SIIT Commemorative Publication (10 Years of International ...

10 Years of International Cooperation: FTI, Nippon Keidanren and TUSIIT Commemorative Publication, 2002relatively high. In particular, an OCL approach to alow power, high frequency, low distortion linear QOhas never been reported.In this paper, a 1.9-GHz, 0.45-mW, 2-V CMOScurrent-mirror sinusoidal quadrature oscillator(Leelasantitham and Srisuchinwong 2002) through theuse of the internal capacitances of CMOS currentmirrors (Srisuchinwong and Leelasantitham 2001c,2000b) and the negative resistance is summarized. Thetechniques result in a new OCL approach to a lowpower, high frequency, low distortion linear QO. Theoscillation frequency (f 0 ) is 1.9 GHz and currenttunableover a range of 370 MHz or 21.6 %.Figure 1. Oscillograms of quadrature waveformsat 1.9 GHz.The amplitude matching and the quadrature phasematching are better than 0.029 dB and 0.15°,respectively. Total harmonic distortions (THD) are lessthan 0.3 %. Carrier to noise ratio (CNR) is 90.01dBc/Hz at 2 MHz offset from the 1.9 GHz carrier withapproximately 0.45 mW dissipation. The figure ofmerit CNR norm is 153.03 dBc/Hz. The ratio of theoscillation frequency to the transition frequency of thetransistor is 0.25. Comparisons to other approaches arepresented.Frequency f o (GHz )2.01.81.61.41.2Expected Oscillation FrequencySimulated Oscillation FrequencyExpected AmplitudeSimulated Amplitude151050-5Amplitude (dB )2. Performance1.010.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0-10Figure 1 depicts the resulting cosine and sineoscillograms of the quadrature currents i O1 and i z ,respectively, at I = 20 µA where the oscillationfrequency f 0 = ω 0 /(2π) is measured to be 1.9 GHz.Figure 2 illustrates plots of the oscillation frequencies(GHz) and the amplitudes (dB) of i O1 versus bias currentI, where the dotted lines indicate the expected analysisand the solid lines indicate the SPICE analysis. Asshown in figure 2, the oscillation frequencies are tunableby the bias current I over approximately 370 MHz andtherefore the tuning range is 21.6 %.Figure 3 depicts the amplitude matching (dB) in terms ofthe ratio i z / i O1 as well as the quadrature phase matching(degrees) in terms of (θ z −θ O1 ) of the quadrature currentsversus frequency. The amplitude matching is as near as0.029 dB whilst the quadrature phase matching for −90°is better than 0.15°. Figure 4 shows the power spectrumlevels (dBm) of the fundamental frequency at 1.9 GHzand the next harmonics of the oscillogram i O1 previouslydepicted in figure 1 using a commercially available fastFourier transform (FFT) program.As shown in figure 4, the distortions are due mainly tothe presence of the second harmonics, which isapproximately 51.5 dBm down from the fundamentalfrequency, and they remain essentially at the samemagnitude over the entire operational bias-current range(13 µA to 20 µA). Consequently, the total harmonicdistortions (THD) are less than 0.3 %.Figure 2. Plots of oscillation frequencies and amplitude versusbias current I.Amplitude Matching (dB):iZ / iO10.050.030.01-0.01-0.03-0.05Current I (uA)Phase AngleAmplitude1.4 1.5 1.6 1.7 1.8 1.9 2.0Oscillation Frequency (GHz)-89.7-89.8-89.9-90-90.1-90.2-90.3Phase Matching (deg)= (phase of iZ) - (phase of iO1)Figure 3. Amplitude and phase matching of the quadraturesignals versus frequency.3. Figure of MeritThe phase noise in figure 4 is equal to –90.01 dBc/Hzat 2 MHz offset from the 1.9 GHz carrier. In otherwords, the carrier-to-noise ratio (CNR) is equal to90.01 dBc/Hz at 2 MHz offset from the 1.9 GHzcarrier. The oscillator requires the total currentconsumption of 8I + 3G 0 I. For I = 20µA and G 0 = 1.1,the power dissipation (P DC ) is only 0.452 mW. Thefigure of merit CNR norm is given by (Tang et al. 2002)8