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zero-IF receiver chip design

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shilong_xu

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gps zero_if

hi,guys
someone can tell me the designing difference between zero-IF and Heterodyne receiver?
(1)including system design and component design considerations
(2)does the zero-IF need the 100dB gain same to Heterodyne structure in GPS application?

thanks
 

nitu

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Hi..

I will recommend that you refer book
"RF System Design of Transceivers for Wireless Communications " by Qizheng Gu.
It deals with both Heterodyne as well as Zero IF receiver architecture and their design considerations.
 

safwatonline

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in zero if u deal with flicker noise but u don't need an Image reject filter also ur signal is DSB while in superheterodyne u need an image reject(or some complex mixing technique,,,complex as in not real not as in complicated) u are usally away from flicker noise ,u use SSB NF
 

drabos

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Zero IF: the main problem is DC offset
you need to determine the IP2 (not only the IP3), because the second order terms are your enemies if you design a zero IF receiver.
 

elec350

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Can you explain for me about differences between zero-if and double conversion concepts. which is better.
 

khouly

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zero IF , mean that ur local oscillator frequency is the same as the carrier frequency so when they mixed , the output is the base band signal

double conversion , mean that there is two mixers in the system first u down convert the RF to some IF frequency and then u can down convert it to base band


every architecture has it's pors and cons
in modern receiver specially single chip ones the ZIF is used as the architecture of the system

khouly
 

drabos

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the superheterodyn receiver has a problem called image problem
So it needs filters to reject the image.
 

shilong_xu

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but if i have the system specifications? how to select original schemetic for each unit component, such as LNA, Mixer et.al,
thanks
 

drabos

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what is the question exactly?

I can understand that:
you have a specification,(sensitivity, frequency, bandwidth, spectral mask, noise figure, SNR ...) and you want to design the receiver. First of all, you have to know what type of technology will be used. You have to be an idea about what knows the technology.
And you design the receiver, so you give the specifications for the LNA, mixer, LO, demodulator,.... and thinking about the antenna as well, you think about the filters and make a system simulation ( I recommend MATLAB for it). If the results are good ( so satisfy the original specifications), you design the circuits, and now you select the schematics for the components. So you select the original schematics due to the specifications and then you optimize them(and simulate the system), and then you design them physically. And when they are ready you simulate the system and if it's good then you make the circuits and then you test it. and if it's good, you will be very happy.
 

pablohoney

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Zero_IF: problem is DC offset, advantage is integration, low-cost, no mirror frequencies, no image reject (IR) filters.
Heterodyne: Image problem, IR filters needed.
 

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