Phase shifter and antenna device

1 . A phase shifter comprising:

a 90-degree hybrid circuit; and

a variable-length stub group including two variable-length stubs connected to the 90-degree hybrid circuit, wherein

each variable-length stub includes

a first switch connected to the 90-degree hybrid circuit and including vanadium dioxide of a first composition that phase-transitions between an insulation phase and a metal phase in a first phase transition temperature range,

a first stub connected to the first switch,

a second switch connected to the first stub and including vanadium dioxide of a second composition that phase-transitions between an insulation phase and a metal phase in a second phase transition temperature range higher than the first phase transition temperature range, and

a second stub connected to the second switch and having an end grounded.

2 . The phase shifter according to claim 1 , wherein

the variable-length stub group includes

a first switch group including the two first switches,

a first stub group including the two first stubs,

a second switch group including the two second switches, and

a second stub group including the two second stubs.

3 . The phase shifter according to claim 2 , wherein the 90-degree hybrid circuit includes

four transmission lines having a same electrical length, and

electrical lengths of the first stubs and the second stubs are half an electrical length of the transmission line.

4 . The phase shifter according to claim 3 , further comprising

a control circuit that comprises

a memory storing instructions, and

a processor connected to the memory and configured to execute the instructions to

control temperatures of the two first switches included in the first switch group and the two second switches included in the second switch group.

5 . The phase shifter according to claim 4 , wherein

the processor of the control circuit is configured to execute the instructions to

individually control temperature of at least one of the two first switches included in the first switch group and the two second switches included in the second switch group.

6 . The phase shifter according to claim 4 , wherein

the processor of the control circuit is configured to execute the instructions to

collectively control temperature of at least two of the two first switches included in the first switch group and the two second switches included in the second switch group.

7 . The phase shifter according to claim 2 , wherein

the first stub group includes a plurality of the first stubs connected in series by at least one of the first switches, and

the second stub group includes a plurality of the second stubs connected in series by at least one of the second switches.

8 . The phase shifter according to claim 4 , comprising:

at least one dummy element including vanadium dioxide that phase-transitions in a known phase transition temperature range, wherein

the processor of the control circuit is configured to execute the instructions to

measure a temperature according to a change in an electric resistance value of the dummy element, and

control, in a case where an abnormality is detected in the measured temperature, the two first switches included in the first switch group and the two second switches included in the second switch group.

9 . An antenna device, comprising

an antenna unit including

a phase shifter according to claim 1 , and

a patch antenna disposed above the phase shifter.

10 . The antenna device according to claim 9 , further comprising

a patch antenna array in which a plurality of the antenna units are arranged in an array.