Frequency Tunable Non-Reciprocal Bandpass Filter and Diplexer Using Time-Modulated Microstrip λg/2 Resonators

Abstract

This paper presents novel designs of frequency reconfigurable distributed non-reciprocal bandpass filter and diplexer based on spatio-temporally modulated microstrip λg/2 resonators. The modulation is achieved by loading both ends of the λg/2 transmission line resonators with time-modulated capacitors. To provide an inherent biasing isolation between the RF and the modulation signals, the modulation voltage source is connected at the center of the resonator, where there is a natural voltage null. A single inductor is used to further enhance such biasing isolation. The wideband nature of this isolation scheme enables the tuning of the devices over a wide frequency range. With more than 30-dB RF to modulation isolation, the proposed resonator structure also enables low insertion loss by eliminating RF signal leakage to the modulation ports. Two examples of a 3-pole bandpass filter and a diplexer are demonstrated with good agreement between the measurement and the simulation. The fabricated filter shows a minimal insertion loss of 3.9 dB, a 20-dB isolation bandwidth of 42 MHz at 1.0 GHz, and frequency tuning range of 885-1031 MHz. The measured diplexer has two non-reciprocal bandpass channels at 829 MHz and 997 MHz, respectively. The two channels can be independently reconfigured without affecting each other.

MMIC GaAs Isolators and Quasi-Circulators With Co-Designed RF Filtering Functionality

“…Furthermore, when passive BPFs are realized with IC-based resonators, they exhibit high levels of IL (IL ∼ 4.5-9.3 dB in [14], [15]). To reduce the size of the non-reciprocal devices and BPFs, two major miniaturization approaches have been investigated: i) the integration of the non-reciprocal components into a chip using MMIC, CMOS, SiGe, technologies [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29] and ii) the RF co-design of the non-reciprocal components with the BPFs with or without ferrite-based elements [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44].…”

“…In yet another magnetless circuit-based design approach, spatiotemporally modulated (STM) switched capacitor arrays, transmission lines or resonator-arrays are employed within a three-port network to achieve non-reciprocity [46], [47], [48], [49]. Alternative integration schemes using PCB ( [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [48]) and CMOS based integration platforms ( [46], [47], [48], [49]) have been demonstrated. However, the operating principles of many of them have been demonstrated at frequencies <1.2 GHz (e.g., [32], [33], [34], [35], [36], [37], [40], [41], [48], [49]).…”

Magnetless microstrip circulators based on differential spatiotemporal modulation of resonators

“…However, these active circulators generally suffer from poor noise performance and strong nonlinearity. Recently, time‐modulated devices, including conductivity modulation 6–8 and permittivity modulation, 9–14 have drawn more and more attention because of their superior property. Conductivity modulated circulators, usually employing switched capacitors or transmission lines, are proved with high power handling ability and relatively low noise figure.…”

Lightweight Low-Noise Linear Isolator Integrating Phase-Engineered Temporal Loops

“…Time modulation has recently attracted a surge of interest thanks to its distinctive capabilities in nonmagnetic nonreciprocal signal transmission and frequency generation [3,[27][28][29][30][31][32][33]. As a result, diversified applications of time modulation techniques have recently been discovered, including signal amplification [34][35][36], unidirectional beam splitting [37], pure frequency conversion [38], multi-functional and nonreciprocal metasurfaces [39][40][41][42][43], circulators [28,44], nonreciprocal filters [45], and multi-functional antennas [46][47][48]. The linear non-magnetic nonreciprocity undergoing time modulation has been shown to be a prominent alternative to conventional cumbersome ferrite-based, transistor-loaded and nonlinear nonreciprocal devices [24,46,[49][50][51][52][53][54].…”