Limits...
A novel sample based quadrature phase shift keying demodulator.

Mohamed Moubark A, Ali SH - ScientificWorldJournal (2014)

Bottom Line: A software simulation of the proposed design was successfully carried out using MATLAB Simulink software platform.In the conventional system, at least 10 dB signal to noise ratio (SNR) is required to achieve the bit error rate (BER) of 10(-6), whereas, in the proposed technique, the same BER value can be achieved with only 5 dB SNR.Since some of the power consuming elements such as voltage control oscillator (VCO), mixer, and low pass filter (LPF) are no longer needed, the proposed QPSK demodulator will consume almost 68.8% to 99.6% less operational power compared to conventional QPSK demodulator.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical, Electronic and Systems Engineering, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia.

ABSTRACT
This paper presents a new practical QPSK receiver that uses digitized samples of incoming QPSK analog signal to determine the phase of the QPSK symbol. The proposed technique is more robust to phase noise and consumes up to 89.6% less power for signal detection in demodulation operation. On the contrary, the conventional QPSK demodulation process where it uses coherent detection technique requires the exact incoming signal frequency; thus, any variation in the frequency of the local oscillator or incoming signal will cause phase noise. A software simulation of the proposed design was successfully carried out using MATLAB Simulink software platform. In the conventional system, at least 10 dB signal to noise ratio (SNR) is required to achieve the bit error rate (BER) of 10(-6), whereas, in the proposed technique, the same BER value can be achieved with only 5 dB SNR. Since some of the power consuming elements such as voltage control oscillator (VCO), mixer, and low pass filter (LPF) are no longer needed, the proposed QPSK demodulator will consume almost 68.8% to 99.6% less operational power compared to conventional QPSK demodulator.

Show MeSH
(a) Output from mixer of QPSK and sine carrier, (b) filtered I-channel signal with LPF, and (c) showing the mismatch in time domain between even and odd data due to phase error in sine carrier.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4150515&req=5

fig7: (a) Output from mixer of QPSK and sine carrier, (b) filtered I-channel signal with LPF, and (c) showing the mismatch in time domain between even and odd data due to phase error in sine carrier.

Mentions: It can be seen that, by mixing the QPSK signal with the sine carrier as shown in (9), it produces two different terms. First, a sine signal with twice the frequency, phase shifted and half amplitude from the incoming signal. Second, another sine signal which varies according to the phase error and half the input amplitude signal. The first signal will be superimposed on second signal which acts like dc offset signal. By using an LPF after the mixing process, the first high frequency term, 2ωc, can be filtered out and the remaining term given in the expression will cause the odd data to be shifted in time domain by Δt. Figure 7 shows output from mixing the QPSK and sine carrier, filtered I-channel signal with LPF, and odd and even data obtained from I channel and Q-channel. The steps involved in obtaining the even data are not shown here but they are the same as in (9). The only difference is the sine carrier substituted by cosine carrier without any phase error:(9)2EsTcos⁡⁡(ωct+θ)×2 sin⁡(ωct+β) =2EsT[ej(ωct+θ)+e−j(ωct+θ)2×ej(ωct+β)−e−j(ωct+β)2j] =4EsT[  sin⁡(2ωct+θ+β)2−  sin⁡(θ−β)2].


A novel sample based quadrature phase shift keying demodulator.

Mohamed Moubark A, Ali SH - ScientificWorldJournal (2014)

(a) Output from mixer of QPSK and sine carrier, (b) filtered I-channel signal with LPF, and (c) showing the mismatch in time domain between even and odd data due to phase error in sine carrier.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4150515&req=5

fig7: (a) Output from mixer of QPSK and sine carrier, (b) filtered I-channel signal with LPF, and (c) showing the mismatch in time domain between even and odd data due to phase error in sine carrier.
Mentions: It can be seen that, by mixing the QPSK signal with the sine carrier as shown in (9), it produces two different terms. First, a sine signal with twice the frequency, phase shifted and half amplitude from the incoming signal. Second, another sine signal which varies according to the phase error and half the input amplitude signal. The first signal will be superimposed on second signal which acts like dc offset signal. By using an LPF after the mixing process, the first high frequency term, 2ωc, can be filtered out and the remaining term given in the expression will cause the odd data to be shifted in time domain by Δt. Figure 7 shows output from mixing the QPSK and sine carrier, filtered I-channel signal with LPF, and odd and even data obtained from I channel and Q-channel. The steps involved in obtaining the even data are not shown here but they are the same as in (9). The only difference is the sine carrier substituted by cosine carrier without any phase error:(9)2EsTcos⁡⁡(ωct+θ)×2 sin⁡(ωct+β) =2EsT[ej(ωct+θ)+e−j(ωct+θ)2×ej(ωct+β)−e−j(ωct+β)2j] =4EsT[  sin⁡(2ωct+θ+β)2−  sin⁡(θ−β)2].

Bottom Line: A software simulation of the proposed design was successfully carried out using MATLAB Simulink software platform.In the conventional system, at least 10 dB signal to noise ratio (SNR) is required to achieve the bit error rate (BER) of 10(-6), whereas, in the proposed technique, the same BER value can be achieved with only 5 dB SNR.Since some of the power consuming elements such as voltage control oscillator (VCO), mixer, and low pass filter (LPF) are no longer needed, the proposed QPSK demodulator will consume almost 68.8% to 99.6% less operational power compared to conventional QPSK demodulator.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical, Electronic and Systems Engineering, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia.

ABSTRACT
This paper presents a new practical QPSK receiver that uses digitized samples of incoming QPSK analog signal to determine the phase of the QPSK symbol. The proposed technique is more robust to phase noise and consumes up to 89.6% less power for signal detection in demodulation operation. On the contrary, the conventional QPSK demodulation process where it uses coherent detection technique requires the exact incoming signal frequency; thus, any variation in the frequency of the local oscillator or incoming signal will cause phase noise. A software simulation of the proposed design was successfully carried out using MATLAB Simulink software platform. In the conventional system, at least 10 dB signal to noise ratio (SNR) is required to achieve the bit error rate (BER) of 10(-6), whereas, in the proposed technique, the same BER value can be achieved with only 5 dB SNR. Since some of the power consuming elements such as voltage control oscillator (VCO), mixer, and low pass filter (LPF) are no longer needed, the proposed QPSK demodulator will consume almost 68.8% to 99.6% less operational power compared to conventional QPSK demodulator.

Show MeSH