Handle insertion loss variation of Analog Phase Shifter based on Varactor Diode

Hi everyone,
I am a junior engineer in RF and Microwave field.
I am working on 360 Analog Phase Shifter at ISM band, and I am trying to handle the large insertion loss variation. I found a good paper for this problem and follow this paper.
I rework and simulate the proposed circuit in this paper, but I cannot get results similar to paper.
Although I have spent the whole week on checking my simulation, I am still not able to know where error is, so I hope that someone can help me check my simulation and rework this paper if possible. After that give me some comment.

Thanks so much for your time and help.

[Edited by moderator: removed copyrighted paper in attachment]

Hi everyone,
I am a junior engineer in RF and Microwave field.
I am working on 360 Analog Phase Shifter at ISM band, and I am trying to handle the large insertion loss variation.
I found a good paper for this problem.
http://ieeexplore.ieee.org/document/4298211/
I rework and simulate the proposed circuit in this paper, but I cannot get results similar to paper. To be more specific, insertion loss still significantly change when I control bias voltage, and the relative phase shift is much less than results in paper.
Although I have spent the whole week on checking my simulation, I am still not able to know where error is, so I hope that someone can help me check my simulation and rework this paper if possible. After that give me some comment.

The main idea of paper is that:
+ Authors parallel resistor Rp with varactor diode that have parasitic resistance close to 2ohm so that insertion loss becomes independent on reactance of varactor.
+ At the same time, authors modify the impedance of each branch of branch-line coupler in order to dramatically improve phase shifter (from 97 degree to 237 degree).

P/s: My simulation in attachments
AnalogPhaseShifter.rar
Thanks so much for your time and help.

You missed to report actual results, both your implemented circuit and the achieved performance (phase and attenuation versus control voltage) should be given.

I don't know how your design looks, but a good topology for low insertion loss phase shifter using varicap diodes, is a high-pass configuration.
The extra insertion loss of the circuit happen when parasitic resonances of the circuit occur.

my guess is that your varactor diode is not actually "series resonated", as is required in the first step of the paper. That tiny series inductor has to be carefully chosen so that the phase shift is on the order of 0 to 270 degrees as the voltage swings from zero to Vmax .

Normally, without the series inductance, you would not get even half of that phase shift. So are you getting the full phase shift? If not vary the inductor value until you do. THEN add the parallel resistance, starting with a very high value, until the insertion loss at the bias voltage extreemes is roughly flat.

you, of course, will need TWO SUCH STRUCTURES to get a full 360 degrees, ie. using one phase shifter for 0 to 180 degrees, and the 2nd phase shifter to reach 181 to 360 degrees total phase shift.