The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> RF Design >> Phase shifter help! Thanks!
https://designers-guide.org/forum/YaBB.pl?num=1385320496

Message started by ccarrot on Nov 24^th, 2013, 11:14am

Title: Phase shifter help! Thanks!
Post by ccarrot on Nov 24^th, 2013, 11:14am

Hi,

I'm going to design a phase shifter with 360 degree tuning range. It works between 100MHz-200MHz, i.e. the input signals are two quadrature digital inputs with f=100-200 MHz.

I checked a lot of references, but they usually works at RF band. I tried a current-steering topology (as shown below), but i'm not able to make it work I think it is because 100-200 MHz is very low.

Is anybody can help me out?
(1) Will current-steering topology work at 100-200MHz?

(2) Any circuit advised?

Thank you!

[img][/img]

Title: Re: Phase shifter help! Thanks!
Post by aaron_do on Nov 24^th, 2013, 4:42pm

Hi,

based on your schematic, I can't see how you could get more than 90 degrees phase shift.

Aaron

Title: Re: Phase shifter help! Thanks!
Post by ccarrot on Nov 25^th, 2013, 11:54am

aaron_do wrote on Nov 24^th, 2013, 4:42pm:

Hi,

based on your schematic, I can't see how you could get more than 90 degrees phase shift.

Aaron

Hi Aaron,

Actually I'm going to build two blocks of this, this one can get 0-90 degree with combining the phi_1 and phi_2, the other block combines phi_2 and phi_3 ---- can I design like this? I'm new to the phase shifter design, I'm so appreciated if you could give some advice, thank you!!

From the simulation, I noticed that in high frequency, the output nodes rise and fall very fast between non-zero and non-vdd voltage level. However, in 100 MHz, they are rising from 0 to VDD through some steps, and hardly to see the shift steps. Is this circuit right for low frequency application? Or there is some other techniques?

I'm still googling online, but still not be able to find a good solution. Thank you for your help!

Title: Re: Phase shifter help! Thanks!
Post by aaron_do on Nov 25^th, 2013, 4:19pm

Hi,

I haven't designed a phase shifter either, but anyway the idea looks like it should work. The only thing I can see is that the output amplitude will depend on the phase shift. If your circuit is having problems, posting waveforms helps. Also, make sure all of your DC biasing is correct.

regards,
Aaron