Texas Instruments Corporation

The Texas A&m University System

Roberto Sadkowski

Carl Michael Panasik

Henry F Taylor

Heino Jean Wendelrup

Chung E Lee

John M Muza

Steve Wiyi Yang

Martin Sallenhag

A wireless user terminal () and system () implementing a mixed signal CODEC () including an improved sigma-delta ADC () which limits input signals into a switched capacitor configuration and avoids adding circuit overhead in the signal path is disclosed herein. This sigma-delta analog-to-digital converter (), having an input signal and an output signal, includes a switch (sw), a clipping circuit (), and a known sigma-delta ADC (). It solves the clipping signal problem by limiting the signal right at the input of the sigma-delta ADC (). The clipping circuit () couples to the switch (sw) and the sigma-delta ADC () for switching the voltage applied to the sigma-delta ADC between the input signal (v) and at least one threshold voltage (Vand V).

Wireless user terminal and system having signal clipping circuit for switched capacitor sigma delta analog to digital converters

A microphone bias current detection circuit includes: a microphone circuit ; an amplifier having a first output and a second output, the first output is coupled to the microphone circuit for providing a bias current to the microphone circuit , the second output provides a sampled current I proportional to the bias current; a first switch having a first end coupled to the second output of the amplifier ; a resistor having a first end coupled to a second end of the first switch ; and a second switch coupled between the first end of the resistor and a reference current source.

Microphone bias current measurement circuit

A mixed signal CODEC including an improved sigma-delta ADC ( ) which limits input signals into a switched capacitor configuration and avoids adding circuit overhead in the signal path is disclosed herein. Additionally, it avoids overshoot and settling problems. This sigma-delta analog-to-digital converter ( ), having an input signal and an output signal, includes a switch (sw ), a clipping circuit ( ), and a known sigma-delta ADC ( ). It solves the clipping signal problem by limiting the signal right at the input of the sigma-delta ADC ( ). The clipping circuit ( ) couples to the switch (sw ) and the sigma-delta ADC ( ) for switching the voltage applied to the sigma-delta ADC between the input signal (v ) and at least one threshold voltage (V and V ).

Signal clipping circuit for switched capacitor sigma delta analog to digital converters

A mixed signal codec includes: a multiplexer amplifier,having an analog output signal; a sigma-delta analog to digital converter,having an input coupled to the analog output signal; and a clipping circuit,and,coupled to the input of the analog to digital converter for clipping the analog output signal.

Analog clipping circuit for mixed signal codecs

Apparatus and method (10, 50) for determining the value of a measurand measured by a fiber optic interferometer sensor (24, 72, 110) is provided. The apparatus includes a light source (16, 58, 102) emitting a light having a periodically modulated frequency which is injected into the interferometric sensor. A modulation cycle is initiated by the microcontroller's (12, 56, 116) generation of a trigger signal. A counter (42, 86) begins counting in response to the trigger signal. A first photodetector (20, 66) is coupled to the light source (16, 58, 102) and produces a first electrical signal proportional to the light. A second photodetector (36, 76, 114) is coupled to the fiber optic interferometer sensor (24, 72, 110) and produces a second electrical signal proportional to the light reflected by the sensor or passed through the sensor and affected by the measurand. A comparator (40, 82, 116) compares the second electrical signal with the first electrical signal and detects a crossing of the first and second electrical signals. The counter (42, 86) stops counting in response to a detected signal crossing. The microcontroller (12, 56, 116) then computes a measurand value from the count value for each modulation cycle.

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Plano, TX, United States of America

Roberto Sadkowski