Low Signal-Attenuation Negative Group-Delay Network Topologies Using Coupled Lines

Abstract

This paper presents the design and analysis of novel topologies of reflective-type negative-group-delay (NGD) networks with very small signal attenuation (SA). The proposed topologies are based on short-circuited coupled lines. Theoretical analysis shows that predefined group-delay (GD) time with very small SA can be obtained due to the high characteristic impedance of a coupled line and the small coupling coefficient. Due to the very low SA characteristics of the proposed networks, the burden of compensating general-purpose gain amplifiers can be reduced and provide stable operations while integrated to RF systems. This paper also analyses performance degradation of the GD time and SA of the proposed NGD networks according to the temperature-dependent resistance variation. For an experimental validation of the proposed topologies, distributed microstrip line NGD networks (type-I and type-II) are designed, simulated, and measured for a wideband code division multiple access (WCDMA) downlink frequency operating at a center frequency of 2.14 GHz. These results show a GD time of 7.27 ns with an SA of 7.43 dB for the type-I NGD network, and 6.3 and 9.23 dB for the type II-NGD network at the center frequency, and agree closely with the simulations. To enhance the NGD bandwidth, two NGD networks with slightly different center frequencies are connected in parallel, which provides wider bandwidth than the single stage case and shows practical applicability.Index Terms-Coupled lines, distributed transmission line, high characteristic impedance, low signal attenuation (SA), wideband code division multiple access (WCDMA).

Negative Group Delay Phenomenon Analysis Using Finite Unloaded Quality Factor Resonators

“…To overcome the limited availability problem of lumped elements in a microwave regime, the NGD circuits have been designed using distributed transmission line resonators along with the resistor (R) because NGD cannot be exhibited without R [17][18][19][20][21][22]. Moreover, the conventional NGD circuits suffer from several disadvantages such as high signal attenuation (SA), small NGD bandwidth and magnitude (S 21 ) flatness.…”

“…Moreover, the conventional NGD circuits suffer from several disadvantages such as high signal attenuation (SA), small NGD bandwidth and magnitude (S 21 ) flatness. While a few works have been done for reducing SA [19][20][21][22], these works still suffer from small NGD bandwidth and magnitude flatness problem. To overcome these problems, researchers have attempted to design NGD circuits using different methods such as cross-coupling between resonators [23], increasing the number of resonators [24] and transversal-filter topologies [25].…”

A Miniaturized Self-Matched Negative Group Delay Microwave Circuit

“…Table 1 compares the proposed NGD circuit with previous publications. Compared to the reflectiontype NGD circuits in [14] and [15], the proposed NGD circuit has larger NGD bandwidth and better return losses performance without the need for external matching networks. The proposed NGD circuit has the same level of NGD time but provides lower insertion loss than the circuits in [16] and [20].…”

“…In microwave circuits, series and parallel RLC resonators are widely used to achieve NGD phenomenon [8][9][10][11][12][13][14][15]. Most of them are used in the reflection-type NGD circuit.…”

“…Most of them are used in the reflection-type NGD circuit. For reflection-type NGD circuits, an extra component, such as a hybrid coupler is always needed to convert these circuits to transmission-type circuits and realize port matching [12][13][14][15]. In addition, some RLC resonators are used in the transmission-type NGD circuit with the filter synthesis approach [16].…”