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While it is possible to get 25 mW from an MAR-8 MMIC amplifier on this band, many people don't like this device due to stability problems, though it is possible to put an MAR-7 in front of it and stabilize it without losing output power. The 1104 MMIC is rated at 17.5 dBm for 1-dB compression at 0.5 GHz, but is under 16 dBm at 2 GHz on a rapidly falling curve (which looks like it would be around 14 dBm with extrapolation to 2.3 GHz). It is obvious that there is a pretty bad mismatch at both the input and output ports if you look at the S parameters. Thus, I expected to restore much of its performance just by tuning the input and output lines. As Table 1 indicates, this is indeed the case.
Construction
I made an open box by soldering 0.025-inch-thick brass walls to the top and bottom ground foils. I used SMA connectors on the input and output to get a repeatable interface. These are attached to the 1/2-inch-high brass walls with 2-56 screws. Very short leads with Teflon coax will work on 2304, but the results aren't as consistent. The ground leads of the MMICs are bent against the body of the device and soldered to the ground plane. The prototype didn't have a pad for the RF choke-it just went to a chip capacitor soldered to the top ground foil. The bias resistor is shielded by the ground plane. It is hooked up to the choke though a small hole with the ground foil cleared away. The board material is 1/32-inch Teflon with a dielectric constant of 2.55.
Fig 1-Component placement diagram for the 13-cm amplifier.
|
Fig 2 -- Etching patters for the 13-cm amplifier |
| Table 1-2304 MHz power output test | |
| Pin | Pout |
| (dBm) | (dBm) |
| 0.0 | 7.17 |
| 5.0 | 12.17 |
| 6.0 | 13.17 |
| 7.0 | 13.83 |
| 8.0 | 14.83 |
| 9.0 | 15.67 |
| 10.0 | 16.33 |
| 11.0 | 17.00 |
| 12.0 | 17.67 |
| 13.0 | 18.17 |
| Table 2-Frequency response test | |||
| f | Pin | Pout | Gain |
| (MHz) | (dBm) | (dBm) | (dB) |
| 432 | -0.33 | 8.17 | 8.50 |
| 903 | -0.17 | 6.17 | 6.34 |
| 1152 | -0.17 | 6.17 | 6.34 |
| 1300 | 0.17 | 7.33 | 7.50 |
| 2160 | -0.33 | 7.17 | 7.34 |
| 2300 | -0.67 | 7.00 | 7.67 |
| 2700 | -0.67 | 2.67 | 3.34 |
Fig 3 -- Microwave Harmonica source file
|
· MSA1104 at 2304 MHz
· Tune input and output for · good return loss/SWR · file \mh\1104amp.ckt
W50:85MIL
blk
trl 1 2 w=w50 p=300mil sub1
ost9w=wis2 p=pis2 sub1 ost 11 w=wis2 p=pis2 sub1
two 10 20 110 MSAll
cross 20 25 30 35 wl=30mil w2=wos1 w3=wol w4=wos1 sub1 ost25 w=wos1 p=pos1 sub1 ost35 w=wos1 p=pos1 sub1 trl30 40 w=wol p=pol sub1
cross 40 45 50 55 w1=wol w2=wos2 w3=w50 w4=wos2 sub1
ost 45 w=wos2 p=pos2 sub1
slc 50 65 1=0.3nh c=10pf q=15 f=2.3ghz trl65 70 w=w50 p=300mil sub1 amp: 2por 1 70
end
data
|
Fig 4 -- Microwave Harmonica output
MICROWAVE HARMONICA PC V5.5 File: \mh\1104amp.ckt 31-JUL-93
2 3 : 03 : 0 4
| Freq GHZ | MS11 dB AMP | MS21 dB AMP | MS22 dB AMP | K AMP |
| 2.000 | -18.932 | 8.46 | -21.660 | 1.05 |
| 2.300 | -24.963 | 7.81 | -19.926 | 1.07 |
| 2.500 | -20.156 | 7.34 | -25.525 | 1.08 |
