Cascade Analysis
Description: Electrical engineering software for noise figure and distortion analysis. Used for receiver/transmitter design and analysis.
Keywords: cad, CAD, cascade, distortion, distortion analysis, friis, intercept point, lineup, lineup analysis, noise, noise analysis, noise temperature, noise figure, receiver, rfcascade, signal chain, source temperature, third order intercept point, third order intercept,

# Cascade Analysis Program

- Overview/Features
- Features
- Input File Format
  - Comments
  - DEFAULTS Line
  - SOURCE Line
  - Element Lines
- Example
  - Example Input File
  - Running Cascade
  - Example Output
- System Requirements
- Licensing
- Obtaining Cascade
- Installation
- Reporting Bugs

## Overview/Features

Cascade is a program for analyzing the noise and distortion performance of a cascade of elements in an electronic system. A typical application of cascade is the analysis of a receiver. A text description of the receiver block diagram consisting of things like amplifiers, mixers, and filters is entered into cascade. Each element is characterized by its gain and optionally noise figure, and third order intercept point. The program then analyzes the system and produces a report detailing the performance at each stage.

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## Features

- Noise Figure Analysis
- Third Order Intercept Point Analysis
- Fast Execution
- Easy to Learn and Use

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## Input File Format

Cascade reads a system description from a text file, computes the parameters for the system, and produces a report file. The input file is created using any ASCII text editor.

### Comments

Any line beginning with `*`, `#`, or `;` is treated as a comment line and is ignored. In addition, any line starting with `@` is treated as a verbose comment line which is copied over to the output. This allows extra annotation to be added to the output file. Blank lines (lines with only spaces and tabs) are ignored.

### DEFAULTS Line

An optional `defaults` line may be included to tell the program certain default parameters. The `defaults` line may be used anywhere in the input file. The listed values take effect at the place in the system where the `defaults` line is given. Multiple `defaults` lines may be used in the input file. This is useful if, for example, the system switches from 75 ohms to 50 ohms part way through the cascade.

A defaults line is specified as follows:

`

- defaults [rin=RIN] [rout=ROUT] [rho=RHO]

`

Where

- `RIN` = Default input resistance for each stage

- `ROUT` = Default output resistance for each stage

- `RHO` = Default third order intermodulation distortion correlation coefficient

Some examples of valid `defaults` lines are:

`
- defaults rin=75 rout=75
- defaults rho=1
- defaults rin=600 rout=600 rho=0
`

### SOURCE Line

An optional source line may be included to tell the program what the carrier level is going into the system. In addition, C/No, or equivalently, C/N and receiver noise bandwidth, may be specified to allow calculation of C/N degredation. If a `source` line is used, it must come before any element lines. A source is specified as follows:

`

- source c=C [cno=C/No | cn=C/N bw=BW]

`

Where

- `C` = Carrier level at the input to the system in dBm.

- `C/No` = Carrier to noise spectral density ratio at the input to the system in dBc/Hz.

- `C/N` = Carrier to noise ratio at the input to the system in dBc.

- `BW` = Receiver noise bandwidth in Hz.

Some examples of valid source lines are:

`
- source c=-25 cn=50 bw=6e6
- source c=-15 cno=115
- source c=-10
`

### Element Lines

Each element in the system is described by an element line. The elements are connected in the order in which they appear in the input file. Elements are entered as follows:

`

- element_name g=G|gp=GP|gv=GV [nf=NF] [iip3=IIP3 [r=RHO] ] [rin=RIN] [rout=ROUT]

`

Where

- `element_name` = Any string to name the block. The only restriction is that the keyword `source` may not be used as an element name. Underscores should be used in place of spaces in the element name.

- `G` = Power gain of the element in dB.
- `GP` = Power gain of the element in dB.
- `GV` = Voltage gain of the element in dB.

- `NF` = Noise figure of the element in dB. Defaults to 0 dB

- `IIP3` = Input third order intercept point of the element in dBm. Default is no distortion created.

- `RHO` = Distortion correlation coefficient for the element. A value of 0 produces power addition, a value of 1 produces voltage addition. The value of `RHO` must be between 0 and 1. If not specified by a `defaults` line, then the default value is 0 (power addition), otherwise the value from the `defaults` line is used.

- `RIN` = Input resistance in ohms. Currently only used in conjunction with `ROUT` to relate voltage gain and power gain for the stage. If not specified, it defaults to the value given by the most recent `defaults` line.

