Circuitry with Transmission Line-Based Signal Attenuators

A radio-frequency signal attenuator disposed on a signal line and comprising:

• a transmission line extending from a first terminal to a second terminal, the first terminal being coupled to an input of the radio-frequency signal attenuator and the second terminal being communicatively coupled to an output of the radio-frequency signal attenuator;
• a first adjustable resistance that couples the first terminal to a ground;
• and
• a second adjustable resistance that couples the second terminal to the ground, wherein the transmission line has a length from the first terminal to the second terminal that is configured to match an input impedance of the radio-frequency signal attenuator to an impedance of the signal line.

An electronic device comprising:

• a signal path configured to convey a radio-frequency signal;
• an attenuator disposed on the signal path, wherein the attenuator is configured to attenuate the radio-frequency signal and includes first and second adjustable shunt resistances;
• and
• a controller configured to adjust a magnitude of the first and second adjustable shunt resistances, wherein the controller includes
• an operational amplifier having an output communicatively coupled to the first and second adjustable shunt resistances,
• a set of transistors having gate terminals communicatively coupled to the output of the operational amplifier, and
• a servo loop extending around the operational amplifier from the output of the operational amplifier to a first input of the operational amplifier through the set of transistors.