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Documentation:   Genesys 2010   >  Part Catalog   >  Mixers Category   >  Mixer (Basic) Part   >  MIXER_BASIC

This document contains references to Agilent Technologies. Agilent's former Test and Measurement business has become Keysight Technologies. For more information, go to www.keysight.com.


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MIXER_BASIC

Description: Basic Mixer
Associated Parts: Mixer (Basic) Part
Model Parameters

Name

Description

Default

Units

Type

Runtime Tunable

ConvGain

Conversion Gain

-8

dB

Integer

NO

SUM

Desired Output: 0-Difference, 1-Sum

0

 

Integer

NO

LO

LO Drive Level

7

dBm

Integer

NO

ISIDE

Image Side to Reject: 0-Below, 1-Above LO

0

 

Integer

NO

IR

Image Rejection

0

dB

Integer

NO

NF

Noise Figure

none

dB

Integer

NO

IP1dB

Input P1dB

1

dBm

Integer

NO

IPSAT

Input Saturation Power

2

dBm

Integer

NO

IIP3

Input IP3

11

dBm

Integer

NO

IIP2

Input IP2

21

dBm

Integer

NO

RTOI

RF to IF Isolation

100

dB

Integer

NO

LTOR

LO to RF Isolation

30

dB

Integer

NO

LTOI

LO to IF Isolation

30

dB

Integer

NO

ZR

RF Port Input Impedance

50

ohm

Integer

NO

ZI

IF Port Input Impedance

50

ohm

Integer

NO

ZL

LO Port Input Impedance

50

ohm

Integer

NO

InRevIso

Out to In Reverse Isolation

300

dB

Integer

NO

LORevIso

Out to LO Reverse Isolation

300

dB

Integer

NO

The basic mixer can be used as both an active or passive mixer. Both sum and difference products will always be created. The maximum order of products created at the output is determined by the Maximum Order property, which is set on the Calculate Tab in the System Analysis. Harmonics of the LO used in the mixing process is determined by getting the Fourier coefficients of a near square wave (52% duty cycle) and scaling them relative to the LO power. The LO along with all its harmonics are mixed with every input signal to produce both sum and difference frequencies. The operating point of the mixer is determined by the total RF and IF power driving the mixer. The mixer does know and doesn't care whether it is being driven from the RF or IF ports. As a matter of fact spectrums will propagate from the RF port to the IF port and vice versa. When multiple spectrums arrive at the RF or IF ports these spectrums generate intermods and harmonics which will be mixed with each harmonic of the LO.

Thermal noise arriving at the RF or IF is not mixed and does not create intermods and harmonics. However, this thermal noise will be folded at the LO frequency and extended to the maximum simulation frequency (Ignore Frequency Above). This process automatically accounts for noise at the image frequency.

Phase noise is also processed by the mixer. Mixed output spectrum is a combination of the input and LO spectrum phase noise.

This mixer can also be used to as an ideal image reject mixer. This is very handy when debugging image related RF architecture issues.

This mixer also has the ability to deal with reverse isolation. Mixed spectrum created by the mixer can be placed back at the mixer input as well as the LO. The amount of isolation can be controlled by the user.

WARNING: The LO power level must be within the tolerance range of the target 'LO Drive Level' or no mixed spectrum will be created!

NOTE: Compression effects of the LO drive are not accounted for in this model. Amplitudes of LO harmonics and intermods are strictly based on Fourier coefficients as described above.

Additional Parameter Information

Desired Output (SUM)

The parameter is used by Spectrasys to determine the correct channel frequency to use at the mixer output. When set to 0 the channel frequency at the output will be the difference between the channel frequency at the input minus the peak LO frequency. When set to 1 the channel frequency at the input will be the sum of the input channel frequency and the peak LO frequency. This parameter has no bearing on what type of mixed spectrums are created at the mixer output. Both sum and difference spectrum will always be created.

Image Side to Reject (ISIDE)

The mixer image frequency will be either above or below the LO center frequency for all difference products. When this parameter is set to 0 all frequencies of the input spectrum that are below the LO frequency will be attenuated by the image rejection amount. When set to 1 all frequencies of the input spectrum above the LO frequency, up to the maximum frequency of the spectrum will be attenuated by the image rejection amount.

For all sum products

the image frequency is that frequency where a difference will fall at the mixer sum frequency. For example, if the mixer input frequency was 1000 MHz with an LO frequency of 900 MHz a 100 MHz difference and 1900 MHz sum products would be created. If the desired output is the 1900 MHz sum then a 2800 MHz input frequency would be the image to the 1000 MHz input signal since 2800 - 900 MHz = 1900 MHz. For sum products the image side is irrelevant since the image will always be higher than the LO frequency. This image will always be greater than the desired input frequency. Consequently, image rejection for a sum product is defined as any input frequency which is greater than the frequency of the peak input signal.

Image Rejection (IR)

The amount of image rejection. When set to a nonzero value ALL spectrums, including noise, will be attenuated by this amount. The spectrum frequencies that will be attenuated are described in the 'Image Side to Reject' explanation.

Input Saturation Power (IPSAT)

Input level at which the mixer will saturate.

Input 2nd Order Intercept (IIP2)

This intercept point is referenced to intermods and not harmonics. See Second Order Intercept Differences for Mixers and Amplifiers for additional information.

Note: If the input saturation is greater than about 9 dB above the input 1 dB compression point the saturation power will be set to 3 dB above the 1 dB compression point.

Out to In Reverse Isolation (InRevIso)

This parameter controls the power level of the intermods and harmonics that will appear back on the input port and propagate backwards through the system. This parameter applies to both the RF port and IF port. IF output spectrum created by the RF and LO port signals will appear at the RF port and RF output spectrum created by the IF and LO port signals will appear at the IF port.

