| Recent years, in response to market developments, the design of wireless receiver follows trends that include lower cost, lower power, smaller size, and multifunction and multistandard. Highly integrated receiver architecture and lower cost Si CMOS technology will reach those trends. In particular, direct conversion architectures have gained increasing attention because of their potential for high level of integration and low power consumption. Mixer is one of the key modules in the receiver, so it is important to design a mixer with high performance. An even harmonic mixer with high gain and high linearity was designed in this paper.The characteristics of UWB system are high data rate, low power consumption and low cost. UWB becomes new developing technology in the wireless personal network (WPAN). Under the trend of the WPAN, the usage of UWB may extensively makes life more convenient in the coming future. This paper designed a high linearity 3-5GHz wide band mixer applied in UWB system.Paper first introduces the CMOS RF integrated circuits, and mixers Research, describes the current low-cost, high integration, low power, high-performance trend. Then the paper followed by a brief analysis of the current structure of commonly used several receivers: superheterodyne receiver, image rejection receiver, zero-IF receiver, low-IF receiver, and compares the advantages and disadvantages of these types of receivers.Mixer is one of the key modules in the radio transceiver, and its performance greatly impact on the entire wireless system. Design a mixer with good performance is the purpose of this paper. The paper outlines the principles of the mixer。In the receiver, the mixer function is put the RF signal and local oscillator signal mixing, then down conversion to IF signal that can be the processed well by successor module. According to the different standard, the mixer may be divided into different type, no matter but, the performance of mixer mainly includes the conversion gain, linearity, noise factor and so on. Through analysis, the conversion gain, linearity, and the NF should be trade-off during design a mixer, and the current injection technology may improve the relations which between the mixer performance parameter restricts mutually. In the numerous performance indices, the linearity is quite important one, therefore this article has carried on the analysis emphatically to the linearity, and this paper also describes the reason of non- linear problem and the optimization techniques to improve the linearity in detail.An even harmonic mixer is designed in this paper. The proposed mixer employs a current reuse circuit in the RF input stage to improve its linearity and conversion gain , and uses the double frequency technique in the LO input stage, respectively. And an inductor is inserted between current reuse circuit and double frequency circuit to improve the linearity. So the designed mixer has the performance of high linearity and high gain. However the inductor used in that design occupies large area in the layout and consumes more power with the increase of frequency. This paper presents an EHM with a LC resonant circuit instead of the enhancement inductor, The simulated results reveal that this improved mixer has higher performance and smaller size.This paper also attempt to design a 3-5GHz wide band mixer that used the folding mixer structure, this structure reduces the supply voltage request, and causes the transconductance stage and the switch stage work better in the saturation area. In addition, the third-order distortion is cancelled due the transconductance stage use the feedforward circuit to improve the linearity, so the designed mixer has high linearity. All mixers designed in this paper realize in SMIC 0.18μm CMOS RF craft, simulate in ADS, and design layout in Virtuoso. |
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