Circuits and methods for detecting interferers
Mechanisms for interferer detection can detect interferers by detecting elevated signal amplitudes in one or more of a plurality of bins (or bands) in a frequency range between a maximum frequency (f MAX ) and a minimum frequency (f MIN ). To perform rapid interferer detection, the mechanisms downconvert an input signal x(t) with a local oscillator (LO) to a complex baseband signal x I (t)+jx Q (t). x I (t) and x Q (t) are then multiplied by m unique pseudorandom noise (PN) sequences (e.g., Gold sequences) g m (t) to produce m branch signals for I and m branch signals for Q. The branch signals are then low pass filtered, converted from analog to digital form, and pairwise combined by a pairwise complex combiner. Finally, a support recovery function is used to identify interferers.
1. A circuit for detecting interferers, comprising:
a first in-phase mixer that receives and mixes a radio frequency (RF) signal and an in-phase local oscillator signal to produce a first in-phase mixer output signal;
a first quadrature-phase mixer that receives and mixes the radio frequency (RF) signal and a quadrature-phase local oscillator signal to produce a first quadrature-phase mixer output signal;
a first in-phase filter that receives and filters the first in-phase mixer output signal and produces a first in-phase filtered signal;
a first quadrature-phase filter that receives and filters the first quadrature-phase mixer output signal and produces a first quadrature-phase filtered signal;
a first in-phase branch that comprises:
a second in-phase mixer that receives and mixes the first in-phase filtered signal and a first pseudorandom noise signal to produce a second in-phase mixer output signal;
a second in-phase filter that receives and filters the second in-phase mixer output signal to produce a second in-phase filtered signal; and
a first in-phase analog-to-digital converter that receives the second in-phase filtered signal and produces a first in-phase digitized signal;
a second in-phase branch that comprises:
a third in-phase mixer that receives and mixes the first in-phase filtered signal and a second pseudorandom noise signal to produce a third in-phase mixer output signal;
a third in-phase filter that receives and filters the third in-phase mixer output signal to produce a third in-phase filtered signal; and
a second in-phase analog-to-digital converter that receives the third in-phase filtered signal and produces a second in-phase digitized signal;
a first quadrature-phase branch that comprises:
a second quadrature-phase mixer that receives and mixes the first quadrature-phase filtered signal and the first pseudorandom noise signal to produce a second quadrature-phase mixer output signal;
a second quadrature-phase filter that receives and filters the second quadrature-phase mixer output signal to produce a second quadrature-phase filtered signal; and
a first quadrature-phase analog-to-digital converter that receives the second quadrature-phase filtered signal and produces a first quadrature-phase digitized signal; and
a second quadrature-phase branch that comprises:
a third quadrature-phase mixer that receives and mixes the first quadrature-phase filtered signal and the second pseudorandom noise signal to produce a third quadrature-phase mixer output signal;
a third quadrature-phase filter that receives and filters the third quadrature-phase mixer output signal to produce a third quadrature-phase filtered signal; and
a second quadrature-phase analog-to-digital converter that receives the third quadrature-phase filtered signal and produces a second quadrature-phase digitized signal;
a complex combiner that combines the first in-phase digitized signal and the first quadrature-phase digitized signal to produce a first combined signal and that combines the second in-phase digitized signal and the second quadrature-phase digitized signal to produce a second combined signal; and
at least one hardware processor that receives the first combined signal and the second combined signal and that identifies at least one interferer in the RF signal using the first combined signal and the second combined signal using an orthogonal matching pursuit technique.
2. The circuit of claim 1 , further comprising a low noise amplifier that outputs the RF signal.
3. The circuit of claim 1 , wherein the quadrature-phase local oscillator signal is shifted 90 degrees from the in-phase local oscillator.
4. The circuit of claim 1 , wherein the first pseudorandom noise signal and the second pseudorandom noise signal are Gold sequences.
5. The circuit of claim 4 , further comprising a Gold sequence generator.
6. The circuit of claim 1 , wherein the at least one hardware processor also determines an estimate of an input signal represented by the RF signal using the first combined signal and the second combined signal.
