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A novel and compact microstrip ultra-wideband (UWB) bandpass filter (BPF) based on a triple-mode resonator is designed, fabricated and measured. The proposed resonator is composed of a coupled line with a half-pass characteristic, which is connected directly with each other at one end and is short-circuited to the grounding plane at the other end. A simple structure and design approach to the proposed filter is provided and demonstrated. To implement the design on a microstrip, the directly tapped-transition input/output ports are used to excite the coupled-line multi-mode resonator. The measured results are in good agreement with the electromagnetic simulated results. The proposed filter shows a 3 dB fractional bandwidth of 117.3% at the central frequency (/)) with a return loss of better than 12 dB and an insertion loss of < 0.5 dB within the passband response. [PUBLICATION ABSTRACT]

Over the past decade, avalanche photodiodes (APDs) have been widely investigated for visible light communications. However, the gain and collection area of an APD is limited, which prevents this type of detector from improving its sensitivity. The gain is typically limited by excess noise, and its overall capacitance limits the collection area. Typically, the APDs of less than a square millimetre only have a bandwidth of more than 100 MHz. The excess noise factor can be avoided by biasing an APD above its breakdown voltage, significantly increasing its gain. The high gain makes an APD sensitive enough to detect photons down to a single photon, hence referred to as a single-photon avalanche diode (SPAD). Similarly, the collection area can be increased using a large array of SPAD elements. However, several important parameters are associated with the size of the array and a SPAD element, such as the effective recovery time, output pulse width or bandwidth, and linearity, which significantly impact the sensitivity and achievable data rate. In this thesis, two off-the-shelf SiPMs are investigated as an OOK VLC receiver for indoor visible light communication and to study the impact of their various parameters on performance. For this reason, parameters such as bias-dependent dark count rate and photon detection efficiency at a particular wavelength, average standard output, optimum bias voltage, and dynamic range of selected SiPMs are characterised. Moreover, analytical models of these parameters are presented. These analytical models are then used to predict the performance of a SiPM-based VLC receiver. The performance of selected SiPMs is first evaluated in the dark without equalisation, where the impact of the bandwidth on the required power penalty due to intersymbol interference (ISI) is studied. The measured power penalty is then analysed by comparing it to the power penalty of a first-order low-pass system and a power penalty estimated based on the collection area, PDE, and the required average number of photons per bit. Subsequently, the performance is evaluated with equalisation, and the sensitivity ratio between selected SiPMs is compared to study the impact of the collection area and the non-linearity of SiPMs. The results obtained in the dark show that when equalsation is used, the SiPM with a larger collection area is approximately 4 times more sensitive than the SiPM with a smaller collection. Similarly, to evaluate the performance of SiPMs in the presence of ambient light, the impact of warm white LED with various absorption filters and combinations of absorption filters has been studied through various models. The performance of SiPMs is then evaluated in 500 lux of illuminance with a particular combination of absorption filters, selected based on transmittance at a wavelength equal to 405 nm and the ability to reject the ambient light from a warm white LED. The sensitivity ratio between selected SiPMs is then studied to see the impact of ambient light. The results in the ambient light show that when used with equalisation, due to the impact of ambient light, the sensitivity ratio is reduced to 2.5. However, despite the large SiPM being more susceptible to ambient light, the SiPM is still more sensitive than the small SiPM up to 1.2 Gbps. However, the limited bandwidth and non-linearity of the large SiPM mean that its sensitivity is limited at higher data rates.

