Hi Alphonso,
I implemented a transmitter for the DRM(30) standard in GNU Radio and
published it on github (https://github.com/kit-cel/gr-drm).
To (partly) answer your questions:
1) DRM only accepts specific audio sample rates, make sure to read the
standard documents carefully.
2) Mixing is usually done by the USRP. You as the user only deal with
the complex baseband centered around DC. 12 kHz would also be a VERY low
carrier frequency, short-wave radio usually uses frequencies between 3
and 30 MHz.
--Felix
On 03.06.2015 12:57, [email protected] wrote:
hello,
i'm trying to implement an ofdm transmitter (and afterwards a
receiver) for demonstration. the parameters should match the drm
standard. so my first try was to implement the transmitter with the
following main parameters:
ofdm transmitter block
fft length = 256 (--> fft length >= occupied carriers)
cyclic prefix = 64 (--> 256/4)
occupied carriers = 228 (--> (-114, -113, ..., 113, 114))
for this try no pilot carriers and symbols and no sync words.
everything works fine but there is a problem with the spectrum of this
ofdm signal. from older posts i have the following equation to set the
bandwidth (bw) of my ofdm output signal:
bw = sampling_rate * occupied_carriers / fft_length
with the parameters above and the wish of a bandwidth of 10khz (to
match the drm standard) i will get the following sampling rate:
sampling_rate = bw * fft_length / occupied_carriers = 10khz * 256 /
228 = 11.228khz
now i have two questions:
1) if there is an input source with a sampling rate higher than
11.228khz (maybe from my sound card (44.1khz) or a wav file (48 khz))
should i use a resampler block because there is a problem with
nyquist? how can i handle this problem?
2) the same problem goes with the output. if i mix up the ofdm signal
to a carrier frequency (for example 12khz) how can i handle this?
there is also a problem with nyquist.
thanks in advance!
alphonso
--
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)
Felix Wunsch, M. Sc.
Research Associate
Kaiserstraße 12
Building 05.01
76131 Karlsruhe
Phone: +49 721 608-46276
Fax: +49 721 608-46071
E-Mail: [email protected]
www.cel.kit.edu
KIT -- University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association
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