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.
SAW filter based on parallel-connected CRFs with offset frequencies
We present designs for two-track devices, based on the coupled resonator filter (CRF) concept, having either two or three transducers. The tracks are connected in parallel, imposing a frequency shift between them. Examples of this approach are demonstrated in different frequency ranges, both on quartz and - for the first time - on 42/spl deg/-LiTaO/sub 3/. We also introduce a parallel-track design with distributed gaps. The device can also operate as a single-to-balanced (BALUN) transformer.
Development of an Analytical Method for Explosive Residues in Soil
Abstract : An analytical method was developed to determine the concentrations of HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT in soil. The method involves extracting a 2-g sample with 50 mL of acetonitrile using an ultrasonic bath procedure for 18 hr. A 10-mL portion of the extract is diluted with 10 mL of water, filtered through a 0.45-micrometer Millex SR filter, and analyzed by RP-HPLC using a fixed 254-nm UV detector. Separations were obtained on an LC-18 column eluted with 50:50 water-methanol. Retention times were 2.55, 3.82, 5.16, 6.25, 7.04, 8.47 and 10.15 min for HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT, respectively. Confirmation of analyte identities is recommended by RP-HPLC on an LC-CN column using 50:50 water-methanol. Kinetic studies using naturally contaminated soil indicated that equilibrium was achieved within 24 hr for the majority of soils and analytes studied. The method provides linear calibration curves over a wide range of concentrations. Reporting limits were conservatively estimated at 1.6, 1.8, 1.5, 0.5, 5.5, 0.8 and 0.8 micro grams/g for HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT. Analytical precision was estimated at + or - 0.44, 0.51, 0.43, 0.13, 1.24, 0.27 and 0.20 micro grams/g, respectively, in the range of homogeneous variance near the detection limits. At higher concentrations the relative standard deviation was constant at 2% for HMX, RDX, DNB and TNB, 3% for TNT and 2,4-DNT, and 6% for Tetryl.