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This article investigates the limits of focal-plane array (FPA) technology by studying a double-reflector antenna system with wide-Angle scan capabilities. The proposed reflector configurations are analyzed in terms of effective isotropic radiated power (EIRP) maximization, minimization of the required total number of array elements for a wide-scan range, and the highest number of simultaneously active array elements of the phased-Array feed. Presented configurations have capabilities to operate in the scan range up to ± 30° in azimuth (±35 beamwidths scan) and ± 3° in elevation. It has been demonstrated how different optimizations could allow to build systems with varying performance in terms of the key operation parameters, such as array size, EIRP, and the number of active array elements. A detailed analysis is provided that demonstrates the potential applicability of this concept in future millimeter-wave (mm-wave) applications.

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.

Conformal array pattern synthesis represents a challenging problem for current state-of-the-art design techniques. To their detriment, these techniques typically suffer from a significant computational burden. A deterministic method for the synthesis of singly curved conformal antenna arrays based on the superformula and the auxiliary array pattern (AAP) formulation is presented. This method, being semianalytical in nature, is able to evaluate the location and excitation coefficients of each radiating element subject to different design constraints in a deterministic manner while utilizing multiple embedded element patterns. Therefore, this method is more computationally efficient than the state-of-the-art alternatives. The proposed synthesis technique has been validated through full-wave electromagnetic simulations and experimental measurements taken on physical demonstrators relevant to different applications within radar and communication systems. The obtained results show accurate agreement between simulations and measurements, requiring only seconds of computation on conventional hardware.

In this work, we present results of a novel mm-wave reverberation chamber, where we discuss the role of the chamber quality factor and chamber decay time, or time constant, for mm-wave applications. For the first time, we analyze the uncertainty due to antenna positioning for these metrics in such a chamber, where we show that the quality factor computed in the frequency domain has a higher uncertainty due to antenna positioning than its time domain counterpart. We describe that the the chamber decay time and quality factor are lower for mm-wave chambers as compared to lower-frequency (sub-6 GHz) chambers, but that they can still function as ideal candidates for metrics revolving around losses.

With 6G around the corner, the push for higher-frequency over-the-air testing of antennas is inevitable, where antenna efficiency is one of the key performance metrics. Reverberation chambers can be an ideal tool for performing antenna-efficiency measurements at mm-Wave frequencies, due to its flexibility in placement, and ability to perform rapid and repeatable measurements. However, to the authors’ best knowledge, no work on antenna efficiency above 47 GHz has been published so far. In this work, we show for the first time results of antenna efficiency using the two-antenna method up to 60 GHz, by using a novel mm-Wave reverberation chamber. We also evaluate chamber loss where we predict that larger systems, such as phased-array systems, can be measured inside this chamber as well, and that the current operational frequency range can be extended much further than 60 GHz for antenna-efficiency measurements.

This paper presents the design of an open-ended waveguide (OEWG) array element operating between 34 GHz and 36 GHz. The OEWG is coupled to a quarter-wave patch antenna on a PCB, which connects to a millimeter-wave IC via a grounded co-planar waveguide. The radiating element is co-designed with an integrated liquid cooling solution to remove heat from the amplifier and phase-shifting IC. Furthermore, a 4x4-element is presented to demonstrate the OEWG design, feed and cooling operation. Although PCB manufacturing deviations were observed in the demonstrator, the realized elements are expected to operate over the entire desired frequency range.

Mode-stirring mechanisms play a critical role in randomizing the fields in a reverberation chamber such that, on average, the chamber provides a uniform field everywhere in the working volume. Recently, a new type of quasi-wall stirring mechanism, the so-called oscillating-wall stirrer was introduced to increase the working volume, without reducing chamber performance. For the first time, we analyze the performance of that stirrer above 1 GHz, for the application of testing antenna efficiency. We investigate this by analyzing the coherence distance of the oscillating-wall stirrer, and the spatial uniformity. We conclude that, for the most stringent threshold, the oscillating-wall stirrer can provide sufficient samples for a single measurement of antenna efficiency above 1 GHz, with uncertainty due to lack of spatial uniformity better than 0.15 dB.

This paper presents an antenna array organized in sub-arrays and composed of densely spaced dielectric-based radiating elements. To reduce the number of active components required in the array beamforming network, each sub-array consists of a single active element, directly fed, and several passive reactively loaded elements. State-of-the-art implementations of such arrays are typically based on rectangular air-filled waveguide radiators which provide a limited bandwidth and support a single linear polarization only. By utilizing the dielectric-based radiators presented in this work, a significant increase in the operating bandwidth of the array can be achieved. In this case, the aforementioned reactive loading is implemented through short-circuited dielectric-filled waveguides. By optimizing the position of the short circuits, the radiation pattern of the sub-array can be controlled and synthesized according to a given mask. To create a larger design flexibility, one can design the sub-array in the presence of the adjacent sub-arrays, so achieving their effective overlapping. By employing the considered design technique, a sub-array featuring flat-top radiation pattern characteristics in combination with low side-lobe levels and high gain was developed, manufactured, and thoroughly analyzed. An additional benefit of such design choice is the possibility of supporting two orthogonal polarizations.

This article reviews the current state-of-the-art of active-integrated antennas co-designed with power amplifiers (PAs). Three strategies to improve output power and power-added efficiency are described using examples, namely direct matching between PA and antenna, tuning of harmonic reflections in the antenna, and in antenna power combining from multiple PAs. An outlook is given on the challenges to be faced in the application of these strategies in wide-scanning phased arrays.

In this work, we analyze for the first time antenna-efficiency measurements of a mm-wave phased-array antenna for smartphone applications by use of the reverberation-chamber-based three-antenna method. We measure the efficiency of the total system (array including an RF beamformer), and we introduce a new method to de-embed radiated emissions by other parts of the system from the efficiency result. We compare the measured result to a simulation model and conclude that the reverberation-chamber approach can yield accurate results when unwanted radiation is properly accounted for.