"IR-UWB Indoor-positioning Receiving system Pulse Rising-edge Detection and Pulse-broaden Research“ proves us a novel Charge-pump PLL receiving system with AGC. By analyzing the time-response , traditional tensof nanosecond, of the rising-edge circuit composed of a transistor, they concluded that the input of pulse leading edge detection circuit is nanosecond stage. Thus to elevate the accuracy of the detection, they want to realize that Before positive pulse arrives, the transistor quickly into the saturate status(the rise time of optional transistor BFP650 is 0.2ns), base region accumulates excess stored charge (minority carriers), capacitor C charged rapidly, Uout level decline; when negative pulse arrives, the transistor will not withdraw from saturated to cut-offstate immediately. Base loop generates reverse current to extract storage charge, before storage charge exhausted,electron concentration gradient in base region will not change, Ic would maintain at Ics, transistor remain saturated[8]. This will speed up the discharge of capacitor C, charge stored in capacitor C will exhausted before the arrival of the next positive pulse, Uout back to high level. When the next positive pulse arrives, C will recharge again, and output level reduced.
If could extracted emit pulse arrive information from AGC circuitof three receiver output pulse signal cluster (Figure 4) , could use directly time difference extracted TDOA positioning system to locate the emission label.However,when the emit pulse width is 1ns, the output of pulse rising-edge detection circuit is not the desired signal envelope, but a pulse cluster with filtering effect (Figure 8).
Because the output of pulse rising-edge detection circuit is still a pulse cluster, in order to reduce the phase locked loop tracking error of PLL caused by multi-path envelope, signal needs to compare stretch before send to PLL. Larger pulse in front of the Pulse cluster contains arrival time of transmitted signal of transmitter. By setting a reasonable threshold, a comparing circuit, realized by LT1720 ,to could eliminate filter the smaller follow-up multi-path noise, then two spike pulse signal would obtained.And the broading function is realized by second chip of LT1720. Done!
转载于:https://www.cnblogs.com/endeavor/archive/2012/08/30/2664283.html