Signal conversion apparatus

Abstract

Identification of complex signals such as a specific phoneme spoken by different speakers is accomplished by analyzing and normalizing the spoken phoneme's group of frequencies (formants) to a standard group, while maintaining the original harmonic-ratio information as channel number differences. A set of filters followed by rectifiers, to an electronic switching matrix, shifts the original filter output set through sequential sets of channels until the fundamental frequency at some input channel activates the lowest numbered ouput channel.

Parent Case Text

This is a continuation of application Ser. No. 235,943, filed Mar. 20, 1972 .

Description

This invention involves the identification of complex signals such as a specific phoneme spoken by different speakers. The basic problem, for example, may be that of recognizing a phoneme spoken in a low-pitched voice, and the same phoneme in a higher-pitched voice. It is well-known that a specific phoneme is a complex wave consisting of harmonically related frequency peaks, or resonances. Thus, it is well known that normalizing any arbitrarily pitched phoneme to a standard pitch set of harmonic frequencies representing the phoneme may simplify the recognition process. Such normalizing to a standard configuration may be accomplished by various forms of signal conversion systems.

This invention relates to signal conversion systems, and more particularly to a novel filter plus switching arrangement for regrouping (shifting) randomly originated complex signals to a reference grouping for simpler processing in a recognition device, for example, speech sound waves, voice print waves, sonar target waves, and so on.

Thus the particular arrangement disclosed herein is contemplated as being sufficiently versatile for a wide scope of uses, as will be apparent from the following specification in conjunction with the accompanying drawings, wherein:

FIG. 1 is a partly block and partly schematic diagram of the invention;

FIG. 2 shows the special center frequency sub-divisions of the pass-band filters, as used in the present invention;

FIG. 3 is a numerical chart showing how the detected signal outputs of the pass-band filters are switched linerarly to the outputs of the numerically arranged channels in accordance with the present invention; and

FIG. 4 shows how a plurality of and-gates (analog switches) can be physically oriented on a planar surface for simple interconnections of terminals for the required switching arrangement.

In order to obtain high accuracy of signal regrouping without causing any cross switching of the input signal to the channel outputs, the center frequencies of the sub-dividing pass-band filters are arranged as in FIG. 2, wherein the sub-divisions are similar to the standard musical scale. In this arrangement, it will be noted that the sub-divisions are arranged in a series of digitals at like intervals in harmonic successions corresponding to the digitals in preceding intervals. Thus, the numerical ratios of the numerals from the second through the thirteenth numerals with respect to the first numeral is the same as the numerical ratios of the fourteenth through the twentififth numeral with respect to the thirteenth numeral, as exemplary demonstration. Such a numerical arrangement simplifies the actual channel switching arrangement, because it requires linearly sequenced numerical transfer without cross coupling of any of the pass-band outputs, such as would be by the arrangement of pass-band center frequencies of the filters shown in FIG. 11, and the chart of switching combinations in FIG. 12 of my related U.S. Pat. No. 3,622,706 issued Nov. 23, 1971. This is shown in greater clarity by the numerical chart in FIG. 3, wherein the top row of the numerals represent the channels, and the rows of numerals below represent the sequence of the numerals left hand of the sub-band frequencies in FIG. 2. For example, in the first row (FIG. 3), all of the detected outputs of pass-band filters (starting from filter number-1) are applied to the inputs of the channels starting from channel number-1. In the second row, the detected filter outputs starting from the number-2 filter are applied to all of the channels starting from the channel number-1, and so on. As stated in the foregoing, such simplicity of switching sequence becomes inherently accurate, as long as the harmonic sequence at like intervals is considered in sub-dividing the sound spectrum, because the number of sub-band divisions and center frequencies of the pass-band filters may be arranged other than the frequencies shown in FIG. 2 without affecting the required accuracy.

Switching apparatus of FIG. 4

In reference to the chart shown in FIG. 3, it is apparent that the use of a large number of switching transistors is required for the switching performance. While multiple element channel swiches in small packages of integrated circuits are available, it still will require large surface of printed circuit board with a large number of terminals to be soldered. Due to the simplicity of interconnecting design, however, a large number of these transistors, or any type of controllable semiconductors, may be integrated on a single wafer, such as shown in FIG. 4, wherein, each square represents the semiconductor as mentioned, three squares of which are shown in shaded lines in order to render them distinguishable in the maze of electrical connections. The connecting electrodes in each square are represented by the black dots to which are terminated the required parallel connections, as illustrated by the horizontal, vertical, and 45.degree. parallel lines; the first representing the source electrode terminals, the second representing the drain terminals, and the third representing the gate electrode terminals of MOS FET transistors, although other types may also be used. Similarly, if enormously large number of transistors are to be deposited on a single wafer, it may be preferable to divide the arrangement of FIG. 4 into segments, in flat packages with connecting terminals attached thereto, so that the terminals of these segments may be connected externally for the complete assembly, as required.

Having described the details of parts for signal conversion of complex groups of signals, an exemplary system for signal conversion is shown in FIG. 1.

