Bandwidth Tunable Optical Bandpass Filter Based on Parity-Time Symmetry

A chip-scale tunable optical filter is indispensable to meeting the demand for reconfigurability in wavelength division multiplexing systems, channel routing, and switching, etc. Here, we propose a new scheme of bandwidth tunable band-pass filters based on a parity-time (PT) symmetric coupled microresonator system. Large bandwidth tunability is realized on the basis of the tuning of the relative resonant frequency between coupled rings and by making use of the concept of the exception point (EP) in the PT symmetric systems. Theoretical investigations show that the bandwidth tuning range depends on the intrinsic loss of the microresonators, as well as on the loss contrast between the two cavities. Our proof-of-concept device confirms the tunability and shows a bandwidth tuning range from 21 GHz to 49 GHz, with an extinction ratio larger than 15 dB. The discrepancy between theory and experiment is due to the non-optimized design of the coupling coefficients, as well as to fabrication errors. Our design based on PT symmetry shows a distinct route towards the realization of tunable band-pass filters, providing new ways to explore non-Hermitian light manipulation in conventional integrated devices.

Reconfigurable diplexer using hybrid couplers and perturbed TE012 cavities

A continuously tunable Ku-band waveguide diplexer is proposed in this paper. This diplexer is based on a hybrid coupler topology and is composed of an input filter centered at 11.9 GHz with a 200 MHz bandwidth, a pair of ladder-type hybrid couplers, and a pair of tunable filters. This diplexer can provide two bandpass channels (channels 1 and 2) that can continuously go from a state where the bandwidths of channels 1 and 2 are maximum (up to 140 MHz) and minimum (down to 40 MHz), respectively, to another configuration where the bandwidth of channel 1 is the largest and the bandwidth of channel 2 is the narrowest. We propose a tunable filter based on TE012 mode circular cavities that are perturbed by low-loss dielectric inserts to obtain such performance. The resonant frequency of these cavities can be continuously tuned between 11.8 and 12 GHz due to the linear movement of the dielectric perturber. The design process for these components is presented and a breadboard device has been manufactured and measured to prove the concept. Different measured configurations of the diplexer are demonstrated, showing that the 200 MHz operating bandpass between 11.8 and 12 GHz can be efficiently separated into two tunable channels. The measured bandwidth of channels 1 and 2 in the manufactured diplexer can be tuned from 135 to 40 MHz (and vice versa) while maintaining an average guard band between the channels of approximately 26 ± 7 MHz. The obtained bandwidth tuning ratios are 3.2 for the highest channel and 3.1 for the lowest channel.

Wideband Reconfigurable Integrated Low-Pass Filter for 5G Compatible Software Defined Radio Solutions

This article presents a wideband reconfigurable integrated low-pass filter (LPF) for 5G NR compatible software-defined radio (SDR) solutions. The filter uses Active-RC topology to achieve high linearity performance. Its bandwidth can be tuned from 2.5 MHz to 200 MHz, which corresponds to a tuning ratio of 92.8. The order of the filter can be changed between the 2nd, 4th, or 6th order; it has built-in process, voltage, and temperature (PVT) compensation with a tuning range of ±42%; and power management features for optimization of the filter performance across its entire range of bandwidth tuning. Across its entire order, bandwidth, and power configuration range, the filter achieves in-band input-referred third-order intercept point (IIP3) between 32.7 dBm and 45.8 dBm, spurious free dynamic range (SFDR) between 63.6 dB and 79.5 dB, 1 dB compression point (P1dB) between 9.9 dBm and 14.1 dBm, total harmonic distortion (THD) between −85.6 dB and −64.5 dB, noise figure (NF) between 25.9 dB and 31.8 dB and power dissipation between 1.19 mW and 73.4 mW. The LPF was designed and verified using 65 nm CMOS process; it occupies a 0.429 mm2 area of silicon and uses a 1.2 V supply.

Self-Tuning Algorithm for Tuneable Clamping Table for Chatter Suppression in Blade Recontouring

The production and repair of blades for aerospace engines and energy turbines is a complex process due their inherently low stiffness and damping properties. The final recontouring operation is usually performed by milling operations where regenerative chatter is one of the main productivity limiting factors. With the objective of avoiding specific stiffening fixtures for each blade geometry, this paper proposes a semi-active tuneable clamping table (TCT) based on mode tuning for blade machining. The active mode of the device can be externally controlled by means of a rotary spring and eddy current damping modules. Its in-series architecture allows damping to be introduced to the critical mode of the thin-walled part without any direct contact in the machining area and enables a more universal clamping. Its chatter suppression capabilities are maximized by means of a novel self-tuning algorithm that iteratively optimizes the tuning for the measured chatter frequency. The benefits of the iterative algorithm are validated through semidiscretization and initial value time-domain simulations, showing a clear improvement in blade recontouring stability compared to regular broad-bandwidth tuning methods.

A fully reconfigurable bandpass-to-bandpass-with-embedded-stopband filter with an ultra-wide 0.09–1.41 GHz bandwidth tuning range

A varactor-based fully reconfigurable microstrip bandpass-to-bandpass-with-embedded-stopband filter is presented in this paper. This filter offers wide center frequency and bandwidth tuning flexibility under both bandpass mode and bandpass-with-embedded-stopband mode. The entire tuning ability is based on multiple mode resonator theory and external quality factor tuning structure for bandpass mode and the introduction of transmission zeros (TZs) for bandpass-with-embedded-stopband mode. Under the bandpass mode, the center frequency tuning range is 0.96–1.45 GHz and the bandwidth can be tuned from 0.09 to 1.41 GHz with a fixed center frequency at 1.22 GHz. Under bandpass-with-embedded-stopband mode, the center frequency and bandwidth can be tuned from 0.94 to 1.61 GHz and 0.2–0.33 GHz, respectively. Good agreements are shown between simulated and measured results.