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Published in Lal Chand Godara, Handbook of Antennas in Wireless Communications, 2018
Pilot signal is the name given to a signal intended to facilitate the coherent detection of waveforms. Pilot signals can be implemented in the frequency domain as in-band tones [40], or in the time domain as digital sequences that can also provide information about the channel state and thus improve performance in fading conditions [41].
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Published in Jerry D. Gibson, Mobile Communications Handbook, 2017
Pilot signal is the name given to a signal intended to facilitate the coherent detection of waveforms. Pilot signals can be implemented in the frequency domain as an in-band tone [40], or in the time domain as a pilot sequence, which can also provide information about the channel state and thus improve performance in fading [41].
Realization of New Radio 5G-IoT Connectivity Using mmWave-Massive MIMO Technology
Published in Parag Chatterjee, Robin Singh Bhadoria, Yadunath Pathak, 5G and Beyond, 2022
Priyanka Pateriya, Rakesh Singhai, Piyush Shukla, Jyoti Singhai
This estimation method sends the trained/pilot signal prior to data transmission at the transmitter end. The pilot signal is the reference signal utilized by the transmitted and received end of the communications system. The receiver utilizes these trained sequences to evaluate the channel parameters and reduce the channel effects. Uplink pilots are orthogonal from one end of the terminal to the other. In each cell, the maximum number of different orthogonal pilot sequences that can be allotted to UT is expressed as: Pilotsmax=Coherenceinterval/Channeldelayspread Errors occur because the noise in the channel is reduced, utilizing the MMSE at the receiver. The transmitted symbol corresponding to the respective UT is multiplied with the channel matrix, and the AWGN signal is added to the resulting channel, thus corresponding to the receiving signal y, which is utilized to evaluate the channel parameters derived from the pilot sequences. The MMSE estimator neutralizes interferences by selecting an appropriate weight w, which can be calculated as: w=σ2n.σ2s.I+HH−1H whereσ2n is the variance of the noise signal,σ2s is the variance of the transmitted signal, andI is the Nr× Nr size identity matrix.
Efficient microwave power transfer system using retrodirective antenna array
Published in International Journal of Electronics, 2023
Changyoung An, Heung-Gyoon Ryu
Figure 1 shows the system model of RDA-based MPT system. Looking at the operation principle of the RDA-based MPT system in detail, first, the pilot signal corresponding to the target frequency is generated in the power receiver. The generated signal is amplified as necessary. This signal is then transmitted through the antenna. In this case, since the antenna for transmitting the pilot signal cannot know the position of the power transmitter, it is effective to use the antenna having a wide beam width. When the pilot signal is received by the pilot receiving antenna of the power transmitter, the signal received by each antenna is inverted through the phase conjugation circuit. For example, when pilot signals are received through four antennas, if the signals received from antennas 1 to 4 are sequentially delayed by 10 degrees, the phase of each signal is 0, 10, 20, and 30 degrees, respectively. When these pilot signals pass through the phase conjugation circuit, they are converted to 0, −10, −20, and −30 degrees, respectively. The converted pilot signals are then amplified by the multistage amplifier. The amplified power signals are transmitted through each antenna module. Since the signal applied to each transmitting antenna has a phase delay, beamforming is performed in the direction in which the pilot signal is received. Then, the power receiver receives the power signal through the multiple antennas. In a power receiver, it is effective to use multiple antennas to receive more power signals. The power signal received by each antenna is applied to the RF-DC rectifier via an impedance matching circuit. In the RF-DC rectifier, the received RF signal is converted into DC power. The DC power signals converted by each RF-DC rectifier are combined into one and input to the DC power management network module for effective power management. The module converts low input voltages to voltage levels that can be effectively used by various applications and stores them.