividing circuit}, volume={51}, ISSN={["1557-9670"]}, DOI={10.1109/TMTT.2002.806927}, abstractNote={In this paper, a Ka-band power amplifier based on a resonant slotted-waveguide-to-microstrip power-dividing/combining circuit is presented. The advantages of this structure are its low profile, ease of fabrication, as well as its potential for high power-combining efficiency. In addition, efficient heat sinking of monolithic microwave integrated circuit (MMIC) devices is achieved. A slotted-waveguide power amplifier using eight MMIC amplifiers was designed and fabricated. The measured power-combining efficiency at 33 GHz is 72%. In addition, simulation results predicting the performance degradation of the slotted-waveguide power amplifier due to multiple device failure are presented.}, number={1}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Jiang, X and Liu, L and Ortiz, SC and Bashirullah, R and Mortazawi, A}, year={2003}, month={Jan}, pages={144–147} }
 @article{ozkar_lazzi_mortazawi_2003, title={A modified unsplit PML formulation for evanescent mode absorption in waveguides}, volume={13}, ISSN={["1531-1309"]}, DOI={10.1109/LMWC.2003.814109}, abstractNote={In this letter, a modified unsplit perfectly matched layer (PML) formulation for the absorption of evanescent waves in waveguides is presented. The proposed formulation combines the advantages of the stretched coordinate and unsplit D - E - H PML formulations, which separates PML conductivities from the properties of the physical materials in the FDTD mesh. Results show that the proposed boundary outperforms the traditional unsplit PML in the evanescent region by 20 to 40 dB.}, number={6}, journal={IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS}, author={Ozkar, M and Lazzi, G and Mortazawi, A}, year={2003}, month={Jun}, pages={220–222} }
 @article{tombak_maria_ayguavives_jin_stauf_kingon_mortazawi_2003, title={Voltage-controlled RF filters employing thin-film barium-strontium-titanate tunable capacitors}, volume={51}, ISSN={["1557-9670"]}, DOI={10.1109/TMTT.2002.807822}, abstractNote={Tunable lowpass and bandpass lumped-element filters employing barium-strontium-titanate (BST)-based capacitors are presented. A new metallization technique is used, which improves the quality factor of the tunable BST capacitors by a factor of two. The lowpass filter has an insertion loss of 2 dB and a tunability of 40% (120-170 MHz) with the application of 0-9 V DC bias. The bandpass filter (BPF) has an insertion loss of 3 dB and a tunability of 57% (176-276 MHz) with the application of 0-6 V DC. The third-order intercept point of the BPF was measured to be 19 dBm with the application of two tones around 170 MHz.}, number={2}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Tombak, A and Maria, JP and Ayguavives, FT and Jin, Z and Stauf, GT and Kingon, AI and Mortazawi, A}, year={2003}, month={Feb}, pages={462–467} }
 @article{tombak_maria_ayguavives_jin_stauf_kingon_mortazawi_2002, title={Tunable barium strontium titanate thin film capacitors for RF and microwave applications}, volume={12}, ISSN={["1558-1764"]}, DOI={10.1109/7260.975716}, abstractNote={The measurement results for thin film barium strontium titanate (BST) based voltage tunable capacitors intended for RF applications are reported. At 9 V DC, BST capacitors fabricated using MOCVD (metalorganic chemical vapor deposition) method achieved 71% (3.4:1) tunability. The measured device quality factor (Q) for BST varactors is comparable with the device Q for commercially available varactor diodes of similar capacitance. The typical dielectric loss tangent was in the range 0.003-0.009 at VHF. Large signal measurement and modeling results for BST thin film capacitors are also presented.}, number={1}, journal={IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS}, author={Tombak, A and Maria, JP and Ayguavives, F and Jin, Z and Stauf, GT and Kingon, AI and Mortazawi, A}, year={2002}, month={Jan}, pages={3–5} }
 @article{ayguavives_jin_tombak_maria_mortazawi_kingon_2001, title={Contribution of dielectric and metallic losses in RF/microwave tunable varactors using (Ba,Sr)TiO3 thin films}, volume={39}, number={1-4}, journal={Integrated Ferroelectrics}, author={Ayguavives, F. and Jin, Z. and Tombak, A. and Maria, J. P. and Mortazawi, A. and Kingon, A. I.}, year={2001}, pages={1343–1352} }
 @article{stauf_ragaglia_roeder_vestyck_maria_ayguavives_kingon_mortazawi_tombak_2001, title={Thick electrodes for high frequency high Q tunable ferroelectric thin film varactors}, volume={39}, DOI={10.1080/10584580108011955}, abstractNote={Abstract Thin film barium strontium titanate (BST) shows great promise for voltage tunable dielectric devices for use at RF and microwave frequencies. An MOCVD process has been developed for production of BST, resulting in films with very low losses (as low as 0.002–0.004) and tunabilities over 50% at low operation voltages. With these values of BST loss, overall device quality factors at RF (100 MHz+) frequencies are primarily limited by losses in the thin metal electrodes, such as Pt, normally used for ferroelectric thin films. The bottom electrode in parallel plate capacitor structures is particularly challenging, since it must provide a good growth surface for BST and be stable at high (>600 °C) growth temperatures in an oxidizing atmosphere yet have high conductivity and compatibility with Si or SiO2/Si substrates. These challenges have previously prevented use of Pt thicknesses over 0.1–0.2 urn. Our solution to this problem, involves combinations of adhesion layers at the Pt/SiO2 interface and embedded stabilization layers to make functioning Pt bottom electrodes as thick as 2 μm. Devices with dielectric Q factors over 150 at 100 MHz (tan δ ∼ 0.006 as measured and modeled by S-parameters) and overall device Q factors over 50 at 30 MHz are described. We have also inserted these devices into tunable filters, achieving tunabilities of 50% and low insertion losses (0.3 dB) at RF frequencies.