Abul Hasan

Novel Modeling and Calibration Approach for Multiport Receivers Mitigating System Imperfections and Hardware Impairments

Factors limiting and degrading the performance of a multiport-based receiver system for wideband signals are modeled and a suitable calibration approach is proposed in this paper. The proposed calibration approach uses a new model for linearization of diode power detectors suitable for wideband real (modulated) wireless signals. To verify the proposed model and calibration procedure, a 2-18-GHz wideband six-port-based receiver system is set up and its performance is verified using wireless signals having different bandwidth and modulation schemes. The new calibration algorithm improved the error vector magnitude (EVM) of the receiver system from 7.9% to 1.6% for a 64-QAM signal with a bandwidth of 2 MHz and a data rate of 12 Mb/s. To show the usefulness of the model for real communication signals, wideband code division multiple access (WCDMA) and wireless local area network (WLAN) signals are received and EVM of 4.7% and 3.4% are reported for the WCDMA and the WLAN signals, respectively.

Concurrent Dual-Band Six-Port Receiver for Multi-Standard and Software Defined Radio Applications

This paper proposes a novel concurrent dual-band receiver architecture that uses only one six-port correlator circuit to downconvert two signals in two different bands concurrently. The receiver is reconfigurable over a broadband to simultaneously receive two different signals with different modulation techniques and bandwidths. There are no limitations on the carrier frequencies of the two signals except that they have to be within the bandwidth of the six port receiver. The mathematical model for the receiver is derived and subsequently implemented to evaluate its performance. This approach shows that, by analytically choosing the frequencies of the two local oscillator signals sent into the six-port correlator, the in-phase (I) and the quadrature (Q) components of each of the two input RF signals can be obtained from the filtered high-pass and low-pass components of the diode detectors outputs. A black box model, which uses a modified memory polynomial, is used to calibrate the receiver. The calibration constants are estimated by sending a training signal of similar characteristics as the signal to be received. Two signals pairs with different modulation types are received to verify the model, and to evaluate the performance and test the robustness of the receiver. A 64-QAM signal at 2.5 GHz and a 16-QAM signal at 3.0 GHz, both with a data rate of 2 Mbps are received. The measured EVMs were 1.9% for the 64-QAM and 1.8% for the 16-QAM. Real communication signals, WCDMA and LTE were also received concurrently with measured EVMs of 1.9% and 2.0%, respectively. A bit error rate (BER) profile of the receiver for a 16QAM and 64QAM, both at 2Mbps is also plotted to evaluate the receiver.

A Wideband Balanced-to-Unbalanced Coupled-Line Power Divider

A compact wideband balanced-to-unbalanced (BTU) out-of-phase power divider (PD) is proposed in this letter. This novel circuit essentially consists of three pairs of cascaded coupled lines and a grounded resistor for output isolation. By using the even- (odd-) mode method analysis and the traditional transmission-line theory, closed-form design equations for equal power division with out of phase from one differential input to two unbalanced outputs, high output isolation and good common-mode suppression are obtained, simultaneously. In addition, an experimental PD is designed and fabricated. The good performance and the consistency between the simulated and measured results verify our design theory.

Performance driven six-port receiver and its advantages over low-IF receiver architecture

This paper provides an extensive analysis of the performance of a six-port based direct conversion receiver (SPR) in terms of signal quality, dynamic range, noise figure, ports matching, isolation, bandwidth, and cost. Calibration technique using multimemory polynomials has been adopted in order to improve the signal quality of the six-port receiver. The performances of the calibrated receiver are then compared with the performances of a commercially available I-Q demodulator used as a low-IF receiver. The main advantages and disadvantages of the SPR compared to the low-IF receiver are highlighted. The major advantages of the SPR come in terms of its available input frequency bandwidth and the low power requirement. The SPR system requires no external bias supply but suffers in terms of the available conversion gain. A better port matching of the SPR can be guaranteed over a wide frequency bandwidth, which mixer based receiver systems lack. The main component limiting the performance of a SPR is the diode detector. A faster and a better diode detector will alleviate some of the problems highlighted in this paper. The SPR systemis calibratable and its error-vector-magnitude performance can be made better than the I-Q demodulator used as a low-IF receiver.

