A Broadband Double-Conversion RF Tuner
Analog Integrated Circuits and Signal Processing
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This paper proposes a novel broad-band MMIC VCO using an active inductor. This VCO is composed of a serial resonant circuit, in which the capacitor is in series with an active inductor that has a constant negative resistance. Since the inductance value of this active inductor is inversely proportional to the square of the transconductance and can vary widely with the FETs gate bias control, a broad-band oscillation tuning range can be obtained. Furthermore, since this active inductor can generate a constant negative resistance of more than 50 Ω, the proposed VCO can oscillate against a 50-Ω output load immediately without using additional impedance transformers. We have fabricated the VCO using a GaAs MESFET process. A frequency tuning range of more than 50%, from 1.56 to 2.85 GHz, with an output power of 4.4±1.0 dBm, was obtained. With a carrier of 2.07 GHz, the phase noise at 1-MHz offset was less than −110 dBc/Hz. The chip size was less than 0.61 mm^2, and the power consumption was 80 mW. This broad-band analog design can be used at microwave frequencies in PLL applications as a compact alternative to other types of oscillator circuits.