Tunable microwave devices with auto-adjusting matching circuit
View Patent ↗An impedance matching circuit includes a conductor line having an input port and an output port, a ground conductor, a tunable dielectric material positioned between a first section of the conductor line and the ground conductor, a non-tunable dielectric material positioned between a second section of the conductor line and the ground conductor, and means for applying a DC voltage between the conductor line and the ground conductor. The impedance matching circuit may alternatively include a first planar ground conductor, a second planar ground conductor, a strip conductor having an input port and an output port, and positioned between the first and second planar ground conductors to define first and second gaps, the first gap being positioned between the strip conductor and the first planar ground conductor and the second gap being positioned between the strip conductor and the second planar ground conductor. A non-tunable dielectric material supports the first and second planar ground conductors and the strip conductor in the same plane. A connection is provided for applying a DC voltage between the strip conductor and the first and second planar ground conductors. A plurality of tunable dielectric layer sections are positioned between the strip conductor and the first and second planar ground conductors so as to bridge the gaps between the said first and second planar ground conductors and the strip conductor at a plurality of locations, leaving non-bridged sections in between, defining a plurality of alternating bridged and non-bridged co-planar waveguide sections.
1. An impedance matching circuit comprising:
a conductor line having an input port and an output port;
a ground conductor;
a first microstrip stage comprising a tunable dielectric material positioned between a first section of said conductor line and said ground conductor;
a second microstrip stage comprising a non-tunable dielectric material positioned between a second section of said conductor line and said ground conductor;
a third microstrip stage comprising a tunable dielectric material positioned between a first section of said conductor line and said ground conductor, wherein said second microstrip stage is positioned between said first microstrip stage and said third microstrip stage; and
an adjustable DC voltage source for applying a DC voltage between said conductor line and said ground conductor.
2. The impedance matching circuit of claim 1 , wherein:
the conductor line is a multi-step microstrip line; and
the ground conductor comprises a ground plane.
3. The impedance matching circuit of claim 2 , wherein:
the first section of the multi-step microstrip line is deposited on said first microstrip stage;
the second section of the multi-step microstrip line is deposited on said second microstrip stage; and
the first and second sections of the multi-step microstrip line are connected in series to form a tunable microstrip impedance transformer.
4. The impedance matching circuit of claim 3 , further comprising:
multiple pairs of microstrip sections functionally interposed between said first section and said second section of said multi-step microstrip line;
each pair of microstrip sections include a microstrip section on a tunable dielectric material which is connected in series with a microstrip section on a non-tunable dielectric material; and
the pairs of microstrip sections together with said first and said second sections of the multi-step microstrip line are connected in series to form a cascaded network.
5. The impedance matching circuit of claim 1 , wherein:
the conductor line is a multi-step stripline; and
the ground conductor is a first ground plane and a second ground plane.
6. The impedance matching circuit of claim 5 , wherein:
the first section of the multi-step stripline is deposited within said tunable dielectric material located between said first ground plane and said second ground plane;
the second section of the multi-step stripline is deposited within said non-tunable dielectric material located between said first ground plane and said second ground plane; and
the first and second sections of the multi-step stripline are connected in series to form a tunable stripline impedance transformer.
7. The impedance matching circuit of claim 6 , further comprising:
multiple pairs of stripline functionally interposed between said first section and said second section of said multi-step stripline;
each pair of stripline sections include a microstrip section deposited within a tunable dielectric material which is connected in series with a microstrip section deposited within a non-tunable dielectric material; and
the pairs of stripline sections together with the said first and said second sections of the multi-step stripline are connected in series to form a cascaded network.
8. The impedance matching circuit of claim 1 , wherein:
the conductor line is a center conductor;
the ground conductor is a cylindrical outer ground conductor; and
the center conductor is coaxially aligned with said cylindrical outer ground conductor.
