OpenIF class

Find open intermediate frequencies (IFs) in multiband transmitter or receiver architecture

Description

Use the OpenIF class to analyze the spurs and spur-free zones in a multiband transmitter or receiver. This information helps you determine intermediate frequencies (IFs) that do not produce interference in operating bands.

Construction

hif = OpenIF creates an intermediate-frequency (IF) planning object with properties set to their default values.

hif = OpenIF(Name,Value) creates an intermediate-frequency (IF) planning object with properties with additional options specified by one or more Name,Value pair arguments.

hif = OpenIF(bandwidth) creates an intermediate-frequency (IF) planning object with a specified IF bandwidth.

hif = OpenIF(bandwidth,Name,Value) creates an IF-planning object with a specified IF bandwidth and additional options specified by one or more Name,Value pair arguments.

Input Arguments

bandwidth

Specify the bandwidth of the IF signal. The bandwidth is a real positive scalar. The value you provide sets the IFBW property of your object. You can also set this property using an optional name-value pair argument.

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments, where Name is the argument name and Value is the corresponding value. Name must appear inside single quotes (' '). You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

'IFLocation' — IF location'MixerOutput' (default) | 'MixerInput'

Specify an up-conversion or down-conversion setup during object construction. The value you provide sets the IFLocation property of your object.

'IFBW' — IF bandwidthnonnegative number

Specify the IF bandwidth during object construction. The value you provide sets the IFBW property of your object. You can also set this property using the optional bandwidth input argument.

'SpurFloor' — Spur floornonnegative number

Specify the spur floor during object construction. The value you provide sets the SpurFloor property of your object.

Properties

IFLocation

Specify an up-conversion or down-conversion setup.

  • Setting IFLocation to 'MixerInput' specifies an up-converting (transmitting) configuration, where one IF is mixed up to multiple RFs. The following figure shows this convention.

  • Setting IFLocation to 'MixerOutput' specifies a down-converting (receiving) configuration, where multiple RFs are mixed down to one IF. The following figure shows this convention.

The setting of IFLocation determines the available values for the injection argument of the addMixer method.

Default: 'MixerOutput'

IFBW

Bandwidth of the IF signal in Hz. When you construct the object, the bandwidth argument specifies the value of this property.

Mixers

Vector of objects that holds mixer information. When you add mixers using the addMixer method, you also add an OpenIFMixer object to the Mixers vector of your original OpenIF object.

The following table lists the properties of each OpenIFMixer object.

PropertyDescription
IMTIntermodulation table of the mixer.
RFCFRF center frequency, in Hz.
RFBWRF bandwidth, in Hz.
MixingTypeMixing (injection) type.
SpurVectorVector of spur information.

The IMT, RFCF, RFBW, and MixingType properties are required inputs to the addMixer method.

NumMixers

Number of mixers. When you use the addMixer method, the number of mixers increases by one. The likelihood of finding an open IF decreases as you add mixers.

SpurFloor

Maximum difference in magnitude between a signal at 0 dBc and an intermodulation product that the OpenIF object considers a spur. The default value of this parameter is 99, corresponding to a spur floor of –99 dBc.

Methods

addMixerAdd mixer to multiband transmitter or receiver for IF planning analysis
getSpurDataFind spurs in multiband transmitter or receiver frequency space
getSpurFreeZoneDataFind spur-free zones in multiband transmitter or receiver frequency space
reportSummarize mixer configurations and spur-free-zone information for a multiband transmitter or receiver
showProduce spur graph for multiband transmitter or receiver

Copy Semantics

Handle. To learn how handle classes affect copy operations, see Copying Objects in the MATLAB® documentation.

Examples

expand all

Spur-free zones of a multiband receiver

Set up an OpenIF object as a multiband receiver, add three mixers to it, and obtain information about its spur-free zones.

Define an OpenIF object. The first input is the bandwidth of the IF signal (50 MHz). The 'IFLocation','MixerOutput' name-value pair specifies a downconverting configuration.

hif = OpenIF(50e6,'IFLocation','MixerOutput');

Define the first mixer with an intermodulation table and add it to the OpenIF object. Mixer 1 has an LO at 2.4 GHz, has a bandwidth of 100 MHz, and uses low-side injection.

IMT1 = [99 00 21 17 26; ...
        11 00 29 29 63; ...
        60 48 70 65 41; ...
        90 89 74 68 87; ...
        99 99 95 99 99];
addMixer(hif,IMT1,2.4e9,100e6,'low');

Mixer 2 has an LO at 3.7 GHz, has a bandwidth of 150 MHz, and uses low-side injection.

IMT2 = [99 00 09 12 15; ...
        20 00 26 31 48; ...
        55 70 51 70 53; ...
        85 90 60 70 94; ...
        96 95 94 93 92];
addMixer(hif,IMT2,3.7e9,150e6,'low');

Mixer 3 has an LO at 5 GHz, has a bandwidth of 200 MHz, and uses low-side injection.

IMT3 = [99 00 15 23 36; ...
        10 00 34 27 59; ...
        67 61 56 59 68; ...
        97 82 81 60 77; ...
        99 99 99 99 96];
addMixer(hif,IMT3,5e9,200e6,'low');

The multiband receiver is fully defined and ready for spur-free-zone analysis. Use the report method to analyze and display spur and spur-free zone information at the command line. The method also returns information about the mixers in the receiver.

hif.report
     Intermediate Frequency (IF) Planner
     IF Location: MixerOutput
     
     -- MIXER 1 --
     RF Center Frequency: 2.4 GHz
     RF Bandwidth: 100 MHz
     IF Bandwidth: 50 MHz
     MixerType: low
     Intermodulation Table:   99   0  21  17  26
                              11   0  29  29  63
                              60  48  70  65  41
                              90  89  74  68  87
                              99  99  95  99  99
                            
     -- MIXER 2 --
     RF Center Frequency: 3.7 GHz
     RF Bandwidth: 150 MHz
     IF Bandwidth: 50 MHz
     MixerType: low
     Intermodulation Table:   99   0   9  12  15
                              20   0  26  31  48
                              55  70  51  70  53
                              85  90  60  70  94
                              96  95  94  93  92
                            
     -- MIXER 3 --
     RF Center Frequency: 5 GHz
     RF Bandwidth: 200 MHz
     IF Bandwidth: 50 MHz
     MixerType: low
     Intermodulation Table:   99   0  15  23  36
                              10   0  34  27  59
                              67  61  56  59  68
                              97  82  81  60  77
                              99  99  99  99  96
                            
     Spur-Free Zones:
      350.00 -  430.00 MHz
      530.00 -  556.25 MHz
      643.75 -  655.00 MHz
        1.38 -    1.41 GHz
        2.10 -    2.17 GHz
        2.28 -    2.29 GHz
     

Use the show method to analyze the receiver and produce an interactive spur graph. Generating a spur graph is a convenient way to summarize the results of the analysis graphically.

figure;
hif.show

References

Faria, Daniel, Lawrence Dunleavy, and Terje Svensen. "The Use of Intermodulation Tables for Mixer Simulations." Microwave Journal. Vol. 45, No. 4, December 2002, p. 60.

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