Motorola Corporation

Virgilio A Fernandez

John Wayne Simmons

Gianfranco Gerosa

Norman T Rollins

John D Wetters

Steve Carsello

Art Ahrens

A method of calibrating a radio receiver (100) which has a desired IF center frequency (fo) includes generating and applying to the receiver's demodulator (126) a plurality of reference signals. The demodulated reference signals are used to generate, for the demodulator, a transfer function that is predictive of amplitude versus frequency characteristics of signals to be demodulated by the demodulator (126). The transfer function (202) is used to determine a frequency offset between a received signal's intermediate frequency and the desired frequency fo. The determined frequency offset is used to adjust the IF frequency of the received signal towards the desired frequency fo. The adjustment process preferably continues until the frequency offset is below a desired threshold. A receiver using the disclosed method is also described.

Radio receiver and method of calibrating same

A circuit (100) is provided which includes a forward charging switch (FET MN2) having an input terminal (102), an output terminal 112 and a plurality of current sink elements (FETs MN1 and MN3). The plurality of current sink elements (MN1 and MN3) are selectable via a control switch circuit (114) which is responsive to a control signal at the control switch input terminal (104). Preferably, one of the current sinks is always selected in order for some small amount of current to be discharged from output terminal 112 which is coupled to a capacitor (C1).

Circuit with adjustable release time

A CMOS differential amplifier or comparator circuit (100) is provided having minimized DC offset voltage. The circuit includes parallel coupled stages (110, 120, 130, 140, 150, 160) that are selectively controlled by an F.E.T. switch (182). The current through each stage is a function of its FET sizing. The current through the differential amplifier is adjusted by the selectively activated certain stages, which increase the current through differential amplifier (100), thereby adjusting the DC offset. The FETs in each stage are sized differently to allow flexibility in adjusting DC offset voltage.

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Sunrise, FL, United States of America

Virgilio A Fernandez