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US-12627281-B2 - Multi-level digital step attenuator and digital step attenuation device

US12627281B2US 12627281 B2US12627281 B2US 12627281B2US-12627281-B2

Abstract

A multi-level digital step attenuator (DSA) with a hybrid attenuation circuit is shown. The hybrid attenuation circuit is coupled between an input node and an output node of the multi-level DSA. The bypass switch of the multi-level DSA is controlled to provide a bypass path between the input node and the output node of the of the multi-level DSA when the hybrid attenuation circuit is in a disabled state. In the first active state, the hybrid attenuation circuit is switched to form a T-type structure to provide a first amount of signal attenuation. In the second active state, the hybrid attenuation circuit is switched to form a Pi-type structure to provide a second amount of signal attenuation.

Inventors

  • Wei-Hsin Tseng
  • Jhen-Kai Wang

Assignees

  • MEDIATEK INC.

Dates

Publication Date
20260512
Application Date
20231226

Claims (13)

  1. 1 . A multi-level digital step attenuator, comprising: a hybrid attenuation circuit, coupled between an input node and an output node of the multi-level digital step attenuator, wherein the hybrid attenuation circuit comprises: a first electronic component and a second electronic component, coupled in series between the input node and the output node of the multi-level digital step attenuator; a third electronic component, coupling a connection node between the first electronic component and the second electronic component to a ground terminal in a first active state of the hybrid attenuation circuit, to form a T-type structure with the first electronic component and the second electronic component and so that the hybrid attenuation circuit in the first active state provides a first amount of signal attenuation; and a fourth electronic component and a fifth electronic component, wherein in a second active state of the hybrid attenuation circuit, the fourth electronic component is coupled between the input node of the multi-level digital step attenuator and the ground terminal, and the fifth electronic component is coupled between the output node of the multi-level digital step attenuator and the ground terminal, to form a Pi-type structure with the first electronic component and the second electronic component and so that the hybrid attenuation circuit in the second active state provides a second amount of signal attenuation; a bypass switch, controlled to provide a bypass path between the input node and the output node of the multi-level digital step attenuator when the hybrid attenuation circuit is in a disabled state.
  2. 2 . The multi-level digital step attenuator as claimed in claim 1 , controlled by a 2-bit control signal to switch the hybrid attenuation circuit between the disabled state, the first active state and the second active state.
  3. 3 . The multi-level digital step attenuator as claimed in claim 1 , wherein: the first electronic component, second electronic component, third electronic component, fourth electronic component, and fifth electronic component are resistors; each of the first electronic component and the second electronic component has a resistance of 36 ohm; the third electronic component has a resistance of 16 ohm; and each of the fourth electronic component and the fifth electronic component has a resistance of 96 ohm.
  4. 4 . The multi-level digital step attenuator as claimed in claim 1 , wherein the hybrid attenuation circuit further comprises: a sixth electronic component, coupled between the input node and the output node of the multi-level digital step attenuator when the hybrid attenuation circuit is in the second active state.
  5. 5 . The multi-level digital step attenuator as claimed in claim 4 , wherein: the T-type structure provides signal attenuation of 2{circumflex over ( )}n dB or any attenuation of non-radix-2, and n is a positive integer; and the Pi-type structure provides signal attenuation of 2 (n−1) dB or any attenuation of non-radix-2.
  6. 6 . The multi-level digital step attenuator as claimed in claim 4 , wherein: the first electronic component, second electronic component, third electronic component, fourth electronic component, fifth electronic component, and sixth electronic component are resistors; each of the first electronic component and the second electronic component has a resistance of 36 ohm; the third electronic component has a resistance of 16 ohm; each of the fourth electronic component and the fifth electronic component has a resistance of 116 ohm; and the sixth electronic component has a resistance of 195 ohm.
  7. 7 . The multi-level digital step attenuator as claimed in claim 1 , wherein: the T-type structure provides signal attenuation of 2{circumflex over ( )}n dB or any attenuation of non-radix-2, and n is a positive integer.
  8. 8 . A digital step attenuation device, comprising: multiple stages of digital step attenuation units, wherein at least one digital step attenuation unit in the multiple stages is implemented by the multi-level digital step attenuator as claimed in claim 1 .
  9. 9 . The digital step attenuation device as claimed in claim 8 , wherein: the digital step attenuation units form four stages numbered from 0 to 3; the digital step attenuation unit implemented by the multi-level digital step attenuator is in the number 3 stage; the T-type structure of the multi-level digital step attenuator implementing the digital step attenuation unit in the number 3 stage provides signal attenuation of 16 dB; the Pi-type structure of the multi-level digital step attenuator implementing the digital step attenuation unit in the number 3 stage provides signal attenuation of 8 dB; when enabled, the digital step attenuation units in the number 0 stage, the number 1 stage, and the number 2 stage provide signal attenuation of 1 dB, 2 dB, and 4 dB, respectively; and the digital step attenuation device provides more than 16 attenuation levels.
