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How to make a I/Q modulator?

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yuhohang

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iq modulator sige

Dear All
Is it possible use discrete components to make a I/Q modulator?
 

flatulent

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Yes

Yes it certainly is possible. Your problem will be matching components for making the carrier feed through initially low and stay low over temperature and time.
 

dd22

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This is depend on what kind of modulation you need.
 

ttosolee

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hi, yuhohang

this may usful document from mini circuit.
I&Q and QPSK Modulators/Demodulators: most often asked questions
 

toonafishy

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You need two mixers, a 90 degree phase network. But I would expect pretty poor carrier/sideband supression since the circuit must be very balanced.
 

jwei363

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re

theoretically,you can make all ic by discrete componets.but why not use ICs?
 

adolfchen

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yuhohang said:
Dear All
Is it possible use discrete components to make a I/Q modulator?
You should tell us clearly what kind of modulation you need.
Maybe there are existing ICs to fit in with your requirement.
 

martin

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Any example for pi/4 - DQPSK modem ? "Mini" circuits is preferred!
thanks!
 

BigBoss

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It's obviously possible to make a IQ Modulator.

There will be 8 transistor for full differential Gilbert cell and " Current Transducer " to control the currents of the each pairs.

But some pitfalls may ocur . You may not provide the symmetricity and if
there become 15-20 degree phase error , at the output this will return back with poor sideband rejection and LO rejection.
Instead of this , using ready-to use IQ modulator is more efficient.
Philips SA 900 is very useful Transmit IQ Modulator.
Datasheet and App. report are attached here.


GL
 

martin

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please send me documents about IQ modulator

Hi, BigBoss
can you me send me " design" documents about IQ modulator ?
 

Needbias

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how to measure accurately a IQ mixer?

A new question:how to measure a IQ mixer's amplitude and phase error accurately?

Now I should design a 9~10GHz IQ mixer,the IF is DC to 100MHz.
As I know,The HP 8753C or HP 8753D's freq offset mode can be used to measure the phase track of IQ mixer,but this network analyses's can not be used up to 6 GHz.whoever know any other method to measure it accurately?
 

Wacko2000

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What frequency range do you need?

There are a lot of good integrated circuits available at this moment which are good enough for most applications.

Take for example Analog Devices, Maxim etc.
 

Wacko2000

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I mean with above posting something like:
Why making your own I/Q mod with discrete components when cheap and good IC's exists.

Otherwise build your own with some Mini Circuit components if you call that 'discrete'

regards
 

trifilinux

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yuhohang said:
Dear All
Is it possible use discrete components to make a I/Q modulator?
Hi, I am designing one using SiGe Bicmos technology, if you are interested don't hesitate to ask more information.

Trifilinux
 

prd

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I want to test baseband circuit.
Modulator has baseband IQ output and Demodulator receive 10.8 MHz input.
Are there any IC match or how to test it anyway.
The only idea I get is to build IQ modulator to output at 10.8MHz
Do you have any idea?

prd
 

IICCEE

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you may use the easy way of R/C and C/R to get the 45degrees and -45degrees phase and using the diode as a MIX.
 

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