| 摘要 |
Having digitized a wide dynamic amplitude range analog signal Vin and recorded it in digital word from comprising a binary coded mantissa A and a binary coded exponent E, where A and E are related to a constant radix or base (e.g., the decimal number 8) the present invention provides methodology and apparatus for converting A and E to an analog signal Vo of compressed dynamic amplitude range for the purpose of making playbacks in the form of oscillograms therefrom. As initially recorded in digital form the digital word is, mathematically, Vin=+/-A8<->E equation 1. According to one illustrative embodiment of the invention, in reconverting the digitally recorded A and E data to obtain the desired analog signal Vo, digital signals representing A are converted to an analog signal V(D-A) = AVref equation 5 where Vref is a periodic function of time t. Digital signals representing the E data are processed to provide a signal representative of a new exponent (K-E) where K is changed by a predetermined magnitude each time Vref attains a predetermined magnitude. Analog signal V(D-A)is delivered to an arrangement of cascaded amplifier stages, each of which has a gain of 8. The signal (K-E) gates the amplified V(D-A) signal through a particular stage of said amplifier arrangement to yield the analog signal Vo = V(D-A)8(K<->E)equation 6 which can also be stated as Vo = Vin Vref8K equation 7. Also, in accordance with the invention various forms of programmed gain control may be introduced in that a time varying gain function G(t) is applied to Vref. Moreover, in accordance with another aspect of the invention a form of automatic gain control is introduced by enabling signal Vo to control the rate of gain expansion. |
