This letter describes a method of withdrawing interdigital electrodes for sidelobe reduction of surface acoustic wave filters by using implicit enumeration algorithm for 0-1 type integer optimization. Obtained results, for example, show that the sidelobe level of 40.98 dB can be obtained by withdrawing 14 electrodes from each of the input and output transducers consisting of 51 electrode pairs. Since the implicit enumeration algorithm gives several sub-optimal solutions in addition to the optimal one, it may be useful for some practical filter design.

Space-time block code (STBC) with complex orthogonal designs achieves full diversity with a simple maximum-likelihood (ML) decoding, however, do not achieve a full transmission rate for more than two antennas. To attain a higher transmission rate, STBC with quasi-orthogonal designs were proposed, whereas there are interference terms caused by relaxing the orthogonality. It has an impact on decoding complexity because a receiver needs to decode two symbols at a time. Moreover, QO-STBC does not achieve full diversity. In this paper, we propose a scheme which makes possible to decode symbols one by one, and two schemes which gain full transmission diversity by upsetting the balance of the transmit power and rotating constellation.

Orthogonal space-time block code (OSTBC) can achieve full diversity with a simple MLD, but OSTBC only achieves 3/4 of the maximum rate if more than two transmit antennas are used. To solve this problem, a quasi-orthogonal STBC (QOSTBC) scheme has been proposed. Even though a QOSTBC scheme can achieve the full rate, there are interference terms resulting from neighboring signals during detection. The existing QOSTBC using the pairs of transmitted symbols can be detected with two parallel MLD. Therefore, MLD based QOSTBC has higher complexity than OSTBC. To reduce the detection complexity, in this paper, we propose the heterogeneous constellation based QOSTBC for improving the detection property of QRD-MLD with maintaining a simple decoding structure.

A 1.9GHz film bulk acoustic resonator (FBAR)-based low-phase-noise complementary cross-coupled voltage-controlled oscillator (VCO) is presented. The FBAR-VCO is designed and fabricated in 0.18µm CMOS process. The DC latch and the low frequency instability are resolved by employing the NMOS source coupling capacitor and the DC blocked cross-coupled pairs. Since no additional voltage headroom is required, the proposed FBAR-VCO can be operated at a low power supply voltage of 1.1V with a wide voltage swing of 0.9V. An effective phase noise optimization is realized by a reasonable trade-off between the output resistance and the trans-conductance of the cross-coupled pairs. The measured performance shows the proposed FBAR-VCO achieves a phase noise of -148dBc/Hz at 1MHz offset with a figure of merit (FoM) of -211.6dB.

The letter deals with theoretical analysis on Lamb waves propagating in a composite membrane of ZnO and SiO2. Calculation was done for the lowest pseudo symmetric (S0) and antisymmetric (A0) modes. It was shown that, for example, when the thickness of each film is of the order of 0.1 wavelengths or less, S0 mode has a large electromechanical coupling coefficient of about 6% and a velocity of more than 5,000 m/s. A0 mode, as may be expected, has a quite small velocity of less than 1,500 m/s with an electromechanical coupling coefficient of about 3%. The result suggests that it may be possible to realise various monolithic acoustic wave devices based on Lamb waves propagating in the ZnO/SiO2 composite membrane.

Linear array antennas weighted by selective withdrawal of elements have been optimized for sidelobe reduction. The optimization was carried out for antennas with total elements up to 41 by modifying implicit enumeration algorithm for 0-1 type integer optimization. Results obtained, for example, show that the sidelobe level optimized decreases almost monotonically with an increase in the total number of elements, and that the sidelobe level of about 19.0 dB is obtainable for the antenna with total elements of 41.