Hybrid‐cascade coupled‐line phasers for high‐resolution radio‐analog signal processing

Abstract

A hybrid-cascade (HC) coupled-line phaser configuration is presented to synthesize enhanced group delay responses for high-resolution RadioAnalog Signal Processing (R-ASP). Using exact analytical transfer functions, the superiority of HC coupled-line phasers over conventional transversally cascaded C-section phasers is demonstrated and verified using full-wave simulations.Introduction: Radio-Analog Signal Processing (R-ASP) is defined as the real-time manipulation of signals in their analog form to realize specific operations enabling microwave or millimeter-wave and terahertz applications ASP. The heart of an R-ASP system is a phaser, which is a component exhibiting a specified frequency-dependent group-delay response within a given frequency range. Such phasers have found useful applications in the domain of instrumentation, security, short-range communication and RADAR systems, to name a few [1].A common requirement in high-resolution R-ASP is to achieve high dispersion in phasers, in order to provide large frequency discrimination in the time-domain [2]. This translates into the requirement to achieve a large group delay swing in the phaser within the desired bandwidth. Recently, a coupled-line phaser based on composite right/left-handed (CRLH) transmission lines was proposed utilizing its tight coupling property to achieve this goal [2]. However, considering its design complexity, multilayer configuration and fabrication sensitivity, a new configuration based on hybrid-cascaded (HC) coupled-lines was proposed in [3]. This configuration exploits the fact that the required coupling level can be relaxed by folding the conventional C-section into a cross-shaped structure, where superior effective backward coupling results from the discontinuities introduced by the arms of the cross. Consequently, tight coupling coefficients are achieved using different coupled-line sections of relatively small coupling values [4]. This paper demonstrates the advantage of using HC coupled-line phasers over regular cascaded C-section phasers in group delay engineering via both analytical and full-wave simulation results.

Dispersive delay lines using microstrip technology

“…As a result, non‐dispersive transmission of signals is the main focus in electromagnetic communications. Owing to the possible applications in analogous signal processing, some studies investigated dispersive transmission media [1–11]. However, the low frequency‐sensitivity delay time of these dispersive structures could limit the potential applications in various aspects.…”

“…[3–10] used C‐section coupled lines and composite right‐/left‐handed (CRLH) structures to control group delay profile. The advantages of the methods [3–10] are two‐fold: they result in broadband responses and they lead to size‐bandwidth independence. However, insertion loss, circuit size and complexity of implementation could be concerned due to its small frequency‐sensitivity dispersion per unit cell.…”

Generalized Coupled-Line All-Pass Phasers

“…The corresponding coupled-line phaser is called a Hybrid-cascaded (HC) coupledline phaser. The HC coupled-line phaser was first introduced in [27] and later used in group delay engineering in [28]. This set of three cascading configurations, LC, TC and HC, represent the fundamental cascading schemes upon which more complex phasers can be constructed, leading to vast variety of coupled-line all-pass phasers with rich and exotic dispersion characteristics.…”