Programmable voltage controlled attenuator
AssigneeMotorola, Inc.
InventorsYi Fang, Cesar Carralero, Mark McEwen
Life of this patent
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Abstract
A programmable voltage controlled attenuator (100) meets the dynamic range and gain requirements for various communication protocols using a single bias generator circuit (104). A control voltage input, Vcnt, and a slope select input provide the dynamic range and attenuation for a voltage controlled attenuator (VCA) (109.).
Claims9
An integrated biasing circuit for a voltage controlled attenuator (VCA), comprising:
- a bias generator section receiving a slope select input voltage having first and second levels and an attenuation control voltage;
- a bandgap reference located within the bias generator section and providing a reference voltage;
- a variable resistive load located within the bias generator section and responsive to the slope select input voltage having first and second levels and providing first and second load impedances respectively;
- a variable current sink located within the bias generator section and responsive to the attenuation control voltage and the reference voltage;
- and
- said first and second load impedances and said variable current sink providing first and second differential voltage swings to the VCA.
A method of controlling dynamic range and gain in an integrated voltage controlled attenuator (VCA) circuit, comprising the steps of:
- setting a voltage reference;
- generating a control voltage from a digital to analog converter (DAC) operating over a predetermined control voltage range;
- providing first and second current sinks using the voltage reference and the control voltage;
- providing a variable impedance;
- providing a differential voltage using the variable impedance and the first and second current sinks;
- and
- supplying the differential voltage to the VCA;
- and
- controlling the dynamic range using the variable impedance and controlling the gain using the DAC.
An integrated programmable voltage controlled attenuator (VCA) circuit, comprising:
- a VCA;
- a bias generator coupled to the VCA including:
- a bandgap reference providing a reference voltage;
- a gain/slope control section for receiving a control voltage and comparing said control voltage to said reference voltage to generate first and second current sinks, the gain/slope control section also including a variable impedance, said variable impedance being responsive to a slope select input, said variable impedance and said first and second current sinks providing a differential voltage to the VCA;
- and
- said control voltage operates over a predetermined range, said predetermined range and said slope select input providing first and second predetermined differential voltage swings to the VCA.
A radio, comprising:
- an offset phase locked loop (PLL) for generating an offset radio frequency (RF) signal;
- a modulator for receiving a base band signal and modulating said base band signal with said offset RF signal and generating a modulated RF signal;
- a programmable voltage controlled attenuator (VCA) for receiving the modulated RF signal and providing an attenuated modulated RF signal;
- said programmable VCA including, a bias generator having a slope control input and a control voltage range input for providing a predetermined number of differential voltage swings, each differential voltage swing providing a predetermined slope and dynamic range for a predetermined number of communication protocols, said programmable VCA also including a VCA for receiving each differential voltage swing and biasing said modulated RF signal using each predetermined voltage swing;
- and
- a wideband amplifier for receiving the attenuated modulated RF signal and generating an RF carrier signal.
Dependencies are inferred from the claim text.