Design and Characterization of D-band Monolithic Direct Carrier Modulator and Demodulator Circuits for High Speed Wireless Communication

Licentiate thesis, 2014

Millimeter waves are finding increasing applications in data communication, sensing, imaging and radio astronomy. One application is in high-speed wireless back-haul networks for mobile communication. The operators are interested in replacing optical fiber with the more flexible and easy to deploy wireless link. This substitute should provide the high capacity which is inevitable for the next generations of mobile standards and also be lightweight and low power to be practical. These requirements together with the expected high market volume of the point-to-point links mandates implementation of the radio front-end on a single semiconductor chipset. This thesis discusses how the direct carrier conversion greatly simplifies the radio front-end and therefore is an attractive alternative for single-chip integrated radio implementation at millimeter-wave. For demonstration, design and characterization of two monolithic direct carrier quadrature modulator and demodulator circuits operating at 110 GHz to 170 GHz will be presented. The circuits are fabricated in 250 nm InP Double Heterojunction Bipolar Transistor (DHBT) technology with ft/fmax of 350/600 GHz and have all the active and passive components integrated into them in a compact size. The modulator has a measured conversion gain of 6 dB with more than 22 dB and 27 dB suppression of sideband and LO tones, respectively at the output. It can provide up to 3 dBm of RF power and has an output third order intercept point of 4 dBm while consuming 78.5 mW dc power. The demodulator circuit has 14 dB of conversion gain, more than 25 dB of image rejection and saturated output power of 4 dBm. The RF bandwidth is from 110 GHz to 170 GHz and has SSB noise figure of 11.5 dB over the LO frequency from 110 GHz to 170 GHz. It consumes 74 mW of DC power. All measurements of both the converters are done at 0 dBm of LO power. The active chip area of each converter including RF and LO balun is 560 μm_ 440 μm.