# Forum: FPGA, VHDL & Verilog Digital to analog converter DAC and FPGA

 Author: issam sassi (Company: uqtr) (isamel85) Posted on: 2014-11-12 17:21

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Hello,

Actually I am looking for a digital to analog converter (preferably an
evaluation board) in order to connect an FPGA with a RF signal generator
N9310A (he plays the role of an I and Q modulator and includes two
inputs analog I and Q on rear panel and he can transpose the two analog
signals to an RF signal).

In the FPGA, I have a baseband transmitter chain with two I and Q
outputs, the internal blocks are clocked on the clock frequency of 1
MHz, but the last two blocks (upsampling with a factor of 8 and the
digital filter in transmission) working on an 8 MHz clock. So the two
outputs of filters with 10 bits each (I and Q) are the outputs of the
main transmitter.

So I need an evaluation board for a digital to analog converter which
has the following characteristics:

- 10 bit resolution
- Rate of 8 MSPS. Is it correct? Is it possible to select a higher rate
e.g. 125 MSPS?
- Dual TxDAC for the two channels (I and Q)
- Parallel interface with digital signals from FPGA
- Analog output range or the output reference voltage must be compatible
with analog I and Q inputs of the RF signal generator.

Knowing that the analog I and Q inputs of the RF signal generator has
the following characteristics: I / Q modulation (Option 001 only)

Operating mode                          External I/Q inputs

VSWR                                          < 1.5

Full scale input                            0.5 Vrms

Modulation frequency range    DC to 20 MHz                 At 3 dB
points

Carrier suppression 40 dBc       Typical; modulation frequency = 10 kHz

QPSK EVM        3%            Typical; 1 Msps; 0.22 RRC filter

GMSK phase error    1.2 °rms    Typical; 1 Msps; BT = 0.5

Connector and impedance    BNC female; 50 Ω                  Rear panel

So if anyone who can help me to choose this converter.

Another alternative, is there a VHDL description of a digital to analog
converter based on a first order Sigma Delta modulator (a version that
works)?

Thank you.

Best Regards,
Issam

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