Abstract: A programmable phase-locked loop frequency synthesizer having a feedback path that includes a tuned discriminator circuit is frequency modulated by coupling a portion of the modulating signal into the feedback path to effect modulation at rates which exceed the bandwidth of the phase-locked loop and by utilizing a portion of the modulating signal to frequency modulate the phase-locked loop reference signal to effect modulation at rates within the bandwidth of the phase-locked loop. A digitally controlled phase shifter that forms a portion of the discriminator tuning circuits in effect divides the phase-locked loop tuning range into a series of relatively narrow centiguous frequency bands. Data, representing deviations in the discriminator characteristics for each of these frequency bands, are stored in an erasable programmable read only memory. As the phase-locked loop is tuned to a particular frequency, a microprocessor determines the associated frequency band, accesses the stored data appropriate to that frequency band and establishes the proper setting of the digitally controlled phase shifter. The accessed data is coupled to a multiplying digital to analog convertor to automatically adjust the level of the modulating signal so that the system exhibits relatively constant modulation characteristics for each frequency band within the tuning range of the phase-locked loop. Low distortion is achieved within each of the relatively narrow frequency bands by circuitry which reduces or eliminates amplitude variations within the feedback path that includes the discriminator circuit, band pass filtering within this feedback path, and a feed-forward circuit arrangement that prevents modulation components from adversely affecting the discriminator tuning circuits. Additionally, a gain switching arrangement that automatically reduces the gain of the feedback loop and the phase-locked loop gain ensures system stability for all operating and tuning conditions.

Abstract: A classification of negative-feedback amplifiers with up to the maximum of four overall feedback loops is presented, forming the complete set of two-port amplifier types with fundamentally different transfer properties. Nonenergic feedback techniques are Introduced, making use of Ideal gyrators and transformers in the feedback networks, thus enabling unlike other wide-band feedback techniques, the maintenance of the signal-to-noise ratio and the signal-handling capablity and power efficiency of the active part of the amplifiers. Theoretically, input and output Impedances can be obtained that are either zero or infinite, or linear and accurately known. In addition, a class of practical amplifier configurations Is presented, where the gyrators are replaced by transformers and Impedances. Nonenergicness Is lost as a consequence, but interesting transformer-feedback configurations are obtained, some of which are new. They are especially suitable for characteristic Impedance matching with very low noise figures and small losses of output power.

Abstract: A delta modulator comprising a feedback loop incorporating a cascade arrangement formed by a difference producer, a loop filter, a two-level quantizer, a clock pulse-controlled sampler and a feedback path. In order to optimize the signal/quantization noise ratio the minimum phase loop filter has such a phase characteristic that the phase shift in the feedback loop caused by the time delay of the sampler is replenished to approximately 180° with a certain margin, in a frequency range up to a certain cut-off frequency, the phase of the loop filter being constant above the cut-off frequency.

Abstract: An improved gain control circuit of the "eight transistor gain cell" type is disclosed. The improvements comprise (1) means for operating the circuit as a Class AB amplifier and (2) means for reducing the distortion component in the output signal due to the inherent parasitic base and emitter resistances of the transistors of the gain cell of the gain control circuit.

Abstract: In an integrated circuit audio power amplifier a 6 db per octave frequency-gain roll off is obtained in a conventional manner by converting a high gain inverter to an integrator and driving the integrator from a current source. A second cascaded stage is also provided so that it operates at lower gain and has a matching high frequency roll off. When such characteristics are combined in cascade the result is a 12 db per octave roll off at the higher frequencies. A flat negative feedback loop is employed to maintain a controlled constant low frequency gain. In the response region located between the 12 db per octave slope region and the constant gain region there is a 6 db per octave slope. The configuration is stable without resorting to frequency sensitive feedback. When such an amplifier is constructed to have its gain versus frequency roll off to unity at the low frequency end of the AM radio broadcast band, the amplifier will emit very little energy in the radio band, yet a sufficient audio bandwidth is available for Hi Fi response.

Abstract: A complete audio processing system of solid state design for providing improvement of audible signals through dynamic compression including an active filter for transient suppression, a gain control, and a plurality of active frequency control stages for selectively controlling internal gain of signals in different frequency bands. Outputs of the frequency control stages are mixed and provided to a compressor stage having an operational amplifier of gain fixed by a DC feedback network. A gain cell provides variable negative feedback. A rectifier circuit measures the average value of the audio input to the compressor stage and controls the gain cell as a function of the average value to provide negative feedback which increases as a function of increase in the level of said input signal. An attenuator receives the output of the operational amplifier and provides an attenuated but dynamically compressed output so that the circuit provides no substantial overall gain but achieves high compression. Optimum achievable compression is indicated by an LED indicator lamp.

