23cm PA using Ericson PTF10137 surface mount device
23cm amplifier was required that would produce a few watts from a 12v
supply. Fortunately, a number of Erikson surface mount PTF10137 devices
were made available at about this time, so it was thought worthwhile to
give them a try.
sheet shows this to be a 1 GHz 12W part, operating from a supply of
28v, with a gain of 18 dB.
A pcb was drawn up from the data
sheet test board drawing, but shortening the lines by a factor of
960/1296, and initially fitting capacitors likewise scaled down -
crude, but quite effective in this case. Added to the board was a
simple 5v regulator to supply a bias pot to set the Idd for the device
(these are LDMOS devices, so require a positive bias to turn them on).
0.8mm Teconic RF-35 material was used
Since I cannot produce plated-thru holes, an alternative
method of applying the device the required. It's not obvious from the
photo, but actually, a hole was cut in the board so that the device
could be dropped through. The base of the device is 0.8mm below the
height at which the pre-formed gate and drain leads leave the package,
so it is convenient to solder a thin (1mm) copper plate to the bottom
side of the pcb, and solder the device slug (the source connection) to
this. It requires the pre-formed leads to be straightened, but they
seem quite malleable, and no problem arose doing this.
Ground interconnects are made using 0.8mm conical track pins
available through Farnell (114-3879).
Board Track pattern
The input match was quite close to being correct with the initial value of line shunt capacitor fitted, and gain was already greater than 10 dB with a 12.5v supply. Initially, Idd was set to 150 mA. A trimmer C was then used to replace the output line shunt C, and with this a gain of 16 dB was obtained with a 1dB output compression power of 4W. A fixed value 2p2 chip C was then used in place of the trimmer, and gave similar results. Gain flatness and input return loss are shown below:
Increasing the supply rail to 15v resulted in a 6W 1 dB
compression power level.
The noise figure at 1296 MHz is 4.4 dB.