Executive Summary : | Wireless receivers are used in all present day communication and Internet-of-Things (IoT) applications. They are also widely used in health care for monitoring vital signals in patients and industrial quality control applications . Ultra wideband sampled downconversion receivers are also used in automotive and military radar applications. Present wireless receiver systems typically contain atleast a couple of signal processing and downconversion stages before digitizing the input signal into in-phase (I) and quadrature phase (Q) data. Such a system contains multiple local oscillators (LO), mixers and filters. These blocks consume a lot of power. Besides, periodic intervention is required to tune these blocks to maintain adequate performance. This requires additional on-chip tuning which needs more area and power. So the fewer the number of blocks in the system chain, the better. The last stage of downconversion, filtering and digitization can be replaced by a wide bandwidth analog-to-digital converter (ADC). Such an ADC should have a bandpass transfer function, where only the inband signal is digitized, while the out-of-band signals are filtered out. As digital technology has matured rapidly over the past two decades, further processing of the digitized data becomes easier and less prone to aging effects. We thus propose the development of an advanced, robust, wideband ADC which can directly sample the input signal without the requirement of downconversion. The wireless receiver signal chain will now contain the antenna, a low noise amplifier and the direct conversion, wideband ADC. The Bandpass Continuous-Time Delta Sigma Modulator is an ideal candidate for such an ADCs because of its resistive input impedance, which makes it easier to drive and inherent anti-aliasing. However, large inductors are necessary to implement the bandpass transfer function, which makes them infeasible. This problem is addressed presently using an active integrator as a substitute for the inductor. However, the use of active elements introduces nonlinearity and also, consumes power. We propose the use of switched-RC N-path filter to implement the bandpass transfer function in the ADC. This results in a compact and linear solution. This project will be executed in two steps. Firstly, we will model the ADC in MATLAB/Cadence to verify the functionality. Once the architecture is verified, we will move to the circuit design and layout of the ADC. After the successful design, the ADC will be sent for fabrication. In the new design, we expect a 2X and 3X reduction in area and power respectively, compared to the existing state-of-the-art. The experience gained from this design will be very useful for successful design of VLSI circuits in the future. Computer workstations will be procured for students/scholars/fellows to work on the project and a new Analog and Mixed Signal Laboratory will be setup at IIT Roorkee. |