# US 11,451,208 B2 · Switching circuit and variable attenuator

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- Number: US 11,451,208 B2
- Document ID: US11451208B2
- Status: Granted
- Kind: B2
- Application number: 17/015,978
- Filed: 2020-09-09
- Published: 2020-12-31
- Granted: 2022-09-20
- Earliest claimed: 2018-03-29
- Assignees: Mitsubishi Electric Corporation
- Applicants: Mitsubishi Electric Corporation
- Inventors: Kengo Kawasaki; Masaomi Tsuru; Mitsuhiro Shimozawa
- Web page: https://patentgrep.com/patent/US11451208B2

## CPC

- H03H 7/25: comprising an element controlled by an electric or magnetic variable (H03H7/27 takes precedence)
- H03K 17/693: Switching arrangements with several input- or output-terminals, e.g. multiplexers, distributors (logic circuits H03K19/00; code converters H03M5/00, H03M7/00)
- H01P 1/22: Attenuating devices (dissipative terminating devices H01P1/26)
- H03H 11/16: Networks for phase shifting
- H03H 11/245: {using field-effect transistor}
- H03K 17/04: Modifications for accelerating switching
- H03K 17/687: the devices being field-effect transistors
- H03K 2217/0054: Gating switches, e.g. pass gates
- H04B 1/44: Transmit/receive switching
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)
- H01P: WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE (operating at optical frequencies G02B)
- H04B: TRANSMISSION

## Abstract

A first switch is connected in parallel with a circuit element. A second switch is connected in series with a parallel circuit constituted by the circuit element and the first switch. The first switch and the second switch alternately perform on-off operation.

## Claims

### Claim 1

A variable attenuator comprising:
a switching circuit configured as a shunt circuit of the variable attenuator, the switching circuit including,
a first switch connected in parallel with a first circuit element; and
a second switch connected in series with a parallel circuit constituted by the first circuit element and the first switch; and
a second circuit element connected in series with the first circuit element and the second switch,
wherein the first switch and the second switch alternately perform on-off operation,
the second switch has a parasitic reactance set in such a way that a parasitic reactance occurring at the parallel circuit in a first state in which the first switch is controlled to be off and the second switch is controlled to be on and a parasitic reactance occurring at the second switch in a second state in which the first switch is controlled to be on and the second switch is controlled to be off are equal to each other,
the first switch is controlled to be off in the first state and to be on in the second state, and
the second switch is controlled to be on in the first state and to be off in the second state.

### Claim 2 (depends on 1)

The variable attenuator according to claim 1, wherein
the variable attenuator is a π-attenuator having a third switch connected in parallel with the second circuit element, and first and second shunt circuits connected to respective ends of the second circuit element,
wherein the switching circuit is configured as the first shunt circuit,
a second switching circuit is configured as the second shunt circuit, the second switching circuit including
a fourth switch connected in parallel with a third circuit element; and
a fifth switch connected in series with a second parallel circuit constituted by the third circuit element and the fourth switch, and in series with the second circuit element,
a resistor is used for each of the first, second, and third circuit elements of the switching circuit.

### Claim 3 (depends on 1)

The variable attenuator according to claim 1, wherein
the variable attenuator is a π-attenuator having first and second shunt circuits connected to respective ends of the second circuit element,
wherein the switching circuit is configured as the first shunt circuit,
a second switching circuit is configured as the second shunt circuit, the second switching circuit including
a third switch connected in parallel with a third circuit element; and
a fourth switch connected in series with a parallel circuit constituted by the third circuit element and the third switch,
a resistor is used for each of the first and third circuit elements,
the first switch and the third switch are controlled to be off in the first state and to be on in the second state, and
the second switch and the fourth switch are controlled to be on in the first state and to be off in the second state.

### Claim 4 (depends on 1)

The variable attenuator according to claim 1, wherein
the variable attenuator is a T type attenuator with a third circuit element being connected in series with each of the second circuit element and the shunt circuit,
a resistor is used for each of the first, second, and third circuit elements,
a third switch connected in parallel with the second circuit element, and a fourth switch connected in parallel with the third circuit element,
the third switch and the fourth switch are controlled to be off in the first state and to be on in the second state,
the first switch is controlled to be off in the first state and to be on in the second state, and
the second switch is controlled to be on in the first state and to be off in the second state.

### Claim 5 (depends on 1)

The variable attenuator according to claim 1, wherein
the variable attenuator is a T type attenuator,
a resistor is used for the first circuit element of the switching circuit,
the first switch is controlled to be off in the first state and to be on in the second state, and
the second switch is controlled to be on in the first state and to be off in the second state.

