A 1–20-GHz Broadband MMIC Demodulator for Low IF Receivers in Multistandard Applications

This paper presents the design and performance of a 1-20-GHz broadband demodulator for low IF receivers dedicated to multistandard applications. Unlike the conventional in-phase/quadrature (I/Q) demodulator, this circuit uses three paths 120deg phase shifted from one another instead of only two 90deg phase shifted I and Q paths. This feature makes the proposed demodulator less sensitive to phase mismatch and permits to achieve very broadband operation. Demodulated quadrature phase-shift keying constellation diagrams are presented to illustrate our purpose, although in practice our demodulator is not restricted to a particular modulation type. The circuit achieves a measured conversion gain better than -8 dB and its sensitivity reaches -65 dBm at 5.8 GHz. The 2 mm times 3 mm chip was fabricated using the ED02AH process (0.25-mum GaAs enhancement/depletion mode pseudomorphic HEMT) provided by the OMMIC foundry. To the best of our knowledge, this is the first demodulator operating in such a broad frequency range reported to date.