A housing suitable for containing a planar circuit substrate, comprising: an upper and a lower housing part (650, 642) which contact each other with contacting surfaces; a support portion within the housing for supporting edges of the planar circuit substrate, the support portion being provided as a groove in an internal surface of at least one housing part, said groove extending in a direction perpendicular to said internal surface; an upper cavity in the upper housing part located above the planar circuit substrate when supported by the support portion; and a lower cavity in the lower housing part located below the planar circuit substrate when supported by the support portion, the lower cavity having the same dimensions as the upper cavity in directions parallel with the plane of the planar circuit substrate when supported by the support portion; electrically conductive fixing members arranged to both fix resiliently the planar circuit substrate in the housing and electrically connect the planar circuit of the planar circuit substrate to the housing; and separation walls between one of the cavities and concave portions within the housing part having said one of the cavities, said concave portions containing further conducting members for electrically connecting the planar circuit to the housing; and wherein: the lower housing part comprises an integral cooling stage for improving thermal conduction; and the contacting surfaces of said two housing parts (650, 642) have a stepped profile when viewed in cross-section in a plane perpendicular to the planar circuit substrate when supported by the support portion, the stepped profile preventing penetration of electromagnetic waves into the housing. an upper and a lower housing part (650, 642) which contact each other with contacting surfaces; a support portion within the housing for supporting edges of the planar circuit substrate, the support portion being provided as a groove in an internal surface of at least one housing part, said groove extending in a direction perpendicular to said internal surface; an upper cavity in the upper housing part located above the planar circuit substrate when supported by the support portion; and a lower cavity in the lower housing part located below the planar circuit substrate when supported by the support portion, the lower cavity having the same dimensions as the upper cavity in directions parallel with the plane of the planar circuit substrate when supported by the support portion; electrically conductive fixing members arranged to both fix resiliently the planar circuit substrate in the housing and electrically connect the planar circuit of the planar circuit substrate to the housing; and separation walls between one of the cavities and concave portions within the housing part having said one of the cavities, said concave portions containing further conducting members for electrically connecting the planar circuit to the housing; and wherein: the lower housing part comprises an integral cooling stage for improving thermal conduction; and the contacting surfaces of said two housing parts (650, 642) have a stepped profile when viewed in cross-section in a plane perpendicular to the planar circuit substrate when supported by the support portion, the stepped profile preventing penetration of electromagnetic waves into the housing. the lower housing part comprises an integral cooling stage for improving thermal conduction; and the contacting surfaces of said two housing parts (650, 642) have a stepped profile when viewed in cross-section in a plane perpendicular to the planar circuit substrate when supported by the support portion, the stepped profile preventing penetration of electromagnetic waves into the housing.