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A differential low-voltage high gain current-mode integrated RF front end for an 802.11b WLAN is proposed. It contains a differential transconductance low noise amplifier (Gm-LNA) and a differential current-mode down converted mixer. The single terminal of the Gm-LNA contains just one MOS transistor, two capacitors and two inductors. The gate-sourc...
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... to be 17.48 dB. The noise is only 4.5 dB. Compared with Ref. [11], this circuit has a higher power gain, a simpler structure and a lower noise figure when using a one stage G m -LNA and a new switched current mirror mixer; in addition, when compared with Refs. [9, 10], the circuit has a lower supply voltage and higher linearity. Figure 1 is a whole block diagram of a direct-conversion current-mode RF receiver. The RF input signals from the an- tenna enters the transconductance LNA, which amplifies and converts the voltage signal to current signal. The current signals then enter the current-mode mixer and are mixed with signals from a local oscillator (LO). The output current signals from the mixer are processed by a current-mode low-pass fil- ter. Finally, the filtered signals enter the base-band signal pro- cessing system. The dashed box contains the transconductance LNA and the current mixer researched in this paper. The proposed low voltage current-mode RF receiver front- end circuit is shown in Fig. 2. It contains a differential G m -LNA and a differential current-mode mixer. The differential G m LNA is composed of Mg1,2, L g1 ; 2 , L s1 ; 2 , C g1 ; 2 , C x1 ; 2 . It amplifies and converts the input RF voltage signal to current signal. The other active components form the differential switched current mirror current-mode mixer. The supply voltage V sup is 1 V. Figure 3 shows the proposed differential transconductance low-noise amplifier used in the receiver. It amplifies the input voltage signal and produces differential output current i rf C and i rf for the current-mode mixer. By using the G m -LNA, I – V conversion of the LNA output can be eliminated and the current output of the LNA directly connected to the current- mode mixer input. This approach decreases the non-linearity of the receiver caused by several I – V and V – I conversions. The single-side of the G m -LNA contains just one MOS transistor, two capacitors and two inductors. The gate–source shunt capacitors C x1 and C x2 can not only reduce the effects of gate–source C gs on resonance frequency and input matching impedance, but can also make the gate inductance L g1 ; 2 to be selected at a very small value. Compared with previously reported similar G m -LNA Œ10; 11 , this circuit has the following advantages: (1) the circuit structure is much simpler due to its one-stage structure; (2) it is not easily affected by gate–source C gs for introducing C x1 and C x2 ; (3) the gate inductance L g1 ; 2 to be selected at a very small value. In Fig. 3, L s1 ; 2 and L g1 ; 2 , together with the capacitance C gs1 ; 2 and C x1 ; 2 , form the impedance-matching network used to produce 50 pure resistance in the resonance frequency. By choosing C x1 ; 2 and L s1 ; 2 appropriately, 50 pure resistance can be easily achieved. The inductance L g1 ; 2 is used to make the input impedance of the LNA resonate, while C x1 ; 2 and L s1 ; 2 are chosen to make the input impedance of the LNA ...
Citations
In this paper, an all current mode RF receiver of direct conversion for 802.11b WLAN has been proposed. The front end of this receiver, containing a current mode LNA plus mixer (CLPM) circuit and a current mode quadrature ring oscillator (CQRO), has been designed and simulated in chartered 0.18 m CMOS process. The proposed method features that the pseudo-cascode current mirrors of the current mode LNA have not been implemented in cascade, so we can decrease the supply voltage and increase the output impedance by adding a common-gate transistor. The current mode mixer has been composed by the four added common-gate transistors; this implementation makes the current mode mixer a two-layer structure that reduces the supply voltage. The current mode quadrature oscillator is a four current mode stage ring oscillator employing feed forward paths. The CLPM has a measured power conversion gain of 18.6 dB, an input referred third-order intercept point (IIP3) of -0.53 dBm. The total noise figure is 3.9 dB and the power is only 15 mW by post-simulations. The CQRO core current consumption is 24 mA with a 1 V supply. The phase noise results in -121.61, -148 dBc/Hz at 1 MHz, and 10 MHz from the carrier, respectively.
