InGaAs/GaAs HBT based MMIC differential VCO for S-band satellite communication applications

This paper presents that MMIC differential voltage controlled oscillator (DVCO) is designed and fabricated with considerably low phase noise. A fully integrated VCO in S-band is applied on InGaAs/GaAs heterojunction bipolar transistor (HBT) technology. The MMIC DVCO has attractive output power and lower phase-noise performance, while drawing lower current than that of the BJT or MOS family differential VCO. In order to generate negative resistance at S-band microwave frequency, a cross-coupled capacitive feedback topology between differential transistors is used. The phase noise is -118.85 dBc/Hz at 1 MHz offset and -96.7 dBc/Hz at 100 KHz offset at 3.583 GHz and the peak output power swings between 3.23 dBm to 3.65 dBm. The frequency tuning range is about 143 MHz. The standard IF frequency for satellite communications is either 70 MHz or 140 MHz. Therefore, the VCO output frequency can easily be tuned at 140 MHz frequency for the S-band satellite communications. The designed MMIC differential VCO is fabricated within the die size of 900 × 850 ¿m² on the GaAs substrate basement.