| 摘要 |
1,198,298. Vocoders. INTERNATIONAL BUSINESS MACHINES CORP. 27 Nov., 1967 [25 Nov.. 19661, No.53755/67. Heading H4R. In a function signal generator to generate excitation function signals to feed to the respective spectrum channels of a vocoder synthesizer a filter circuit is repeatedly fed with pulses derived from the excitation pulse and the resulting repetitive primary function signal from the filter is sampled at successively different points on succeeding repeats of the primary function signal in order to generate a lower frequency replica of the primary function signal. The period between samples is different in the different spectrum channels so that the signals generated consists of components lying in a range of frequencies whose centre frequency is appropriate to the respective spectrum channel, and whose bandwidths are the same for all channels. Fig. 1 shows a vocoder synthesizer in which excitation function signals are generated at the appropriate frequencies, modulated by the aggregate function signals SKS in modulators M1 to Mn, smoothed in low pass filters SM1 to SMn and combined to produce the synthesized speech at SO. The excitation function signals are generated by feeding excitation pulses from APL via "OR" gate OT to filter BF to produce a damped oscillation at a high frequency. The excitation pulse is also applied to delay unit VZ1, having a delay KNdt, and delay unit VZ2, having a delay Ndt, which are interconnected via "AND" gate UT and "OR" gate OT so that each excitation pulse is recirculated and applied to the filter input K times by recirculation through delay VZ2 until "AND" gate UT is inhibited by the inverted output of delay VZ1. Each resulting output from filter BF consequent upon each appearance of the pulse to the filter input is sampled N times by the switch SM and the samples are multipled on to the fixed contacts of switches S1 to Sn so that a complete series of samples making up one complete output signal sequence from filter BF is continuously available around the fixed contacts of switches S1 to Sn. The contact arms of switches S1 to Sn are then driven to read off the sequence of samples at such a speed, different for each spectrum channel, as to provide an excitation signal appropriate in frequency for the respective spectrum channel. The switches may be electronic rather than mechanical. |
