Oludotun Olukoya | University of Westminster (original) (raw)

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Papers by Oludotun Olukoya

2016 Asia-Pacific Microwave Conference (APMC), 2016

2018 41st International Conference on Telecommunications and Signal Processing (TSP), 2018

This paper presents a highly efficient balanced power amplifier for 4G applications using a micro... more This paper presents a highly efficient balanced power amplifier for 4G applications using a microstrip branch line coupler. A compact U-shaped microstrip branch line coupler is used for the balanced power amplifier (PA) architecture. The balanced PA achieves a power aided efficiency (PAE) of 66.8% what makes it very applicable for the 4G and 5G communication systems. The simulated and measured S-parameters (S_11 and S_22), gain, output power and power spectra densities for 3 MHz LTE signals at 1.5 GHz are presented.

In this paper, a waveform comparison and rectifier nonlinearity effects on 4G and 5G wireless sys... more In this paper, a waveform comparison and rectifier nonlinearity effects on 4G and 5G wireless systems are presented. The 3 MHz CP-OFDM and 5G FBMC signals are used in Matlab simulations. It is noted that 3 MHz CP-OFDM signals have larger side-lobes in comparison with 5G FBMC signals. The 5G FBMC signals have stepper slope at the edges and very low out-of-band leakage. The simulated output spectra densities of the rectifier for 3 MHz LTE and 5G FBMC signals at 1.5 GHz are illustrated.

The main focus of this thesis is to investigate the critical nonlinear distortion issues affectin... more The main focus of this thesis is to investigate the critical nonlinear distortion issues affecting RF/Microwave components such as power amplifiers (PA) and develop new and improved solutions that will improve efficiency and linearity of next generation RF/Microwave mobile wireless communication systems. This research involves evaluating the nonlinear distortions in PA for different analog and digital signals which have been a major concern. The second harmonic injection technique is explored and used to effectively suppress nonlinear distortions. This method consists of simultaneously feeding back the second harmonics at the output of the power amplifier (PA) into the input of the PA. Simulated and measured results show improved linearity results. However, for increasing frequency bandwidth, the suppression abilities reduced which is a limitation for 4G LTE and 5G networks that require larger bandwidth (above 5 MHz). This thesis explores creative ways to deal with this major drawba...

2017 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), Jul 1, 2017

This paper presents a compact inkjet printed microstrip Bandstop Filters (BSF) on Flexible Substr... more This paper presents a compact inkjet printed microstrip Bandstop Filters (BSF) on Flexible Substrate. To achieve a compact size, the defected microstrip structure (DMS) structure was employed. A 0.05 mm thick kapton polymide substrate with a dielectric constant of 3.4 suitable for inkjet printing was used. Simulated results show a narrowband response with good stopband attenuation of -39 dB, excellent passband return loss of -0.14 dB and inter-band return loss greater than -35 dB up to 10 GHz. Whilst sustaining its outstanding performance, miniaturisation is also achieved as the presented BSF occupies the least normalised area (0.267 λg × 0.002 λg) when compared to other published filters. A spurline DMS is also simulated and presented, and exhibits improved stopband attenuation up to -45 dB, compact size and excellent passband return loss of -0.09 dB at resonant frequency of 3.425 GHz. These types of filters are very useful for wireless systems such as the WLAN, WiMax and 4G.

In this paper, we evaluate the waveform candidates for 5G wireless communications such as FBMC an... more In this paper, we evaluate the waveform candidates for 5G wireless communications such as FBMC and UFMC and 4G’s cyclic prefix CP-OFDM. Measured results for 1.4 MHz and 3 MHz waveforms show a 5 dB reduction in ACPR between FBMC and UFMC. Simulation and measured output power spectra of the power amplifier for 3 MHz and 10 MHz waveforms are match very well.

In this paper, an evaluation of impact of 5 MHz 5G FBMC waveforms on energy harvesting rectifier ... more In this paper, an evaluation of impact of 5 MHz 5G FBMC waveforms on energy harvesting rectifier performance is presented. The 5 MHz 5G FBMC signals are used in Matlab. The simulated CCDFs of the rectifier for 5 MHz 5G signals at different input powers at 1.5 GHz are illustrated

2018 IEEE Wireless Power Transfer Conference (WPTC)

This paper presents a method for enhancing RFdc conversion efficiency of the rectifier based on i... more This paper presents a method for enhancing RFdc conversion efficiency of the rectifier based on inkjet-printed quadrature based hybrid coupler (QHC) for wireless energy transfer systems. The input matching network and output load of the rectifier are optimized for optimal RF-dc conversion efficiency. Improvement of about 16 dB input power range is achieved for RF-dc conversion efficiency of 60%. The simulated efficiencies of the rectifiers with and without coupler for 3 MHz LTE signals and output power spectra densities at 1.5 GHz are illustrated.

Microwave and Optical Technology Letters, Feb 5, 2018

This paper presents a highly linear balanced power amplifier with miniaturised quadrature hybrid ... more This paper presents a highly linear balanced power amplifier with miniaturised quadrature hybrid coupler for carrier aggregation (CA). The miniaturised quadrature coupler is designed using a novel U-shaped transmission line (USTL) concept to achieve good size reduction. The novel branch-line coupler is used to design a wideband balanced PA. The performance of the balanced PA is compared to a single PA solution. The balanced PA shows better performance with improved matching properties and better electrical stability. There was an increase in saturated maximum output power (Pout) from 8 dBm for the individual PA to 13.41 dBm for the balanced with a power aided efficiency (PAE) of 43.92%. The highly linear balanced PA achieves a 14 dB ACPR reduction and also improves ACPR by 12 dB for non-contiguous and 9 dB for contiguous carrier aggregation.

