Impedance matching circuit and antenna apparatus using the same

An impedance matching circuit comprising:

• a hollow cylindrical dielectric;
• a ground conductor provided in a cylindrical inner surface of said cylindrical dielectric;
• a plurality of first matching circuits disposed in a cylindrical outer surface of said cylindrical dielectric to perform impedance matching at a frequency f2, each of said first matching circuits including a strip conductor constituting a micro strip line with said ground conductor via said cylindrical dielectric, a transmission line, and a capacitance device;
• and
• a plurality of second matching circuits disposed in the cylindrical outer surface of said cylindrical dielectric and respectively connected to said plurality of first matching circuits, each of said second matching circuits including the strip conductor, a transmission line, and a parallel-resonant circuit adapted to resonate at the frequency f2 and exhibit a predetermined susceptance value at a frequency f1.

An antenna apparatus comprising:

• a hollow cylindrical dielectric;
• helical radiation devices amounting to N in number, including a strip-like conductor and helically wound on a cylindrical outer surface of said cylindrical dielectric;
• a ground conductor provided in a region, the region being a part of a cylindrical inner surface of said cylindrical dielectric;
• a strip conductor provided in the cylindrical inner surface of said cylindrical dielectric, constituting a micro strip line with said ground conductor via said cylindrical dielectric, and constituting a power supply line to each of said helical radiation devices;
• impedance matching circuits amounting to N in number, respectively connected to said helical radiation devices, each of said impedance matching circuits including a first matching circuit having the strip conductor, a transmission line and a capacitance device, and adapted to perform impedance matching at a frequency f2, and a second matching circuit connected to the first matching circuit, the second matching circuit having the strip conductor, a transmission line, and a parallel-resonant circuit adapted to resonate at the frequency f2 and exhibit a predetermined susceptance value at a frequency f1;
• and
• an N-distribution circuit including the strip conductor, wherein said N-distribution circuit comprises distributing terminals amounting to N in number exhibiting required distribution amplitude and phase characteristics, said distributing terminals being respectively connected to input terminals of said impedance matching circuits amounting to N in number.