Patent ID: 8140041

Claim:
A tunable capacitive device, comprising: a first tunable capacitive element, having a first node and a second node, wherein the first node of the first tunable capacitive element is coupled to a first voltage input terminal configured to receive a first input voltage; a first coupling capacitive element, having a first node and a second node, wherein the first node of the first coupling capacitive element is coupled to the second node of the first tunable capacitive element, and the second node of the first coupling capacitive element is coupled to a first connection terminal of the tunable capacitive device; a first coupling resistive element, having a first node and a second node, wherein the first node of the first coupling resistive element is coupled to the second node of the first tunable capacitive element, the second node of the first coupling resistive element is coupled to a second voltage input terminal configured to receive a second input voltage, one of the first input voltage and the second input voltage is a control voltage configured for tuning a capacitive value of the tunable capacitive device, and the other of the first input voltage and the second input voltage is a reference voltage; and a first specific capacitive element, coupled between the first node and the second node of the first tunable capacitive element, wherein the first specific capacitive element has one node directly connected to at least one of the first tunable capacitive element and the first coupling capacitive element.