Decimation filtering apparatus and method

A decimation filtering apparatus for decimating a sampling signal of a digital signal processing system, comprising:

• a CIC decimation filter for decimation filtering the sampling signal to downconvert the sampling signal;
• an ISOP filter for monotonically increasing an output of the CIC decimation filter to compensate for a passband droop caused by the CIC decimation filter;
• and
• a modified halfband filter for half-decimating a signal output from the ISOP filter, with passband droop thereof compensated for by the ISOP filter.

A decimation filtering apparatus for decimating a sampling signal of a digital signal processing system, comprising:

• a Cascaded Integrator-Comb (CIC) decimation filter for decimation filtering the sampling signal to downconvert the sampling signal;
• an Interpolated Second Order Polynomial (ISOP) filter for monotonically increasing an output of the CIC decimation filter to compensate for a passband droop caused by the CIC decimation filter;
• a multistage halfband filter including at least one modified halfband filter for ½ decimating a signal output from the ISOP filter, said multistage halfband filter decimating the signal output from the ISOP filter to downconvert the signal;
• and
• a programmable Finite Impulse Response (FIR) filter for compensating for a passband droop of a signal output from the multistage halfband filter.

A decimation filtering apparatus for decimating a sampling signal of a digital signal processing system, comprising:

• a Cascaded Integrator-Comb (CIC) decimation filter for decimation filtering the sampling signal to downconvert the sampling signal;
• an Interpolated Second Order Polynomial (ISOP) filter for monotonically increasing an output of the CIC decimation filter to compensate for a passband droop caused by the CIC decimation filter;
• a multistage halfband filter including at least one modified halfband filter for ½ decimating a signal output from the ISOP filter, said multistage halfband filter decimating the signal output from the ISOP filter to downconvert the signal;
• a programmable FIR filter for compensating for a passband droop of a signal output from the multistage halfband filter;
• and
• an interpolation filter for adjusting an output sampling rate of the programmable FIR filter to a predetermined frequency.

A decimation filtering apparatus in a downconverter of a software radio system, comprising:

• a first mixer for mixing a digital converted Intermediate Frequency (IF) signal with a sinusoidal signal output from a sinusoidal wave generator to generate an I channel sampling signal;
• a first decimation filter for decimating an output of the first mixer to downconvert the output of the first mixer;
• a second mixer for mixing an IF sampling signal with an output of the sinusoidal wave generator to generate a Q channel sampling signal;
• a second decimation filter for decimating an output of the second mixer to downconvert the output of the second mixer;
• and
• a signal processor for processing outputs of the first and second decimation filters at baseband;
• wherein each of said first and second decimation filters comprises:
• a CIC decimation filter for decimation filtering the sampling signal to downconvert the sampling signal;
• an ISOP filter for monotonically increasing an output of the CIC decimation filter to compensate for a passband droop caused by the CIC decimation filter;
• a multistage halfband filter including at least one modified halfband filter for half-decimating a signal output by the ISOP filter, said multistage halfband filter decimating the signal output by the ISOP filter to downconvert the signal;
• and
• a programmable FIR filter for compensating for a passband droop of a signal output by the multistage halfband filter.

A decimation filtering method comprising:

• a CIC decimation filtering step of decimating a sampling signal by H ⁡ ( z ) = ( 1 MR ⁢ ⁢ 1 - z - MR 1 - z - 1 ) L
• to downconvert the sampling signal;
• an ISOP filtering step of monotonically increasing the CIC decimation filtered signal by P ⁡ ( z ) = 1 [LeftBracketingBar] c + 2 [RightBracketingBar] ⁢ ⁢ ( 1 + cz - I + z - 2 ⁢ I )
• to compensate for a passband droop caused by decimation;
• a multistage halfband filtering step of performing multiple halfband filtering operations of ½ decimating the input signal, to downconvert the ISOP filtered signal;
• and
• an FIR filtering step of compensating for a passband droop of the multistage halfband filtered signal.

A decimation filtering method comprising:

• a CIC decimation filtering step of decimating a sampling signal by H ⁡ ( z ) = ( 1 MR ⁢ ⁢ 1 - z - MR 1 - z - 1 ) L
• to downconvert the sampling signal;
• an ISOP filtering step of monotonically increasing the CIC decimation filtered signal by P ⁡ ( z ) = 1 [LeftBracketingBar] c + 2 [RightBracketingBar] ⁢ ⁢ ( 1 + cz - I + z - 2 ⁢ I )
• to compensate for a passband droop caused by decimation;
• a multistage halfband filtering step of performing multiple halfband filtering operations of ½ decimating the input signal, to downconvert the ISOP filtered signal;
• an FIR filtering step of compensating for a passband droop of the multistage halfband filtered signal;
• and
• an interpolation filtering step of adjusting the FIR filtered signal to a predetermined frequency.