Analysis and Design of a Rotary Travelling-Wave Oscillator for Integration in a Microwave Phased-Array Transmitter

The design methodology and phase noise analysis of a multiphase bipolar Ku-band Rotary Travelling-Wave Oscillator (RTWO) is presented. Lack of symmetry in an RTWO can result in oscillation in an unwanted mode rather than travelling-wave mode. In order to determine the oscillation mode and also measure the phase shift, we have proposed a frequency domain phase shift measurement technique, intended for an 18 GHz RTWO, which is presented. Using a 0.25 μm BiCMOS process from NXP Semiconductors, the fabricated RTW-VCO gives access to eight different phases in steps of 45 degrees and achieves a tuning range of 1.2 GHz centred at 17.5 GHz. A beam-forming technique that utilizes the RTWO for LO phase shifting is also presented. In order to configure a two-element-array transmitter to show the functionality of an RTWO for beam-forming, we have designed and characterized a high frequency distribution network, a switching bank, a power amplifier (PA) and also a patch antenna. All of these components, except the antennas, have been integrated on a single, 19 mm2, silicon die along with the RTWO. The measurement of the full system is performed with the aid of two off-chip antennas fabricated on a high frequency printed circuit board. The combined system is fully functional and the measurement results are provided. This research demonstrates the relevance of the RTWO for integration in phased-array transmitter systems.