High-frequency filter

A high-frequency filter, comprising, on a surface of a dielectric substrate,

• transmission lines connected to a first terminal and a second terminal, respectively, and
• 2n−1 (n is an integer of 2 or more) lumped constant elements connected in series between the transmission lines,
• one end of a first lumped constant element being connected to the first terminal,
• one end of a 2n−1-th lumped constant element being connected to the second terminal, and
• a second to a 2n−2-th lumped constant elements being connected between the first lumped constant element and the 2n−1-th lumped constant element,
• wherein all of the 2n−1 lumped constant elements are composed of capacitors, the capacitors being connected to each other by a transmission line having a line length of λ/4 (λ is a wavelength within a transmission line corresponding to a frequency f0 at which a reflection loss of a passband frequency is minimized) and a characteristic impedance of Z0, and
• wherein
• (i) when n is 2, a capacitance C(H1) of the capacitors is given by:
• C(H1)=1/(2π·f0·Z0), and
• (ii) when n is 3 or more, a capacitance C(H2) of a 2x−1-th (x is an integer from 2 to (n−1)) one of the capacitors from the first terminal is given by:
• C(H2)=½(2π·f0·Z0), and
• a capacitance C(H3) of the capacitors other than the 2x−1-th one from the first terminal is given by:
• C
• ⁡
• (
• H
• ⁢
• 3
• )
• =
• 1
• /
• (
• 2
• ⁢
• π
• ·
• f
• 0
• ·
• Z
• 0
• )
• .