Negative impedance converter

About: Negative impedance converter is a research topic. Over the lifetime, 5801 publications have been published within this topic receiving 87636 citations.

Half-bridge DC to DC converter with low output current ripple

Abstract: A method and apparatus for maintaining relatively low ripple current in a dc-dc converter while minimizing the size of an inductive line filter utilizes a transformer having at least a pair of secondary windings in which the secondary windings are selected to have different numbers of winding turns depending on the specific design of the ideal duty factor at which the converter will be operated. In addition, the converter is provided with an active pre-load which establishes a continuous conduction current when load current is below some selected minimum value in order to provide control stability during light load conditions without converter oscillations. In an illustrated embodiment, the active pre-load circuit comprises a resistor connected in series with a transistor across the voltage output of the converter with the gate terminal of the transistor connected through a zener diode to the control circuit so that when the control voltage feedback signal drops to a selected low value, the transistor is biased into conduction to connect the resistor as a load to maintain a minimum load current. Alternatively, the transistor can be connected across one of the diodes in the transformer secondary and arranged so as to conduct current in a direction opposite to the direction of current through the diode so that under low current conditions, a current loop is formed through the transformer to maintain continuous current flow and allow the converter to operate at very light loads.

Method for controlling the impedance of a driver circuit

Abstract: A method for controlling the impedance of drivers controls the output impedance of drivers by coupling the drivers to a impedance control circuit. Accordingly, a desired driver output impedance can advantageously be established and maintained over a wide range of variations in operating conditions and manufacturing processes. Thereby shortening the signal settling time and increasing the attainable signaling frequency.

Envelope modulator saturation detection using a DC-DC converter

Abstract: In an embodiment of the invention, a system provides for efficient polar and linear signal modulation. The system has a controller coupled to a voltage converter and a modulator. The system also has an amplifier coupled to the voltage converter and the phase modulator. The controller is for receiving an input and providing a polar signal. The voltage converter is for receiving the polar signal, receiving a voltage input, and providing a power signal. The amplifier is for amplifying the modulated signal based on the power signal. The voltage converter provides a feedback signal to the controller, and the controller adjusts a scale of modulation, such as a peak of the modulation signal, based on the feedback signal, such that the output power and the amplification by the amplifier are based on the feedback signal.

Broadband Fast-Wave Propagation in a Non-Foster Circuit Loaded Waveguide

Abstract: Frequency independent fast-wave (FW) propagation with phase velocity greater than the speed of light can be ideally realized in a dielectric medium whose relative permittivity is positive, but less than 1. Conventionally, FW propagation is implemented by non-TEM waveguides or antiresonance-based metamaterials, which suffers from the narrow bandwidth due to the dispersion. In contrast, non-Foster circuits provide a brand new method for reducing the dispersion so as to broaden the bandwidth. This paper demonstrates broadband FW propagation in a microstrip line that is periodically loaded with non-Foster circuits. Discrete transistor-based non-Foster circuits functioning as negative capacitors are successfully designed with the novel modified negative impedance converter circuits. A -10-pF negative capacitor over a bandwidth of 10-150 MHz has been implemented. The fabricated circuits have been integrated into a microstrip line to form a FW waveguide. The retrieved phase velocity of the effective medium from the measured S-parameters characterizes a stable and causal FW medium with constant phase velocity of 1.2c from 60 to 120 MHz, and this has been further verified by Kramers-Kronig relations and the near-field measurements along the waveguide. In conclusion, a stable, causal, and broadband FW waveguide has been achieved by means of transistor-based non-Foster circuits. The implemented broadband FW propagation can potentially be applied in broadband leaky-wave antennas and cloaking techniques.