An RFID tag reading system for reading one or more RFID tags, the system comprising at least one RF transmitter and an RF receiver, a plurality of transmit/receive antennas coupled to said RF transmitter and to said RF receiver, to provide spatial transmit/receive signal diversity, and a tag signal decoder coupled to at least said RF receiver, wherein said antennas are spaced apart from one another sufficiently for one said antenna not to be within the near field of another said antenna, wherein said system is configured to perform a tag inventory cycle comprising a plurality of tag read rounds to read said tags, a said tag read round comprising transmission of an RF tag interrogation signals with defined relative phases simultaneously from said plurality of antennas and receiving a signal from one or more of said tags, a said tag read round having a set of time slots during which a said tag is able to transmit tag data including a tag ID for reception by said antenna, and said system is configured to generate an interference between said simultaneously transmitted RF tag interrogation signals with defined relative phases from said plurality of antennas in said system, wherein said interference comprises a constructive interference at a first location of said system and a destructive interference at a second location of said system; to perform, during a said tag inventory cycle, a change in a relative phase of a said RF tag interrogation signal transmitted from one of said antennas with respect to another of said antennas, wherein changing said relative phase dithers said first location of said generated constructive interference and said second location of said generated destructive interference; and to combine received RF signals from said simultaneously transmitting antennas to provide a combined received RF signal, and in that said RF receiver has said combined received RF signal as an input; and in that said at least one RF transmitter is common to said plurality of antennas, and characterised in that the system includes a plurality of phase shifters between said at least one RF transmitter and said plurality of antennas to perform said change in relative phase between said antennas. said system is configured to generate an interference between said simultaneously transmitted RF tag interrogation signals with defined relative phases from said plurality of antennas in said system, wherein said interference comprises a constructive interference at a first location of said system and a destructive interference at a second location of said system; to perform, during a said tag inventory cycle, a change in a relative phase of a said RF tag interrogation signal transmitted from one of said antennas with respect to another of said antennas, wherein changing said relative phase dithers said first location of said generated constructive interference and said second location of said generated destructive interference; and to combine received RF signals from said simultaneously transmitting antennas to provide a combined received RF signal, and in that said RF receiver has said combined received RF signal as an input; and in that said at least one RF transmitter is common to said plurality of antennas, and characterised in that the system includes a plurality of phase shifters between said at least one RF transmitter and said plurality of antennas to perform said change in relative phase between said antennas. to generate an interference between said simultaneously transmitted RF tag interrogation signals with defined relative phases from said plurality of antennas in said system, wherein said interference comprises a constructive interference at a first location of said system and a destructive interference at a second location of said system; to perform, during a said tag inventory cycle, a change in a relative phase of a said RF tag interrogation signal transmitted from one of said antennas with respect to another of said antennas, wherein changing said relative phase dithers said first location of said generated constructive interference and said second location of said generated destructive interference; and to combine received RF signals from said simultaneously transmitting antennas to provide a combined received RF signal, and in that said RF receiver has said combined received RF signal as an input; and in that said at least one RF transmitter is common to said plurality of antennas, and the system includes a plurality of phase shifters between said at least one RF transmitter and said plurality of antennas to perform said change in relative phase between said antennas.