摘要:
Method and apparatus for cancelling a deviation in an input signal due to drift, line or background noise, changes in circuit component characteristics due to aging, and the like wherein the input signal, typically a digitized representation of an analog signal, is altered by a presumed offset magnitude; the polarity of the difference is monitored and a negative or positive count of clock pulses is accumulated dependent upon the aforesaid polarity. When a determined positive (or negative) count is reached the presumed offset is adjusted (up or down) by a predetermined increment and the count is begun anew. As an alternative technique and embodiment the initiation of the count may be restrained as long as the magnitude of the digitized input signal exceeds a predetermined threshold.
摘要:
A compandor converts a linear code signal consisting of a polarity bit and a plurality of absolute value bits. The polarity bit represents the polarity of each sample value of an original analog signal. The absolute value bits represent the absolute value of the sample. The compandor converts the linear code into a nonlinear code including the polarity bit, a plurality of segment bits representing the segments in a characteristic curve to which the original analog signal belongs, and mantissa bits which indicate the position of the sample value in that segment. The compandor comprises: a plurality of input terminals for receiving the linear code signal; a first read-only memory means, addressed by a first bit group among the absolute value bits for memorizing a segment bit decision rule; a second read-only memory means, addressed by a second bit group consisting of another plurality of bits among the absolute value bits and some bits in common with the first bit group for memorizing a first mantissa bit decision rule; a third read-only memory means, addressed by the first bit group, for memorizing a second mantissa bit decision rule; and means for selecting the second or third read-only memory means depending on the value of the most significant bit among the segment bits applied from the first read-only memory means.
摘要:
An internal frame signal producing circuit for use in a cross connection system which cross connects first bit rate signals, each produced by multiplexing m second bit rate signals at first or the second bit rate signal levels, the first bit rate being higher than the second bit rate, an internal frame frequency is predetermined to be equal to a frequency f.sub.h ' higher than a first nominal frequency f.sub.h of the first bit rate digital signals by a predetermined value, the frequency f.sub.h ' being synchronized with a second nominal frequency fl of the second bit rate digital signals. In order to obtain the internal frame signal, from m second bit rate signals, the m second bit rate signals are stuff-synchronized processed to produce m stuff-synchronized signals, each having a stuff bit, a variable bit, and vacant bit at suitable bit intervals in a frame of a frame length. The m stuffed-synchronized signals are serially arranged to make the internal frame signal. In order to compensate a frequency difference between f.sub.h ' and fl, one frame consisting of all vacant bits is assigned at predetermined frame intervals.
摘要:
An adaptive differential pulse code modulated (ADPCM) transmission system includes a subtractor for providing a difference signal E.sub.j between an input signal X.sub.j and a predicted signal X.sub.j. A coder encodes the difference signal E.sub.j into a coded signal U.sub.j for transmission to a receiver. The signal U.sub.j is also decoded at the transmitter to produce a reproduced error signal E.sub.j. A prediction circuit operates to generate a prediction signal X.sub.j on the basis of the reproduced error signal E.sub.j. The prediction circuit is controlled by a control circuit which operates to detect transmitter instability. A first level detector in the control circuit compares the input signal level against the level of a transmitter produced signal representing the input signal. A second level detector of the control circuit determines when the input signal is below a specified value. Transmitter instability is judged by a decision circuit which determines when the output of the first level detector exceeds a preset value and the output of the second level detector is below another preset value.
摘要:
A PCM signal interface apparatus comprises a buffer memory being capable of asynchronously writing and reading a PCM signal, means for inserting a frame marker to the PCM signal upon writing the PCM signal into the buffer memory, means for judging whether or not the frame marker is contained in an output signal read out of the buffer memory at a time that is designated by an external read frame position designating pulse, means for resetting all the contents in the buffer memory and temporarily stopping the supply of a writing clock and a reading clock to the buffer memory when the frame marker is not delivered out at the predetermined time, means for resuming the supply of the writing clock to the buffer memory by receiving a write frame position designating pulse, and means for resuming the supply of the reading clock to the buffer memory by receiving the frame position designating pulse at a predetermined time lapse after the resumption of the writing clock supply. The data written into the buffer memory can be read out at a desired frame phase and data speed without duplication and missing of the read data.
