Abstract: A surface wave device (10) having substrate with at least a surface layer of piezoelectric material (12) and at least one pair of opposing electrically conducting pads (14 and 16) is disclosed. A first group of at least three electrodes (18, 20 and 22) in a distance (24) of one half wavelength of a preselected operating frequency is disposed on the piezoelectric surface between the opposing pads. At least one of the electrodes is electrically connected to one of the opposing pads and the remaining electrodes are electrically connected to the other opposing pad. The sequence of the three electrodes is unevenly distributed with respect to which of the pads the electrodes are connected to. At least two additional groups of at least three electrodes similar to the first group have sequences of electrodes within each group that is distinct from the other groups.
Abstract: A surface wave device includes a substrate (12 in FIG. 7) having a surface layer of piezoelectric material (14), at least one pair of opposing electrically conducting pads (16 and 18) and at least two electrodes (20 and 22) which generate surface waves that vary significantly in strength in a direction transverse to the opposing pads. An ungrounded pad (16) forms an electrode array of parallel segmented electrodes (24), joined by electrically conducting connecting bars (26), having more segmented electrodes near the center of the transverse distance than near the pads. A grounded electrode (22) forms a segmented electrode array having segmented electrodes (44) joined by electrically conducting connecting bars (46) having fewer segmented electrodes near the center of the transverse distance than near the pads.
Abstract: A surface wave resonator device (10) includes a substrate (12) having a surface layer of piezoelectric material (14), first and second reflective grating structures (16 and 18) and a middle grating structure (40). The middle grating structure includes an odd multiple of one-quarter wavelength for the resonant frequency of the first and second reflective grating structures. The surface acoustic wave transmission velocity of the middle grating structure is substantially equal to the surface acoustic wave transmission velocity of the first and second reflective grating structures. One arrangement includes a surface acoustic wave input transducer (52) and a surface acoustic wave output transducer (58).
Abstract: The present invention provides a method and apparatus for scrambling and unscrambling television signals to prevent reception of acceptable signals by an unauthorized television receiver while maintaining the television signal recoverable by an authorized receiver. The present invention can also be used for reducing the necessary carrier signal power of a television transmitter.A transmitter (12) passes a television signal through at least one linear filter (30, 32 and 34) of the type that produces multiple time delayed signals of differing time delays.A receiver (14) receives the multiple time delayed signals from the transmitter and passes them through at least one linear filter (64, 66 and 68) to add the signals together so that one signal representative of the original is reinforced, allowing acceptable reception by an authorized viewer.In one arrangement, the linear filters are SAW devices.
Abstract: A surface wave device is disclosed which includes a substrate (12) having a piezoelectric surface (14), an acoustic surface wave transducer (16 and 18) for converting between an electrical signal and acoustic surface waves propagating on the piezoelectric surface and reflective structures (22) which cause reflections of acoustic surface waves in the portion of the piezoelectric surface over which the transducer is disposed. Numerous kinds of reflective structures are disclosed. An acoustic surface wave resonator using the present invention is disclosed, along with bandpass filters with multiple poles. A low-loss transversal filter using the present invention is also disclosed.