7. The circuit of claim 1 , wherein the complex combiner: combines the first in-phase digitized signal (X Base-Band-in-Phase1 ) and the first quadrature-phase digitized signal (X Base-Band-Quadrature1 ) to produce the first combined signal (y 1 ), wherein y 1 =X Base-Band-In-Phase1 ∓jX Base-Band-Quadrature1 ; and that combines the second in-phase digitized signal (X Base-Band-In-Phase2 ) and the second quadrature-phase digitized signal (X Base-Band-Quadrature2 ) to produce a second combined signal (y 2 ), wherein y 2 =X Base-Band-In-Phase2 ∓jX Base-Band-Quadrature2 .
8. A method for detecting interferers, comprising:
mixing a radio frequency (RF) signal and an in-phase local oscillator signal to produce a first in-phase mixer output signal;
mixing the radio frequency (RF) signal and a quadrature-phase local oscillator signal to produce a first quadrature-phase mixer output signal;
filtering the first in-phase mixer output signal to produce a first in-phase filtered signal;
filtering the first quadrature-phase mixer output signal to produce a first quadrature-phase filtered signal;
mixing the first in-phase filtered signal and a first pseudorandom noise signal to produce a second in-phase mixer output signal;
filtering the second in-phase mixer output signal to produce a second in-phase filtered signal;
analog-to-digital converting the second in-phase filtered signal to produce a first in-phase digitized signal;
mixing the first in-phase filtered signal and a second pseudorandom noise signal to produce a third in-phase mixer output signal;
filtering the third in-phase mixer output signal to produce a third in-phase filtered signal;
analog-to-digital converting the third in-phase filtered signal to produce a second in-phase digitized signal;
mixing the first quadrature-phase filtered signal and the first pseudorandom noise signal to produce a second quadrature-phase mixer output signal;
filtering the second quadrature-phase mixer output signal to produce a second quadrature-phase filtered signal;
analog-to-digital converting the second quadrature-phase filtered signal to produce a first quadrature-phase digitized signal;
mixing the first quadrature-phase filtered signal and the second pseudorandom noise signal to produce a third quadrature-phase mixer output signal;
filtering the third quadrature-phase mixer output signal to produce a third quadrature-phase filtered signal;
analog-to-digital converting the third quadrature-phase filtered signal to produce a second quadrature-phase digitized signal;
combining the first in-phase digitized signal and the first quadrature-phase digitized signal to produce a first combined signal and combining the second in-phase digitized signal and the second quadrature-phase digitized signal to produce a second combined signal; and
identifying at least one interferer in the RF signal using the first combined signal and the second combined signal using an orthogonal matching pursuit technique.
9. The method of claim 8 , further comprising amplifying an input signal to produce the RF signal using a low noise amplifier.
10. The method of claim 8 , wherein the quadrature-phase local oscillator signal is shifted 90 degrees from the in-phase local oscillator.
11. The method of claim 8 , wherein the first pseudorandom noise signal and the second pseudorandom noise signal are Gold sequences.
12. The method of claim 11 , further comprising generating the Gold sequences using a Gold sequence generator.
13. The method of claim 8 , further comprising determining an estimate of an input signal represented by the RF signal using the first combined signal and the second combined signal.
14. The method of claim 8 , wherein: combining the first in-phase digitized signal (X Base-Band-In-Phase1 ) and the first quadrature-phase digitized signal (X Base-Band-Quadrature1 ) to produce the first combined signal (y 1 ), wherein y 1 =X Base-Band-In-Phase1 ∓jX Base-Band-Quadrature1 ; and combining the second in-phase digitized signal (X Base-Band-In-Phase2 ) and the second quadrature-phase digitized signal (X Base-Band-Quadrature2 ) to produce a second combined signal (y 2 ), wherein y 2 =X Base-Band-In-Phase2 ∓jX Base-Band-Quadrature2 .