Microtune (texas), Inc.

General Instrument Corporation

Kevin John Lynaugh

Joel Stephen Michon

Hans Habermeier

Michael Andrew Grossman

Yong Zeng

Eric Mumper

An input section of an RF interface is shown in conjunction with a tuner circuit. The input, in one embodiment, is constructed using co-planner wave guide techniques and serves to provide low return loss, low insertion loss, high voltage protection, all within a single housing without causing RF interference problems.

Cable network interface circuit

A method for estimating the input power to a cable modem includes generating a look-up table containing AGC integrator accumulator values corresponding to selected frequencies and amplitudes. The look-up table is generated by first constructing a calibration matrix by inputting a plurality of calibration signals having known input frequencies and known input power levels into the cable modem's receiver, and recording AGC integrator accumulator values corresponding to several frequencies and power levels over a selected operating range as calibration points. Next, an interpolation and extrapolation process generates the look-up values corresponding to the frequencies and amplitudes in between the calibration points. During modem operation, the modem estimates the input power by checking the AGC integrator accumulator value corresponding to the input frequency and amplitude. Because the look-up table values are based on the cable modem's actual operating characteristics, the estimated input power will reflect any variations or irregularities in the modem's operation, such as gain non-linearities, frequency ripple, or temperature effects.

Method and system for estimating input power in a cable modem network

The present invention is directed to a system and method which utilizes a fixed base current to control the output voltage instead of a variable base current. In one embodiment, instead of modulating the base current, the converter uses output current to determine the voltage produced at the output. By sinking current out of the DC-to-DC converter, a high output impedance is achieved which, in turn, allows a fairly low modulating current to offer a large change in output voltage. This circuit eliminates at least one of the feedback loops found in existing designs, further increasing stability. As a result of the circuit design, there is achieved a DC-to-DC converter which allows the user to easily define the frequency at which the circuit operates and which is tolerant of component variations.

DC-to-DC converter providing stable operation

The gain characteristics of certain stages of a tuner circuit are selected to be proportional, but opposite, to selected other stages such that the overall gain of the tuner remains constant over a wide temperature range. In one embodiment, the gain of the IF stage has a temperature slope opposite to the temperature slope of the input RF stage thereby avoiding the use of AGC circuitry.

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Carlsbad, CA, United States of America

Kevin John Lynaugh