A novel structure is proposed to feed a patch antenna. This structure has filter characteristics that affect the matching properties of the antenna. The aim of this antenna structure is to relax the specifications of the antenna filters in future massive MIMO (mMIMO) communication systems. Simulation and measurement results are shown to quantify improved performance characteristics and validate the concept.

A compact coaxial SIW resonator and filter in multi-layer LTCC technology with Green Tape Dupont material is developed. Compact resonators with strong coupling to implement narrow- and moderate- bandwidth filters are proposed. High-order filters have been designed, implemented and tested with excellent results. An insertion loss of less than 0.4 dB (measured Q-factor > 400) for a 3-pole filter and 0.52 dB (0.56 dB connectorized, measured Q-factor > 440) for a 4-pole filter is demonstrated. The fractional bandwidth of the 4 pole filter is almost 262 MHz @ 3 GHz and 8.8%.

Driven by spectrum scarcity and pressures to reduce costs, the complexity of the wireless environment is continuously growing. The need for flexible radio systems that enable efficient spectrum utilization is becoming increasingly urgent to optimize the use of spectrum and telecommunication infrastructure [1]–[9]. In cellular systems, the requirement for agile RF front ends is driven by the evolution of standardization and associated spectrum and channel allocations. The evolution from 4G to 5G and beyond is marked by increased spectrum allocation to these systems both in the sub-6-GHz (FR1) and millimeter-wave (FR2) ranges and a multiplicity of frequency bands of operation. Underpinning cellular infrastructure that can serve a number of frequency bands utilizing common hardware therefore delivers operational and commercial advantages.

This work presents a compact (~25.3 – 34.0°) mechanically reconfigurable filter capable of wide tuning range (~30%) maintaining a stable fractional bandwidth. A common single tuning mechanism simplifies the design. The proposed technology is low-cost and implemented with low complexity. The filter maintains high Q factor across the range. Two distinct designs demonstrate the ability to implement this technology for narrow-band as well as wide-band designs. Experimental results are reported on several prototype filters. This solution augments the current state-of-the-art for narrow and moderate bandwidth adjustable filters.

This work presents the design of two 64-element phased array antennas for 5G access, operating at 28 GHz and at 39 GHz frequency bands. The 8x8-element antenna arrays use a multi-layer printed circuit board stack. 16 commercial quad-core TX/RX ICs are used to provide independent control of phase and amplitude for each radiating element. RF power distribution and combining network is integrated on the PCB, with a single RF interface to an external radio transceiver. Analysis and design of the feed network for the antenna elements is demonstrated.

This paper proposes a novel double ground plane coaxial resonator that allows to realize two independent coaxial cavity modes in reduced physical volume. This configuration of compact high performance filters is an enabler for multiband transmitter architectures using modern radio frequency data convertors. The proposed approach benefits from simple design and design flexibility. The benefit of the proposed approach is the ease of design and the design flexibility. The proposed filters provide the ability to control the frequency, the bandwidth, and the introduction of transmission zeros separately for each band. A number of designs are presented to demonstrate the operation principle and the performance characteristics of the proposed filters. A 2x4 pole filter has been manufactured and tested with very good obtained results.

This paper presents a new dual-frequency coaxial cavity resonator and its potential in the implementation of a new class of four port filters that provide cost and volume efficient solutions for emerging multiband base transceiver stations (BTS). The proposed concept delivers in a single physical structure two virtually independent bandpass filters without significant sacrifices in design or manufacturing complexity as well as performance. This is achieved by introducing within a single cavity two coaxial stubs for two independent frequency bands. Experimental results on a fabricated prototype demonstrate the validity of the concept and the potential of its implementation.

