RF transistor amplifier design, any suitable literature?

[Yansi]

Winner winner chicken dinner! Maybe... likely accidentaly... need to have that bastard characterized using better equipment.  (I.e. proper two port VNA, which I do not have access to, yet.)

I was able to get ~9dB of gain from it!

The suicide bias wasn that bad at all. I made an guesstimate about hFE - but close. So from the real circuit measurement, I calculated back the real hFE (was exactly the typical value from the datasheet, go figure!), then calculated the correct base resistor.  Almost bang on, running it at 19mA. (didn't have 21k, used 22k instead).

I should have made a bigger island with more vias on the upper emitter leg. (I hate hate hate the manual wire-through via soldering!) In a proper PCB manufacture, I wouldn't probably hesitate much to via the shit out of the board. But still, it seems to be (likely accidental) success. Even the simulation predicted 9dB of gain.

What I do not know, is the OP1dB of the amplifier.  I do generate the 1627.5MHz  carrier from some very old radio-amateur build. It is very unstable, drifting (amplitude wise, frequency is held precisely by an OCXO ) and I cannot vary the output amplitude finely. I can only stack 4dB pads which I salvaged a handful from old equipment.

What I did found, is the output of the 1627MHz LO is not even close to 50ohms. (which one could guess, based on how the LO output is done).  By connecting the amplifier directly to the LO output, I cannot get the  9dB gain.  If I insert at least one of the 4dB pads before the amplifier, the LO match to 50ohm gets probably better, and then I am able to get 9dB of gain. 

Heck.. how a proper RF generator would be handy!  Unfortunately, this is very out of my skill to build and very well out of what I could afford to buy, for this kind of frequencies. 

Photo, schematic below.


//EDIT: I have added a bunch of BAP64Q  PIN diode quads to shopping cart at Mouser, so probably I could use that to vary (and maybe even stabilize the amplitute of the LO source?)  By making another piece of this amplifier, I could probably get enough power to probably overdrive the amp and make Pin/Pout measurement by fine adjusting the PIN attenuator. ??

[cdev]

That bugs me a lot too! 

Working on getting a better setup where I can drill nice neat measured holes quickly.



Quote from: Yansi on Today at 13:27:40

I should have made a bigger island with more vias on the upper emitter leg.

(I hate hate hate the manual wire-through via soldering!) In a proper PCB manufacture, I wouldn't probably hesitate much to via the shit out of the board. But still, it seems to be (likely accidental) success. Even the simulation predicted 9dB of gain.

[Yansi]

I have no problem drilling more holes. Making some chips or dust is not a problem either, as I have a small machine shop at home, where I do all the electro-mechanicals a small metal working.  I hate soldering the wire jumpers through the board, as it is a very slow and boring process.

Now that a first working amplifier is done, I am not quitting yet, not at all!

For example I completely skipped the stability analysis here. Need to have a look back at the Sonnet Lite and the Ansoft Designer to see, if I will be able to simulate the whole amp including the PCB. And a lot of other things.

At least I am currently a bit more positively "tuned" after this. 

I will take S11 and S22 measurements of the amplifier tomorrow or on Tuesday (using the single port available only, non-calibrated VNA)


I have currently another goal for me to try and test.  Meanwhile I continue to study and experiment with transistor RF amps, for some projects I'd like to build, it would become handy to be able to multiply frequency. For example I have a 814 MHz LO I'd like to multiply by 2 to get the same 1628MHz I have now, and even multiply even that by two to get 3256 MHz. I should probably create a separate thread for RF multipliers, hopefully I don't get accused for spamming the forum with n00b questions too much!

//EDIT: Typos.

[T3sl4co1l]

I have no problem drilling more holes. Making some chips or dust is not a problem either, as I have a small machine shop at home, where I do all the electro-mechanicals a small metal working.  I hate soldering the wire jumpers through the board, as it is a very slow and boring process.

I have some PCB drills that are just the right size for some, whatever it is, 18AWG or so, bare wire I've got laying around.  A little finagling wedges the wire in the hole, then I cut it flat, and pound on the wire a bit, riveting it in place.  Solid riveted vias, what could be better?   (Glommed over with solder, of course.  I don't trust such a crude rivet to hold.)

Tim

[T3sl4co1l]

Just to pick up briefly on the point about noise, 1.7nV/rtHz is indeed a very small voltage by everyday standards. However, the noise from a 50ohm resistor at 290K (the standard reference temperature) is only about 0.9nV/rtHz. So, the noise figure (NF) for your amplifier is about 4.6dB (a noise temperature of about 550K).

LNAs usually have a NF <~1dB (a noise temperature of about 75K).

Yeah, not low as LNAs go, but it's quieter than the other amp that I made specifically for low noise purposes that's two or three times worse...

