Optimized filter parameters design for digital IF programmable downconverter

1. A method for finding an optimized filter parameters design for a digital IF programmable downconverter, comprises the following steps:

(1) receiving an input specification, said input specification comprising an input signal sampling rate, an input data rate, an oversampling factor R, an available number of Halfband decimation filters, a passband frequency, a stopband frequency, a passband ripple, a stopband attenuation and a optimal filter parameter satisfying said input specification;

(2) determining if said oversampling factor R is equal to 1;

(3) obtaining an largest available number nHB of Halfband decimation filters and setting an initial value of nHB equal to a total of Halfband decimation filters;

(4) obtaining an largest available first number of Halfband decimation filters satisfying said input specification and determining if re-sampling FIR filter is necessary;

(5) obtaining an optimized combination of Halfband decimation filters satisfying said input specification;

(6) obtaining a total n of window function for designing filters;

(7) obtaining a window function index j and setting said windows function index to 1; and

(8) obtaining a programmable FIR filter satisfying said input specification.

2. The method of claim 1 , wherein the step (4) further comprises the following steps:

A: estimating a decimation factor M based on said largest available number nHB of Halfband decimation filters and obtaining a minimum decimation factor M CIC,min of CIC decimation filter;

B: determining if said minimum decimation factor M CIC,min of CIC decimation filter is equal to said decimation factor M; and

C: obtaining a decimation factor threshold M V of CIC decimation filter and determining if said minimum decimation factor M CIC,min of CIC decimation filter is larger or equal to said decimation factor threshold M V of CIC decimation filter.

3. The method of claim 2 , wherein in step C if M CIC,min is less than M V , subtracting 1 from said largest available number nHB of Halfband decimation filters and determining if said nHB is larger or equal to O.

4. The method of claim 2 , wherein said decimation factor M obtained from said largest available number nHB of Halfband decimation filters is further obtained by dividing said input signal sampling rate by twice said input data rate, then divided by a decimation factor M nHB of Halfband decimation filter having said largest available number nHB, wherein MnHB=2 nHB .

5. The method of claim 2 , wherein said minimum decimation factor M CIC,min of CIC decimation filter is less than or equal to a positive integer of said decimation factor M obtained from said largest available number nHB of Halfband decimation filter.

6. The method of claim 1 , wherein the step (5) further comprises the following steps:

A: estimating a decimation factor M 1 based on a combination number nHB,i of Halfband decimation filters having a priority index i and obtaining a decimation factor M CIC of CIC decimation filter;

B: obtaining a combination threshold M ORF of Halfband decimation filters having said priority index i; and

C: determining if said decimation factor M CIC of CIC decimation filter is larger or equal to said combination threshold M ORF of Halfband decimation filters having said priority index i.

7. The method of claim 6 , wherein if step C is true, then determining if said decimation factor M CIC of CIC decimation filter is equal to said decimation factor M 1 .

8. The method of claim 6 , wherein said decimation factor M 1 obtained from said combination number nHB,i of Halfband decimation filters having a priority index I is further obtained from dividing said input signal sampling rate by twice said input data rate, then divided by said decimation factor M nHB,i of Halfband decimation filter having said combination number nHB,i of Halfband decimation filters and said priority index i, wherein M nHB,i =2 nHB,i .

9. The method of claim 6 , wherein said decimation factor M CIC is less than or equal to a largest positive integer of said decimation factor M 1 obtained from said combination number nHB,i of Halfband decimation filter having said priority index i.

10. The method of claim 1 , wherein the step (8) generating a coefficient of said programmable FIR filter based on said window function of window function index j and determining if a synthesized frequency response of said digital IF programmable down-converter satisfying said input specification.

11. The method of claim 10 , wherein if said synthesized frequency response is not satisfying said input specification, add 1 to said window function index j and determine if said window function index j is greater than said total n of window function.