### Claim 6 (depends on 1)

The switching circuit according to claim 1, wherein the first switch and the second switch each operate as a short circuit while being on and as capacitance while being off.

### Claim 7 (depends on 6)

The variable attenuator according to claim 6, wherein
the variable attenuator is a π-attenuator having a third switch connected in parallel with the second circuit element, and first and second shunt circuits connected to respective ends of the second circuit element,
wherein the switching circuit is configured as the first shunt circuit,
a second switching circuit is configured as the second shunt circuit, the second switching circuit including
a fourth switch connected in parallel with a third circuit element; and
a fifth switch connected in series with a second parallel circuit constituted by the third circuit element and the fourth switch, and in series with the second circuit element,
a resistor is used for each of the first, second, and third circuit elements of the switching circuit.

### Claim 8 (depends on 6)

The variable attenuator according to claim 6, wherein
the variable attenuator is a π-attenuator having first and second shunt circuits connected to respective ends of the second circuit element,
wherein the switching circuit is configured as the first shunt circuit,
a second switching circuit is configured as the second shunt circuit, the second switching circuit including
a third switch connected in parallel with a third circuit element; and
a fourth switch connected in series with a parallel circuit constituted by the third circuit element and the third switch,
a resistor is used for each of the first and third circuit elements,
the first switch and the third switch are controlled to be off in the first state and to be on in the second state, and
the second switch and the fourth switch are controlled to be on in the first state and to be off in the second state.

### Claim 9 (depends on 6)

The variable attenuator according to claim 6, wherein
the variable attenuator is a T type attenuator with a third circuit element being connected in series with each of the second circuit element and the shunt circuit,
a resistor is used for each of the first, second, and third circuit elements,
a third switch connected in parallel with the second circuit element, and a fourth switch connected in parallel with the third circuit element,
the third switch and the fourth switch are controlled to be off in the first state and to be on in the second state,
the first switch is controlled to be off in the first state and to be on in the second state, and
the second switch is controlled to be on in the first state and to be off in the second state.

### Claim 10 (depends on 6)

The variable attenuator according to claim 6, wherein
the variable attenuator is a T type attenuator,
a resistor is used for the first circuit element of the switching circuit,
the first switch is controlled to be off in the first state and to be on in the second state, and
the second switch is controlled to be on in the first state and to be off in the second state.

### Claim 11 (depends on 1)

The switching circuit according to claim 1, wherein the first switch and the second switch each operate as a short circuit while being on and as an inductor while being off.

### Claim 12 (depends on 11)

The variable attenuator according to claim 11, wherein
the variable attenuator is a π-attenuator having a third switch connected in parallel with the second circuit element, and first and second shunt circuits connected to respective ends of the second circuit element,
wherein the switching circuit is configured as the first shunt circuit,
a second switching circuit is configured as the second shunt circuit, the second switching circuit including
a fourth switch connected in parallel with a third circuit element; and
a fifth switch connected in series with a second parallel circuit constituted by the third circuit element and the fourth switch, and in series with the second circuit element,
a resistor is used for each of the first, second, and third circuit elements of the switching circuit.

### Claim 13 (depends on 11)

The variable attenuator according to claim 11, wherein
the variable attenuator is a π-attenuator having first and second shunt circuits connected to respective ends of the second circuit element,
wherein the switching circuit is configured as the first shunt circuit,
a second switching circuit is configured as the second shunt circuit, the second switching circuit including
a third switch connected in parallel with a third circuit element; and
a fourth switch connected in series with a parallel circuit constituted by the third circuit element and the third switch,
a resistor is used for each of the first and third circuit elements,
the first switch and the third switch are controlled to be off in the first state and to be on in the second state, and
the second switch and the fourth switch are controlled to be on in the first state and to be off in the second state.

### Claim 14 (depends on 3)

The variable attenuator according to claim 3, wherein
the variable attenuator is a T type attenuator with a third circuit element being connected in series with each of the second circuit element and the shunt circuit,
a resistor is used for each of the first, second, and third circuit elements,
a third switch connected in parallel with the second circuit element, and a fourth switch connected in parallel with the third circuit element,
the third switch and the fourth switch are controlled to be off in the first state and to be on in the second state,
the first switch is controlled to be off in the first state and to be on in the second state, and
the second switch is controlled to be on in the first state and to be off in the second state.

### Claim 15 (depends on 11)

The variable attenuator according to claim 11, wherein
the variable attenuator is a T type attenuator,
a resistor is used for the first circuit element of the switching circuit,
the first switch is controlled to be off in the first state and to be on in the second state, and
the second switch is controlled to be on in the first state and to be off in the second state.