A Single Board No-Tuning 23
"C" wires to provide a low-impedance
ground. Plated-through holes would
eliminatethis step. After preparingthe
boardwith its "C" wires,mount the chip
capacitors, inductors and connectors.
Careful measurementsshow a mixer conFinally, install the MMICs and bias
versionlossof 5.5 dB. The output for l-dB
compressionis 0 dBm. LO suppressionis
The bottom of the hairpin U is a lowimpedancepoint for signalsin the filter
about 25 dB. The mixers compare favorSystem Block Diagram
A bypasscapacitorat that point
ably with more-expensivepackaged units.
Fig 35 is the transverter block diagram
Transmit output is about 13 dBm, which
has little effect on the filter passbandbut
providesa ground path for VHF signals.
and Fig 36 is the schematic diagram. Fig is suitable for some applications without
37 showsthe layout of the 5- x 7-inch G-10 further amplification. A major advantage Although 22-pF capacitorsare specified,
board with all functional blocks labeled. In of the MMIC output stageis that it offers valuesfrom 12to 30 pF gavegood results
the transmit path, FLI removes the image, an unconditionally stable, near-50-ohm in the prototypes.
LO (local oscillator) and higher order source to the following stage or antenna.
The multiplier works best with drive
spurious outputs. FL3 selectsthe desired
Receivenoise figure is less than 4 dB.
levelsof 0 to l0 dBm. without a biasresisLO harmonic. The LO signal is filtered The unconditionally stable 50-ohm load
tor. For higherdrivelevels,the biascircuit
again in FL4 before the LO is split and presentedby the input MMIC is useful for
describedin footnote2 will providemore
applied to the transmit and receivemixers. direct connection to an antenna, and ideal output.With l0 dBm driveat230.4MHz,
The receivedsignal passesthrough FL5,
a s t h e s t a g e f o l l o w i n g a n e x t e r n a l output from FL3 is about -20 dBm, so
which attenuatesout-of-band signals.After
about 33 dB of additionalgain is needed.
amplification, image noise added to the
The filters allow coverage of the entire
With l0 dBm drive at 576-MHz,output
received signal is attenuated by FL6.
1240-to 1300-MHz band with a 144-MHz
from FL3 is - 3 dBm, soonly 16dB of gain
One noteworthy feature of this trans- IF and appropriate LO drive. The band- is required.
verter is that the choice of LO drive fre- passfilters used,although not mechanically
Padsare includedon the board for up
quency is left to the builder. The filters are c r i t i c a l , r e m o v e s i g n i f i c a n t s p u r i o u s to threeMMICs. Choosethe appropriate
narrow enough to permit use of outputs at responses.The passbandresponseof one numberof MMICs basedon availableLO
1152,576,384,288 and230.4MHz. Fig 37 RF and one LO filter section is shown in
drive level and frequency.FL3 and FL4
shows component values for 576-MHz F i g 3 8 .
mustbe isolated.If only oneMMIC is used
This transverter uses bandpass filtering
with printed hairpin filters. It will work
with any MMICs capable of operating at
1.3 GHz at the appropriateinput and output levels.New MMIC types may be easily substituted simply by changing the
MMIC and its bias resistor. It was designed
b y R i c k C a m p b e l l ,K K 7 B . r
drive from the LO board describedin footnote l. Other LO frequenciesmay require
minor component changes.
All components are surface mounted on
ol the 23rdConfer- the etched side of the board.
enceof the CentralStatesVHFSociety(Newing- tediousstep is drilling the holesnext to the
ton: ARRL,1989),pp 44-52.
MMIC mounting pads and soldering the
MS A - 0 6 8 5
zR. Campbell, "A Clean Microwave Local Oscillator," Proceedings of the 21st Conference of
the Central States VHF Society (Newington:
A R R L , 1 9 8 7 ) ,p p 5 1 - 5 7 .
M S A - 0 18 5
M u l t i p l i e*r
115 2 - M H z
115 2 - M H z
F i l te r
M S A - 110 4
12 9 6 M H z
( + 1 Jd B m )
* see text
Fig. 35 -
12 9 6 - M H z
transverter.Extensiveuse of printed-circuit
Blockdiagramof the single-board
UHFand MicrowaveEquipment 32-15
XMIT RF OUT
1 2 9 6M H z
" o , . 1I -
J- 0c. 0 1
R C V EI F O U T
(4 db NF)
- Schematicot the 1296-MHztransverter.
capacitorsare chip typesexceptas noted.DiodesD1 throughD4 are Hp
5082-2835.FL1 throughFL6,the mixertunedcircuitsand the Wilkinsdnpowerdivideiaid etchedbn the circuitboard.
Fig 37 - Part-placement
diagramfor the transverter.
The "C" wires undereach MMICconnectthe componentpad to the groundplaneon the
other side of the board.