Lumped elements (capacitors, inductors, transformers) would be more compact than using transmission lines. You are at a pretty low frequency which is making your transmission lines physically large. There may be alternative distributed networks that are more compact than what you are doing. Lots of PA designs have been published online for similar frequencies so you should be able to find some examples.
Yes, this is low enough frequency (800 MHz) that lumped components will almost be smaller than transmission line stuff (unless you're using a super high epsilon substrate, but that's kind of pricey).
You'd want to watch the power dissipation in any compact design. The currents can get kind of high in a high Q matching circuit.
You need to use lumped elements to make the network more compact as others have said, but have you looked at the vendor datasheet for an example layout? Is that more compact than what you have?
Another option is to use a high Dk substrate to reduce the size of the transmission lines.
I will. The design from the vendor is also long at the output side but is curved and I think the design also implement two lumped shunt capacitors (as you mentioned). I am using the same substrate the vendor use (RO4350B).
Any time someone says "compact" you need to think about thermal issues. You can probably design/build a lumped network (since you don't have a bandwidth requirement) that gives whatever match you want, but the circulating currents might be so high that even small losses would cause hot parts. Consider that a 1% loss (0.04 dB) is a Watt of dissipation. And a tiny 0604 part probably can't handle that.
And consider that the temperature coefficient of your parts might be high enough that the values shift as it gets warm/hot. Such are the challenges of high power amplifier design.
The other thing to consider is whether your matching networks need to tolerate mismatch on the other port - Matching 1 ohm device output impedance to 50 ohms resistive is one thing, but what happens when your amplifier is shorted or open circuit? Do the voltages or currents go awry? Maybe your part tolerates that (lots of semiconductor amplifier MMICs advertise "works into any load" with a video of someone shorting it with a screwdriver intermittently), but maybe it doesn't.
Use high Q RF inductors from Coilcraft and parallel-up some ceramic C0G capacitors. You can use high-end ATC capacitors, but they don't buy you that much - their ESR is about half of normal caps. Parallelling more capacitors also reduces ESL which is what you want. Anyway, that's what you generally find in compact designs like power modules (open up a Mitsubishi one to learn from it), radios, etc.
I haven't established a specific Bandwidth requirement yet. I am focusing on a narrowband design. I used the series inductor and shunt capacitor matching network generated by AWR impedance matching tool on both the input and output and then covert it to microstrip lines.
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u/mightyohm 5d ago edited 5d ago
Lumped elements (capacitors, inductors, transformers) would be more compact than using transmission lines. You are at a pretty low frequency which is making your transmission lines physically large. There may be alternative distributed networks that are more compact than what you are doing. Lots of PA designs have been published online for similar frequencies so you should be able to find some examples.
Can you tell us more about your application?