Upconverter with with wide output frequency range

Hi All,
I have to design a 720 Mhz IN- 8-8.4 Ghz OUT Upconverter with the following specs:

1 khz step
Spur: < -60 dbc
PN: -70 dbc @ 10 khz

When I use the ADISimPLL sw for a tuning range of 400 Mhz and 1 khz step I get high phase noise characteristics.

Any suggestions?

If the IF input is 720 MHz, how you get the 8.0-8.4 GHz output? I would advise not to tune the LO frequency, most mixers do not like it and gain ripple is the result.
Phase noise of a multiplied-frequency source is the reference PN scaled by frequency: PN out = PN ref + 20 log F/f ref + 3 dB

My Plan is as follows:

720 MHz IN
MIXER <-------- LO: PLL1: 1800-1810 MHz 1 kHz step
BPF
2520-2530
MIXER <-------- LO: PLL2: 5480-5870 MHz 10 MHz step
BPF
8000-8400 out

Is this approach wrong?

The approach is correct. In my experience, tuning the LO over a wide band like 5.48-5.78 GHz may require good filtering and rejecting LO harmonics from entering the mixer(s). In upconverters, the result is often the conversion-loss ripple. Be ready to design good RF and LO pass-band filters. As the first and second LO are linked: LO1 x 3 ~ LO2, you may find some problems when you test the system in the end.

In my experience I rather preferred tuning the IF while the LO stayed fixed.

To upconvert this signal, I think a single step upconverting is enough.In order to do this, a VCO can be used such as
http://www.macomtech.com/datasheets/MAOC-009264.pdf
and a high performance mixer such as
http://www.hittite.com/content/docum...t/hmc171c8.pdf
The alternatives can be found of course but upconverison in 2 steps will increase the complexity and noise and spurs.
The best circuit which the simplest one...

Single step requires a BPF with a 3db BW of 8-8.4 Ghz and attenuation of 7.3-7.7 Ghz LO.