Transmission-line filtering with enhanced frequency response

An apparatus for enhancing a frequency response of a filtering operation, the apparatus comprising:

• a transmission-line filter including:
• an input port;
• an output port;
• multiple transmission lines disposed between the input port and the output port, the multiple transmission lines including:
• a first transmission line electrically coupled between the input port and a ground;
• a second transmission line electrically coupled between the output port and the ground, the second transmission line having a proximal end and a distal end;
• and
• a third transmission line disposed between the first transmission line and the second transmission line;
• and
• a capacitor electrically coupled to the distal end of the second transmission line, wherein the proximal end of the second transmission line is closer to the output port than is the distal end of the second transmission line;
• the transmission-line filter includes an inductor coupled between the distal end of the second transmission line and the ground;
• and
• the inductor and the capacitor are coupled together in parallel between the distal end of the second transmission line and the ground,
• wherein the first transmission line has another proximal end and another distal end;
• and
• the capacitor is electrically coupled between the distal end of the second transmission line and the another distal end of the first transmission line.

A method for operating a transmission-line filter with enhanced frequency response, the method comprising:

• accepting an incoming signal at an input port;
• propagating the incoming signal from the input port along at least one signal pathway to an output port to produce a filtered signal, the propagating including:
• applying the incoming signal to a first transmission-line base unit including a first transmission line;
• applying the incoming signal to a second transmission-line base unit including a second transmission line, the applying including generating multiple resonant frequencies using the second transmission-line base unit, wherein the first transmission-line base unit and the second transmission-line base unit share a common capacitor that bridges the first transmission-line base unit and the second transmission-line base unit, the generating including establishing a parallel resonance between the second transmission line and a ground for the multiple resonant frequencies using at least one inductor and the common capacitor that are coupled to a distal end of the second transmission line;
• and
• applying the incoming signal to a third transmission-line base unit including a third transmission line;
• and
• forwarding the filtered signal from the output port.

An apparatus for enhancing a frequency response of a filtering operation, the apparatus comprising:

• a transmission-line filter including:
• a plurality of electromagnetically coupled transmission lines coupled between an input of the transmission-line filter and an output of the transmission-line filter, the plurality of electromagnetically coupled transmission lines including:
• a first transmission line;
• a second transmission line;
• and
• a third transmission line;
• a first inductor coupled between the first transmission line and ground, wherein a first end of the first transmission line is coupled to at least one of the input of the transmission-line filter or the output of the transmission-line filter, wherein the first inductor is coupled between a second end of the first transmission line and ground;
• a first capacitor coupled in parallel with the first inductor and coupled in series to a second inductor;
• and
• a second capacitor coupled between ground and the first end of the first transmission line.