There is an increasing demand for wireless commercial applications operating at millimeter-wave frequencies. The emergence of millimeter-wave wireless applications such as LMDS, WLAN and automotive anti-collision radar has brought new requirements on device technology and the systems used to characterize these devices at higher frequencies.


Many researchers specifically require the noise properties of the emerging millimeter-wave transistors. Fortunately, a new line of noise parameter measurement systems from Maury Microwave provides such a fully dedicated automated test system with frequency capabilities up to 110 GHz.

Noise parameters are used to describe noise behavior of a linear two-port device and are essential in designing low noise amplifiers (LNA) and transceivers. Manufacturers do not usually provide noise parameters obtained directly at mm-wave frequencies. When they are provided, they are most likely derived by extrapolation from values measured at microwave frequencies. Clearly, more accurate mm-wave noise parameter measurements are needed in device characterization as well as in the development and verification of device dependent equivalent circuit models.

By providing state-of-the-art device characterization, this new series of millimeter-wave noise parameter measurement systems allows designers to improve overall circuit performance for a given fabrication process by enhancing transistor operating range and linearity. These test systems encompass a wide range of high performance features designed for on-wafer testing. Specific models and added options offer higher levels of noise measurement capabilities and system integration, in addition to fast and accurate S-parameter measurements. This article describes the complete measurement solutions that are now available with frequency coverage up to 110 GHz.

Measurement System Specifics

The typical measurement setup for the fully automated wideband noise parameter measurements is shown in Figure 1. This setup is illustrated using the functional blocks and connectivity that comprise the system. Among the functional blocks, there is a network analyzer for S-parameter measurements, a noise source, an input tuner, an input switch, a noise receiver module and a noise figure analyzer (NFA) for noise parameter measurements. A solid-state noise source is used as a hot/cold noise reference needed in the noise figure measurement. Additionally, the system includes a DC power supply and bias tee to supply DC power to the device under test.

A key component in this measurement system is the automated electromechanical tuner that is used to change the reflection coefficient of the network connected to the input of the DUT. The reflection coefficient at the input reference plane of the DUT is controlled by the changing position of a moveable probe inside of a slab line or a waveguide section. Probe motions are precisely controlled using stepper motors. The system is capable of providing a maximum source reflection coefficient greater than a 0.9 magnitude at the DUT input reference plan. The available automated electromechanical tuners (see Table 1) used in the millimeter-wave noise parameter measurement systems are categorized by their frequency range and corresponding waveguide connector dimensions.

Typical Electromechanical Tuner Specifications

The typical tuner specifications include a minimum matching range of 20:1, a maximum VSWR of 1.06, maximum insertion loss of 0.65 dB, worst case repeatability > 50 dB and CW power handling of 20 W. Another key component of this highly accurate system is the noise receiver module. This module allows automatic switching at the DUT output between S-parameter measurements from the network analyzer and noise power measurements provided by the noise figure analyzer. The noise figure analyzer includes a low noise downconverter block to increase the system’s sensitivity across the entire frequency bandwidth and an optional bias tee. The noise figure analyzer is used only to measure noise power levels up to 26.5 GHz. Table 2 contains the specifications for the different models of the noise receiver module.

ATS version 4.0 software is used to control the measurement setup and to perform all the computations. Prior to the actual DUT noise parameter measurements, the passive network between the noise source and the noise receiver must be carefully characterized. The system performs the task of determining the unilateral transducer gain (kBG) as well as the noise parameters of the receiver during calibration using a thru calibration standard. In the multi-impedance measurement method only one hot noise power measurement with a minimum of four cold noise power measurements is taken during the noise figure measurements. After calibration, the thru standard is replaced by the DUT and at least four noise power measurements are made using different values for source reflection coefficient at the input.

Besides developing the necessary key hardware to perform noise parameter measurements over a broadband frequency range (up to 110 GHz), the system has also successfully integrated the Cascade Microtech automated probe stations for direct wafer testing. Figures 2 and 3 illustrate system integrations for a 50 GHz noise parameter system and a 60 to 90 GHz noise parameter and load-pull system.

Conclusion

Maury Microwave’s new fully integrated millimeter-wave noise parameter measurement systems are a unique solution addressing the increasing demand for mm-wave device impedance and noise characterization. The systems provide completely automated measurements, reducing expensive engineering set-up time while delivering an exceptionally high level of accuracy. Its ease-of-use and flexibility enables engineers to measure a broad range of high performance, leading-edge components, including very low noise transistors and amplifiers.

This level of accurate device information is critical for transistor development at higher frequencies, active model generation and, perhaps most critically, circuit optimization. The features available in the new series of Maury Microwave’s noise parameter measurement systems are ideal for addressing the challenges facing today’s R&D engineers developing millimeter-wave frequency components for the broadband wireless communications industries. Additional information may be obtained at www.maurymw.com.

Maury Microwave Corp.
Ontario, CA
(909) 987-4715

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