Tunable Gm-C Filter Research Articles

Design and Characterization of a Digitally Tunable Gm-C Filter for Multi-Standard Receivers

This paper presents the design, simulation, prototyping, and measurement results of a digitally tunable fourth order Gm-C low-pass filter (LPF) for multi-standard radio receivers. The LPF cut-off frequency can be tunned by digitally selecting the transconductance of the basic reconfigurable operational transconductance amplifiers (OTAs) that compose the circuit. Four operation modes allow for control of the OTA transconductances and, consequently, the scaling of power consumption. The filter was designed and prototyped in a 1.8 V 180 nm CMOS process. The measurement results indicate that the configurability provides a cutoff frequency of 1.90/3.56/6.07/8.15 MHz with a power consumption ranging from 9.9 to 13.1 mW. The designed filter achieves an IIP3 of 8.17 dBm for a signal bandwidth of 8.15 MHz. The performance, in terms of power dissipation, noise, and cut-off frequency, is at the same order of magnitude compared to recent related works reported in the literature. The advantages are a compact area, small sensitivity to component mismatches, and low design complexity. The proposed filter presents electrical characteristics suitable for the application in radio receivers for multi-carrier WCDMA signals.

Design and simulation of tunable low-pass Gm-C filter with 1 GHz cutoff frequency based on CMOS inventers for high speed telecommunication applications

A tunable low-pass Gm-C filter with 1 GHz cutoff frequency is presented. The core of this filter is a high frequency low voltage operational transconductance amplifier (OTA) in which CMOS inverters...

0.3V Tunable OTA and Gm-C Filter in 0.13µm CMOS

This paper presents an ultra-low-voltage operational transconductance amplifier (OTA) and Gm-C filter, both working with 0.3V single supply voltage. Using pseudo-differential structure, the common mode rejection is the main challenge in low voltage condition which is overcome by a new common mode feedback circuit. The OTA can be tuned through the gate terminal of body-driven PMOS input transistors. Post-layout simulation shows 23.4 dB differential gain and 47.4 dB CMRR at low frequencies. By changing the tune voltage from 50mV to 0V, the OTA's transconductance can be tuned from 7.9 to 17.4 uA/V. By applying input voltages up to 0.36 Vpp, the THD of output current remains less than -60 dB. The proposed OTA is employed to implement a tunable low-pass Gm-C filter. The cutoff frequency of Gm-C filter can be tuned from 1.13 to 1.9 MHz that makes it applicable in the multi-standard direct conversion receivers as channel selection filter. The power consumption of filter is 111.3 uW and its input referred voltage noise is 168.7 nV/sqrt(Hz), as results of post-layout simulations. The post-layout simulation shows the IIP3 of 8.5 dBm for the cutoff frequency of 1.9 MHz.

Adaptive cancellation linearisation and its application to wide‐tunable Gm‐C filter design

This paper presents an adaptive g m3 cancellation for linearisation of operational transconductance amplifier (OTA) and its application to design of a wide tunable Gm-C filter. g m3 cancellation through paralleling triode- and subthreshold-mode transconductors makes good linearisation, but only in a limited range of tuning voltage. An auxiliary circuit is employed to adaptively change the operating point of subthreshold-mode transconductor such that to keep linearisation throughout the tuning range. By this way, the linearity of OTA is significantly improved in overall transconductance tuning range from 18 to 289 μA/V. While by applying 0.6 Vpp input voltage at 1 MHz the total harmonic distortion (THD) of conventional OTA lies between -75.1 and -44.4 dB, it reduces to lie between -83.3 and -57.4 dB in the proposed OTA. Using the proposed OTA, a third-order low-pass Gm-C filter is designed in 0.18 μm CMOS technology. The cutoff frequency of filter is tunable from 1.73 to 27.25 MHz, thus, can be applicable to support WCDMA, WLAN (IEEE 802.11a/b/g/n) and WiMAX standards in multi-mode direct conversion receivers. The third-order intercept point of filter is between 7.1 and 13.7 dBm in different tuning conditions.

A low-noise widely tunable Gm-C filter with frequency calibration**Project supported by the National Natural Science Foundation of China (No. 61574045).