Planar Miniaturized Balanced-to-Single-Ended Power Divider Based on Composite Left- and Right-Handed Transmission Lines

A planar asymmetrical miniaturized circuit based on composite left- and right-handed transmission lines (CLRHTLs) is proposed to design a new balanced-to-single-ended (BTSE) power divider (PD) in this letter. The CLRHTLs are used to realize circuit miniaturization and positive-phase response. Conversion between the mixed-mode scattering parameters and the standard scattering parameters, and circuit analytical methods are discussed to realize the equal power division in phase from one differential input to two SE outputs. To verify the correctness of the proposed theory, a practical BTSE PD, which operates at 0.95 GHz, is designed and fabricated. The measured relative bandwidth is 26.3%, and the final circuit size is only

Novel Planar Compact Coupled-Line Single-Ended-to-Balanced Power Divider

0.021~\lambda _{g}^{2}

Novel Calibration Algorithm of Multiport Wideband Receivers Based on Real-Valued Time-Delay Neural Networks

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Effort-Reduced Calibration of Six-Port Based Receivers for CR/SDR Applications

In this paper, a novel planar compact coupled-line circuit is proposed to design a single-ended-to-balanced power divider (PD) that can be used in numerous balanced circuits and systems. By using the matrix transformation between the mixed-mode (MM) scattering parameters and the single-ended scattering parameters, the constraint rules are deduced to realize the performance of equal power division with in-phase, good input (output) port matching, high isolation between two balanced outputs, high suppression of the common-mode (CM) noise, as well as the mode-conversion suppression between differential-mode signals and CM noise. Then, the closed-form design equations are derived using the even- and odd-mode analysis. Finally, a microstrip PD, which works at 1 GHz, is designed and fabricated. The measured (simulated) operating relative bandwidth is 37% (38%) from 0.76 (0.83 GHz) to 1.13 GHz (1.21 GHz). The consistency between the simulated and measured MM scattering parameters verifies the correctness of the design theory.

Design and Calibration of Wideband Multiport Homodyne Wireless Receivers

In this paper, a novel calibration algorithm based on real-valued time-delay neural network (RVTDNN) is proposed for the multiport receiver to recover I/Q signals from the received modulated signals, especially from wideband signals. All the system impairments, including the nonideal six-port correlator, the nonlinearity of the diodes, and the memory effects under the excitation of the wideband signals, are taken into consideration. The RVTDNN, which has three layers, consists of four inputs and two outputs (in-phase and quadrature signals), and its parameters (biases and weights) are all real-valued and are determined by the backpropagation algorithm. Finally, the proposed calibration method is validated by a 2-18-GHz six-port receiver under 3G and 4G signals. The performance of the error vector magnitude between the transmitted signals and received signals is always less than 1.8%, which validates the correctness of the proposed model.

Six-port technology for MIMO and cognitive radio receiver applications

This paper presents an effort-reduced approach for calibrating the reconfigurable six-port based receiver (SPR) systems for cognitive radio/software defined radio applications that accounts for all the known imperfections and impairments of an SPR system. The state-of-the-art calibration method requires estimation of more than 100 calibration parameters on-the-fly. The proposed calibration method reduces the number of parameters to four without any sacrifice in the overall system performance. The proposed method uses a different structure for six-port junction to ease the calibration effort. The nonlinearity and the frequency response of the system are broken down into two different realms. Nonlinearity of the system is accounted for by continuous wave characterization of the diode detectors while the frequency response is compensated for using an equalizer in the calibration step. The results obtained for the proposed approach are compared with the state-of-the-art calibration method. Similar performance from the SPR system is obtained with much reduced calibration complexity.