Kenta Tsukamoto

A 30-MHz-to-3-GHz CMOS array receiver with frequency and spatial interference filtering for adaptive antenna systems

A 30-MHz-to-3-GHz wideband CMOS phased array receiver with interference suppression capability in frequency and spatial domains is presented. A frequency filtering function is provided by a 16-phase, two-stage harmonic rejection mixer which also works as a 5-bit phase shifter in multi-chip phased array systems. Equipped with 6-bit amplitude control in addition to the phase, the array receiver enables analog null steering that can reduce a spatial interferer coming from a specific direction. The developed IC achieves more than 55-dB suppression of harmonic interference in the wide range from 30 MHz to 3 GHz. The multiple ICs configure a four-element adaptive array system for the measurement of space propagation. It is confirmed that the null steering function reduces spatial interference by 20 dB and improves an EVM from -12.7 dB to -26.3 dB even when a strong interferer exists.

A 30-MHz–3-GHz CMOS Array Receiver With Frequency and Spatial Interference Filtering for Adaptive Multi-Antenna Systems

A 30-MHz–3-GHz wideband complementary metal–oxide–semiconductor phased array receiver with interference suppression capability in the frequency and spatial domains is presented. A frequency filtering function is provided by a two-stage harmonic rejection mixer with 16-phase local oscillator (LO) signals that are generated by frequency dividers and phase interpolators. The developed IC suppresses third- to seventh-order harmonic interference by more than 55 dB in a wide range from 30 MHz to 3 GHz. The 16-phase LO signal generator combined with a 2-b baseband phase shifter (PS) also works as a 6-b PS. Equipped with a 6-b amplitude control in addition to the 6-b phase control, the array receiver enables analog null steering that can reduce a spatial interference coming from a specific direction. The multi-chip synchronization needed for the null steering function is realized with pre-set circuits in the frequency dividers. Space propagation measurements made on a four-element array antenna system using the developed ICs indicated that the null steering function reduces spatial interference by 20 dB and reduces the error vector magnitude of a 2-GHz radio frequency, 20-MHz bandwidth, and 64-quadrature amplitude modulation signal from −12.7 to −26.3 dB even when a strong interferer exists.

Suppression of conducted noise coupling in a board with digital and RF circuits by a ferrite film plated on an interposer

This paper presents evaluation results of conducted noise suppression effect of a ferrite film directly plated on an interposer substrate in the long-term evolution (LTE) communication band. A test board for evaluations has an IC with digital and RF circuits which is designed for investigations of electromagnetic noise coupling at the IC chip level. Firstly, we have confirmed effectiveness of a ferrite film onto an interposer in suppression of conducted noise from a digital circuit to a board by simulations. Then, we have verified that the ferrite film reduces conducted noise coupling to the RF circuit, occurring inside the board, by measurements of In-phase/Quadrature (I/Q) signals and high frequency voltages of power supply lines.