Switchable high pass filter/low pass filter phase shifter having a switch circuit with FETs connected in parallel
View Patent ↗A switch circuit in which the cut-off characteristic is improved over a wide range of frequencies in the microwave band includes a first field-effect transistor functioning as a switch element, a second field-effect transistor and an inductor. A serially connected circuit composed of the inductor and second field-effect transistor is connected in parallel with the first field-effect transistor across the source and drain thereof. The second field-effect transistor is turned on when the first field-effect transistor operates normally and is turned off when the first field-effect transistor is inspected.
1. A switch circuit, comprising:
a first field-effect transistor that functions as a switch element;
a second field-effect transistor; and
an inductor,
wherein a serially connected circuit including said inductor and said second field-effect transistor is connected in parallel with said first field-effect transistor across a source and drain thereof.
2. The switch circuit according to claim 1 , wherein said second field-effect transistor is turned on at a time of normal operation of said first field-effect transistor and is turned off when said first field-effect transistor is inspected.
3. A phase shifter, comprising:
first and second single-pole, double-throw switches;
a high-pass filter; and
a low-pass filter,
wherein each of said first and second single-pole, double-throw switches having first and second switch circuits,
wherein a contact on the single-pole side of one of the first and second switch circuit is connected to said high-pass filter and a contact on the single-pole side of the other of the first and second switch circuit is connected to said low-pass filter, and
wherein said first and second switch circuits are adapted so as to turn on exclusively, wherein each of said switch circuits comprises:
a first field-effect transistor that functions as a switch element;
a second field-effect transistor; and
an inductor,
wherein a serially connected circuit composed of said inductor and said second field-effect transistor is connected in parallel with said first field-effect transistor across a source and drain thereof.
4. The phase shifter according to claim 3 , further comprising first and second inspection pads connected to first and second ends, respectively, of said high-pass filter, a voltage vs. current characteristic being measurable between said first and second inspection pads.
5. The phase shifter according to claim 4 , further comprising:
a third inspection pad connected to gates of said first field-effect transistors in the first and second switch circuits associated with said high-pass filter;
a fourth inspection pad connected to gates of said second field-effect transistors in the first and second switch circuits associated with said high-pass filter;
a fifth inspection pad connected to gates of said first field-effect transistors in the first and second switch circuits associated with said low-pass filter; and
a sixth inspection pad connected to gates of said second field-effect transistors in the first and second switch circuits associated with said low-pass filter.