Signal conversion system of FIG. 1

I have described novel signal conversion systems in my related patents, for example, U.S. Pat. No. 3,622,706, U.S. Pat. No. 3,659,051, and copending applications Ser. Nos. 97,893 and 209,661, and reference may be made to these disclosures. However a simpler arrangement, in an exemplary form, may be described by way of the arrangement in FIG. 1, wherein the voice signals in block 1 are applied to the pass-band filters in blocks 2 through 5, for sub-dividing the sound spectrum band in the sequence of resonances, as shown in FIG. 2. The outputs of these pass-band filters are first detected in the blocks 6 through 9, respectively, and applied to the drain electrodes of switching transistors Q1 through Q4 (these switching transistors may also be termed as and-gates for the purpose contemplated herein, and therefore, the same terminology will also be used in the appended claims), respectively. The source electrodes of these transistors are connected to ground in series with the output resistors R1, R2, R3, and Rn, which represent the channel outputs for signal conversion of the arriving signals from the detected signals in blocks 6 through 9. In accordance with the numerical chart of FIG. 3, any one of the detected signals in blocks 6 through 9 may be coupled to the resistor R1 of channel-1. This is done by the additional transistors Q5, Q8, Q10, the source electrodes of which are all connected in parallel with the source electrode of Q1. Thus, when the first distributor pulse from the pulse distributor in block 10 is applied to the gate electrode of Q1 the detected signal of block 6 is admitted to the output resistor R1. When the second distributor pulse is applied to the gate electrode of Q5 the detected signal from block 7 is admitted to the output resistor R1. By such sequential pulse distribution to the gate electrodes of Q1, Q5, Q8, Q10, it is seen that any one of the detected outputs of the pass-band filters may be admitted to the resistor R1 of the channel-1. By such example, similar signal transfers are made to the channel outputs across resistors R2, R3, and Rn, in the linear numerical order of the chart in FIG. 3, by the parallel connections of the gate electrodes of transistors Q1 through Q4; Q5 through Q7; and Q8-Q9, etc., as shown in the drawing. Thus, as the distributor in block 10 applies sequential pulses to the parallel connected gate electrodes, as shown, the detected signals in blocks 6 to 9 are sequentially transferred to the channel outputs in the signal regrouping combinations of the chart in FIG. 3. During this sequence, one of the signal regrouping combinations at the channel outputs may represent the desired information, which may be decoded, or used, for any particular purpose that may be desired.

While the arrangement of FIG. 1 is given in an exemplary form, showing how signal conversion may be accomplished by the novel transistor arrangements of FIGS. 1 and 4, reference may be made to my disclosures in my reference patents for greater details of these signal conversion systems, because the gating functions of these transistors in the arrangement of FIG. 1 and FIG. 4 is contemplated for a wide scope of uses, and accordingly, both the arrangements and specific parts that I have mentioned in exemplary form may vary without departing from the true spirit and scope of the invention .

Claims

What I claim, is:

1. The system normalizing spectral variations of a group of information-bearing harmonically related frequency peak resonances in a complex sound wave by converting and standardizing the channel-location identities of said resonances, the system comprising a plurality of band-pass filters for separating the resonances of said complex wave in divisions such that the center frequency of said filters are arranged in a monotonically increasing series of frequencies; said series comprising a plurality of sub-series, all sub-series having the same number of channels such that each frequency in a sub-series is harmonically related to the same-placed frequency in the other sub-series; said filters being numbered sequentially for identity from the reference numeral one; a plurality of detectors for derivng detected signals from said band-pass filters, said detectors having numerical identities the same as the associated filters; a signal conversion switching arrangement comprising a plurality of input and output channels numbered sequentially, said switching comprising a plurality of AND-gates numerically identified from a reference numeral; first parallel connections of the first inputs of the corresponding AND-gates to corresponding input channels, second inputs of corresponding AND-gates to corresponding channel-switching control-gate inputs, third parallel connections of the outputs of corresponding AND-gates to corresponding output channels; coupling means from said detectors to corresponding first inputs of AND-gates; means for energizing said parallel-connected second inputs sequentially for said signal-switching conversion, all input channels being switched simultaneously to sequentially lower-number channels, until said group of detected signals are admitted to the output channels in an order such that the detected signal having the lowest numerical identity within the input group of signals is switched to the output channel having said reference numeral one, while the other detected signals of the input group are switched to corresponding output channels, such that the information concerning input frequency harmonic ratios is maintained relative to the input fundamental frequency, and thereby having input channels to a normalized group of output channels.

2. Apparatus in the system as set forth in claim 1, wherein said plurality of AND-gates in each of said channels consist of semiconductor devices, each device having first and second electrodes for forming electrical conductive path therebetween, and a third electrode for controlling the resistance of said conductive path, and said devices are assembled in numerically identified plurality of rows in linear numerical successions from a reference numeral, in each of said rows said devices being identified numerically in linear numerical successions from said reference numeral, and said devices being numerically aligned in the assembly; first parallel connections of the first electrodes of the numerically corresponding devices in said parallel rows, respectively, for forming said first inputs of said channels; second parallel connections of the third electrodes of the numerically identified devices in the numerically succeeding rows with that of the third electrodes of the numerically succeeding devices from the numerically corresponding devices in the numerically preceding rows, respectively, for forming said second inputs of said channels; and third parallel connections of the second electrodes of the numerically identified devices in said rows, respectively, for forming said channel outputs.