This paper presents a programmable wideband low pass filter (LPF) with Continuous-Time (CT)/Discrete-Time (DT) hybrid architecture. Unlike the conventional DT LPF, the proposed LPF eliminates sample & hold circuits, enabling to expand available bandwidth. The transfer function and the influence of the circuit imperfection are derived from CT/DT hybrid analysis. A prototype has been fabricated in 40 nm CMOS process. The proposed LPF achieves 2.5 GHz bandwidth by wideband equalization, which offers capacitance ratio (Cratio) and clock frequency (fCK) programmability. The proposed LPF occupies only 0.048 mm2 of active area.

A new or future system of mobile telecommunication is built by new digital technologies to provide an improved and more consistent quality of service for the customers. These digital systems can provide greater number of transmission channel allocation for their subscribers and security. On the digital communication system, distortion of transmitted signal should be eliminated as much as possible for high communication quality. However, the need to both minimize distortion of signal amplifiers and continue to provide good filtering protection can become difficult to achieve with conventional high power amplifiers and filters. In this paper, the application of high-Tc superconducting (HTS) power filters on such digital communication systems and recent progress of filter device developments for those are discussed.

Sandwich-type Josephson junctions with the structure Bi2Sr2Ca1Cu2Ox/Bi2Sr2Cu1Oy/Bi2Sr2Ca1Cu2Oz (BSCCO/BSCO/BSCCO), have been fabricated and their characterstics determined. The BSCO barrier layer, which is characterized by a crystal structure close to that of the BSCCO electrode layer, is a normal conductor at 4.2 K. Superconductor/normal-conductor/superconductor (S/N/S) type current-voltage characteristics are obtained with these junctions. Distinctive Shapiro steps are observed when they are exposed to microwave radiation. An oscillating behavior of each step in their I-V characteristics are confirmed for increased microwave power. The critical current, Ic, is found to be proportional to (1-T/Tc)2 in the neighborhood of Tc. These results coincide with the ones observed with conventional S/N/S junctions.

A 60 GHz direct conversion transceiver which employs amplitude/phase imbalance cancellation technique is newly proposed. By using the proposed technique, the receive path of the transceiver achieves less than 0.2 dB of amplitude error and less than 3 of phase error at 60 GHz bands over a 10 GHz bandwidth, which relaxes the design accuracy required for baluns used in the transceiver. It also employs a simple and fast calibration algorithm to adjust the locking range of the divide-by-3 injection locked divider in the phase locked loop. Fabricated in 90 nm CMOS technology, the transceiver achieves a low power consumption of 230 mW in transmit mode and 173 mW in receive mode. The output spectrum of 1.76 Gsps π/2-BPSK/QPSK modulation shows the excellent distortion and spurious suppression that meet the IEEE802.11ad draft standard.