In this paper we present a concentric, multiple resonant elements realization of a distributed filter. The proposed filter has 3 poles and is designed to operate at a frequency of 1.8 GHz with an absolute bandwidth of 40 MHz, equivalent to 2.22 %. Each resonant chamber of the presented filter consists of 25 individual resonant elements arranged in an interdigitated fashion along the circumference of three concentric rings. The resonator occupies a volume of 40 × 40 × 5 mm 3 and has an unloaded quality factor of over 1800. The internal height of the filter (5 mm or 10.8°) is lowest reported in the literature. The measurements of the filter are in an excellent agreement with simulations - the measured insertion loss is 0.44 dB, while the theoretically predicted value stands at 0.37 dB.

A new class of coaxial cavity filters with low-profile suitable for base transceiver station applications is proposed. The benefits of the technology are volume reduction, high performance, and superior spurious-free response. An equivalent lumped element circuit allows for a fast and efficient initial design of the resonators. Full-wave optimization is required to produce the final configuration of the filters. Experimental results demonstrate the high performance of the proposed filters. The electrical length of the experimental resonators is as low as $\lambda _{0}/16$ . The measured insertion loss of the five-pole filter is 0.92 dB at 722 MHz. Experimental results show a spurious-free response of the order of 7.6 times.

In this paper we demonstrate the use of low-loss dielectric powders in the design and fabrication of RF filters. Initially, several different powders are tested for their RF performance — in particular their relative dielectric permittivity and loss tangent. Then, based on the information obtained in this way, the best performance powder is used to design a 5-pole Chebyshev filter operating at a centre frequency of 779 MHz, with a bandwidth of 17 MHz. Upon fabrication of the filter housing, the filter cavities are filled with the powder. Compaction of the powders is achieved in a systematic way and has resulted in stable performance.

In this paper we present a highly compact and low-cost antenna solution based on a dielectric lens and a waveguide horn array feed for operation in the 57–64 GHz frequency band. The antenna is targeted for applications in point-to-point backhaul systems for Small Cell mobile access networks and features a beamforming capability providing self-alignment for ease of installation and improved link stability.

A new topology for E-plane filters compatible with the traditional low-cost single metal insert in a split-block housing is proposed. Improved out-of-band rejection is achieved by virtue of the transmission zeros. The overall length of the input and output resonators is reduced by ~45%, resulting in saving the length of a resonator. A synthesis procedure is outlined. A 4pole filter is demonstrated that implements 2 out-of-band TZs. The technique is well suited to be combined with an extracted pole technique further improving the out-of-band characteristics of the filters. The same 4pole filter is then adopted to accommodate for extra 4 TZs by means of extraction. The simulated loss of the two 4 pole filter presented is 0.22 dB and 0.24 dB, respectively.

A technique to improve the spurious performance of coaxial cavity filters is investigated. It involves incorporating elements/posts resonant at spurious frequencies within the coaxial input/output cavites. To perform suppression and control of harmonic outputs, the spurious elements are coupled directly to the excitation posts and prevent the excitation of harmonics at the fundamental elements. The spurious elements are physically significantly smaller than the fundamental elements that perform the basic filtering function (fundamental frequency); thus they impose only minimized degradation to the ohmic loss of the devices and miniscule additional design effort. Design guidelines of the proposed filters are given. Obtained results demonstrate significant improvement in the spurious performance, and experimental results verify the concept.

This contribution presents numerical and experimental results on a 2 nd order UHF filter prototype that exploits helical resonators with modulated radius. Earlier works have proposed this geometry as means to enhance power handling without significantly compromising on unloaded quality factors. Here we present a detailed prototype design and evaluate its performance at low and high power levels using both rigorous numerical tools as well as the results of an experimental test campaign. Low power results include CST predictions against measurements on a Vector Network Analyser. High power results include predictions from the tool SPARK3D as well as the outcome of a test campaign at the ESA-VSC laboratories. Despite some discrepancies in the power handling predictions, which are largely attributed to uncertainties associated with prototyping, the presented results indicate that there is margin for significant performance improvement by adopting the large gap approach for this class of filters.