Chi-Hui Lai

Novel Dual-Band Decoupling Network for Two-Element Closely Spaced Array Using Synthesized Microstrip Lines

We investigate an innovative decoupling network for dual-band two-element closely spaced arrays in MIMO applications. The new architecture, combining the reactive element decoupling technique and the eigenmode feed network, provides dual-band decoupling with good radiation characteristics and power balance between the modes. The core block of the decoupling network is a dual-mode 180-degree hybrid coupler; it functions as a conventional coupler in one frequency band but can be equivalent to a pair of isolated direct-thru transmission lines in the other band. This unusual dual-mode coupler is realized by synthesized microstrip lines (cells), consisting of line inductors, parallel-plate capacitors, and series LC tanks. A set of design equations, providing a systematic synthesis procedure of the unit cells, is discussed. The scheme of the dual-band decoupling network is illustrated first, followed by the details of the building circuit blocks; the experimental results and discussion are given at the end of the paper.

Miniaturized Distributed Marchand Balun Using Coupled Synthesized CPWs

A miniaturized distributed Marchand balun, composed of two unequal sections of coupled slow-wave synthesized coplanar waveguides, is developed in this letter. With the even odd mode analysis, the propagation characteristics of the coupled synthesized lines are analyzed. A simple phase compensation scheme, with unequal coupling sections, is proposed to compensate for the phase imbalance due to the non-zero connection line between the coupled-line sections. Without the need of surface-mounted capacitors, the proposed balun provides a comparable miniaturization capability but wider bandwidth when compared with its lumped-distributed counterparts. The circuit topology, design consideration, and simulated and experimental results are discussed thoroughly.

Tri-Mode Heterogeneous Integrated Beam-Switching/Van Atta/Phase-Conjugating Array Using Synthesized Transmission Lines

With the aid of tri-operational mode synthesized transmission lines, an innovative heterogeneous integrated phased array having the functions of beam-switching and retrodirection in three individual bands is proposed and demonstrated. The key innovation is the array feeding network, capable of automatically reconfiguring its topology into three states without applying any active switch. In the low band, the feeding circuit, and hence, the entire system function as a beam-switching array using the Butler matrix for communication and positioning. In the mid and high bands, the integrated array rearranges its feeding network into pairs of isolated delay lines and becomes a Van Atta array and a phase-conjugating array, respectively, to re-radiate the signals to the direction of arrival. The core building blocks are the three-channel selector, tri-mode coupler, and diplexer, all realized by synthesized transmission lines with rigorous design formulae. The operational principle is first introduced, followed by the design and implementation of the key components. A phase compensation scheme is discussed to complete the tri-mode array design. This unique concept is experimentally verified using the radiation characteristics of the integrated array at the end of this paper.

Miniaturized Coupled-Line Couplers Using Uniplanar Synthesized Coplanar Waveguides

A novel slow-wave synthesized coplanar waveguide (CPW), namely, the uniplanar synthesized CPW, is investigated in this paper. Quasi-lumped CPW inductors and capacitors are used in synthesizing the new slow-wave structure. The synthesis method, lumped equivalent-circuit model, and simulated and experimental results are discussed. The synthesized line, featuring excellent miniaturization capabilities, has a moderate quality factor. The slow wave factor is 7.5, while the unloaded quality factor is 30-60. By utilizing the synthesized CPW, three novel miniaturized coupled-line directional couplers are proposed and experimentally verified. With the help of even/odd-mode analysis, design charts are summarized for understanding of the developed miniaturized couplers. When compared with previous designs, the miniaturized couplers show comparable performance, but significantly reduced sizes. Additionally, they have quasi-square appearances, which are suitable for circuit integration in cascade connection.

A Miniaturized Dual-Mode Ring Bandpass Filter

A novel miniaturized dual-mode ring bandpass filter is proposed in this letter. The miniaturization is accomplished by slow-wave synthesized microstrip lines in an asymmetrical form. At the input/output ports, two saw-toothed coupling structures with quarter-wavelength open-circuited stubs are used to provide tight coupling. The miniaturized filter features a very compact size and the in-band responses are comparable to its conventional counterpart. The design methodology, circuit topology, and simulated and measured results are investigated and compared.