摘要:
A PCM-TASI signal transmission system utilizes assignment control means responsive to an output signal from means for detecting the presence of information on each of a plurality (m) of input trunks arranged in time-serial fashion. The assignment control means selectively assigns a PCM signal representing the input trunk signal, during the period when information is present thereon, to one of a second plurality (s) of transmission channels (s
摘要:
In a cross-connection network, a plurality of asynchronous input digital signals can be cross-connected to a plurality of output lines by use of time switch. The input digital signals are pulse stuffed at a common higher bit rate and are synchronized to one another by attaching extra bits. The pulse stuffed signals are assigned into serial frames in a predetermined order by the multiplex technique and are interchanged from one to another by the time switch in the time division fashion. The frame-interchanged signal is demultiplexed to reproduce the pulse-stuffed signals which are sent out to the respective output lines assigned to the frames after removing extra bits. When the input digital signals are of higher order group, each of the higher order group digital signals is demultiplexed to lower order group signals which are pulse stuffed to be synchronized to the common higher bit rate. The pulse stuffed lower order signals are rearranged by the multiplex technique to reform each of the high order group signal which is synchronized to one another. The reformed higher order group signals are assigned in serial frames and are processed in the similar manner as described above. The frame-interchanged signals are reversely processed to be separated, demultiplexed, destuffed, and multiplexed to reproduce the input signals as the output signals.
摘要:
A compandor converts a linear code signal consisting of a polarity bit and a plurality of absolute value bits. The polarity bit represents the polarity of each sample value of an original analog signal. The absolute value bits represent the absolute value of the sample. The compandor converts the linear code into a nonlinear code including the polarity bit, a plurality of segment bits representing the segments in a characteristic curve to which the original analog signal belongs, and mantissa bits which indicate the position of the sample value in that segment. The compandor comprises: a plurality of input terminals for receiving the linear code signal; a first read-only memory means, addressed by a first bit group among the absolute value bits for memorizing a segment bit decision rule; a second read-only memory means, addressed by a second bit group consisting of another plurality of bits among the absolute value bits and some bits in common with the first bit group for memorizing a first mantissa bit decision rule; a third read-only memory means, addressed by the first bit group, for memorizing a second mantissa bit decision rule; and means for selecting the second or third read-only memory means depending on the value of the most significant bit among the segment bits supplied from the first read-only memory means.
摘要:
An N-point DFT (discrete Fourier transform) calculator comprises a pre-processor responsive to N-point complex input data F.sub.k (k=0 to N-1) for producing N/2-point complex intermediate data G.sub.p (p=0 to N/2-1) and an N/2-point DFT calculating circuit supplied with the intermediate data as N/2-point complex input data for producing in a known manner real and imaginary parts g.sub.q.sup.R and g.sub.q.sup.I of DFT's or IDFT's (inverse DFT) g.sub.q (q=0 to N/2-1) of the latter input data G.sub.p as either real or imaginary parts f.sub.n.sup.R or f.sub.n.sup.I (n=0 to N-1) of even and odd numbered DFT's or IDFT's f.sub.2n' and f.sub.2n'+1 (n'=0 to N/2-1) of the original input data F.sub.k. The pre-processor extracts from the input data F.sub.k a truncated sequence of conjugate symmetric or antisymmetric components H.sub.m, N/2+1 in number, extracts from the truncated sequence conjugate symmetric and antisymmetric components A.sub.p and B.sub.p, [N/4]+1 in number where the brackets are the Gauss' notation, and calculates complex products of ones of the latter components A.sub.p or B.sub.p and factors, such as jexp(-j[2.pi./N]p) for DFT's or jexp(j[2.pi./N]p) for IDFT's, sums of the products and the others of the latter components B.sub.p or A.sub.p, differences between the products and the others B.sub.p or A.sub.p, and conjugate complex data of the differences. For the real parts f.sub.n.sup.R, the sums and the conjugate complex data provide the intermediate data. For the imaginary parts f.sub.n.sup.I, the differences are used instead of the sums. For factors exp(-j[2.pi./N]p) or exp(j[2.pi./N]p), each of the other components B.sub.p or A.sub.p should include a factor j.
摘要:
An A-D converter which oversamples the input analog signal, at a frequency greater than the Nyquist frequency, and achieves high precision linear coding by performing simple operations at a high sampling frequency f.sub.H while complicated operations are performed at a low sampling frequency f.sub.s. The high sampling frequency may be reduced to the low sampling frequency through a two-step reduction using a sampling frequency converter to reduce the frequency to an intermediate frequency f.sub.M and an integrator/sampler to reduce the sampling frequency further to f.sub.s or directly with the use of an FIR filter having a frequency characteristic in which attenuation is large in the out-of-band and gain deviation is small in-band.