Since most restrictions and/or monitoring of mobile device usage within a vehicle are targeted at mobile devices within the driver's space of the vehicle, it is still necessary to be able to distinguish when the mobile devices is being used in the drive or passenger seat with the present system. For example, if the mobile device is in the passenger seat, the system will still detect transmissions from such devices in the uplinks bands, and the system will still be able to determine that the signal is coming from within the vehicle and not from a source outside of the vehicle. However, to distinguish signals coming from the driver's space and the passenger's space, the present system preferably uses the concept of an “antenna sandwich” 700, 750, as shown in FIG. 7. This is a device with two (either directional or omnidirectional) antennas 702, 752 placed on either side of a microwave reflective or microwave absorptive material 704, 754. This effectively restricts each antenna to pick up only signals from opposite hemispheres, where the sphere is split along the plane of the absorptive/reflective material. Transmissions from near the meeting of the two hemispheres will be received roughly equally. Maximum differentiation will occur along the axis perpendicular to the absorptive/reflective material. To increase the differentiation between the two hemispheres even further, the RF reflecting material is preferably parabolic, as shown by antenna sandwich 700, in contrast with the straight design of antenna sandwich 750. The orientation of the antenna sandwich is preferably selected during installation so as to maximize differentiation of the desired RF sources on either side of the absorptive material 704, 754. For differentiating between signals coming from driver versus passenger seats, the antenna sandwich is preferably placed between the driver and passenger, oriented such that the perpendicular axis passes through the centers of the driver and passenger spaces.
