This letter presents a design for a wideband reflection-type tunable phase shifter (RTPS) with a low in-band phase deviation error. The proposed RTPS consists of a 3-dB hybrid where a through port and a coupled port are terminated with coupled lines, varactor diodes, and a capacitor. The measured capacitance of the varactor diodes was used in the analysis to take into account the in-band phase deviation error caused by the parasitics of the varactor diode. The analysis shows that the desired phase shifting range (PSR) and a low in-band phase deviation error can be obtained by properly selecting the characteristic impedance and coupling coefficient of the coupled line and load capacitance. The experimental results show that the fabricated RTPS provides a PSR of 146.93° at 2.5 GHz and an in-band phase deviation error of ±5.79° within 500 MHz. Moreover, the input-output return losses are higher than 15.76 dB, and the insertion loss is smaller than 1.29 dB within the operating frequency band.

In this letter, a novel design for a dual-band negative group delay circuit (NGDC) is proposed. Based on the topology of a single-band reflection type NGDC, composite right/left handed λ/4 short stubs are employed to obtain a negative group delay (NGD) at two separate frequency bands simultaneously. In order to achieve a bandwidth extension, the proposed structure consists of a two-stage dual-band NGDC with different center frequencies connected in a cascade. According to the measurements performed for wide-band code division multiple access and worldwide interoperability for microwave access, an NGD of -3.0 ± 0.4 ns and -3.1 ± 0.5 ns are obtained at 2.12-2.16 GHz and 3.46-3.54 GHz, respectively.

This study presents a novel approach to the design and implementation of transmission‐type negative group delay (NGD) networks based on a coupled line doublet structure. To improve the reflection coefficients, a quarter‐wavelength transmission line is connected between the input and through ports of a coupled line section. For the doublet structure, two coupled line sections are arranged in a symmetrical manner by connecting them back‐to‐back with the help of the quarter‐ wavelength through line. For the experimental demonstration, two planar NGD networks (unmatched and matched doublet NGD networks) are designed, simulated and measured at a centre frequency of 2.14 GHz. From the measurement, a group delay (GD) of −5.66 ns and signal attenuation (SA) of 18.78 dB were obtained in the case of an unmatched NGD network. Similarly, for the matched NGD case, a GD of −6.33 ns, SA of 20.69 dB and input/output return losses >29 dB were obtained at the centre frequency.

Timely harvesting and disease identification of strawberry fruits is a major concern for commercial level cultivators. Failing to harvest the grown strawberries can result in the fruit rotting which makes their damaged tissues more prone to grey mold pathogens. Immediate removal of the overgrown or diseased strawberries is inevitable to curb the mass spreading of the pathogen. In this paper, we propose a deep learning-based framework to identify three different strawberry fruit classes (unripe, partially ripe and ripe), as well as a class of overgrown or diseased strawberries. We equip the proposed convolutional encoder-decoder network with three different modules. One for adaptively controlling receptive filed size of the network to detect objects of multiple sizes. Second for controlling the flow of salient features (information) to the deeper layers of the network and the other for controlling the architecture's computational complexity. These modules combined, outperform the previous state-of-the-art semantic segmentation networks on the task of strawberry fruit phenotyping. We also introduce a dataset collected from different farms to evaluate the performance of the network. Quantitative and qualitative results show that notwithstanding heterogeneity in the data and the effect of the real-field variations, our approach produced remarkable results with a 3% increase in mean intersection over union as compared to the other state-of-the-art networks and was able to recognize diseased fruits with a precision of 92.45%.

This letter presents a magnet-less nonreciprocal bandpass filter (BPF) that uses coupled static and time-modulated resonators. This coupling allows the nonreciprocal BPF to achieve minimum forward insertion loss (IL) and two pole isolation within the passband and shows wideband and high isolation. The modulation signal is directly applied to the varactor through the transmission line. This design, while simple, nevertheless achieves an excellent nonreciprocal response. We designed, simulated, and experimentally validated a microstrip line nonreciprocal BPF at 1.46 GHz. The results achieved in experiment were consistent with those obtained through simulations; forward IL of 3.10 dB and reverse isolation of 20 dB over a bandwidth of 50 MHz.

In this article, we present a frequency tunable magnetless nonreciprocal bandpass filter (BPF) that uses time-modulated quarter-wave microstrip line resonators. The proposed nonreciprocal BPF can transform real-to-real, real-to-complex, and complex-to-complex termination impedances. To achieve nonreciprocity, a modulation signal is directly applied to the varactor through the transmission line. The modulation scheme in the proposed nonreciprocal BPF, while simple, nevertheless achieves an excellent nonreciprocal response. The center frequency ( f ₀ ) and nonreciprocal response of the proposed BPF are tuned by changing the dc bias voltage of the varactor. The design is validated by experiments using four prototypes of nonreciprocal BPFs (filter A: 50-to-50 Ω, filter B: 20-to-50 Ω, filter C: 25+ j 10-to-50 Ω, and filter D: 25+ j 10-to-55+ j 10 Ω). The measured results confirm that the f ₀ of the nonreciprocal BPF is tuned from 1.64 to 1.97 GHz (330 MHz) with a forward insertion loss variation of 4.96 to 3.94 dB and backward isolation of 20 dB over a bandwidth of 50 MHz.