| 摘要 |
1,248,088. Digital microphones. INTERNATIONAL BUSINESS MACHINES CORP. 28 Feb., 1969 [1 March, 1968], No. 10803/69. Heading G4H. [Also in Division H4] In a condenser microphone, switching elements 10 to 15 are electrically coupled with a flexible electrode 1 and the number of switching elements 10 to 15 which change their states is a function of the distortion of the flexible electrode 1. The arrangement permits conversion of an acoustic signal into a digital electric signal for pulse code modulation use. Preferably the switching elements 10 to 15 are field-effect transistors with the flexible electrode 1 as a common gate electrode. Electrode 1 is a parabolic elongated diaphragm and the switching elements 10 to 15 are placed along the projection on a plate 2 of a radius of the electrode 1. The F.E.Ts 10 to 15 are followed by sampling circuits 20 to 25 which are controlled by a sampling control circuit 30. Each output of sampling circuits 20 to 25 is fed to a codling matrix 40 which converts 2<SP>n</SP> sampled input signals into n binary output signals. A clock 30 triggers the sampling circuits 20 to 25 so that their output signals are received serially by the coding matrix 40. At each particular value for the elongation of the diaphragm, one part of the F.E.T. arrangement is in the conducting state whilst the other part is non-conducting. The line of demarcation is found by sampling circuits 20 to 25 including "EXCLUSIVE OR" circuits. Two adjacent sampling circuits 20 to 25 are compared and an output is given only if one is conducting and the other is non-conducting i.e. an output signal is given only from that sampling circuit which is wired with the sampling circuits defining the line of demarcation. The circuitry comprising switching elements, sampler circuits and coding circuits may be a single semi-conductor chip fabricated using the Mesa technique. |
