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 device for sample modulating electronic information signals, which includes a pulse position modulating circuit having a first input coupled to receive information signals, a second input coupled to simultaneously receive uniformly spaced sampling signals, and an output for generating thereon in response to each sampling signal an electronic output impulse at a time instant indicating the amplitude of the simultaneously received information signals. Also included is an acoustic surface wave device having an impulse response of predetermined shape and finite length. The surface wave device has an input coupled to receive the impulses from the pulse position modulating circuit for generating in response thereto output signals proportional to the convolution of the impulses with the impulse response. Accordingly, these output signals also are of predetermined shape and finite length, and thus have a highly controllable frequency spectrum.

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.

Abstract: A device for sample modulating electronic information signals which includes mixing circuitry having a first input coupled to receive information signals, a second input for receiving electrical sampling signals, and an output for generating thereon electrical output signals proportional to the product of the information signals and the sampling signals. Also included is an acoustic surface wave device having an impulse response of predetermined shape and finite length. The surface wave device has an output coupled to the second input of the mixing circuit for generating thereon the sampling signals. These signals are proportional to the finite impulse response of predetermined shape, and accordingly have a highly controllable frequency spectrum.

Abstract: A method for transmitting and receiving high resolution television pictures is disclosed. Each frame of the pictures is comprised of scan lines having frequency components from 0 to f.sub.MAX where f.sub.MAX is .gtoreq. the bandwidth BW of the conventional television system. Frames are transmitted and received via analog video signals f.sub.k (t) which are formed from selected samples of predetermined scan lines. Each of the analog video signals has a frequency spectrum of width less than BW. High resolution televisions receive the video signals f.sub.k (t) and extract the selected samples therefrom. The samples are then recombined to form high resolution pictures. Conventional television receivers use the analog video signals f.sub.k (t) as common analog video scan line signals in the usual manner.

Abstract: An improved acoustic waveguide structure which comprises a ridge waveguide disposed in a horizontal direction extending outwardly from a substrate. The horizontal orientation of the waveguide which is in the form of a ledge results in particle motion of the ledge predominantly normal to the substrate plane with the largest motion at the free edge of the ledge and almost no motion in the substrate, thereby permitting a plurality of such structures to be densely packed on a common substrate.

Abstract: An improved acoustic waveguide structure which comprises a ridge waveguide disposed in a horizontal direction extending outwardly from a substrate. The horizontal orientation of the waveguide which is in the form of a ledge results in particle motion of the ledge predominantly normal to the substrate plane with the largest motion at the free edge of the ledge and almost no motion in the substrate, thereby permitting a plurality of such structures to be densely packed on a common substrate.

Abstract: An improved acoustic waveguide structure which comprises a ridge waveguide disposed in a horizontal direction extending outwardly from a substrate. The horizontal orientation of the waveguide which is in the form of a ledge results in particle motion of the ledge predominantly normal to the substrate plane with the largest motion at the free edge of the ledge and almost no motion in the substrate, thereby permitting a plurality of such structures to be densely packed on a common substrate.

Abstract: An improved acoustic waveguide structure which comprises a ridge waveguide disposed in a horizontal direction extending outwardly from a substrate. The horizontal orientation of the waveguide which is in the form of a ledge results in particle motion of the ledge predominantly normal to the substrate plane with the largest motion at the free edge of the ledge and almost no motion in the substrate, thereby permitting a plurality of such structures to be densely packed on a common substrate.

Abstract: A transform structure employing surface wave devices performs Fourier transform operations on a time-limited substantially band limited signal. The output signal of the transform structure is related to the Fourier transform of the input signal in a manner which permits forming the product of this output with a similar output of a second transform structure. This product is inverted by a third transform structure so as to provide the convolution of the two original input functions. The overall structure comprises a filter apparatus readily programable in either the time or frequency domain.

Abstract: A tunable surface wave resonator is disclosed comprising a substrate of piezoelectric material having acoustic surface wave absorbing extremities, a pair of spaced acoustic surface wave gradient reflectors positioned adjacent to the absorbing extremities of the substrate, a pair of spaced multiphase surface wave tuning transducers selectively positioned between the pair of gradient reflectors over antinode positions of desired resonant frequency standing wave, and an acoustic surface wave transducer selectively placed for optimum coupling of energy into the acoustic resonant cavity formed by the pair of gradient reflectors.

Abstract: A variable frequency VHF or UHF band oscillator is disclosed. Principal control over the precise location and stability of the frequency of oscillation is provided by a surface wave delay line in the regenerative feedback path of a broadband amplifier. The surface wave delay line is capable of passing substantial energy within each of a plurality of very narrow passbands. Controls are provided for ensuring that at any given time the circuit can oscillate only at the resonant frequency of one of these passbands. Selection of the frequency of oscillation is in accordance with an externally applied digital frequency select signal.

Abstract: An improved acoustic waveguide structure which comprises a ridge waveguide disposed in a horizontal direction extending outwardly from a substrate. The horizontal orientation of the waveguide which is in the form of a ledge results in particle motion of the ledge predominantly normal to the substrate plane with the largest motion at the free edge of the ledge and almost no motion in the substrate, thereby permitting a plurality of such structures to be densely packed on a common substrate.

Abstract: A surface wave device having a periodic frequency response characteristic is disclosed. At least two reflective grating structures are located at the surface of the surface wave device such that acoustic surface wave standing wave resonance can occur in the region between the two reflector structures. The spacing between the reflector structures is sufficiently large to insure that standing wave resonance can occur at any of a plurality of discrete resonance frequencies, all falling within the bandwidth of the grating reflectors themselves.

Abstract: Prior art methods for shaping the impulse response of a surface wave delay line interdigital transducer include finger width weighting and finger overlap weighting. The new method for shaping the transducer impulse response disclosed herein overcomes several objectional characteristics of the prior art methods. The new method involves removal of individual fingers or groups of fingers from selected portions of the transducer. The amplitude of the impulse response in those regions from which fingers have been removed is reduced below the value which it would have if no fingers had been removed. The method thus provides the capability to control the relative amplitudes of the impulse response along the length of the transducer.