Amplifier providing power recovery from a narrow-band antenna

An amplitude modulated amplifier for amplifying a radio frequency (RF) signal, the amplifier comprising:

• four selectably controllable transistors arranged to receive power from a direct current (DC) power supply to amplify the signal, the transistors configured in a bridge configuration with a first and a second transistor coupled between the DC power supply and an antenna having a short electrical length compared to a wavelength of a transmitted signal, and with a third and a fourth transistor coupled between the antenna and ground in an ‘H’ configuration, each transistor having a gate input to determine the state of the transistor between an on state and an off state;
• four diodes each associated with one of the four transistors and forward biased from a source to a drain of each transistor, forming a bridge rectifier;
• and
• drive logic for controlling each of the four transistors from an open state to a closed amplifying state based on external input, wherein the drive logic is selectable from a driving state to a damping state of the amplifier by switching transistors to recover power from the antenna when an impedance state of the antenna is negative, and to deliver the recovered power to the DC power supply.

A system for transmitting radio frequency signals into an antenna having a short electrical length compared to a wavelength of a transmitted signal, the system comprising:

• a signal source providing a baseband source signal to be amplified and modulated before transmission;
• an exciter module for up-converting the source signal based on a frequency of a received RF source;
• an amplification module comprising one or more amplifier, each amplifier comprising:
• four selectably controllable transistors arranged to receive power from a direct current (DC) power supply to amplify the up-converted source signal, the transistors configured in a bridge configuration with a first and a second transistor coupled between the DC power supply and an antenna, and a third and fourth transistors coupled between the antenna and ground in an ‘H’ configuration, each transistor having a gate input to determine the state of the transistor between an on state and an off state;
• four diodes each associated with one of the four transistors and forward biased from a source to a drain of each transistor, forming a bridge rectifier;
• drive logic for controlling each of the four transistors from an open state to a closed amplifying state based on external input, wherein the drive logic is selectable from an active state to a damping state of the amplifier by switching transistors to recover power from the antenna when an impedance state of the antenna is negative, and to deliver the recovered power to the DC power supply;
• a power source for delivering DC power to the amplification module or receiving and storing power from the amplification module;
• an antenna coupled to the amplification module, the antenna having a highly capacitive characteristic wherein the signal wavelength is less than the antenna wavelength, wherein current is delivered from the amplification module to the antenna when in the driving state and impedance is positive, and current is received from the antenna and delivered to the DC power source in the damping state when impedance is negative;
• and
• a controller coupled to or integrated with the exciter module, for controlling the operation of the one or more amplifiers via the drive logic, wherein a subset of the one or more amplifiers is switched between the driving state or damping state, wherein any remaining amplifier(s) of the one or more amplifiers are placed in an inactive mode, to control the modulation of the transmitted signal.