Some fundamental and practical limits on broadband matching tocapacitive devices, and the implications for SIS mixer design
Kerr, A.R.
Microwave Theory and Techniques, IEEE Transactions on
Volume 43, Issue 1, Jan 1995 Page(s):2 - 13
Digital Object Identifier 10.1109/22.363015
Summary:In a given frequency band, the achievable match between a
capacitive microwave or millimeter-wave device and a resistive source is
limited by the capacitance of the device and its series inductance. The
fundamental limit on the match bandwidth is examined for three circuits:
1) parallel RC, 2) parallel RC with series L, and 3) parallel RCL with
series L. The broadband matching theories of Bode (1945) and Fano (1950)
are used, the latter modified to avoid the standard low-pass to
band-pass mapping in case 2) because the terminals of the capacitance
are not generally accessible for connection of the requisite parallel
inductor. The results are fundamental to the design of broadband mixers,
multipliers, switches, and detectors using Schottky diodes or SIS
junctions. Practical limitations imposed by the minimum realizable
dimensions of millimeter-wave integrated circuits fabricated by standard
photolithography are discussed in the context of SIS mixers with series
arrays of junctions, and an example of a coplanar SIS mixer design is
given. For a series array of N devices with a given total resistance, it
is shown that there is an upper limit to N, below which the theoretical
match bandwidth depends only on the RC product of the devices and not on
the series inductance of the array
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