File name: A-150F.doc PCB: :tft029 version 1.1 17.11.2000

VI TELEFILTER Application Note TFS 150F - 11 / 15

1. General

The filter is driven in an unbalanced way. It is matched to 50 W

The matching element values given below are theoretical calculations based on measured values for termination impedance of test fixture (Q-value of matching elements is equal 30 ), given in the specification and S-parameters of the filters on PCB. If there are parasitics on the customer PCB, the matching elements have to be optimised as far as the circuit and PCB design are concerned.

We have tested on the PCB (tft029) three versions of matching network ( scheme 1, 2 and 3 ).

2. Theoretical matching

The unbalanced driven source and load termination impedances based on measured values of test fixture

(Q-value of matching elements is equal 30 ), given in the specification of the filter for Scheme 1 are :

Frequency / Source termination impedance [Zin] / Load termination impedance [Zout]
150 MHz / 272,87 W ÷ê - 10,73 pF º 31,67 W + j 87,40 W / 1345 W ÷ê - 4,17 pF º 46,5 W + j 245,64 W

2.1 Scheme 1.

The values of the matching elements that are given below are calculated from the source and load impedance on test fixture for different Q-value of the matching elements. If the values of the matching elements are not equal to standard values, the best standard values are given in brackets.

The calculation was made under consideration of the parasitic capacities of C1p and C2p of our PCB (tft029).

Input elements (theor.) / Output elements (theor.) /
ILo
Q-value / C1 [pF] / L1 [nH] / C1p [pF] / C2p [pF] / L2 [nH] / C2 [pF] / [dB]
¥ / 16 / 118 / 0 / 0 / 275 / 6,1 / -27,0
¥ / 18 / 116 / 0,5 / 0,5 / 258 / 12,5 / -27,5
¥ / 20 / 113 / 1,0 / 1,0 / 239 / 17 / -27,9
¥ / 21,2 / 110 / 1,5 / 1,5 / 221 / 21 [22] / -28,2
100 / 22 / 112 / 1,5 / 1,5 / 221 / 21 [22] / -29,1
50 / 22 / 112 / 1,5 / 1,5 / 221 / 21 [22] / -29,9
30 / 22 / 112 / 1,5 / 1,5 / 221 / 21 [22] / -30,7

The values of the matching elements that are given below are calculated under consideration of the different Q-values of the matching elements and based on measured S-parameters of the filter TFS 150F.

The calculation was made under consideration of the parasitic capacities of C1p and C2p of our PCB (tft029).

Based on measured S-parameters we calculated the following theoretical matching components

Input elements (theor.) / Output elements (theor.) / ILo
Q-value / C1 [pF] / L1 [nH] / C1p [pF] / C2p [pF] / L2 [nH] / C2 [pF] / [dB]
¥ / 22 / 112 ± 1 ( ± 1%) / 1,5 / 1,5 / 221 ± 2 ( ± 1%) / 21 [22] / -28
100 / 22 / 112 ± 3 ( ± 2,6%) / 1,5 / 1,5 / 220 ± 3 ( ± 1,4%) / 21 [22] / -29,1
50 / 22 / 112 ± 4 ( ± 3,6%) / 1,5 / 1,5 / 220 ± 3 ( ± 1,4%) / 21 [22] / -30
30 / 22 / 111 ± 5 ( ± 4,5%) / 1,5 / 1,5 / 220 ± 3 ( ± 1,4%) / 21 [22] / -30,8

2.2 Scheme 2.

The unbalanced driven source and load termination impedances (Q-value of matching elements is equal 30 ) for Scheme 2 are :

Frequency / Source termination impedance [Zin] / Load termination impedance [Zout]
150 MHz / 272,87 W ÷ê - 10,73 pF º 31,67 W + j 87,40 W / 1345 W ÷ê - 4,17 pF º 46,5 W + j 245,64 W

The values of the matching elements that are given below are calculated from the source and load impedance on test fixture for different Q-value of the matching elements. If the values of the matching elements are not equal to standard values, the best standard values are given in brackets.

The calculation was made under consideration of the parasitic capacities of C1p and C2p of our PCB (tft029).

