A Wideband Doherty Combiner with Phase Variation Compensation Using LTCC Applicable for High Power Transmission

In this paper, we propose a small-sized Doherty combiner with phase variation compensation using low temperature co-fired ceramic (LTCC) substrate. The proposed design theory for the Doherty combiner is derived using the phase calculation of the S-parameter based on the relation between the input and output ports. The proposed circuit is designed after determining the band edge frequency and the targeted degree of the phase balance. The proposed circuit is verified using the microstrip line and the LTCC substrate. The implemented structure, using LTCC as the substrate, is operated under a high-power test of continuous wave 50 W, the results of which also show that the amplitude and phase balance have variations within 0.2 dB and ±1°, respectively. The high-power test shows that the implemented structure is applicable for high power Doherty amplifiers or combiners

A New Doherty Combiner with Wide Bandwidth for Magnitude and Phase Balance Compensation

This paper proposes a novel Doherty combiner that uses a series and parallel resonant circuit for wideband. Unlike conventional combiners, the aim of the proposed combiners is to extend bandwidth for not only the magnitude bandwidth, but also phase balance by employing series and parallel resonant circuits at the output impedance of the peaking amplifier. Considering the load impedance of the peaking amplifier, the Doherty combiners were analyzed in the theory of this study by deriving the series and parallel resonant circuit values. The output phase balances are determined for the targeted bandwidth to achieve uniform phase balance in the proposed combiner I using a series resonator. For better magnitude bandwidth, the slope of reflection coefficient (Γ) at port 3 in the combiner II using series resonator was derived using the derivative of Γ with respect to ω. Experimental results show that the proposed combiner I has 63.5% magnitude fractional bandwidth (FBW) and 118% FBW with the phase balance at ±2.5°. The proposed combiner II also has 85% magnitude FBW and 118% FBW with the phase balance at ±2.5°

Understanding the Lirico-Spinto Soprano Voice through the Repertoire of Giovane Scuola Composers

As lirico-spinto soprano commonly indicates a soprano with a heavier voice than lyric soprano and a lighter voice than dramatic soprano, there are many problems in the assessment of the voice type. Lirico-spinto soprano is characterized differently by various scholars and sources offer contrasting and insufficient definitions. It is commonly understood as a pushed voice, as many interpret spingere as ‘to push.' This dissertation shows that the meaning of spingere does not mean pushed in this context, but extended, thus making the voice type a hybrid of lyric soprano voice type that has qualities of extended temperament, timbre, color, and volume. This dissertation indicates that the lack of published anthologies on lirico-spinto soprano arias is a significant reason for the insufficient understanding of the lirico-spinto soprano voice. The post-Verdi Italian group of composers, giovane scuola, composed operas that required lirico-spinto soprano voices. These giovane scuola composers include Alfredo Catalani (1854 –1893), Umberto Giordano (1867 –1948), Pietro Mascagni (1863 –1945), Giacomo Puccini (1858 –1924), and Riccardo Zandonai (1883 –1944). Descriptions of the soprano voices that premiered these roles are included in this document to determine the suitability of the lirico-spinto soprano voice for each role

Doctoral Recitals

Recital presented at the UNT College of Music Voertman Hall in partial fulfillment of the Doctor of Musical Arts (DMA) degree

Doctoral Recitals

Recital presented at the UNT College of Music Voertman Hall in partial fulfillment of the Doctor of Musical Arts (DMA) degree

Doctoral Recitals

Recital presented at the UNT College of Music Voertman Hall in partial fulfillment of the Doctor of Musical Arts (DMA) degree

Novel Wilkinson Power Divider with an Isolation Resistor on a Defected Ground Structure with Improved Isolation

A modified Wilkinson Power Divider is proposed in this paper that utilizes defected ground structure (DGS) in parallel with an isolation resistor. The proposed DGS section is incorporated between the output ports, and the isolation resistor is soldered in parallel with the DGS in the ground plane, instead of on the top plane as in a conventional Wilkinson power divider, to achieve improved or preferable isolation. The proposed design is comprised of two pairs of microstrip transmission lines with equal impedances and varied electrical lengths. The parameters of the main circuit and the DGS section are acquired separately. The parameters of the proposed main circuit are derived by applying conjugate matching theory. Dumbbell-shaped DGS is introduced in the ground plane between the output ports, which acts as a parallel resonator, yielding an attenuation pole at the resonant frequency that contributes to improved isolation. By applying the previous well-known circuit theory, the lumped elements of the equivalent circuit of the DGS were achieved. The physical dimensions of the equivalent circuit for the DGS section were obtained by three-dimensional EM simulation. The measured results show improved isolation, return loss and better bandwidth as compared with other similar works. Furthermore, the proposed circuits designed at resonating frequencies of 3 and 2 GHz presented comparatively good return losses, S11 of about −25.54 and −31.24 dB, respectively, and achieved improved isolations, S32 between the output ports, in an order of about −40.83 and −36.05 dB, respectively, which is rather exceptional and desirable