# US 5,703,909 A · Programmable voltage controlled attenuator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,703,909 A - Document ID: US5703909A - Status: Granted - Kind: A - Application number: 08/698,837 - Filed: 1996-08-16 - Granted: 1997-12-30 - Earliest claimed: 1995-01-30 - Assignees: Motorola, Inc. - Inventors: Yi Fang; Cesar Carralero; Mark McEwen - Web page: https://patentgrep.com/patent/US5703909A ## CPC - H04L 27/367: {using predistortion} - H03G 1/0023: {in emitter-coupled or cascode amplifiers (H03G1/0029 takes precedence)} - H04L 27/0002: {analog front ends; means for connecting modulators, demodulators or transceivers to a transmission line (duplex arrangements H04L5/143)} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H03G: CONTROL OF AMPLIFICATION ## 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.). ## Claims ### Claim 1 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. ### Claim 2 (depends on 1) An integrated biasing circuit for a VCA as described in claim 1, wherein the first differential voltage swing provides a predetermined dynamic range for a first communication protocol while the second differential voltage swing provides a predetermined gain for a second communication protocol. ### Claim 3 (depends on 2) An integrated biasing circuit for a VCA as described in claim 2, wherein the first communication protocol is a code division multiple access (CDMA) protocol and the second communication protocol is a public access communication system (PACS) protocol. ### Claim 4 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. ### Claim 5 (depends on 4) A method as described in claim 4, further comprising the steps of: controlling the variable impedance with a serial peripheral interface port to provide first and second impedances; providing a first dynamic range and a first gain in response to the control voltage range and the first impedance; and providing a second dynamic range and a second gain in response to the control voltage range and the variable impedance. ### Claim 6 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. ### Claim 7 (depends on 6) An integrated programmable VCA circuit as described in claim 6, wherein the gain/slope control section comprises a switching transistor pair including resistive loads coupled through diode drops to a differential transistor pair, said differential transistor pair biased by the reference voltage and the control voltage, and said switching transistor pair biased by the slope select input. ### Claim 8 (depends on 7) An integrated programmable VCA circuit as described in claim 7 wherein the differential transistor pair comprises N-channel metal oxide field effect transistors (MOSFETs) and the switching transistor pair comprises P-channel MOSFETs, and the diode drops comprise bipolar npn transistors. ### Claim 9 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.