how to design a IF input stage for superheterodyne receiver

[mydreamhouse]

who can tell me how to design a IF input stage for superheterodyne receiver
the IF frequency is about 180MHZ,and followed by external LC BPF.
as i known, the IF LC BPF must be match with IF input stage,but i don't know how to design it.(if the BPF matched resister is low, is it necessary to design a COMMOM GATE(CG) stage to match the LC BPF? or directly Gate input?(CS).

 

[vfone]

Re: how to design a IF input stage for superheterodyne recei

An option is to use a diplexer placed after the mixer, followed by the LC BPF.
The LC BPF shall be matched on 50 ohms on both sides, to optimize for a low in-band ripple and low insertion loss.
The first IF stage will be also matched for 50 ohms at its input.

 

[mydreamhouse]

Re: how to design a IF input stage for superheterodyne recei

i know the first IF stage must be matched with BPF,but what structure of the input stage is used usually in superheterodyne receiver,CS,CG,CD?,thanks!

 

[vfone]

Re: how to design a IF input stage for superheterodyne recei

CG

 

[mydreamhouse]

Re: how to design a IF input stage for superheterodyne recei

can you give me some reference about it ,thanks

 

[Abhishekabs]

Is it that CG has low impedance,that's why this configuration is used?

 

[mydreamhouse]

Re: how to design a IF input stage for superheterodyne recei

may i use CS IF input stage and a resistor is add between GATE for matching? my IF frequency is about 200MHZ.

 

[vfone]

Re: how to design a IF input stage for superheterodyne recei

Use LC network for matching and resistors for bias.

 

[mydreamhouse]

Re: how to design a IF input stage for superheterodyne recei

LC matching is used when frequency is higher than 500MHZ in most commercial product, why?

Added after 2 minutes:

i mean when frequency is lower than 500MHZ, few products use LC matching

 

[vfone]

Re: how to design a IF input stage for superheterodyne recei

Whatever frequency is used a resistive matching introduce the same noise figure degradation.
A reactive matching network (LC) will introduce minimal losses.