US-12620976-B2 - Variable attenuator

US12620976B2US 12620976 B2US12620976 B2US 12620976B2US-12620976-B2

Abstract

A variable attenuator includes n attenuation resistor circuits and m adjustment resistor circuits connected in parallel to a signal line, the n attenuation resistor circuits are on-off controlled by corresponding attenuation amount control signals, each of the n attenuation resistor circuits being with a different attenuation amount, the adjustment resistor circuits correspond to k attenuation resistor circuits, and are on-off controlled by a signal of a logical product of k attenuation amount control signals for performing on-off control corresponding to each of the selected k attenuation resistor circuits, and when being on-controlled by a signal of a logical product of the k attenuation amount control signals, attenuation amount of the adjustment resistor circuits are made equal to a sum of attenuation amounts when the k attenuation resistor circuits controlled by the corresponding k attenuation amount control signals are independently on-controlled.

Inventors

Shinji Takezoe
Koji Tsutsumi

Assignees

MITSUBISHI ELECTRIC CORPORATION

Dates

Publication Date: 20260505
Application Date: 20241003

Claims (11)

1 . A variable attenuator comprising n attenuation resistor circuits and m adjustment resistor circuits connected in parallel to a signal line, wherein the n attenuation resistor circuits are on-off controlled by corresponding attenuation amount control signals, each of the n attenuation resistor circuits exhibits a different attenuation amount when being independently on-controlled, the adjustment resistor circuits correspond to k attenuation resistor circuits selected from the n attenuation resistor circuits, and are on-off controlled by a signal of a logical product of k attenuation amount control signals for performing on-off control corresponding to each of the selected k attenuation resistor circuits, and when being on-controlled by a signal of a logical product of the k attenuation amount control signals, attenuation amount of the adjustment resistor circuits are made equal to a sum of attenuation amounts when the k attenuation resistor circuits controlled by the corresponding k attenuation amount control signals are independently on-controlled together with a sum of attenuation amounts by the selected k attenuation resistor circuits simultaneously on-controlled by the corresponding k attenuation amount control signals.
2 . The variable attenuator according to claim 1 , wherein the n is 2, the m is 1, and the k is 2, an attenuation amount by a second attenuation resistor circuit of two of the attenuation resistor circuits when being independently on-controlled by a second attenuation amount control signal of two of the attenuation amount control signals is twice as large as an attenuation amount in decibel notation by a first attenuation resistor circuit of two of the attenuation resistor circuits when being independently on-controlled by a first attenuation amount control signal of the two of the attenuation amount control signals, and when the first attenuation amount control signal and the second attenuation amount control signal cause the first attenuation resistor circuit and the second attenuation resistor circuit to be simultaneously on-controlled, the adjustment resistor circuit is on-controlled by a signal of a logical product of the first attenuation amount control signal and the second attenuation amount control signal, and adjusts an attenuation amount for the signal line to a step width that is same as a step width of an attenuation amount by the first attenuation resistor circuit and an attenuation amount by the second attenuation resistor circuit with respect to an attenuation amount by the second attenuation resistor circuit.
3 . The variable attenuator according to claim 1 , wherein the n is a natural number equal to or more than 2, the m is 2 n −1−n, and the k is n of 2 or more, an attenuation amount when being independently on-controlled by a corresponding attenuation amount control signal in each of the n attenuation resistor circuits is 2 N-1 (N is 1 to n) dB, the m adjustment resistor circuits include (2 N-2 −1) adjustment resistor circuits to adjust an attenuation amount from an attenuation amount of 2 N-2 dB by the (N−1)-th attenuation resistor circuit to an attenuation amount of 2 N-1 dB by the N-th attenuation resistor circuit by a same step width, and each of the (2 N-2 −1) adjustment resistor circuits corresponds to one combination of two or more combinations of two or more attenuation resistor circuits up to an (N−1)-th attenuation resistor circuit.
4 . The variable attenuator according to claim 1 , wherein each of the n attenuation resistor circuits includes a switcher and an attenuation resistor that are on-off controlled by a corresponding attenuation amount control signal among the n attenuation amount control signals, and each of the m adjustment resistor circuits includes a switcher and an adjustment resistor that are on-off controlled by a signal of a logical product of the selected k attenuation amount control signals.
5 . The variable attenuator according to claim 4 , wherein in each of the attenuation resistor circuits, the switcher is a MOS transistor having a first main electrode connected to the signal line, a corresponding attenuation amount control signal among the n attenuation amount control signals is input to a gate electrode of the MOS transistor, and the attenuation resistor is connected between a second main electrode of the MOS transistor and a ground node, and in each of the adjustment resistor circuits, the switcher is a series body including k MOS transistors having a first end connected to the signal line, a corresponding attenuation amount control signal among the selected k attenuation amount control signals is input to a gate electrode of each of MOS transistors, and the adjustment resistor is connected between a second end of the series body and the ground node.
6 . The variable attenuator according to claim 1 , wherein the signal line is a pair of signal lines, each of the attenuation resistor circuits includes a switcher and an attenuation resistor connected in series between the pair of signal lines, and the switcher includes a one-side switcher and an other-side switcher with the attenuation resistor interposed therebetween, the switcher being on-off controlled by a corresponding attenuation amount control signal, and each of the adjustment resistor circuits includes a switcher and an adjustment resistor connected in series between the pair of signal lines, and the switcher includes a one-side switcher and an other-side switcher with the adjustment resistor interposed therebetween, the one-side switcher and the other-side switcher being on-off controlled by a signal of a logical product of corresponding selected k attenuation amount control signals.