- `ROUT` = Output resistance in ohms. Currently only used in conjunction with `RIN` to relate voltage gain and power gain for the stage. If not specified, it defaults to the value given by the most recent `defaults` line.

Some examples of valid element lines are:

`

- ideal_gain g=10
- noisy_gain g=12 nf=15
- transformer gp=0 rin=50 rout=200
- nonlinear_amp g=8 nf=6 iip3=-5

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## Example

This section shows an example of the use of the cascade program. The block diagram for the system to be analyzed is shown below.

### Example Input File

The input file `ex1.cas` contains the following:

`

    # Id: ex1.cas,v 1.2 2001/09/05 19:15:37 dan Exp
    #
    @ An example input file for the program cascade
    #

    source c=-40 cn=25 bw=1e6
    rf_filter g=-1.5 nf=1.5
    lna g=10 nf=2.3 iip3=0
    first_mixer g=-7 nf=7 iip3=20
    if_amp_1 g=8 nf=5 iip3=12
    transformer rin=50 rout=200 gp=0
    # end of input file

`

### Running Cascade

To run cascade on the input file and display the results to the screen, use the following format.

`cascade ex1.cas`

or,

`cascade ex1.cas | more`

The results can be saved to a file by

`cascade ex1.cas > ex1.out`

### Example Output

The resulting output file `ex1.out` contains the following:

`

    ************************************************************
    *                    CASCADE ANALYSIS                      *
    *                     Version   1.4                        *
    *               (c) 1997-2001 Dan McMahill                 *
    *                  mcmahill@alum.mit.edu                   *
    ************************************************************

    Processing input file "ex1.cas"

    @ An example input file for the program cascade
    ************************************************************
    *    Input Source                                          *
    ************************************************************
         Source Resistance   = 50 Ohms

         Input Carrier Level = -40 dBm
         Input Noise Density = -125 dBm/Hz

         Input C/N           = 25 dB
         Receiver Noise BW   = 1 MHz

         Input C/No          = 85 dB/Hz

    ************************************************************
    *    Stage #1  "rf_filter"                                 *
    ************************************************************
         Power Gain= -1.50 dB, Voltage Gain= -1.50 dB
         NF=  1.50 dB
         Input Res. = 50 Ohms,  Output Res. = 50 Ohms
         No Distortion In this Stage

         Total Power   Gain                     =   -1.50 dB
         Total Voltage Gain                     =   -1.50 dB
         Total Noise Figure                     =    1.50 dB
         Noise Figure from this stage only      =    1.50 dB

         C/N                                    =   25.00 dB
         C/No                                   =   85.00 dB
         C/N Degradation                        =   0.000 dB
         C/N Degradation from this stage only   =   0.000 dB

         Output Carrier Level                   =  -41.50 dBm
                                                =    5.49 dBmV

         Output Open Circuit Voltage            =   11.51 dBmV

    ************************************************************
    *    Stage #2  "lna"                                       *
    ************************************************************
         Power Gain= 10.00 dB, Voltage Gain= 10.00 dB
         NF=  2.30 dB
         Input Res. = 50 Ohms,  Output Res. = 50 Ohms
         IIP3=  0.00 dBm ( 46.99 dBmV), RHO=  0.00

         Total Power   Gain                     =    8.50 dB
         Total Voltage Gain                     =    8.50 dB
         Total Noise Figure                     =    3.80 dB
         Noise Figure from this stage only      =    2.98 dB

         C/N                                    =   25.00 dB
         C/No                                   =   85.00 dB
         C/N Degradation                        =   0.000 dB
         C/N Degradation from this stage only   =   0.000 dB

         IIP3                                   =    1.50 dBm
         IIP3 from this stage only              =    1.50 dBm

         Output Carrier Level                   =  -31.50 dBm
                                                =   15.49 dBmV

         Output Open Circuit Voltage            =   21.51 dBmV

         Third Order Intermod Level             =  -83.00 dBc

    ************************************************************
    *    Stage #3  "first_mixer"                               *
    ************************************************************
         Power Gain= -7.00 dB, Voltage Gain= -7.00 dB
         NF=  7.00 dB
         Input Res. = 50 Ohms,  Output Res. = 50 Ohms
         IIP3= 20.00 dBm ( 66.99 dBmV), RHO=  0.00

