Patent ID: 7061975
Filing Date: 2006-06-13
Classification: G11C,H04B

Abstract:
1. A nonrecursive digital filter, comprising: an n-stage shift register that sequentially shifts input data having a predetermined number n of bits, and in which the output of each output stage of the shift register is multiplied by a filter coefficient and added, the n-stage shift register including: first and second shift registers to which the input data is input and a shift clock is inputted, each having n/2 stages obtained by dividing the n-stage shift register; a reference-code register that stores n reference codes; first and second selection devices that select and output odd-numbered stages and even-numbered stages of the reference-code register according to the shift clock; a first multiplication device that multiplies an output of each stage of the first shift register by the output of the first selection device; a second multiplication device that multiplies an output of each stage of the second shift register by the output of the second selection device; and a correlation-strength calculation device that adds multiplication results of the first multiplication device and the second multiplication device to output a correlation strength; wherein the first and second shift registers are configured such that one of the first and second shift registers performs a shift operation at a rising edge of the shift clock and the other performs a shift operation at a falling edge of the shift clock; and wherein the first and second selection devices are configured such that, when the shift clock is in an ON state, one of the first and second selection devices outputs even-numbered stages of the reference-code register to the first multiplication device and the other of the first and second selection devices outputs odd-numbered stages to the second multiplication device, and when the shift clock is in an OFF state, the one of the first and second selection devices outputs the odd-numbered stages of the reference-code register to the first multiplication device and the other of the first and second selection devices outputs the even-numbered stages to the second multiplication device.