Comments on: Need for I-Q modulator and demodulator http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/ Signal Processing for Communication Fri, 10 Feb 2012 01:03:15 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Thulasi http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-100840 Thulasi Tue, 07 Feb 2012 17:56:02 +0000 http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-100840 written in simple way.. easy to understand:) it helps a lot.. thank you:) written in simple way.. easy to understand:) it helps a lot.. thank you:)

]]> By: Krishna Sankar http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-56230 Krishna Sankar Tue, 24 May 2011 00:45:00 +0000 http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-56230 @tabraiz: idling... try to come back to posting :) @tabraiz: idling… try to come back to posting :)

]]> By: tabraiz http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-50427 tabraiz Sun, 13 Mar 2011 23:48:42 +0000 http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-50427 What are you doing these days What are you doing these days

]]> By: Krishna Sankar http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-39889 Krishna Sankar Sun, 14 Nov 2010 21:12:13 +0000 http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-39889 @komal: a) Source coding : If we have redundancy in the information symbol, we can have a better way of sending that information out (rather than sending the raw data). For eg, if we have a sequence [0 0 0 0 0 1 1 1 ], we can alternatively send [ 4 zeros three ones] :) b) Modulation : We can pack more bits into a symbol. However, the penalty is that we need higher signal to noise ratio to recover the bits. @komal:
a) Source coding : If we have redundancy in the information symbol, we can have a better way of sending that information out (rather than sending the raw data). For eg, if we have a sequence [0 0 0 0 0 1 1 1 ], we can alternatively send [ 4 zeros three ones] :)
b) Modulation : We can pack more bits into a symbol. However, the penalty is that we need higher signal to noise ratio to recover the bits.

]]> By: komal http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-39185 komal Wed, 03 Nov 2010 12:25:18 +0000 http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-39185 Hi!. How the source coding can compress the data rate?And how the modulation schemes are able to increase the data rate,though we are representing the symbol with redundant bits?Can u plz put forward the process of digital communication with an example? Hi!. How the source coding can compress the data rate?And how the modulation schemes are able to increase the data rate,though we are representing the symbol with redundant bits?Can u plz put forward the process of digital communication with an example?

]]> By: anil kumar http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-18302 anil kumar Tue, 19 Jan 2010 20:47:49 +0000 http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-18302 Hi evry one in this.Nice to c u all here buddy's. Ofcourse I am new to this. I have a small problem with my calculation in OFDM USING QAM AND IQ modulator . I ll just paste the question here. I have done some calculations, but i was unable to judge those.Please help as early as possible. We are required to build a SIMULINK model of a 16-QAM OFDM Digital Communications System (OFDM transmitter and OFDM receiver) operating over an AWGN channel. • The OFDM system has a cyclic prefix of 20% of the (data) symbol duration Ts. • Use an I-Q modulator at the transmitter and I-Q demodulator at the receiver to upconvert and downconvert, respectively, the analogue signal to a central frequency of fc=2 MHz (so, the passband transmitted signal is centered on 2 MHz). • The symbol duration is set to Ts =1 msec. • Chose the number of carriers, N, so as to achieve a bitrate of Rb = 192000 bits / sec (you have to evaluate the correct N). • Test the system performance for Eb/N0=5, 8, 10, 12 and 14 dB, and report the respective BER measurements. • Subsequently, use a channel encoder of your choice and repeat the BER measurements for the same values of Eb/N0. Hi evry one in this.Nice to c u all here buddy’s.
Ofcourse I am new to this. I have a small problem with my calculation in OFDM USING QAM AND IQ modulator .
I ll just paste the question here. I have done some calculations, but i was unable to judge those.Please help as early as possible.

We are required to build a SIMULINK model of a 16-QAM OFDM Digital Communications System (OFDM transmitter and OFDM receiver) operating over an AWGN channel.
• The OFDM system has a cyclic prefix of 20% of the (data) symbol duration Ts.
• Use an I-Q modulator at the transmitter and I-Q demodulator at the receiver to upconvert and downconvert, respectively, the analogue signal to a central frequency of fc=2 MHz (so, the passband transmitted signal is centered on 2 MHz).
• The symbol duration is set to Ts =1 msec.
• Chose the number of carriers, N, so as to achieve a bitrate of Rb = 192000 bits / sec (you have to evaluate the correct N).
• Test the system performance for Eb/N0=5, 8, 10, 12 and 14 dB, and report the respective BER measurements.
• Subsequently, use a channel encoder of your choice and repeat the BER measurements for the same values of Eb/N0.

]]> By: Krishna Sankar http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-16636 Krishna Sankar Sun, 06 Dec 2009 11:25:51 +0000 http://www.dsplog.com/2008/04/05/need-for-i-q-modulator-and-demodulator/#comment-16636 @kwame: Well, its not that we were not utilizing the other half of the spectrum. Rather the same information (mirrored in frequency) was present in the other half of the spectrum. In previous case, we were not sending anything on the Q arm. @kwame: Well, its not that we were not utilizing the other half of the spectrum. Rather the same information (mirrored in frequency) was present in the other half of the spectrum. In previous case, we were not sending anything on the Q arm.

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