The outphasing technique proposed by Chireix in 1935 is one of the classical methods of addressing power amplifier (PA) efficiency degradation caused by operating in output back-off (OBO) conditions, where PA efficiency is typically low. Essentially, the envelope from the input signal is eliminated, and two CW signals are constructed; these have constant amplitude, while their relative phase offset holds the original information contained by amplitude modulation. Consequently, efficiency improvements are achieved by amplifying signals with constant amplitude using PAs operating in saturation, where efficiency typically peaks. The envelope is restored at the output by means of a vector summation of both signals, using a non-isolating combiner at the output stage The main focus of the work described in this thesis was placed on extending bandwidth of the inherently narrowband technique of outphasing and then adopting this method to modern telecommunication standards. Two prototype PAs were designed to investigate whether bandwidth improvements can be achieved by adopting a broadband balun as a combining structure in the outphasing PA. Two baluns were designed and fabricated to be used in the demonstrator circuits; one using a section of semirigid coaxial cable and the other, a planar balun realized on 10 mil thick Alumina substrate. A novel method of fabrication was proposed for the former structure, which achieved more than double octave bandwidth, from 1.25 GHz to 4.7 GHz with losses lower than 1dB, an amplitude imbalance (trace separation) below 0.75 dB and phase imbalance within ±5 degrees. The measured CW performance of the prototype circuits produced results comparable with the state-of-the-art solutions available in literature. Moreover, this work demonstrated that a balun with sufficient bandwidth allows load modulation to be prescribed at fundamental and second harmonic frequencies, opening the possibility of waveform engineering to implement continuous PA modes such as class J in outphasing PAs. The desired harmonic load termination was achieved without any specialized matching networks, and solely by means of load modulation provided through active device interaction. The thesis concludes with the formulation, analysis and description of the novel concept derived from Chireix outphasing. Several outdated assumptions still prevalent in outphasing analysis included in literature today are challenged and reformulated for modern semiconductor devices such as GaN HEMTs. Through this process, a new concept of Current Mode Outphasing (CMOP), is proposed and described in detail. One of the significant advantages of the proposed approach is it allows the elimination of the combiner structure, which typically dominates the size of the final outphasing circuit, due to the presence of λ/4 transmission lines. Consequently, the demonstrator MMIC circuit, containing DC bias, stability elements and pre-matched to 50 Ω on input and output, has been deployed on an area of 2.3 mm x 2.8 mm. The CMOP circuit was fabricated using 0.25 µm GaN technology and achieved a bandwidth of 1.6 GHz centered at 3.35 GHz, whereas the maximum CW output power remains within 43 dBm ± 0.5 dB. A total gain of more than 12 dB is reported from 2.95 to 3.95 GHz, while a maximum Power Added Efficiency was measured as 68.5% at 3.25 GHz and remains greater than 60% from 2.85 to 3.8 GHz, and above 50% for almost the entire frequency range. The output back-off (OBO) efficiency peaks at 3.25 GHz with 53.5% and 45.6% for 6 dB and 8 dB back-off, respectively, and remains above 30% and 23.7% for the entire frequency range. To the best of the authors' knowledge, this is the largest fractional bandwidth achieved in an outphasing PA, that has been reported in literature.

A broadband hybrid power amplifier using a gallium nitride (GaN) high electron mobility transistor (HEMT) is presented. A discrete GaN HEMT bare die with 1.25 mm of gate width is used, and a compact size of 8.3 × 12.7 mm is achieved by using a feedback technique based on lumped elements. The power amplifier operates from 100 to 1000 MHz, and shows more than 12.8 dB gain and higher than 30.7 dBm output power in the overall bandwidth. Power added efficiency of 61.3% was acquired at the mid-band frequency and more than 54.5% throughout the bandwidth. [PUBLICATION ABSTRACT]

Background: Prolonged field care is required when casualty evacuation to a surgical facility is delayed by distance or tactical constraints. This can occur in both civilian and military environments, including remote locations in Canada. In these circumstances, there are no established treatment options for extremity compartment syndrome. One solution is to remotely mentor the tactical clinician to perform surgical compartment release. Methods: Six military clinicians were recruited to perform a 2-incision leg fasciotomy on a synthetic model under the remote guidance of an orthopedic surgeon. The operators wore smartglasses that allowed synchronous communication and the display of anatomic holograms in their field of view. Three control legs were created: 1 complete fasciotomy and 2 with major errors. The experimental and control legs were evaluated by 2 blinded surgeons according to criteria described by Kucera and colleagues. Results: All 6 study participants were Canadian Armed Forces physician assistants. They had extensive experience as military clinicians but minimal experience performing surgical procedures. None had performed a fasciotomy previously. The study was conducted over 3 days, during which bandwidth varied widely at the study site: ping ranged from 12 to 338 ms, download speed from 0.93 to 3.48 Mbps and upload speed from 0.44 to 0.64 Mbps. The mentor, located 300 km away from the study site, had a stable Internet connection with sufficient bandwidth. The average duration of the procedure was 53 minutes (standard deviation 12 min). All 6 procedures were completed without major errors: release of all 4 compartments was achieved through fulllength incisions in the skin and fascia. The only minor error was a laceration of the saphenous vein (n = 1). All 3 control specimens were correctly assessed by the evaluators. None of the participants experienced adverse effects from wearing the AR headset. Four dropped calls occurred. In all cases, the connection was reestablished, and the procedure was completed successfully. Conclusion: Despite limited bandwidth, we were able to successfully perform 2-incision leg fasciotomy in all cases. We attribute the dropped calls to a mismatch between the size of the graphic files and the available bandwidth. A better technical understanding of the software by the mentor would have avoided this problem. Important considerations for future research and practice include protocols for dropped communications, communications training for mentoring surgeons and surgical skills training for the operators.

