2-IDT double-mode SAW filters with decreased insertion loss and advanced functionalities
This paper presents new 2-IDT double-mode SAW (DMS) filters with the decreased insertion loss and advanced functionalities: low input and output impedances, balanced operation and impedance conversion on 42º YX LiTaO3, 64º YX and 41º YX LiNbO3. To decrease the input and output impedances and resistive losses of the IDT electrodes the parallel connection of the 2-IDT DMS filters in the different acoustic tracks is used simultaneously reducing the aperture of each track. For an impedance conversion a series connection of the output IDTs in the 2 parallel acoustic tracks of the filters is used. To increase the selectivity of the filters the cascaded connection and phase weighting are employed. The constructional and topological optimization of the SAW filters is provided with a computer simulation using an equivalent circuit model. The 240–367 MHz samples of the balanced SAW filters have shown an insertion loss of about 1 dB, stopband attenuation of about 20 dB, impedance conversion from 50–75 Ω at the input to 200–300 Ω at the output in a wide fractional bandwidth of 2–6%. Two cascaded filter has provided an insertion loss of less than 2 dB and stopband attenuation of about 50 dB. The filters are housed in the 5×5×1.35 mm SMD packages.
Balanced low-loss 2-IDT double mode SAW filter with narrowed passband and improved selectivity
This paper presents the new balanced low-loss DMS filter with the narrowed passband and improved selectivity on 42° YX LiTaO3. The filter is realized as two-transducer scheme. A narrow passband of the filter is obtained by choosing a definite gap length between the input and output IDTs. Also the both long weighted input IDT and reflectors are used. A shape of the frequency response of the filter is determined by the weighting function of the input IDT, number of the electrodes in output IDT and reflectors, relationship between the electrode pitches in the input IDT, output IDT and reflectors. An optimization of the mentioned parameters with a computer simulation using equivalent circuit model allows to get a specified high selectivity of the filter with a fractional bandwidth of 0.5-0.6% under condition that the insertion losses are low and input and output impedances are close to the specified real values. To decrease the input and output impedances the parallel connection of the two filters in the different acoustic tracks is used. To improve the selectivity of the filter the cascaded connection and phase weighting the input IDT are employed. The 300 MHz sample of the balanced SAW filter has shown an insertion loss of 3 dB, 2-dB bandwidth of 1.5 MHz, stopband attenuation of 70 dB at ±12 MHz offsets from a center frequency in a 75-Ω balanced system. The filter did not require the matching elements and housed in the 9.1×7.1×2 mm SMD package.
PASSIVE AND LOW-ENERGY RESEARCH AND PRACTICES-DEHUMIDIFICATION
Methods of achieving acceptable indoor conditions in overheated, temperate, and underheated humid climates are discussed and compared. Desiccants and desiccant systems utilizing solid and liquid sorbents and various low-energy mechanical systems are described and evaluated.