RF filtering circuitry

Radio frequency (RF) filtering circuitry comprising:

• a first port;
• a second port;
• a first RF filter path connected between the first port and the second port, wherein the first RF filter path comprises at least one pair of weakly coupled resonators and a first capacitive element having a first capacitance, wherein the at least one pair of weakly coupled resonators are configured such that a first transfer response between the first port and the second port defines a first passband and wherein the first capacitive element is connected to the first port and is connected in series within the first RF filter path;
• and
• a second RF filter path connected in parallel with respect to the first RF filter path between the first port and the second port, wherein the second RF filter path is configured such that the first transfer response between the first port and the second port defines a stopband adjacent to the first passband and wherein the second RF filter path comprises a parallel resonator connected in shunt with respect to the second RF filter path and a second capacitive element that is connected to the first port and is connected in series within the second RF filter path, the second capacitive element having a second capacitance that is smaller than the first capacitance of the first capacitive element.

Radio frequency (RF) filtering circuitry comprising:

• a first port;
• a second port;
• a third port;
• a first RF filter path connected between the first port and the second port, wherein the first RF filter path comprises at least one pair of weakly coupled resonators that are configured such that a first transfer response between the first port and the second port defines a first passband;
• and
• a second RF filter path connected between the first RF filter path and the third port, the second RF filter path comprising a first series resonator connected in shunt with respect to the first RF filter path and a first parallel resonator connected in shunt with respect to the second RF filter path, the first series resonator being weakly coupled to the first parallel resonator such that the first transfer response defines a stopband adjacent to the first passband of the first transfer response.