Novel DC-offset cancellation techniques for even-harmonic direct conversion receivers

A 5.25-GHz CMOS folded-cascode even-harmonic mixer for low-voltage applications

“…Similarly, the relationship between and is obtained as (8) On the other hand, from (5), the time-varying transconductance related to the overdrive voltage can be written as (9) where and are the transconductances of the -and -transistors of the current reuse pair, respectively, and the subscript CR denotes the overall transconductance using the current reuse technique. Furthermore, according to [17]- [19], by assuming and using the Taylor's series expansion, the resulting differential output voltage of the proposed FEHM becomes (10) where (11) and (12) are the fundamental coefficients of the RF signal from -and -transistors, respectively, which are important for the noise figure, and (13) is related to the conversion gain information at the up/down converter, and (14) is the major third nonlinear coefficient affecting the linearity.…”

“…Since the LO frequency is equal to one half of the RF frequency, no dc component is generated by LO leakage, achieving the time-varying self-mixing-free result. Moreover, the LO fundamental leakage can be effectively cancelled by a low-pass filter (LPF) and cannot influence the baseband circuit [9]- [13]. Therefore, if the EHM is employed in direct conversion receivers, the dc offset resulted from self-mixing can be significantly improved and the desired operational frequency of the synthesizer can be relaxed.…”

“…1. As , the local oscillator (LO) leakage is fed through to the mixer input, while the reflection factors such as LNA and the antenna can strengthen this leakage, resulting in a self-mixing behavior by the mixer [9]- [13]. This causes a time-varying dc offset and reduces the dynamic range of the baseband circuit.…”

Zero-if second harmonic SiGe mixer with DC offset cancellation

“…Recent works [4]- [6] utilizing the advantages of SiGe BiCMOS technology show the state of the art. Various approaches are proposed for the cancellation of the DC offset voltage by even suppressing the LO leakage or using digital signal processing techniques in [7]- [9].…”

Direct conversion 2.4-GHz receiver front end design for wireless applications

“…There are several DC-Offset correction methods available [50], [51], [52], [53], [54], [55], [56], [57], [58] calibration. Using a fully balanced design is a standard practice which ideally prevents LO leakage and cancels second order nonlinearity.…”