System and a method for a waveform generator

• US 9,904,311 B1
• Filed: 08/09/2016
• Issued: 02/27/2018
• Est. Priority Date: 08/09/2016
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Cristofoli, Bruno, Scipioni, Marco
• Primary Examiner(s): Vlahos, Sophia
• Application Number:
  US15/232,572
• Publication Number:
  US 20180048501A1
• Time in Patent Office: 567 Days
• CPC Class Codes: G06F 1/022 Waveform generators, i.e. devices for generating periodical functions of time, e.g. direct digital synthesizers G06F1/025, G06F1/03 take precedence
• CPC Class Codes: G06F 2101/02 Linear multivariable functions, i.e. sum of products
• CPC Class Codes: G06F 2101/04 Trigonometric functions

Abstract

According to an embodiment, a waveform generator includes a phase accumulator configured to generate a digital phase signal representing a phase angle, and a phase-to-amplitude converter configured to receive the digital phase signal as a phase input, and generate sine and cosine waveform values as digital amplitude signals, wherein the phase-to-amplitude converter does not include a look-up table.

Claims

1. A waveform generator comprising:

a phase accumulator configured to generate a digital phase signal representing a phase angle; and

a phase-to-amplitude converter configured to receive the digital phase signal as a phase input, and generate sine and cosine waveform values as digital amplitude signals, wherein the phase-to-amplitude converter does not include a look-up table, wherein the phase-to-amplitude converter comprises;

an input stage circuit configured to receive the digital phase signal, determine sine and cosine values of the digital phase signal, and output the determined sine and cosine values of the digital phase signal;

a calculating stage circuit having inputs coupled to outputs of the input stage circuit, the calculating stage circuit configured to calculate sine and cosine values based on the determined sine and cosine values output of the input stage circuit, the calculating stage circuit comprising multiple sum-of-products circuits, each of the multiple sum-of-products circuits comprising multipliers and adders; and

an output stage circuit having inputs coupled to outputs of the calculating stage circuit, the output stage circuit configured to calculate sine and cosine values based on the determined sine and cosine values of the calculating stage circuit, the output stage circuit comprising a sum-of-products circuit, the sum-of-products circuit comprising multipliers and adders, the calculated sine and cosine values forming the digital amplitude signals.

2. The waveform generator of claim 1, wherein each of the sum-of-products circuits further comprises:

a first sine input node and a second sine input node configured to receive a first sine value and a second sine value, respectively;

a first cosine input node and a second cosine input node configured to receive a first cosine value and a second cosine value, respectively;

a first multiplier coupled to the first sine input node and the first cosine input node, the first multiplier configured to output the product of the first sine value and the first cosine value;

a second multiplier coupled to the second cosine input node and the second sine input node, the second multiplier configured to output the product of the second cosine value and the second sine value;

a third multiplier coupled to the second cosine input node and the first cosine input node, the third multiplier configured to output the product of the second cosine value and the first cosine value;

a fourth multiplier coupled to the first sine input node and the second sine input node, the fourth multiplier configured to output the product of the first sine value and the second sine value;

a first adder coupled to the outputs of the first and second multipliers, the first adder configured to output the sum of the output of the first multiplier and the output of the second multiplier; and

a second adder coupled to the outputs of the third and fourth multipliers, the second adder configured to output the difference of the output of the third multiplier and the output of the fourth multiplier.

3. The waveform generator of claim 1, wherein each of the sum-of-products circuits is configured to receive a sine value and a cosine value of a first value, receive a sine value and a cosine value of a second value, output a sine value of the first and second values combined, and output a cosine value of the first and second values combined.

4. The waveform generator of claim 1, wherein the input stage circuit further comprises:

a first sum-of-products circuit configured to receive at least one bit of the digital phase signal, the first sum-of-products circuit configured to calculate sine and cosine values of the at least one bit of the digital phase signal; and

a second sum-of-products circuit configured to receive at least one other bit of the digital phase signal, the second sum-of-products circuit configured to calculate sine and cosine values of the at least one other bit of the digital phase signal.

5. The waveform generator of claim 1, wherein the input stage circuit further comprises:

a first set of multiplexers configured to output first output values based on at least one bit of the digital phase signal, the first output values being sine and cosine values of the at least one bit of the digital phase signal;

a first sum-of-products circuit configured to receive the first output values, the first sum-of-products circuit configured to calculate sine and cosine values of the first output values;

a second set of multiplexers configured to output second output values based on at least one other bit of the digital phase signal, the second output values being sine and cosine values of the at least one other bit of the digital phase signal; and

a second sum-of-products circuit configured to receive the second output values, the second sum-of-products circuit configured to calculate sine and cosine values of the second output values.

