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LumpedT is a DOS application which designs lumped element band pass filters.
All filters are capacitively coupled Tchebychev types.
The filter can use any number of resonators from 2 to 18.
The program generates two output files.
The first is a list of component values.
The second is a SPICE netlist.
More information on SPICE is available on the CIRCUIT ANALYSIS page.
As an exapmle, the following four pole filter was designed using LUMPEDT, and analyzed using BSPICE,
which is free from UC Berkeley.
The resistors which appear in the SPICE circuit file are not part of the actual filter circuit.
Rin represents the source impedance of the driving circuit.
Rout represents the impedance of the load.
RR is a very large value dummy resistor. It has negligible effect on the simulation results,
but it is needed to make the SPICE simulator work.
R1 to Rn are added to model the loss of the coils. Their values are determined from the coil Q.
The example below shows the program prompts, and the user responses when the program was run
to design a four pole bandpass filter with a passband of 14 to 16 MHz. The two files which resulted
from this session are included as examples in the downloadable ZIP file.
Note that scientific notation is used instead of units like MHz and PF, so
a 100pf capacitor's value is denoted "100e-12", and a frequency of 14 MHz is denoted "14e6".
All units of frequency are in Hertz, Capacitance in Farads, inductance in Henrys, and resistance in Ohms.
Text generated by the program is shown in black.
The user responses are shown in red.
Comments are shown in green.
First, at the DOS prompt, type LUMPEDT
enter name of file to save filter data.
FILENAME:: [response: 15mhz.fil ]
enter name of file for SPICE analysis.
CADFILE:: [response: 15mhz.cir ]
enter lower bandedge in Hz:: [response: 14e6 ] i.e. 14MHz
enter upper bandedge in Hz:: [response: 16e6 ] i.e. 16MHz
enter input impedance, Ohms :: [response: 50 ]
enter output impedance, Ohms :: [response: 50 ]
enter passband ripple(db).
RIPPLE(Db):: [response: 0.5 ]
enter number of sections
N:: [response: 4 ]
enter approximate resonator capacitor value, FARADS:: [response: 100e-12 ] i.e. 100pF
Section C(series) C(parallel) L(parallel)
0 5.543386e-11 0 0
1 1.368364e-11 9.99976e-11 6.686669e-07
2 9.825153e-12 9.999906e-11 9.155829e-07
3 1.368364e-11 9.999906e-11 9.155829e-07
4 5.543387e-11 9.99976e-11 6.686669e-07
the values above are the L and C values chosen for the filter
Change resonator capacitences {C(parallel)}? (Y/N):: [response: N ]
Note; Optionally, we might have changed the first and last resonator
capacitors to a smaller value so that the program would choose a larger
value for the associated inductors. By adjusting these values, we
could get all of the inductors near the same value, allowing us to
use standard 1.0 microhenry adjustable inductors in all four places.
data saved in file {15mhz.fil}
enter coil Q for SPICE analysis :: [response: 220]
(for such a high Q, large coils are needed)
enter analysis frequencies in Hz:
Start:: [response: 10e6 ] i.e. 10MHz
Stop:: [response: 20e6 ]
Number of Points:: [response: 101 ]
(run analysis at 101 frequency points)
Circuit File saved in file {15mhz.cir}
That's it, the program has ended, and the filter files are left in the current directory.
The file 15MHZ.FIL is the filter data file generated for this filter circuit.
If you have downloaded BSPICE from this site, you can now type BSPICE 15MHZ.CIR to run an analysis
Make a note of the output node. In this case, the output node will be node 7.
Next, to display the results from SPICE, type NUTMEG.
From the NUTMEG prompt, type plot vdb(7). Be sure not to use capital letters.
NUTMEG will plot the response in dB at the output node (node 7).
The file 15MHZ.CIR is the spice netlist generated for this filter circuit.
Tcheychev bandpass filter
vin 1 0 ac 2
Rin 1 2 50
RR 2 0 5000000
CC0 2 3 5.543386e-11
C1 3 0 9.99976e-11
L1 3 0 6.686669e-07
R1 3 0 2829.607691
CC1 3 4 1.368364e-11
C2 4 0 9.999906e-11
L2 4 0 9.155829e-07
R2 4 0 3874.485858
CC2 4 5 9.825153e-12
C3 5 0 9.999906e-11
L3 5 0 9.155829e-07
R3 5 0 3874.485838
CC3 5 6 1.368364e-11
C4 6 0 9.99976e-11
L4 6 0 6.686669e-07
R4 6 0 2829.60763
CC4 6 7 5.543387e-11
Rout 7 0 50
.ac LIN 101 10000000 2e+07
.plot ac vdb(7)
.end
The file 15MHZ.FIL is the filter data file generated for this filter circuit.
output from program C:\FILTER\LUMPEDT.EXE data saved in file {15mhz.fil}
lowpass prototype (g) values:
1
1.670357
1.19255
2.36617
0.84186
1.984127
passband ripple =0.5 db
Midband loss= 4.38457dB
L[1]= 6.686669e-07
L[2]= 9.155829e-07
L[3]= 9.155829e-07
L[4]= 6.686669e-07
CC[0]= 5.543386e-11
CC[1]= 1.368364e-11
CC[2]= 9.825153e-12
CC[3]= 1.368364e-11
CC[4]= 5.543387e-11
C[0]= 0
C[1]= 9.99976e-11
C[2]= 9.999906e-11
C[3]= 9.999906e-11
C[4]= 9.99976e-11