Lucent Technologies Inc.

Simon Hamparian

Michael Gordon Kossor

Adam Joseph O'Donnell

Temperature compensation of LDMOS devices as are employed in high power amplifiers follows from replacing the voltage source and resistive divider that feed the sensing diode of prior art temperature compensators for transistor amplifiers, with a current source feeding the sensing diode in a manner that is substantially independent of voltage variations which follow from temperature change. Such current variations as result from temperature change, in the circuit of the invention, produce variations in the bias voltage at the gate of the LDMOS power transistor which are many times less than the temperature coefficient of the LDMOS device, in producing virtually error-free temperature compensation.

Temperature compensation of LDMOS devices

A phase shifter circuit shifts the phase of a voltage varying RF signal at high RF power levels by using a diode arrangement of back to back diode sets connected in series to reduce the change in capacitive reactance of the diode arrangement. The diode arrangement is connected to a phase adjustment port of a phase shifting device which shifts the phase of the RF signal according to the capacitive reactance level at the phase adjustment port. A control circuit for each back to back diode set can be used to provide independent adjustment of each diode set to balance capacitive reactance responses between the diode sets to further reduce the change in capacitive reactance. In certain embodiments, the phase shifter circuit uses a ninely (90) degree hybrid coupler with two phase adjustment ports, a zero (0) degree port and a -90 degree port. A first diode arrangement of back to back diode sets is connected to the zero degree port, and a second diode arrangement of back to back diode sets is connected to the -90 degree port. Each diode arrangement includes at least a first set of back to back diodes (common cathode) connected in series which a second set of back to back diodes. Using the diode arrangements with multiple back to back diode sets reduces the change in the capacitive reactance of the diode arrangement at high RF signal power levels with wide voltage swings. Additionally, providing each back to back diode set with corresponding control circuitry allows independent adjustment of the capacitive reactance associated with each diode set, providing improved balancing of the capacitive reactance responses between and within the diode arrangements.

Phase shifter circuit with high linearity

In an amplifier apparatus of the type including an RF power transistor output stage, the control circuitry of the invention provides an automatic gain control mode of operation for its power transistor of a first response time and a power limiting mode of operation for its transistor of a second, faster response time, and with the power limiting mode of operation being switched into effect in response to the sensing of the collector current flow of the power transistor beyond a prescribed value.

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Palisades Park, NJ, United States of America

Simon Hamparian