Abstract: Otala's suggested rules for eliminating transient intermodulation distortion (TIMD) in a low-pass feedback amplifier have been widely and wrongly interpreted as being necessary. In fact, the necessary and sufficient condition, for avoiding gross TIMD with a broad-band input signal, is that the forward-path stages before the dominant pole should not clip on a signal input which is twice the amplitude of full rated input to the complete amplifier including feedback. When the input signal is band limited, this dipping criterion can be relaxed by a factor approximately equal to the ratio of the (signal 3 dB bandwidth) to the (amplifier closed-loop 3 dB bandwidth). In both cases the condition is essentially independent of the low-frequency loop gain. There is no TIMD penalty whatsoever in using a large amount of feedback, provided the forward-path gain is concentrated in stages that do not precede the dominant pole. All the usual benefits of feedback accrue with increasing loop gain.

Abstract: The DC output level of a video signal amplifier is compensated to remain constant as the amplifier is gain controlled in response to a gain control voltage supplied from a gain control circuit which also supplies a DC compensation voltage to the amplifier The DC compensation is preserved by means of an additional network which senses the DC bias of both the amplifier and the gain control circuit, and corrects a deviation of the amplifier bias and the gain control circuit bias from a prescribed mutual relationship The sensed DC bias of the gain control circuit is also used to establish a black reference level for the video signal

Abstract: Volume control circuits generally vary the overall gain of a low-frequency amplifier by varying the gain in a negative-feedback branch. At very high gain, at which very large output signals are obtained, the negative-feedback is then very small, which may produce a non-linear distortion. In accordance with the invention the gain of a frequency-compensation stage is varied so that it increases when the overall gain increases. The loop gain at higher output amplitudes is now higher than it would otherwise be so that non-linear distortion is reduced.

Abstract: PURPOSE:To obtain a good beam shape, by applying a prescribed driving waveform having an optimum frequency characteristic to each element of a divided transducer. CONSTITUTION:The signal generated from a drive signal generating part D is filtered in filters FL1 and FL2 and is supplied to gain adjusting equipments G1, G2, and G1'. The gain adjusting equipment G1 connected to a transducer E2 on the outside circumference through an amplifier Ampl supplies the output to the gain adjusting equipment G1' also. The gain adjusting equipment G1' is operated to enhance the gain near a frequency f1. Output signals of these gain adjusting equipments G1' and G2 are added in an adding circuit AD. Thus, the signal which is given from the adding circuit AD to a transducer E1 in the inside through an amplifier Amp2 is driven with a gain which is higher than that of the transducer E2 in the outside by components corresponding to the output gain of the gain adjusting equipment G1'.

Abstract: PURPOSE:To enhance the level margin for the recording/reproducing circuit using the 4/5NRZI system to write 4 bits after converting them into 5 bits, by detecting the peak of the output waveform of a reading head by means of a delay line during the reproduction and then performing the deomdulation of data. CONSTITUTION:The circuit consists of the 4/5 code converter 1, timing compensating circuit 2, writing amplifier 3, magnetic head 4, preamplifier 5, AGC6, delay line differenciator 7, LPF8, pulse shaper 9 and VFO10. In the 4/5NRZI system, the length of continuation can be set to <=2 for the bit 0 in the converted series, and accordingly the data can be demodulated by the peak detection like the MFM system. In this case, however, the level margin can be increased by using an approximate differentiating circuit consisting of the delay line in place of the CR differenciator. At the same time, the phase margin can be secured by shifting the writing timing previously in the direction opposite to the direction where the peak shift occurs to the presumed peak shift.

Abstract: The gain variation is made in the software logic of the pitch angle controller. The gain level is changed depending upon the level of power error. The control uses low gain for low pitch activity the majority of the time. If the power exceeds ten percent offset above rated, the gain is increased to a higher gain to more effectively limit power. A variable gain control functioned well in tests on the Mod-0 wind turbine.

Abstract: The relative stability curves, the time-delay sensitivity and loop-gain sensitivity over a wide frequency range have been evaluated for both linear and non-linear time-delay systems designed with a relative stability (6-dB gain margin) and minimum time-delay sensitivity conditions imposed on the system. The resultant system shows an improved performance.