MIXER_LOAD_DIFFERENTIAL_AMPLIFIER

Published:2009/7/15 23:25:00 Author:Jessie | From:SeekIC

Two different amplifier stages are used as the load of the mixer TUA2017 or MTl13006 (products developed by Siemens Co.). The LQ frequency is fixed at 483 MHz, because a commercial SAW oscillator at 483 MHz can be used as a local oscillator. If the RF frequency is swept from 433 to 633 MHz, then the IF frequency also is swept from 0 to 200 MHz. Compared to a passively loaded mixer, this combination of mixer and differential amplifiers exhibits excellent performance. The relative amplitude (amplitude difference between the fundamental frequency and the largest distortion frequency) is typically at least 50 dB. But it is only 30 dB (or less) in the case of a passive load mixer. Resistors R4, R5, R11, and R12 are used as the shunt feedback to obtain the flat output amplitude when the RE frequency is swept. The amplitude ripple with the IF bandwidth (0 to 200 MHz) is less than 0.5 dB.



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