| 摘要 |
PURPOSE:To convert directly a digital signal into an analog sigal by inputting a corresponding bit-encoded signal to a piezoelectric element through impedance represented as Z0{2<(>N<-k-1)>} (where Z0 is the impedance of piezoelectric element). CONSTITUTION:Impedance elements Z1, Z2-Z(N-1) are connected to (N-1) sets of piezoelectric elements individually in series. The value of this serial impedance Zk is Z0{2<(>N<-k-1)>}, where k is a bit number. When a digital electric signal with constant amplitude is applied to an electroacoustic transducer through the respective impedance elements Zk, the respective impedance elements Zk connected to respective bit channels have voltage drops to apply the respective piezoelectric elements with voltages proportional to weights of respective bits, radiating sound pressure proportional to each bit weight. This is added to sound pressure radiated by a piezoelectric element corresponding to another bit to regenerate and radiate an analog acoustic signal. |