Input elements (theor.) / Output elements (theor.) /
ILo
Q-value / L1 [nH] / L3 [nH] / C1p [pF] / C2p [pF] / L4 [nH] / L2 [nH] / [dB]
¥ / 112 / 440 / 0 / 0 / - / - / -
¥ / 112 / 370 / 0,5 / 0,5 / - / - / -
¥ / 112 / 320 / 1,0 / 1,0 / 980 / 270 / -27,8
¥ / 112 / 280 [270] / 1,5 / 1,5 / 680 / 270 / -28,2
100 / 112 / 280 [270] / 1,5 / 1,5 / 680 / 270 / -28,8
50 / 112 / 280 [270] / 1,5 / 1,5 / 680 / 270 / -29,5
30 / 112 / 280 [270] / 1,5 / 1,5 / 680 / 270 / -30,2

The values of the matching elements that are given below are calculated under consideration of the different Q-values of the matching elements and based on measured S-parameters of the filter TFS 150F.

The calculation was made under consideration of the parasitic capacities of C1p and C2p of our PCB (tft029).

Based on measured S-parameters we calculated the following theoretical matching components

Input elements (theor.) / Output elements (theor.) / ILo
Q-value / L1 [nH] / L3 [nH] / C1p [pF] / C2p [pF] / L4 [nH] / L2 [nH] / [dB]
¥ / 112 ± 5 ( ± 4,5%) / 280 [270] / 1,5 / 1,5 / 680 / 270 ± 4 ( ± 1,5%) / -28,2
100 / 112 ± 5 ( ± 4,5%) / 280 [270] / 1,5 / 1,5 / 680 / 270 ± 4 ( ± 1,5%) / -28,8
50 / 112 ± 6 ( ± 5,3%) / 280 [270] / 1,5 / 1,5 / 680 / 270 ± 5 ( ± 1,9%) / -29,5
30 / 112 ± 6 ( ± 5,3%) / 280 [270] / 1,5 / 1,5 / 680 / 270 ± 6 ( ± 2,2%) / -30,2

2.3 Scheme 3.

The unbalanced driven source and load termination impedances (Q-value of matching elements is equal 30 ) for Scheme 3 are :

Frequency / Source termination impedance [Zin] / Load termination impedance [Zout]
150 MHz / 272,87 W ÷ê - 10,73 pF º 31,67 W + j 87,40 W / 1345 W ÷ê - 4,17 pF º 46,5 W + j 245,64 W

The values of the matching elements that are given below are calculated from the source and load impedance on test fixture for different Q-value of the matching elements. If the values of the matching elements are not equal to standard values, the best standard values are given in brackets.

The calculation was made under consideration of the parasitic capacities of C1p and C2p of our PCB (tft029).

Input elements (theor.) / Output elements (theor.) /
ILo
Q-value / L3 [nH] / L1 [nH] / C1p [pF] / C2p [pF] / L2 [nH] / L4 [nH] / [dB]
¥ / 70 / 67 / 0 / 0 / 246 / 181 / -26,8
¥ / 63 / 63 / 0,5 / 0,5 / 212 / 92 / -27,0
¥ / 58 / 60 / 1,0 / 1,0 / 187 / 67 / -27,2
¥ / 53 / 57 / 1,5 / 1,5 / 168 / 54 / -27,8
100 / 53 / 57 / 1,5 / 1,5 / 168 / 54 / -28,4
50 / 53 / 57 / 1,5 / 1,5 / 168 / 54 / -29,5
30 / 53 / 57 / 1,5 / 1,5 / 168 / 54 / -30,2

The values of the matching elements that are given below are calculated under consideration of the different Q-values of the matching elements and based on measured S-parameters of the filter TFS 150F.

The calculation was made under consideration of the parasitic capacities of C1p and C2p of our PCB (tft029).

Based on measured S-parameters we calculated the following theoretical matching components

Input elements (theor.) / Output elements (theor.) / ILo
Q-value / L3 [nH] / L1 [nH] / C1p [pF] / C2p [pF] / L2 [nH] / L4 [nH] / [dB]
¥ / 53 / 51 ± 3 ( ± 5,9%) / 1,5 / 1,5 / 169 ± 3 ( ± 1,8%) / 54 / -27,8
100 / 53 / 52 ± 4 ( ± 7,5%) / 1,5 / 1,5 / 169 ± 3 ( ± 1,8%) / 54 / -28,4
50 / 53 / 54 ± 5 ( ± 9%) / 1,5 / 1,5 / 168 ± 4 ( ± 2,4%) / 54 / -29,5
30 / 53 / 56 ± 6 ( ± 10%) / 1,5 / 1,5 / 168 ± 4 ( ± 2,4%) / 54 / -30,2

3. Matching on the PCB

The matching network on the test board (PCB: tft029) was tested with SMD-components

having a Q-value of » 30.