Microwave and Optical Technology Letters

2016 Asia-Pacific Microwave Conference (APMC), 2016

2018 41st International Conference on Telecommunications and Signal Processing (TSP), 2018

This paper presents a highly efficient balanced power amplifier for 4G applications using a micro... more This paper presents a highly efficient balanced power amplifier for 4G applications using a microstrip branch line coupler. A compact U-shaped microstrip branch line coupler is used for the balanced power amplifier (PA) architecture. The balanced PA achieves a power aided efficiency (PAE) of 66.8% what makes it very applicable for the 4G and 5G communication systems. The simulated and measured S-parameters (S_11 and S_22), gain, output power and power spectra densities for 3 MHz LTE signals at 1.5 GHz are presented.

In this paper, a waveform comparison and rectifier nonlinearity effects on 4G and 5G wireless sys... more In this paper, a waveform comparison and rectifier nonlinearity effects on 4G and 5G wireless systems are presented. The 3 MHz CP-OFDM and 5G FBMC signals are used in Matlab simulations. It is noted that 3 MHz CP-OFDM signals have larger side-lobes in comparison with 5G FBMC signals. The 5G FBMC signals have stepper slope at the edges and very low out-of-band leakage. The simulated output spectra densities of the rectifier for 3 MHz LTE and 5G FBMC signals at 1.5 GHz are illustrated.

The main focus of this thesis is to investigate the critical nonlinear distortion issues affectin... more The main focus of this thesis is to investigate the critical nonlinear distortion issues affecting RF/Microwave components such as power amplifiers (PA) and develop new and improved solutions that will improve efficiency and linearity of next generation RF/Microwave mobile wireless communication systems. This research involves evaluating the nonlinear distortions in PA for different analog and digital signals which have been a major concern. The second harmonic injection technique is explored and used to effectively suppress nonlinear distortions. This method consists of simultaneously feeding back the second harmonics at the output of the power amplifier (PA) into the input of the PA. Simulated and measured results show improved linearity results. However, for increasing frequency bandwidth, the suppression abilities reduced which is a limitation for 4G LTE and 5G networks that require larger bandwidth (above 5 MHz). This thesis explores creative ways to deal with this major drawba...

2017 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), Jul 1, 2017

This paper presents a compact inkjet printed microstrip Bandstop Filters (BSF) on Flexible Substr... more This paper presents a compact inkjet printed microstrip Bandstop Filters (BSF) on Flexible Substrate. To achieve a compact size, the defected microstrip structure (DMS) structure was employed. A 0.05 mm thick kapton polymide substrate with a dielectric constant of 3.4 suitable for inkjet printing was used. Simulated results show a narrowband response with good stopband attenuation of -39 dB, excellent passband return loss of -0.14 dB and inter-band return loss greater than -35 dB up to 10 GHz. Whilst sustaining its outstanding performance, miniaturisation is also achieved as the presented BSF occupies the least normalised area (0.267 λg × 0.002 λg) when compared to other published filters. A spurline DMS is also simulated and presented, and exhibits improved stopband attenuation up to -45 dB, compact size and excellent passband return loss of -0.09 dB at resonant frequency of 3.425 GHz. These types of filters are very useful for wireless systems such as the WLAN, WiMax and 4G.

In this paper, we evaluate the waveform candidates for 5G wireless communications such as FBMC an... more In this paper, we evaluate the waveform candidates for 5G wireless communications such as FBMC and UFMC and 4G’s cyclic prefix CP-OFDM. Measured results for 1.4 MHz and 3 MHz waveforms show a 5 dB reduction in ACPR between FBMC and UFMC. Simulation and measured output power spectra of the power amplifier for 3 MHz and 10 MHz waveforms are match very well.

In this paper, an evaluation of impact of 5 MHz 5G FBMC waveforms on energy harvesting rectifier ... more In this paper, an evaluation of impact of 5 MHz 5G FBMC waveforms on energy harvesting rectifier performance is presented. The 5 MHz 5G FBMC signals are used in Matlab. The simulated CCDFs of the rectifier for 5 MHz 5G signals at different input powers at 1.5 GHz are illustrated

2018 IEEE Wireless Power Transfer Conference (WPTC)

This paper presents a method for enhancing RFdc conversion efficiency of the rectifier based on i... more This paper presents a method for enhancing RFdc conversion efficiency of the rectifier based on inkjet-printed quadrature based hybrid coupler (QHC) for wireless energy transfer systems. The input matching network and output load of the rectifier are optimized for optimal RF-dc conversion efficiency. Improvement of about 16 dB input power range is achieved for RF-dc conversion efficiency of 60%. The simulated efficiencies of the rectifiers with and without coupler for 3 MHz LTE signals and output power spectra densities at 1.5 GHz are illustrated.

Microwave and Optical Technology Letters, Feb 5, 2018

This paper presents a highly linear balanced power amplifier with miniaturised quadrature hybrid ... more This paper presents a highly linear balanced power amplifier with miniaturised quadrature hybrid coupler for carrier aggregation (CA). The miniaturised quadrature coupler is designed using a novel U-shaped transmission line (USTL) concept to achieve good size reduction. The novel branch-line coupler is used to design a wideband balanced PA. The performance of the balanced PA is compared to a single PA solution. The balanced PA shows better performance with improved matching properties and better electrical stability. There was an increase in saturated maximum output power (Pout) from 8 dBm for the individual PA to 13.41 dBm for the balanced with a power aided efficiency (PAE) of 43.92%. The highly linear balanced PA achieves a 14 dB ACPR reduction and also improves ACPR by 12 dB for non-contiguous and 9 dB for contiguous carrier aggregation.

Microwave and Optical Technology Letters