AoE x-Chpaters - 1x.3 Capacitors

Yes, MEMS variable caps and switches keep getting introduced, but don't seem successful.

Were vacuum capacitors in there ?

I wouldn't design one in, despite the attractively low capacitances. No track record, for one thing, and too many conflicting requirements, for another. Good processing characteristics != good operating characteristics.

Cheers

Phil Hobbs

Al2O5?!

Best regards, Piotr

I think the problem with MEMS switches is that they tend to stick closed. The proposed parts that I've seen had fabulous specs.

Varicaps are cheap and not very microphonic!

Of course poling the cap is going to make the piezo problem much, much worse.

Cheers

Phil Hobbs

Yeah. You have to be able to make the contacts by etching or liftoff, which makes it sort of hard to have the right contact plating for a relay. Also of course the actuators aren't that stiff.

Plus you can use two back-to-back to cancel the even-order nonlinearity. At a fixed frequency you can do pretty well on the odd orders by adding an inductor in series and another in parallel. You resonate the series inductor just off the high-capacitance end, and then resonate the parallel inductor with the series combination just off the low-capacitance end. Makes good phase shifters.

Cheers

Phil Hobbs

From the caption: "The gain-calibrating input signal is replaced by a 0 Ω shorting plug during noise measurement."

IIRC, the fixture is capable of making effective noise measurements below 2.2 ohms.

Am 05.08.2019 um 23:57 schrieb Winfield Hill:

In fig. 1x.51 I missed air capacitors in the fixed section. While rare and expensive, they are commonly used as reference standards. Genrad Type 1404 :)

Greetings from Germany Henrik