Compact surface acoustic wave (SAW) resonator based multi-band bandpass filters (BPFs) with quasi-elliptic transfer functions are reported. They are based on multi-resonant acoustic wave lumped resonator (AWLR) stages that are shaped by multiple one-port type acoustic wave resonators (AWRs) and one lumped-element inductor. The concept can be scaled to transfer functions with: i) a high number of passbands by readily increasing the number of the AWRs in the multi-resonant stage and ii) a higher order by cascading AWLRs using impedance inverters. As such, for N in-series cascaded multi-resonant stages, each comprising K AWRs, K passbands with enhanced fractional bandwidth (FBW) can be created, and the overall transfer function will have $K\bullet(N)$-poles and $N\bullet(K+1)$-transmission zeros (TZs). The operating principles of the multi-band AWLR concept are provided through detailed design examples. For proof-of-concept demonstration purposes, two-stage dual-band (i.e. $N=K=2$) and triple-band ((i.e. $N=2$ and $K=3$) BPF prototypes were designed, manufactured and characterized. They exhibit i) two passbands with $f_{cen1,2}=1033.4$ and 1039.9MHz, FBWs $\gt0.78k_{t}{}^{2}$ and $Q_{\text{effS}}\gt6200$ ii) three passbands with $f_{cen1,2,3}=1029.8,1033.4$ and $1039.9\mathrm{MHz},\mathrm{FBWs}\gt0.48k_{t}^{2}$ and $Q_{effS}\gt5400.\ (k_{t}{}^{2}$ is the AWR’s electromechanical coupling coefficient)
In this paper, we present a hemispherical Fabry-Pérot open cavity resonator based measurement technique to estimate the relative permittivity of dielectric materials. The open cavity is realized by combining a spherical and a planar mirror, suitable for the characterization of both solid and fluid materials in the frequency range from 25 GHz to 42 GHz. The planar mirror is surrounded by a 0.5 mm high metal wall which allows the reflector to be filled with the liquid material to characterize. The measurement method is based on the Gaussian beam theory, which allows extracting the dielectric properties of the material by analyzing the resonant frequency shift of the fundamental mode from, in this case, the reflection coefficient only. This is made possible thanks to the optimized shape of the coupling aperture.
This paper presents a detailed RF design methodology for quasi-elliptic bandpass filter (BPF) with quasi-input reflectionless behaviour in both their passband and stopband regions. The proposed input reflectionless BPF consists of microstrip coupled lines and transmission lines, comprising three sections: a BPF, a transmission zero (TZ) and an input matching sections. A quasi-elliptic transfer function is achieved by generating TZs at lower and upper sides of passband without affecting the passband response or input reflectionless behaviour. The TZs can be located close to the passband for achieving sharper power absorption ratio profiles within the stopband-to-passband transitions. The theoretical foundation and design methodology of the proposed quasi-elliptic input reflectionless BPF are described. To validate the proof-of-concept, a prototype was manufactured and measured at center frequency of 3.5 GHz. The measured results are fair agreement with the EM simulations and theoretically predicated results.
This paper reports for the first time the use of 100VGaN on SiC HEMT devices in a distributed amplifier, and the highest power and efficiency yet achieved is reported. Over 0.5 – 1.5 GHz the power and efficiency are SOW and 50% minimum with typically 90W over most of the band.
This work proposes a small dual-band (2.4 GHz and 4.89 GHz bands) 3D beamforming Multiple-Input Multiple-Output (MIMO) antenna for emerging size-constrained Internet of Things (IoT) applications. The performance is realized via digital beamforming in a structure sized only 51.5 mm in diameter (smaller than half wavelength at 2.4 GHz). At the 2.4 GHz band, the antenna realizes an isolation >30 dB, and the Envelope Correlation Coefficient (ECC) is <0.0003), with a bi-directional beamforming capability in the azimuth plane, and unidirectional beamforming across the elevation plane. At the 4.89 GHz band, the isolation is >19 dB, and the ECC<0.0047, while unidirectional beamforming is achieved in both the azimuth and elevation planes.