  10. 10 . The digital step attenuation device as claimed in claim 8 , wherein: the multiple stages of digital step attenuation units are numbered from 0 to (m−1), and m is a positive integer greater than 1; and the digital step attenuation unit implemented by the multi-level digital step attenuator is in the number (m−1) stage.
  11. 11 . The digital step attenuation device as claimed in claim 10 , wherein: the T-type structure of the multi-level digital step attenuator implementing the digital step attenuation unit in the number (m−1) stage provides signal attenuation of 2{circumflex over ( )}m dB; and the Pi-type structure of the multi-level digital step attenuator implementing the digital step attenuation unit in the number (m−1) stage provides signal attenuation of 2{circumflex over ( )}(m−1) dB.
  12. 12 . The digital step attenuation device as claimed in claim 11 , wherein: when enabled, the digital step attenuation units in the number 0 to the number (m−2) stages provide signal attenuation of 2{circumflex over ( )}0 dB to 2{circumflex over ( )}(m−2) dB, respectively.
  13. 13 . The digital step attenuation device as claimed in claim 12 , providing more than 2{circumflex over ( )}m attenuation levels.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63/480,314, filed Jan. 18, 2023, the entirety of which is incorporated by reference herein BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a digital step attenuation technology. Description of the Related Art In radio signal (RF) applications, a digital step attenuator (DSA) is a device that attenuates or reduces the amplitude of the RF signal that passes through it. The channel gain of the wireless receiver or transmitter (Rx/Tx), therefore, can be well controlled. The accuracy of the DSA will affect the reliability of the gain range of the channel, and therefore determine the usability of the Rx/Tx. Generally, the amount of attenuation is controlled digitally. A conventional DSA can be digitally switched between two modes. In an attenuation mode, the RF signal is attenuated by an attenuation circuit of the DSA. In a normal bypass mode, the RF signal is allowed to pass through by a bypass switch rather than by the attenuation circuit. Multiple DSAs may be coupled in series to provide more levels of signal attenuation. However, more stages may require more complex LC matching networks for wideband impedance matching. How to reduce the number of DSA stages is an important topic in this field of technology. BRIEF SUMMARY OF THE INVENTION A multi-level digital step attenuator (DSA) with a single bypass switch and a hybrid attenuation circuit is shown. A multi-level DSA in accordance with an exemplary embodiment of the disclosure has a hybrid attenuation circuit and a bypass switch. The hybrid attenuation circuit is coupled between an input node and an output node of the multi-level DSA. The bypass switch is controlled to provide a bypass path between the input node and the output node of the multi-level DSA when the hybrid attenuation circuit is in a disabled state. In a first active state, the hybrid attenuation circuit is switched to form a T-type structure to provide a first amount of signal attenuation. In a second active state, the hybrid attenuation circuit is switched to from a Pi-type structure to provide a second amount of signal attenuation. The proposed multi-level DSA is controlled by a 2-bit control signal to switch the hybrid attenuation circuit between the disabled state, the first active state and the second active state. A 2-bit control signals, 3 states, and single bypass switch 1.5-bit-DSA is shown. In comparison with the conventional DSA design, fewer stages of DSAs are required for wide-range and high resolution attenuation. In an exemplary embodiment, the hybrid attenuation circuit has a first electronic component and a second electronic component coupled in series between the input node and the output node of the multi-level DSA. The hybrid attenuation circuit further has a third electronic component that couples a connection node between the first electronic component and the second electronic component to a ground terminal when the hybrid attenuation circuit is in the first active state. A T-type structure is formed by the first, second and third electronic components. In an exemplary embodiment, the hybrid attenuation circuit further has a fourth electronic component and a fifth electronic component. The fourth electronic component is coupled between the input node of the multi-level DSA and the ground terminal when the hybrid attenuation circuit is in the second active state. The fifth electronic component is coupled between the output node of the multi-level DSA and the ground terminal when the hybrid attenuation circuit is in the second active state. A Pi-type structure is formed by the first, second, fourth and fifth electronic components. In another exemplary embodiment, the hybrid attenuation circuit further has a sixth electronic component coupled between the input node and the output node of the multi-level DSA when the hybrid attenuation circuit is in the second active state. The first, second, fourth, fifth, and sixth electronic components also form a Pi-type structure. In an exemplary embodiment, n is a positive integer. The T-type structure formed by the first, second, and third electronic components provides signal attenuation of 2{circumflex over ( )}n dB, and the Pi-type structure formed by the first, second, fourth, fifth and sixth electronic components provides signal attenuation of 2{circumflex over ( )}(n−1) dB. It is convenient for digital design. In an exemplary embodiment, a digital step attenuation device formed by multiple stages of digital step attenuation units is shown. At least one digital step attenuation unit in the multiple stages is implemented by the aforementioned multi-level DSA. A detailed description is given in the following embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The present invention can be more fully understood by reading the subsequent detailed des