# US 8,786,472 B1 · Low complexity non-integer adaptive sample rate conversion

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- Number: US 8,786,472 B1
- Document ID: US8786472B1
- Status: Granted
- Kind: B1
- Application number: 13/770,862
- Filed: 2013-02-19
- Granted: 2014-07-22
- Earliest claimed: 2013-02-19
- Assignees: Raytheon Company
- Applicants: Raytheon Company
- Inventors: Gregary B. Prince
- Web page: https://patentgrep.com/patent/US8786472B1

## CPC

- H03M 7/00: Conversion of a code where information is represented by a given sequence or number of digits to a code where the same {, similar or subset of} information is represented by a different sequence or number of digits
- H03H 17/0294: {Variable filters; Programmable filters}
- H03H 17/0416: {with input-sampling frequency and output-delivery frequency which differ, e.g. extrapolation; Anti-aliasing}
- H03H 17/0685: {the ratio being rational}
- H03M 5/02: Conversion to or from representation by pulses
- H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C)
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)

## Abstract

Generally described herein are methods and systems for sample rate conversion of non-integer and integer factors. In one or more embodiments an apparatus can include a sample rate converter that can include an input configured to receive an input signal with a first frequency and an output configured to provide an output signal with a second frequency different from the first frequency. The sample rate converter can include a filter coefficient lookup table and a numerically controlled oscillator configured to provide filter coefficients from the filter coefficient lookup table at a rate that is a function of the first frequency and the second frequency. The sample rate converter can include a multiplier configured to produce an output that is the product of a filter coefficient of the filter coefficients from the numerically controlled oscillator and a sample of an input signal and an accumulator configured to sum an output of the multiplier and provide a result of the summation when the accumulator receives an indicator to dump the result.

## Claims

### Claim 1

An apparatus comprising:
a transmit sample rate converter comprising:
a first port configured to receive a first signal, the first signal having a first frequency;
a second port configured to provide an second signal, the second signal having a second frequency different from the first frequency;
a transmit filter coefficient lookup table;
a transmit numerically controlled oscillator configured to provide transmit filter coefficients from the transmit filter coefficient lookup table at a rate that is a function of the first frequency divided by the second frequency;
a transmit multiplier configured to multiply a transmit filter coefficient of the transmit filter coefficients from the transmit numerically controlled oscillator and a sample of the first signal; and
a transmit accumulator configured to sum products from the transmit multiplier and provide a result of the summation when the transmit accumulator receives an indicator to dump the result; and
a receive sample rate converter comprising:
a third port configured to receive a third signal, the third signal having the second frequency;
a fourth port configured to provide a fourth signal, the fourth signal having the first frequency;
a receive filter coefficient lookup table;
a receive numerically controlled oscillator configured to provide receive filter coefficients from the receive filter coefficient lookup table at the rate proportional to the first frequency divided by the second frequency;
a receive multiplier configured to multiply a receive filter coefficient of the receive filter coefficients from the receive numerically controlled oscillator and a sample of the third signal; and
a receive accumulator configured to sum products of the receive multiplier and provide a result of the summation when the receive accumulator receives an indicator to dump the result.

### Claim 2 (depends on 1)

The apparatus of claim 1, further comprising:
a digital to analog converter coupled to the transmit sample rate converter and configured to produce an analog signal from results received from the transmit accumulator; and
a band pass filter configured to provide a filtered version of the analog signal.

### Claim 3 (depends on 2)

The apparatus of claim 2, further comprising an analog to digital converter configured to provide samples of the filtered version of the analog signal to the receive sample rate converter.

### Claim 4 (depends on 3)

The apparatus of claim 3, wherein the analog to digital converter and the digital to analog converter are clocked at the same frequency.

### Claim 5 (depends on 4)

The apparatus of claim 4, wherein the receive filter coefficient lookup table includes coefficients corresponding to a Sinc-Blackman filter.

### Claim 6 (depends on 5)

The apparatus of claim 5, wherein the apparatus is a high data rate radio frequency ground modem.

### Claim 7

A method comprising:
receiving, at a first port, a signal, the signal having a first frequency;
providing, using a numerically controlled oscillator, filter coefficients from a filter coefficient lookup table at a rate that is a function of a ratio of the first frequency and a second frequency, wherein the second frequency is a frequency of a second signal the second frequency is different from the first frequency;
multiplying, using a multiplier, a filter coefficient of the filter coefficients from the numerically controlled oscillator and a sample of the input signal;
summing, using an accumulator, products from the multiplier;
providing a result of the summation when the accumulator receives an indicator from the numerically controlled oscillator to dump the result;
converting, using a digital to analog converter, the dumped results to an analog signal; and
filtering, using a band pass filter, the analog signal.

### Claim 8 (depends on 7)

The method of claim 7, further comprising:
transmitting the analog signal to a sample rate converter.

### Claim 9 (depends on 8)

The method of claim 8, further comprising:
sampling, using an analog to digital converter, the filtered analog signal received at the sample rate converter.

### Claim 10 (depends on 9)

The method of claim 9, further comprising:
clocking the digital to analog converter and the analog to digital converter at the same frequency.

### Claim 11 (depends on 10)

The method of claim 10, wherein the input is an input to a high data rate radio frequency ground modem.

### Claim 12

A computer readable storage device including instructions stored thereon, the instructions, which when executed by a machine, cause the machine to perform operations comprising:
providing filter coefficients from a filter coefficient lookup table at a rate that is a function of a ratio of a first frequency and a second frequency, wherein the first frequency is a frequency of a first signal and the second frequency is a frequency of a second signal;
multiplying a filter coefficient of the filter coefficients and a sample of the first signal;
summing results of the multiplication;
providing a result of the summation when an indicator to dump the result is received;
converting the dumped result to an analog signal; and
band pass filtering the analog signal.

### Claim 13 (depends on 12)

The computer readable storage device of claim 12, wherein the instructions further comprise instructions, which when executed by the machine, cause the machine to perform operations comprising:
transmitting the analog signal to a sample rate converter.

### Claim 14 (depends on 13)

The computer readable storage device of claim 13, wherein the instructions further comprise instructions, which when executed by the machine, cause the machine to perform operations comprising:
sampling the filtered analog signal received at the sample rate converter.

### Claim 15 (depends on 14)

The computer readable storage device of claim 14, wherein the instructions further comprise instructions, which when executed by the machine, cause the machine to perform operations comprising:
clocking a digital to analog converter and an analog to digital converter at the same frequency.