7 . The variable attenuator according to claim 6 , wherein the n is 2, the m is 1, and the k is 2, an attenuation amount for a first signal line in the pair of signal lines by a second attenuation resistor circuit of two of the attenuation resistor circuits when being independently on-controlled by a second attenuation amount control signal of two of the attenuation amount control signals is twice as large as an attenuation amount in decibel notation for the first signal line in the pair of signal lines by a first attenuation resistor circuit of two of the attenuation resistor circuits when being independently on-controlled by a first attenuation amount control signal of the two of the attenuation amount control signals, and when the one-side switcher in the adjustment resistor circuit is on-off controlled by the second attenuation amount control signal, the other-side switcher is on-off controlled by the first attenuation amount control signal, and the first attenuation resistor circuit and the second attenuation resistor circuit are simultaneously on-controlled by the first attenuation amount control signal and the second attenuation amount control signal, and the attenuation amount for the first signal line in the pair of signal lines is adjusted to a same step width as a step width of the attenuation amount by the first attenuation resistor circuit and the attenuation amount by the second attenuation resistor circuit with respect to the attenuation amount by the second attenuation resistor circuit.
8 . The variable attenuator according to claim 7 , wherein in each of the first attenuation resistor circuit and the second attenuation resistor circuit, the one-side switcher is a MOS transistor connected between the first signal line in the pair of signal lines and a first end of the attenuation resistor and to which the first attenuation amount control signal or the second attenuation amount control signal corresponding to each of gate electrodes is input, and the other-side switcher is a MOS transistor that is connected between the second signal line in the pair of signal lines and a second end of the attenuation resistor, and to which the first attenuation amount control signal or the second attenuation amount control signal corresponding to each of gate electrodes is input, and in the adjustment resistor circuit, the one-side switcher is a MOS transistor connected between the first signal line in the pair of signal lines and a first end of the adjustment resistor, and in which the second attenuation amount control signal is input to a gate electrode, and the other-side switcher is a MOS transistor that is connected between the second signal line in the pair of signal lines and a second end of the adjustment resistor, and in which the first attenuation amount control signal is input to a gate electrode.
9 . The variable attenuator according to claim 6 , wherein the n is a natural number equal to or more than 2, the m is 2 n −1−n, and the k is n of 2 or more, and an attenuation amount for the first signal line in the pair of signal lines when being independently on-controlled by a corresponding attenuation amount control signal in each of the n attenuation resistor circuits is 2 N-1 (N is 1 to n) dB, the m adjustment resistor circuits include (2 N-2 −1) adjustment resistor circuits to adjust an attenuation amount from an attenuation amount of 2 N-2 dB for the first signal line in the pair of signal lines by the (N−1)-th attenuation resistor circuit to an attenuation amount of 2 N-1 dB for the first signal line in the pair of signal lines by the N-th attenuation resistor circuit by a same step width, each of the (2 N-2 −1) adjustment resistor circuits corresponds to one combination of two or more combinations of two or more attenuation resistor circuits up to an (N−1)-th attenuation resistor circuit, the one-side switcher in each of the adjustment resistor circuits is on-off controlled by a signal of a logical product of attenuation amount control signals for a half of a plurality of attenuation resistor circuits corresponding to the combination, and the other-side switcher in each of the adjustment resistor circuits is on-off controlled by a signal of a logical product of attenuation amount control signals for a remaining half of the plurality of attenuation resistor circuits corresponding to the combination.
10 . The variable attenuator according to claim 9 , wherein in each of the attenuation resistor circuits, the one-side switcher in the switcher is a MOS transistor in which a first main electrode is connected to the first signal line in the pair of signal lines, a corresponding attenuation amount control signal among the n attenuation amount control signals is input to a gate electrode of the MOS transistor, a second main electrode of the MOS transistor is connected to a first end of the corresponding attenuation resistor, the other-side switcher in the switcher is a MOS transistor in which a first main electrode is connected to a second signal line in the pair of signal lines, a corresponding attenuation amount control signal among the n attenuation amount control signals is input to a gate electrode of the MOS transistor, and the second main electrode of the MOS transistor is connected to a second end of the corresponding attenuation resistor, and in each of the adjustment resistor circuits, the one-side switcher of the switcher is a series body including a half of the k MOS transistors that each have a first end connected to the first signal line in the pair of signal lines and a second end connected to a first end of the adjustment resistor, and in which a corresponding attenuation amount control signal in a corresponding half of k attenuation amount control signals among the selected k attenuation amount control signals is input to a gate electrode, and the other-side switcher of the switcher is a series body including a remaining half of the k MOS transistors that each have a first end connected to the second signal line in the pair of signal lines and a second end connected to a second end of the adjustment resistor, and in which a corresponding attenuation amount control signal in a corresponding remaining half of the k attenuation amount control signals among the selected k attenuation amount control signals is input to a gate electrode.
11 . The variable attenuator according to claim 9 , wherein when the k is an odd number, the half and the remaining half mean (k+1)/2, and one of the half and the remaining half overlaps.

