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<span style="font-size:12.0pt; font-family:"Arial",sans-serif; color:black">It is good that Atsushi Maeda found the difficultly to be only that of misidentifying a component.<span style="">
</span>90-degree PDNs are very INSENSITIVE to component tolerance variations (because they have only real-valued poles).<span style="">
</span><span style=""> </span>A moderate amount of care should assure a near-nominal performance – they just work – no tweaking.<span style="">
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<span style="font-size:12.0pt; font-family:"Arial",sans-serif">An exception to this rosy picture occurs when we use an extremely large bandwidth to minimize end phase errors – say 5000:1.<span style="">
</span>The poles have a corresponding spread and so do the RC products of the individual sections.<span style="">
</span>In attempting to keep resistors in a range of perhaps 5.1k to 100k, capacitors may spread outside a corresponding desired spread range of perhaps 330 pfd to 0.05 microfarad (too small means stray capacitance matters, too large that caps are physically
too large).<span style=""> </span>Happily I found some 30 years ago that by pairing the poles, largest to smallest, using 2dn-order secions nsead of first, the spread range is reduced to near unity.<span style="">
</span>See:</span></p>
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<a id="LPUrlAnchor_15411234973900.9855665940552767" href="http://electronotes.netfirms.com/EN168-90degreePDN.PDF" target="_blank" style="text-decoration:none">LARGE SPREAD OF CAPACITOR VALUES; - Netfirms</a></div>
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THE DESIGN OF WIDEBAND ANALOG 90° PHASE DIFFERENCING NETWORKS WITHOUT /\ LARGE SPREAD OF CAPACITOR VALUES;-by Bernie Hutchins INTRODUCTION: The design of wideband 90° phase differencing networks is fundamental to the</div>
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<span style="font-size:12.0pt; font-family:"Arial",sans-serif">This discussion along with several related entries is on the Electronotes site as misc. items.
<span style=""> </span>As a bonus, you cut the number of op-amps<span style="">
</span>in half.<span style=""> </span>Only reasonable way to design these – or so it seems to me.</span></p>
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<span style="font-size:12.0pt; font-family:"Arial",sans-serif">Bernie<span style="">
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