| 摘要 |
PURPOSE:To obtain the same performance figure G/T as that of a large-sized antenna by means of two sets of small-sized inexpensive antennas by using the 2 sets of the antennas and adding an RF signal from each antenna in phase. CONSTITUTION:A signal received by the 2nd antenna 1b and amplified by the 2nd low noise amplifier 3b with low noise is phase-shifted by a phase shifter 11, and an output of the phase shifter 11 and an output of the 1st low noise amplifier 3a are in phase and added by an adder 12. Since the S/N (signal to noise ratio) is improved by 3dB in this case, the overall G/T is improved by 3dB than the G/T of each antenna system resultingly. In a loop consisting of a subtractor 13, a down converter 4b, a gain control circuit 14, a level detector 16 and a phase shifter 11, the phase difference between two RF signals inputted to the adder 12 is eliminated by using a voltage proportional to the sinusoidal absolute value of the phase difference between the two RF signals inputted to the subtractor 13 to control the phase shift amount of the phase shifter 11. |