Description

CROSS REFERENCE TO RELATED APPLICATION This application is a Continuation of PCT International Application No. PCT/JP2022/021037, filed on May 23, 2022, which is hereby expressly incorporated by reference into the present application. TECHNICAL FIELD The present disclosure relates to a variable attenuator. BACKGROUND ART In order to obtain a simple layout, a simplified switched T-type attenuator is proposed as an attenuator in Non Patent Literature 1. The T-type attenuator disclosed in Non-Patent Literature 1 includes a shunt transistor and a shunt resistor connected in series between a signal line and a ground node. CITATION LIST Non Patent Literature Non Patent Literature 1: MK Cho et al. “A SiGe-BiCMOS Wideband Active Bidirectional Digital Step Attenuator With Bandwidth Tuning and Equalization” IEEE Transactions on Microwave Theory and Techniques, Volume. 66, No 8, AUGUST. 2018 SUMMARY OF INVENTION Technical Problem In order to vary the attenuation amount using a plurality of T-type attenuators disclosed in Non-Patent Literature 1, it is necessary to perform on-off control of the shunt transistor of each T-type attenuator. It is conceivable to use a logic circuit for on-off control of the shunt transistors of the plurality of T-type attenuators. However, the logic circuit has a problem that a circuit configuration is complicated. The present disclosure solves the above problem, and an object thereof is to obtain a variable attenuator having a simple circuit configuration without using a logic circuit. Solution to Problem A variable attenuator according to the present disclosure includes n attenuation resistor circuits and m adjustment resistor circuits connected in parallel to a signal line, in which the n attenuation resistor circuits are on-off controlled by corresponding attenuation amount control signals, each of the n attenuation resistor circuits exhibits a different attenuation amount when being independently on-controlled, the adjustment resistor circuits correspond to k attenuation resistor circuits selected from the n attenuation resistor circuits, and are on-off controlled by a signal of a logical product of k attenuation amount control signals for performing on-off control corresponding to each of the selected k attenuation resistor circuits, and when being on-controlled by a signal of a logical product of the k attenuation amount control signals, attenuation amount of the adjustment resistor circuits are made equal to a sum of attenuation amounts when the k attenuation resistor circuits controlled by the corresponding k attenuation amount control signals are independently on-controlled together with a sum of attenuation amounts by the selected k attenuation resistor circuits simultaneously on-controlled by the corresponding k attenuation amount control signals. Advantageous Effects of Invention According to the present disclosure, an attenuation amount width can be changed stepwise in three or more steps with a simple circuit configuration without providing a logic circuit for attenuation amount control. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a circuit diagram illustrating a variable attenuator according to a first embodiment. FIG. 2 is a schematic circuit diagram illustrating a variable attenuator according to a second embodiment. FIG. 3 is a circuit diagram illustrating a variable attenuator according to a third embodiment. FIG. 4 is a schematic circuit diagram illustrating a variable attenuator according to a fourth embodiment. DESCRIPTION OF EMBODIMENTS First Embodiment A variable attenuator according to a first embodiment will be described with reference to FIG. 1. The variable attenuator according to the first embodiment is applied to a variable attenuator integrated on a gallium arsenide (GaAs) substrate. The variable attenuator according to the first embodiment is a variable T-type attenuator having a plurality of attenuation amounts and having step widths of the plurality of attenuation amounts at equal intervals. The variable attenuator according to the first embodiment includes n attenuation resistor circuits 11 and 12 with n being a natural number equal to or more than 2 and m adjustment resistor circuits 2 with m being a natural number. In the n attenuation resistor circuits 11 and 12, an N-th (Nis a natural number from 1 to n) attenuation resistor circuit IN attenuates an attenuation amount of 2N-1 dB. In the present disclosure, the attenuation amount of 2N-1 dB includes a technical range obtained by multiplying 2N-1 by a coefficient α, and the coefficient will be described as 1 because it is complicated for description. Each of the m adjustment resistor circuits 2 corresponds to a selected plurality of attenuation resistor circuits among the n attenuation resistor circuits 11 and 12, and is adjusted in such a manner that a sum of attenuation amounts when the selected plurality of attenuation resistor circuits is enabled simultaneously is equal to a sum of attenuation amounts