Seb Holzapfel

About a month ago I was frothing over a datasheet for a (pretty expensive) PLL synthesizer by Analog Devices, the ADF5355. It's capable of spitting out signals from 50MHz to 13.6GHz - widest I've seen!. It's got a VCO parked between 3.4 and 6.8GHz and internal dividers & doublers. Naturally, I requested some free samples of the $100 AUD (!!) part, to evaluate it - might be useful in a future project.

I then designed a board to house it - for a few reasons. Firstly, great practice for RF routing. Also, a good opportunity to create part

Recently I've been working on a project for which I needed a 14GHz double-balanced mixer, however I'm on an extremely tight budget.

Luckily, most manufacturers provide free silicon samples these days, and Linear Tech (or rather, Analog Devices these days) is no exception. The LTC5548 is a pretty awesome MMIC, DC-6GHz IF, 1-12GHz LO, and 2-14GHz RF. It also includes a buffer so that you can use LO powers around the 0dBm mark instead of an ordinary mixer which might require.

Unfortunately, the evaluation board for the chip costs hundreds of dollars (~$300!) and I need multiple for my experiments.

Or perhaps 'How to make a microwave filter for $0'. Yesterday afternoon I wanted a 1.2GHz filter for an experiment, didn't need anything super-performant, and didn't want to spend any money. Before I actually show you what the filter looks like (because it's hilariously ugly), here's it's response (0-2GHz sweep):
Okay, the frequency response isn't so bad, but I'm putting -10dBm in so we've got about 10dB of insertion loss which isn't great. 300-600MHz seems to seep through at around -40dBc, which is surprisingly not bad. Here's the setup:
So you can see from the tuning scale that the

Alright; I've been sitting on the same old website theme for the last couple of years, so I figured it's about time to change...

Been sitting on this for a couple of weeks and slowly migrating all of my old content over. I think I've fixed most things now; so this new site's now live!

I've completely changed tech and moved over to the much sexier (in my opinion) Ghost blogging engine, with a heavily modified version of it's normal themes with some alterations to allow for my static content.

Annoyingly I couldn't import any of the comments from my

Get the source here. Make sure to compile with ‘ghc fdtd -O2′ otherwise it’ll be insanely slow (Will be profiling for space leaks, probably switching to discrete array constructs in the future).

A few weeks ago, I came across an article on Hackaday about memory mapped IO, and the sorts of toggle speeds you can achieve on the Beaglebone’s output pins when using this technique as opposed to just using the file access API. Around the same time, I was reading some articles on Pulse Density Modulation (as opposed to Pulse Width Modulation) for another project I was working on; in an attempt to increase the slew rate of a low-pass filter on the output of a microcontroller I was using.

As it happened, I’d had this old Dick Smith