Out to LO Reverse Isolation (LORevIso)

This parameter controls the power level of the intermods and harmonics that will appear on the LO port and propagate backwards through the system. This parameter applies to both the RF port and IF port. IF output spectrum created by the RF and LO port signals will appear at the LO port as well as the RF output spectrum created by the IF and LO port signals.

 

Additional Operation Information

LO Drive Level

The LO drive level does not affect the power level of any of the spectrums created by the mixer other than the port to port isolation spectrum.  However, Spectrasys will look at this power level during the simulation and warn the user if the power level is outside the tolerance range specified in the 'System Analysis'. No spectrum at the output will be created unless the LO power level is within this tolerance range.

Mixed Spectrum Creation

Several spectrums may be present on the LO port of a mixer. Spectrasys has the ability to use only the peak LO signal or all LO signals that fall within a given power level range of the peak LO signal.  See the 'Options Tab' of the 'System Simulation Dialog Box' for more information of this setting.

Isolation Spectrum

All signals arriving at any mixer port will be propagated to the other mixer ports through their respective isolation's.

Reverse Isolation

The mixer will create reverse isolation products on the mixer RF and IF ports based on the reverse isolation parameters.

Mixer Thermal Noise Model

Thermal noise arriving at the RF or IF is not mixed and does not create intermods and harmonics. Noise arriving at the input is separated into 2 frequency bands. One below the LO frequency and the other above it. Depending on the mixer Input and LO frequencies one band will be in the main desired band of frequencies and the other will be in the image band. The location of these bands is determined by the 'LO Side to Reject' parameter. Frequencies falling into the Image band will be rejected by the 'Image Rejection' parameter. By default the image rejection is 0 dB. The mixer also generates self noise at both the main or desired frequency as well as the image frequency. This self noise is added to the input noise and then amplified by the conversion gain of the mixer at the main frequency and image frequency. All the noise is summed together at the mixer output.

Note

The main and image band conversion gains for behavioral mixer models are identical.

Caution

Image rejection does not affect the image self noise generated by the mixer. Image rejection only applies to noise signals appearing at the mixer input. Traditional cascaded noise measurements completely ignore both the mixer input noise at the image frequency and the mixer self generated noise at the image frequency.

Phase Noise

Phase noise is also processed by the mixer. Mixed output spectrum inherit the phase noise of the LO. When input spectrum have phase noise and there is no LO phase noise specified then the mixed spectrum will retain the phase noise of the input spectrum.

Phase

Output Phase = LO Phase + Input Phase (Sum)
Output Phase = LO Phase - Input Phase (Difference for High LO Side Injection )
Output Phase = Input Phase - LO Phase (Difference for Low LO Side Injection )

Output Intermod and Harmonic Phase

The output phase of an intermod is based on the phase of the input signals and the coefficients of the intermod equation. However, the polynomial coefficients that represent the Vin versus Vout curve have negative coefficients for all odd orders 3rd and higher. This means that odd orders of 3rd and higher will have a phase shift of 180 degrees. These negative odd coefficients keep the transfer function from increasing monotonically.
 
Output Phase = +/- K * Input1Phase +/- M * Input 2 Phase +/- N * Input 3 Phase ...
 
Where K, M, N, etc are the coefficients of the intermod equation.
 
For example, the phase of the 2nd harmonic will be double the input phase, triple the input phase plus 180 degrees for a 3rd harmonic etc.

Image Frequency

The image frequency is an alternate frequency at the input of the mixer that will produces the same IF output frequency as the desired input frequency. For example, if the desired mixer input signal is 800 MHz with an LO frequency of 900 MHz then the difference IF output frequency is 100 MHz. However, a input frequency of 1000 MHz when mixed with the same 900 MHz LO will also produce a 100 MHz IF frequency. The 1000 MHz is the image of the desired 800 MHz input frequency.

Image Frequencies are located at the following frequencies:

Sum:

Fimage = 2 * Flo + Frf

Difference:

Fimage = 2 * Flo - Frf

Orders Generated by Multiple Input Spectrums

When multiple spectrums arrive at the RF or IF ports they will generate intermods and harmonics based on the nonlinear transfer function defined by the nonlinear parameters (IP1dB, IPSAT, IIP3, IIP2). A maximum of 3 orders will be created since these nonlinear parameters only support a 3rd order transfer function. However, this should not be confused with the maximum order of the mixer output products. The input products order is limited to 3 but higher order LO products can be used until the maximum simulation order is reached.

SVNI

(Stage Equivalent Input Noise Measurement) - Voltage Based)

When the voltage based measurement SVNI is used on this mixer the real value of the RF port input impedance is used to determine the source resistance.

Input Self Mixing

Mixer input signals leak to the LO and will mix with themselves in non-ideal mixers. This is called RF ( or input self mixing since the input port can be the IF port ) self mixing. The DC value output is = 2 x Signal Input Power - Mixer IIP2 (dBm). The bandwidth of the spectrum at DC will be the same bandwidth as the mixer input spectrum. Since a 2nd harmonic has double the bandwidth of the fundamental and the self mixing product exists at DC, only the positive half of the intermod will be seen which is equivalent to the input spectrum bandwidth.

DC Block

DC is blocked.

WARNING: Only the linear portion of this model is used in simulators other than Spectrasys. The linear model is the port impedance coupled with the isolation parameters.

NOTE: RF to IF isolation is used not the conversion gain. Conversion gain is not used since this is a nonlinear process.

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