Automatic frequency calibration channel selection filter for multi-frequency multi-mode wireless transceiver

Abstract

The invention discloses an automatic frequency calibration channel selection filter for a multi-frequency multi-mode wireless transceiver, which comprises a fully differential operational amplifier, three switch resistance arrays, a decoder, an automatic frequency calibration circuit, two switch capacitance arrays and a capacitor. The filter can be applied to multi-frequency multi-mode wireless transceivers which support wireless local area network, global mobile communication, radio frequency identification and time division synchronous code division multiple accesses. The filter supports eight different frequency bands, reduces the implementation cost of the system and improves the integrity of the system. The automatic frequency calibration circuit of the filter can realize the accurate adjustment of a cut-off frequency, and the error is within 3 percent.

Description

technical field [0001] The present invention relates to a channel selection filter, in particular to a filter that simultaneously supports Radio Frequency Identification (UHF RFID), Time Division Synchronous Code Division Multiple Access (TD-SCDMA), Global System for Mobile Communications (GSM), Wireless Local Area Network (WLAN 802.11 a / b / g) Multi-frequency multi-mode channel selection filter. Background technique [0002] With the rapid development of wireless communication technology, new technologies and standards emerge in an endless stream. Users hope that they can freely access the corresponding network for communication according to their own needs through multi-mode terminals in their hands, so as to realize flexible, convenient and unlimited free communication. , the future development trend will be the continuous integration of various wireless technologies. [0003] The multi-mode multi-band wireless transceiver can simultaneously meet the three application req...

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Problems solved by technology

When the input signal swing is too large, the MOSFET-C filter will have a large nonlinearity. Using a differential structure can improve the linearity of the circuit, but due to the influence of the parasitic capacitance of the MOS tube, its high-frequency characteristics are not as good as the ACTIVE-RC filter. The Gm-C filter has good high-frequency characteristics. The problem lies in the non-linearity of the transconductance and the small input dynamic range. The ACTIVE-RC filter has a good dynamic range and linearity. The disadvantage is that it uses Passive components, while the absolute accuracy of passive components is relatively low, its absolute error may be as high as 15% to 20%, so the filter part needs to be tuned

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