Vamsi Krishna Velidi

Design of compact microstrip diplexer with high selectivity

A novel design of compact microstrip diplexer, using coupled dual-mode open-loop resonators, is proposed. The main advantage in using dual-mode open-loop resonators is that a compact narrowband bandpass filter with high selective asymmetrical frequency response is easily realized. This property is explored to design diplexer for a system with two extremely close bands. A prototype diplexer operating in the 2.07/2.3 GHz band, having compact size (44 mm × 11 mm) and high isolation (>;-40 dB), is designed for demonstration.

Millimeter-wave ultra-wideband bandpass filter with quarter-wavelength short-stubs and port extensions using 0.18-μm CMOS process

Millimeter-wave ultra-wideband (UWB) bandpass filter implemented in a standard 0.18-μm CMOS process is presented in this paper. Thin film microstrip structure (TFMS) is constructed appropriately on the low-resistivity silicon substrate without any post processing steps. Using the transmission line topology composed of quarter-wavelength short-circuited shunt stubs and port extensions, a wide return loss bandwidth is achieved so as to make up a class of UWB TFMS bandpass filter at 60 GHz. A compact geometry with sinuous shaped lines is designed and fabricated. The predicted and measured results are in good agreement up to 110 GHz.

Compact harmonic suppression branch-line coupler using signal-interference technique

A novel application of signal-interference technique to branch-line coupler design is proposed for miniaturization and wideband harmonic passband suppression. The couplers second, third and fourth harmonic passband responses are attenuated due to a pole at each of these harmonics. Design equations and graphs are provided using lossless transmission line model. A prototype coupler, having a compact (λg/6)2 area, that is 44.4% of the (λg/4)2 conventional coupler area, is fabricated in microstrip form for validation purposes. The input matching, isolation, amplitude and phase balance bandwidths of the proposed coupler are comparable to those of the conventional coupler.