Guican Chen

An Active Inductor-Based VCO With Wide Tuning Range and High DC-to-RF Power Efficiency

An active inductor-based voltage-controlled oscillator (VCO) with a wide frequency tuning range was designed and fabricated using a standard 0.13-μm CMOS process. The oscillator has an LC-tank topology with cross-coupled transistors, and the active inductor was realized using a pair of fully differential very high-speed operational transconductance amplifiers. Due to the differential nature of the inductor, the even harmonics of the output signal were much reduced. Measured results show that the VCO is tunable from 833 MHz to 3.72 GHz, representing a tuning range of 127%. The VCO can produce -0.9 dBm of radio-frequency power. The core circuit, excluding output buffers, consumes 13 mW from a 1.2-V supply.

A 12 GHz-Bandwidth CMOS Mixer With Variable Conversion Gain Capability

A broadband downconverter mixer using an operational transconductance amplifier (OTA) in the RF transconductor stage is presented in this paper. By changing the OTAs transconductance through a dc control voltage, the mixers conversion gain is varied. Experimental results show that the mixers conversion gain can vary from 17 dB down to 1.2 dB over a 12 GHz bandwidth. The maximum IP1 dB of the mixer is -3.7 dBm and its maximum IIP3 is + 8.6 dBm. Meanwhile, the maximum OP1dB is +7 dBm and the maximum OIP3 is +21 dBm. The circuit consumes a maximum of 5.9 mW of power from a 1.2 V supply. The chip occupies an area of 0.105 mm2 excluding bonding pads.

Design of a fully differential CMOS LNA for 3.1-10.6 GHz UWB communication systems

Abstract A fully differential complementary metal oxide semiconductor (CMOS) low noise amplifier (LNA) for 3.1–10.6 GHz ultra-wideband (UWB) communication systems is presented. The LNA adopts capacitive cross-coupling common-gate (CG) topology to achieve wideband input matching and low noise figure (NF). Inductive series-peaking is used for the LNA to obtain broadband flat gain in the whole 3.1–10.6 GHz band. Designed in 0.18 μm CMOS technology, the LNA achieves an NF of 3.1–4.7 dB, an S11 of less than −10 dB, an S21 of 10.3 dB with ±0.4 dB fluctuation, and an input 3rd interception point (IIP3) of −5.1 dBm, while the current consumption is only 4.8 mA from a 1.8 V power supply. The chip area of the LNA is 1×0.94 mm, a .

Wideband microwave OTA with tunable transconductance using feedforward regulation and an active inductor load

A microwave operational transconductance amplifier (OTA) using a feedforward-regulated cascode stage and an active inductor load is proposed in this paper. The use of the feedforward regulation mechanism provides the OTA with a very wide bandwidth of over 10 GHz while the active inductor load contributes to the OTAs high linearity performance. Furthermore, the transconductance of the OTA can be varied from 5 mS to 20 mS. The OTA is designed in a 0.13-µm CMOS technology and it draws a maximum of 5.5 mA of current from a 1.2 V supply when the transconductance is set to 20 mS. The chip occupies an area of 110 µm × 66 µm.

Fully Differential CMOS LNA and Down-Conversion Mixer for 3-5 GHz MB-OFDM UWB Receivers

This paper presents a fully differential low noise amplifier (LNA) and I/Q down-conversion mixers for 3-5 GHz multiband OFDM (MB-OFDM) UWB receivers. The LNA adopts capacitive cross-coupling common-gate (CG) topology to achieve wideband input matching and low noise figure (NF). Tuning technique is used in the double-balanced Gilbert mixer to realize flat conversion gain in the whole 3-5 GHz UWB band. Degeneration inductors are used in the mixer to improve linearity. Designed in 0.18 mum CMOS technology, the LNA achieves a NF of 3.2-3.5 dB and a S11 of less than -13 dB. The LNA and mixer show a total conversion gain of 23.5~25.5 dB, a NF of less than 5dB, an input IP3 of-4.3 dBm and an input IP2 of 47 dBm, while consuming only 10.1 mA from a 1.8 V power supply. The chip area is 1.38 x 0.95 mm2.

A 2.4-GHz linear-tuning CMOS LC voltage-controlled oscillator

This paper presents a voltage-controlled oscillator (VCO) with high linearity in frequency tuning. The VCO has two control inputs. One controls a pair of p/sup +//n-well varactors to realize continuous tuning and the other controls a pair of MOS varactors for band switching. This new circuit topology achieves a good tuning nonlinearity of 1.45% and a wide total tuning range from 2.33 GHz to 2.72 GHz. The simulated phase noise is only -115.7 dBc/Hz at 600kHz offset from 2.4 GHz. Based on a 0.25-/spl mu/m process, the VCO dissipates only 15mW at a 2.5-V supply voltage.

Design of a noise-canceling differential CMOS LNA for 3.1–10.6 GHz UWB receivers

An ultra-wideband (UWB) 3.1–10.6 GHz fully differential low noise amplifier (LNA) employing the broadband noise-canceling technique is presented. With the proposed circuit topology, the noise from the input matching transistor is entirely suppressed over the full UWB band. The LNA is designed in 0.18µm CMOS technology. The simulated results show that the noise figure is 3.7–4.5 dB and the power gain is 13.4–14.1 dB in the desired UWB band, both the input and output reflection coefficients are below −10dB, and the IIP3 is −6.3dBm at 5.7 GHz. It consumes 12.5 mW from a 1.8V supply.1

A 1-GHz LC voltage-controlled oscillator with high linearity and wide range

A 1-GHz low phase noise LC voltage-controlled oscillator (VCO) with high tuning linearity and wide range is presented. A novel resonant tank with a MOS varactor array and distributed control voltages is proposed to improve the tuning linearity and maintain a wide tuning range. Simulation results show that the tuning nonlinearity of the proposed VCO is only 0.8%, reduced by a factor of 4 compared with a conventional one. The VCO draws 5.2 mA current from a 1.8 V supply and can be tuned from 967 MHz to 1146 MHz (17%). The simulated phase noise is -132.2 dBc@1 MHz for an oscillation frequency of 1056 MHz.

The Design of RF Receiver for Frequency Spectrum Sensing in Cognitive Radios

In this paper, a new architecture of RF receivers in the cognitive radios is proposed for sensing the spectral environment. The receiver has two mixer stages and a high intermediate frequency (IF) for up/down dual-converting signal frequency. In order to select the channels in UHF (470-870 MHz) band in TV broadcast, the range of frequency points in the first local oscillator is from 1640 MHz to 2040 MHz with a space of 8 MHz between two adjacent frequency points. The IF is 1166 MHz. The second local oscillator frequency is also 1166 MHz for downconverting the IF to baseband. The simulated results of the receiver show that the noise figure (NF) of the receiver is 6.4 dB, and the conversion gain is about 82.5 dB.

A novel method for smooth transition in step-up/step-down DC-DC converter

This paper presents a step-up/step-down converter with a novel control scheme based on noninverting buck-boost converter. The control scheme is used to obtain a transition mode and implement smooth transition between buck mode and boost mode. The transition mode is adopted to improve the linearity between the output voltage and the control voltage. With the proposed control method, the output ripple voltage is significantly reduced when the input voltage is close to the output voltage. In addition, this method decreases the complexity in circuit design and enhances efficiency. The step-up/step-down converter has been designed with 0.5µm CMOS process, and can regulate an output voltage within the supply voltage ranged from 2.5V to 5V. The simulation results show that the output ripple voltage in the transition mode is less than 3mV which is smaller than that in the buck mode and boost mode.