A low cost and low power adaptive cable equalizer that is particularly suitable for fast Ethernet data communication is disclosed. According to various embodiments of the present invention, first and second order adaptive equalizers are implemented using CMOS continuous-time analog signal processing, with variable resistors, linear capacitors and high-speed operational amplifiers.

Analog adaptive line equalizer

A switched capacitor circuit is described which is programmable so that its function can be set by a user. Thus, control circuitry and selection circuitry are provided to enable one of a plurality of alternative control signals to be provided to switch circuits of the switched capacitor circuit. In this way, the function of the switched capacitor circuits can be altered. Where there are a plurality of switched capacitor circuits connected in an array, the topology of the array can be altered by suitably routing particular input signals to particular outputs by selecting the control signals to control the switched circuits. A field programmable array of this type is also described.

Programmable switched capacitor circuit

An electronic compensation network which allows the analytic and empirical realization of the compensation needed to optimize a system response. The electronic compensation network includes a switched capacitor active filter network; means for selectively changing filter characteristics; and, means for indicating the characteristics of the compensator which produces an optimized system response.

Electronic compensation network

In the comparator circuit, the amplifier circuit (6) is comprised of an inverting amplifier section (21) having a high gain and a noninverting amplifier section (22) having a low output impedance. Therefore, the comparator circuit has a high input sensitivity. The comparator circuit also can operate at a high speed.

Voltage comparator circuit

The present invention is related to an adaptive equalizer comprising multiple tuning circuits that generate tuning signals. Each tuning signal can typically induce higher frequency gain up to a limited level, e.g. +5dB, at the upper data frequency for compensation of high frequency losses in the connected transmission channel. Several tuning signals can tune one adaptive amplifying compensation stage. In its adaptive amplifying compensation stage the tuning signal can generate through its tuning function, non-linear small-signal and large-signal transfer behaviour. However, by limiting the amount of higher frequency gain to maximum +8dB per tuning function, and by having only one tuning function active at a time the resulting deterministic fitter remains tolerable. Several adaptive amplifying compensation stages introducing non-linear effects in the compensation behaviour and their tuning functions are disclosed. Especially at low power supply voltage the merits of the present invention become apparent.

Low voltage multistage adaptive equalizer

The variable switched-capacitor filter (VSCF) comprises an input terminal (101), an output terminal (104) and first and second variable switched-capacitor filter blocks (102 and 103, resp.) each having a plurality of capacitors. In each of the filter blocks (102, 103) at least one of the filters is selected in response to a control signal for changing the filter characteristic based on the selected capacitor or capacitors. A first switch (SA) delivers during a first state a first output signal from the first variable switched-capacitor filter block (102) to the output terminal (104), and during a second state, prohibits the first output signal from reaching the output terminal (104). The function of the second switch (SB) is essentially opposite to that of the first switch (SA). The selection of at least one capacitor in the first and the second variable switched-capacitor filter block (102 and 103, resp.) is performed during the second and the first state, respectively. The VSCF accomplishes automatic line equalization without being affected by waveform distortions which result from switching the filter characteristic.

Nakayama Kenji

Papers

Variable switched-capacitor filter capable of changing the filter characteristic thereof