frequency sweep & single frequency using lpc2148(SPI) => ADF3450

Hi.... I need to sweep frequency from 138MHz to 4.4GHz.
How do I do it ..?

using lpc2148 (arm7) SPI.

Presumably you mean an ADF4350 from Analog Devices.

That is a very general question so you get a general answer:
Presumably you aim to build a device?
There are a few examples of projects built around the ADF4350 on the web, https://zl2bkc.com/projects/adf4350-pll/

Decide what controls you want, eg do you want an LCD screen to show current frequency and buttons to control operation
Decide how to supply 3.3volt power, you probably want a regulator on the board, do you need 5volts as well?
Read the datasheets of the parts you want to use
Produce a schematic
Read the datasheets again and check the schematic for errors
Design a PCB, it's going to be less hassle than trying to make VHF stuff work with wires
Consider high frequency requirement such as bypass capacitors close to the synthersizer, design a double sided board with a groundplane on the bottom
Get it made by a pcb manufacturer unless you really want to spend hours doing it yourself.
Get a simple test program running on the microcontroller, flash an LED or write "hello world" on your LCD
You probably want to write your software in C
Write software to make a sweep
Along the way figure out at least a dozen reasons that the hardware and software does not work first time.

If you want more a more specific answer you have to give more information about what you want the final device to look like and ask more specific questions