| With continued introduction of new wireless applications, the available spectrum is becoming crowded. Because of this, interests for developing circuits and systems operating at higher frequencies have been increasing larger bandwidth and propagation properties of signals in the frequency range from 100 GHz to 3 THz have led to the recent increase in research efforts.;For the communication over 30m, use of antennas are better than using transmission lines at the frequency above 60 GHz. Use of on-chip antennas at high frequencies makes systems compact and lower cost, as well as potentially improve their performance. The impact of realistic metal interference structures which can significantly modify the characteristics of on-chip antennas, such as a power grid, local clock trees and data lines have been investigated using EM simulations. In the presence of a power grid, the antenna pair |S 12| can be traded off for improved stability of antennas characteristics and the predictability of on-chip antenna characteristics.;The radiation of a patch antenna is due to the fringing fields. The ground plane in the patch antenna decreases the coupling to near by circuits. The design of patch antenna in CMOS processes is limited by the fixed relatively low dielectric thicknesses. These limit the input resistance and efficiency. The bond wires change the radiation direction by ∼13° at the distance 12 of 50 mum from a patch for 250 GHz operation and decrease the input resistance by about 4 O. Increasing the separation to 150 mum, make the impact of bond wires negligible.;A 182-GHz Schottky diode detector is demonstrated in foundry 130-nm CMOS technology. A 182-GHz AM modulator is implemented by changing the gate bias of PMOS current source of a push-push oscillator which utilizes the 2 nd order harmonics. The operation is verified by the observation of 91-GHz AM signals at the fundamental using an OML harmonic mixer. The noise performance of a 250 GHz Schottky barrier diode detector with an on-chip patch antenna in 90 nm CMOS also have analyzed.;To overcome the difficulties of electrical measurement techniques for submillimeter-wave circuits, optical techniques are utilized. The power and spectrum of 250-GHz and 410-GHz push-push oscillators have been measured using a bolometer (HD-3, IR Lab) and FTIR (IFS 113v, Bruker). A 250-GHz push-push oscillator with an on-chip patch antenna fabricated using a 90-nm CMOS process is demonstrated. A ring oscillator is incorporated for the generation of 250-GHz AM signals. The 125-GHz AM signal is measured using a harmonic mixer and a spectrum analyzer. The radiated second harmonic power from the patch antenna is about -32 dBm. A 410-GHz push-push oscillator with an on-chip patch antenna fabricated using low leakage transistors of a 45-nm CMOS process with 6 metal layers is demonstrated. The patch antenna size is 200 x 200 mum2 . The radiated second harmonic power from the patch antenna is about -49 dBm. The 410-GHz operating frequency is the highest among the transistor circuits fabricated in any technology including the III-V technologies. These suggest the possibility of CMOS THz systems. |
