Linus Boehm

Compact bistatic 160 GHz transceiver MMIC with phase noise optimized synthesizer for FMCW radar

This paper presents an ultra compact bistatic FMCW radar transceiver MMIC at 160 GHz with a mixer-based synthesizer concept. The integrated mixer converts a ramp signal with a stabilized local oscillator (SLO) signal to the RF output signal. The usage of a mixer reduces the frequency multiplication factor of the ramp signal and hence improves the phase noise at 160 GHz. The fixed frequency local oscillator for the up-conversion has a comparably small phase noise level compared to the ramp input signal and does not contribute significantly to the total phase noise level at 160 GHz. Apart from the synthesizer, the MMIC also includes a power amplifier with a maximum output power of 2 dBm, two efficient integrated antennas with a wide radiation pattern, and an IQ-receiver. Two FMCW radar responses recorded with a bandwidth of 20 GHz show the dynamic range of this sensor and its near range behavior. The compact SiGe MMIC requires only a chip area of 1.4mm × 1.0mm and consumes 285mW from a 3V power supply.

MMIC-to-waveguide transition at 160 GHz with galvanic isolation

In this paper a new approach for a monolithic microwave integrated circuit (MMIC) to rectangular waveguide transition is presented, which has no need for a specific package. The transition uses a partly integrated antenna with a patch radiator and a tapered dielectric waveguide to guide the wave into a widened metallic waveguide. Due to the usage of the dielectric waveguide the ground potentials of the MMIC and the metallic waveguide are galvanically isolated. The proposed transition was characterized in back-to-back measurements without probe-tips. A minimum insertion loss of 3 dB was measured. To the authors knowledge, this is the first approach of a galvanically isolated MMIC to metallic waveguide transition.

An automated millimeter-wave antenna measurement setup using a robotic arm

In order to measure antenna properties precisely at frequencies above 100 GHz, elaborate measurement techniques are required. This is especially challenging for integrated antennas, as probes require a steady, rigid measurement setup to avoid damage. This paper introduces an antenna measurement setup that allows fast and reliable 3-dimensional antenna pattern measurements in a frequency range of 60 GHz to 330 GHz. The system consists of a probe station, a vector network analyzer (VNA) and an industrial robotic arm with six axes. The robot ensures highly repeatable and accurate measurements and allows high flexibility in terms of scan geometry and resolution. Using a probe station, this setup not only supports measurements of waveguide-fed antennas, but also integrated antennas. After explaining the basic setup, measurement results are shown to demonstrate the capability of the system.

Influence of the wafer chuck on integrated antenna measurements

For meaningful pattern measurements of integrated antennas the devices, which are required during the measurement process, need to be optimized to influence the measurement results as little as possible. In this paper the errors caused by reflections on the chuck are investigated and quantified. A plastic chuck was built to reduce sources of reflection and thus improve the overall accuracy of the setup. The new chuck causes less ripples over the scanning angle and over the frequency and therefore, increases the performance of the setup significantly.

Scattering center determination for integrated antenna measurements at mm-wave frequencies

In this paper the results of integrated antenna measurements are analyzed to identify the main reflection locations when measuring with wafer probes. Two different approaches are described and the measurement results for two different probe designs are shown. First, the main reflection center on the wafer probe is determined by analyzing the measured far field radiation pattern at 160 GHz. The second approach is based on an extrapolation measurement of the antenna. It is shown that the reflective areas can be identified for both probe designs. The results can be used to assess the measurement uncertainty and to quantify the measurement error.

Reflection Reduction Through Modal Filtering for Integrated Antenna Measurements Above 100 GHz

Feeding integrated antennas during a measurement requires special feeding structures. Due to the small antenna dimensions, these feeding structures are often much bigger than the antenna under test (AUT) itself and with chip sizes of around 1 mm2, the achievable separation between antenna and feed is limited. Wafer probes have to be used to feed the AUT during passive antenna measurements and present a large reflective surface in close proximity to the AUT. Reflections from the wafer probe cause interference on the measurement surface and distort the results. The same is true for active antenna measurements, where bondwires and the package can have a significant effect on the radiated fields. The fragility and size of the components do not allow to reduce reflections with absorbers, which is why modal filtering was used in this paper to mitigate undesired reflections and improve the measurement result through postprocessing. Two issues that limit the performance of the algorithm are discussed, namely, phase center inaccuracies of the AUT and a limited measurement surface. It is shown that modal filtering is applicable to integrated antenna measurements at frequencies over 100 GHz and that a significant improvement in the measured radiation pattern can be achieved. Furthermore, it is shown that the postprocessed results make it possible to measure the directivity of integrated antennas, despite strong probe reflections.

The Challenges of Measuring Integrated Antennas at Millimeter-Wave Frequencies [Measurements Corner]

The increasing demand for radar sensors and the wide distribution of handheld communication devices push the development of low-cost components with a small form factor. One approach to achieve smaller, low-cost devices is the integration of the required components on a monolithic microwaveintegrated circuit (MMIC). At frequencies above 100 GHz, passive components are small enough to be integrated onto a chip, and the advances in semiconductor technology make it possible to build active components that can operate at millimeter (mm)-wave frequencies [1], [2]. The available bandwidths of several gigahertz at mm-wave frequencies offer high data rates for communication devices or high resolution for remote-sensing applications. By integrating the radio-frequency (RF) components and the antennas, lossy off-chip transitions can be avoided, thus limiting the required connections to the power supply and baseband signals.