RF A/B switch with substantial isolation

An RF A/B switch associated with a receiver comprising:

• a first input;
• a second input;
• an output;
• a first circuit coupling the first input to the output, wherein the first circuit includes a first diode and a first impedance, and wherein the first diode is coupled between the first input and the output;
• a second circuit coupling the second input to the output, wherein the second circuit includes a second diode and a second impedance, and wherein the second diode is coupled between the second input and the output;
• a third diode coupling the first circuit to a reference;
• a fourth diode coupling the second circuit to a reference;
• and,
• a controller, wherein the controller is arranged to establish a biasing current common to both of the first and second circuits, wherein the biasing current forward biases the first and fourth diodes and reverse biases the second and third diodes so as to configure the first impedance as a low pass filter between the first input and the output and so as to configure the second circuit in a signal blocking state when a signal on the first input is to be coupled to the output, and wherein the biasing current reverse biases the first and fourth diodes and forward biases the second and third diodes so as to configure the second impedance as a low pass filter between the second input and the output and so as to configure the first circuit in a signal blocking state when a signal on the second input is to be coupled to the output.

An RF A/B switch associated with a receiver comprising:

• a first input;
• a second input;
• an output;
• a first diode circuit comprising a plurality of diodes and an impedance network coupled between the first input and the output;
• a second diode circuit comprising a plurality of diodes and an impedance network coupled between the second input and the output;
• a controller, wherein the controller is arranged to establish a common series biasing current through at least one of the diodes in each of the first and second diode circuits, wherein the common series biasing current biases one of the first and second diode circuits so as to configure a respective one of the impedance networks in a low pass filter configuration that couples a signal on one of the first and second inputs to the output, wherein the common series biasing current biases the other of the first and second diode circuits in a blocking configuration so as to block a signal on the other of the first and second inputs from the output, and wherein the other of the first and second diode circuits in the blocking configuration has an equivalent series impedance;
• and,
• a compensation impedance arranged to substantially cancel the equivalent series impedance at a predetermined frequency.