6. The waveform generator of claim 1, wherein the input stage circuit further comprises:

a first set of multiplexers configured to select sine and cosine values of a first set of bits of the digital phase signal based on the first set of bits of the digital phase signal; and

a second set of multiplexers configured to select sine and cosine values of a second set of bits of the digital phase signal based on the second set of bits of the digital phase signal.

7. The waveform generator of claim 1, wherein the input stage circuit, the calculating stage circuit, and the output stage circuit each comprise pipeline registers.

8. The waveform generator of claim 1, wherein the digital phase signal comprises at least sixteen bits.

9. A method comprising:

receiving, at a phase-to-amplitude converter, a digital phase signal from a phase accumulator, the digital phase signal representing a phase angle, the phase-to-amplitude converter not including a look-up table and being configured to generate sine and cosine waveform values as digital amplitude signals;

determining, by an input stage of the phase-to-amplitude converter, a first sine value and a first cosine value of at least a first bit of the digital phase signal;

determining, by the input stage of the phase-to-amplitude converter, a second sine value and a second cosine value of at least a second bit of the digital phase signal;

calculating, by a calculating stage of the phase-to-amplitude converter having inputs coupled to outputs of the input stage of the phase-to-amplitude converter, a third sine value and a third cosine value based on the first and second sine values and the first and second cosine values, the calculating stage comprising multiple sum-of-products circuits, each of the multiple sum-of-products circuits comprising multipliers and adders; and

generating, by an output stage of the phase-to-amplitude converter having inputs coupled to outputs of the calculating stage of the phase-to-amplitude converter, the digital amplitude signals based at least partially on the third sine value and the third cosine value, the output stage comprising a sum-of-products circuit, the sum-of-products circuit comprising multipliers and adders.

10. The method of claim 9, wherein the digital phase signal comprises at least sixteen bits.

11. The method of claim 9 further comprising:

calculating, by the calculating stage of the phase-to-amplitude converter, a fourth sine value and a fourth cosine value, the digital amplitude signals being at least partially based on the fourth sine value and the fourth cosine value.

12. The method of claim 9 further comprising:

pipelining the input stage and the output stage with pipeline registers.

13. The method of claim 9, wherein calculating a third sine value and a third cosine value based on the first and second sine values and the first and second cosine values comprises:

adding the product of the first sine value and the second cosine value to the product of the first cosine value and the second sine value to generate the third sine value; and

subtracting the product of the first sine value and the second sine value from the product of the first cosine value and the second cosine value to generate the third cosine value.

14. The method of claim 9, wherein determining the first sine value and the first cosine value of the first bit of the digital phase signal comprises:

selecting the first sine value and the first cosine value with one or more multiplexers in the input stage, outputs of the one or more multiplexers being selected at least partially by the first bit of the digital phase signal.

15. A phase-to-amplitude converter comprising:

a first stage circuit configured to receive, from a phase accumulator, a digital phase signal representing a phase angle, the digital phase signal having at least sixteen bits, the first stage circuit being further configured to determine sine and cosine values of the digital phase signal, and output the determined sine and cosine values of the digital phase signal, the first stage circuit comprising;

an input stage circuit configured to receive the digital phase signal, determine sine and cosine values of the digital phase signal, and output the determined sine and cosine values of the digital phase signal;

a calculating stage circuit having inputs coupled to outputs of the input stage circuit, the calculating stage circuit configured to calculate sine and cosine values based on the determined sine and cosine values output of the input stage circuit, the calculating stage circuit comprising multiple sum-of-products circuits, each of the multiple sum-of-products circuits comprising of multipliers and adders; and

a second stage circuit directly connected to the output of the first stage circuit, the second stage circuit configured to calculate sine and cosine values of the determined sine and cosine values of the digital phase signal, the second stage circuit comprising;

an output stage circuit having inputs coupled to outputs of the calculating stage circuit, the output stage circuit configured to calculate sine and cosine values based on the determined sine and cosine values of the calculating stage circuit, the output stage circuit comprising a sum-of-products circuit, the sum-of-products circuit comprising of multipliers and adders, the calculated sine and cosine values forming digital amplitude signals, wherein the phase-to-amplitude converter does not include a look-up table.

16. The phase-to-amplitude converter of claim 15, wherein the second stage circuit further comprises a pipeline register.