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Abstract-An active balun using current steering for phase correction is presented. The proposed active balun is constructed with two different unit balun structures based on current steering to reduce phase and amplitude errors. This type of topology can be compared with the conventional phase and amplitude correction techniques which do not incorporate the current steering. Designed and fabricated active balun in 0.18 μm CMOS process operates over 0.95 -1.45 GHz band, showing input reflection coefficient under -15 dB, phase error of 11˚ and gain error of 0.5 dB. Gain is measured to be 0.3 dB maximum and power consumption of 7.2 mW is measured.

A systematic design for asymmetric coupled-section Marchand baluns is presented. Asymmetrically coupled transmission lines in multilayer configuration are exploited for constructing Marchand baluns. Design equations for characteristic impedance and electrical length of asymmetrical coupled transmission lines are derived for establishing a systematic design procedure. Novel Marchand balun based on these design equations is composed of two identical asymmetrical coupled transmission lines. However, contrary to the general conventional design approach where ranges for characteristic impedances of coupled lines are ambiguously capitalized, values for characteristic impedance and length are explicitly expressed. Our approach is fundamentally different from the design method using coupling coefficients where solution for coupling coefficient is inherently restricted. To verify the proposed method, one design example is performed for wideband Marchand balun in multilayer configuration, and is fabricated for verifying the design procedure proposed. Maintaining the return loss more than 10 dB, the bandwidth is measured from 0.43 to 1.0 GHz, where S21 and S31 show better than 4 dB. The measured phase and amplitude imbalances illustrate 0.5 dB and ±5º, respectively.

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harmonic current source excited the antenna with the frequency set to 1.36 GHz. As seen in Figure 6, waveforms computed using the developed and direct FDTD methods overlap as long as the iteration is less than n s and a distance between the antenna and scatterer is sufficiently long.The developed method allows to limit the erroneous field leakage which appears when the radiation incompatible with the FDTD grid is injected across the TFSF interface. Although the error resulting from the unilateral coupling between the antenna and the scatterer decreases when the distance between these objects is increased, the dispersion error of the FDTD method increases as well. It has to be taken into consideration before applying the developed method for simulation of distant wire antennas and scatterers. CONCLUSIONThe application of the DGF-FDTD antenna simulations for excitation of the TFSF interface in the FDTD method was presented. It was verified that the DGF-FDTD solutions of antenna problems can be applied to introduce irradiation to the FDTD domain without the erroneous field leakage. The error resulting from the unilateral coupling between antenna and scatterer was demonstrated to be negligible for sufficiently long distance between these objects. Infinite DGF waveforms can be truncated using the Hann's window to speed up computations but this approximation introduces errors to the FDTD solution. The developed implementation facilitates the DGF applications in the FDTD simulations of radiation and scattering problems.