Analog bandpass filters

An analog bandpass filter (BPF) comprising:

• a first low pass filter (LPF) coupled to a first radio-frequency (RF) port;
• a second LPF coupled to a second RF port;
• and
• a high-pass module coupled in series between the first LPF and the second LPF;
• wherein a main series path is defined between the first RF port and the second RF port, the main series path part comprises at least part of the first LPF, part of the second LPF, and part of the high-pass module;
• wherein one or more resonant circuits are established for adjusting a center frequency of the analog BPF, the one or more resonant circuits at least partially overlap with the main series path, the one or more resonant circuits involve the high-pass module and at least one of the first and second LPFs;
• wherein the high-pass module comprises one or more tuning stages, each tuning stage comprises at least one shunt inductor and at least one series capacitor, the at least one series capacitor of each stage is on the main series path;
• and
• wherein each of the first LPF and second LPF comprises a shunt capacitor, the at least one series capacitor of each tuning stage has a larger capacitance value than a capacitance value of the shunt capacitor of the first LPF and a capacitance value of the shunt capacitor of the second LPF.

An analog bandpass filter (BPF) comprising:

• a first low pass filter (LPF) coupled to a first radio-frequency (RF) port, the first LPF comprising a series inductor and a shunt capacitor;
• and
• a first high-pass module coupled to the first LPF, the high-pass module comprising at least one shunt inductor and at least one series capacitor, the at least one series capacitor, the series inductor and the first RF port are coupled in series to form a main path for RF signal transmission;
• wherein a resonant circuit is established from the at least one shunt inductor from the high-pass module and the shunt capacitor from the first LPF, the resonant circuit further comprises the series inductor from the first LPF, the series inductor coupled between the at least one shunt inductor and the shunt capacitor;
• wherein the shunt capacitor and the at least one series capacitor are varactors with adjustable capacitance values, the varactors are coupled to a common biasing voltage source, via a biasing resistor and a choke inductor coupled in series with the biasing resistor for DC-RF isolation between the common biasing voltage source and each varactor, for adjusting a capacitance value thereof.