| 摘要 |
An arrangement for compensating errors occurent in a quadrature modulator. The modulator includes means (1) for generating quadrature signals (cos a(t), sin a(t)) in the baseband, each of which signals is delivered to a respective branch in the modulator; means (2) for generating two high frequency signals (cos wt, sin wt) with a mutual phase difference of 90 degrees; mixers (3, 4) for mixing the quadrature signals (cos a(t), sin a(t)) with the high frequency signals (cos wt, sin wt) and an adder (5) for producing the sum of the output signals of the mixers (3, 4). Amplitude errors and phase errors are compensated with the aid of a separate compensating network (11, 12, 14, 16, 17, 19, 21) which is incorporated in the low frequency part of the modulator and which includes adjustable signal generating means (14, 16, 19). Local oscillator leakage is compensated with the aid of a second compensating network (13, 15, 18, 20) which is also incorporated in the low frequency part of the modulator and which also includes adjustable signal generating means (15, 18). The signals (k4, k5) from the latter means (15, 18) are subtracted from the signals occuring in the two branches of the modulator. |