This paper presents an ultra-low-power second-order Chebyshev active-RC complex filter for a low-IF ultra-low-power receiver. By utilising a pole-cancellation push-pull buffer with feedforward phase compensation technology, the operational amplifier (opamp) realises superior stability while maintaining high gain bandwidth and ultra-low power consumption. A second-order complex filter with four proposed opamps and an adaptive bias fabricated in standard 180 nm CMOS process consumes only 460 mu W at 1.8 V power supply. The measured centre frequency is 3 MHz and bandwidth is 2 MHz, while it achieves 32 dB image rejection ratio at the centre frequency.

[...]a reduction of RF power without losing the superior features of a TSE sequence would be advantageous. A big advantage of GRASE compared to TSE is the smaller number of refocusing pulses. [...]SAR can be substantially reduced.

The bandwidth of tapered slot antennas (TSAs) is usually limited by the bandwidth of the feed used and typically does not exceed a few octaves, even though the TSA itself possibly can operate at a wider frequency range. Presented, and discussed, is a planar TSA feeding scheme that makes use of an external 1808 hybrid. Design guidelines and analytical formulas are presented for this hybrid connection scheme.

In the field of electronic information science, with the continuous advancement of signal processing technology, filtering technology has become particularly important due to its ability to effectively suppress noise and extract useful information. This article focuses on exploring an innovative method for rapid optimization of filters. By designing a hollow cylindrical dielectric ceramic and combining it with traditional inductive structures, the bandwidth and return loss characteristics of intelligent filters at various frequencies could be quickly controlled. Simulation results show that by loading the dielectric ceramic, the bandwidth of filter 1 is reduced by an average of 20%, the return loss at low frequencies is increased by an average of 3 dB, and the return loss at high frequencies is reduced by 5 dB. Simulations were conducted on two different structures of filters, and the results showed that the optimization design technique has good applicability.

In current `Cloud' data centres, switching of data between servers is performed using deep hierarchies of interconnected electronic packet switches. Demand for network bandwidth from emerging data centre workloads, combined with the slowing of silicon transistor scaling, is leading to a widening gap between data centre traffic demand and electronically-switched data centre network capacity. All-optical switches could offer a future-proof alternative, with potentially under a third of the power consumption and cost of electronically-switched networks. However, the effective bandwidth of optical switches depends on their overall switching time. This is dominated by the clock and data recovery (CDR) locking time, which takes hundreds of nanoseconds in commercial receivers. Current data centre traffic is dominated by small packets that transmit in tens of nanoseconds, leading to low effective bandwidth, as a high proportion of receiver time is spent performing CDR locking instead of receiving data, removing the benefits of optical switching. High-performance optical switching requires sub-nanosecond CDR locking time to overcome this limitation. This thesis proposes, models, and demonstrates clock synchronisation assisted CDR, which can achieve this. This approach uses clock synchronisation to simplify the complexity of CDR versus previous asynchronous approaches. An analytical model of the technique is first derived that establishes its potential viability. Following this, two approaches to clock synchronisation assisted CDR are investigated: 1. Clock phase caching, which uses clock phase storage and regular updates in a 2km intra-building scale data centre network interconnected by single-mode optical fibre. 2. Single calibration clock synchronisation assisted CDR}, which leverages the 20 times lower thermal sensitivity of hollow core optical fibre versus single-mode fibre to synchronise a 100m cluster scale data centre network, with a single initial phase calibration step. Using a real-time FPGA-based optical switch testbed, sub-nanosecond CDR locking time was demonstrated for both approaches.