High linearity low noise down-conversion mixer in ultrahigh frequency radio frequency identification (RFID) reader
A technology of mixer and drain, which is applied in the direction of modulation conversion balance device, etc., can solve the problem of noise increase
Inactive Publication Date: 2010-07-21
HUNAN UNIV
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Problems solved by technology
In the UHF RFID reader, there is serious self-interference between the transmitter and the receiver, and there is also adjacent channel interference between the readers, so the design of the transmitter and receiver with high linearity and high sensitivity It can effectively simulate self-interference and adjacent channel interference, and the linearity and sensitivity of the receiver are mainly determined by the down-mixer, so high linearity, low noise, high gain, low voltage and low power consumption have become mixers important indicators, but these indicators are mutually restrictive, such as linearity and gain are two contradictory indicators, the improvement of linearity is at the expense of the decrease of gain, and the working conditions of low voltage will likely cause noise raised
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[0016] figure 2 For the second-order intermodulation current injection structure, the small-signal output current of the tube at the static operating point can be expressed as:
[0017] i d =g 1 (v g -v s )+g 2 (v g -v s ) 2 +g 3 (v g -v s ) 3 +... (1)
[0018] where g i Represents the i-order transconductance coefficient of the tube, v g and v s Represents the gate and source voltages of the tube, respectively. Through analysis, two signals ω with different angular frequencies but the same amplitude can be known 1 , ω 2 When inputting, we inject another low frequency with a size of 2x*cos(ω 1 -ω 2 )t second-order intermodulation current, then there is
[0019] i p + i n =2x*cos(ω 1 -ω 2 )t (2)
[0020] Simultaneously (1) and (2), the frequency at the common source node can be obtained as (ω 1 -ω 2 ) small signal source level voltage v s for:
[0021] v s | ω ...
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The invention provides a down-conversion mixer facing an ultrahigh frequency radio frequency identification (RFID) reader, relating to a high linearity mixer based on a Gilbert structure. The linearity is enhanced by adopting a second-order intermodulation current injection structure at the input end, and a dynamic current injection structure is adopted at the output end to lower the noise. In the second-order intermodulation current injection structure, an injection current value which enables a three-order intermodulation current value to be 0 is obtained by analyzing the nonlinearity characteristic of an MOS pipe; and the dynamic current injection structure is adopted at the output end to realize the dynamic injection characteristic of a current by analyzing the conduction characteristic of the MOS pipe, thereby the flash noise of the mixer is greatly reduced. The mixer has the work voltage of 1.2V and low power consumption, accords with the requirements of low voltage and low power consumption and has great guiding significance in the aspects of simplifying a circuit structure, lowering the power consumption, expanding center work frequency point and the like.
Description
technical field [0001] The technology relates to a mixer based on a Gilbert structure in an ultra-high frequency RFID reader, in particular a mixer with high linearity and low noise, belonging to the field of analog integrated circuits. Background technique [0002] RFID is the abbreviation of Radio Frequency Identification, that is, radio frequency identification technology, which is a kind of automatic identification technology. It conducts non-contact two-way data communication through radio frequency to identify targets and obtain relevant data. [0003] According to the working frequency, the RFID system can be divided into: 1) Low frequency system: the working frequency is generally 30∽300KHz, the typical working frequency is 125KHz, 133KHz; 2) Medium and high frequency system: the working frequency is generally 3∽30MHz, the typical working frequency 13.56MHz; 3) UHF and microwave systems: the operating frequency is generally 300MHz∽3GHz or greater than 3GHz, and its t...
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IPC IPC(8): H03D7/14
Inventor 王春华汪飞袁超郭胜强许静张秋晶何海珍郭小蓉易波
Owner HUNAN UNIV