Parameterizable bandpass delta-sigma modulator

• US 10,181,862 B1
• Filed: 01/24/2018
• Issued: 01/15/2019
• Est. Priority Date: 01/24/2018
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Marr, Harry B., Thompson, Daniel, Yeary, Mark B.
• Primary Examiner(s): Perez, James M
• Application Number:
  US15/879,024
• Time in Patent Office: 356 Days
• Field of Search: 375242-254, 375259, 375285, 375295-296, 375316, 375346-351, 375354-355
• CPC Class Codes: H03H 17/0294 Variable filters; Programmable filters
• CPC Class Codes: H03M 3/324 characterised by means or methods for compensating or preventing more than one type of error at a time, e.g. by synchronisation or using a ratiometric arrangement
• CPC Class Codes: H03M 3/396 among different frequency bands
• CPC Class Codes: H03M 3/404 characterised by the type of bandpass filters used
• CPC Class Codes: H03M 3/464 Details of the digital/analogue conversion in the feedback path
• CPC Class Codes: H04B 1/0017 Digital filtering H04B1/001 takes precedence; digital filters per se H03H17/00
• CPC Class Codes: H04B 1/04 Circuits
• CPC Class Codes: H04B 2001/0491 with frequency synthesizers, frequency converters or modulators
• CPC Class Codes: H04B 7/0617 for beam forming

Abstract

A delta-sigma modulator (DSM) includes: a first summation circuit coupled to an input signal for subtracting an error feedback signal from the input signal; a tunable signal transfer function coupled to the first summation circuit for setting a desired pole in a frequency response of the DSM; a second summation circuit coupled to the tunable signal transfer function for adding a noise transfer function to an output of the tunable signal transfer function; and a quantizer coupled to the second summation circuit for quantizing an output of the second summation circuit to generate an output of the DSM. The output of the DSM is used as feedback to the first summation circuit as the error feedback signal, and the tunable signal transfer function is dynamically tuned to allow selecting and tuning a center frequency and a bandwidth of the DSM.

Claims

1. A parameterizable bandpass delta-sigma modulator (DSM) comprising:

a first summation circuit coupled to an input signal for subtracting an error feedback signal from the input signal;

a tunable signal transfer function coupled to the first summation circuit for setting a desired pole in a frequency response of the DSM;

a second summation circuit coupled to the tunable signal transfer function at a first input port and to a noise transfer function at a second input port for adding the noise transfer function to an output of the tunable signal transfer function; and

a quantizer coupled to the second summation circuit for quantizing an output of the second summation circuit that includes the noise transfer function and the output of the tunable signal transfer function to generate an output of the DSM, wherein the output of the DSM is used as feedback to the first summation circuit as the error feedback signal, and wherein the tunable signal transfer function is dynamically tuned to allow selecting and tuning a center frequency and a bandwidth of the DSM, and wherein the center frequency of the DSM is tuned by placing a zero of the noise transfer function at the center frequency.

2. The parameterizable DSM of claim 1, further comprising a digital-to-analog converter (DAC) for converting the output of the DSM to an analog signal and inputting the analog signal to the first summation circuit as the error feedback signal.

3. The parameterizable DSM of claim 1, wherein the tunable signal transfer function is implemented as a finite impulse response (FIR) filter.

4. The parameterizable DSM of claim 1, wherein the tunable signal transfer function is dynamically tuned by placing a pole of the tunable signal transfer function at the center frequency.

5. The parameterizable DSM of claim 1, wherein the bandwidth of the DSM is tuned by an oversampling ratio, defined as a sampling rate divided by a desired instantaneous bandwidth, and wherein the oversampling ratio sets a maximum dynamic range for the desired instantaneous bandwidth.

6. The parameterizable DSM of claim 1 implemented in a Gallium Nitride circuit.

7. The parameterizable DSM of claim 1, further comprising a second tunable signal transfer function for setting a second desired pole in the frequency response of the DSM to increase an order of the DSM.

8. The parameterizable DSM of claim 4, wherein coefficients for the pole of the tunable signal transfer function to maximize signal-to-noise ratio (SNR) or maximize the bandwidth are determined by a Monte Carlo simulation.

9. The parameterizable DSM of claim 8, wherein the tunable signal transfer function is tuned using the coefficients.

10. A method for tuning a delta-sigma modulator (DSM), the method comprising:

receiving an input signal;

subtracting an error feedback signal from the input signal;

setting a desired pole in a tunable signal transfer function of the DSM;

adding a noise transfer function to an output of the tunable signal transfer function to generate a combined signal that includes an output of the signal transfer function summed with the noise transfer function; and

quantizing the combined signal that includes an output of the signal transfer function summed with the noise transfer function to generate an output of the DSM, wherein the output of the DSM is feedback as the error feedback signal to be subtracted from the input signal, and wherein the tunable signal transfer function is dynamically tuned to allow selecting and tuning a center frequency and a bandwidth of the DSM, and wherein the center frequency of the DSM is tuned by placing a zero of the noise transfer function at the center frequency.

11. The method of claim 10, further comprising converting the output of the DSM to an analog signal and inputting the analog signal to the first summation circuit as the error feedback signal.

12. The method of claim 10, wherein the tunable signal transfer function is dynamically tuned by placing a pole of the tunable signal transfer function at the center frequency.

13. The method of claim 10, wherein the bandwidth of the DSM is tuned by an oversampling ratio, defined as a sampling rate divided by a desired instantaneous bandwidth, and wherein the oversampling ratio sets a maximum dynamic range for the desired instantaneous bandwidth.

14. An antenna array comprising:

a plurality of antennas; and

a beamforming circuit including a parameterizable bandpass delta-sigma modulator (DSM) comprising;

a first summation circuit coupled to an input signal for subtracting an error feedback signal from the input signal;

a tunable signal transfer function coupled to the first summation circuit for setting a desired pole in a frequency response of the DSM;

a second summation circuit coupled to the tunable signal transfer function at a first input port and to a noise transfer function at a second input port for adding the noise transfer function to an output of the tunable signal transfer function; and

a quantizer coupled to the second summation circuit for quantizing an output of the second summation circuit that includes the noise transfer function and the output of the tunable signal transfer function to generate an output of the DSM, wherein the output of the DSM is used as feedback to the first summation circuit as the error feedback signal, and wherein the tunable signal transfer function is dynamically tuned to allow selecting and tuning a center frequency and a bandwidth of the DSM, and wherein the center frequency of the DSM is tuned by placing a zero of the noise transfer function at the center frequency.

15. The antenna array of claim 14, wherein the parameterizable DSM further comprises a digital-to-analog converter (DAC) for converting the output of the DSM to an analog signal and inputting the analog signal to the first summation circuit as the error feedback signal.

16. The antenna array of claim 15, wherein the tunable signal transfer function is implemented as a finite impulse response (FIR) filter.

17. The antenna array of claim 14, wherein the tunable signal transfer function is dynamically tuned by placing a pole of the tunable signal transfer function at the center frequency.