Zongxi Tang

Measuring Complex Permeability of Ferromagnetic Thin Films using Microstrip Transmission Method

A transmission method is proposed to measure the complex permeability of ferromagnetic thin films in the frequency range of 100 MHz–18 GHz. The air microstrip is used as measurement fixture; S-parameters are measured by vector network analyzer (VNA). Ferromagnetic thin film samples deposited on silicon substrate with thickness less than 90 nm are measured. Effective permeability is deduced from the s-parameters loaded with and without thin films, and complex permeability of thin films is extracted from the effective permeability. The experimental results show that, using the method proposed in this paper, the complex permeability of thin films can be determined accurately up to 18 GHz.

An Improved Measurement Configuration for Determining the Permeability of Ferromagnetic Thin Film Materials

An improved measurement configuration is proposed to measure the permeability of ferromagnetic thin film materials. For best consideration of the large conductivity of ferromagnetic materials, the thin film is integrated as under layer substrate instead of upper layer substrate in microstrip configuration. Formulations are deduced and support vector regression (SVR) is used to extract the complex permeability of the ferromagnetic thin film materials. The results show that the error for both real part and imaginary part of the permeability (μ′ and μ″) is less than 1%.

Linearity Improved Doherty Power Amplifier Using Coupled-Lines and a Capacitive Load

A Doherty power amplifier, using a pair of coupled lines loaded by a capacitor, is proposed for linearity improvement. The conventional λ/4 transmission line is substituted by capacitor-loaded coupled lines to perform impedance inversion, and to compensate phase delay. At the same time, the proposed structure is also utilized to suppress the second and higher order harmonic of the output of the main amplifier. Furthermore, the phase distortion of the peak amplifier at a high power level can be corrected by tuning capacitor-loaded coupled lines. Compared to a conventional Doherty PA, the third-order intermodulation distortion of the proposed Doherty PA is reduced by 23 dB.

Push-Push Dielectric Resonator Oscillator Using Substrate Integrated Waveguide Power Combiner

A novel Ku-band push-push dielectric resonator oscillator (DRO) using substrate integrated waveguide (SIW) power combiner is presented. Compared with the traditional push-push oscillator, the proposed push-push DRO can realize high fundamental harmonic suppression, due to the use of a SIW power combiner, whose cut-ofi frequency is designed within the range of the fundamental and second harmonic frequency. Moreover, the isolation of two fundamental frequency oscillators can be enhanced, while the power combiner operates at the second harmonic frequency to maximize the output power. As shown in the experimental results, the centre frequency of push-push DRO is 14GHz, with a frequency tuning range of 30MHz. The suppression of the fundamental frequency is 28.59dBc while the third harmonic suppression is 22.54dBc. Furthermore, the phase noise can achieve i98:01dBc/Hz at 100kHz ofiset from the centre frequency.

K-BAND HARMONIC DIELECTRIC RESONATOR OSCILLATOR USING PARALLEL FEEDBACK STRUCTURE

A novel K-band harmonic dielectric resonator oscillator (DRO) is presented. Two identical parallel feedback DROs constitute a symmetric structure by sharing the same dielectric resonator (DR). As a result of this special structure, the odd frequency output components ofiset while the even harmonic frequency components superimposed at the output port. Odd and even mode analysis method is used in theoretical analysis. As the experimental results shown, the fundamental frequency is 9.45GHz and the output power at the second harmonic frequency of 18.9GHz is 9.45dBm. The suppression of fundamental frequency is about 15.5dBc. A phase noise of i97dBc/Hz@100KHz and i78dBc/Hz@10KHz is achieved at the output frequency.

An Improved Method for Permeability Measurement of Magnetic Thin Film

A modified method is proposed in order to improve the measurement accuracy of permeability. Formulations are then deduced and the complex permeability of the magnetic thin film materials is extracted. The results show that the accuracy of complex permeability can be improved remarkably with 1% error for permeability

An unequal broadband power divider using Composite Right/Left-Handed Transmission Lines

A unequal power divider using anti-coupled and Microstrip Metamaterial Lines over a large bandwidth is proposed. The structure comprises anti-coupled power divider, followed by a +90° negative-refractive index (NRI) metamaterial (MM) phase-shifting line along the top branch, and traditional microstrip line along the bottom branch. The structure is used to deliver flexible variation of power division ratio and phase using Composite Right/Left-Handed Transmission Lines (CRLH-TL), besides, anti-coupled power divider to suppress the second harmonic. The proposed power divider exhibits a measured differential output phase 90° ± 5°bandwidth from 1.62 to 2.75GHz, while the output quantities S21 and S31 remain above-4dB from 0.7 to 2.5GHz.

The design of waveguide Slot Taylor circular arrays

Two dimensional arrays formed by arranging a number of linear slotted waveguides side-by-side are presented. Theory, synthesis procedure, and implementation of the two dimensional Taylor Slot Array are demonstrated. The performances of the two dimensional Taylor Slot circular array with 972 slots in the ka-band at the center frequency of 30 GHz are demonstrated. A less than 1.51dB input voltage standing-wave ratio (VSWR) with the band width of 600MHz is achieved. At the center frequency 30 GHz, main beam is 35.48dB with a 25dB sidelobe level of the H-plane and 21.3dB sidelobe level of the E-plane are also achieved.

Tri-band cross-coupling bandpass filter with rectangular defected ground structure array

Abstract A tri-band cross-coupling bandpass filter (BPF) with rectangular defected ground structure (DGS) array is proposed in this paper. Cross-coupling paths comprised of five resonators are employed to achieve general Chebyshev filtering frequency responses. Besides changing gaps among resonators, a novel rectangular DGS array is proposed to exactly meet coupling coefficients for specific demands for different passband in multi-band BPF. The centre frequency of the tri-band filter that is selected at 2.4, 3.4, 5.5 GHz are for LTE, Bluetooth, WiMAX and WLAN. The 3 dB bandwidth of the three passbands are 5, 3.23 and 3.45%, respectively, meanwhile, more transmission zeros are generated, leading to enhanced selectivity and high out of band isolation. The proposed tri-band filter is completed with a few simple calculations and several brief processes. Measured results of the fabricated filter demonstrate the theory prediction and proposed method well.