Superimposed composite channel filter
View Patent ↗Methods and systems are provided to generate digital coefficients for a filter. The generation of coefficients relies on a Fourier transformation of an impulse response in time domain that is zero padded, e.g., zeros are appended to an array corresponding to a sampled input signal of length M. A unit prototypical filter is generated through a frequency domain response of length N FFT =N S +M−1, wherein N S is a sampling length of the incoming signal. The unit prototypical filter is then circularly shifted in order to generate a band pass filter centered at a desired frequency. Circularly shifted filters are point-to-point added to generate a set of composite digital coefficients to filter the incoming signal. The reference frequencies for the composite filter are extracted from a message received from one or more base stations associated with one or more service providers. The composite filter typically operates on a frequency repeater.
1. A method for generating digital filter coefficients utilized in a wireless environment, the method comprising:
appending zeros to an M-sample impulse response in time domain to create a zero padded impulse response of N FFT in length, wherein M and N FFT are positive integers;
Fourier transforming the NFFT length zero-padded impulse response; performing a circular shift of the Fourier-transformed zero-padded impulse response; and
adding in frequency domain a set of circularly-shifted, Fourier-transformed zero-padded impulse responses to generate a set of composite digital filter coefficients.
2. The method of claim 1 , further comprising:
adding in frequency domain a set of circularly-shifted, Fourier-transformed zero-padded impulse responses to generate composite digital filter coefficients; and
performing an inverse Fourier transform of the frequency domain composite digital filter coefficients to obtain a composite time domain digital filter impulse response.
3. The method of claim 1 , further comprising conveying the generated filter coefficients to a frequency bin multiplier block.
4. The method of claim 3 , further comprising applying the generated digital filter coefficients to a set of frequency domain bins of a block of signal to be repeated.
5. The method of claim 4 , generating a set of frequency domain bins of a block of signal by appending N S time domain signal samples with zeros to form a N FFT block of zero padded time samples, wherein N S and N FFT are a positive integers;
and, performing a Fourier transform of the zero padded time sample to produce a set of frequency domain bins.
6. The method of claim 5 , wherein N FFT is equal to or greater than M+N S −1.
7. The method of claim 4 , wherein the generated composite digital filter coefficients are designed to filter a predetermined set of frequencies to be repeated.
8. The method of claim 7 , wherein in the M-sample impulse response is designed to match at least one industry standardized waveform property.
9. The method of claim 8 , the set of frequencies to be repeated comprising a set of sub-bands within an operating band of a service provider.
10. The method of claim 8 , the set of frequencies to be repeated comprising a set of predetermined frequencies associated with the service provider.
11. The method of claim 10 , the message is at least one of a broadcast channel or a management frame, or a directed message, or an short message service message.
12. The method of claim 7 , wherein the set of frequencies to be repeated is determined by carrying out the following acts:
receiving a message carrying an indication of the set of frequencies;
extracting the set of frequencies from the indication within the message.
13. The method of claim 12 , the cell search is conducted by a modem residing in a repeater.
14. The method of claim 13 , wherein the predetermined set of frequencies is stored in the frequency repeater.
15. The method of claim 7 , the set of frequencies to be repeated is acquired in a cell search of the cellular signals.
16. The method of claim 3 , further comprising storing the generated filter mask in a repeater.
17. The method of claim 1 , further comprising generating the M-bin impulse response in time domain.
18. A wireless device comprising:
a processor configured to generate an M sample impulse response in time domain, to perform an array padding operation, wherein M is a positive integer; to compute a Fourier transformation of at least one of the M-bin impulse response or an N FFT -bin frequency sequence, wherein N FFT is a positive integer; perform a circular shift of an N FFT -bin Fourier transformed impulse response; to add a set of Fourier transformed zero-padded impulse responses; to generate a composite mask filter utilizing the added Fourier-transformed impulse responses; and
a memory coupled to the processor.
19. The device of claim 18 , the processor further configured to convey the generated filter mask to a frequency bin multiplier block.
20. The device of claim 19 , the processor further configured to apply the generated filter mask to a set of frequency domain bins of a block of signal to be repeated.
21. The device of claim 20 , the block of signal to be repeated comprises a set of sub-bands within an operating band of a service provider.
22. The device of claim 21 , the set of sub-bands comprising a set of predetermined frequencies associated with the service provider.
23. The device of claim 21 , wherein the set of sub-bands is determined by carrying out the following acts:
receiving a message carrying an indication of the set of frequencies;
extracting the set of frequencies from the indication within the message.
24. The device of claim 18 , the processor further configured to store the generated composite set of filter coefficients.
25. An apparatus that operates in a wireless environment, the apparatus comprising:
means for zero padding an M-bin impulse response in time domain to an N FFT -bin length, wherein M and N FFT are positive integers;
means for Fourier transforming the N FFT -bin zero-padded impulse response;
performing a circular shift of the Fourier-transformed zero-padded impulse response;
means for adding in frequency domain a set of circularly-shifted, Fourier-transformed zero-padded impulse responses to generate a filter mask;
means for conveying the generated filter mask to a frequency bin multiplier block; and
means for applying the generated filter mask to a set of frequency domain bins of a block of signal to be repeated.
26. A computer-readable storage medium, volatile or non-volatile, encoded with a computer program, the computer program including:
code for causing a computer to pad an M-bin impulse response in time domain to an N FFT -bin length, wherein M and N FFT are positive integers;
code for causing a computer to Fourier transform the N FFT -bin zero-padded impulse response;
code for causing a computer to perform a circular shift of the Fourier-transformed zero-padded impulse response; and
code for causing a computer to add in frequency domain a set of circularly-shifted, Fourier-transformed zero-padded impulse responses to generate a filter mask; and
code for causing a computer to apply the generated filter mask to a set of frequency domain bins of a block of signal to be repeated.