Abstract: A universal decoder for scrambled television signals in which the signals are processed in a circuit by converting them to other frequencies and then removing the scrambling signal. One method uses one or more narrow filters at a fixed frequency with the television signal being heterodyned down to the frequency of the filters to place the scrambling signals in the rejection band of one of the filters. A second method eliminates scrambling signals by filters at video frequencies. In this method, the frequency in phase with the television signal carrier of a television channel is regenerated by filtering it with a narrow crystal filter and by means of an automatic phase comparison (APC) loop. The regenerated carrier is then used to synchronously demodulate the television signal. A third method for removing the scrambling signals is by use of one or more comb filters.

Abstract: A master decoder for scrambled television signals in which the signals are processed in a circuit by converting them to other frequencies and then removing the scrambling signal. One method uses one or more narrow filters at a fixed frequency with the television signal being heterodyned down to the frequency of the filters to place the scrambling signals in the rejection band of one of the filters. A second method eliminates scrambling signals by filters at video frequencies. In this method, the frequency in phase with the television signal carrier of a television channel is regenerated by filtering it with a narrow crystal filter and by means of an automatic phase comparison (APC) loop. The regenerated carrier is then used to synchronously demodulate the television signal. A third method for removing the scrambling signals is by use of one or more comb filters.

Abstract: A Television Signal Transmission Security System which provides a higher degree of security then previously possible by utilizing encoding and decoding technology which effectively prevents pirating by amateurs or experimenters. The television signal transmitted is encoded by injecting one or more modulated interfering signals in specific frequency slots in close proximity to the video carrier. Continuous or alternating interfering signals can be injected either above or below the video carrier between harmonics of the horizontal frequencies. Combinations of interfering signals provide coding techniques making the system virtually pirate proof. The interfering signal is removed by very narrow band rejection filters having a rejection band attenuation greater than about 40 dB over a bandwidth equal to the bandwidth between adjacent harmonics of the horizontal sweep frequency. The filters are constructed using advanced technology to produce the quartz crystal bulk resonators or surface acoustic wave filters.

Abstract: A Television Signal Transmission Security System which provides a higher degree of security then previously possible by utilizing encoding and decoding technology which effectively prevents pirating by amateurs or experimenters. The television signal transmitted is encoded by injecting one or more interfering carriers in specific frequency slots in close proximity to the video carrier. Interfering carriers can be injected either above or below the video carrier between harmonics of the horizontal frequencies. Combinations of interfering carriers provide coding techniques making the system virtually pirate proof. The interfering carrier is removed by very narrow band rejection filters having a rejection band attenuation greater than about 40 db over bandwidth of up to 4000 Hz and a 3 dB bandwidth of approximately 5 kHz. The filters are constructed using advanced technology to produce the quartz crystal bulk resonators or surface acoustic wave filters.

Abstract: An echo-compensating surface acoustic wave interdigital transducer in which the entire length of the end finger of the transducer at each end is connected directly or indirectly to at least one of the bus bars, the end finger extends only partially across the aperture of the transducer, and the space which is colinear with the end finger across the remaining portion of the aperture is not occupied by any surface-acoustic-wave-reflective structure. The end finger is substantially a quarter of an acoustic wavelength out of phase with the nearest interior finger with respect to an incident wave at the operating frequency of the transducer, so that the acoustic reflections of the end finger and the nearest interior finger are in phase-opposition to each other.

Abstract: A compensation scheme is disclosed which avoids the requirement of high alignment accuracy, and thus reduces the production cost of a surface acoustic wave filter, by employing a compensating transducer system which is arranged with its fingers parallel to those of the receiving transducer. The requirement of receiver sensitivity at the trap frequencies is nevertheless achieved by using a very narrow compensating beam width. The narrowness of the compensating beam also allows it to pass directly through a multi-strip coupler. The degree of compensation achieved is controlled by aiming the compensating beam at a small region of the apodized receiving transducer located at the extremity of the major lobe; by restricting the aperture of the compensating transducer system; and by trimming the printed circuit capacitor which couples the compensating transducer system to the electrical input signal.

