Ulf Johannsen

At lower frequencies, bulky and expensive impedance tuners and long cables are required to generate a well-spread impedance pattern to measure the noise parameters (NPs) of an active device. In this letter, we propose a four-term method in which well-characterized vector network analyzer (VNA) calibration kit standards, that is, open, short, and load are used with a single surface-mount capacitor or inductor as the source impedances. The uncertainty analysis of a cold source measurement example shows that the method accurately characterizes wideband low-frequency receivers. Furthermore, the bandwidth of the measurement method can be increased simply by changing the capacitor value, demonstrating that the proposed method is robust and cost-effective.

This paper presents a novel approach to low noise amplifier (LNA)-antenna co-design in the Q-band frequency range, leveraging the antenna as an integral part of the LNA matching network to achieve broadband noise figure improvement.Unlike conventional designs, the proposed LNA does not include a 50$\,\Omega$ input matching network, allowing direct access to the complex frequency-dependent impedance (${\Gamma _{opt}}$) associated with the LNA’s minimal noise figure (${NF_{min}}$). The antenna input impedance is optimized to match the LNA for minimal noise contribution, effectively enhancing system performance. Noise figure measurements of the active antenna prototype confirm the achievement of ${NF_{min}}$, ranging from 1.9 to 1.4 dB within the 35 to 40 GHz frequency band. Additionally, the receiver system demonstrates a gain of 14.5 dB and a noise figure below 3.6 dB across the operating frequency range. These results validate the effectiveness of the proposed co-design approach in reducing noise while maintaining high gain, making it a promising solution for next-generation millimeter-wave communication and sensing applications.

Active millimeter-wave beamforming arrays and focal plane array antennas require extensive calibration to compensate for impairments, such as phase and gain variations between elements, as well as unintended coupling between changes in gain and phase. When far-field calibration methods are used for calibrating focal plane array antennas, the required size of the anechoic chamber is exceedingly large. For this reason, a near-field calibration method for millimeter-wave analog beamforming array antennas and focal plane array antennas is proposed. Nonidealities of the beamformer integrated circuits with vector modulators are taken into consideration, and a way to reduce the measurement set for vector modulators with high resolution is proposed. This method is both practical and achieves a good calibration as evidenced by measurements of the radiation patterns, and it is suitable for use in an automated factory calibration setup. The important trade-off between the radiated power and side-lobe level is highlighted.

Quantification of uncertainties in the results of channel sounding measurements is important for their interpretation and further usage. In this paper, a novel uncertainty analysis methodology to quantify uncertainties of condensed parameters in measurements of dynamic millimeter-wave channels is presented. The bandwidth limitation and multipath threshold are identified as important impairments. Therefore, the methodology provides three uncertainty metrics for condensed parameters, namely a standard uncertainty to quantify the impact of random variations; a bias due to the multipath threshold; and a total bias including the impact of the bandwidth limitation. These uncertainty metrics are highly channel dependent. Therefore, the proposed methodology creates reference channels, which are representative of corresponding measured channels. Hardware and processing impairments are included in the analysis via a Monte Carlo simulation. This results in a general methodology that can quantify uncertainties in both static and dynamic channel measurements of any wideband channel sounder. The methodology is implemented, verified and demonstrated for the TU/e channel sounder, which exemplifies how it can be used. The proposed methodology can improve the analysis, interpretation and reporting of channel measurement results.

An active transmitarray antenna is presented for Ka-band monopulse tracking radar in the 34 to 36 GHz range. A novel contribution is the application of commercial SiGe-based 5G beamforming chips in a large-scale naval radar array, demonstrating how developments in Ka-band communications can benefit radar technology. Three arrays of 0.77 m diameter each with 24368, 19424 and 7824 radiating elements are presented to compare amplitude-tapered, space-tapered and hybrid-tapered designs. All designs achieve a sub-1° half-power beamwidth (HPBW), peak side-lobe levels (SLL) below –26 dB and effective isotropic radiated power (EIRP) of 100 dBm at broadside with a ±60° grating-lobe-free scanning range. Furthermore, a small-scale demonstrator is realized and presented that consists of an eight-layer printed circuit board with 8×8 patch antennas on one side, and a 4×4 open-ended waveguide feed-array with beamforming chips and integrated liquid cooling channels on the other. After over-the-air calibration, the realized array achieves a peak EIRP of 56 dBm, a 12° HPBW and the ability to scan to ±60° in the H-plane with cos θ scan loss and no grating lobes. E-plane scanning is achieved up to ±45° with cos θ ^1.1 scan loss.

Active integrated antennas (AIAs) are used in low-noise receivers for their good noise performance compared with their nonintegrated counterparts. However, it is challenging to accurately determine one of these antennas’ most important characteristics: the noise figure (NF). To overcome the dependencies of the existing methods, we show a new method that can estimate the NF of a wireless system over-the-air (OTA), using a reverberation chamber (RC). Using the RC, we could create a consistent and repeatable measurement environment. Since this method characterizes the NF of the total system, it also includes factors such as noise matching. An extensive uncertainty analysis shows that the NF can be determined within only 0.7 dB expanded uncertainty in the frequency range from 21 to 29 GHz.