         Total Power   Gain                     =    1.50 dB
         Total Voltage Gain                     =    1.50 dB
         Total Noise Figure                     =    4.72 dB
         Noise Figure from this stage only      =    1.95 dB

         C/N                                    =   25.00 dB
         C/No                                   =   85.00 dB
         C/N Degradation                        =   0.000 dB
         C/N Degradation from this stage only   =   0.000 dB

         IIP3                                   =    1.48 dBm
         IIP3 from this stage only              =   11.50 dBm

         Output Carrier Level                   =  -38.50 dBm
                                                =    8.49 dBmV

         Output Open Circuit Voltage            =   14.51 dBmV

         Third Order Intermod Level             =  -82.96 dBc

    ************************************************************
    *    Stage #4  "if_amp_1"                                  *
    ************************************************************
         Power Gain=  8.00 dB, Voltage Gain=  8.00 dB
         NF=  5.00 dB
         Input Res. = 50 Ohms,  Output Res. = 50 Ohms
         IIP3= 12.00 dBm ( 58.99 dBmV), RHO=  0.00

         Total Power   Gain                     =    9.50 dB
         Total Voltage Gain                     =    9.50 dB
         Total Noise Figure                     =    6.53 dB
         Noise Figure from this stage only      =    4.03 dB

         C/N                                    =   25.00 dB
         C/No                                   =   85.00 dB
         C/N Degradation                        =   0.000 dB
         C/N Degradation from this stage only   =   0.000 dB

         IIP3                                   =    1.44 dBm
         IIP3 from this stage only              =   10.50 dBm

         Output Carrier Level                   =  -30.50 dBm
                                                =   16.49 dBmV

         Output Open Circuit Voltage            =   22.51 dBmV

         Third Order Intermod Level             =  -82.89 dBc

    ************************************************************
    *    Stage #5  "transformer"                               *
    ************************************************************
         Power Gain=  0.00 dB, Voltage Gain=  6.02 dB
         NF=  0.00 dB
         Input Res. = 50 Ohms,  Output Res. = 200 Ohms
         No Distortion In this Stage

         Total Power   Gain                     =    9.50 dB
         Total Voltage Gain                     =   15.52 dB
         Total Noise Figure                     =    6.53 dB
         Noise Figure from this stage only      =    0.00 dB

         C/N                                    =   25.00 dB
         C/No                                   =   85.00 dB
         C/N Degradation                        =   0.000 dB
         C/N Degradation from this stage only   =   0.000 dB

         IIP3                                   =    1.44 dBm

         Output Carrier Level                   =  -30.50 dBm
                                                =   16.49 dBmV

         Output Open Circuit Voltage            =   22.51 dBmV

         Third Order Intermod Level             =  -82.89 dBc

    ************************************************************
    ****** ANALYSIS OF THE  5 ELEMENT CASCADE IS COMPLETE ******
    ************************************************************

    ************************************************************
    *       Noise Figure Contribution Summary                  *
    ************************************************************

         Stage          Noise Figure     Possible Noise Figure
                        in the system          Improvement
    ---------------   ----------------   ----------------------
    if_amp_1              4.033 dB               1.808 dB
    lna                   2.980 dB               1.075 dB
    first_mixer           1.950 dB               0.585 dB
    rf_filter             1.500 dB               0.418 dB
    transformer           0.000 dB               0.000 dB

    ************************************************************
    *             IIP3 Contribution Summary                    *
    ************************************************************

         Stage         IIP3 in the system
    ---------------   --------------------
    lna                    1.500 dBm
    if_amp_1              10.500 dBm
    first_mixer           11.500 dBm

    ************************************************************
    *              CASCADE ANALYSIS COMPLETE                   *
    ************************************************************

`

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## System Requirements

- UN*X Shell. Any standard `sh` shell should work. In particular, cascade has been tested under NetBSD, SunOs, and Solaris.
- `gawk` or `nawk`

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## Licensing

Cascade is available for free but is not in the public domain. Please refer to the license file for details.

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## Obtaining Cascade

Cascade is now hosted by SourceForge and can be downloaded via FTP at ftp://ftp.sourceforge.net/pub/sourceforge/rfcascade/ or via HTTP from http://prdownloads.sourceforge.net/rfcascade/.

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## Installation

Please refer to the file `INSTALL` that is part of the cascade distribution for details on installation.

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## Reporting Bugs

To report a bug, request a new feature, or participate in an online discussion forum about cascade, please visit the project's SourceForge Home.

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