Microwave diode?

Those look good. Skyworks has some really nice low-barrier Schottky diodes. And they have a fabulous sample kit of schottkies and varactors, lots of parts.

Go for "low barrier" parts for unbiased low-level detection.

The best detectors are probably germanium back diodes, but expensive.

Several semi companies now make active detectors... LTC, ADI.

John

Depends which "C-band" those spec sheets refer to: IEEE C-band is about 4 -

And of course ITU C-band is 190.0-197.2 THz.

Cheers,

Phil Hobbs

"1N23B is a point contact silicon diode. For the ages that was the closest thing to Shottkey and the diode for microwave. In a lot of old hardware the newer shottkey diodes will easily replace the

FYI: the suffix specificied specific sorting of 1n23 for noise, working frequency and threshold voltage."

To compare 1N21 to 1N23 go here and download the data.

Graham

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Data on your first part here

Not sure what the suffix means but there's a load of them here.

Graham

Is that similar to the 1N6264 ?

Someone else who doesn't know what a thread is thanks to Google ! Would you mind learning please ?

Graham

There was a thread about this a few months back in s.e.d IIRC.

Graham

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That's a big-junction, high-barrier part, OK for a UHF mixer. But with roughly 1.5 pF of zero-bias capacitance, it's not ideal as a detector at 2.4 GHz.

John

Any idea how well 0.35pF compares with a point contact type ? Googling 1N23B brings up plenty of data including that for the 1N21B but I've yet to see any capacitance figures.

"These point contact "cat's whisker" devices, are still made occasionally because of their very small capacitance. As it was discovered early on, they are highly useful in high frequency electronics."

Graham

My question was off topic - I simply wondered if the two were similar.

Sorry, wrong guy.

John

Hello Dave,

Try bat15 (comes in various packages, single,dual, quad), low capacitance (0.35pF at 0V bias, that is far better then the general purpose hybrid schottky rectifiers, the specify them at, for example,

-0.5V). Video resistance of about 100 kOhm, so you can use it as a zero bias detector when loaded with 1M Ohm or more.

When you want to detect higher voltages, try bat62. This one has some more capacitance, but still a fast diode, with 40V (yes, 40V) reverse voltage. Video resistance is also about 100 kOhms,

When you want high video bandwidth, you should bias them or use special zero bias detector diodes with low video resistance.

Best regards,

Wim PA3DJS

(but

mind

Sorry reply to wrong post.

Graham

how are you going to make a BAT51 fit in the waveguide 1N21B is specified for?

Shfmicro sells diodes in one offs.

Steve Roberts

because

Almost as important as the capacitance, which is covered by the frequency range anyway, ist the case. It should suit the application, meaning the geometry of the mounting. The manufacturers divide into mixer diodes and detector diodes. The detector diodes are specified in terms of mV/uW together with a loading. The loading is connected to the video bandwidth. The higher the bandwidth the lower the load. I'm not too familiar with 2.4GHz, but assume few kOhms would be usual. There are different sort of bias to achieve a high sensitivity. RF of the same frequency, but adjustable phase, DC, none. This usually is given by the setup.

I wasn't yet able to figure out what happens when a zerobias detector is suddenly biased, or whether a DC bias detector can be RF biased.

Rene

(but

because

highly

You know, I picked up all this info when the father of a good friend of mine died. The son let me take some books of his. His father was Anthony Tucker who was a fighter pilot in WW2 in N.Africa.

Later he became the Science Editor for the Guardian (UK) newspaper. He was one hell of a smart guy. I shall never forget him. I even lived with the family as a lodger for a while which is where I picked up most of my environmental clues. He is buried in the grounds of St Albans Cathedral.

Graham

Thanks for all the input.

The project is this:

To the person asking about form-factor: there isn't any. Well, there is concern about strain relief, so if I choose an smt part it should be soldered to a speck of pcb to provide relief.

I looked at the BAT62 part; the datasheets say "up to GHz frequencies", but no specified bw:

Is this a good stand-in for the 1N21B?

Thanks,