Controlling an output signal independently of the first harmonic
A method includes configuring a transmitter to provide at least three output levels used to form an output signal. The method further includes adjusting a duration of at least one of the output levels to control an average value of the output signal independently of an amplitude of a first harmonic of the output signal.
1. An integrated circuit comprising:
a transmitter that cyclically forms an output signal using at least three voltage states, the output signal having:
an average value V DCB ;
an amplitude V F of a fundamental frequency component; and
a period T of the fundamental frequency component, the period T including:
a duration D 0 of an intermediate state voltage;
a duration D + of a high state voltage above the intermediate state voltage; and
a duration D − of a low state voltage below the intermediate state voltage; and
processing logic that controls the average value V DCB by adjusting at least one of duration D + and duration D − to vary a difference therebetween.
2. The integrated circuit of claim 1 , further comprising a receiver with an input terminal configured to directly connect with a piezoelectric transducer driven by the output signal, the average value V DCB corresponding to a desired DC bias for the input terminal.
3. The integrated circuit of claim 1 , wherein the processing logic further controls the amplitude V F by adjusting at least one of duration D + and duration D − to vary their sum.
4. The integrated circuit of claim 3 , wherein the processing logic controls the amplitude V F by varying both duration D + and duration D − to maintain the difference therebetween.
5. The integrated circuit of claim 3 , wherein the processing logic controls the amplitude V F by measuring a supply voltage and responsively adjusting at least one of duration D + and duration D − .
6. The integrated circuit of claim 5 , wherein the intermediate state voltage is a ground voltage, the high state voltage is a positive voltage, and the low state voltage is a negative voltage, and wherein the integrated circuit comprises a charge pump that provides both the positive and negative voltages.
7. A method that comprises manufacturing an integrated circuit having:
a transmitter that cyclically forms an output signal using at least three voltage states, the output signal having:
an average value V DCB ;
an amplitude V F of a fundamental frequency component; and
a period T of the fundamental frequency component, the period T including:
a duration D 0 of an intermediate state voltage;
a duration D + of a high state voltage above the intermediate state voltage; and
a duration D − of a low state voltage below the intermediate state voltage; and
processing logic that controls the average value V DCB by adjusting at least one of duration D + and duration D − to vary a difference therebetween.
8. The method of claim 7 , wherein the integrated circuit further includes a receiver with an input terminal configured to directly connect with a piezoelectric transducer driven by the output signal, the average value V DCB corresponding to a desired DC bias for the input terminal.
9. The method of claim 7 , wherein the processing logic further controls the amplitude V F by adjusting at least one of duration D + and duration D − to vary their sum.
10. The method of claim 9 , wherein the processing logic controls the amplitude V F by varying both duration D + and duration D − to maintain the difference therebetween.
11. The method of claim 9 , wherein the processing logic controls the amplitude V F by measuring a supply voltage and responsively adjusting at least one of duration D + and duration D − .
12. The method of claim 11 , wherein the intermediate state voltage is a ground voltage, the high state voltage is a positive voltage, and the low state voltage is a negative voltage, and wherein the integrated circuit comprises a charge pump that provides both the positive and negative voltages.
13. A method comprising:
cyclically forming an output signal using at least three voltage states, the output signal having:
an average value V DCB ;
an amplitude V F of a fundamental frequency component; and
a period T of the fundamental frequency component, the period T including:
a duration Do of an intermediate state voltage;
a duration D + of a high state voltage above the intermediate state voltage; and
a duration D − of a low state voltage below the intermediate state voltage; and
controlling the average value V DCB by adjusting at least one of duration D + and duration D − to vary a difference therebetween.
14. The method of claim 13 , further comprising applying the output signal to a piezoelectric transducer terminal, the terminal being electrically connected to a receiver input without a coupling capacitor.
15. The method of claim 13 , further comprising:
controlling the amplitude V F by adjusting at least one of duration D + and duration D − to vary their sum.
16. The method of claim 15 , wherein controlling the amplitude V F is performed by varying both duration D + and duration D − to maintain the difference therebetween.
17. The method of claim 15 , wherein controlling the amplitude V F includes measuring a supply voltage and responsively adjusting at least one of duration D + and duration D − .