15MHz wide tuning-range OTA with −69dBHD3 and its application to Gm-C filter
This paper presents a high linearity operational transconductance amplifier (OTA). The OTA circuit combines the techniques of the double differential pairs (DDP) and Source-degenerated current mirrors to achieve high linearity in a large GM tuning range. With the Gm values ranged from 60µS to 130µS, the HD3 of the OTA is below −69dB at 15MHz. The OTA has been applied to a fourth-order linear phase low-pass filter for high speed system. The fourth-order low-pass filter with the cutoff frequency of 15MHz has been implemented. The filter is designed by 0.18-µm CMOS process technology, the HD3 performance is about −53dB, and the group delay variation is below 5% at cutoff frequency.
We consider the MIMO wiretap channel, that is a MIMO broadcast channel where the transmitter sends some confidential information to one user which is a legitimate receiver, while the other user is an eavesdropper. Perfect secrecy is achieved when the transmitter and the legitimate receiver can communicate at some positive rate, while insuring that the eavesdropper gets zero bits of information. In this paper, we compute the perfect secrecy capacity of the multiple antenna MIMO broadcast channel, where the number of antennas is arbitrary for both the transmitter and the two receivers. Our technique involves a careful study of a Sato-like upper bound via the solution of a certain algebraic Riccati equation.