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This paper conducts a validation of two linearization approaches that utilize baseband nonlinear linearization signals of the 2nd order, through practical experiments on an asymmetrical two-way microstrip Doherty amplifier (ADA), and simulations on a symmetrical two-way Doherty amplifier (DA) as well as the single stage power amplifier (PA) for the post-OFDM 5G modulation formats. In the first approach, linearization signals are led at the input and output of the carrier transistor in the DA, while in the second approach, they are injected at the outputs of both the carrier and peaking amplifiers. The DA was tested in simulation for the FBMC signal of 20 MHz bandwidth, while the experimental measurements were performed for the FBMC signal on the ADA for different useful signal frequency bandwidths, 5 MHz, 7.5 MHz, and 10 MHz. The maximal improvement of DA linearity obtained in simulation is 10 dB for lower power and 5 dB for maximum amplifier output power, while the second approach gives around 2 dB better results for higher power levels. The experimental test for ADA performed for considered signal bandwidths indicates 3 dB to 5 dB linearity improvement for the implemented approaches and more symmetrical results achieved by the second approach. Additionally, the simulation tests for the PA were carried out for the FBMC, UFMC, and FOFDM signals of 100 MHz bandwidth, with the application of the first linearization approach. The minimal achieved linearization improvement is 13 dB for the FOFDM signal and a maximal of 18 dB for the FBMC signal. [ABSTRACT FROM AUTHOR]

Introduction/purpose: This paper presents initial development of the procedure for electric field estimation in the vicinity of 5G base stations. Methods: The procedure allows determination of future radiation levels before traffic is established over applied antenna systems on the basis of measured values of electric field levels caused by the signal forming Synchronization Signal Block. It is possible to perform necessary calculations for a very accurate estimation even if some important parameters of the radiation characteristics (such as the frequency span between the frequency carriers on the radio interface) are not a priori known. In this way, communication with mobile system operators before measurement is significantly simplified because operators do not need to know system technical details. Results: The developed formula for electric field estimation is verified comparing the calculated values by its implementation to the practical results obtained by intensive measurements on a great number of 5G base stations in a highly developed country. The formula gives a pessimistic result, i.e. a higher electric field level than it is obtained by all such performed measurements. Conclusion: This estimation allows mobile system operators to predict whether the electromagnetic field around base stations could be dangerous for human health when systems come to full operation while considering national and international recommendations dealing with radiation levels. [ABSTRACT FROM AUTHOR]

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This paper presents an optimization-based approach to the design of asymmetrical filter structures having the maximum number of return--or insertion-loss ripples in the passband such as those based upon Chebyshev function prototypes. The proposed approach has the following advantages over the general purpose optimization techniques adopted previously such as: less frequency sampling is required, optimization is carried out with respect to the Chebyshev (or minimax) criterion, the problem of local minima does not arise, and optimization is usually only required for the passband. When implemented around an accurate circuit simulation, the method can be used to include all the effects of discontinuities, junctions, fringing, etc. to reduce the amount of tuning required in the final filter. The design of asymmetrical ridged-waveguide bandpass filters is considered as an example. Measurements on a fabricated filter confirm the accuracy of the design procedure. Index Terms--Bandpass filters, computer optimization, rectangular waveguide, ridged waveguide, waveguide filters.

A computer-aided synthesis technique for E-plane bandpass filters with improved stopband performance is developed. An optimization procedure based on equal ripple optimization is adopted. The design of a symmetrical E-plane bandpass filter with improved stopband performance is considered; higher order mode interaction between E-plane discontinuities is included in the design. The predicted filter performance shows improved stopband performance and reduced filter dimensions compared with conventional E-plane bandpass filters. The validity of the method is confirmed by the measurement of a fabricated five resonator E-plane bandpass filter with improved stopband performance.

This paper presents novel ultracompact waveguide bandpass filters that exhibit pseudoelliptic responses with the ability to place transmission zeros on both sides of the passband to form sharp rolloffs. The filters contain E -plane extracted pole sections (EPSs) cascaded with cross-coupled filtering blocks. Compactness is achieved by the use of evanescent mode sections and closer arranged resonators modified to shrink in size. The filters containing nonresonating nodes are designed by means of the generalized coupling coefficients’ extraction procedure for the cross-coupled filtering blocks and EPSs. We illustrate the performance of the proposed structures through the design examples of third- and fourth-order filters with center frequencies of 9.2 and 10 GHz, respectively. The sizes of the proposed structures suitable for fabricating using the low-cost {E} -plane waveguide technology are 38% smaller than ones of the {E}$ -plane extracted pole filter of the same order. [ABSTRACT FROM AUTHOR]