A High Slow-Wave Factor Microstrip Structure With Simple Design Formulas and Its Application to Microwave Circuit Design

Abstract

This paper proposes a new microstrip slow-wave structure. The unit cell comprises a Schiffman section of meander line and a shunt open-circuited stub. No via-holes and ground-plane patterns are required. Simple design formulas can be used to obtain line parameters, such as the characteristic impedance and phase velocity. According to the analysis, the characteristic impedance and slow-wave factor of the proposed slow-wave line can be independently controlled by merely two layout parameters. The proposed uniplanar structure only requires a single-layer substrate and is simply constructed using the conventional printed circuit board manufacturing process. A branch-line and a rat-race coupler were designed and fabricated using the proposed structure to demonstrate its feasibility. Their sizes are only 8.49% and 4.87% of the conventional ones, respectively. This novel slow-wave structure should find wide applications in compact microwave circuits.

Nonlinear analysis of oscillators based on a slow-wave structure for phase-noise reduction

“…USE OF A SLOW-WAVE STRUCTURE Slow-wave structures enable a long delay in a compact size. The one considered has a unit cell made up of an open-ended stub and a Schiffman section [9] [Fig. 1(d)].…”

Oscillators Based on Step-Impedance and Slow Wave Transmission Lines for Sensing Applications

“…Using a passive structure with a high frequency selectivity, the oscillator will both exhibit a low phase noise and be able to track the variation of the structure resonance frequency with the MUT dielectric constant. Thus, this work extends [13] with the investigation of the possible use of oscillators based on step-impedance transmission lines [6]- [7] or on slow-wave structures [8]- [9], [14]- [18] to implement lowcost dielectric sensors. Emphasis will be placed on the standalone oscillator operation since, as stated, frequency and amplitude detection methods have been established in the literature.…”

“…On the other hand, the derivatives of  i in (18) with respect to  mut and  are calculated from (4) in a straightforward manner. Replacing (19) and those derivatives in (18), one obtains: TMTT-2022-07-0982.R1  …”

“…The slow-wave structures exhibit a high group delay, enabling a high-quality factor in a compact size [16]- [18]. This is obtained by increasing the effective capacitance and/or inductance of the line, which can be achieved through different strategies [16]- [18].…”

“…The dielectric covers at least a part of these structures and very good results are obtained in transmission mode, for slow-wave structures [8]- [9], and reflection mode, for open-ended step impedance lines [6]- [7]. On the other hand, the work [13] presents a detailed analysis of oscillators containing a slowwave structure [14]- [18], which enables a low phase-noise spectral density. In fact, oscillator-based sensors [19]- [29] have the advantage of a self-sustained operation, in which the MUT variations give rise to a change in the oscillation amplitude and frequency [21]- [22], easily measured with the aid of amplitude or frequency detection interfaces; for instance, frequency variations can be detected from the control voltage of a synthesizer and amplitude variations by means of a power detector or through the control voltage of a feedback loop [10], [21], [25]- [28].…”