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In this paper, we propose the FeatherWave, yet another variant of WaveRNN vocoder combining the multi-band signal processing and the linear predictive coding. The LPCNet, a recently proposed neural vocoder which utilized the linear predictive characteristic of speech signal in the WaveRNN architecture, can generate high quality speech with a speed faster than real-time on a single CPU core. However, LPCNet is still not efficient enough for online speech generation tasks. To address this issue, we adopt the multi-band linear predictive coding for WaveRNN vocoder. The multi-band method enables the model to generate several speech samples in parallel at one step. Therefore, it can significantly improve the efficiency of speech synthesis. The proposed model with 4 sub-bands needs less than 1.6 GFLOPS for speech generation. In our experiments, it can generate 24 kHz high-fidelity audio 9x faster than realtime on a single CPU, which is much faster than the LPCNet vocoder. Furthermore, our subjective listening test shows that the FeatherWave can generate speech with better quality than LPCNet.

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Back‐channel‐etched (BCE) thin‐film transistors (TFTs) with an InGaO/InZnO stacked channel are developed, in which the InGaO and InZnO provide a highly acid‐resistant back channel and a high‐mobility front channel, respectively. The electrical performance of the TFT is optimized by adjusting the InGaO thickness. The best performance is achieved for the TFT with 10 nm thick InGaO. A thinner InGaO layer leads to inferior performance due to damage during the back‐channel‐etching process, while a thicker InGaO layer results in a hump effect and significant negative shifts in the threshold voltage (Vth) and turn‐on voltage (Von), which should be ascribed to the large total carrier number in the channel. The optimal TFT exhibits a high saturated field‐effect mobility of 28.9 cm2 V−1 s−1, a near‐zero Vth of −0.17 V, a Von of −0.49 V, a low subthreshold swing of 0.12 V dec−1, a high on‐to‐off current ratio of 3.5 × 109, and a low contact resistance between the source/drain (S/D) electrodes and channel. The TFT also exhibits high stability under bias thermal stress.