Future television white space (TVWS) transceivers require frequency agility and adherence to spectral masks. For the 320 MHz wide UHF range for TVWS in the UK, this paper discusses two variations of a design for wideband digital up- and down converters at are capable of sampling at radio frequency. The designs consist of a two stage digital conversion is presented, comprising of a polyphase filter that implicitly performs upsampling and decimation, as well as a filter bank-based multicarrier stage capable of resolving the 8MHz channels of the TVWS band. The up- and down-conversion of 40 such channels is shown to not significantly exceed the cost of converting a single channel. The required spectral mask and the reconstruction error of the overall system can be controlled by the filter design. We demonstrate that even the more costly of the two transceiver designs can be implemented on a Virtex-7 FPGA with sufficient word-length to satisfy the spectral masks.
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