| 摘要 |
PCT No. PCT/AU94/00287 Sec. 371 Date Dec. 5, 1995 Sec. 102(e) Date Dec. 5, 1995 PCT Filed May 30, 1994 PCT Pub. No. WO94/29975 PCT Pub. Date Dec. 22, 1994A fading simulator for generating multipath-faded test signals which have attenuation notches of precisely controllable frequency position and attenuation depth from a modulated input signal of known bandwidth. The input signal is fed to a splitter that directs two in-phase components to a first path and a second path. The input to each path is divided by a splitter into in-phase and quadrature sub-signals having a quadrature phase relationship, each sub-signal being fed to a respective inverting attenuator, the outputs of the attenuators then being combined in a combiner and the combined output being passed through a variable delay line to generate the output of the respective path. The outputs of each path are then combined in a combiner circuit to generate the multipath-faded test signal. All four inverting attenuators are preferably substantially identical to one another so that the two paths have close to identical temperature-drift and other characteristics. The attenuators and delay lines are electronically controlled in tandem, preferably using a microprocessor and stored program, to generate precision, static or dynamic, attenuation notches desired. |
