Matthias Rudolph

Analysis of the Survivability of GaN Low-Noise Amplifiers

This paper presents a detailed analysis of the stressing mechanisms for highly rugged low-noise GaN monolithic-microwave integrated-circuit amplifiers operated at extremely high input powers. As an example, a low-noise amplifier (LNA) operating in the 3-7-GHz frequency band is used. A noise figure (NF) below 2.3 dB is measured from 3.5 to 7 GHz with NF<1.8 dB between 5-7 GHz. This device survived 33 dBm of available RF input power for 16 h without any change in low-noise performance. The stress mechanisms at high input powers are identified by systematic measurements of an LNA and a single high electron-mobility transistor in the frequency and time domains. It is shown that the gate dc current, which occurs due to self-biasing, is the most critical factor regarding survivability. A series resistance in the gate dc feed can reduce this gate current by feedback, and may be used to improve LNA ruggedness

A peeling algorithm for extraction of the HBT small-signal equivalent circuit

Direct extraction is the most accurate method for the determination of equivalent-circuits of heterojunction bipolar transistors (HBTs). The method is based on first determining the parasitic elements and then the intrinsic elements analytically. The accuracy and robustness of the whole algorithm therefore is determined by the quality of the extraction of the extrinsic elements. This paper focuses on a new extraction method for the extrinsic capacitances which have proven to be the main source of uncertainty compared to the other extrinsic parameters. Concerning the intrinsic parameters, all the elements are extracted using exact closed-form equations, including exact expressions for the base-collector capacitances, which model the distributed nature of the base. The expressions for the base-collector capacitances are valid for both the hybrid-/spl pi/ and the physics-based T-topology equivalent circuits. Extraction results for InP HBT devices on measured S-parameters up to 100 GHz demonstrate good modeling accuracy.

Direct extraction of HBT equivalent-circuit elements

We present an analytical method for determining the heterojunction bipolar transistors (HBTs) equivalent-circuit elements. Its special feature is that it does not need measurements of test structures nor optimizations. The new algorithm for extracting the intrinsic elements exploits the information contained in the frequency dependence of the network parameters. This leads to a fast algorithm with a unique solution. The method is validated treating GaInP-GaAs HBTs.

Scalable GaInP/GaAs HBT large-signal model

A scalable large-signal model for heterojunction bipolar transistors (HBTs) is presented. It allows exact modeling of all transistor parameters from single finger elementary cells to multifinger power devices. The scaling rules are given in detail. The model is verified by comparison with measurements of GaInP/GaAs-HBTs.

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.

GaN HEMT Potential for Low-Noise Highly Linear RF Applications

This paper presents a study of the capability of gallium-nitride (GaN) high-electron mobility transistors (HEMTs) to achieve low noise and high linearity performance. A packaged GaN HEMT was measured in a 50 - Omega system at 2 GHz. Noise figures slightly above 1.8 dB were achieved together with a record third-order intercept point of 54 dBm. The same configuration yields a maximum output power of 30 W, with 50% power-added efficiency. This combination of high power and low-noise performance allows the realization of highly linear low-noise amplifiers, which could significantly reduce protection and filter efforts at receiver inputs.

InP DHBT Process in Transferred-Substrate Technology With

In this paper, a double heterojunction bipolar transistor (DHBT) process has been developed in transferred-substrate (TS) technology to optimize high-frequency performance. It provides an aligned lithographic access to frontside and backside of the device to eliminate dominant transistor parasitics. The transistors of 0.8 times 5-mum2 emitter mesa feature ft = 410 GHz and fmax = 480 GHz at a BVceo = 5.5 V. Parallel to the device setup, a multilevel metallization scheme is established. It serves as construction kit for 3-D configurations of active and passive elements. High yield of the TS DHBTs, consistent large-signal modeling, and accurate simulation of complex passive elements have been demonstrated and have proved the availability of the technology for advanced millimeter-wave circuit design.

f_{t}

The base-collector capacitance and the collector transit-time in GaAs-based heterojunction bipolar transistors depend not only on base-collector voltage, but also on collector current. This has to be taken into account in a large-signal model. However, since collector transit-time and capacitance are both caused by the charge stored in the collector space-charge region, it is not possible to model them independently of each other. This paper investigates the interrelation between collector capacitance and transit-time due to transcapacitance effects, and presents an analytical unified description for both quantities, that is derived from measurement-extracted small-signal equivalent circuits. The model is verified by comparison of simulation and measurement data.

and

Extensive GaAs field-effect-transistor noise measurements are used to compare noise models with the aim of recommending the most useful one for monolithic-microwave integrated-circuit design. The evaluation is based on noise and S-parameter measurements of metal-semiconductor field-effect transistors and high electron-mobility transistors with different gatewidths in the frequency range of 0.05-26 GHz. The models under investigation differ in the number of independent coefficients necessary to calculate the four noise parameters of the device. The broad frequency range including radio-frequency frequencies down to 50 MHz requires two different noise measurement systems with special modifications for optimum performance. In conclusion, the two-parameter Pospieszalski model turns out to be the most suitable one.

f_{\max}

A highly rugged low-noise GaN MMIC amplifier is presented that operates in the frequency band 3-7 GHz. A noise figure NF below 2.3 dB is measured from 3.5 to 7 GHz, with NF < 1.8 dB between 5 and 7 GHz. The survivability of the LNA was assessed by several stress-tests, injecting in the input up to 36dBm at 4 GHz for 16 hours. To the authors knowledge, these are the most severe survivability tests for these circuits reported in the literature so far