Author: Jerng, Albert
Other Contributors: Massachusetts Institute of Technology. Dept. of Electrical Engineering and Information Technology.
Consultant: Charles G. Sodini.
Department: Massachusetts Institute of Technology. Dept. of Electrical Engineering and Information Technology.
Writer: Massachusetts Institute of Technology
Date Issued: 2007
A minimal power, wideband wireless transmitter utilizing [Delta]-[Sigma] direct digital modulation of the RF carrier is presented. The transmitter architecture replaces high dynamic range analog circuits rich in speed digital circuits along with a passive LC bandpass filter, saving power and area when compared with conventional IQ modulators for wideband systems. A prototype transmitter IC built-in .13 pm CMOS demonstrates an information rate of just one.2 Gb/s using OFDM modulation inside a bandwidth of 200 MHz centered at 5.25 GHz. The modulator consumes 187 mW and occupies a die section of .72 mm2. A quadrature digital-IF approach eliminates modulator LO feedthrough and image spurs in the output spectrum without requiring analog circuitry or system calibration, simplifying the style of the transmitter. The biggest modulator spur is measured to become -47 dBc. Measured SNDR on the 200 MHz bandwidth is 43 dB. Effective implementation from the [Delta]-[Sigma] RF modulator requires the style of a higher-Q, tunable RF bandpass filter, along with a low power, high-speed digital [Delta]-[Sigma] modulator. A fourth order passive LC bandpass filter with center frequency of 5.25 GHz was created and implemented using differential coupled resonators.(cont.) Variation from the filter response over process and temperatures are removed through the style of a computerized self-tuning loop that calibrates the filter center frequency somewhere LO.
A Couple.625 GS/s, second order, 3-bit digital [Delta]-[Sigma] modulator is recognized by using a pass-gate adder circuit enhanced for low power and speed. Digital modulator is software programmable to aid multiple bandwidths, frequency channels, and modulation schemes. You can use it adaptively to deliver in selected channels with variable bit-rates, based on funnel conditions. It’s envisioned the [Delta]-[Sigma] digital-RF modulator can be used a universal transmitter for wideband systems and applications that need high data rates and occasional power consumption.
Thesis (Ph. D.)–Massachusetts Institute of Technology, Dept. of Electrical Engineering and Information Technology, Feb 2007.Includes bibliographical references (p. 157-162).
Keywords: Electrical Engineering and Information Technology.