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 apparatus, comprising:
an ultrasonic transducer;
a receive circuit coupled to the ultrasonic transducer and configured to receive an output signal from the 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 receive circuit, and the input terminal being switchably coupled to the first or second output terminals; and
an analog averaging circuit having first and second input terminals coupled to the first and second output terminals, respectively, of the switching circuit;
wherein:
the analog averaging circuit is configured to output an analog averaged signal representing an average of a plurality of output signals from a plurality of ultrasonic transducers, the plurality of output signals from the plurality of ultrasonic transducers including the output signal from the ultrasonic transducer;
the analog averaging circuit comprises a feedback resistor; and
the apparatus 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.
2. The apparatus of claim 1 , wherein the analog averaging circuit is 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.
3. The apparatus of claim 1 , wherein the analog averaging circuit comprises an amplifier.
4. The apparatus of claim 1 , wherein:
the ultrasonic transducer is a first ultrasonic transducer and the receive circuit is a first receive circuit;
the apparatus further comprises a second ultrasonic transducer and a second receive circuit coupled to 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.
5. The apparatus of claim 1 , wherein the ultrasonic transducer, the receive circuit, the switching circuit, and the analog averaging circuit are monolithically integrated on a same semiconductor chip.
6. An apparatus, comprising:
an ultrasonic transducer;
a receive circuit coupled to the ultrasonic transducer and configured to receive an output signal from the 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 receive circuit, and the input terminal being switchably coupled to the first or second output terminals;
an analog averaging circuit having first and second input terminals coupled to the first and second output terminals, respectively, of the switching circuit;
an auto-zeroing circuit coupled to an output of the analog averaging circuit;
an attenuator coupled to an output of the auto-zeroing circuit; and
a low-pass filter and fixed gain amplifier coupled to an output of the attenuator.
7. A method for processing a plurality of ultrasound signals, comprising:
receiving the plurality of ultrasound signals at a switching circuit, the switching circuit having first and second outputs;
outputting the plurality of ultrasound signals to the first and/or second outputs; and
averaging a first value on the first output and a second value on the second output to produce an analog signal,
wherein averaging the first value on the first output and the second value on the second output comprises setting a resistance value based on a number of ultrasound signals in the plurality of ultrasound signals.
8. The method of claim 7 , wherein averaging the first value on the first output and the second value on the second output comprises adding the first value and the second value.
9. The method of claim 7 , wherein averaging the first value on the first output and the second value on the second output comprises subtracting the first value from the second value.
10. The method of claim 7 , further comprising auto-zeroing a result of the averaging.
11. The method of claim 10 , further comprising attenuating a result of the auto-zeroing.
12. The method of claim 11 , further comprising low-pass filtering and amplifying with a fixed gain a result of the attenuating.