Multi-frequency receiver with arbitrary center frequencies
AssigneeTALX Corporation
InventorBaohua Zheng
Life of this patent
Estimating the term…
Abstract
A multi-frequency receiver for detecting the presence of one or more of a plurality of m frequency tones in an incoming signal. A digital signal processor executes a fast algorithm for accurately calculating the spectral energies in a plurality of m frequency bands. Each frequency band is centered on one of the frequencies to be detected. The center frequencies of those bands are independent of the data length used. The calculated spectral energies are compared to a set of predefined thresholds. As a result, the presence of particular tones within the incoming signal are detected.
Claims18
A multi-frequency receiver for receiving an incoming analog signal x(t) and for determining the presence of any of a plurality of m known frequencies f.sub.i, i=1, 2, . . . , m, in the incoming analog signal, said receiver comprising:
- a. a detector for detecting the incoming analog signal;
- b. an analog to digital converter for converting the detected incoming analog signal into a digital signal x(n) at a sampling frequency f.sub.S ;
- and
- c. a digital signal processor for analyzing the digital signal, said processor executing a software program implementing:
- i. means for defining a plurality of m frequency bands, each frequency band having a center frequency equal to one of the known frequencies f.sub.i to be detected;
- ii. means for calculating a spectral energy .vertline.X(f.sub.i).vertline..sup.2 within each frequency band according to the following algorithm:
- Q.sub.i (n)=2C.sub.i Q.sub.i (n-1)-Q.sub.i (n-2)+x(n)
- where C.sub.i =cos (2.pi.f.sub.i /f.sub.S), Q.sub.i (-1)=Q.sub.i (-2)=0, N is a preselected data length and n=0, 1, 2, . . . , N-1;
- and
- .vertline.X(f.sub.i).vertline..sup.2 =Q.sub.i (N-1).sup.2 +Q.sub.i (N-2).sup.2 -2C.sub.i Q.sub.i (N-1)Q.sub.i (N-2);
- and
- iii. decision logic for comparing the calculated spectral energy of each band to a predefined threshold for determining the presence of any of the m known frequencies f.sub.i in the incoming analog signal.
A receiving method for receiving an incoming analog signal x(t) and for determining the presence of any of a plurality of m known frequencies f.sub.i, i=1, 2, . . . , m, in the incoming analog signal, said receiver comprising the steps of:
- a. detecting the incoming analog signal;
- b. converting the detected incoming analog signal into a digital signal x(n) at a sampling frequency f.sub.S ;
- c. determining the spectral energy .vertline.X(f.sub.i).vertline..sup.2 of the digital signal within each of a plurality of m frequency bands, each band having a center frequency equal to one of the known frequencies f.sub.i to be detected, said determining step employing the following algorithm:
- Q.sub.i (n)=2C.sub.i Q.sub.i (n-1)-Q.sub.i (n-2)+x(n)
- where C.sub.i =cos (2.pi.f.sub.i /f.sub.S), Q.sub.i (-1)=Q.sub.i (-2)=0, N is a preselected data length and n=0, 1, 2, . . . , N-1;
- and
- .vertline.X(f.sub.i).sup.2 =Q.sub.i (N-1).sup.2 +Q.sub.i (N-2).sup.2 -2C.sub.i Q.sub.i (N-1)Q.sub.i (N-2);
- and
- d. comparing the calculated spectral energy of each band to a predefined threshold for determining the presence of any of the m known frequencies f.sub.i in the incoming analog signal.
A multi-frequency receiver for receiving an incoming analog signal x(t) and for determining the presence of any of a plurality of m known frequencies f.sub.i, i=1, 2, . . . , m, in the incoming analog signal, said receiver comprising:
- a. a detector for detecting the incoming analog signal;
- b. an analog to digital converter for converting the detected incoming analog signal into a digital signal x(n) at a sampling frequency f.sub.S ;
- and
- c. a digital signal processor for analyzing the digital signal, said processor comprising:
- i. a plurality of m frequency bands, each of which is centered at one of the known frequencies f.sub.i to be detected;
- ii. means for calculating a spectral energy .vertline.X(f.sub.i).vertline..sup.2 within each frequency band according to the following algorithm:
- Q.sub.i (n)=2C.sub.i Q.sub.i (n-1)-Q.sub.i (n-2)+x(n)
- where C.sub.i =cos (2.pi.f.sub.i /f.sub.S), Q.sub.i (-1)=Q.sub.i (-2)=0, N is a preselected data length and n=0, 1, 2, . . . , N-1;
- and
- .vertline.X(f.sub.i).vertline..sup.2 =Q.sub.i (N-1).sup.2 +Q.sub.i (N-2).sup.2 -2C.sub.i Q.sub.i (N-1)Q.sub.i (N-2);
- and
- iii. decision logic for comparing the calculated spectral energy of each band to a predefined threshold for each band and for determining the presence of any of the m known frequencies f.sub.i in the incoming analog signal.
Dependencies are inferred from the claim text.