Abstract: A surface wave acoustic filter is compensated for diffraction and other spurious effects, which distort its frequency response, by adding an auxiliary acoustic channel which is in parallel with the primary acoustic channel, is out of phase therewith, and mimics the frequency response of the primary channel to the diffracted or other spurious wave.

Abstract: In order to avoid spurious responses at the third harmonic of the signal frequency, a surface acoustic wave filter employs a multi-strip track coupler in which the spacing d of the elements is an integral multiple I of the acoustic wavelength .lambda. of the third harmonic. When the condition d=I.lambda. is satisfied, the coupler blocks transmission of the third harmonic from the input transducer track to the output transducer track. This basic principle can also be used to block other frequencies.

Abstract: In order to reduce the reflectivity of an apodized surface acoustic wave transducer, one portion of the dummy area thereof is bare and another portion is 100% metallized, and the boundary between these two regions is shaped to equalize total acoustic transit times across the transducer aperture. This avoids any net refraction, and thus permits any acoustic wavefronts which traverse the two regions to remain flat.

Abstract: An acoustic wave storage convolver includes a plurality of sampling transducers coupled to a surface wave propagating medium along a path defined by a pair of opposedly disposed input transducers. The sampling transducers, each of which is connected to a suitable signal storage element, are equally spaced along the path by an integral number of acoustic wavelengths plus or minus 1/4 wavelength for providing successive samples of surface waves propagated along the medium in phase quadrature relationship. Means initiating the signal storage function and output means developing the convoluted product of two high frequency signals applied to the input transducers are provided.

Abstract: A ghost cancellation system includes a surface-wave device operable for developing a replica of the ghost component of a video signal, which replica is combined with the video signal to eliminate or cancel the ghost component. The surface-wave device comprises an input transducer responsive to a modulated video signal for launching uniform acoustic surface-waves along a path traversing a balanced pair of output transducers and impinging upon a reflector array. The reflector array includes means for initiating non-uniform surface-wave reflections suitable for causing the output transducers to develop an output electrical signal comprising the ghost replica.

Abstract: An acoustic surface wave filter comprises a piezoelectric substrate defining a propagating surface upon which a transmitting and receiving transducer pair are formed in offset alignment. An interposed multistrip coupler provides surface wave coupling between the offset transducers. An elongated isolating barrier is interposed between the transducers in an orthogonal relationship with the coupler to prevent surface wave propagation between the transducers along other than the primary axis. In one embodiment, an isolating barrier is composed of an acoustic surface wave dampening material, while in another a barrier of acoustic surface wave reflective material is used.

Abstract: An acoustic surface wave filter has offset transmitting and receiving transducers formed on a wave propagating surface of a piezoelectric substrate. A multistrip coupler interposed between the transducers on the propagating surface includes a plurality of identical conductor groups forming coupler elements uniformly spaced on the surface and selectively attenuates either of the symmetrical or anti-symmetrical mode components of coupled waves within a predetermined range of acoustic wavelengths. In one embodiment, each conductor group includes electrically connected pairs which attenuates the symmetrical mode component while in another embodiment each conductor group includes a first continuous filamentary conductor and a second filamentary conductor having a discontinuity at its approximate center which attenuates the anti-symmetrical mode component.

Abstract: An acoustic surface wave filter has offset transmitting and receiving transducers formed on the wave propagating surface of a piezoelectric substrate. A two-segment multistrip coupler is interposed on the propagating surface and provides "track switching" or "sidestepping" action for signals within the coupler passband. The coupler includes a split-connected portion formed by electrically connected filamentary conductor pairs and a split-isolated portion formed by electrically continuous filamentary conductors and interleaved conductors having a discontinuity at their center. The split-connected portion attenuates the symmetrical mode components of acoustic waves within the coupler stop band while the split-isolated portion attenuates the anti-symmetrical mode portion of acoustic waves within the coupler stop band, producing an improved trap response.