SMALL EFFECTIVE MICROWAVE CAD PACKAGES

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H e w l e tt-Pac kard Hain Henu * RppCAD Transis tor Design Data Hixer Spurious Search Uersion 1 .02 Microwave Calculator Microwave Path Calculat ions Transmission Lines Hewlett-Packard Co., 1990 Two-port Circuit Analys is A l l r i g h t s reserued S p i r a l Inductor Design Impedance Hatching PIN Attenuator and Switch Design Schottky Detector Calculat ions Transis tor Bias C i r c u i t s NoiseCalc Thermal Analys is Product S e l e c t i o n Guide HP Part No. HAPP-0001 Li terature Request Sample Request Application Engineering S t a f f Register f o r Updates For More Information.. .

= CPII=Help CESCl=Return t o DOS ,- Use t h e arrow keys t o h i g h l i g h t d e s i r e d i t e m and press return t o select

Micro wau e Se m ic o nduc t o r Diu is ion

Dr. Ed da Silva

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Abstract: Three low cost microwave effective CAD software programs are described in this paper. They are Hewlett Packard’s AppCAD, CalTech’s PUFF, and Motorola’s MIMP. AppCAD is useful for the calculation of individual components, losses and gains. PUFF is valuable in calculating two port parameters input and output matches, gains and losses, frequency responses and plotting facilities for layout artwork. MIMP provides real time facilities for narrow and broadband matching using Smith charts and rectangular plots.

1 Introduction Excellent radio engineering computer programs, such as Touchstone, Compact, and Academy have been available for many years. These programs are excellent and extremely versatile. However, these facilities cost money, require quality computers with large RAM, and disk facilities. Many people and some small radio engineering courses cannot afford these costs. learning situations, software expenditure becomes doubly important because each student must be provided with programs which can be run on their home computers. Therefore low cost, small, powerful packages requiring minimum storage and RAM requirements are vitally important. Open University, we use inexpensive but powerful programs such as Hewlett Packard’s AppCAD, CalTech’s PUFF and Motorola’s Impedance Matching Program (MIMP) to provide students with hands on experience.This paper shows how these programs are used by the Open University for its long distance learning courses in Radio Engineering.

In long distance

At the

2. 0 Hewlett-Packard’s Computer Aided Design Program - AppCAD. Hewlett - Packard’s Applications Computer Aided Design Program AppCAD is a collection of software tools or modules, which aid in the design of RF (radio frequency) and Microwave circuits. AppCAD also includes a selection guide for Hewlett Packard RF and Microwave semiconductors. The modules considered in AppCAD are shown in figure 2.1 Each main program is listed on the left table while the highlighted item is described on the right table.

Dr. Ed da Silva is in the Telematics Dept, Open University, Milton Keynes

0 1997 The institution of Electrical Engineers. Printed and published by the IEE, Savoy Place, London WC2R OBL, UK. 8/ 1

A main program usually sub-divides into other programs. For example, the transmission lines program sub-divides into seven other types of transmission lines. See figure 2.2

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ewle t t -Packard Transmiss ion Line C a l c u l a t o r OppCIII

T h i s module computes t h e e l e c t r i c a l parameters of v a r i o u s t r a n s m i s s i o n l i n e s t r u c t u r e s g i v e n t h e i r p h y s i c a l dimensions. Begin by s e l e c t i n g t h e t r a n s m i s s i o n l i n e t y p e from t h e menu below.

S t r i p l i n Z . S i i i g l e Line S t r i p l i n e Coupled L i n e s

Coplanar Waveguide GPW w i t h Groundplane

C o a x i a l L ine

CESC ]=Qui t Use t h e a r row keys t o h i g h l i g h t d e s i r e d i t e m and vress r e t u r n t o s e l e c t

Figure 2.2 Sub-division of the transmission line program.

Figure 2.2 further sub-divides into another screen for calculation. the calculation of co-planar waveguide with a ground plane.

Figure 2.3 shows the case for

- H e w l e t t - P a c k a r d Coplanar Waveguide With Groundplane e p p x i i .

I n p u t Width * I I + Height

Preq: im GHz 1 I I I I - E r : 9 .8 + I I+ Gap

Gap: 5.0 Er Height : 2 5 . 0 Length: iL88.8 t t

NOTE: With Groundplane

1 o u t p u t

I Eo: 49 .96 Eeff : 5.52

E l e c Length: 85 .97 dey

[PI 1 =He l p CP2 ]=Compute CP3 ]=Units CESCI=Quit E n t e r a n a l u s i s f r e a u e n c u .

Figure 2.3 Calculation of co-planar waveguide with ground plane.

