| 摘要 |
PURPOSE:To enable signal catching with one receiver even from a plurality of satellites, by adding an asynchronous AGC loop to a tracking receiver providing an AFC loop, detecting the presence of input signals and operating the AFC loop. CONSTITUTION:An input signal (a) is inputted to a mixer 1 via a variolosser 7 of an asynchronous AGC loop 12, the output is detected at a detector 8, and the detection signal is inputted to the variolosser 7 and a level detctor 9. The detection level is compared with a level slightly higher than the preset noise level, and if the detected level is higher than the set level, a control signal (b) operating an AFC loop 10 form a detector 9 is transmitted to a loop filter 3. When a signal is inputted from the mixer to a frequency discriminator 2, the filter 3 is an integrator, the AFC loop starts operation, the loop is closed and a phase locked loop PLL starts operation to catch signals. Even if objective satellites are in plural, since the AFC loop is operated after a signal is inputted to the discriminator 2, the signal can be caught with one receiver. |
