Transimpedance amplifier (TIA) with tunable input resistance

Patent metadata

Field	Value
Publication number	US-11595069-B2
Application number	US-202117375843-A
Country	US
Kind code	B2
Filing date	Jul 14, 2021
Priority date	Jul 14, 2021
Publication date	Feb 28, 2023
Grant date	Feb 28, 2023

Abstract

An electronic device may include wireless circuitry with a baseband processor, a transceiver, and an antenna. The transceiver may include a mixer that outputs signals to a transimpedance amplifier. The mixer has an output impedance that varies depending on the frequency of operation. An adjustable resistance can be coupled to the input of the transimpedance amplifier. A control circuit can tune the adjustable resistance to compensate for changes in the output impedance of the mixer as the transceiver operates across a wide range of frequencies.

First claim

What is claimed is:

1. Wireless circuitry operable in a plurality of radio-frequency bands, comprising:
a first amplifier configured to receive a radio-frequency signal via an antenna;
a mixer having a first input coupled to an output of the first amplifier, a second input coupled to an oscillator circuit, and an output;
a second amplifier having first and second amplifier input terminals coupled to the output of the mixer; and
an adjustable resistance having a first terminal coupled at the first amplifier input terminal and having a second terminal coupled at the second amplifier input terminal, the adjustable resistance being configured to adjust an input impedance of the second amplifier as the wireless circuitry is operated across the plurality of radio-frequency bands.

2. The wireless circuitry of claim 1 , further comprising:
a control circuit configured to increase a resistance value of the adjustable resistance as an output impedance of the mixer is decreased and to decrease the resistance value of the adjustable resistance as the output impedance of the mixer is increased.

3. The wireless circuitry of claim 1 , further comprising:
a first shunt capacitor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to a ground line; and
a second shunt capacitor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to the ground line.

4. The wireless circuitry of claim 3 , further comprising:
a first feedback capacitor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to a first amplifier output terminal of the second amplifier; and
a second feedback capacitor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to a second amplifier output terminal of the second amplifier.

5. The wireless circuitry of claim 4 , further comprising:
a first feedback resistor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to the first amplifier output terminal; and
a second feedback resistor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to the second amplifier output terminal.

6. The wireless circuitry of claim 1 , wherein the second amplifier comprises a transimpedance amplifier.

7. The wireless circuitry of claim 1 , wherein:
the adjustable resistance comprises a plurality of resistive strings; and
each resistive string in the plurality of resistive strings comprises a first resistor, a second resistor, and a switch coupled between the first and second resistors in that resistive string.

8. The wireless circuitry of claim 1 , wherein:
the adjustable resistance comprises a plurality of resistive strings; and
each resistive string in the plurality of resistive strings comprises a first switch, a second switch, and a resistor coupled between the first and second switches in that resistive string.

9. A method of operating wireless circuitry in a plurality of radio-frequency bands, comprising:
receiving signals at a first amplifier via an antenna;
mixing signals from the first amplifier and signals from an oscillator at a mixer having an output impedance;
receiving signals at a second amplifier from the mixer; and
tuning an adjustable resistor coupled to an input of the second amplifier based on changes in the output impedance of the mixer as the wireless circuitry is operated across the plurality of radio-frequency bands to provide a first resistance value when the wireless circuitry is operating in a first radio-frequency band in the plurality of radio-frequency bands and to provide a second resistance value greater than the first resistance value when the wireless circuitry is operating in a second radio-frequency band in the plurality of radio-frequency bands greater than the first radio-frequency band.

10. The method of claim 9 , wherein:
the adjustable resistor comprises a plurality of resistive strings each having a first resistor, a second resistor, and a switch coupled between the first and second resistors in that resistive string; and
tuning the adjustable resistor comprises selectively activating and deactivating the switch in each of the plurality of resistive strings.

11. The method of claim 9 , wherein:
the adjustable resistor comprises a plurality of resistive strings each having a first switch, a second switch, and a resistor coupled between the first and second switches in that resistive string; and
tuning the adjustable resistor comprises selectively activating and deactivating the first and second switches in each of the plurality of resistive strings.

12. The method of claim 9 , wherein the second amplifier comprises a transimpedance amplifier having a bandwidth that is greater than 100 MHz.

13. An electronic device comprising:
a mixer having a first input coupled to an antenna, a second input coupled to an oscillator, and an output with a variable output impedance;
an amplifier having inputs coupled to the output of the mixer;
an adjustable resistance coupled across the inputs of the amplifier and configured to adjust an input impedance of the amplifier based on the variable output impedance of the mixer; and
processing circuitry configured to receive data generated based on signals output by the amplifier.

14. The electronic device of claim 13 , further comprising:
a control circuit configured to tune the adjustable resistance as a function of the operating frequency of the amplifier.

15. The electronic device of claim 13 , wherein:
the input of the amplifier comprises a first amplifier input terminal and a second amplifier input terminal; and
the adjustable resistance has a first resistor terminal directly coupled to the first amplifier input terminal and a second resistor terminal directly coupled to the second amplifier input terminal.

16. The electronic device of claim 15 , further comprising:
a first shunt capacitor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to a ground line; and
a second shunt capacitor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to the ground line.

17. The electronic device of claim 16 , wherein the amplifier comprises a first amplifier output terminal and a second amplifier output terminal and wherein the electronic device further comprises:
a first feedback capacitor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to the first amplifier output terminal;
a second feedback capacitor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to the second amplifier output terminal;
a first feedback resistor having a first terminal coupled to the first amplifier input terminal and having a second terminal coupled to the first amplifier output terminal; and
a second feedback resistor having a first terminal coupled to the second amplifier input terminal and having a second terminal coupled to the second amplifier output terminal.

18. The electronic device of claim 13 , wherein the adjustable resistance has a first resistance value when the mixer is operating at a first frequency and has a second resistance value greater than the first resistance value when the mixer is operating at a second frequency greater than

Assignees

• Apple Inc

Inventors

• Woo Sang Hyun
• Mrugalla Florian

Classifications

• H03F2200/451

  the amplifier being a radio frequency amplifier · CPC title

• H03F2200/294

  the amplifier being a low noise amplifier [LNA] · CPC title

• H04B1/1638

  Special circuits to enhance selectivity of receivers not otherwise provided for (resonant circuits H03H) · CPC title

• H04B1/10

  Means associated with receiver for limiting or suppressing noise or interference · CPC title

• H04B1/005 Primary

  adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges · CPC title