Abstract-In this paper, a compact wideband high-rejection microstrip bandstop filter using two meandered parallel-coupled lines of different electrical lengths and characteristic impedances in shunt is presented. The transmission and reflection zeros of the filter can be controlled through analytical equations and rulers given. Using this signal interferences technology, this filter obtains a low insertion loss and sharp rejection. Bandwidth and rejection level of the filters of this bandstop filter can be designed by choosing different even-and oddmode characteristic impedances values of the coupled lines. According to the transmission zeros number, two types of filters are shown in the paper. To validated this topology, a wideband bandstop filter with a 3 dB cutoff frequency bandwidth of 92% centered at 2.6 GHz with sharp rejection characteristics is built to verify the theoretical prediction. The measured frequency response of the filter agrees excellently with the predicted result.
A new method to design an unequal Wilkinson power divider (UWPD) with a high power-dividing ratio is presented. By employing dual transmission lines, the ratio of highest to lowest characteristic impedance in the UWPD is effectively reduced while maintaining the main frequency response, thus the conventional narrow width in the microstrip can be avoided in practical implementation. For verification, a 5:1 microstrip UWPD operating at 1 GHz has been designed, fabricated and tested. Results show that there is good agreement between calculation and measurement.Introduction: Unequal Wilkinson power dividers (UWPDs) have asymmetric structures, which are more generalised and complicated than equal ones [1]. In general, the main difficulty in designing microstrip extremely UWPDs operating at single band [2] or dual-band [3-7] is the realisation of high characteristic impedance transmission lines. To overcome such practical difficulty for UWPDs, many novel technologies, such as a meander-shaped DGS [8], offset double-sided parallel-strip lines (ODSPSL) [9], grooved substrates [10], and a T-shaped equivalent structure [11], have been developed. However, design and implementation using the DGS, ODSPSL and grooved substrates are not very easy for many engineers, while the transmission line stubs [11] decrease the final operating bandwidth.In this Letter, we propose another novel design method of extremely UWPDs. In this proposed UWPD, equivalent impedance transformers based on dual transmission lines (DTLs), which have been applied to miniaturise the branch-line coupler [12] and improve the isolation of the parallel coupler [13], are used to replace the quarter-wavelength impedance transformers with too low characteristic impedances. Therefore, equivalent structures with DTLs make the ratio of highest to lowest characteristic impedances decrease compared with the conventional one. In particular, the proposed UWPD does not include any reactive components, transmission line stubs and via holes, and can be easily realised on the planar PCB procedure or monolithic microwave integrated circuit (MMIC). In the final microstrip experiment, good agreement between the calculated and measured results can be observed.
A new accurate Volterra-based model is introduced for behavioral modeling and digital predistortion (DPD) of power amplifiers (PAs). This model extends the GMP model with specific cross terms, and these augmented terms significantly increase the model's performance. The proposed model's performance is assessed using a LDMOS Doherty PA driven by two modulated signals (a 4-carrier WCDMA signal and a single carrier 16QAM signal). The experimental results in both behavioral modeling and DPD applications demonstrate that the proposed model outperforms the hybrid memory polynomial-envelope memory polynomial (HME) model and generalized memory polynomial (GMP) model. Compared with the HME model, the proposed model shows an average normalized mean square error (NMSE) improvement of 2.2 dB in the behavioral modeling, average adjacent channel power ratio (ACPR) improvement of 2.8/2.5 dB in the DPD application, and 20% reduction in the number of coefficients. In comparison with the GMP model, the proposed model achieves higher model accuracy and better DPD performance, but reduces approximately 40% of coefficients.
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