Tim

[cdev]

When I thread several through at once and then solder them all, one side and then the other, and then chop the tangle of wire off, with sidecutters, I waste a bit more wire but its faster.

[Yansi]

Well, I have currently the smallest drill bit 0.5mm, but using a rather thinner wire, so working multiple wires at once is not possible. it just falls out.

[cdev]

There has to be a better way and we have to find it. Has anybody ever used the little grommets they sell?

[Yansi]

Me personally not, but my friend uses it. It sucks. They are too large. I can make the wire-vias to take very small surface area on the pcb.

[cdev]

I know the inductance of larger diameter plated hollow vias is much lower than smaller ones but I have no idea what changes when the via is solid metal. Another option is a slot, maybe cut with a Dremel, a very thin line, with copper in it. Might be thin enough to solder both sides well in one motion.

I wonder how hard it is to electroplate your own vias? Using graphite and a low voltage power supply.

[Yansi]

I've seen people doing that on YouTube. But my goal is not mastering electrotechnology, but mastering circuit design.  For quick and dirty prototypes or  retro designs from THT components only, I etch the PCBs at home, as the photo-etch-process is quite quick and precise with very repeatable results.  The small PCB for the RF amp takes like about an hour up to hour and a half, from cutting a bare PCB to drilling holes in the finished board.

Currently I am making another piece of the board, that I will use to measure the other one's OP1dB (and the whole Pin/Pout characteristic).  Still I have to wait for the PIN diode attenuator to arrive, or find some PIN quad at home.  I have somewhere a large TV (or satellite?) distribution amplifier, and if my memory serves me right, it was absolutely full of PIN diodes. Maybe I could  bodge an attenuator from those? Mmm. Interesting idea.   

[Yansi]

Found the detailed photos of the TV distribution amp.  There is a fuckton of these diodes.  Marking seems to be AG or A6.

A6 might be BAS16 : https://www.infineon.com/dgdl/Infineon-BAS16SERIES-DS-v01_01-en.pdf?fileId=db3a30431400ef6801141b93811b03ff
But that is a switching diode. Useless for attenuators.

But I suspect the marking to be AG more likely.

EDIT:  AG may be ZMV835A, but varicap diode? I don't think so.  They must be either the switching diodes (but what for in the UHF distribution amp?) or PIN diodes.

EDIT2: Well.. They most probably are the BAS16. Even switching diodes can be used to switch RF (??), but with a rather low off isolation. Hence probably why there are four in series on the photo below!  The configuration seems to be a SP4T switch.

[G0HZU]

Glad it seems to be working a bit better now...  I'm not sure how you are measuring the power level but obviously, you have to be wary of mismatch uncertainty as this can give a fairly wide uncertainty window wrt your gain measurements.

It's a while since I did any formal VCO design but I could probably design a fairly decent narrowband VCO for you at 1620MHz with good phase noise and stability. But it would need soma fairly decent components. But if you want something a bit more average I could make something a bit uglier and cheaper?

[Yansi]

Well, what decent components exactly?  I can take an off the shelf Minicircuits JTOS can packaged VCO, slap that on board and use that. Have some of those here too.
But sure knowing how to design a VCO from discretes would be more interesting for me. If you could for example share some details how to do it (or why and how you did it), you'd be gold! Many thanks!

(Note: I'd probably vote for the cheaper and uglier, to make it from what I have available, rather then buying expensive new stuff).

I can only imagine building a Colpitts oscillator (I have built a bunch of those, but only at VHF), but am not too sure about how these classic topologies stand at these frequencies. Maybe using some quarter wave resonator may be good, but at 1627M, the resonators are pretty large and space hungry.

I have also a bunch of LMX2326 or TSA5055 PLL chips I could use to lock the VCO (either the MiniCircuits can or discrete would be more interesting) and produce a nice 1627 MHz LO.

To measure the power, I use my trusty old Advantest R3131 spectrum  analyzer.  Unfortunately, still don't have any RF generator in my lab, it is on the list to get one. But I can borrow a crusty (not trusty) old Russian one for 1627MHz if necessary. It has a cavity resonator inside and is mechanically tuned.

[Yansi]

So I dug through my document archives and found Infineon AN061: W-CDMA 2.3 GHz VCO using BFR360F and BBY58-02V, which seems to be the closest to what I am looking for.

Also found another interesting book on RF design: Randall W. Rhea, Oscillator Design and Computer Simulation .
And already started reading the book from Chris Bowick, RF Circuit Design. It is the very basics mostly (at least the beginning part of the book, but still good to remind that.

Attaching the VCO schematic from the AN061.

[T3sl4co1l]

Are you sure you get a flat bandwidth up to 700MHz out of that module?

Reply moved to here: https://www.eevblog.com/forum/projects/wideband-amp/msg1299433/#msg1299433

Tim