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Everardo Laboy
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"Biological optimization" (BIOP) means planning treatments using (radio)biological criteria and models, that is, tumour control probability and normal-tissue complication probability. Four different levels of BIOP are identified: Level I is "isotoxic" individualization of prescription dose D(presc) at fixed fraction number. D(presc) is varied to keep the NTCP of the organ at risk constant. Significant improvements in local control are expected for non-small-cell lung tumours. Level II involves the determination of an individualized isotoxic combination of D(presc) and fractionation scheme. This approach is appropriate for "parallel" OARs (lung, parotids). Examples are given using our BioSuite software. Hypofractionated SABR for early-stage NSCLC is effectively Level-II BIOP. Level-III BIOP uses radiobiological functions as part of the inverse planning of IMRT, for example, maximizing TCP whilst not exceeding a given NTCP. This results in non-uniform target doses. The NTCP model parameters (reflecting tissue "architecture") drive the optimizer to emphasize different regions of the DVH, for example, penalising high doses for quasi-serial OARs such as rectum. Level-IV BIOP adds functional imaging information, for example, hypoxia or clonogen location, to Level III; examples are given of our prostate "dose painting" protocol, BioProp. The limitations of and uncertainties inherent in the radiobiological models are emphasized.
Atoll includes advanced multi-RAT RAN design capabilities for 2G, 3G, 4G, and 5G radio access technologies. It supports the latest technology advances including massive MIMO, 3D beamforming, and mmWave propagation for the design and roll-out of 5G networks.
Atoll is a comprehensive multi-technology radio planning and optimisation platform which includes unified multi-technology traffic models, Monte Carlo simulators, and automatic cell planning (ACP). Atoll can model the traffic-related aspects of multi-technology networks and dynamically spread traffic across 2G, 3G, 4G and 5G network layers comprising macro, micro, small cells, and Wi-Fi hot spots.
Atoll offers unique capabilities of using both predictions and live network data throughout the RF network planning and optimisation process. Live-network data (KPIs, UE/cell/MDT traces, and crowdsourced data) add real-world information to predictions allowing for enhanced modelling of traffic evolution, hot-spot identification, and radio signal propagation. Live-network data can also be used in Atoll to drive the planning process (site selection) and to steer the optimisation algorithms of the AFP (Automatic Frequency Planning) and the ACP.
The new Atoll In-Building module allows in-building wireless network design within the Atoll framework, providing operators with unique indoor/outdoor network planning capabilities. Atoll In-Building includes a comprehensive set of indoor planning features, such as modelling of floor plans and building elements, indoor propagation, equipment installation layouts, and automatic calculation of bills of materials, that enable operators to streamline the overall indoor/outdoor RAN planning process.
With industrial/scientific/medical (ISM) band radio frequency (RF) products, often times users are new to the structure of Analog's low pin-count transmitters and fully integrated superheterodyne receivers. This tutorial provides simple steps that can be taken to get the best performance out of these transmitters and receivers while providing techniques to measure the overall capability of the design.
Every day more industrial, scientific, and medical (ISM) band radio frequency (RF) products reach the marketplace. With so many offerings available, it is not surprising that users are often unfamiliar with the structure of low-pin-count transmitters and fully integrated superheterodyne receivers. This tutorial presents simple steps that designers can follow to achieve the best performance from these transmitters and receivers. Techniques to measure the overall capability of these designs are also provided.
There are only two basic steps used to optimize the operation of a simple ISM transmitter (shown in Figure 1): make sure that the reference frequency is properly tuned, and correctly match the output network of the transmitter to the antenna. A crystal oscillator is commonly used as the reference in both the transmitter and receiver circuits, so that optimization technique is addressed in the Receiver Optimization section below.
After establishing a starting point, adjustments are guided by measuring the transmitted power and the PA current as a function of frequency. The measurement setup is shown in Figure 3. The fixed crystal is removed from the board; an external signal generator is connected through a blocking capacitor to the crystal pin to allow the adjustment of frequencies from about 11MHz to 15MHz (for transmitted RF from 352MHz to 480MHz). The peak-to-peak voltage from the generator is set to about 500mV.
