Abstract: A subscriber control system designed to be placed outside of the subscriber's home, for controlling access to cable television signals provided by a cable television headend. The system is modular in design containing a single control module and a single RF distribution module both shared by a number of jammer modules. The jammer modules contain a plurality of frequency agile oscillators, the frequencies of which can be changed in time-multiplex fashion. The outputs of the jammer modules can be shared amongst a number of subscribers using space division switching.

Abstract: A frequency division network is disclosed in which a sinusoidal signal is converted to a digital format for frequency division and then converted back to the sinusoidal format, the sinusoidal output waveform having low phase noise. In a preferred embodiment the frequency conversion takes place in an m-fold plurality of edge triggered flip-flops, connected to divide by two, and clocked by the sinusoidal waveform. Each flip-flop is subject to jitter causing phase noise, which is minimized when the output of two sets of four flip-flops are averaged, and then filtered to obtain the sinusoidal fundamental. When a crystal filter having a very narrow pass band is employed, the phase noise is further reduced. The frequency division network uses low cost components and the phase noise of the output waveform approaches that of a stable crystal oscillator.

Abstract: The invention relates to a two state phase modulator with minimum amplitude modulation. The modulator assumes two phase states differing by .THETA. where .THETA. is a sub-multiple of 180.degree. which permits a phase variation of 180.degree. for phase coded transmissions when the frequency of the phase modulated carrier wave is multiplied by the reciprocal of the sub-multiple. Three equal components are derived in the phase modulator: an in-phase, an out of phase, and a quadrature phase component. The out of phase component is delayed in relation to the in-phase component by .THETA./2, while the quadrature phase component is delayed .THETA./4. The in-phase and out of phase components are then reduced by a factor (2 sin .THETA./2) selected such that when added to the quadrature component, the resultants have a magnitude equal to that of the quadrature component and differ in phase from the quadrature comonent by .+-..THETA./2.

Abstract: A low phase noise frequency multiplier is disclosed for multiplying a sine wave obtained from a low phase noise crystal oscillator to higher frequencies than can be directly obtained from a crystal oscillator. The multiplication occurs without the ordinary increase in phase noise. The multiplier, when tripling the frequency contains a low phase noise frequency doubler. The double and triple frequency terms in the tripler are synthesized from two orthogonally related derivatives of the same wave, which are then multiplied in a double balanced mixer. The process reinforces the desired harmonics while not reinforcing the short term random phase noise, and produces a substantial improvement in the single sideband phase noise ratio over conventional frequency multipliers.

Abstract: An interface circuit that couples the output of a differential AFC detector to a tuner and in so doing provides a single-ended control signal and a substantially constant reference signal. A bridging circuit combines the differential outputs to effect a substantially constant signal which is appropriately scaled by a referencing circuit so as to develop the reference voltage required. A dividing circuit coupled to one of the differential outputs develops an AFC control voltage having the range required to accommodate the tuner's AFC-responsive circuitry.