Aravind Heragu

A Low Power BAW Resonator Based 2.4-GHz Receiver With Bandwidth Tunable Channel Selection Filter at RF

A low power sub-sampling multi-channel 2.4-GHz receiver front-end is presented. Bulk Acoustic Wave (BAW) resonators which intrinsically exhibit high quality factor (Q) are exploited in the frequency synthesis to provide low phase noise signal with low power consumption. A low power solution to perform channel selection and filtering directly at RF by employing current reuse and using a BAW resonator is proposed. The filter is capable of tuning the bandwidth and thus making the front-end to be suitable for multi-band/multi-standard applications. The overall performance of the front-end is improved by additional discrete time filtering which also down-converts the wanted channel to baseband in quadrature. The proposed front-end is designed and integrated in a 0.18-μm CMOS process. Measurements reveal that the front-end is capable of providing very narrow band filtering down to 300 kHz. The rejection at 10-MHz offset is 62 dB with conversion gain of 44.2 dB.

A concurrent quadrature sub-sampling mixer for multiband receivers

A quadrature sub-sampling direct conversion mixer capable of sampling two or more bands concurrently using a single sampling frequency is presented. The implementation of the mixer to sample a band in quadrature and downconvert it to baseband is discussed and it is shown how this idea could be extended to sample in quadrature two or more bands concurrently. The proposed circuit is analyzed in detail and the results are validated using Spectre RF simulations for a 0.18μm CMOS process.

Complementary BAW oscillator for ultra-low power consumption and low phase noise

A BAW based parallel resonance oscillator employing cross-coupled complementary structure is presented for applications requiring ultra-low power consumption and good phase noise performance. Compared to the differential NMOS structure, this circuit offers about 50% reduction in power consumption along with a significant improvement in the thermal noise performance. By the use of proper design considerations, the flicker noise behavior can be optimized. The power consumption in the case of such an oscillator (designed in CMOS 180 nm process) employing a 2.497 GHz BAW resonator is around 675μW for an amplitude of 300 mV with a phase noise of −140dBc/Hz at 1 MHz offset.

A 2.4 GHz MEMS based sub-sampling receiver front-end with low power channel selection filtering at RF

A sub-sampling RF front end which exploits the intrinsically high quality factor of MEMS devices for performing channel filtering directly at RF is proposed in this work. This narrow band filtering at RF also acts as a good anti-aliasing filter to support down-conversion by sub-sampling. The RF front end employs current reuse for amplification, mixing and filtering. A low phase noise BAW based DCO is used as the reference clock for channel selection and sub-sampling. The front end is integrated in 0.18 μm CMOS process and it exhibits up to 300 kHz bandwidth filtering at RF with 44.2 dB conversion gain and 62 dB rejection at 10 MHz offset from the center frequency.

The Design of Ultralow-Power MEMS-Based Radio for WSN and WBAN

Transceivers for wireless sensor networks (WSN) and wireless body area networks (WBAN) require both extreme miniaturization and ultra-low-power dissipation in order to be seamlessly integrated virtually everywhere and enable ubiquitous connectivity among persons, objects, machines and the environment. The miniaturization challenge can be addressed with a combination of system-on-chip (SoC) and system-in-package (SiP) approaches to build an ultra-compact transceiver. The confined space is also limiting the available energy, which raises several design and system issues that could severely affect the radio robustness to interferers, the link budget and the autonomy. This paper presents how innovative narrowband radio architectures devised to take advantage and circumvent the limitations of a few well-chosen MEMS devices can address the above issues and go beyond the existing solutions both in terms of miniaturization and power dissipation reduction.

A low power 2.4 GHz front end with MEMS lattice based channel filtering at RF

In this work, a sub sampling receiver front end at 2.4 GHz with high Q filtering to perform channel selection at RF is presented. A low power solution for channel selection directly at RF is proposed in this work using “pseudo-self-biased” inverter amplifier with a BAW resonator lattice as a load to realize high selectivity. This work focusses on the Bluetooth LE standard, however the front-end can be used for any protocol standards for radios working at 2.4 GHz. A low power BAW based digitally controlled oscillator (DCO) is used as a reference to a LC PLL to perform channel selection. An integer divided version of the BAW DCO signal is used as clock for the sub-sampler to down-convert the selected channel from “super-high IF” to baseband in quadrature. The proposed architecture is designed in 0.18µm CMOS process and validated using ELDO-RF simulations.

Analysis of ultralow-power asynchronous ADCs

In this paper, analysis of a novel class of A/D converters based on asynchronous delta modulation (DM) is presented and a high level model is realized for the same. Using the high level model, analytical expressions are derived for the calculation of the inband signal-to-quantization noise ratio (SQNR) for the case of sinusoidal inputs and two-tone inputs. For the special case of sinusoidal inputs, an empirical formula is also derived for calculating the inband SQNR. The derived analytical and empirical expressions are verified using high level simulations and the simulation results are presented finally.

Ultra low-power MEMS based radios for the IoT

The start-up phase of the radios is responsible for the major energy drain in duty cycled Internet of Things (IoT) nodes. The main source of this energy drain is the long start-up of the loop based frequency synthesizer; especially the crystal oscillator (XO) frequency reference. In order to greatly reduce this energy drain, this paper presents radios based on micromachined Bulk Acoustic Wave (BAW) resonators that have the capability to start in few μs as opposed to ≈ 1 ms start-up of the traditional XO. In addition, these resonators also have a high Quality factor (Q). This results in the oscillators employing these resonators having excellent phase noise, thereby aiding the development of loop-free frequency synthesizers. The high-Q has also been leveraged to make a very good high frequency filter that has been employed in the sub-sampling receiver presented in this paper.

A MEMS-based 2.4-GHz sub-sampling RF front-end for advanced healthcare applications

This work presents a Bulk Acoustic Wave (BAW) resonator based 2.4-GHz front-end compliant to the Bluetooth LE standard and targeting advanced biomedical applications. A new transceiver architecture is proposed that combines BAW resonators and a sub-sampling architecture. It takes advantage of the high-Q of BAW resonators to perform channel filtering directly at RF. At the same time it also carries-out the critical anti-alias filtering required by the subsequent sub-sampling down-conversion mixer generating quadrature samples of the selected channel at baseband. The high-Q resonator is also used in the frequency synthesis to provide a low phase noise reference clock. The front-end has been designed and integrated in a 0.18-μm standard CMOS process and the principle is validated with simulations and measurement results.

A multiband concurrent sampling based RF front end for biotelemetry applications

A sub-sampling based multiband RF front end suitable for medical telemetry applications is presented. Using a single inductor and a single sampling frequency it is shown how to downconvert concurrently Bluetooth LE and MICS band signals to baseband with relative attenuation of 42 dB between the two downconverted bands. The proposed front end is analyzed in detail and the results are validated using Spectre RF simulations for a 0.18µm CMOS process.