Integrated Filters and Couplers for Next Generation Wireless Tranceivers

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 drawback. The injection technique was modified with the aid of a well-designed band-stop filter. The compact narrowband notch filter designed was able to suppress nonlinear distortions very effectively when used before the PA. The notch filter is also integrated in the injection technique for LTE carrier aggregation (CA) with multiple carriers and significant improvement in nonlinear distortion performance was observed. This thesis also considers maximizing efficiency alongside with improved linearity performance. To improve on the efficiency performance of the PA, the balanced PA configuration was investigated. However, another major challenge was that the couplers used in this configuration are very large in size at the desired operating frequency. In this thesis, this problem was solved by designing a compact branch line coupler. The novel coupler was simulated, fabricated and measured with performance comparable to its conventional equivalent and the coupler achieved substantial size reduction over others. The coupler is implemented in the balanced PA configuration giving improved input and output matching abilities. The proposed balanced PA is also implemented in 4G LTE and 5G wireless transmitters. This thesis provides simulation and measured results for all balanced PA cases with substantial efficiency and linearity improvements observed even for higher bandwidths (above 5 MHz). Additionally, the coupler is successfully integrated with rectifiers for improved energy harvesting performance and gave improved RF-dc conversion efficienc

Inkjet-Printed Bandstop Filters for Interference Suppression in Multi-Standard Wireless Systems

This paper presents a highly compact inkjet printed microstrip bandstop filter (BSF) for interference suppression in multi-standard wireless applications. The structure is designed with strict specifications for inkjet printing such as the use of the Kapton substrate and its flexible polyimide film. The design was simulated based on Kapton substrate with a thickness of 50µm and dielectric constant of 3.4. The simulated results show a good narrowband response with good stopband attenuation of about 38 dB. When compared to other published BSFs, the proposed structure occupies the least normalized area and best return loss performance up to 10 GHz. This filter is then used to reject interference in a multi-standard wireless transmitter system with suppression of about 30 dB achieved with a great level of noise and spurious response reduction thereby improving the overall performance of the system. This type of filter will be very useful to eliminate undesired signals in next generation 4G LTE-Advanced and 5G mobile networks as well as being very attractive for modern day multi-standard wireless applications such as machine to machine (M2M) communications and internet of things (IoT)

Evaluation of Waveform Candidates for 5G Wireless Communications

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

Rectifier Nonlinearity Effects on 4G and 5G Wireless Systems

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

Highly Efficient Balanced Power Amplifiers for 4G Applications

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 (S11 and S22), gain, output power and power spectra densities for 3 MHz LTEsignals at 1.5 GHz are presented

Impact of 5G Waveforms on Energy Harvesting Rectifier Performance

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

Rectifiers Based on Quadrature Hybrid Coupler with Improved Performance for Energy Harvesting

This paper presents a method for enhancing RF-dc 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

Miniaturised Inkjet-printed Quadrature Hybrid Couplers for Multiband Wireless Systems

A miniaturised multiband inkjet printed Quadrature Hybrid Coupler is proposed in this paper. The design and flexibility characterization of an inkjet-printed coupler on a flexible 50 μm polyimide film (Kapton) substrate is presented. Kapton is chosen due to its good balance of physical, chemical and electrical properties with a low loss factor of 0.0021. The coupler is designed to operate at 1.5 GHz, 4.5 GHz, 6.0 GHz, 7.5 GHz and 9.0 GHz. The circuit was simulated and the simulation results are presented. The coupler will be fabricated and test results will be presented. The proposed QHC size is 78% smaller than the conventional QHC

Miniaturized Quadrature Hybrid Couplers based on Novel U-shaped Transmission Lines

In this paper, a miniaturized microstrip quadrature hybrid coupler (QHC) using U-shaped transmission lines (USTLs) is presented. The proposed approach replaces all arms of the conventional QHC with its equivalent USTL to achieve compactness. The proposed coupler structure is designed to operate in the 1.5 GHz (1427-1518 [MHz]) band which is one of the 5G bands of interest. At such low RF/microwave bands below 3-4 GHz, the size of the conventional coupler is considerably very large which raises a concern for the next generation networks. The pro- posed coupler is designed, simulated and fabricated using Rogers 5880 with thickness of 0.79 mm, dielectric con- stant (εr) of 2.2 and loss tangent of 0.0021. The proposed QHC size is 70% smaller in circuit area (30% relative area) than the conventional equivalent. Simulation and mea- sured results are presented and good matching between the results is observed, confirming the outstanding coupler performance properties. The proposed miniaturized QHC structure will play a vital role for next generation 4G and 5G wireless communication systems operating below 6 GHz