Alan Victor

A voltage controlled oscillator using barium strontium titanate (BST) thin film varactor

Barium strontium titanate (BST) has a field-dependent permittivity and can be used as a dielectric in voltage tunable capacitors or varactors. These BST-based varactors are passive devices and have significantly different properties compared to semiconductor varactors. A voltage tunable oscillator using a BST thin film varactor was designed and characterized. The frequency of oscillation varied from 34.8 MHz to 44.5 MHz (28% tuning) upon application of 7 V tuning voltage. The VCO gain was 1.38 MHz/V and the 2nd harmonic was over 23 dB below the fundamental throughout the tuning range.

Voltage Controlled GaN-on-Si HFET Power Oscillator Using Thin-Film Ferroelectric Varactor Tuning

A 1.6 GHz power oscillator with a GaN-on-Si heterostructure field effect transistor (HFET) is reported. The voltage-controlled oscillator used a thin-film barium strontium titanate (BST) interdigital varactor as the tuning element. The surface-mount varactor was fabricated using sputtered BST film and copper metallization on alumina. An output power of 1.6 W (32 dBm) is obtained with a DC conversion efficiency of 25.5%. Flat tuning sensitivity of 500 kHz/V, 49 MHz linear frequency tuning, and power flatness of better than 0.5 dB are obtained with 0-100 V tuning voltage. The maximum oscillator phase noise is -81.4 dBc/Hz at 100 kHz offset

Time-Domain Modelling of Phase Noise in an Oscillator

This paper presents a time-domain simulation of phase noise in a varactor-tuned voltage-controlled oscillator. Flicker, thermal and shot noise are captured using transient sources of noise based on the principles of mathematical chaos. High levels of noise are handled by replacing the ordinary differential equations used in conventional transient circuit simulation by stochastic differential equations. The system of stochastic differential equations is interpreted in the sense of Stratonovich. Simulation runs are compared with measured phase noise of the oscillator and an accurate match is found for different levels of bias

Reflection Coefficient Shaping of a 5-GHz Voltage-Tuned Oscillator for Improved Tuning

Negative resistance voltage-controlled oscillators (VCOs) are systematically designed to operate with loaded resonator networks that permit stable steady-state oscillation over a specified tuning bandwidth. Circuit parasitics, however, significantly affect tuning behavior and complicate straightforward design. This paper introduces a scheme that compensates for the effect of parasitics by introducing an embedding network that modifies the effective active device reflection coefficient and thus enables conventional one-port oscillator design techniques to be used. A common-base SiGe HBT VCO operating from 4.4 to 5.5 GHz demonstrates the technique. Phase noise is better than -85 dBc/Hz at 10-kHz offset from the carrier and the second harmonic is less than -20 dBc, while higher order harmonics are less than -40 dBc. The voltage-tuned oscillator demonstrates an oscillator figure-of-merit of at least -182 dBc/Hz over a 800-MHz tuning range. The phase-noise-bandwidth (in megahertz) product is -159 dBc/Hz.

An analytic technique for trade-off of noise measure and mismatch loss for low noise amplifier design

An analytic technique and figure-of-merit (Fnm) for the trade-off of noise measure and mismatch loss in the design of a low noise amplifier is presented. The trade-off between various design parameters as a function of inductive source degeneration is evaluated from design curves developed and are shown to be unique to the selected device. Several devices demonstrated conditions whereby the use of source degeneration leads to instability and must be avoided. The technique is straightforward and permits pre-screening of potential devices being considered for low noise amplifier design. The resulting design curves permit accurate selection of the range of acceptable feedback values to achieve desired performance. The new figure-of-merit allows designers to choose the optimum value of source inductance either analytically or graphically. The new methodology is discussed and applied to a low noise amplifier design at 10.24 GHz.

Improved Y factor noise measurement using the second stage contribution to advantage

The ultimate limitation to characterizing noise in microwave amplifiers derives from the noise inserted by the front-end of the measurement set. Typically a high-gain low noise preamplifier is used in the measurement set to improve accuracy. Even then there is a limit to the minimum noise factor that can be measured. In this paper an extended Y-factor noise measurement technique is presented that utilizes an amplifier stage identical and in addition to the amplifier under test to enhance measurement accuracy. Utilizing a calibrated noise source, the output noise power of first a forward cascade of the two amplifiers is measured and then that when the amplifiers are arranged in reverse cascade. The use of a spectrum analyzer or power meter with a readily measured change in noise power reading is required as well as a calibrated noise source.

Design of a C-Band Microstrip Voltage Controlled Oscillator Using an Electromagnetic-Harmonic Balance Co-Design Technique

A voltage controlled oscillator (VCO) was designed for operation in C-band for use in a microwave point-to-point radio system. Microstrip technology was chosen for resonator implementation since it offers ease of manufacturing and frequency adjustment The design was performed using an electromagnetic (EM)-harmonic balance co-design technique in order to achieve first pass success. The measured frequency versus tune voltage data shows excellent agreement with simulation. Maximum deviation of 2% between the two was observed. The VCO tuned from 4.3 GHz to 5.4 GHz as the tuning voltage was varied from 0 to 9V representing a tuning bandwidth in excess of 20%. Phase noise over the tune range was better than -108 dBc/Hz at 100 kHz offset.

Tracking Phaselock Loop Characteristics with a VCO Using a Barium Strontium Titanate (BST) Thin-Film Varactor

Barium strontium titanate (BST) varactors utilized in a VCO demonstrate unique tuning characteristics compared to junction varactors. A 2.7 GHz microstrip line VCO operates in a tracking phaselock loop configured as an X4 frequency multiplier. BST oscillator tuning and the effect on loop dynamics is observed by the intentional design of an under damped system. Oscillator noise correction and peaking is noted particularly at low tune voltages. Loop dynamics are addressed through proper design of the loop compensator filter. The differences between BST varactor and junction varactor operation in frequency control are noted