Digital Up Converters (DUC) and Digital Down Converters (DDC) are widely used in communication systems for scaling the sample rate of signals. Digital up conversion is required when a signal is translated from baseband to intermediate frequency (IF) band. Digital down conversion happens when a signal is converted from intermediate frequency band to baseband. DUCs and DDCs typically include frequency shifting using mixers, in addition to sampling rate conversion. The structure of a DUC or DDC depends mainly on the conversion ratio that is required. For example, WiMAX (Worldwide Interoperability for Microwave Access) systems have a conversion ratio typically in the order of 8 to 10. For such low conversion rates, the DUC or the DDC is constructed using FIR filters only. If the required conversion ratio is much higher, a cascaded integrator-comb (CIC) filter is used in the DDC/DUC structure.
Lattice's Multi-Channel (MC) DUC/DDC reference design is broadly applicable to various 4G standards such as LTE and Wimax. This reference design was specifically tested for a WiMAX configuration.
WiMAX Reference Design
The Multi-Channel DUC/DDC reference design addresses the 10 MHz bandwidth channels for Wireless-MAN or Wireless-HUMAN PHY for WiMAX systems. An IF sampling frequency of 89.6 MHz is used for this reference design. The MC DDC/DUC is designed to support 4 complex channels (i.e., each channel having an I and a Q component). The MC DUC and MC DDC reference design packages include pre-configured Lattice ispLeverCore Intellectual Property Cores (IPs) for the FIR (Finite Impulse Response) filters, DA-FIR (Distributed Arithmetic Finite Impulse Response) filters and the NCO (Numerically Controlled Oscillator).
The multi-channel reference designs use three ispLeverCORE IP Cores - the Finite Impulse Response (FIR) Filter, the Distributed Arithmetic FIR, and the Numerically Controlled Oscillator (NCO). See additional license requirements below for details.
Additional License Requirements
| IP Core |
Multi-Channel DDC/DUC |
| Distributed Arithmetic FIR (DA-FIR) Filter |
Yes |
| Finite Impulse Response (FIR) Filter |
Yes |
| Numerically Controlled Oscillator (NCO) |
Yes |
NOTE: The DA-FIR, FIR and NCO IP cores must first be installed using IPexpress to implement these reference designs, but no manual configuration is necessary. The DDC and DUC reference designs will configure the IP cores as needed.
The IP cores provide a free FPGA evaluation period which also applies to the reference design. Please see the User Guide for more details about the use of these cores in this reference design.
For licenses and support, please contact your local Lattice sales office.