Abstract 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.
An arrangement for compensating errors occurent in a quadrature modulator which includes means (1) for generating two quadrature signals (cos a(t), sin a(t)) in the baseband, each of said signals being delivered to its 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 said mixers (3,4), characterized in that the arrangement further includes adjustable signal generating means (14, 16, 21) for generating a first (k1), a second (k2) and a third (k3) signal; a means (11) incorporated in one branch of the modulator for forming a fourth signal which constitutes the product of the one quadrature signal (cos a(t)) and said first signal (k1); a means (17) for forming a fifth signal which constitutes the product of the second quadrature signal (sin a(t)) and said second signal (k2); a means (12) incorporated in said one branch for forming a sixth signal which constitutes the difference between said fourth signal and said fifth signal; and a means (19) incorporated in the other branch of the modulator for forming a seventh signal which constitutes the product of the second quadrature signal (sin a(t)) and said third signal (k3), whereby amplitude error and phase error are compensated by suitably adjusted values of said first to third signals (k1 - k3).
Claim 2
Dependent Claim
257 words
An arrangement for compensating errors occurent in a quadrature modulator which includes means (1) for generating two quadrature signals (cos a(t), sin a(t)) in the baseband, each of said signals being delivered to its 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 said mixers (3,4), characterized in that the arrangement further includes adjustable signal generating means (14, 16, 21) for generating a first (k1), a second (k2) and a third (k3) signal; a means (11) incorporated in one branch of the modulator for forming a fourth signal which constitutes the product of the one quadrature signal (cos a(t)) and said first signal (k1); a means (17) for forming a fifth signal which constitutes the product of the second quadrature signal (sin a(t)) and said second signal (k2); a means (12) incorporated in said one branch for forming a sixth signal which constitutes the difference between said fourth signal and said fifth signal; and a means (19) incorporated in the other branch of the modulator for forming a seventh signal which constitutes the product of the second quadrature signal (sin a(t)) and said third signal (k3), whereby amplitude error and phase error are compensated by suitably adjusted values of said first to third signals (k1 - k3).
Claim 3
Dependent Claim
101 words
An arrangement according to claim 1, characterized in that the arrangement further includes adjustable signal generating means (15, 10) for generating an eighth (k4) and a ninth (k5) signal; a means (13) incorporated in one branch of the modulator for forming a signal which constitutes the difference between said sixth and eighth signals; and a means (20) incorporated in the other branch of the modulator for forming a signal which constitutes the difference between said seventh and ninth signal, whereby local oscillator leakage is also compensated with the aid of suitably adjusted values of said eighth (k4) and ninth (k5) signals.