2.4GHz Single Balanced Mixer

Andrew Bacon

Jacqueline Griffin

John Stone

Mixer Specifications

IF Frequency: 140 MHzRF Frequency: 2400-2485 MHzRF Power: -10 dBmLO Frequency: 2260-2345 MHzLO Power: 8 dBmConversion Loss: > -9.5 dBLO-RF Rejection: < -20 dBLO-IF Rejection: <-30 dB

Mixer Design

Balun Design and Simulation

•Used an r of 2.9 for second layer to compensate for it being buried.

Diode Model and Simulation

Matching Design and Simulation

Find input impedance of diodes at 2.4 GHzDesign single stub network between

diodes and balunLet simulator optimize LC filter at output

Mixer Layout

LO Return

IF Block

LO Port

RF Port

Diode Matching Circuits

LC LPF

Coupler

IF Port

Diode

Ghetto Lettering

2.6 in

1.7 in

Resulting Board (Problems)

All holes that were supposed to be connected to ground were not

All holes that were not supposed to be connected to ground were

Missing parts of Traces

Mixer Board

Top View Bottom View

Measurement Methodology

Down Converter Used spectrum analyzer because it has low

error (~.1dB) Low frequency cable was taken out of

measurement through calibration High frequency cable was taken out of

measurement by measuring the response of the cable after measuring the mixer

Used spectrum analyser to measure IF rejection

Measurement Diagram (Down Converter)

IF RF

LO

2.260 000 00 GHz

Vector Network Analyzer

RF LO

LO Signal Generator

Downconversion Results

RF Freq

(GHz)

2.4 2.44 2.485 2.4 2.44 2.485

LO Freq

(GHz)

2.26 2.30 2.345 2.26 2.30 2.345

Conv. Loss

-10.78 -11.48 -13.00 -8.475 -8.588 -18.52

LO-IF Isolation (dBm)

-59.3 -60.5 -58.79 -71.37 -69.31 -69.99

Measurements Simulation

Downconverter MeasurementsRF Freq = 2.40 GHz RF Freq = 2.44 GHz

RF Freq = 2.485 GHz

Frequency Shift Measurements

Conversion Loss

-11.5

-11

-10.5

-10

-9.5

-9

-8.5

-8

1.73 1.83 1.93 2.03 2.13 2.23 2.33

Frequency (GHz)

Co

nve

rsio

n L

oss

Desired Frequency Response

Results

Adjusting the IF return led to being able to shift the frequencyBand up to 2.0 GHz on another board

If inductor were used this adjustment would be much easierAs stub is shorted to ground at end.

RF freq

Con

vers

ion

Lo

ss

Simulation Verification

RF freq (GHz)

Con

vers

ion

Lo

ss

Measurement Methodology

Up ConverterUsed spectrum analyzer

Measurement Diagram (Up Converter)

1 400000 00 MHz

2.260 000 00 GHz

IF RF

LO

IF Signal Generator

LO Signal Generator

Upconversion Spurious Levels

Freq Range (GHz)

Spurious

Spec

LO 2.26 GHz

LO 2.30 GHz

LO 2.345 GHz

LO 2.26 GHz

LO 2.30 GHz

LO 2.345 GHz

2.4-2.485

<-50 dBc -- -- -- -- -- --

2.485-2.90

< -40 dBc

-33.55

-43.9

-46.54 -40.43 -41.28

-36.85

-39.58

-41.91

-40.83

-43.53

2.325-2.40

< -40 dBc

-- -- -- -- -- --

1.0-2.212

<-30 dBc -36.62

-45.89

-35.92

-44.69

-35.89

-35.4

-49.77

-43.87

-44.06

-50.49

-41.35

-76.62

Measurements Simulation

Upconverter MeasurementsLO Freq = 2.26 GHz LO Freq = 2.30 GHz

LO Freq = 2.345 GHz

Upconverter Sweep Measurement• LO Frequency Swept from 2.26 GHz to 2.345 GHz

LO-RF Isolation

LO-RF Isolation

-30

-29

-28

-27

-26

-25

-24

-23

-22

2.26E+09 2.28E+09 2.30E+09 2.32E+09 2.34E+09

Frequency (Hz)

S21

dB

Simulations vs. Measurements

Possible Reasons for inaccuraciesFabrication (~.5dB)Inaccurate r

Multilayer simulation problems with ADS

Improvements

Use inductor for IF return (will allow more tuning)

Verify technology parametersVerify ADS’s simulation abilities

Questions