Montgomery modular multiplication algorithm is commonly used in implementations of the RSA cryptosystem and other cryptosystems with modular operations. Radix-2 version of this algorithm is simple and fast in hardware implementations. In this paper this algorithm is modified with a new recoding method to make it simpler and faster. We have also implemented this new algorithm with carry save adders. Results show that, in average the proposed algorithm has about 47% increase of data throughput with maximum 7% increase of hardware area comparing with conventional algorithm.

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This paper presents a new low phase noise quadrature voltage-controlled oscillator (QVCO). Coupling phase shifts of 90° in conjunction with center-tapped capacitor impedance transformers are exploited to optimally couple two VCOs. DC and AC path of the switching and coupling pairs are de-coupled to allow operation in saturation for large oscillation amplitudes. The switching and coupling transistor pairs operate in class-C mode which increases the DC to RF efficiency. Also, these transistors alternate from strong inversion to accumulation region, decreasing the intrinsic device flicker noise. Simulations confirm the superiority of the proposed circuit in comparison with the prior published QVCOs in terms of phase noise performance.

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The pathloss model in the literature suffers from two major deficiencies: First, it is distance dependent, whereas the distance of an interior link is unknown to outsiders. Second, it suffers from line-of-sight (LOS) uncertainty with channel parameters fluctuating sharply between LOS and non-LOS conditions. In this paper, we address these problems by taking the distance as a random variable and by introducing a room-density index that combines the LOS and non-LOS conditions. We then modify the widespread IEEE 802.15.4a pathloss model into a unified pure statistical pathloss model that is a function of the room size and the room-density index. This pure statistical model supplements the conventional pathloss model and can help cognitive users infer pathloss information of the non-cognitive without knowing the latter's link distance.

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This paper describes a wideband power divider using a new type of transmission line transformer (TLT) to change impedance from 50 to 25Ω. A prototype of the power divider to connect two 50-Ω coaxial cables to the 25-Ω output ports of the proposed TLT was fabricated. The reflection characteristics of the proposed TLT were less than -15dB over the range 54-907MHz. The reflected power of the power divider was less than -14dB, and the relative amplitude and phase difference between two outputs of the power divider were within ± 0.15dB and ± 1.0° over the range 100-900MHz.

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This letter presents a DLL (Delay Locked Loop)-based CDR (Clock Data Recovery) design with a modified input data format. The proposed CDR recovers the clock and tracks the phase by the proposed training and real data patterns. The proposed input data formatting is done by inserting the ‘01’ pattern in every N-bit data. To prove the feasibility, a 2.4Gbps CDR is designed and simulated. The training and the real data pattern were formatted as the 10B12B for a high-performance display interface. The CDR achieves less jitter due to the DLL structure. The proposed CDR with the 10B12B format consumes approximately 8mA under 3.3V power supply using 0.25µm CMOS process.

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The Diversity-Multiplexing Tradeoff (DMT) in shadowed Nakagami fading channels is evaluated while the multiple antennas technique is used at the transmit or receive sides. We show that at the infinite Signal to Noise Ratio (SNR), the asymptotic DMT is not affected by the lognormal shadowing. However, the shadowing phenomena can dramatically reduce the achieved finite SNR diversity gain for all multiplexing gains. Also, we derive the effect of the Nakagami fading parameter on the provided DMT by MISO/SIMO channels and show that the diversity gain is directly influenced by this parameter.

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This paper presents a performance comparison method among the circuits for different high-frequency communication systems using newly proposed figure of merit (FOM). Efficiencies of transmission energy of circuits for optical communications, cellular phone systems, and ubiquitous network systems are compared by the FOM. The FOM expresses the circuit performance among the different communication systems without the influence of the difference of the communication capacity and the device performance. The FOM of the circuits are plotted in the almost equal value without depending on system differences, and the differences indicate the technical evolutions of the systems and circuit designs.

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In order to meet the demand for mass production of 77GHz automotive radar systems, a low cost and high performance 38/77GHz AlGaAs/InGaAs PHEMT MMIC transmit amplifier with a multiplier has been realized. The chip is packaged in an inexpensive conventional non-hermetic package. Excellent power performance is demonstrated with a 15dBm output power and 7dB maximum conversion gain from 38 to 76.5GHz. Also, highly reliable RF operation of a bare MMIC chip is obtained with less than 0.7dB reduction in output power during 10⁶ hr at V_d=4V and T_a=25°C in air.

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