A radio frequency (RF) amplifier configured to operate at a fundamental frequency (f.sub.0) includes a transistor with a transistor output, an output matching network coupled to the transistor output, and a reflection absorption circuit. The output matching network includes an output path device connected between the transistor output and an output of the RF amplifier. The reflection absorption circuit is coupled between the transistor output and the output path device, and is configured to absorb reflected signal energy from the output path device.

A wireless communication node and method therein for generating beamformed signals by means of backscattering in a wireless communication network are disclosed. The wireless communication node receives a radio frequency signal at a plurality A of antennas. Each antenna is coupled to one of a number of impedance matrices by one of a plurality A of switches. The wireless communication node generates a first baseband signal based on data symbols to be transmitted in a baseband signal generator. The states of each switch are controlled based on its specific switch control signal such that each antenna impedance is selected among a number M of impedances, and thereby the received RF signal at each antenna is modulated by the first baseband signal with its specific phase and reflected. The beamformed signals are generated by the plurality A of antennas by reflecting the modulated RF signals from each antenna.

A wireless communication node and method therein for generating beamformed signals by means of backscattering in a wireless communication network are disclosed. The wireless communication node receives a radio frequency signal at a plurality A of antennas. Each antenna is coupled to one of a number of impedance matrices by one of a plurality A of switches. The wireless communication node generates a first baseband signal based on data symbols to be transmitted in a baseband signal generator. The states of each switch are controlled based on its specific switch control signal such that each antenna impedance is selected among a number M of impedances, and thereby the received RF signal at each antenna is modulated by the first baseband signal with its specific phase and reflected. The beamformed signals are generated by the plurality A of antennas by reflecting the modulated RF signals from each antenna.

Present invention is an antenna system and a wireless device comprising a negative resistance amplifier, the antenna system further comprises a first antenna element, said first antenna element being adapted to receive an incident wave for generating a first signal proportional to the incident wave, wherein the antenna system comprises a signal generating device for generating a second signal that is essentially 90 degrees phase shifted to the first signal, the first signal and the second signal being adapted to be applied to a hybrid coupler such that the first signal and the second signal are adapted to essentially destructively combine at a first hybrid coupler port, and the first signal and the second signal are adapted to be essentially constructively combined at a second hybrid coupler port, the second hybrid coupler port being adapted to operatively connect to the negative resistance amplifier, and the first hybrid coupler port being adapted to connect to a termination unit. Please invention is also a method for reflection of an incident wave.

A radio frequency (RF) amplifier configured to operate at a fundamental frequency (f.sub.0) includes a transistor with a transistor output, an output matching network coupled to the transistor output, and a reflection absorption circuit. The output matching network includes an output path device connected between the transistor output and an output of the RF amplifier. The reflection absorption circuit is coupled between the transistor output and the output path device, and is configured to absorb reflected signal energy from the output path device.

A multiport microwave device includes a first reactive three-port microwave device, a second reactive three-port microwave device, a third reactive three-port microwave device, and a matched four-port microwave device. The four-port microwave device includes first and second input ports and first and second output ports communicatively coupled to one another. A first port of each of the first, second and third three-port microwave devices is operative to receive a microwave signal, and a first output port and a second output port of the four-port microwave device are each operative to output a microwave signal. A second port of the first microwave device is communicatively coupled to a second port of the second microwave device, a second port of the third microwave device is communicatively coupled to a third port of the second microwave device, and a third port of the first microwave device is communicatively coupled to the first input port the four-port microwave device. A third port of the third microwave device is communicatively coupled to the second input port of the four-port microwave device.

A multiport microwave device includes a first reactive three-port microwave device, a second reactive three-port microwave device, a third reactive three-port microwave device, and a matched four-port microwave device. The four-port microwave device includes first and second input ports and first and second output ports communicatively coupled to one another. A first port of each of the first, second and third three-port microwave devices is operative to receive a microwave signal, and a first output port and a second output port of the four-port microwave device are each operative to output a microwave signal. A second port of the first microwave device is communicatively coupled to a second port of the second microwave device, a second port of the third microwave device is communicatively coupled to a third port of the second microwave device, and a third port of the first microwave device is communicatively coupled to the first input port the four-port microwave device. A third port of the third microwave device is communicatively coupled to the second input port of the four-port microwave device.

Exemplary impedance matching circuit for an amplifier device comprises a broadband impedance transformer configured to transform, over a fundamental frequency range, an impedance associated with an input port or an output port of the impedance matching circuit; and to transmit RF signals having a fundamental frequency within the fundamental frequency range. The impedance matching circuit also includes a phase shifter circuit configured to transmit, with substantially matched impedance, the RF signals having a fundamental frequency within the fundamental frequency range, and to phase-shift higher-order harmonics of the RF signals. The impedance matching circuit also includes a high-pass impedance transformer configured to match an impedance of the RF signals having a fundamental frequency within the fundamental frequency range; and to transmit, with low reflection, second-order harmonics of the RF signals. Exemplary embodiments also include amplifier circuits comprising an RF amplifier and embodiments of the impedance matching circuit.

A low-noise directional amplifier includes a first port, a second port, a first coupler and a second coupler. The first port is coupled to a first coupler. The low-noise directional amplifier also includes at least two phase preserving amplifiers, a first phase preserving amplifier connected to the first coupler and a second coupler, and the second phase preserving amplifier connected to the first coupler and the second coupler.

Present invention is an antenna system and a wireless device comprising a negative resistance amplifier, the antenna system further comprises a first antenna element, said first antenna element being adapted to receive an incident wave for generating a first signal proportional to the incident wave, wherein the antenna system comprises a signal generating device for generating a second signal that is essentially 90 degrees phase shifted to the first signal, the first signal and the second signal being adapted to be applied to a hybrid coupler such that the first signal and the second signal are adapted to essentially destructively combine at a first hybrid coupler port, and the first signal and the second signal are adapted to be essentially constructively combined at a second hybrid coupler port, the second hybrid coupler port being adapted to operatively connect to the negative resistance amplifier, and the first hybrid coupler port being adapted to connect to a termination unit. Please invention is also a method for reflection of an incident wave.