Jason Breitbarth

A Local Oscillator for Chip-Scale Atomic Clocks at NIST

We describe the first local oscillator (LO) that demonstrates viability in terms of performance, size, and power, for chip-scale atomic clocks (CSAC) and has been integrated with the physics package at the National Institute of Standards and Technology (NIST) in Boulder, CO. This voltage-controlled oscillator (VCO) achieves the lowest combined size, DC power consumption, phase noise, and thermal frequency drift among those previously reported, while achieving a tuning range large enough to compensate for part tolerances but small enough to permit precision locking to an atomic resonance. We discuss the design of the LO and the integration with the NIST physics package

Additive Phase Noise in Linear and High-Efficiency X-Band Power Amplifiers

This paper compares additive (residual) phase noise of linear and highly saturated high-efficiency MESFET and HBT 10 GHz power amplifiers (PA). A custom discriminator measurement system is developed to characterize the PAs and exhibits a phase noise floor of -164dBc/Hz at 10 kHz offset for a 10 GHz fundamental. The additive phase noise measurements show a phase noise of -120dBc@1kHz for the class-E MESFET PA, a roughly 10-dB increase when compared to the class-A PA with the same device. The HBT amplifier exhibited nearly the same phase noise in class-E and linear class-A

Design method for low-power, low phase noise voltage-controlled oscillators

This paper presents a design method for voltage controlled oscillators (VCOs) with simultaneous small size, low phase noise, DC power consumption and thermal drift. We show design steps to give good prediction of VCO phase noise and power consumption behavior: (1) measured resonator frequency-dependent parameters; (2) transistor additive phase noise/ noise figure characterization; (3) accurate tuning element model; and (4) bias-dependent model in case of an active load. As an illustration, the design of a 3.4-GHz bipolar transistor VCO with varactor tuning is presented Oscillator measurements demonstrate low phase noise (-40dBc@ 100Hz and better than -lOOdBcfflOkHz) with power consumption on the order of a few milliwatts with a circuit footprint smaller than 0.6cm2. The temperature stability is found to be better than +/-10ppm/degC from -40degC to +30degC. The oscillators are implemented using low-cost off-the-shelf surface-mountable components, including a micro-coaxial resonator. The VCO directly modulates the current of a laser diode and demonstrates a short-term stability 2-10/radictau Bias of clock. when locked to a miniature Rubidium atomic clock.

Component-level demonstration of a microfabricated atomic frequency reference

We demonstrate component-level functionality of the three critical subsystems for a miniature atomic clock based on microfabrication techniques: the physics package, the local oscillator and the control electronics. In addition, we demonstrate that these three components operating together achieve a short-term frequency instability of 6times10-10/radictau, with a total volume below 10 cm 3 and a power dissipation below 200 mW

Measuring Transistor Large-Signal Noise Figure for Low-Power and Low Phase-Noise Oscillator Design

This paper presents an experimental method for determining additive phase noise of an unmatched transistor in a stable 50-Omega environment. The measured single-sideband phase noise is used to determine the large-signal noise figure of the device. From the Leeson-Cutler formula and a known oscillator circuit with the characterized transistor, the phase noise of the oscillator can be predicted. The method is applied to characterization of several bipolar devices around 3.4 GHz, the frequency of interest for miniature rubidium-based atomic clock voltage-controlled oscillators.

Absorptive near-Gaussian low pass filter design with applications in the time and frequency domain

The work presented here is for the design of an absorptive low pass filter for use in the time and frequency domain. The filter presented is absorptive in the stop band, flat in group delay to twice the half power frequency and near-Gaussian in shape. The design of the low pass filter is general with design examples in microstrip and coplanar waveguide at 40 GHz. Frequency domain measurements to 110 GHz and time domain measurements at 40 Gbits/s are presented. The absorptive filter presented has uses in pulse shaping, rise time alteration and harmonic matching.

Source impedance influence on cross-correlation phase noise measurements

The phase noise floor of an oscillator has been shown both theoretically and experimentally to be the ratio of the source noise power divided by the delivered power. In a 50Ω system this is determined by -177dBm - POUT in dBc/Hz. Recent measurements have shown what appears to be better than theoretical noise floors in some oscillators, assuming a 50Ω environment. However, oscillators rarely exhibit an output impedance of exactly 50Ω and vary significantly farther from the carrier. While the input impedance of a modern cross correlation analyzer may be 50Ω, the assumption the analyzer introduces 50Ω common mode noise can be erroneous. This paper presents theory and measurements that demonstrate the extremely low phase noise measured on some oscillators is real and not in violation of theoretical limits by isolating the noise sources in a series of additive phase noise measurements.

An additive phase noise measurement technique for mixers with non-DC IF in large signal

Mixer phase noise with respect to system level performance is often assumed negligible, measured using small signal Y-factor noise figure measurements or in some cases measuring noise direct at DC. AC coupled IF port mixers, such as triple balanced mixers, cannot be measured directly at DC and Y factor methods do not show phase noise contributions in large signal or the effect of flicker noise. A method is demonstrated in this paper that allows for direct large signal additive phase noise measurements at arbitrary (non-DC) IF frequencies and compares phase noise measurement results to the more common DC coupled measurement in the case of the double balanced mixer.

Spectral performance and noise theory of nonlinear transmission line frequency multipliers

In this paper the theoretical and measured spectral performance of nonlinear transmission lines (NLTLs) and their applicability to frequency multiplication is presented. NLTLs, through nonlinear dispersion in large signal, create a sharp edge from a sinusoid that is rich in harmonics, making a very effective frequency multiplier. While the design of NLTLs has been widely published [1–2] for high harmonic content, prior to this work, the noise performance of NLTLs has only been published in [3]. The results presented in this paper demonstrate the near ideal 20·log10N phase noise multiplication as referenced to the additive phase noise of the fundamental with N being the multiplicative factor. Theoretical analysis of the noise properties of NLTLs show the effect of DC biasing and the overall change in phase shift of the NLTL in sum with AM source noise has the most dramatic influence in additive phase noise and is confirmed by measurement. An NLTL design with a −187dBc/Hz input referred phase noise is presented.