Ultrasound receiver circuitry and related apparatus and methods
Methods and apparatus are described for implementing a coding scheme on ultrasound signals received by a plurality of ultrasonic transducers. The coding, and subsequent decoding, may allow for multiple ultrasonic transducers to be operated in a receive mode simultaneously while still differentiating the contribution of the individual ultrasonic transducers. Improved signal characteristics may result, including improved signal-to-noise ratio (SNR).
1. An ultrasound device, comprising:
a plurality of ultrasonic transducers;
an analog encoding circuit coupled to outputs of the plurality of ultrasonic transducers and configured to apply a Hadamard code to a plurality of output signals from the plurality of ultrasonic transducers;
an analog-to-digital converter (ADC) coupled to an output of the analog encoding circuit; and
a digital decoding circuit coupled to an output of the ADC.
2. The ultrasound device of claim 1 , wherein the analog encoding circuit is operable to encode a positive signal during a first acquisition window and a negative signal during a second acquisition window.
3. The ultrasound device of claim 1 , wherein the analog encoding circuit is further configured to:
generate a first encoded signal representative of a sum between a first output signal of a first ultrasonic transducer of the plurality of ultrasonic transducers and a second output signal of a second ultrasonic transducer of the plurality of ultrasonic transducers during a first acquisition window, and
generate a second encoded signal representative of a difference between the first output signal and the second output signal during a second acquisition window.
4. The ultrasound device of claim 1 , wherein the analog encoding circuit comprises:
an analog averaging circuit configured to output an analog averaged signal representing an average of the plurality of output signals from the plurality of ultrasonic transducers.
5. The ultrasound device of claim 4 , wherein the analog encoding circuit further comprises:
a first receive circuit coupled to a first ultrasonic transducer of the plurality of ultrasonic transducers and configured to receive an output signal from the first ultrasonic transducer;
a switching circuit having an input terminal and first and second output terminals, the input terminal configured to receive an output signal from the first receive circuit, and the input terminal being switchably coupled to the first or second output terminals, wherein
the analog averaging circuit has first and second input terminals coupled to the first and second output terminals, respectively, of the switching circuit.
6. The ultrasound device of claim 5 , wherein the analog averaging circuit is further configured to output the analog averaged signal by averaging a first signal received at a first input terminal of the analog averaging circuit and a second signal received at a second input terminal of the analog averaging circuit.
7. The ultrasound device of claim 5 , wherein the analog encoding circuit further comprises:
a second receive circuit coupled to a second ultrasonic transducer of the plurality of ultrasonic transducers and configured to receive an output signal from the second ultrasonic transducer; and
the switching circuit is configured to sum at the first output terminal a first current signal from the first receive circuit and a second current signal from the second receive circuit.
8. The ultrasound device of claim 5 , wherein the plurality of ultrasonic transducers, the first receive circuit, the switching circuit, and the analog averaging circuit are monolithically integrated on a same semiconductor chip.
9. The ultrasound device of claim 4 , wherein the analog averaging circuit comprises a feedback resistor; and
the ultrasound device further comprises a control circuit configured to control a resistance value of the feedback resistor based on a number of the plurality of output signals from the plurality of ultrasonic transducers.
10. A method of processing ultrasound signals, comprising:
receiving ultrasound signals with a plurality of ultrasonic transducers;
producing, from the plurality of ultrasonic transducers, a plurality of analog output signals representing the ultrasound signals received by the plurality of ultrasonic transducers;
encoding the plurality of analog output signals using a Hadamard code to produce a plurality of analog encoded signals;
digitizing the plurality of analog encoded signals to produce a plurality of digital encoded signals; and
decoding the plurality of digital encoded signals.
11. The method of claim 10 , wherein encoding the plurality of analog output signals comprises producing an analog encoded signal based on analog output signals produced from at least two ultrasonic transducers of the plurality of ultrasonic transducers during a same time duration.
12. The method of claim 10 , wherein decoding the plurality of digital encoded signals comprises applying a Hadamard code.
13. The method of claim 10 , wherein encoding the plurality of analog output signals comprises:
encoding a positive signal during a first acquisition window and a negative signal during a second acquisition window.
14. The method of claim 10 , wherein encoding the plurality of analog output signals comprises:
generating a first output signal representative of a sum between a first analog output signal received from a first ultrasonic transducer of the plurality of ultrasonic transducers and a second analog output signal received from a second ultrasonic transducer of the plurality of ultrasonic transducers during a first acquisition window, and
generate a second output signal representative of a difference between the first analog output signal and the second analog output signal during a second acquisition window.
15. The method of claim 10 , wherein encoding the plurality of analog output signals comprises:
outputting, with an analog averaging circuit, an analog averaged signal representing an average of a plurality of analog output signals from the plurality of ultrasonic transducers.
16. The method of claim 15 , wherein encoding the plurality of analog output signals further comprises:
receiving, at an input terminal of a switching circuit, analog output signals representing ultrasound signals received from a first ultrasonic transducer of the plurality of ultrasonic transducers;
switchably coupling the input terminal of the switching circuit to a first terminal or a second output terminal of the switching circuit, wherein
the analog averaging circuit has first and second input terminals coupled to the first and second output terminals, respectively, of the switching circuit.
17. The method of claim 16 , wherein outputting the analog averaged signal comprises averaging a first signal received at a first input terminal of the analog averaging circuit and a second signal received at a second input terminal of the analog averaging circuit.
18. The method of claim 10 , wherein encoding the plurality of analog output signals comprises normalizing some or all of the plurality of analog output signals.