2.5–7 GHz single balanced mixer with integrated Ruthroff‐type balun in 0.18 µm CMOS technology

An on‐chip Ruthroff‐type balun fabricated in tsmc TM 0.18 µm CMOS technology has been realised and used in a single balanced mixer. By using the phase compensation line and appropriately choosing the characteristic impedance of transmission lines, the balun was realised with a minimum insertion loss of 0.71 dB and the 1 dB bandwidth over a frequency range from 3.2 to 8.4 GHz. The compact size of 0.088 mm 2 is achieved owing to the short length of the transmission line winding, approximately 1/18 λ g , and the adoption of broadside‐coupled and spiral‐shape structures. A simple single balanced mixer with the Ruthroff‐type balun was then designed to demonstrate the capability of the broadband and low‐loss balun. A minimum conversion loss of 12.48 dB with a 3 dB bandwidth from 2.5 to 7 GHz was measured at the LO drive of only 6 dBm. The chip area, including pads, is 0.49 mm 2 .