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 coupled to the receive circuit, wherein the switching circuit comprises a pair of cross-coupled switches coupled between the input terminal of the switching circuit and the first and second output terminals, the pair of cross-coupled switches operable to control a sign of the output signal of the ultrasonic transducer with respect to a reference value; and
a summation circuit having first and second input terminals switchably coupled to the first and second output terminals of the switching circuit, the summation circuit configured to output an output signal representing a combination of the output signal from the ultrasonic transducer with one or more output signals from one or more other ultrasonic transducers.
2. The apparatus of claim 1 , wherein the ultrasonic transducer is a first ultrasonic transducer, the receive circuit is a first receive circuit, and the switching circuit is a first switching circuit, and wherein the apparatus further comprises a second ultrasonic transducer, a second receive circuit coupled to the second ultrasonic transducer, and a second switching circuit coupled between the second receive circuit and the first and second input terminals of the summation circuit.
3. The apparatus of claim 2 , wherein the first input terminal of the summation circuit is configured to sum a first current output by the first switching circuit and a second current output by the second switching circuit.
4. The apparatus of claim 1 , further comprising a transimpedance amplifier (TIA) coupled between the ultrasonic transducer and the switching circuit, and being upstream of the switching circuit.
5. The apparatus of claim 1 , further comprising an averaging circuit including the summation circuit and configured to output an averaged signal representing a combination of an output signal from the ultrasonic transducer with one or more output signals from one or more other ultrasonic transducers.
6. The apparatus of claim 5 , wherein the averaging circuit is configured to output an averaged signal representing an average of a combination of a first signal received at a first input terminal of the averaging circuit and a second signal received at a second input terminal of the averaging circuit.
7. The apparatus of claim 6 , wherein the averaging circuit comprises a feedback resistor having a variable resistance.
8. The apparatus of claim 1 , wherein the summation circuit is one of a buffer or an amplifier.
9. The apparatus of claim 1 , wherein the summation circuit is an analog circuit and the output signal of the summation circuit is an analog signal.
10. The apparatus of claim 1 , wherein the ultrasonic transducer, receive circuit, switching circuit, and summation circuit are monolithically integrated on a same semiconductor chip.