At each frequency, the transmitted power and PA current are measured and the results are plotted. Component values in the matching network are changed (Figure 1) until an optimized current minimum and a power maximum are achieved near the desired frequency (in this case 434MHz).
The plot of current versus frequency (Figure 5) shows how each change in the matching network moved the current minimum to a different frequency. The graph for the best match at 434MHz is shown in yellow. Notice that the values of C9 and L2 have changed noticeably (from 15pF and 39nH) as a result of the component and board parasitic contributions.
The process of matching for Tx, PA power, operational frequency, and antenna impedances can be found in application notes 1954, "Designing Output Matching Networks for the MAX1472 ASK Transmitter," and 3401, "Matching Analog's 300MHz to 450MHz Transmitters to Small Loop Antennas."
The basic steps for optimizing the operational characteristics of an ISM superheterodyne receiver start with a systematic evaluation of the receiver blocks. There are commonly four blocks where performance can be improved: the crystal oscillator circuit, the antenna matching circuit, the tank circuit, and the baseband circuit.
One of the most common challenges associated with crystal-based receivers and transmitters is proper tuning of the radio's oscillation circuit. The oscillator on ISM radios is intended to operate using a crystal specified with a specific load capacitance (Figure 6). In some ISM receivers, the crystal is typically specified for a 3pF load capacitance. This low value is not a very common specification for crystals. Typically because of cost or supply considerations, customers attempt to design a system using a crystal with a tested load capacitance of 6pF, 8pF, 10pF, or more. Using these larger load capacitance crystals is not prohibitive, but does present a trade-off since the oscillator circuit will only provide the specified load capacitance to the crystal pins. For example, a 3pF load will cause a 10pF specified crystal to operate at a noticeably higher frequency than intended. (For more information, see application note 1017, "How to Choose a Quartz Crystal Oscillator for the MAX1470 Superheterodyne Receiver..") To compensate for this shift in frequency, a customer can present a larger load to the crystal by placing capacitors in the circuit. Our experience recommends two shunt capacitors to ground rather than a parallel arrangement for enhanced flexibility and other loading benefits. The trade-off with this "adjusted" load is that too much capacitance connected to the circuit could cause a problem with the oscillation startup.
A debug measurement was made to investigate the oscillating frequency of the crystal populated on the above reference design. To perform this test, an R&S ZVL3 spectrum analyzer and a "sniffer" antenna were used to probe the crystal frequency. This antenna was held in close proximity to the crystal (or touching one of the leads, as needed) to obtain an estimate of the operating frequency. The system was populated with a 13.2256MHz crystal that had a specified CL of 8pF, but the oscillator circuit only provided about 3pF of load. The peak of this system was measured at 13.23049MHz, which is high by 370ppm. This translates to an operating frequency of 434.085MHz (32 13.23049 + 10.7), which placed the expected LO and carrier frequency 165kHz higher than intended. This off-frequency operation of the crystal oscillator resulted in an incoming ASK carrier and associated sidebands being pushed to the edge and even past the "knee" of the IF filter. This caused an unnecessary attenuation of the signal power.
To further test the impact of this frequency error, the passband of the IF was tested. By sweeping the carrier signal in frequency and monitoring the IF filter output with the spectrum analyzer in max-hold mode, a plot of the filter bandwidth was collected. Marker M1 was placed at 10.7MHz (nominal center of the IF filter) and the delta marker, D2, was placed at the frequency spike where the RF signal was tuned to 433.92MHz. The signal generator was set to 434.085MHz when the IF spike was at M1, confirming the shift in LO frequency. The plot illustrated in Figure 7 shows that the mistuning degrades the carrier by about 7dB. Sideband information needed for ASK demodulation is actually attenuated further, and distorted due to the nonlinear location on the filter curve.
As a first-order attempt to improve the sensitivity of the demonstration LFRD014: Tube Motor Receiver Reference Design module, two 10pF shunt caps were added at C21 and C22. The resulting crystal oscillator frequency was confirmed to have moved and was now operating at the corrected frequency of 13.226MHz. After adjusting the RF generator to be centered back at 433.92MHz, sensitivity was measured at -107dBm. This 12.4dB improvement resulted from the proper tuning of the reference frequency for the local oscillator.
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