Topic Semiconductor Corp.

Industrial Technology Research Institute

Jean-Ming Lee

Chu-Chiao Yu

Claymens Lee

Her-Y Shih

Shaw-Jia Hor

An apparatus of a digital echo canceller and method therefor, a designed selector is used values of receiving and input signals to estimate the length of a cable. The response values of an insignificant part of the echo signal can be selected. Multiplication and addition operations are carried out in a response region of a significant part of the echo signal. An estimated echo signal is produced to cancel the echo signal, unnecessary operations and the cost of a hardware can be reduced.

Apparatus for a digital echo canceller and method therefor

A voltage-controlled oscillator comprising a voltage compensation transistor is disclosed. The voltage compensation transistor is able to provide an equivalent resistance to the bias voltage supplied to the oscillator. When a sudden raise in the voltage of the power supply takes place, the equivalent resistance of the compensation transistor will drop, such that the bias voltage supplied to the oscillator may be pulled down, whereby the oscillation frequency of the ring oscillator may be adjusted.

Voltage-controlled oscillator

The present invention discloses a biquadratic switched-capacitor filter, which merely utilizes one operational amplifier to implement a biquadratic transfer function. The biquadratic switched-capacitor filter further comprises ten switched-capacitor circuits, two feedback capacitors, and two individual switching devices. The switching devices in this switched-capacitor filter can be controlled by six different clock signals. The first and second clock signals are two-phase, complementary but non-overlapping pulse trains with a reference period. The third clock signal is a pulse train with double the reference period and coincident with the first clock signal. The fourth, the fifth, and the sixth clock signals are pulse trains that result from delaying the third, the fourth, and the fifth clock signals by half the reference period. The obtained switched-capacitor filter can be used to simplify some applications, such as sigma-delta modulators.

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Hsinchu, Taiwan

Jean-Ming Lee