}, number={1-4}, journal={Integrated Ferroelectrics}, author={Stauf, G. T. and Ragaglia, C. and Roeder, J. F. and Vestyck, D. and Maria, J. P. and Ayguavives, T. and Kingon, A. and Mortazawi, A. and Tombak, A.}, year={2001}, pages={1271–1280} }
 @article{ortiz_ivanov_mortazawi_2000, title={A CPW-fed microstrip patch quasi-optical amplifier array}, volume={48}, ISSN={["0018-9480"]}, DOI={10.1109/22.821775}, abstractNote={A CPW fed microstrip patch quasi-optical power combining amplifier array is introduced. The amplifier array uses CPW fed patches for both input and output antennas. This structure is not only compatible with MMIC implementations but can also provide a greater bandwidth for the patch antennas. A 4/spl times/4 amplifier array was designed and fabricated at X-band. Theoretical and experimental results are presented.}, number={2}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Ortiz, SC and Ivanov, T and Mortazawi, A}, year={2000}, month={Feb}, pages={276–280} }
 @article{martin_mortazawi_2000, title={A Ka band extended resonance power amplifier}, volume={10}, ISSN={["1051-8207"]}, DOI={10.1109/75.888837}, abstractNote={A Ka-band power amplifier based on an extended resonance power combining technique is presented. This technique enables the design of planar microstrip power amplifiers that are much more compact than those based on traditional quarter-wave hybrid designs. The extended resonance power combining amplifier presented here combines four GaAs MESFETs at 32.8 GHz using a planar structure that is more than 40% smaller than a quarter-wave hybrid power combining amplifier design, while the power-combining efficiency is 92%. The measured small-signal gain at 32.8 GHz is 4.6 dB, and at 1-dB compression the output power is 23.3 dBm with a power-added efficiency of 12.8%.}, number={11}, journal={IEEE MICROWAVE AND GUIDED WAVE LETTERS}, author={Martin, AL and Mortazawi, A}, year={2000}, month={Nov}, pages={475–477} }
 @article{martin_mortazawi_2000, title={A class-E power amplifier based on an extended resonance technique}, volume={48}, number={1}, journal={IEEE Transactions on Microwave Theory and Techniques}, author={Martin, A. L. and Mortazawi, A.}, year={2000}, pages={93–97} }
 @article{martin_mortazawi_2000, title={A new lumped-elements power-combining amplifier based on an extended resonance technique}, volume={48}, ISSN={["1557-9670"]}, DOI={10.1109/22.869001}, abstractNote={A technique for combining power FETs in the output stage of a power amplifier is presented. The active devices are combined with simple inductor/capacitor networks and can be laid out across a single die while still allowing each device to be independently accessed for biasing. The inductors can range from fully integrated spirals to simple wire bonds, making this technique applicable over a broad range of frequencies. For linear RF power applications this is an effective technique for spreading more heat, while at high frequencies the junction parasitics are easily absorbed into this type of design. DC losses are minimized since each device can be biased individually, furthermore, it is possible to adjust the bias separately for each device to account for device nonuniformity across the die.}, number={9}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Martin, AL and Mortazawi, A}, year={2000}, month={Sep}, pages={1505–1515} }
 @article{bashirullah_mortazawi_2000, title={A slotted-waveguide power amplifier for spatial power-combining applications}, volume={48}, ISSN={["0018-9480"]}, DOI={10.1109/22.848497}, abstractNote={A power-amplifier array based on a slotted-waveguide power divider is presented for quasi-optical applications. The advantages of this structure are its low profile and ease of fabrication. Furthermore, efficient heat sinking of power devices is achieved. An X-band version of the power amplifier using eight MESFET's was designed and fabricated. An output power of 14 W was obtained. At 10 GHz, the amplifier gain and power-combining efficiency were 6.7 dB and 88%, respectively. The 3-dB bandwidth for the circuit was approximately 5%. This technique has the potential to meet the increasing demand for solid-state power amplifiers used in millimeter-wave communications and radar systems.}, number={7}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Bashirullah, R and Mortazawi, A}, year={2000}, month={Jul}, pages={1142–1147} }