The same is true of the Microwave calculator program. programs. See figure 2.4

It also sub-divides into four separate

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SWRI = SWR2 = 2.18

Max SWR 2.42

Max Phase Error f 1.42 deg

Hax Hismatch + 0.212 dB Error - 0.217 dB

Reflectometer

Coupler D i r e c t i v i t y = 35 dB

H i n Heas Hax

SWR 1.78 1.86 1.93 Refl Coefficent 0.28 0.30 0.31

Return Loss <dB> 10.96 10.43 9.94 Hismatch Loss <dB> 0.36 0.41 0.36

- CPII=Help CP2l=Compute CP31=Toggle [ESCI=Quit - -- - Use the arrow keys t o highl ight desired i t e m and press r e tu rn t o s e l e c t

Figure 2.4 AppCAD’s calculator program -

dB = 6.00 -1 r SWR = 1.81 Refl Coeff = 0.28

Uoltage Ratio = 2.00 E 00 Return Loss = 10.80 dB Power Ratio = 4.00 E 00 Mismatch Loss = 0.37 dB

3.0 PUFF Version 2.0

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P U F F was chosen because of (a) its low costs, (b) its ease of use, PC format, (c) its versatility, (d) its computer requirement flexibility - ( = 290 KB on a floppy disk), any processor from an 8080 to pentium, choice of display, CGA, EGA or VGA, and (e) choice of printer, dot-matrix, bubble jet or laser. In the radio courses at the Open University we use it for (a) lumped and distributed filter design, evaluation, layout and fabrication, (b) evaluation of s-parameter networks, (c) lumped and distributed matching techniques, layout and construction and (d) amplifier design layout and construct ion.

One example of a microwave filter design, bandpass response, match response, and layout is shown in figure 3.1.

Figure 3.1 Microwave bandpass Fi l ter

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The layout section F1 can be expanded and printed out individually to form a template for etching and construction purposes. The great advantage in printing the layout in expanded form on a printer is that it permits line imperfections in the printer to be minimised, when the lithographic process is reduced down to the actual etching size.

Figure 3.2 shows the construction of an amplifier with feedback. The s-parameters of the amplifier circuit together with its frequency response is also plotted by the program. Components, calculated parameters and frequency response can all be selected by the user to suit the individual case. Enlarged Smith chart facilities are also available and these prove invaluable when PUFF'S stub-matching facilities are used. with open or short-circuit matching stubs.

The latter is particularly useful for comparing circuit responses

F2 : PLOT - Points 5 1 Smith radius 3

S11 0 .@@dB 180 .O0 x s21 0 os12 0 +S22 -9.lOdB 0.0O

f 0.0000 GHz

PUFF can also be used for the design of oscillators; it has compressed Smith chart facilities.

F1 : LRVOUT

4 . 0 Motorola's Impedance Matching Program (MIMP)

MIMP is excellent for narrow band and wide band matching of impedances. It has facilities for matching complex source and load impedances, designing lumped or distributed circuits with the desired Q graphically. This program can be explained by an example. Consider the case where the output impedance, =(20 + j0)Q of a transmitter operating between 470 MHZ and 500 MHz is to be matched to an antenna whose nominal impedance is 50Q. A return loss of =20 dB is required. The conditions are entered into MIMPs as in figure 4.1. Three frequencies are used to cover the band and the load and source impedances are also entered into the figure.

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Copyright (c) Motorola, Inc. 1992 All rights reserved.

IMPEDANCE ENTRY SCREEN

[Please press RIGHT mouse button or ESCwhen done]

T o change a value, Select using IeWright arrows Press ‘E’ to edit

FREQ (MHzl

470.0

485.0

500.0

LOAD IMPEDANCE User Z Zin

R e Im

50.00 0.00 50.00 >99999 50.00 0.00 50.00 ,99999 50.00 0.00 50.00 ,99999

SOURCE IMPEDANCE

(ser):

(ser):

(ser):

(pad:

(par):

(par):

Zol R e Im

20.00 0.00 20.00 >99999 20.00 0.00 20.00 >99999 20.00 0.00 20.00 >99999

x: 0

MOTOROLA’S IMPEDANCE MATCHING PROGRAM

Programmer: Dan Moline

Figure 4.1 Input Data for Motorola’s MIMP

When figure 4.1 is completed, the ESC key is pressed to move on to figure 4.2 where a network is chosen. components and the Q of the matching network are unknown so nominal values are inserted. The exact values will be derived later. For clarity, Zin and the Load have been shown in figure 4.2.

For this case, a T network has been chosen. At this stage, the exact values of the

Select circuit element. (Press RIGHT mouse button to view SMITH chart.]

m 3.650PF

+ Load = 50 R

Zin = 20 R

Figure 4.2 Matching circuit for Motorola’s MIMP

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After completion of figure 4.2, the ESC key is pressed to enter figure 4.3. Starting from the top left line in figure 4.3, we have “SERIES CAP and up/down arrows which allow any component to be selected. C1 is shown in this case. Capacitors are shown in this box with its arrow keys. The next right block shows values of inductors. Adjustment is provided by up/down arrow keys. The next right box with its arrow keys is the Q selection box. Q = 3 has been selected. The next box after the logo is the line impedance (Z,) box. Its default position is lOsZ but it can be changed and the Smith chart plot values will automatically change accordingly. The FREQ box allows selection of frequency. It has been set to mid-point, i.e. 485 MHz. The remaining three boxes are self- evident.

Figure 4.3 Smith chart and input return loss.

The middle left hand box provides a readout of impedance at points to the “right” of a junction. The Smith chart return loss circle size is determined by the Return Loss boundary set in the lower left box. Arcs AB, BC, and CD are adjusted by components, C1, C2, and L1 respectively.

5 . 0 Conclus ions:

The above computer aided learning programs are extremely low cost and provide a very good cross-section of theoretical and practical constructional techniques for microwave radio devices and circuits.

Manuscript prepared 3/11/97 Milton Keynes, England MK7 6AA

by author, Dr. Ed da Silva, Telematics, Open University, Walton Hall,

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