Binary transversal filter

• US 4,323,864 A
• Filed: 03/03/1980
• Issued: 04/06/1982
• Est. Priority Date: 03/02/1979
• Status: Expired due to Term

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Fujitsu Limited, Nippon Telegraph and Telephone East Corporation (Nippon Telegraph and Telephone Corporation)
• Inventors: Suzuki, Eiji, Ogawa, Kazuo, Horikawa, Izumi, Kurita, Osamu
• Primary Examiner(s): Nussbaum, Marvin L.
• Application Number:
  US06/126,528
• Time in Patent Office: 764 Days
• Field of Search: 333/165, 333/166, 333/18, 333/28 R, 307/221 R, 307/221 C, 307/269, 328/37, 328/165, 328/167, 328/37, 375/25, 375/26, 375/34, 375/96, 375/103, 375/104, 364/724
• US Class Current: 333/165
• CPC Class Codes: H03H 17/06 Non-recursive filters

Abstract

A binary transversal filter which has a plurality of stages of shift registers that are driven by timing signals of a frequency which is a multiple of that of clock pulses being introduced, and a weighting circuit which weights outputs of shift registers of each of the stages, so that outputs of the weighting circuit can be synthesized. The characteristic feature of the present invention resides in the facts that NRZ signals are introduced into the shift registers, and the shift registers are driven by timing signals of a frequency which is a multiple of that of clock pulses of the NRZ signals.

Claims

1. A binary transversal filter for receiving NRZ input signals synchronously with clock pulses, comprising:

a shift register, to which the NRZ input signals are fed directly, said register including a plurality of stages which are driven by timing signals of a frequency that is a multiplier M times that of the clock pulses of the input signals,

a weighting circuit for weighting and synthesizing the outputs of each of the stages of said shift register, and

a tap coefficient a_n of said weighting circuit connected to each of the stages of said shift register being given by a sampling value of an interval T/M of an inverse Fourier transform a(t) of ##EQU9## wherein H(ω

) denotes a transfer coefficient which gives a response that is to be found, T denotes a repetitive period of the input NRZ signals, and M represents said multiplier.

2. A binary transversal filter as set forth in claim 1, wherein said shift register is driven by timing signals of a frequency two times that of the clock pulses of said NRZ signals, and said tap coefficient a_n of said weighting circuit connected to each of the stages of said shift register is given by a sampling value of an interval T/2 of an inverse Fourier transform a(t) of ##EQU10## where H(ω

) denotes a transfer coefficient which gives a response that is to be found, and T denotes a repetitive period of the input NRZ signals.

3. The filter of claim 1 or 2, wherein:

each said tap coefficient a_n of said weighting circuit is realized as a resistor having a value R_n such that the product of R_n and a_n is constant for the filter.

4. The filter of claim 3, further comprising:

an operational amplifier, operatively connected to all of said resistors.

5. The filter of claim 4, further comprising:

a low-pass filter operatively connected to the output of said operational amplifier.

6. A binary transversal filter for receiving an NRZ input having a clock frequency 1/T and processing said input according to a transfer characteristic H(ω

) comprising;

a multiplier circuit for detecting the clock frequency of the NRZ input and generating timing signals at a frequency which is a preselected multiple M of the clock frequency;

a shift register comprising (2n+1) sequentially connected stages, each stage being operatively connected to the timing signals generated by said multiplier circuit, and the first one of said stages being directly connected to the NRZ input; and

a plurality of resistors, respectively connected at one terminal of each thereof to a corresponding stage of said shift register and connected at the other terminal of each thereof to a common output terminal to provide an output of said filter, wherein the value R_k of the respective one of said resistors which is connected to the k-th stage of said shift register is given in relation to an arbitrary real constant C by;

##EQU11##

7. The filter of claim 6, further comprising:

a low-pass filter, operatively connected between said common connection of said resistors and the output of said binary transversal filter.