450 MHz 20 dBm multiplier pcb  - second batch.....
 
Introduction

This board uses a 10 MHz TCXO and multiplies the output by x45 in three stages
(x3 x3 x5), finishing with a medium power mmic that takes the output power up to
+20 dBm.

A small part of the pcb remains unpopulated on this build. This is either because
the circuitry is relevent for tx use only (the board can be used as a Tx driver), or it
is an option that has to to be added seperately (the auto TCXO switch-off logic,
where an external 10 MHz reference is sometimes required), the general idea
being to keep the standard option as simple as possible.

Details of the auto TCXO switch-off logic are given at the end of this page.

The board is layed-out for either a leaded or smd TCXO module, and where
components are supplied, it will be the smd version that is delivered. This runs
from a 3,3v supply, and accordingly, the supply regulator for this (IC2) is a SOT89
packaged 78L03. When using you're own  TCXO, fit a TS78L05ACY if a 5v rail is
required
pcb smd tcxo
Build information


layout       sma side

450 MHz
            circuit


C1     0.1uF 0805
C30   0.1uF 0805
R5    2k2 0805
IC3   78M08 DPAK
C2     22uF tant
C31   0.1uF 0805
R6    220R 0805
IC4   BGA6489 DPAK
C3     22uF tant
C32   0.1uF 0805
R7    100R 1206

C4     22uF tant
C33   1nF 0805
R8    1k 0805
Q1    BFS17
C5     22uF tant
C34   1nF 0805
R9    12k 0805
Q2    BFS17
C6     0.1uF 1206
C35   1nF 0805
R10   2k2 0805
Q3    BFS17
C7     10nF 0805
C36   1nF 0805
R11   47R 0805
Q4    nf
C8     0.1uF 1206
C37   1nF 0805
R12   100R 1206
Q5    nf
C9     0.1uF 0805
C38   22uF tant
R13   12k 0805
Q6    nf
C10   82pF 0805
C39   22uF tant
R14   2k2 0805

C11   0.1uF 0805
C40   1nF 0805
R15   100R 0805
D1    LLSD103A-07
C12   82pF 0805
C41   0.1uF 0805
R16   100R 1206

C13   2.2pF 0805
C42   1nF 0805
R17   22R 0805
TCXO1    10 MHz  IQD TVXO009984
C14   2.2pF 0805
C43   1nF 0805
R18   22R 0805

C15   82pF 0805
C44   nf  (no pads)
R19   nf
L1    Toko 378008 - green
C16   100pF 0805
C45   nf
R20   10k leaded pot
L2    Toko 378008 - green
C17   470pF 0805
C46   nf
R21   nf
L3    Toko 378008 - green
C18   0.1uF 0805
C47   nf
R22   nf
L4    Toko 371044 - red
C19   0.1uF 0805
C48   nf
R23   nf
L5    Toko 371044 - red
C20   0.1uF 0805
C49   nf
R24   nf
L6    Toko 371044 - red
C21   0.1uF 0805
C50   nf
R25   nf
L7    10uH 1206
C22   10nF 0805
C51   nf
R26   nf
L8    10uH 1206
C23   15pF 0805
C52   nf
R27   nf
L9    10uH 1206
C24   1pF 0805

R28   nf
L10   10uH 1206
C25   15pF 0805

R29   nf
L11   Toko 1550 93474 - yellow
C26   1pF 0805
R1    0R 0805

L12   Toko 1550 93474 - yellow
C27   22pF 0805
R2    100R 1206

L13   10uH 1206
C28   82pF 0805
R3    1k 0805
IC1   78M08   DPAK

C29   10nF 0805
R4    12k 0805
IC2   78L03 SOT89

 

A stocklist version of this might also be useful:

