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.
Wideband low loss double mode SAW filters
A method is discussed for achieving a wideband low-loss longitudinally coupled double mode surface acoustic wave (SAW) (DMS) filter using a leaky SAW on a 36 degrees Y-X LiTaO/sub 3/ and 64 degrees Y-X LiNbO/sub 3/ substrate with a high electromechanical coupling factor. Its characteristics are analyzed by computer simulation. With the use of the first-mode and third-mode resonance on a 64 degrees Y-X LiNbO/sub 3/ substrate and the selection of the optimum values for the distance between input and output interdigital transducers (IDTs), the electrode film thickness and the input/output IDT pair number, it is possible to achieve favorable characteristics with a 1-dB bandwidth of 33 MHz, and insertion loss of 2.1 dB, and an attenuation in the rejection band of 28 approximately 38 dB.<<ETX>>
A device for uranium series leaching from glass fiber in HEPA filter
For the disposal of a high efficiency particulate air (HEPA) glass filter into the environment, the glass fiber should be leached to lower its radioactive concentration to the clearance level. To derive an optimum method for the removal of uranium series from a HEPA glass fiber, five methods were applied in this study. That is, chemical leaching by a 4.0 M HNO3–0.1 M Ce(IV) solution, chemical leaching by a 5 wt% NaOH solution, chemical leaching by a 0.5 M H2O2–1.0 M Na2CO3 solution, chemical consecutive chemical leaching by a 4.0 M HNO3 solution, and repeated chemical leaching by a 4.0 M HNO3 solution were used to remove the uranium series. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after leaching for 5 h by the 4.0 M HNO3–0.1 M Ce(IV) solution were 2.1, 0.3, 1.1, and 1.2 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after leaching for 36 h by 4.0 M HNO3–0.1 M Ce(IV) solution were 76.9, 3.4, 63.7, and 71.9 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after leaching for 8 h by a 0.5 M H2O2–1.0 M Na2CO3 solution were 8.9, 0.0, 1.91, and 6.4 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after consecutive leaching for 8 h by the 4.0 M HNO3 solution were 2.08, 0.12, 1.55, and 2.0 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after three repetitions of leaching for 3 h by the 4.0 M HNO3 solution were 0.02, 0.02, 0.29, and 0.26 Bq/g. Meanwhile, the removal efficiencies of 238U, 235U, 226Ra, and 234Th from the waste solution after its precipitation–filtration treatment with NaOH and alum for reuse of the 4.0 M HNO3 waste solution were 100, 100, 93.3, and 100%.