High isolation RF power amplifier with self-bias attenuator

A high isolation RF power amplifier comprising:

• a HBT RF power amplifier having a RF signal input;
• a diode having an anode and a cathode, the anode electrically coupled to the RF signal input and the cathode electrically coupled to ground;
• a variable current source having a power amplifier control voltage input and having a DC current output, the DC current output being electrically coupled to the anode;
• and
• a switching device electrically coupled between the cathode and ground.

A high isolation RF power amplifier comprising:

• a RF power amplifier having a RF signal input and a RF signal output;
• diverting means for diverting a desired portion of a RF signal to ground and away from the RF signal input;
• and
• controlling means for varying the desired RF signal portion diverted to ground in response to a power amplifier control signal to generate an attenuated RF signal such that a predetermined isolation is achieved between the RF signal input and the RF signal output.

A high isolation RF amplifier comprising:

• a RF amplifier having a RF signal input;
• a RF signal path associated with the RE signal input, the RF signal path having a predetermined attenuation characteristic;
• current generating means for providing a variable DC current having a value determined by a RF power amplifier control voltage;
• and
• means responsive to the current generating means for changing the attenuation characteristics associated with the RF signal path in response to the variable DC current wherein the attenuation characteristics are dependent upon the value of the DC current necessary to substantially eliminate self-biasing of the RF amplifier when the RF amplifier is not in a forward gain operating mode.

A method for eliminating self-biasing in a bipolar radio frequency amplifier, said method comprising the steps of:

• (a) providing a bipolar radio frequency amplifier having a radio frequency signal input;
• (b) electrically coupling a PIN diode attenuator to the radio frequency signal input;
• (c) providing a radio frequency amplifier control voltage;
• (d) providing a variable current source capable of allowing transmission of a current to the PIN diode in response to the radio frequency amplifier control voltage;
• and
• (e) transmitting a first predetermined current from the variable current source to the PIN diode in response to a selected radio frequency amplifier control voltage such that no more than sufficient radio frequency signal attenuation is achieved at the signal input to substantially eliminate self-biasing of the bipolar radio frequency power amplifier during transmission of large radio frequency signals to the radio frequency signal input when the radio frequency amplifier is in its off mode.