1pF     0805    3    C24, 26,
22uF    tant    6    C2-5, 38, 39 78L03     SOT89     1     IC2
2p2     0805    2    C13, 14
0R     0805    1    R1 78M08    DPAK      2     IC1, 3
15pF   0805   2    C23, 25
22R   0805    2    R17, 18 BGA6489 DPAK     1    IC4
22pF   0805   1    C27
47R   0805    1    R15 BFS17   SOT23      3    Q1-3
82pF   0805   4    C10, 12, 15, 28
100R 0805    1    R11 LLSD103A-07         1     D1
100pF 0805   1    C16
100R 1206    4    R2, 7, 12, 16         
IQD TVXO009984  1    TCXO1
470pF 0805   1    C17
220R 0805    1    R6
1nF     0805   8    C33-37, 40, 42, 43
1k     0805     2    R3, 8 10uH 1206                5    L7-10, 13
10nF   0805   3    C7, 22, 29
2k2   0805     3    R5, 10, 14 Toko 378008            3    L1-3        (green)
100nF 1206   2    C6, 8 
10k     pot      1    R20 Toko 371044            3    L4-6        (red)
100nF 0805   11  C1, 9, 11, 18-21, 30-32, 41
12k   0805     3    R4, 9, 13 
Toko 1550 93474     2    L11, 12    (yellow)

Items printed in blue are leaded - all else are smd

For anyone who would prefer to use rf connectors on the main pcb, this is possible - the board has been drilled for 5mm square items (ie, sma, smb, mmx), but these are not supplied as standard in the kits, the coax interconnects being soldered direct to the pcb (as can be seen in the pic at the beginning of the page).


Build procedure

It helps to have familiarized yourself with both the circuit and the layout before you begin. Start with the bottom (track) side - this all surface mount.  It is easiest perhaps to start with the smaller items first. Certainly fit IC2 before the tantalum capacitors C4 and C5, since they tend to restrict access to the IC pads, but other than this, the order of placement is not important. For those who have ordered the components as well as the pcbs, simply work your way down the the card on which the components are supplied.  Be careful to fit the tantalum 22uF capacitors the right way round (the +ve end is marked with a bar). The supply diode D1 is similarly polarised. In both cases, check your build against the layout drawing above.
Use a hot pencil tip iron, and thin solder (less than 1mm dia).

Solder blob links LK1, LK2 and LK3 - a pic of this is shown below.

Be careful not to mix up components. Although the resistors are marked with their values, the capacitors are not. A list of the semiconductor markings can be found here.

When all the bottom side components have been fitted, connect a 12v supply to the '+10-18v input' pad (Note: NOT the '+8v O/P' pad!).  The supply current should be 100mA +- 20mA. Check that the output from the two 8v regulators are correct, and likewise that the output from IC2 is 3.3v.

Now fit the top-side coils. Be very careful to fit the green and red marked coils to the correct holes! (see board picture above) - removing incorrectly fitted coils without damage to either coil or pcb is no trivial matter. The two dual helicals (L11 and 12) can be fitted either way round - they are both electrically and physically symetrical. 

Solder in the 10k pot.

Finally, fit the surface mount TCXO, this time being very careful to note the correct orientation, as bellow. If in any doubt, after fitting check that the resistance from the TCXO lid to the top copper layer is less than 1 ohm (or, if out of circuit, measure the resistance between the lid and the bottom right pin, and if less than 1 ohm, fit in the same orientation as the pic).


                      tcxo orientation                

                                        orientation of TCXO

                         solder blob
                  links                 

                                        solder blob links


Alignment

The board should be aligned prior fitting into the converter housing. Adjustment to the six ferrite cored coils (L1 L6) should be made with a copper small bladed screwdriver. I have no spare cores, and they are fragile so please please adjust carefully.

The helical coils (L11 L12) are best adjusted using a small steel bladed jewelers screwdriver.

Use a spectrum analyser fitted with a coax lead that has the free end inner uncovered by about half inch to act as a probe. With this placed close to L1, some signal at 30 MHz (3rd harmonic) should be visible. Adjust L1 for max signal. Move on to L2 and do the same. Likewise, move the probe to L3 and adjust for max 30 MHz signal.

Move the probe across to L4. Signal at 90 MHz (9th harmonic) should be visible. Adjust L4 for max. With the probe close to L5 adjust for max, and do the same at L6.

Temporarily solder a coax lead to the 450 MHz O/P socket pads on the board and feed into the spectrum analyser via a 10 dB attenuator. Alternatively, push an sma or smb socket into the board holes and interconnect with a suitable lead to the analyser. There should be signal present at 450 MHz. Adjust L11 and L12 for max reading, and then peak all coils L1 L6 once more. A final tweak of L11 and L12 should result in an output power of about 20 dBm.

This completes board alignment, and it can now be fitted into the housing.



External 10 MHz reference option


The extra components for this option are detailed here.