Browsing by Subject "VCO"

Now showing 1 - 3 of 3

Open Access
Cross-coupled CMOS voltage controlled oscillators operating in the X-band
(2023-06) Soygür, Can
Voltage controlled oscillators (VCOs) are electronic devices whose oscillation frequencies can be tuned by applying an external control input. A widely preferred topology is the cross-coupled VCO topology, which offers easy implementation inside integrated circuits. VCO designers take certain performance metrics into account for their designs, with the most prominent ones being the frequency tuning range and the output phase noise. These two metrics often require trading off from one another; as introducing more networks for tunability increases the overall noise within the device. With the aim of observing this trade-off between the tuning range and phase noise, four VCOs have been designed and fabricated in a single die with a 0.18 µm CMOS process. They are designed to operate in the X-band, at almost the same oscillation frequencies, to allow for easier comparison. Each VCO in the IC offers either more tunability with more tuning circuits or better phase noise performance with simpler circuits. Measurement results verify this hypothesis; a decrease in output phase noise is observed in the tested VCOs that contained simpler tuning network. With center frequencies of oscillation at approximately 12 GHz in the VCOs, tuning ranges as high as 25% are achieved in the VCO with most tunability, while phase noises as low as -106 dBm/Hz (at a 1 MHz offset) were achieved in the one with no tunability.
Open Access
MMIC VCO design
(1995) Erdem, Aykut
In this study, three voltage controlled oscillator (VCO) circuits are realised using Monolithic Microwave Integrated Circuit (MMIC) technology. Two of the VCOs are in the capacitive feedback topology, whereas the last one is designed by using the inductive feedback topology. GaAs MESFETs are used as both active devices and varactor diodes. Designed for a 50il system, the circuits operate in 8.88-10.40GHz, 8.7T10.23GHz and 8.96-12.14GHz ranges. Their output powers are well above the 9.5dBm for most of the oscillation band. All three VCOs have harmonic suppressions better than 30dBc. Both small signal and large signal analysis are carried out. The layouts are designed by GEC Marconi’s F20 process rules and the circuits are produced in this foundry
Open Access
X-band low phase noise mmic vco & high power mmic spdt design
(2014) Osmanoğlu, Sinan
Generally the tuning bandwidth (BW) of a VCO is smaller than the tuning BW of the resonant circuit itself. Using proper components with right topology can handle this problem. In order to overcome this problem and improve the tuning BW of the VCO, common-base inductive feedback topology with Gallium Arsenide (GaAs) Heterojunction Bipolar Transistor (HBT) is used and an optimized topology for tank circuit is selected to minimize the effect of bandwidth limiting components. Designed VCO with this topology achived -117 dBc/Hz at 1 MHz offset phase noise with 9-13 dBm output power between 8.8-11.4 GHz band. Second part of the thesis composed of Single Pole Double Throw (SPDT) RF Switch design. From mesa resistors to SPDT fabrication, everything is fabricated using Bilkent University NANOTAM Gallium Nitride (GaN) on Silicon Carbide (SiC) process. Switching HEMTs are fabricated to generate a model to design SPDTs and the final design works between DC-12 GHz with less than 1.4 dB insertion loss (IL), -20 dB isolation and 14.5 dB return loss (RL) at worst case. The power handling of the switches are better than 40 dBm at output with 0.2 dB compression, which is measured with continuous wave (CW) signal at 10 GHz.