Jinping Xu

Analyzing wide-band behavior of wire antennas on large platforms with fast PO-MoM Techniques

The physical optics-moment of method (PO-MoM) is an efficient and accurate hybrid technique for EMC analysis of antennas on electrical-large platforms. In this paper, the fast far field approximation (FAFFA) in PO region and the impedance-matrix interpolation method in MoM region are adopted in the traditional PO-MoM algorithm in order to accelerate the analysis of the wide-band behavior of the onboard antennas. Numerical results showed that the proposed fast PO-MoM technique is very efficient in saving CPU time while the required memory units keep approximately unchanged compared to the conventional PO-MoM.

Near-field sparse inverse preconditioning of multilevel fast multipole algorithm for electric field integral equations

Based on the singularity of electric field integral equation (EFIE), a near-field sparse approximate inverse (SAI) preconditioning technique is proposed to improve the convergence property of the Krylov iterative solution of the dense linear systems arising from EFIE. The multilevel fast multipole algorithm (MLFMA) is employed to reduce the computational complexity of the matrix-vector product operations. Sparse patterns are prescribed by taking account of the interactions of nearby pairs of RWG basis functions. Then, the SAI preconditioner is constructed by Frobenius norm minimization method. It is applied to solve the scattering problem of a PEC plate and a sphere. The additional CPU time and memory consumption are approximately in linear proportion to the number of unknowns. The high numerical efficiency of the proposed preconditioning technique combined with GMRES is illustrated.

A third-harmonic mixer using balanced diode configuration at W-band frequencies

This paper reports on the design, fabrication and performance of a third-harmonic fixed-tuned frequency mixer, working at W-band frequencies. The mixing circuit consists of a variation of crossbar structure, a combination of the suspended stripline circuit and the microstrip matching circuit. The mixing diodes are arranged as a single balanced configuration near the end of the RF waveguide. The precise RF grounding is provided by the grounding via holes close to the diodes. For a fixed IF frequency of 2.0GHz, the mixer has a measured conversion loss (CL) of 12.5 ±1.5 dB over both the frequency range of 80-83GHz and 91-97GHz. Furthermore, the mixer exhibits wide-band CL characteristics of better than 18.0dB over 75-83GHz and 88-98GHz. The achieved LO-to-IF isolation is better than 30dB. This mixer design offers an effective and low-cost alternative solution for W-band receivers.

Design of a hermetically-sealed ka-band LNA module with high reliability

This paper presents the design and test of a hermetically-sealed low noise amplifier (LNA) module at Ka-band, in which the reliability is fully considered for its application in critical environment. An overall design scheme is worked out for the project-oriented LNA module. It consists of two LNA MMICs, a waveguide-to-microstrip transition, three fixed value attenuator chips and an amplitude equalizer which is fabricated by using hybrid microwave integrated circuit (HMIC). A waveguide-to-microstrip transition with a hermetic coaxial bead is designed and applied to form the hermetic housing of the RF devices and circuits. The LNA module is fabricated, tested and measured. The robustness of the LNA chips, passive components as well as the effect of the assembling technique have been tested out under a temperature shock process with temperatures being -40 o°C to +70°C. The measured noise figure of the LNA is 2.4 ± 0.02dB including the insertion loss of 0.4dB of the waveguide-to-microstrip transition. Measured linear gain of is 37.8±0.3dB over the a testing bandwidth of 2GHz at room temperature. The recorded gain variation is within ±0.9dB over the temperature range of -40°C to +50°C.

