Electrically tunable notch filters
An embodiment of the present invention provides n apparatus, comprising a wireless telephone handset comprising an antenna connection; a diplexer coupled to the antenna connection; a transmit section connected to a first port of the diplexer; a receive section connected to a second port of the diplexer; and wherein the diplexer includes first and second notch filters, each of the notch filters comprising a main transmission line, a first coupling mechanism, and a first electrically tunable resonator coupled to the main transmission line through the first coupling mechanism, wherein the first electrically tunable resonator includes a voltage tunable dielectric varactor and wherein a control unit provides control signals for controlling the voltage tunable dielectric varactor, thereby tuning the first and second notch filters to provide isolation between the transmit and receive frequencies.
1 . An apparatus, comprising:
a wireless telephone handset comprising:
an antenna connection;
a diplexer coupled to the antenna connection;
a transmit section connected to a first port of the diplexer;
a receive section connected to a second port of the diplexer; and
wherein the diplexer includes first and second notch filters, each of the notch filters comprising a main transmission line, a first coupling mechanism, and a first electrically tunable resonator coupled to the main transmission line through the first coupling mechanism, wherein the first electrically tunable resonator includes a voltage tunable dielectric varactor and wherein a control unit provides control signals for controlling said voltage tunable dielectric varactor, thereby tuning said first and second notch filters to provide isolation between the transmit and receive frequencies.
2 . The apparatus of claim 9 , wherein said composite or doped voltage tunable dielectric material are selected from the group consisting of: BSTO-MgO, BSTO-MgAl2O4, BSTO-CaTiO3, BSTO-MgTiO3, BSTO-MgSrZrTiO6, and combinations thereof.
3 . The apparatus of claim 10 , wherein said composite or doped voltage tunable dielectric material is a BSTO-composite ceramic material.
4 . The apparatus of claim 9 , wherein the first coupling mechanism comprises one of:
a first capacitive probe, a first inductive loop, a first iris window, a first evanescent waveguide piece, a first slot, and a first hole.
5 . The apparatus of claim 9 , wherein the main transmission line comprises one of:
a coaxial transmission line, a microstrip line, a stripline line, a rectangular waveguide, a coplanar waveguide, and a ridged waveguide.
6 . The apparatus of claim 9 , wherein each of the first and second notch filters further includes:
a second coupling mechanism; and
a second electrically tunable resonator coupled to the main transmission line through the second coupling mechanism, wherein the first and second coupling mechanisms are spaced ¼ wavelength apart at an operating frequency of the filter.
7 . An apparatus, comprising:
a wireless telephone handset comprising:
an antenna connection;
a diplexer coupled to the antenna connection;
a transmit section connected to a first port of the diplexer;
a receive section connected to a second port of the diplexer; and
wherein the diplexer includes first and second notch filters, each of the notch filters comprise a bandpass filter connected between a termination and one of a circulator or a 3 dB hybrid, wherein the bandpass filter includes a voltage tunable dielectric varactor.