To sekharareddy,
Your idea is absolutely right. You need to have a few boards each for one of the SOLT calibration procedures. The only question is what is your frequency range? You know that calibrations kits are very expensive and it is because they made to work precisely in wide frequency range. If your application is only for GPS, or about 1500 MHz it is not so hard to build calibration boards. However, there are some points to consider. All traces must be really 50 Ohm, better to use coplanar wave guide than microstrip. SHORT one should be really short and here CPW is much better. Shorting must be done for both sides of the connector’s central pin and despite CPW via to ground plane must be place around. Via diameter about 15 mils is good and the spacing about 30 to 50 mils should be okay. Distance from via center to edge of CPW ground is about 2 via diameters or 30 mils. What is extremely important it is to solder the central pin of connectors along all the length. This is the tricky case because PCB manufacturers often want to stop copper about 0.25 to 0.5 mm (10 to 20mils) from the edge of the board. This will completely kill you standard. Never use SMA connectors designed to install vertically. Use only horizontal end-launch SMAs, desirable those that eliminate unsoldered part of the central pin to be hanging in the air. Footprint for chosen connector is also important. All the traces and ground planes must go to the very edge of the board! Just imaging those 20 mils of the central pin is sitting in the air. It is about 0.5 nH of inductance, which is about 3 Ohm at 1 GHz or about 5 Ohm at GPS frequency. It is not so good standard for calibration if it has series connected 5 Ohm reactance for each of connectors. All board must be kept as small as it possible (RF part of course, there may be empty space for convenience), except the THRU one. This board must have the length which is corresponds to the real one. The 50 Ohm load standard is also very tricky. It is better to install two resistors 100 Ohm each for both sides of the central pin to the CPW ground. The 0402 size should be okay for GPS frequencies. Pay special attention to the robustness of the boards. Very often they are under the stress from cable tension and develop some micro cracks or may be broken. Install stiffeners, but be careful not to damage the ground plane under them. Finally, it is good idea to check your standards with TDR.
There is one more good opportunities to use such homemade boards. You can make small board that have two connectors and 50 Ohm loads. All traces are the same as on the test board. Then you measure S-parameter file (s2p) for input connector, then for output connector and save them. After these calibration procedures you measure your device under test (DUT) and save S-parameter file. After this you may use RF simulator or special calculator (for example in LINC2 RF simulator) and de-embed connectors and traces from test board S-parameter files. This will allow you to have pure S-parameter file for your device with test conditions what you need, not those that vendor provided.
I hope this information will be helpful.
Best regards,
RF-OM
Added after 8 minutes:
To GVVIN,
Your concern about antenna is right, but today's GPS receiver has sensitivity well below -165dBm (yes, close to kTB). A couple of years ago I participated in GPS chip design and this chip worked very well in the lab. Mass production receiver worked well under the seat in the car. I believe there should be no problem now.
Best regards,
RF-OM