Parameters of a metrology tool may be determined by measuring a dimension of a feature on a calibration standard with the tool and using the measured dimension and a known traceable value of the dimension to determine a value for the parameter. When a server receives a request from a client, a message combining system of the server sends a response to the request that includes the content of a request that the server would normally send to the client in a separate request. The following conditional expression is satisfied: 0. The planar patch element may relate to a full wave loop antenna as a compliment.