Chien-Hsun Ho

Broad-band uniplanar hybrid-ring and branch-line couplers

Novel uniplanar 180 degrees and 190 degrees hybrids suitable for MIC and MMIC applications are described. The uniplanar crossover hybrid-ring coupler using a coplanar waveguide (CPW) and slotline provides substantially improved amplitude and phase characteristics over a broad bandwidth compared to conventional microstrip hybrid-ring couplers. Experimental results show that the new coupler has a bandwidth of more than one octave from 2 GHz to 4 GHz with a +or-0.4-dB power dividing balance and a +or-1 degrees phase balance. A uniplanar two-branch directional coupler using a coupled rectangular slotline ring has also been developed. CPW-to-slotline transitions using uniform and nonuniform CPWs or slotlines are also discussed. These transitions are uniplanar and simple to fabricate. No via-holes are needed for ground connections, and integration with solid-state devices is easy. A pair of broadband transitions using CPW shorts and slotline radial stubs is demonstrated with a 1-dB bandwidth of more than 5.2:1. >

Wide-band reduced-size uniplanar magic-T, hybrid-ring, and de Ronde's CPW-slot couplers

New reduced-size uniplanar magic-T and hybrid-ring coupler suitable for MICs and MMICs have been developed using a CPW-slotline ring that is 20% smaller than comparable designs. These circuits provide good amplitude and phase characteristics over a broad bandwidth. Experimental results show that the hybrid-ring coupler has a 1.3 octave bandwidth centered at 4 GHz and the magic-T has a bandwidth of 1.6 octave from 2-6 GHz. Both have a maximum power dividing imbalance of 0.4 dB and a 2.5/spl deg/ maximum phase imbalance. Also a new uniplanar de Rondes CPW-slot directional coupler was developed with good performance. The even-odd mode analysis of four-port networks with double symmetry was used to analyze this coupler. A de Rondes coupler with 5 dB coupling was designed and demonstrated over the frequency range of 2.4-3.4 GHz. The measurement results agree with the theoretical design.

Experimental investigations of CPW-slotline transitions for uniplanar microwave integrated circuits

Eight novel coplanar waveguide (CPW) to slotline transitions using uniform and nonuniform CPWs or slotlines are discussed. These transitions are uniplanar and simple to fabricate. No via-holes are needed for ground connections, and integration with solid-state devices is easy. A pair of broadband transitions using CPW shorts and slotline radial stubs is demonstrated with a 1-dB bandwidth of more than 5.2:1.<<ETX>>

Slotline annular ring elements and their applications to resonator, filter and coupler design

A slotline type of annular ring element has been developed as a new circuit component for resonator, filter, and hybrid coupler applications. Various coupling methods were devised for the use of this slotline ring in many applications. A new type of slotline dual-mode filter has been developed with a bandwidth of 12.3% and a stopband attenuation of more than 30 dB at the center frequency of 3.5 GHz. Another slotline type of cross-over hybrid ring coupler which utilized a slotline T-junction and a resistively-coupled slotline ring has also been developed with a bandwidth of more than 80%, an excellent power dividing balance of +or-0.2 dB, and a fairly good isolation of 35 dB. With the ease of adding series and shunt components, the slotline annular ring element should have many applications for MICs and MMICs. >

Slot-coupled double-sided microstrip interconnects and couplers

A broadband slot-coupled microstrip vertical interconnect and a microstrip double-layer quadrature coupler are presented. The interconnect uses virtually terminated microstrip-to-sandwich slotline transitions and demonstrates broad bandwidth, low loss, and high efficiency coupling. The interconnect showed less than 1 dB insertion loss over a bandwidth of more than 2.6 octaves which covered the L, C, and S bands. The microstrip double-layer quadrature coupler, consisting of two parallel microstrip lines coupled by two virtually terminated narrow slots, showed an isolation of greater than 15 dB and a phase quadrature of 90 degrees +or-2.5 degrees over a bandwidth of 14%. Due to the advantages of compact size, light weight, high density, and good isolation, these 3D noncontacting RF couplers are very suitable for multilayer and large-scale MIC (microwave integrated circuit) and MMIC (monolithic microwave integrated circuit) applications.<<ETX>>

Ultra wide band slotline hybrid ring couplers

The design procedure and results for two newly developed hybrid ring couplers using microstrip-coupled slotline rings are presented. The couplers have a wider bandwidth with an excellent power dividing balance and a fairly good isolation compared to the conventional microstrip hybrid ring coupler. The slotline cross-over hybrid ring coupler exhibits greater than 35-dB isolation and a good power dividing balance of +or-0.2 dB over an 80% bandwidth from 1.8 to 4.2 GHz. The experimental results agree very well with the theoretical prediction. With the advantage of allowing easy series or shunt insertion of devices, these couplers are useful in many applications for MICs (microwave ICs) and MMICs (monolithic MICs).<<ETX>>

A broad-band uniplanar slotline hybrid ring coupler with over one octave bandwidth

A novel uniplanar hybrid ring coupler using coplanar waveguide (CPW) and slotline is presented. The coupler provides substantially improved amplitude and phase characteristics over a broad bandwidth compared to the conventional microstrip hybrid ring couplers. Experimental results show that the new coupler has a bandwidth of one octave from 2 GHz to 4 GHz with a +or-0.25-dB power dividing balance and a +or-1 degrees phase balance.<<ETX>>

A new type of waveguide ring cavity for resonator and filter applications

A new type of rectangular waveguide ring cavity has been developed for applications to resonators, filters, and multiplexers. The circuits have advantages of high Q and high power handling capability. H-plane and E-plane waveguide ring cavities have been investigated thoroughly in single-mode and dual-mode operations. For single-mode operation, regular resonant modes, split resonant modes, and forced resonant modes were explained by resonant mode charts of E-field points. Mechanically tuned and electronically tuned resonators built by adjusting the resonant modes between regular resonant modes and forced resonant modes have been demonstrated. For dual-mode operation, a dual-mode filter using a single H-plane ring cavity has been built with a bandwidth of 0.77%, a stopband attenuation of more than 40 dB, and a sharp gain slope transition. Another dual-mode filter which was formed by cascading two E-plane ring cavities has also been fabricated with a bandwidth of 1.12%, a stopband attenuation of 70 dB, a mode purity of 2 GHz at the center frequency of 26.82 GHz, and a sharp gain slope transition. >

Transmission line modeling of CPW-slotline transitions and CPW butterfly filters

This paper presents theoretical analyses of CPW-slotline transitions and CPW butterfly filters using the transmission line models. Accurate modeling of non-uniform CPW and slotline radial stubs was developed using tandem connected uniform lines. Measured results of various transitions and filters agree very well with calculation. Design curves for practical applications are also presented.<<ETX>>

Directional couplers between doubled-sided substrate microstrip lines using virtually-terminated coupling slots

A new planar multilayer quadrature coupler is proposed. This new multilayer coupler consists of two microstrip lines that are coupled through two virtually terminated narrow slots in a common ground plane. Experimental results are in fairly good agreement with theory. With the advantages of compact size and simple design procedure, this new component should have many applications in multilayer microwave integrated circuits.<<ETX>>