US 8,275,341 B2Granted

Fixed point FIR filter with adaptive truncation and clipping and wireless mobile station using same

AssigneeNational Semiconductor Corporation

InventorTao Zhang

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Abstract

A fixed point finite impulse response (FIR) filter comprising: 1) an input stage for receiving an input signal as a sequence of input samples comprising: i) delay elements connected in series for receiving and shifting N sequential input samples; ii) multipliers, each multiplier receiving a selected one of the N sequential input samples from the delay elements and multiplying the selected input sample by a corresponding coefficient to produce an intermediate product; and iii) a summer for receiving and adding N intermediate products from the multipliers to produce an output sum signal comprising a sequence of output sum samples; and 2) an output stage for truncating k least significant bits (LSBs) from each of the output sum samples, wherein k is a variable number.

Claims20

Dependent claims

A fixed point finite impulse response (FIR) filter comprising:

a filter input stage configured to receive an input signal as a sequence of input samples and to generate an intermediate signal comprising a sequence of filtered samples, wherein the filtered samples have a larger number of bits than the input samples;
and
an output stage configured to truncate k least significant bits from each of the filtered samples to generate a sequence of output samples, wherein the output stage is configured to perform adaptive truncation where a value of k is modified in order to truncate a variable number of least significant bits from the filtered samples during operation of the fixed point FIR filter;
wherein the output stage comprises:
a feedback controller configured to determine a power of each output sample and, in response to the determination, adjust the value of k;
and
a variable truncation unit configured to truncate the k least significant bits from each of the filtered samples to thereby generate a sequence of truncated samples.

4 more elements

A wireless communication device comprising:

1) a radio frequency (RF) receiver front-end configured to receive an incoming RF signal and down-convert the incoming RF signal to a demodulated signal;
and 2) a fixed point finite impulse response (FIR) filter configured to receive the demodulated signal as a sequence of input samples, the fixed point FIR filter comprising:
a filter input stage configured to receive the input samples and to generate an intermediate signal comprising a sequence of filtered samples, wherein the filtered samples have a larger number of bits than the input samples;
and
an output stage configured to truncate k least significant bits from each of the filtered samples to generate a sequence of output samples, wherein the output stage is configured to perform adaptive truncation where a value of k is modified in order to truncate a variable number of least significant bits from the filtered samples during operation of the fixed point FIR filter;
wherein the output stage comprises:
a feedback controller configured to determine a power of each output sample and, in response to the determination, adjust the value of k;
and
a variable truncation unit configured to truncate the k least significant bits from each of the filtered samples to thereby generate a sequence of truncated samples.

6 more elements

Dependencies are inferred from the claim text.