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Mini-Circuits ADT1-1WT
The next 1:1 transformer tested is the ADT1-1WT. Expectations with this transformer were high as its specsheet shows the best phase and amplitude balance among the other 1:1 Mini-circuits transformers. Also it is very wideband. Another thing worth noticing is its strange pin-out. Unlike all other transformers, the secondairy center connection is found inbetween the primary connections at the opposite side! Fortunetely this part does not have a primairy center connection, so by simply interconnecting the 2 center pins it can be deployed in the 'normal' h-mode mixer layout. The following table lists the results:
| FSA3157 + ADT1-1WT + 74AC04 |
Vdd = 7.0V, Vbias = 1.8V |
Best bias |
| Band |
BPF |
mixer |
MDS -dBm |
IF rej |
spur |
mixer IIP3 (dBm) @ 20KHz spacing |
Bias |
IIP3 |
| IL |
CL |
- |
+ |
|
avg |
-6 |
-3 |
0 |
+3 |
+5 |
|
0 |
| -dB |
-dB |
BPF |
BPF |
-dB |
dB |
dBm |
dBm |
dBm |
dBm |
dBm |
V |
dBm |
| 160 |
3,3 |
5,56 |
133,0 |
129,0 |
56,0 |
|
|
|
39,9 |
|
|
1,8 |
39,9 |
| 80 |
1,4 |
5,76 |
132,5 |
131,0 |
57,2 |
|
43,5 |
45,0 |
45,7 |
47,0 |
48,7 |
1,8 |
45,7 |
| 40 |
2,3 |
6,12 |
132,5 |
130,0 |
59,2 |
|
|
|
46,7 |
|
|
1,8 |
46,7 |
| 30 |
3,4 |
6,24 |
132,0 |
128,5 |
59,2 |
|
|
|
45,3 |
|
|
1,8 |
45,3 |
| 20 |
3,4 |
6,40 |
132,0 |
128,5 |
61,6 |
|
|
|
44,7 |
|
|
1,8 |
44,7 |
| 17 |
3,0 |
6,44 |
132,0 |
128,5 |
65,2 |
|
|
|
44,1 |
|
|
1,8 |
44,1 |
| 15 |
3,9 |
6,52 |
132,0 |
127,5 |
66,0 |
-10,8 |
|
|
42,9 |
|
|
1,8 |
42,9 |
| 12 |
3,7 |
6,52 |
132,0 |
127,5 |
46,8 |
|
|
|
41,1 |
|
|
1,8 |
41,1 |
| 10 |
2,3 |
6,60 |
132,0 |
129,0 |
41,2 |
|
|
|
42,8 |
|
|
1,8 |
42,8 |
| 6 |
|
6,36 |
131,5 |
|
54,0 |
|
|
|
40,0 |
|
|
1,8 |
40,0 |
| 4 |
|
6,56 |
130,0 |
|
27,6 |
|
|
|
36,4 |
|
|
1,8 |
36,4 |
Conversion loss is on average more than 1dB worse than with other 1:1 transformers and worsening on higher frequencies, much like with the T1-1T.
IP3 is excellent. Almost > +40dBm on all bands, except for 160M which stays just below +40dBm.
Average spur level with the ADT1-1WT is really excellent at -10,8dB (!). Note that this applies to a mixer adjusted for best RF-IF isolation, so nothing special was done to minimize the spur level. Also note the excellent MDS levels on 6M and 4M indicating that the spur level is also very low on the VHF bands!
RF-IF isolation is really excellent, better than -60dB, if band specific adjustments are made. The levels in the table are for the best isolation on 15M.
The ADT1-1WT combination has the best bias point at 1.8V like ADTT1-1. However unlike its cousin ADTT1-1 it is not sensitive to the bias point at all.
Except for its too high high conversion loss, the ADT1-1WT configuration is a good performer: IP3 well above +40dBm on all HF bands except for 160M. Excellent RF-IF isolation combined with truly excellent spur reduction up to 4M. And last but not least a very docile character with respect to the bias point.
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