High frequency filter and high frequency module equipped with same
To provide a smaller-sized high frequency filter. In a high frequency filter according to an embodiment of the invention, two filter circuits each equipped with a first externally coupling capacitor having one end coupled to an input-output terminal, a wavelength shortening capacitor having one end coupled to other end of the externally coupling capacitor and having other end coupled to the ground potential, and a resonator having one end coupled to the other end of the externally coupling capacitor and the one end of the wavelength shortening capacitor, having other end coupled to the ground potential, and being formed of a distributed constant line. The two filter circuits are broadside-coupled to each other.
1. A high frequency filter having a stack of a plurality of dielectric layers, comprising;
a first input-output terminal;
a second input-output terminal;
a first externally coupling capacitor having one end coupled to the first input-output terminal;
a first wavelength shortening capacitor having one end coupled to another end of the first externally coupling capacitor and having another end coupled to a ground potential;
a first resonator having one end coupled to the other end of the first externally coupling capacitor and the one end of the first wavelength shortening capacitor, and having another end coupled to the ground potential, the first resonator being formed of a distributed constant line;
a second externally coupling capacitor having one end coupled to the second input-output terminal;
a second wavelength shortening capacitor having one end coupled to another end of the second externally coupling capacitor and having another end coupled to the ground potential; and
a second resonator having one end coupled to the other end of the second externally coupling capacitor and the one end of the second wavelength shortening capacitor, and having another end coupled to the ground potential, the second resonator being formed of a distributed constant line and broadside-coupled to the first resonator.
2. The high frequency filter according to claim 1 , further comprising;
an internally coupling capacitor having one end coupled to the other end of the first externally coupling capacitor, the one end of the first wavelength shortening capacitor, and the one end of the first resonator, and having another end coupled to the other end of the second externally coupling capacitor, the one end of the second wavelength shortening capacitor, and the one end of the second resonator.
3. The high frequency filter according to claim 1 , wherein the first resonator and the second resonator are both coupled to the ground potential through a same via electrode.
4. The high frequency filter according to claim 1 , wherein the first resonator and/or the second resonator is formed of a bent distributed constant line.
5. The high frequency filter according to claim 1 , wherein ground planes are provided at the top and bottom dielectric layers.
6. The high frequency filter according to claim 5 , wherein a part of lateral side of the filter has a shielding via electrode coupled to the ground planes provided at the top and bottom dielectric layers.
7. The high frequency filter according to claim 1 , wherein the filter is formed of a low temperature co-fired ceramic (LTCC).
8. A high frequency module, comprising the high frequency filter according to claim 1 .