9. The impedance matching circuit of claim 8 , wherein:
the first section of the center conductor is imbedded in the tunable dielectric material;
the second section of the center conductor is imbedded in the non-tunable dielectric material;
the first and second sections of the center conductor are connected in series to form a tunable co-axial transmission line impedance transformer.
10. The impedance matching circuit of claim 9 , further comprising:
multiple pairs of center conductor sections functionally interposed between said first section and said second section of said center conductor;
each pair of center conductor sections includes a conductor section in a tunable dielectric material which is connected in series with a conductor section in a non-tunable dielectric material;
the pairs of center conductor sections together with the said first and said second sections of the center conductor are connected in series to form a cascaded network.
11. The impedance matching circuit of claim 1 , wherein:
the tunable dielectric material is a barium strontium titanate composite.
12. The impedance matching circuit of claim 1 , wherein the tunable dielectric material includes a material selected from the group of:
Ba x Sr 1-x TiO 3 , Ba x Ca 1-x TiO 3 , Pb x Zr 1-x TiO 3 , lead lanthanum zirconium titanate, PbTiO 3 , BaCaZrTiO 3 , NaNO 3 , KNbO 3 , LiNbO 3 , LiTaO 3 , PbNb 2 O 6 , PbTa 2 O 6 , KSr(NbO 3 ) and NaBa 2 (NbO 3 )5KH 2 PO 4 .
13. The impedance matching circuit of claim 12 , wherein the tunable dielectric material further includes a material selected from the following:
MgO, MgAl 2 O 4 , MgTiO 3 , Mg 2 SiO 4 , MgZrO 3 , CaSiO 3 , MgSrZrTiO 6 , CaTiO 3 , Al 2 O 3 , SiO 2 , BaSiO 3 , and SrSiO 3 , and combinations thereof.
14. The impedance matching circuit of claim 12 , wherein the tunable dielectric material further includes a material selected from the group of:
zirconnates, tannates, rare earths, niobates, tantalates, CaZrO 3 , BaZrO 3 , SrZrO 3 , BaSnO 3 , CaSnO 3 , MgSnO 3 , Bi 2 O 3 /2SnO 2 , Nd 2 O 3 , Pr 7 O 11 , Yb 2 O 3 , Ho 2 O 3 , La 2 O 3 , MgNb 2 O 6 , SrNb 2 O 6 , BaNb 2 O 6 , MgTa 2 O 6 , BaTa 2 O 6 and Ta 2 O 3 .
15. The impedance matching circuit of claim 1 , wherein said impedance matching circuit can maximize the power transfer from a microwave source to a tunable microwave device.
16. The impedance matching circuit of claim 15 , wherein said tunable microwave device includes a tunable phase shifter, a tunable delay line or a tunable filter.
17. The impedance matching circuit of claim 15 , wherein said tunable microwave device operates in a range from 500 MHz to 40 GHz.
18. The impedance matching circuit to claim 1 , wherein said impedance matching circuit can maximize the power transfer to a microwave load from a tunable microwave device.
19. The impedance matching circuit of claim 18 , wherein said tunable microwave device includes a tunable phase shifter, a tunable delay line or a tunable filter.
20. The impedance matching circuit of claim 18 , wherein said tunable microwave device operates in a range from 500 MHz to 400 Hz.
21. The impedance matching circuit of claim 1 , wherein said first microstrip stage is substantially longer than a quarter wavelength.
22. The impedance matching circuit of claim 1 , wherein said first microstrip stage is substantially shorter than a quarter wavelength.
23. The impedance matching circuit of claim 1 , wherein the tunable dielectric material comprises Ba x Ca 1-x TiO 3 .
24. The impedance matching circuit of claim 1 , wherein the tunable dielectric material comprises lead.
25. The impedance matching circuit of claim 1 , wherein the tunable dielectric material comprises lanthanum.
26. The impedance matching circuit of claim 1 , wherein the tunable dielectric material comprises niobium.