| 摘要 |
Apparatus (119) for compensating the effects of non-linearities in a frequency ramp (90, 92) includes a delay element (120) coupled to receive the ramp signal; a signal mixer (122) for mixing together the direct and delayed ramp signals to produce their sum and difference frequencies; a filter (124) selecting the difference frequency; and a device (126) responsive to the difference frequency for producing timing pulses having a frequency which is dependent upon the difference frequency. The timing pulses define the instants of time at which the frequency of the ramp has changed by a prescribed amount DELTA f, and can thus be used as a timing reference in a utilisation device receiving the frequency ramp. In a first embodiment (shown), a transponder system has a transceiver wherein the frequency ramp is transmitted (106) and wherein frequencies received from the transponder are analyzed (118). The timing pulses are then used to strobe the receiver sample-and-hold device (114) and A/D converter (116). In a second embodiment (Fig. 5), the ramp is used to deflect a laser beam using an acousto-optic modulator, and the timing pulses are applied to a Q- switch which controls beam intensity. <IMAGE> |