Design of a G-band frequency doubler based on a pair of parallelly mounted dual-diode chips

This paper presents the design and preliminary test results of a 166-188GHz frequency doubler using two flip-chip dual Schottky diode chips. The purpose of this work is to explore the feasibility of a simple and compact HMIC circuitry for frequency doubling with a higher power handling capability in this band. The designed doubler module consists of a pair of parallelly mounted Schottky dual-diode chips, two E-plane probes located in the input and output waveguide, a BPF for fundamental wave trasmission, two CMRC LPFs for DC biasing as well as impedance matching circuits at both driving and output port of the chip pair. The douber features four Schottky anodes closely located at a very compact region, being no need for additional power dividing and combining circuit. Preliminary measurement has been done on the fabricated doubler. It delivers an output power of 0.5±2.5dBm across the band of 166-188GHz with an input driving power of about 17dBm at W-band. The measured output power has a monotonously increasing tendency with respect to the input power, which demonstrates its potential of providing more output power at G-band if driving source with higher power level is applied.

Scattering at rectangular waveguide to quasi-optical cavity junction

A formally exact solution is given for the problem of scattering at the junction of rectangular waveguide to quasi-optical cavity by mode matching method. The normal TE and TM modes are utilized to expand fields in rectangular waveguide. Gaussian beam modes are employed to express fields in quasi-optical cavity. By applying the boundary condition of the transverse electric and magnetic fields at the interface between the two regions, a matrix equation for the amplitude of each mode is established. Generalized scattering matrix [S] can be readily deduced from the matrix equation. Numerical results of the S-parameter for the dominant TE/sub 10/ mode in rectangular waveguide are calculated. The results are graphically compared with those obtained by a hybrid technique of finite element method and Gaussian mode expansion method.

A balanced reflection type HMIC vector modulator over 34–36GHz based on cold state pHEMTs

A vector modulatorat Ka band consisting of two balanced I/Q bi-phase attenuatorsis presented in this paper. The bi-phase attenuators are of reflection type, in which cold state pHEMTs are employed as tunable impedance loads. Due to the balanced structure, parasitic effects of the pHEMTs are effectively cancelled. A prototype of the vector modulator is fabricated by HMIC technique. The measured dynamic range of amplitude is about 28dB with 360 degree tunable phase. The maximum transmission coefficient is about -8dB while the return loss is better than 15dB at the whole operation band of 34-36GHz.

A wideband Ka-band receiver with high gain flatness and slight group delay fluctuation

We report on the design consideration and experimental results of a wideband Ka-band heterodyne receiver with high gain flatness and slight group delay fluctuation. Flat gain performance is achieved by applying amplitude equalizers both in RF circuits and IF circuits. Small group delay fluctuation is fulfilled by making a trade-off between out-of-band rejection and group delay when designing the RF and IF BPFs. The measured results demonstrate that the receiver has a gain flatness less than ±0.5dB at a conversion gain of 55dB and a slight group delay fluctuation less than 2ns.

Phase noise analysis of fractional-N PLL based frequency ramp generator for FMCW radar

The phase noise of a fractional-N PLL based frequency ramp generator is investigated to understand how phase noise performance is affected by ramp slope and loop gain of PLL. The steady state phase error of the PLL is analyzed by utilizing a linear time-invariant continuous-time model (CTM). The relationship between phase error and phase noise spectrum during frequency ramp is deduced. A 24GHz FMCW signal source is designed and fabricated using commercial ICs to verify the theoretical analysis. It is deduced from theoretical analysis and experimental results that the phase noise spectrum of a frequency ramp signal can be reduced by using a large CP current and a low ramp slope.

A compact bandwidth controllable BPF using fish-like taijitu shaped resonators

The fish-like Taijitu pattern is a Chinese symbol for the concept of opposites existing in harmony. In this letter, a compact band-pass filter (BPF) using half fish-like taijitu shaped resonators is proposed. Compared to the square open loop resonator, the self-capacitance of the proposed resonator is increased, which is well suited for the design of narrow band BPFs. Furthermore, its bandwidth is easily controlled by rotating the taijitu pattern to obtain the required Q factor due to its skew-symmetric structure. Three prototypes of the BPFs working around 12GHz with different bandwidths are designed, fabricated and measured. The relative 3dB bandwidths of these filters are approximately 15.8%, 10.2% and 4.5% respectively. The simulated results and the measured results agree well with each other.