lcladder

Create LC ladder network

Description

Use an lcladder object to:

• Create an LC ladder filter.

• Convert an rffilter object to an LC ladder.

• Build a circuit object with an LC ladder element.

• Model an LC circuit in cascaded stages using an rfbudget object or the RF Budget Analyzer app.

Creation

Syntax

lcobj = lcladder(top,L,C)

lcobj = lcladder(rffilterobj)

lcobj = lcladder(___,lcname)

Description

lcobj = lcladder(top,L,C) creates an LC ladder object lcobj and sets the Topology, Inductances, and Capacitances properties.

lcobj = lcladder(rffilterobj) creates a LC ladder object lcobj from an RF filter object rffilterobj.

lcobj = lcladder(___,lcname) creates an LC ladder object lcobj and sets the Name property. Specify lcname after all other input arguments.

Input Arguments

rffilterobj — RF filter object

rffilter object

RF filter object, specified as an rffilter object.

Example: lcobj = lcladder(rffilterobj)

Properties

Topology — Topology type of LC ladder

'lowpasspi' | 'lowpasstee' | 'highpasspi' | 'highpasstee' | 'bandpasspi' | 'bandpasstee' | 'bandpasstee' | 'bandstoppi' | 'bandstoptee'

Topology type of the LC ladder, specified as one of the following:

• 'lowpasspi' — Low-pass pi filter

• 'lowpasstee' —Low-pass tee filter

• 'highpasspi' — High-pass pi filter

• 'highpasstee' — High-pass tee filter

• 'bandpasspi' — Band-pass pi filter

• 'bandpasstee' — Band-pass tee filter

• 'bandstoppi' — Band-stop pi filter

• 'bandstoptee' — Band-stop tee filter

Example: 'lowpasspi'

Inductances — Inductor values in LC ladder

inductor object | numeric scalar | two-element vector

Inductor values in the LC ladder, specified as an inductor object or as a numeric scalar or two-element vector in henries.

Example: 1e-9

Capacitances — Capacitor values in LC ladder

capacitor object | numeric scalar | two-element vector

Capacitor values in the LC ladder, specified as a capacitor object or as a numeric scalar or two-element vector in farads.

Example: [2e-12 3e-12]

Name — Name of LC ladder object

'lcfilt' (default) | character vector | string scalar

Name of the LC ladder object, specified as a character vector or string scalar.

Example: 'lcfilter'

NumPorts — Number of ports in LC ladder object

Read-only: 2 (default) | positive scalar

This property is read-only.

Number of ports in LC ladder object. specified as a positive scalar.

Terminals — Terminal names of LC ladder object

Read-only: {'p1+' 'p2+' 'p1-' 'p2-'} | cell vector

This property is read-only.

Terminal names of LC ladder object, specified as the cell vector, {'p1+' 'p2+' 'p1-' 'p2-'}. An LC ladder object always has four terminals: two terminals associated with the first port ('p1+' and 'p1-') and two terminals associated with the second port ('p2+' and 'p2-').

Example: {'p1+' 'p2+' 'p1-' 'p2-'}

ParentNodes — Parent circuit nodes connected to LC ladder object terminals

vector of integers

Parent circuit nodes connected to LC ladder object terminals, specified as a vector of integers. This property appears only after the LC ladder object is added to a circuit.

Note

ParentNodes are only displayed after the capacitor has been added into a circuit.

ParentPath — Full path of the circuit to which the LC ladder object belongs

character vector

Full path of the circuit to which the LC ladder object belongs, specified as character vector. This path appears only after the inductor is added to the circuit.

Note

ParentPath is only displayed after the capacitor has been added into a circuit.

Object Functions

sparameters	Calculate S-parameters for RF data, network, circuit, and matching network objects
groupdelay	Group delay of S-parameter object or RF filter object or RF Toolbox circuit object
clone	Create copy of existing circuit element or circuit object
rfplot	Plot S-parameter data

Examples

Create Low-Pass Pi LC Ladder Object and Plot S-Parameters

Create a low-pass pi LC ladder object with an inductor value of 3.18e-8 H and a capacitor value of 6.37e-12 F. Calculate and plot the s-parameters.

L = 3.18e-8;
C = [6.37e-12 6.37e-12];
lpp = lcladder('lowpasspi',L,C)

lpp = 
  lcladder: LC Ladder element

        Topology: 'lowpasspi'
     Inductances: 3.1800e-08
    Capacitances: [6.3700e-12 6.3700e-12]
            Name: 'lcfilt'

freq = 0:1e6:1e9;
S = sparameters(lpp,freq);
rfplot(S)

You can also add this LC ladder to a circuit.

c = circuit;
add(c,[1 2 0 0],lpp)
setports(c,[1 0],[2 0])

Design RF Chain with LC Ladder

Design a low-pass pi LC ladder circuit.

L  = 1e-9;
C = [1e-12 1e-12];
lpp = lcladder('lowpasspi',L,C);

Design a default transmission line delay lossy and lossless objects.

tx1 = txlineDelayLossless;
tx2 = txlineDelayLossy;

Create an rfbudget object to design an RF chain.

b = rfbudget([tx1 lpp tx2 ],2.1e9,-30,100e6,'Solver','HarmonicBalance')

b = 
  rfbudget with properties:

               Elements: [1x3 rf.internal.rfbudget.Element]
         InputFrequency: 2.1 GHz
    AvailableInputPower: -30 dBm
        SignalBandwidth: 100 MHz
                 Solver: HarmonicBalance
                WaitBar: true
             AutoUpdate: true

   Analysis Results
        OutputFrequency: (GHz) [       2.1        2.1        2.1]
            OutputPower: (dBm) [       -30     -30.87     -30.87]
         TransducerGain: (dB)  [-6.514e-10     -0.868    -0.8683]
                     NF: (dB)  [-2.132e-14 -2.132e-14  0.0003759]
                   IIP2: (dBm) [       Inf        Inf        Inf]
                   OIP2: (dBm) [       Inf        Inf        Inf]
                   IIP3: (dBm) [       Inf        Inf        Inf]
                   OIP3: (dBm) [       Inf        Inf        Inf]
                    SNR: (dB)  [     63.98      63.98      63.97]

Use the show command at the command line to visualize the RF budget chain in the RF Budget Analyzer app. You can also do further analysis on this chain using the app. For more information, see RF Budget Analyzer.

show(b)

Version History

Introduced in R2013b

R2023b: Recommenced over rfckt.lcbandpasspi, rfckt.lcbandpasstee, rfckt.lcbandstoppi, rfckt.lcbandstoptee. rfckt.lchighpasspi, rfckt.lchighpasstee. rfckt.lclowpasspi, and rfckt.lclowpasstee

lcladder is recommended over rfckt.lcbandpasspi, rfckt.lcbandpasstee, rfckt.lcbandstoppi, rfckt.lcbandstoptee. rfckt.lchighpasspi, rfckt.lchighpasstee. rfckt.lclowpasspi, and rfckt.lclowpasstee objects because it enables you to:

• Create a two-port:

  • Low-pass pi filter

  • Low-pass tee filter

  • High-pass pi filter

  • High-pass tee filter

  • Band-pass pi filter

  • Band-pass tee filter

  • Band-stop pi filter

  • Band-stop tee filter

• Convert an rffilter object to an LC ladder.

• Build a circuit object with an LC ladder element.

• Model a lumped filter element in an RF chain created using an rfbudget or the RF Budget Analyzer app, and then export this element to RF Blockset™ or to rfsystem System object™ for circuit envelope analysis.