Microwave Three-Channel Selector Using Tri-Mode Synthesized Transmission Lines

A microwave three-channel selector, showing twofold symmetry using tri-operational mode synthesized transmission lines, is proposed and investigated in this paper. On one hand, just like a typical triplexer, the three-channel selector provides independent transmission paths at three different frequencies; however, on the other hand, the twofold symmetry makes each of the ports able to serve as the common input. The arrangement of the proposed channel selector is unique and can be applied to synthesize a tri-mode heterogeneous integrated beam-switching/Van Atta/phase-conjugating array. The operational principle is introduced first, followed by the details of the synthesized lines as the core building blocks; design formulas are discussed along with the results. Experimental validation verifies the design concept, and discussions on its potential applications are provided.

On-Chip Miniaturized Diplexer Using Jointed Dual-Mode Right-/Left-Handed Synthesized Coplanar Waveguides on GIPD Process

A new on-chip miniaturized diplexer, implemented on glass-based integrated passive device (GIPD) process using dual-mode right- and left-handed synthesized coplanar waveguides (CPWs), is proposed and validated. The right-handed synthesized CPW is identical to a 50-Ω line in the low band but resembles an open circuit in the high band. The left-handed one, on the contrary, serves as an open circuit in the low band but becomes equivalent to a 50-Ω line in the high band. This unique property makes the proposed design require no extra matching section. The on-chip diplexer shows a very compact size of 0.0174 × 0.0171 λg2, along with low power dissipation (0.6-0.8 dB) and moderate operating bandwidth (11-19%) at 2.6/5.8 GHz.

On-Chip Miniaturized Triplexer Using Lumped Networks With Dual Resonators on an Integrated Passive Device Process

By utilizing lumped coplanar waveguide elements, an on-chip miniaturized triplexer on glass-based integrated passive device (GIPD) process is investigated. Each transmission channel is composed of two parallel LC resonators and an appended L-section network connected in cascade. While the resonators making the path resemble an open circuit at designated frequencies (transmission zeroes), the appended L-section helps create a 50- Ω transmission channel in the third band. In light of this unique approach, the proposed triplexer requires no matching section and features an extremely compact size. According to the experimental results, this on-chip triplexer, while still keeping good in-band/out-of-band performance, is less than one-third the size of the second smallest one in the literature.

Novel uniplanar synthesized coplanar waveguide and the application to miniaturized rat-race coupler

By utilizing quasi-lumped components, we propose a novel slow-wave uniplanar synthesized coplanar waveguide (USCPW) in this paper. The physical length of a 90-degree uniplanar synthesized coplanar waveguide (USCPW) is less than one-twentieth of a guided wavelength. A lumped equivalent circuit model is proposed to explain the complicated behavior of the synthesized line. The design concept, propagation characteristics, equivalent circuit model, and simulated and measured results are carefully studied. Based on the new synthesized coplanar waveguide, a novel miniaturized rat-race coupler is demonstrated. The proposed design is merely 7.2% the size of a conventional coupler, which is the smallest one ever reported in coplanar waveguide form using printed circuit board technology. The response of the miniaturized coupler is experimentally verified in this paper.

Novel synthesized microstrip line with quasi-elliptic response for harmonic suppressions

A novel synthesized microstrip line with quasi-elliptic response is proposed in this paper. By utilizing quasi-lumped elements, the proposed synthesized lines are capable of reducing the circuit size with good slow-wave property. Benefitted from the quasi-elliptic response, signal suppression capability is introduced to the synthesized line at the harmonic frequencies. The design concept, circuit geometry, equivalent lumped circuit model, and simulated and measured results are carefully investigated and discussed. Based on the new synthesized microstrip line, a miniaturized quadrature hybrid coupler with harmonic suppressions is designed as a demonstrated example. The signal rejection levels are higher than 20 and 40 dB at the second and third harmonics, respectively. At the mean time, the size reduction percentage is 50%.