Friedrich Lenk

Low phase noise MMIC VCOs for Ka-band applications with improved GaInP/GaAs-HBT technology

We report on the technology and performance of fully monolithic coplanar voltage-controlled oscillators (VCOs) with GaInP/GaAs-HBTs as the active devices. With our optimized HBT process, the parasitic base resistance R/sub B/ and extrinsic base-collector capacitance C/sub EX/ are significantly reduced. In this way, the maximum frequency of oscillation F/sub max/ is increased from 100 to 170 GHz. This allows us to realize fundamental 38 GHz-VCOs with very low phase noise. At an oscillation frequency F/sub res/=34.2/spl plusmn/0.2 GHz, the VCO reaches phase noise levels of -87 dBc/Hz @ 100 kHz and -108 dBc/Hz @ 1 MHz offset frequency, respectively. To our knowledge, these phase noise values are the lowest GaAs data for Ka-band applications reported so far.

On the simulation of low-frequency noise upconversion in InGaP/GaAs HBTs

Residual phase-noise measurements of GaAs heterojunction bipolar transistors (HBTs) with different low-frequency noise properties are used to investigate how accurate a compact HBT model can predict the upconversion of low-frequency noise under nonlinear operation. We find that the traditional low-frequency source implementation, as well as a cyclostationary noise source implementation, have shortcomings under different operation conditions. While, in general, the cyclostationary approach yields much better results, it fails under certain operation conditions. Experimental evidence is given that this is caused by overestimated correlation between baseband noise and RF noise sidebands. It is shown that a model based on cyclostationary sources with reduced cross-correlation yields good agreement between measurement and simulation in all cases.

Low phase-noise GaInP/GaAs-HBT MMIC oscillators up to 36 GHz

Monolithic coplanar 18 and 36 GHz oscillators with GaInP/GaAs-HBTs and on-chip resonators are presented. Measured phase-noise reaches -93 dBc/Hz and -91 dBc/Hz at 100 kHz offset for 18 and 36 GHz, respectively. These values demonstrate that GaAs-HBT oscillators yield a phase-noise performance comparable to SiGe-HBTs, with the potential for higher frequencies.

38 GHz push-push GaAs-HBT MMIC oscillator

Two differential coplanar MMIC HBT oscillators are presented, a fixed frequency and a VCO version. They provide single-ended output at the second harmonic at 38 GHz as well as differential output at 19 GHz. The oscillators show excellent phase noise performance, the fixed-frequency type reaches -95 dBc/Hz at the fundamental frequency and -89 dBc/Hz at the second harmonic, at 100 kHz offset.

New extraction algorithm for GaAs-HBTs with low intrinsic base resistance

A new algorithm for extraction of the small-signal equivalent circuit elements of HBTs is presented. An analytical non-iterative approach is used in order to ensure physical significance of the extracted parameters. In order to enhance the robustness and reliability of the extraction routine, a simplified formula to determine the intrinsic base resistance R/sub b2/ Is presented. The new algorithm is verified by extraction of GaInP/GaAs HBT equivalent-circuit elements.

Modeling of low-frequency noise in GaInP/GaAs hetero-bipolar transistors

Accurate low-frequency noise modeling is a prerequisite for oscillator phase-noise simulation. In this paper, the LF noise sources of GaInP/GaAs HBTs are investigated. It turns out that the 1/f-noise model must contain two sources, the base-emitter diode and the emitter resistance. Quantitatively, excess noise power at 100 kHz scales with the square of collector current-density.

Towards a unified method to implement transit-time effects in Pi-topology HBT compact models

Four different approaches to include transit-time effects into /spl Pi/-topology HBT equivalent circuits are investigated in order to assess their compatibility with the physics-based T topology. The aim is to find an implementation that not only yields an exact model but also has a unique set of parameters in both the /spl Pi/ and T cases. This is of prime importance for reliable parameter extraction and thus the physical significance of the model. It is achieved using a transcapacitance approach. The theoretical considerations are supported by a practical example comparing measured and modeled HBT behaviour.

On the load-pull effect in MMIC oscillator measurements

Low phase-noise MMIC oscillators are key components for microwave and mm-wave systems. As a consequence, phase-noise measurements of these circuits have become a subject of growing interest and importance. This paper demonstrates that MMIC oscillator circuits with their relatively low Q factors are prone to specific measurement errors. Caused by a load-pull effect, the measurement system can become part of the oscillator, which yields phase-noise data significantly below reality. Special care has to be taken in order to avoid such phenomena.

24 GHz Low Power VCOs and Analog Frequency Dividers

24 GHz VCOs and frequency dividers with very low power consumption are presented. The circuits are realized as GaAs HBT MMICs. They comprise a VCO with high efficiency >17% and 12% tuning range at only 18 mW DC consumption as well as several frequency dividers. In order to minimize power consumption, the latter use the injection-locked frequency-divider (ILFD) concept. Divider ratios of 2 and 4 are realized, power consumption as low as 25 mW for a divider-by-2 is achieved. This demonstrates the capabilities of the analog concept in realizing dividers for mm-wave frequencies at DC consumption levels far below their digital counterparts

W-band flip-chip VCO in thin-film environment

A flip-chip packaging approach for W-band GaAs chips is presented using thin-film structures on silicon as carrier substrate. Reliability investigations indicate that, depending on bump size, the CTE mismatch is not critical and an underfiller does not provide distinctive benefits. A 77 GHz VCO GaAs-HBT MMIC is flip-chip-mounted to demonstrate validity of the packaging scheme.