*****************************************************************
* ARRL Radio Designer 1.0 File EXRF9501.TXT V 1.1 (23 Dec 1994) *
* Exploring RF -- January 1995 *QST*, pp 80-82                  *
* compiled by David Newkirk, WJ1Z (dnewkirk@arrl.org)           *
*                                                               *
* Parts One and Two of this file will run as analyzable ARD     *
* netlists--SEPARATELY. ARD won't like it if you just copy this *
* entire file, containing Parts One AND Two, into               *
* Circuit Editor, and will remind you of this with the error    *
* message "Duplicate label name: ONEPORT."*                     *
*                                                               *
* Part One:                                                     *
*                                                               *
* Using ARRL Radio Designer 1.0's Optimizer                     *
* to adjust a C-L-C T-Network                                   *
* for a 10+j0-Ohm to 50+j0-Ohm transformation                   *
* at 1.9 MHz                                                    *
*****************************************************************
*
* In this example, optimization adjusts a C-L-C T network
* to transform a 10-ohm resistive load to 50 ohms, resistive
* (50+j0 ohms), at 1.9 MHz. To do this, we describe the network as
* a 1-port (the ONEPORT block below), in which the netlist
* line "RES 3 0 R=10" specifies the load we want to transform. Question
* marks bracket the optimizable values--its 20- to 1000-pF input
* capacitor and its 0.1- to 35-uH inductor. (Note that we've constrained
* the optimizable values to these limits. If the optimizer can't reach
* its goal within these constraints, we learn something quite useful:
* that the load we want to transform is outside the transformation limit
* of the network's components.) Since our goal is to simulate
* manual adjustment of a T-net serving as an antenna tuner, we won't let
* optimization adjust the network's output capacitor (also a 20- to
* 1000-pF unit). Instead, we begin by setting the output capacitor
* to its maximum value (as an experimenter would likely do in adjusting
* the network), since keeping the network's output capacitance as high
* as possible minimizes the network's loss for a given transformation.
*
* Note: Figure 1 of January 1995 QST's Exploring RF shows the network
* capacitors as 20- to 240-pF parts. Upping their maximum capacitance to
* 1000 pF is one of the "few additions and changes" implied by the text's
* Figure 1 callout. With its capacitors (especially its output capacitor)
* constrained to 240 pF, the Figure 1 network can do no better in
* in transforming 10+j0 ohms to 50+j0 ohms at 1.9 MHz than the lower
* three curves in the column's Figure 3. You can experiment with such
* limitations at will just by changing the constrained values, or
* by hard-coding one or more values, as I've done with C/OUT\in the block
* that follows. Fixing C/OUT\'s value in this way lets you answer this
* question: "Can the C-L-C network in Figure transform 10+j0 to 50+j0 ohms
* at 1.9 MHz with a C/IN\ between 20 and 1000 pF, an L between 0.1 and
* 35 microhenries, and C/OUT\ set to 240 pF?"
*
BLK
 CAP 1 2 C=?20PF 82.1733PF 1000PF? Q=1000 ; this is C/IN\
 IND 2 0 L=?0.1UH 30.2528UH 35UH? Q1=200 F=2.52MHZ ; this is L
 CAP 2 3 C=240PF Q=1000 ; this is C/OUT\
 RES 3 0 R=10
 ONEPORT:1POR 1
END
* Once the optimizer has found a set of values that work, we can determine
* the network's loss and frequency response by reconfiguring the T-net
* as a 2-port. This lets ARRL Radio Designer determine the network's forward
* transmission gain (MS21, the magnitude of the S parameter S21). To do this,
* we remove the * network's 10-ohm load resistor (we'll specify a
* 10+j0-ohm load in ARRL Radio Designer's Report Editor) and replace it with
* an ideal transformer (TRF) configured to look like 10 ohms with 50 ohms a
* its output. (Because the TRF is ideal, it is lossless and does not skew the
* network's frequency response.)
*
* Removing the contrained optimizable values and their bracketing question
* marks is a good thing to do in this new block because we'll want to use the
* ONEPORT block over and over to see if the T-net can successfully transform
* various loads, and because ARRL Radio Designer's optimizer attempts
* to adjust ALL the question-mark-delimited values in a.CKT file--even
* those outside the circuit named as optimizable in the OPT block--during
* optimization.
*
BLK
 CAP 1 2 C=477.616PF Q=1000
 IND 2 0 L=4.90764UH Q=200 F=2.52MHZ
 CAP 2 3 C=1000PF Q=1000
 TRF 3 4 0 0 R1=10 R2=50
 OUT1000P:2POR 1 4
END
* The remaining three 2-port blocks show the results of optimization done
* at other output capacitance values. Each succeeds in transforming
* 10+j0 ohms to 50+j0 ohms, but plotting their response indicates
* that the network's minimum loss varies inversely with output capacitance
* --at least for this 10+j0- to 50+j0-ohm transformation. In using this
* T network for feeding transmitter power to an antenna at 1.9 MHz, we'd
* want to minimize the network's loss to avoid component overheating.
