40-nm CMOS Wideband High-IF Receiver Using a Modified Charge-Sharing Bandpass Filter to Boost Q-Factor

Abstract

A 40-nm CMOS wideband high-IF receiver is presented in this paper. The low-noise transconductance amplifier (LNTA) uses dual noise cancellation in order to improve its noise figure. The LNTA has also a folded-cascode structure to increase its output impedance and prepare for a current-mode passive mixer. This structure is merged into the output stage of the LNTA, so there is no need for extra transistors. Additionally, a modified charge-sharing bandpass filter with cross-connected transconductors to boost Q-factor is proposed and discussed. The highest voltage gain achieved by the receiver (RX) is 30 dB. The RX noise figure is 3.3 dB at the maximum gain, while the IIP3 is −2.5 dBm at 1 GHz. The area of the receiver is very competitive for the wide band considered, merely 0.137 mm 2. The RX and clock generation circuitry drain 25 mA from a 0.9-V supply.

A Charge-Sharing Bandpass Filter Topology with Boosted Q-Factor in 40-NM CMOS

“…This second peak is barely noticeable on the 4/8-phase CS-BPF transfer function (TF), but it already affects the symmetry of the magnitude TF. Due to the second peak, the image attenuation improves only by 5 dB from the 4/8phase to the 4/16-phase BPF [6]. Based on these points, we conclude that increasing the order of the filter beyond two (e.g., 4/8-phase BPF) is hardly worth the cost of complexity and power consumption.…”

“…By improving the Q-factor, both the image attenuation and the filtering of out-of-band blockers are improved. Nevertheless, since the I and Q paths are still independent, the I/Q mismatch remains affected mainly by the clock generation [6], [12]. A.…”

“…This "replica" folding issue was solved by the fullrate charge-sharing (CS) BPF introduced in [5]. In [6], an enhancement to the full-rate CS-BPF was introduced, which in turn allows for a sharper filtering without additional power consumption burden.…”

“…In this paper, the modified CS-BPF which was tested in [6] has its CMOS design presented in detail. Its main advantages over the traditional CS-BPF approach are discussed, and the small noise impact of the circuit modification is carefully analysed.…”

Enhancing Q-Factor in a Biquadratic Bandpass Filter Implemented with Opamps

“…In the opamp-RC topology, the capacitor values are fixed and a sensitivity analysis is performed for each resistance to identify which one can help to enhance the Q factor, which must be as high as possible to avoid energy loss. Some recent works on enhancing the Q factor in a bandpass filter include works by the authors of [19,20]. In the former work, the authors propose a modified charge-sharing bandpass filter with cross-connected transconductors to boost Q-factor, and, in the other work, a tunable synthetic fourth-order bandpass filter is synthesized by two parallel second-order Q-enhanced LC bandpass filters.…”