A fourth-order Gm-C Chebyshev low-pass filter is presented as channel selection filter for reconfigurable multi-mode wireless receivers. Low-noise technologies are proposed in optimizing the noise characteristics of both the Gm cells and the filter topology. A frequency tuning strategy is used by tuning both the transconductance of the Gm cells and the capacitance of the capacitor banks. To achieve accurate cut-off frequencies, an on-chip calibration circuit is presented to compensate for the frequency inaccuracy introduced by process variation. The filter is fabricated in a 0.13 μm CMOS process. It exhibits a wide programmable bandwidth from 322.5 kHz to 20 MHz. Measured results show that the filter has low input referred noise of and high out-of-band IIP3 of 16.2 dBm. It consumes 4.2 and 9.5 mW from a 1 V power supply at its lowest and highest cut-off frequencies respectively.

A new controllable adaptive biasing linearization technique for a CMOS OTA and its application to tunable Gm-C filter design

This paper presents a new linearized operational transconductance amplifier which uses a fully controlled adaptive biasing scheme. The differential input voltage is sensed through a squarer circuit and is compared with a controllable reference voltage to create appropriate auxiliary tail currents. The proposed adaptive biasing circuit can be adjusted to make best linearization for each tuning condition of OTA. While the adaptive biasing circuit consumes a little portion (about 13%) of the total power consumption (about 475μW), it significantly reduces the third-order nonlinearity of OTA׳s output current in whole of its tuning ranges. By applying a two-tone 0.6Vp-p input voltage at 20MHz, IM3 is degraded by more than 13dB throughout the transconductance tuning range from 8.2μA/V to 47μA/V. Proposed OTA is employed to implement a wide tunable Gm-C filter. The cutoff frequency of low-pass filter is tunable from 584kHz to 10.6MHz, thus, it covers several standards of wireless applications. IIP3 of filter is 22.3dBm, 19dBm and 17.4dBm, respectively, for Bluetooth, UMTS and IEEE 802.11a/g standards. The OTA and Gm-C filter are designed and simulated in 0.18-μm TSMC CMOS technology with Hspice simulator. Monte Carlo and corner case simulations show the good robustness of proposed circuits against the fabrication errors.

A 0.9 V Supply OTA in 0.18 μm CMOS Technology and Its Application in Realizing a Tunable Low-Pass Gm-C Filter for Wireless Sensor Networks

A low voltage low power operational transconductance amplifier (OTA) based on a bulk driven cell and its application to implement a tunable Gm-C filter is presented. The linearity of the OTA is improved by attenuation and source degeneration techniques. The attenuation technique is implemented by bulk driven cell which is used for low supply voltage circuits. The OTA is designed to operate with a 0.9 V supply voltage and consumes 58.8 μW power. A 600 mVppd sine wave input signal at 1 MHz frequency shows total harmonic distortion (THD) better than -40 dB over the tuning range of the transconductance. The OTA has been used to realize a tunable Gm-C low-pass filter with gain tuning from 5 dB to 21 dB with 4 dB gain steps, which results in power consumptions of 411.6 to 646.8 μW. This low voltage filter can operate as channel select filter and variable gain amplifier (VGA) for wireless sensor network (WSN) applications. The proposed OTA and filter have been simulated in 0.18 μm CMOS technology. Corner case and temperature simulation results are also included to forecast process and temperature variation affects after fabrication.

Ultra low voltage, high performance operational transconductance amplifier and its application in a tunable Gm-C filter

This paper presents an ultra low voltage, high performance Operational Transconductance Amplifier (OTA) and its application to implement a tunable Gm-C filter. The proposed OTA uses a 0.5V single supply and consumes 60μw. Employing special CMFF and CMFB circuits has improved CMRR to 138dB in DC. Using bulk driven input stage results in higher linearity such that by applying a 500mvp–p sine wave input signal at 2MHz frequency in unity gain closed loop configuration, third harmonic distortion for output voltage is −46dB and becomes −42.4dB in open loop state for 820mvp–p output voltage at 2MHz. DC gain of the OTA is 47dB and its unity gain bandwidth is 17.8MHz with 20pF capacitance load due to both deliberately optimized design and special frequency compensation technique. The OTA has been used to realize a wide tunable Gm-C low-pass filter whose cutoff frequency is tunable from 1.4 to 6MHz. Proposed OTA and filter have been simulated in 0.18μm TSMC CMOS technology with Hspice. Monte Carlo and temperature dependent simulation results are included to forecast the mismatch and temperature effects after fabrication process.