BLK
 CAP 1 2 C=122.811PF Q=1000
 IND 2 0 L=19.3847UH Q=200 F=2.52MHZ
 CAP 2 3 C=240PF Q=1000
 TRF 3 4 0 0 R1=10 R2=50
 OUT240PF:2POR 1 4
END
BLK
 CAP 1 2 C=104.752PF Q=1000
 IND 2 0 L=23.063UH Q=200 F=2.52MHZ
 CAP 2 3 C=200PF Q=1000
 TRF 3 4 0 0 R1=10 R2=50
 OUT200PF:2POR 1 4
END
BLK
 CAP 1 2 C=82.1733PF Q=1000
 IND 2 0 L=30.2528UH Q=200 F=2.52MHZ
 CAP 2 3 C=150PF Q=1000
 TRF 3 4 0 0 R1=10 R2=50
 OUT150PF:2POR 1 4
END
* The FREQ block sets relative high simulation resolution (1-kHz STEPs)
* from 1.8 to 2.0 MHz for maximum report (graph and table) resolution in
* Amateur Radio's 1.8- to 2.0-MHz (160-meter) band. Specifying 300
* exponentially stepped (ESTP) frequencies from 0.5 to 30 MHz is
* appropriate for logarithmically graphing the network's frequency
* response across this wider range.
FREQ
 STEP 1.8MHZ 2.0MHZ 1KHZ
 ESTP 0.5MHZ 30MHZ 300
END
* The OPT block specifies our target 50+j0-ohm load in terms of the
* 1-port impedance parameters RZ11 and IZ11. The TERM=1E-5 line tells
* the optimizer to consider the job done--to TERMinate optimization--
* when it has adjusted the circuit's optimizable values for an error
* function of 1E-5 rather than chasing the error function all the way
* down to 0 (the optimizer's default goal).
*
* Because the SWR-driven power-foldback circuits in modern solid-
* transmitters usually don't kick in until SWR hits 1.5 to 2.0, 1E-5 is
* much farther than we need to go in achieving a match if all we want the
* network to do is make its load look enough like 50+0j0 to make a
* transmitter happy. With this in mind, we could modify
* the optimization goal along the lines of
*
* RZ11=33 75 ; see "Two Value Goals" on page 19-17 of the ARD Manual
* IZ11=0
* 
* This spec lets the optimizer stop when it causes the resistive
* portion of the net's input impedance to fall within the RZ11 range
* that corresponds to an SWR of 1 to 1.5, while keeping the reactive
* portion of the net's input Z at 0. (Power in a reactance doesn't do
* useful work, so we want a transmitter to see a purely resistive
* load even if that means settling on a resistive load that
* diverges a bit from 50 ohms.)
OPT
 ONEPORT
 F=1.9MHZ
 RZ11=50
 IZ11=0
 TERM=1E-5
END
*
************************************************
* ARRL Radio Designer 1.0 File EXRF9501.TXT    *
* Exploring RF -- January 1995 *QST*           *
*                                              *
* Part Two:                                    *
*                                              *
* Using ARRL Radio Designer 1.0's Optimizer    *
* to adjust a C-L-C T-Network                  *
* for a 60+j60-Ohm to 50+j0-Ohm transformation *
* at 7.2 MHz                                   *
************************************************
*
* Instead of terminating the network with a resistor or an LC, RL or RC
* network, we use ARD's ONE black-box element to specify a complex
* load directly, as shown in the
*
* ONE 3 0 ANTENNA
*
* netlist line below. Rather than specify the load on this line, we
* point to the ANTENNA entry in netlist's DATA block.
* 
BLK
 CAP 1 2 C=?20PF 198.234PF 240PF? Q=1000
 IND 2 0 L=?0.1UH 1.56629UH 35UH? Q1=200 F=2.52MHZ
 CAP 2 3 C=?20PF 122.386PF 240PF? Q=1000
 ONE 3 0 ANTENNA
 ONEPORT:1POR 1
END
FREQ
 STEP 7.1MHZ 7.3MHZ 1KHZ
 ESTP 1MHZ 30MHZ 300
END
OPT
 ONEPORT
 F=7.2MHZ
 RZ11=50
 IZ11=0
 TERM=1E-5
END
DATA
 ANTENNA: Z RI ; see "Data for One" on page 17-6 of the ARD Manual
 60 +60
END

