Up-sampling half-band reconstruction filtering
View Patent ↗An up-sampled half band reconstruction filter has a seagull architecture in the form of a pair of parallel infinite impulse response (IIR) filters, one receiving as an input an input signal delayed by one sample time and the other receiving as an input a reverse version of the input signal delayed by one sample time. The outputs from the pair of parallel IIR filters are combined with the input signal to produce a reconstruction filter output in response to the input signal.
1. A reconstruction filter having a seagull architecture comprising:
a first infinite impulse response filter having as an input a signal delayed by one sample time and having as an output a first filter output;
a second infinite impulse response filter having as an input a reverse version of the signal delayed by one sample time and having as an output a second filter output; and
means for combining the first and second filter outputs and the signal to produce a reconstruction filter output.
2. The reconstruction filter as recited in claim 1 wherein each infinite impulse response filter comprises:
a high frequency path coupled to the filter input to produce a high frequency filter output; and
a low frequency path coupled to the filter input to produce a low frequency filter output, the low and high frequency filter outputs together forming the filter output for input to the combining means.
3. The reconstruction filter as recited in claim 2 wherein each frequency path comprises:
a first multiplier having a first input coupled to the filter input and a second input coupled to receive a first filter coefficient, and having an output;
a summer having a first input coupled to the output of the first multiplier and a second input, and having an output;
a delay circuit having an input coupled to the output of the summer, and having a first output coupled to the combining means and a second output; and
a second multiplier having a first input coupled to the second output of the delay circuit and a second input coupled to receive a second filter coefficient, and having an output coupled to the second input of the summer.
4. A method of reconstruction filtering an input signal comprising the steps of:
infinite impulse response filtering the input signal delayed by one sample time to produce a first filter output;
infinite impulse response filtering a reverse version of the input signal delayed by one sample time to produce a second filter output; and
combining the first and second filter outputs and the input signal to produce a reconstruction filter output in response to the input signal.