In a beamforming circuit for a modern broadband phased-array system, high accuracy and compactness have received sufficient attention as they are directly related to side lobe level and fabrication cost, respectively. In order to meet the low phase error required, this paper proposed an ultra-broadband 6-bit digital step switched-type attenuator (STA) with capacitive/inductive compensation networks. Compared to the conventional methods, the proposed technique employs an improved simplified T-structure with capacitive compensation networks, which simultaneously achieves low insertion loss and high-accuracy amplitude/phase control. In addition, on-chip level shifting circuit is integrated to avoid complex control schemes. The strategy of prioritizing return loss is adopted to alleviate the performance degradation caused by impedance mismatch after cascade. As a proof-of-principle demonstration, a wideband 6-bit STA with core area of only 0.5 mm × 1.8 mm was designed via 0.15-micrometer GaAs pHEMT technology. It exhibits ultra-broadband operation with a 31.5 dB amplitude tuning range and a 0.5 dB tuning step. The insertion loss of the reference state is 4–5.3 dB. The return loss is better than 15 dB for all the 64 states. The RMS amplitude and phase errors are less than 0.2 dB and 2° over the 10 to 20 GHz.

Yu, Z.T.; Chen, J.; Zhang, B.Q.; Wang, D., and Jiang, H., 2020. Selection method of optimal wavelet basis function for aeromagnetic anomaly signal processing. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 530-534. Coconut Creek (Florida), ISSN 0749-0208.We proposed a selection method of optimal wavelet basis function for the signal processing of aeromagnetic anomaly of underwater targets. Based on traditional evaluation index of signal processing, we firstly proposed the comprehensive evaluation index of wavelet basis function selection, which was based on traditional evaluation index of signal processing and wavelet features. Next, we used the comprehensive evaluation index to evaluate the processing results of the typical magnetic anomaly signals of underwater targets, and obtained the optimal wavelet basis function. Finally, we verified the proposed method by the aeromagnetic anomaly simulation signals of underwater targets. The experimental results show that the optimal wavelet basis functions obtained by the proposed method have a better enhancement effect on the aeromagnetic anomaly measurement signal of the underwater target.

In view of the wide and effective application of wavelet transform in the study of weak signal detection, it has been applied to the enhancement of magnetic anomaly signal of underwater target. But there is a problem of the decomposition level selection in the process of wavelet enhancement, which is related to the parameters of Aeronautical platform and underwater target. In this paper, based on the detection model of underwater target magnetic field, the selection model of wavelet decomposition level of aeromagnetic anomaly signal was established, and was realized adaptive wavelet enhancement of aeromagnetic anomaly signal by weighted reconstruction. The processing results of the simulation test signal show that the method can effectively enhance the weak magnetic signal of underwater target.

Generalized broadband operation facilitates multifunction or multiband highly integrated applications, such as modern transceiver systems, where ultra-wideband bidirectional passive mixers are favored to avoid a complex up/down-conversion scheme. In this paper, a modified Ruthroff-type transmission line transformer (TLT) balun is presented to enhance the isolation of the mixer from the local oscillator (LO) to the radio frequency (RF). Compared to the conventional methods, the proposed Ruthroff-type architecture adopts a combination of shunt capacitors and parallel coupled lines to improve the return loss at the LO port, thus effectively avoiding the area consumption for the diode-to-balun impedance transformation while simultaneously providing a suitable point for IF extraction. In addition, a parallel compensation technique consisting of an inductor and resistor is applied to the RF balun to significantly improve the amplitude/phase balance performance over a wide bandwidth. Benefiting from the aforementioned operations, an isolation-enhanced 8–30 GHz passive double-balanced mixer is designed as a proof-of-principle demonstration via 0.15-micrometer GaAs p-HEMT technology. It exhibits ultra-broadband performance with 7 dB average conversion loss and 50 dB LO-to-RF isolation under 15 dBm LO power. The monolithic microwave integrated circuit area is 0.96 × 1.68 mm² including all pads.