Cincinnati Electronics Corporation

Texas Instruments Corporation

Elvin Duane Stepp

Gary L Claypoole

James Reggie Talley

A carrier wave is frequency modulated to one of M different output frequencies that deviate from the carrier wave frequency by .+-.k.sub.1, .+-.k.sub.2 . . . .+-.k.sub.q. The carrier is modulated in response to a clocked digital signal having n data bits forming a data word, where M=2.sup.n. In response to the digital signal an n bit control signal is derived. M/2 clock frequencies synchronized with the clock data signal are simultaneously derived. An up-down counter responds to the control signal so that one bit of the control signal controls the counting direction of the counter and (n-1) of the bits control which one of the M/2 frequencies is applied to a clock input of the counter. In response to the count in the counter, orthogonal sinusoidal like waves at one of the frequencies k.sub.1, k.sub.2 . . . k.sub.q are derived. The M/2 clock frequencies are equal to k.sub.1 2.sup.P, k.sub.2 2.sup.P . . . k.sub.q 2.sup.P, where P is the number of clock frequency bits in the counter. The orthogonal sinusoidal like waves at the selected frequency are vectorially combined with the carrier wave to derive a constant amplitude wave that deviates from the carrier frequency by the selected frequency k.sub.1, k.sub.2 . . . k.sub.q in a direction controlled by the value of the one bit.

Frequency shift key modulator

A clock wave is synchronized to the frequency of serial binary data bits. Digital circuitry derives a clock wave by responding to the data bits to selectively (a) increment a reference frequency, (b) decrement the reference frequency, and (c) not change the reference frequency. The digital circuitry divides each data bit into an even number of sub-bits. The binary value associated with a first half of the divided sub-bits of a particular data bit is compared with the binary value associated with a second half of the divided sub-bits of the particular data bit. In response to the derived clock wave and the comparison, the reference frequency is derived, incremented or decremented. The frequency of the source is respectively incremented and decremented in response to first and second relations of the binary value associated with the first half relative to the binary value associated with the second half. The frequency of the source is not changed when the binary values associated with the first and second halves are equal.

Digital clock bit synchronizer

Positive feedback of an acoustic signal from a loud speaker to a microphone of a loud speaker system, i.e., howling, is prevented by randomly phase shifting an electric signal containing audio information supplied to the speaker. The random phase shifting is provided by variably delaying the electric signal in a serial analog register having a shift rate determined by an output signal of a pseudo random code generator.

Audio feedback suppressor

A frequency synthesizer or a circuit for deleting cycles from a wave source includes a dual modulus counter responsive to a reference frequency source of the synthesizer or waves of the source. The dual modulus counter selectively decreases the number of cycles of the source by the factors K.sub.2 and (K.sub.2 +1). A frequency divider divides the frequency of the source by a third factor L to derive an output wave. The dual modulus counter is activated so it divides by K.sub.2 +1, whereby the dual modulus counter derives an output signal having a frequency F.sub.0 =F.sub.in /K.sub.2 (1-1/L), where F.sub.in equals the frequency of the source, L is an integer and K.sub.2 is an integer greater than L.

Pulse control circuit

A shunt regulator circuit having a reference voltage generator in which the collector currents of a pair of transistors are adjusted by the ratios of their load resistances to produce a temperature coefficient equal and opposite to the temperature coefficient of third transistor; a proportional sample of the output voltage is compared to the temperature stable reference voltage to adjust the shunt current to maintain the output voltage constant.

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Cincinnati, OH, United States of America

Elvin Duane Stepp