US 6,459,743 B1 · Digital reception with radio frequency sampling

Abstract

A radio frequency signal is received by using a sigma-delta analog-to-digital converter to sample the radio frequency signal at a sampling rate and to generate therefrom 1-bit digital samples representing a digital intermediate frequency signal. The intermediate frequency signal is demodulated to generate in-phase and quadrature samples. Demodulation may be performed by generating a first mixed signal by combining the 1-bit digital samples representing the intermediate frequency signal with a first sequence representing a cosine mixing signal; generating a second mixed signal by combining the 1-bit digital samples representing the intermediate frequency signal with a second sequence representing a sine mixing signal; and decimating the first and second mixed signals to generate the in-phase and quadrature samples. In alternative embodiments, the intermediate frequency signal is directly converted to in-phase and quadrature signals by using bandpass decimation filtering to subsample two time-shifted sequences of the intermediate frequency. In another alternative, the sigma-delta analog-to-digital converter uses subsampling to convert the radio frequency signal to a first intermediate frequency, and a decimation filter is used to further convert the signal to a second intermediate frequency. An IQ demodulator then reconstructs the in-phase and quadrature signals from the second intermediate frequency signal.

Claims28

Dependent claims

A receiver, comprising:

means for receiving a radio frequency signal;
a sigma-delta analog-to-digital converter that samples the radio frequency signal at a sampling rate and generates therefrom 1-bit digital samples representing a digital intermediate frequency signal, wherein the intermediate frequency is one fourth of the sampling rate;
and
a demodulator for generating in-phase and quadrature samples from the digital intermediate frequency signal, wherein the demodulator comprises:
a first mixer that generates a first mixed signal by combining the 1-bit digital samples representing the digital intermediate frequency signal with a first sequence representing a cosine mixing signal, wherein the first mixer is a first exclusive-OR logic gate having a first input coupled to receive the 1-bit digital samples representing the digital intermediate frequency signal, and a second input coupled to receive the first sequence representing the cosine mixing signal;
a second mixer that generates a second mixed signal by combining the 1-bit digital samples representing the digital intermediate frequency signal with a second sequence representing a sine mixing signal, wherein the second mixer is a second exclusive-OR logic gate having a first input coupled to receive the 1-bit digital samples representing the digital intermediate frequency signal, and a second input coupled to receive the second sequence representing the sine mixing signal;
and
means for decimating the first and second mixed signals to generate the in-phase and quadrature samples.

5 more elements

A receiver, comprising:

means for receiving a radio frequency signal;
a sigma-delta analog-to-digital converter that samples the radio frequency signal at a sampling rate and generates therefrom 1-bit digital samples representing a digital intermediate frequency signal;
and
a demodulator for generating in-phase and quadrature samples from the digital intermediate frequency signal, wherein the demodulator comprises:
decimation means for receiving the 1-bit digital samples representing the digital intermediate frequency signal and generating therefrom first and second decimated signals, wherein:
the first decimated signal is based on the 1-bit digital samples;
the second decimated signal is based on a time-shifted version of the 1-bit digital samples;
each of the first and second decimated signals has one sample for every number, N, of 1-bit digital samples representing the intermediate frequency;
and
the time-shifted version of the 1-bit digital samples is the 1-bit digital samples delayed by an amount, Δn cycles of the sampling rate;
and
means for bandpass filtering the first decimated signal to generate the in-phase samples, and for bandpass filtering the second decimated signal to generate the quadrature samples.

9 more elements

A receiver, comprising:

means for receiving a radio frequency signal;
a sigma-delta analog-to-digital converter that samples the radio frequency signal at a sampling rate and generates therefrom 1-bit digital samples representing a digital intermediate frequency signal, wherein the intermediate frequency is one fourth of the sampling rate;
and
a demodulator for generating in-phase and quadrature samples from the digital intermediate frequency signal, wherein the demodulator comprises:
a first mixer that generates a first mixed signal by combining the 1-bit digital samples representing the digital intermediate frequency signal with a first sequence representing a cosine mixing signal, wherein the first mixer is a first exclusive-OR logic gate having a first input coupled to receive the 1-bit digital samples representing the digital intermediate frequency signal, and a second input coupled to receive the first sequence representing the cosine mixing signal;
a second mixer that generates a second mixed signal by combining the 1-bit digital samples representing the digital intermediate frequency signal with a second sequence representing a sine mixing signal, wherein the second mixer is a second exclusive-OR logic gate having a first input coupled to receive the 1-bit digital samples representing the digital intermediate frequency signal, and a second input coupled to receive the second sequence representing the sine mixing signal;
analog filter means for filtering the first and second mixed signals to generate in-phase and quadrature signals;
and
analog-to-digital conversion means for converting the in-phase and quadrature signals into the in-phase and quadrature samples.

6 more elements

A method receiving a signal, comprising the steps of:

receiving a radio frequency signal;
using a sigma-delta analog-to-digital converter to sample the radio frequency signal at a sampling rate and to generate therefrom 1-bit digital samples representing a digital intermediate frequency signal, wherein the intermediate frequency is one fourth of the sampling rate;
and
demodulating the digital intermediate frequency signal to generate in-phase and quadrature samples, wherein the step of demodulating comprises the steps of:
generating a first mixed signal by combining the 1-bit digital samples representing the digital intermediate frequency signal with a first sequence representing a cosine mixing signal, wherein the step of generating the first mixed signal comprises the step of performing an exclusive-OR operation between corresponding ones of the 1-bit digital samples representing the digital intermediate frequency signal, and the first sequence representing the cosine mixing signal;
generating a second mixed signal by combining the 1-bit digital samples representing the digital intermediate frequency signal with a second sequence representing a sine mixing signal, wherein the step of generating the second mixed signal comprises the step of performing an exclusive-OR operation between corresponding ones of the 1-bit digital samples representing the digital intermediate frequency signal, and the second sequence representing the sine mixing signal;
and
decimating the first and second mixed signals to generate the in-phase and quadrature samples.

5 more elements

A method of receiving a signal, comprising the steps of:

receiving a radio frequency signal;
using a sigma-delta analog-to-digital converter to sample the radio frequency signal at a sampling rate and to generate therefrom 1-bit digital samples representing a digital intermediate frequency signal, wherein the intermediate frequency is one fourth of the sampling rate;
and
demodulating the digital intermediate frequency signal to generate in-phase and quadrature samples, wherein the step of demodulating comprises:
generating a first mixed signal by combining the 1-bit digital samples representing the digital intermediate frequency signal with a first sequence representing a cosine mixing signal, wherein the step of generating the first mixed signal comprises the step of performing an exclusive-OR operation between corresponding ones of the 1-bit digital samples representing the digital intermediate frequency signal, and the first sequence representing the cosine mixing signal;
generating a second mixed signal by combining the 1-bit digital samples representing the digital intermediate frequency signal with a second sequence representing a sine mixing signal, wherein the step of generating the second mixed signal comprises the step of performing an exclusive-OR operation between corresponding ones of the 1-bit digital samples representing the digital intermediate frequency signal, and the second sequence representing the sine mixing signal;
using analog filtering steps to filter the first and second mixed signals to generate in-phase and quadrature signals;
and
converting the in-phase and quadrature signals into the in-phase and quadrature samples.

6 more elements

Dependencies are inferred from the claim text.

Digital reception with radio frequency sampling

Life of this patent

Digital reception with radio frequency sampling

Life of this patent

Abstract

Claims28