John Fluke Mfg. Co., Inc.

Fluke Corporation

Metawave Communications Corporation

Datacom Technologies, Inc.

Eric R Drucker

Jeffrey Sandsmark Bottman

Tzafrir Sheffer

Steven P Cok

Frederick J Telewski

Richard Chesarek

Lannes S Purnell

Chuck C Hanna-Myrick

John D Moser

A system and method for providing distributed amplification of a plurality of input signals is disclosed. The preferred embodiment of the disclosed invention utilizes two signal path matrixes having signal combiners, hybrid combiners, and phase shifters to dissect an input signal for amplification and subsequent recombination. The unique matrixes disclosed provide for the distributed amplification of any number of input signals factorable as a product of prime numbers including an odd prime number factor, therefore reducing the number of linear power amplifiers required where a number of input signals other than a power of two are used.

Signal feed matrix amplifier reduction system and method

A test instrument (50) for testing a cable (52), the test instrument having a main unit (54) and an interchangeable performance module (56). The main unit of the test instrument contains signal generators for generating AC and DC test signals. The AC test signals are generated as single-ended signals and applied to a pair selection switching array (76). The pair selection switching array switches the single-ended test signals to a plurality of lines (84a-84d) that couple to the performance module. The performance module is an interchangeable module having a plurality of balancing networks (baluns) (102a-102d) that are connected to the plurality of lines. Single-ended test signals applied to the baluns are converted into balanced signals and applied to a cable being tested. The performance module may be interchanged to allow the main unit to be connected to cables having various impedances and connectors. The conversion to a balanced signal after the switching array improves the test instrument accuracy and allows the switching array to be constructed of transistors.

Cable test instrument having interchangeable performance modules

A cable crosstalk measurement system provides fault diagnostic information to locates faults in addition to providing a crosstalk versus frequency function to test and troubleshoot LAN cables. In a preferred embodiment, a narrow pulse is introduced into one twisted pair of a standard LAN cable, and another twisted pair in the same cable is monitored for crosstalk signal coupling. A measurement system digitizes crosstalk signals using sequential sampling of repetitive signals to provide a waveform record that is a reconstructed equivalent time representation of a real-time crosstalk signal. A microprocessor performs a fast Fourier transform of the waveform record to provide crosstalk versus frequency information, while the waveform record is also examined for higher-than-acceptable amplitude levels to locate poor quality or faulty connectors and cables.

Cable crosstalk measurement system

Method and apparatus for improving the signal-to-noise ratio of a divide-by-N phase-locked loop includes a variable divider circuit to provide a plurality of feedback signals of substantially equal phase. Each of the plurality of feedback signals includes a signal component and a noise component wherein the signal components of the plurality of feedback signals have substantially equal phase and wherein the noise components of the plurality of feedback signals are not substantially correlated. A respective plurality of control circuits is provided to combine the plurality of feedback signals with a reference signal to provide a plurality of control signals wherein each control signal is a substantially direct current voltage the magnitude of which is proportional to the phase difference between the reference signal and the feedback signal which comprised its origin. The plurality of control signals are added to provide a composite control signal so that the signal components of the plurality of control signals add by linear superposition and so that the noise components of the plurality of control signals add by the square root of the sum of their squares, thereby substantially improving the signal-to-noise ratio of the phase-locked loop output.

Noise reduction method and apparatus for phase-locked loops

A coherent direct digital waveform synthesizer, capable of generating a waveform in response to a decimally or other non-binary related reference frequency while obtaining the advantages of the use of a binary radix phase accumulator generating binary addresses for a waveform memory. The interface between these elements include a frequency converter including a voltage controlled oscillator and a further binary radix phase accumulator in the feedback path of a phase locked loop. A binary radix related digital waveform synthesizer may be thus made to produce non-binary related frequency waveforms coherent with a non-binary radix reference frequency source, and of decimal or other non-binary radix related resolution.

Coherent direct digital synthesizer

A three modulus prescaler for a phase-locked loop frequency synthesizer includes a N.sub.0 modulus prescaler inputting into a divide-by-two circuit. A microprocessor and internal logic control a three modulus prescaler synchronizer to receive signals from the divide-by-two circuit and output control commands to the N.sub.0 modulus prescaler so as to cause the N.sub.0 modulus prescaler to divide solely by a first or second modulus, or alternately between said first and second modulus, between output pulses of the divide-by-two circuit to extend the synthesizer's bandwidth.

Multiple-multiple modulus prescaler for a phase-locked loop

A phase-locked loop is disclosed that exhibits flat modulation characteristics over a wide range of carrier frequencies for either frequency or phase modulation at rates that are both within and outside the loop bandwidth. The disclosed arrangement is a programmable divide-by-N phase-locked loop frequency synthesizer wherein the feedback path includes a second phase-locked loop that serves as a tracking filter. Modulation is supplied to the main phase-locked loop via a first modulation path that couples the modulating signal to the frequency control terminal of the phase-locked loop voltage-controlled oscillator and via a second modulation path that couples the modulating signal to the phase-locked loop phase detector. To configure the system so that flat modulation is attained, the gain factors of the first and second modulation paths are established in accordance with specific relationships and the second modulation path includes a compensator network having a transfer function that at least aproximates that of the phase-locked loop which is embedded in the system feedback path. Additionally, the modulation signal coupled to both modulation paths is adjusted on the basis of carrier frequency to compensate for frequency-related variation in the transfer characteristics of the main loop VCO. The transfer characteristic of the main loop phase detector is controlled to maintain a constant loop bandwidth.

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Seattle, WA, United States of America

Eric R Drucker