Microwave Engineering Europe - November 2008 - (Page 21) MMICs 21 readers may have been omitted. In this case interested parties are invited to contact the authors directly. All of the measurements presented below were made using RFOW probing. An off-chip connectorised balun was used to transform the differential IF signal to single-ended for ease of measurement. Figure 7 shows the measured conversion loss of the mixer in downconvert mode with LO fixed at 28 GHz and the RF swept between 18 GHz and 27GHz (giving an IF output of between 10 GHz and 1 GHz). The results for three representative devices (the solid traces) are plotted showing good device to device repeatability with the conversion loss varying between 7.9 dB and 9.9 dB across the band. This compares favourably with the simulated performance, the dotted trace in Figure 7, which predicted an almost flat conversion loss of around 8.4 dB. Figure 8 shows the conversion loss of the mixer in upconvert mode with the LO fixed at 36 GHz and the IF swept between 0.5 GHz and 17 GHz. The resulting RF output is between 35.5 GHz and 19 GHz. Measured results for the same three representative devices are plotted (the solid traces) along with the original simulated performance (the dotted trace). The measured conversion loss varies between 6.9 dB and 10.4 dB across the band. This compares favourably with the simulated performance, which has a flatter response with conversion loss varying between 8.6 dB and 9.3 dB across the band. The measured s11 at the LO port is plotted for the same three representative devices in Figure 9. This return loss is around 10 dB across the band. Whilst not a perfect 50 W, it is in good agreement with the simulated performance. During the design process this level of return loss was selected as representing a good-trade-off between input match and high LO voltage swing across the gates of the mixer. Figure 9: LO port s11 for 3 MMICs. ISO 9001 : 2000 Delivery in Days • Since 1976 Single Single Layer Layer Capacitors Capacitors • Broadest variety available • Gold or tin terminations • 100pf X7R from 10 x 10 mils • 1,000pf X7R from 30 x 30 mils Mounting Shorts Mounting Shorts • Instant bonding pads • Height matching reduces lead length • Any size available Submounts Submounts • Alumina, Aluminum Nitride, Quartz, Kovar • Custom patterns • Thickness from 3 to 60 mils and beyond New RPS New RPS Rapid Prototyping System for Rapid Prototyping System for Thin Film Substrates and Thin Film Substrates and Copper Laminate Boards Copper Laminate Boards • Direct patterns, no mask required • 48-hour delivery • Single prototype to full production Figure 10: Downconvert conversion loss versus LO power level, LO = 28 GHz, RF = 22 GHz. West Berlin, NJ 08091 e-mail: sales@compexcorp.com 856/335-2277 • fax: 856/335-7223 web: www.compexcorp.com Microwave Engineering ● November 2008 ● www.mwee.com http://www.compexcorp.com http://www.compexcorp.com http://www.mwee.com
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