RF power amplifier employing bias circuit topologies for minimization of RF amplifier memory effects

An RF amplifier, comprising:

• an input receiving an RF input signal comprising an RF carrier and a modulation signal having a modulation bandwidth of at least 5 MHz;
• an active amplifier device receiving and amplifying the input signal to provide an output, the active amplifier device having a power supply connection;
• and
• a bias circuit coupled between a DC power supply and the active amplifier device power supply connection, the bias circuit comprising a network of circuit elements having an impedance versus frequency response having plural minima spaced across the modulation bandwidth and an impedance at said RF carrier frequency at least ten times the output impedance of said active amplifier device.

An RF amplifier, comprising:

• an input receiving an RF input signal;
• an active amplifier device receiving and amplifying the input signal to provide an output, the active amplifier device having a power supply connection;
• and
• a bias circuit coupled between a DC power supply and the active amplifier device power supply connection, the bias circuit comprising parallel power supply feed lines connected to the active amplifier device power supply connection and a plurality of decoupling capacitors coupled in a parallel configuration to a ground connection and electrically coupled to the DC power supply and the parallel power supply bias feed lines.

A method of amplifying an RF input signal, comprising:

• providing an input signal comprising a modulating signal having a video bandwidth and an RF carrier to an RF amplifier device having a power supply connection;
• providing DC power from a DC supply to said RF amplifier device power supply connection along parallel feed lines;
• and
• providing a low impedance to said supplied power across the video bandwidth and an impedance at least ten times the device output impedance at the frequency of the RF carrier.

A bias circuit for use with an amplifier having an active device power supply connection, comprising:

• a DC power supply connection;
• an RF blocking inductance;
• a first set of decoupling capacitors coupled in a parallel configuration to a ground connection and configured between the DC power supply and the RF blocking inductance;
• and
• a second set of one or more decoupling capacitors coupled to a ground connection and configured between the active device power supply connection and the RF blocking inductance.

An RF amplifier, comprising:

• an input receiving an input signal comprising an RF carrier and a modulation signal having a modulation bandwidth of at least 5 MHz;
• an active amplifier device receiving and amplifying the input signal to provide an output, the active amplifier device having a power supply connection;
• and
• a bias circuit coupled between a DC power supply and the active amplifier device power supply connection, the bias circuit comprising a network of circuit elements having an impedance versus frequency response having at least one minimum in the modulation bandwidth and a low impedance across the modulation bandwidth so as to minimize amplifier memory effects and a higher impedance from a parallel resonance close to said RF carrier frequency, wherein the impedance at said RF carrier frequency is at least ten times the output impedance of said active amplifier device.

A feed forward amplifier, comprising:

• an RF input for receiving an RF signal having an RF carrier and a modulation bandwidth of at least 10 MHz;
• a predistortion circuit receiving and predistorting said RF input signal;
• a main amplifier receiving and amplifying said predistorted RF signal, said main amplifier comprising an active device and a bias circuit coupled to a DC power supply, said bias circuit having a transfer function having a plurality of transmission zeros spaced across the modulation bandwidth so as to substantially eliminate amplifier memory effects;
• a main amplifier output sampling coupler;
• a first delay coupled to the RF input and providing a delayed RF signal;
• a carrier cancellation combiner coupling the delayed RF signal to the sampled output from the main amplifier;
• an error amplifier receiving and amplifying the output of the carrier cancellation combiner;
• a second delay coupled to the output of the main amplifier;
• an error injection coupler combining the output from the error amplifier and the delayed main amplifier output from the second delay so as to cancel distortion introduced by the main amplifier;
• and
• an RF output coupled to the error injection coupler output and providing an amplified RF output.