Sampling frequency converter

• US 4,472,785 A
• Filed: 10/13/1981
• Issued: 09/18/1984
• Est. Priority Date: 10/13/1980
• Status: Expired due to Term

• Current Assignee: Victor Company of Japan Limited (JVC Kenwood Corporation)
• Original Assignee: Victor Company of Japan Limited (JVC Kenwood Corporation)
• Inventors: Kasuga, Masao
• Primary Examiner(s): Shaw, Gareth D.
• Assistant Examiner(s): Wiens, Tim A.
• Application Number:
  US06/311,095
• Time in Patent Office: 1,071 Days
• Field of Search: 364/718, 364/723, 364/724, 364/328
• US Class Current: 708/270
• CPC Class Codes: H03H 17/0288 Recursive, non-recursive, ladder, lattice structures
• CPC Class Codes: H03H 17/0685 the ratio being rational

Abstract

A sampling frequency converter for converting a first signal sampled at a first sampling frequency f1 into a second signal sampled at a second sampling frequency f2 comprising an interpolation device supplied with the first signal, for inserting L-1 zeros (L is an integer) for every sampling time, a filter circuit for attenuating a frequency component over a frequency f/2 (f is a frequency) within an output signal of said interpolation device, where the filter circuit has a series circuit consisting of a finite impulse response digital filter and an infinite impulse response digital filter, and the frequency f is equal to the first sampling frequency f1 when f1<f2 and equal to the second sampling frequency f2 when f1>f2, and a decimation device for extracting every M-th (M is an integer) output signal of the filter circuit, to produce said second signal.

Claims

1. A sampling frequency converter for converting a first signal sampled at a first sampling frequency f1 into a second signal sampled at a second sampling frequency f2, said second sampling frequency f2 being equal to L/M times said first sampling frequency f1, where L and M are natural numbers satisfying L≠

M, said sampling frequency converter comprising;

an interpolation device supplied with said first signal as an input signal thereof, for inserting L-1 zeros for every sampling time;

a filter circuit supplied with an output signal of said interpolation device as an input signal thereof, for attenuating a frequency component over a frequency f/2 within an output signal of said interpolation device, where f is a frequency, said filter circuit comprising a series circuit which includes a finite impulse response digital filter and an infinite impulse response digital filter which is coupled in series to an output stage of said finite impulse response digital filter, said frequency f being equal to said first sampling frequency f1 under a condition f1<

f2 and being equal to said second sampling frequency f₂ under a condition f1>

f2; and

a decimation device supplied with an output signal of said filter circuit as an input signal thereof, for extracting sampled values in the output signal of said filter circuit at a rate of one sampled value for every M sampled values in the output signal of said filter circuit, to produce said second signal.

2. A sampling frequency converter as claimed in claim 1 in which said infinite impulse response digital filter is a digital filter described by a transfer function ##EQU12## satisfying an equation f1L=Mf2=i_p Kf2 (or i_p k=M) where K is a natural number, i_p is a prime number, and a₀, a₁, a₂, b₁, and b₂ are coefficients.

3. A sampling frequency converter as claimed in claim 1 in which said filter circuit comprises a plurality of finite impulse response digital filters and a plurality of infinite impulse response digital filters which are coupled in series.

4. A sampling frequency converter as claimed in claim 1 in which the order of said infinite impulse response digital filter within said filter circuit is selected to four or six according to the value of M.

5. A sampling frequency converter as claimed in claim 1 in which said infinite impulse response digital filter has an amplitude characteristic in which an upper limit frequency of a passband thereof is in a vicinity of a roll-off frequency due to resonance, and has a phase characteristic which is substantially linear in the passband thereof, and said finite impulse response digital filter has an amplitude characteristic for cancelling a peak which is in the vicinity of the roll-off frequency in the amplitude characteristic of said infinite impulse response digital filter.