3.1 Scheme 1.

C1 = 22 pF. L1 = ( 100 + 15 ) nH.

C2 = 22 pF L2 = ( 180 + 47 ) nH..

Elements L1 and L2 will be influenced by your board design.

Filter responses see in Appendix 1.

3.2 Scheme 2.

L1 = 100 + 18 nH, L3 = 220 nH.

L2 = 220 + 15 nH, L4 = 680 nH.

Elements L1 and L2 will be influenced by your board design.

Filter responses see in Appendix 2.

3.3 Scheme 3.

L1 = 47 nH, L3 = 47 nH.

L2 = 150 nH, L4 = 47 nH.

Elements L1 and L2 will be influenced by your board design.


Commentary.

All matching networks on the PCB does slightly differs from the theoretical matching. The reasons for that are parasitics of the PCB ( parallel capacities C1p , C2p and serial inductors of microstrip on the our board tft029 ), and particularly differences in the Q-value of the matching components.

But if the parasitics on the customer board (mentioned parasitics, additional parasitics of active parts) are different to this PCB (tft029), the matching elements will have to be slightly adjusted. Both in line and shunt elements will change both pass band shape (tilt, concave, convex) and insertion loss ILo.

Details for scheme 1:

The insertion loss depends on the values of C1 and C2, parasitic capacities of C1p and C2p, and Q-value of the SMD-components if L1 and L2 are optimal values.

From experiment on our PCB ( tft029 ) with parasitics and Q = 30 of SMD-components we have

ILo < -30 dB and concave < 0 if C1 < 22 pF and C2 < 22 pF and Q-value < 30.

The pass band tilt depends on the value of L1 and L2 :

if L1 ( < ) 112 nH (exp. = 115 nH), then pass band tilt < ( ) 0.

if L2 ( < ) 221 nH (exp. = 189 nH), then pass band tilt < ( ) 0.

Pass band shape characteristic [ tilt, ILo, S11 , S22 ] depends much on the elements of L1 and especially L2.

Details for scheme 2:

The insertion loss and concave in pass band depend on the values of L3 and L4, parasitic capacities of C1p and C2p, and Q-value of the SMD-components if L1 and L2 are optimal values :

ILo < -29 dB if L3 280 nH and L4 680 nH ( theoretical case: C1p = C2p = 1,50 pF, Q = ¥ ).

From experiment on our PCB ( tft029 ) with parasitics and Q = 30 of SMD-components we have

ILo < -30 dB and concave < 0 if L3 220 nH, L4 680 nH and Q-value < 30.

The pass band tilt depends on the value of L1 and L2 :

if L1 ( < ) 112 nH (exp. = 118 nH), then pass band tilt < ( ) 0.

if L2 ( < ) 270 nH (exp. = 235 nH), then pass band tilt < ( ) 0.

Pass band shape characteristic [ tilt, ILo, S11 , S22 ] depends much on the elements of L1 and especially L2.

Details for scheme 3:

The insertion loss and concave in pass band depend on the values of L3 and L4, parasitic capacities of C1p and C2p, and Q-value of the SMD-components if L1 and L2 are optimal values :

ILo < -28 dB if L3 53 nH and L4 54 nH ( theoretical case: C1p = C2p = 1,50 pF, Q = ¥ ).

From experiment on our PCB ( tft029 ) with parasitics and Q = 30 of SMD-components we have

ILo < -30 dB and concave < 0 if L3 47 nH, L4 47 nH and Q-value < 30.

The pass band tilt depends on the value of L1 and L2 :

if L1 ( < ) 57 nH (exp. = 47 nH), then pass band tilt < ( ) 0.

if L2 ( < ) 168 nH (exp. = 150 nH), then pass band tilt < ( ) 0.

Pass band shape characteristic [ tilt, ILo, S11 , S22 ] depends much on the elements of L1 and especially L2.

Comparison of matching schemes:

Electrical characteristics of the filter TFS 150F are equal for all matching networks if we use variable matching elements L1 and L2 ( especially L2 ).

Scheme 2 is more stable for filter characteristic in the pass band, than scheme 1, because relative accuracy (or tolerance ) of matching elements for the scheme 2 can be larger ( » 5...10 % for element L1 ), than for scheme 2 ( » 4,5 % ).

The attenuation in stopband will be much better if metal shielding (electrically connected to ground ) separates space between input and output matching elements, as the crosstalk will be reduced.

Appendix 1 : Scheme 1.