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The time-interleaved analog-to-digital converters (TIADCs) technique is an efficient solution to improve the sampling rate of the acquisition system with low-speed ADCs. However, channel mismatches such as gain mismatch, time skew mismatch, and offset mismatch may seriously degrade the performance of TIADC. Furthermore, for high-speed signal acquisition, the gain and time skew mismatches would vary with the signal frequency, and the traditional fixed model does not work any longer. In this paper, a series of sinusoidal signals are adopted to estimate the variable mismatches. First, an autocorrelation-based approach is presented to estimate the gain mismatch. The information about the gain mismatch is extracted from the autocorrelation function of sub-ADC output samples. Then, the time skew mismatch is estimated by utilizing the particle swarm optimization algorithm. The reported simulation results show that the mismatches can be accurately estimated. Finally, a commercial 12.5 GSPS four-channel TIADC system is utilized to verify the performance of the proposed method. The spurious free dynamic range of the system can be improved by about 20 dB, and the effectiveness of the proposed estimation method is demonstrated.

This article presents a dual-band shared-aperture antenna array for a phased array system operating in the Ku/E-bands with a large frequency ratio. A regular array arrangement is used to arrange single-layer coupled microstrip patch elements that operate in the Ku-band. E-band elements using slot-coupled microstrip patch antennas are arranged in a sparse concentric circular array configuration. In addition, E-band transceiver/receiver (T/R) chips are attached to the back of the array's multilayer printed-circuit board (PCB) to achieve high density with a low-profile. In the shared-aperture of the proposed antenna array, there are 64 elements in both Ku-and E-bands. According to the results of our experiments, the Ku-band array has a large scanning angle spanning from À45 to +45 with low gain drop and sidelobe level (SLL). It also exhibits a comparatively wide impedance bandwidth of 17.8% in the frequency range of 14.65-17.51 GHz. The E-band array has a scanning angle of about ±20 in both the E-and H-planes and a 7.7% simulated impedance bandwidth covers the frequency range of 75.8-81.9 GHz.

As the application of microwave to radar and 5G communication goes wider, the array beam scanning capability has become an important and popular issue in modern society. Appropriate implementation of beam scanning methods suitable for diverse conditions could provide better performance and help to save costs for a system. Moreover, electronically scanned array has the characteristics of fast beam switching rate, high measurement accuracy and low profile. Thus, discussions on typical electronic scanning approaches are particularly necessary. This paper first presents a review of typical electronic scanning approaches to microwave arrays, such as the phased array, the focused aperture array, the frequency scanning array, and the time modulated array. And then some latest designs in the industry have been introduced. In addition, problems appeared in the application of the phased array and relevant solutions have been put forward. For the rest, some discussions are briefly summarized, as well as some comments on future trend in this field.