12. A method for finding an optimized filter parameters design for a digital IF programmable downconverter, comprises the following steps:

(1) receiving an input specification, said input specification comprising an input signal sampling rate, an input data rate, an oversampling factor R, an available number of Halfband decimation filters, a passband frequency, a stopband frequency, a passband ripple, a stopband attenuation and a optimal filter parameter satisfying said input specification;

(2) determining if said oversampling factor R is equal to 1;

(3) obtaining an largest available number nHB of Halfband decimation filters and setting an initial value of nHB equal to a total of Halfband decimation filters;

(4) obtaining an largest available first number of Halfband decimation filters satisfying said input specification and determining if re-sampling FIR filter is necessary;

(5) obtaining an optimized combination of Halfband decimation filters satisfying said input specification;

(6) obtaining a total n of window function for designing filters;

(7) obtaining a window function index j and setting said windows function index to 1; and

(8) obtaining a programmable FIR filter satisfying said input specification; wherein the step (4) further comprises the following steps:

A: estimating a decimation factor M based on said largest available number nHB of Halfband decimation filters and obtaining a minimum decimation factor M CIC,min of CIC decimation filter;

B: determining if said minimum decimation factor M CIC,min of CIC decimation filter is equal to said decimation factor M; and

C: obtaining a decimation factor threshold M V of CIC decimation filter and determining if said minimum decimation factor M CIC,min of CIC decimation filter is larger or equal to said decimation factor threshold M V of CIC decimation filter; wherein the obtaining said decimation factor threshold M V of CIC decimation filter step further comprises the following steps:

(1) obtaining a total clock cycle CLK R of re-sampling FIR filters and Halfband interpolation filters based on an existing index q and a oversampling factor R, wherein

COK R =CLK res ×q+N L

(2) obtaining a threshold CLK TH of re-sampling FIR filters and Halfband interpolation filters by dividing said total clock cycle CLK R of re-sampling FIR filters and Halfband interpolation filters by said decimation factor M nHB of Halfband decimation filter having said largest available number nHB;

(3) estimating a minimum clock cycle CLK nHB,min of all combinations of Halfband decimation filter having said largest available number nHB by:

CLKnHB

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(4) obtaining said decimation factor threshold M V of CIC decimation filter by determining a maximum between said threshold CLK TH of re-sampling FIR filters and Halfhand interpolation filters and said minimum clock cycle CLK nHB,min of all combinations of Halfband decimation filter having said largest available number nHB.

13. A method for finding an optimized filter parameters design for a digital IF programmable downconverter, comprises the following steps:

(1) receiving an input specification, said input specification comprising an input signal sampling rate, an input data rate, an oversampling factor R, an available number of Halfband decimation filters, a passband frequency, a stopband frequency, a passband ripple, a stopband attenuation and a optimal filter parameter satisfying said input specification;

(2) determining if said oversampling factor R is equal to 1;

(3) obtaining an largest available number nHB of Halfband decimation filters and setting an initial value of nHB equal to a total of Halfband decimation filters;

(4) obtaining an largest available first number of Halfband decimation filters satisfying said input specification and determining if re-sampling FIR filter is necessary;

(5) obtaining an optimized combination of Halfband decimation filters satisfying said input specification;

(6) obtaining a total n of window function for designing filters;

(7) obtaining a window function index j and setting said windows function index to 1; and

(8) obtaining a programmable FIR filter satisfying said input specification; wherein the step (5) further comprises the following steps:

A: estimating a decimation factor M 1 based on a combination number nHB,i of Halfband decimation filters having a priority index i and obtaining a decimation factor M CIC of CIC decimation filter;

B: obtaining a combination threshold M ORF of Halfband decimation filters having said priority index i; and

C: determining if said decimation factor M CIC of CIC decimation filter is larger or equal to said combination threshold M ORF of Halfband decimation filters having said priority index i; wherein said combination threshold M ORF of Halfband decimation filters having said priority index i is an overclock rate factor of said combinations of Halfband decimation filters having priority index i, said M ORF is obtained by:

M

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