Wandel & Goltermann

Wandel U. Goltermann Gmbh & Co.

Wandel & Goltermann Gmbh & Co. Kg

Peter Harzer

A variable-frequency main oscillator of digitally tunable high output frequency f.sub.A is controlled by the integrated output voltage of a phase discriminator receiving on the one hand a relatively low comparison frequency and on the other hand a matching feedback frequency stepped down from output frequency f.sub.A by frequency division or by heterodyning with an auxiliary frequency f.sub.H of the same order of magnitude from an ancillary oscillator, a difference frequency f.sub.D =f.sub.A -f.sub.H is fed to a frequency discriminator delivering a corrective voltage, independent of that emitted by the phase discriminator through a filter network, to the control input of the main oscillator. A pair of frequency selectors varying the feedback frequency and/or the comparison frequency enable the output frequency f.sub.A to be adjusted in coarse and fine tuning steps, the coarse adjustments being also applied to the auxiliary frequency f.sub.H to limit the excursions of the difference frequency f.sub.D. In order to minimize shifts in the corrective voltage due to changes in the setting of the fine-tuning selector, a digital command generated by that selector is converted into an analog compensating voltage subtracted from the output voltage of the frequency discriminator.

Low-noise digitally tunable phase-locked loop frequency generator

A test object, such as a communication path used for data transmission, is examined by applying to its input a measuring signal M consisting of several simultaneously or sequentially generated test frequencies which may be harmonically interrelated, extracting from the output of the test object a distorted version E of the measuring signal, locally generating a compensation signal K with frequency components matching respective test frequencies, and subtracting the two signals E and K from each other to obtain a residual signal R=E-K. The compensation signal K is produced by one or more local oscillators and as many frequency converters under the control of regenerating circuitry which locks each of its components in phase and amplitude to the corresponding test frequency. Regeneration takes place in a different frequency range to which the residual signal R is transposed and from which the compensation signal K is retransposed with the aid of a locally generated carrier. Various transmission coefficients can be derived from the three signals R, E, K as well as from control voltages produced in the regenerating circuitry for the amplitude lock.

Process and circuit arrangement for the measuring of coefficients of

A manually operated direct-current generator, with an output voltage whose polarity and magnitude depend on the direction and speed of rotation of a control knob, charges a storage capacitor in an input circuit of an operational amplifier which works into two comparators respectively responsive to positive and negative voltages exceeding selected thresholds. A triggerable pulse source, upon actuation by either comparator, feeds back one or more discharge pulses to the storage capacitor and also steps a reversible pulse counter in either a forward or a reverse sense.

Circuit arrangement for the control of a digitally settable load

A frequency generator of the digitally settable type comprises several voltage-controlled oscillators, specifically a pair of pilot oscillators and a final oscillator, provided with respective phase-locking loops each including a phase discriminator. The loops of the pilot oscillators further include respective frequency dividers whose step-down ratios are controlled by setting commands stored in associated memories which can be reloaded, under the control of manually or automatically adjustable selectors, only in the presence of an enabling pulse generated by a coincidence circuit with inputs connected to the outputs of a source of reference frequency and of the several stages of a chain of binary dividers connected to that source, certain of these stage outputs delivering comparison frequencies to the phase discriminators fed by the frequency dividers of the pilot oscillators. The phase discriminator associated with the final oscillator has one input connected to a mixer and another input connected to one of the pilot oscillators, the mixer receiving operating frequencies of the other pilot oscillator and of the final oscillator. A timing device such as a monoflop may be triggered by the enabling pulses for temporarily disabling the final phase discriminator, or restricting its dynamic range, to suppress fluctuations in the output frequency due to transient oscillator instability. The emission of such inhibiting pulses may be limited to switching operations involving both pilot oscillators, as upon the occurrence of a denominational carry.

Growing community of inventors

Eningen, Germany

Peter Harzer