Variable resistance attenuator
AssigneeThe United States of America as represented by the Secretary of the Army
InventorAnthony Abajian
Life of this patent
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Abstract
Four PIN diodes are connected, two in parallel oppositely directed at each f two ports of a 3 dB, quadrature hybrid which equally divide the power from an input port. The mismatch produced by the PIN diode resistance in parallel with the matching load resistance reflects part of the power, which combines at the two ports and exits at a fourth port of the hybrid. Direct-current bias to the PIN diodes is adjusted to vary the attenuation. There is also variable resistance and capacitance which serves as variable adjustments on the terminations of the hybrid when the diodes are unbiased.
Claims3
A variable resistance attenuator comprising:
- quadrature hybrid means having an input port, an output port, and at least first and second other ports, such that radio frequency power applied at the input port divides equally between the first and second other ports, and the output port is isolated;
- at least four PIN type diodes whose radio-frequency resistance is a function of their direct-current bias coupled to said first and second other ports, with first and second of said diodes in parallel coupled between the first other port and ground, and third and fourth of said diodes in parallel between the second other port and ground, adjustable bias means to supply direct current through said diodes to control the resistance thereof;
- and termination impedance means coupled between said first and second other ports and ground, comprising a plurality of impedance elements, including an adjustable resistor coupled to said first other port, and an adjustable capacitor in parallel with a fixed resistor coupled to said second other port, to match the characteristic impedance of the hybrid when the diodes are unbiased.
Dependencies are inferred from the claim text.