Tongqing Wang

Size-reduction and band-broadening design technique of uniplanar hybrid ring coupler using phase inverter for M(H)MIC's

The hybrid coupler is one of the most fundamental building blocks in microwave and millimeter-wave systems. Ring topology can be often found in the hybrid microwave integrated-circuit design of narrow and broad-band integrated couplers and mixers. In this paper, we propose a new design theory using a phase inverter for systematic size reduction and band broadening of a uniplanar hybrid ring coupler. The features and design criteria of broad-band reverse-phase hybrid ring couplers are presented. Effective bandwidth of a new reverse-phase hybrid ring coupler can be increased by 28% with a return loss of 20 dB. In addition, we present a class of uniplanar phase inverters and discuss their technical aspects. Experimental results show that the bandwidth of the proposed phase inverter is greater than 1.9 octaves with insertion loss below 1 dB and phase shift error of less than /spl plusmn/20/spl deg/. Measurements confirm that the new uniplanar hybrid ring coupler provides attractive features. Its isolation is better than 20 dB over a 1.8-octave bandwidth attributed to the phase inverter providing almost a frequency-independent phase shift.

A 50:1 bandwidth cost-effective coupler with sliced coaxial cable

A 20 dB 50:1 bandwidth, extremely low-cost coupler with sliced coaxial cable is reported in this paper. The proposed coupler consists of two shaped coaxial cables with adequate sliced linear-tapered cuts and soldered together. It has excellent performance in terms of low VSWR, good isolation, excellent EMI shielding, ultrawide coupling bandwidth, and high power handling capability. Good agreement between measurements and calculations on one hand shows the excellent performance of the coupler, and on the other hand validates the design procedure.

An efficient approach to modeling of quasiplanar structures using the formulation of power conservation in spectral domain

An enhanced spectral domain approach (SDA) is developed for analysis of complex quasi-planar transmission lines. The method is based on a combination of the spectral domain formulation and power conservation theorem. The relationship between electric and magnetic fields is established inside dielectric layers by using the conventional SDA while the characteristic equation related to interface conditions is derived through the power conservation theorem. Maintaining the inherent advantages of the SDA, this technique is able to easily handle more complex quasi-planar structures. Generalized power formulation is also presented to calculate characteristic impedance. Convergence behavior is discussed considering the nature of power conservation. Various finlines with finite thickness of conductors are analyzed to demonstrate its applications. >

Spectral-domain analysis of radiating cylindrical dielectric resonator for wireless communications [WLANs]

A novel class of leaky-mode cylindrical dielectric resonators including mounting holder and radial-step has been recently proposed as a feed structure for omnidirectional antennas that are suitable for wireless communication systems. In this work, a spectral-domain modeling is developed and used for analysis of these composite cylindrical dielectric resonators considering single and double radiating slots. The dielectric resonators are bounded between two parallel conducting plates so that leaky-wave propagation takes place under some electrical and geometrical conditions. Results and discussion are focused on the properties of low-order leaky TM-modes. Influences of various structural parameters on resonant frequency and quality factor of leaky dielectric resonators are presented in detail. A set of experiments are made to verify the proposed theoretical approach.

Experimental study of wideband uniplanar phase inverters for MICs

In this work, a class of novel uniplanar phase inverters are presented for hybrid and monolithic microwave integrated circuits (MICs). An extensive experimental study for characterizing frequency response of insertion loss and phase shift has been made. Measured results show that a CPW phase inverter with slotline transition has more than 2.3:1 bandwidth centered at 3.9 GHz with better than 1 dB insertion loss and 140/spl deg/ phase shift. A compact CPW phase inverter without slotline transition has also been developed that demonstrates better electrical performance than its counterpart with slotline transition. It shows more than 3.1:1 bandwidth centered at 3.5 GHz with better than 10.5 dB insertion loss and 140/spl deg/ phase shift. A new CPW phase inverter with triple strip line transition is proposed. It features more than 2.5:1 bandwidth centered at 6.2 GHz with better than 1 dB insertion loss and 140/spl deg/ phase shift.

A novel leaky-mode cylindrical dielectric resonator used as feeds of omnidirectional antenna for wireless communications

This paper presents a novel leaky-mode cylindrical dielectric resonator including mounting holder and radial-step, which can be used as feeds of a class of omnidirectional antennas suitable for wireless communication systems. An enhanced spectral domain (SDA) approach is extended to determining resonant properties of the proposed resonator. Numerical results are focused on low-order leaky TM-mode properties. The effects of different structural parameters on resonant frequencies and quality factors are studied in detail. Theoretical results are verified by experiments.<<ETX>>

A novel microwave omnidirectional antenna for wireless communications

A novel microwave omnidirectional antenna is proposed in this paper for wireless communications. This antenna is constructed with cavity-restrained multi-stacked dielectric disks. Vertical polarized omnidirectional radiation patterns are obtained from radiative ring slots in the side wall of dielectric-metal cavities operating on TM/sub 01/spl delta// mode. High omnidirectional gain is realized with stacked cavities with multi-radiative slots. Ring slots between the adjacent cavities are used to enhance the excitation of the desired radiating mode in phase, which actually eliminates the feed network. A special technique is adopted for excitation of the antenna from coaxial line, with which very good matching is achieved. This type of antennas could be ideal for the base or center stations for wireless and indoor communications. Experimental results of a prototype of the antennas working at 12.6 GHz is given to demonstrate the great potentials for wireless applications.

Effects of various suspended mounting schemes on mode characteristics of coupled slotlines considering conductor thickness for wideband MIC applications

Propagation characteristics of fundamental and higher-order modes are determined in coupled slotlines with three suspended mounting schemes (pedestal, groove, inverse pedestal) for wideband applications of microwave and millimeter-wave integrated circuits. The analysis is based on a novel enhanced spectral domain approach (ESDA) that combines essentially the conventional spectral domain technique with the power conservation theorem. Numerical results, considering also the influence of finite conductor thickness, are presented for propagation constants and characteristic impedance of the fundamental modes. Effects of different suspended mounting schemes on cutoff frequencies of first higher-order even and odd modes are discussed in detail. Field profiles of the fundamental modes in coupled slotlines with and without pedestals are shown. The inherent mechanism of mode transition is explained with respect to different pedestal sizes, indicating that the monomode bandwidth can be extended by appropriately choosing the dimension of pedestal in coupled slotlines. >

Enhanced spectral domain analysis of coupled slotlines with septum and pedestal considering finite thickness of conductors for wideband MICs

A class of coupled slotline structures with septum and pedestal/groove considering finite thickness of conductors are analyzed for wideband applications of microwave and millimeter wave integrated circuits. The analysis is based on a novel enhanced spectral-domain approach (SDA). Numerical results are presented for propagation constants and characteristic impedances of the fundamental modes. Effects of different structural parameters on cut-off frequencies of first higher-order even- and odd-modes are discussed in detail. The inherent mechanism of these cutoff frequencies of first higher-order modes indicates that the monomode bandwidth can be extended by appropriately choosing the dimension of pedestal in coupled slotlines (CSLs).<<ETX>>

A NOVEL DOMAIN-PARTITIONING APPROACH FOR MODELING ARBITRARILY SHAPED MICROWAVE CIRCUITS

A novel domain-partitioning approach (DPA) is presented for field-the-oretical modeling and for the design of arbitrarily shaped microwave circuit problems. The new technique is derived from a finite-difference strategy with networking interconnections. Simple examples are demonstrated and compared with available results. The advantages of the proposed approach compared to other techniques in the discrete domain are its efficiency and accuracy.