Dynamic Range Extension of Schottky Detectors Application Note ...

The compression level can be raised by reducing the value of R L , theload resistance. However, the sensitivity degrades by the factorR L / (R L + R V ) ,where R V is the diode’s video resistance. This degradation in TSSexceeds the improvement in compression, so there is no improvementin square law dynamic range.Another technique for raising the compression level is to increase thebias current. This also degrades the sensitivity, but the improvement incompression exceeds this degradation so square law dynamic range isincreased.Figure 2 illustrates the effect of bias current level on a Hewlett-Packard5082-2751 detector, measured at 10 GHz. The diode impedance wasmatched to the 50 ohm system at each bias level. The tuner wasadjusted at an input level of -30 dBm.-62-2452-58-20TSS50TSS (dBm)-54-50-46-421 dB COMPRESSION POINT (dBm)-16-12-8-4COMPRESSIONDYNAMICRANGE48464442DYNAMIC RANGE (dB)-38040-34+43810 20 40 70 100 200 400 700 1000BIAS (µA)Figure 2. Dynamic Range Improvement with BiasConclusionThe improvement in dynamic range is evident by the increased spacingbetween the TSS and compression curves.For technical assistance or the location ofyour nearest Hewlett-Packard sales office,distributor or representative call:Americas/Canada: 1-800-235-0312 or(408) 654-8675Far East/Australasia: Call your local HPsales office.Japan: (81 3) 3335-8152Europe: Call your local HP sales office.Data Subject to ChangeCopyright © 1975 Hewlett-Packard Co.Printed in U.S.A. 5952-8335 (10/75)