 @article{yakovlev_ortiz_ozkar_mortazawi_steer_2000, title={A waveguide-based aperture-coupled patch amplifier array - Full-wave system analysis and experimental validation}, volume={48}, ISSN={["0018-9480"]}, DOI={10.1109/22.899032}, abstractNote={In this paper, the full-wave analysis and experimental verification of a waveguide-based aperture-coupled patch amplifier array are presented. The spatial power-combining amplifier array is modeled by the decomposition of the entire system into several electromagnetically coupled modules. This includes a method of moments integral equation formulation of the generalized scattering matrix (GSM) for an N-port waveguide-based patch-to-slot transition; a mode-matching analysis of the GSM for the receiving and transmitting rectangular waveguide tapers; and a finite-element analysis of the waveguide-to-microstrip line junctions. An overall response of the system is obtained by cascading GSMs of electromagnetic structures and the S-parameters of amplifier networks. Numerical and experimental results are presented for the single unit cell and 2/spl times/3 amplifier array operating at X-band. The results are shown for the rectangular aperture-coupled patch array, although the analysis is applicable to structures with arbitrarily shaped planar electric and magnetic surfaces.}, number={12}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Yakovlev, AB and Ortiz, S and Ozkar, M and Mortazawi, A and Steer, MB}, year={2000}, month={Dec}, pages={2692–2699} }
 @article{ozkar_mortazawi_2000, title={Analysis and design of an inhomogeneous transformer with hard wall waveguide sections}, volume={10}, ISSN={["1051-8207"]}, DOI={10.1109/75.843099}, abstractNote={A new inhomogeneous waveguide transformer with hard walls is presented. Mode matching technique along with an optimization routine is used to design the transformer. The generalized scattering matrix (GSM) of the whole block is calculated which can be used to predict the fields at the output given the incident excitations. An example of a three-section transformer, which replaces a tapered hard horn, is shown. The transformer has better performance in the bandwidth of interest compared to the tapered hard horn having twice the length of the transformer. This type of transformer could be useful for excitation of quasi-optical amplifiers and reflector feeds.}, number={2}, journal={IEEE MICROWAVE AND GUIDED WAVE LETTERS}, author={Ozkar, M and Mortazawi, A}, year={2000}, month={Feb}, pages={55–57} }
 @article{yakovlev_khalil_hicks_mortazawi_steer_2000, title={The generalized scattering matrix of closely spaced strip and slot layers in waveguide}, volume={48}, ISSN={["1557-9670"]}, DOI={10.1109/22.817481}, abstractNote={In this paper, a method-of-moments integral-equation formulation of a generalized scattering matrix (GSM) is presented for the full-wave analysis of interactive planar electric and magnetic discontinuities in waveguide. This was developed to efficiently handle a variety of waveguide-based strip-to-slot transitions, especially on thin substrates. This single matrix formulation replaces the problematic procedure of cascading individual GSM's of an electric (strip) layer, a thin substrate, and a magnetic (slot) layer.}, number={1}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Yakovlev, AB and Khalil, AI and Hicks, CW and Mortazawi, A and Steer, MB}, year={2000}, month={Jan}, pages={126–137} }
 @article{ali_ortiz_ivanov_mortazawi_1999, title={Analysis and measurement of hard-horn feeds for the excitation of quasi-optical amplifiers}, volume={47}, ISSN={["0018-9480"]}, DOI={10.1109/22.754882}, abstractNote={Measurement and analysis of hard horn feeds for excitation of quasi-optical amplifiers has been performed. A computer program based on the mode matching technique has been developed in order to determine the aperture field distribution for pyramidal hard horns. This program can be used to optimize a hard horn's field distribution and bandwidth. Simulation and measurement results for a 31 GHz hard horn feed are presented.}, number={4}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Ali, MA and Ortiz, SC and Ivanov, T and Mortazawi, A}, year={1999}, month={Apr}, pages={479–487} }
 @article{popovic_mortazawi_1998, title={Quasi-optical transmit/receive front ends}, volume={46}, ISSN={["1557-9670"]}, DOI={10.1109/22.734521}, abstractNote={Quasi-optical (QO) active circuits have originally received interest for power generation by large-scale power combining of solid-state devices at microwave and millimeter-wave frequencies. Here, we present an overview of QO components developed with functionality in mind, with an emphasis on bidirectional amplifier arrays for transmit/receive (T/R) front ends. We discuss possible advantages of the QO architecture for communications and radar. The following three QO bidirectional arrays are presented: 1) a nine-element X-band patch antenna array with different polarizations in T/R modes; 2) a 24-element X-band slot lens array with switches for the T/R paths; and 3) a 22-element K/spl alpha/-band patch lens array using monolithic microwave integrated circuits (MMICs).}, number={11}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Popovic, Z and Mortazawi, A}, year={1998}, month={Nov}, pages={1964–1975} }