Design of microwave mixers

Abstract

This report presents a novel fundamental single-balanced ring mixer design. Incorporating recently developed T-Shaped Compact Microstrip Resonant Cells (TS-CMRCs) and compact Dual Band Stubs (DBS), we can provide proper terminations for the IF, RF and LO signal simultaneously in addition to all major unwanted mixing products, leading to a unique low-conversion loss design. The measured minimum single side-band (SSB) down-conversion loss of 3.3 dB is achieved for a 10.4 GHz RF signal and is better than 6 dB from 9.6-11.5 GHz with a 0.1 GHz IF. Compared with others reported mixers and commercial products, this design has achieved 5 dB better on the conversion loss, indicating an improvement of more than threefold. In addition, our working prototype demonstrates an unparallel advantage in linearity response, in which the thirdorder intercept point (IP3) is +17 dBm with a spurious free dynamic range of more than 55 dB. This mixer provides a superb performance in a very simple manner, making it viable to many modern wireless communication systems. A high-performance X-band sub-harmonic self-oscillating mixer (SOM) is proposed. By using a reconfigurable transistor pair in conjunction with an open and a short circuit stubs, the proposed SOM is capable of down converting four RF frequency bands with center frequencies at 7.35, 8.65, 11.35 and 12.65 GHz with a conversion gain ranging from 7.83 to 18.7 dB. The measured phase noise of the free-running oscillation is –85.4 dBc/Hz at an offset frequency of 100-kHz. With injection locking, the phase noise is reduced to less than – 100dBc/Hz at 10-kHz, without affecting the conversion gains. This is the first demonstration of a multi-band sub-harmonic SOM.