I have n5244b network analyzer with 2.4mm cable but the cal kit has the adaptor of 2.92mm type and my dut has the sma connnector so i we connect a 2.4mm to 2.92mm connector during ecal and that we apply directly to dut. but the s11 parameter shows the problem. is this due to the connector mismatch?
Yes. 2.92 mm is "mateable" with 3.5 mm or SMA. But that doesn't mean it makes a good match. There is a step in the outer conductor size which makes a mismatch.