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vor 7 Jahren

10-2016

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  • Quarze
  • Emv
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  • Frequenzbereich
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Fachzeitschrift für Hochfrequenz- und Mikrowellentechnik

RF & Wireless Figure 5:

RF & Wireless Figure 5: The Smith chart shows the Input impedance to an isolated element and to elements when the entire array is simulated. Load pull contours for power getting to the load are also shown tic example would simulate the layout of the feed network in an EM simulator to make sure the models are accurate and there is no unintended coupling between sections of the network. Typical circuit simulation results are shown in Figure 5. The system is designed to work at 10 GHz. The purple curve shows the input impedance for an isolated patch from 6 to 14 GHz on a 50 Ohm normalized Smith chart. The marker shows the normalized impedance at 10 GHz. The four crosses show the input impedance of four typical elements at 10 GHz. Note that the interaction between the elements in the array shifts the input impedance of each element from that of an isolated patch. The green contours are load-pull simulations for the MMIC amplifier, showing the power delivered to a load. The shifting of the impedances of the antenna feed results in a 0.5 dB degradation of power to the elements. (Figure 5 power contours are in 0.5 dB increments.) Examples of the antenna pattern are shown in Figure 6. The beam is steered by controlling the relative phasing and attenuation to the various transmit modules. In practice, the harmonic balance takes substantial time to run with 16 power amplifiers. Therefore, the beam is steered with the amplifiers turned off. The designer then turns on the power amplifiers for specific points of interest. Note: the far right image in Figure 6 shows a second lobe created when the main lobe is at a near grazing angle. This second example is an 8X8 patch array. Anything that can be tuned in Microwave Office can also be optimized. For example, in Figure 7, the antenna pattern is optimized for a certain scan angle. In the interests of time, the amplifiers are not included in the optimization. At the end the amplifiers are turned on to see the amount of degradation. The plot is of the total power in the beam, scanning in the theta direction with phi at 0 degrees. The blue bars show the optimizer goals for the measurement. The purple pattern is the original broadside pattern. The optimizer changes the phase and attenuation at the feeds to the patches. The resulting blue curve meets Figure 6: The beam of the array as it is scanned throughtypical values of theta and phi the optimization goal of scanning at 20 degrees with acceptable side lobe levels. Conclusion In conclusion, designing antennas with multiple feed points for communications or radar systems requires simulation of the interaction that occurs between the circuit, typically a highly nonlinear power amplifier, the feed network, and the antenna. The beam is steered by the circuitry, and as the beam changes the input impedance or input characteristics of the antenna change, which effects the circuit. The circuit and the antenna are connected, so both must be included in the simulation. The traditional method of simulating antennas with multiple feeds is to simulate the coupled antenna/circuit effects manually using an iterative process that is time consuming and frustrating. Microwave Office circuit and antenna simulation are coupled together, enabling arrays to be easily excited from the amplifier and feed network. The load impedances of the array are incorporated into the circuit simulation. This automates the process, saving design time and delivering products to market faster. ◄ Figure 7: The antenna pattern is optimized to be below the blue bars 52 hf-praxis 10/2016

RF & Wireless Components Phased Array GaN MMIC Reference Design Plextek RFI has announced a new reference design for a GaN power amplifier (PA) MMIC for use in X-band active phased array radar applications. “Active phased arrays require numerous PAs, which need to have high efficiency, and to have a small size and relatively low cost,” said Liam Devlin, CEO of Plextek RFI. “Our new design has a die size of only 1.5 x 2 mm, which means around 2,300 PAs can be fabricated on a single 4-inch (100 mm) diameter wafer. This makes the cost very competitive compared with other commercially-available MMICs offering this level of RF output power.” The X-band GaN PA MMIC covers 9 to 11.5 GHz and delivers 7 W (38.5 dBm) of RF output power from a 29 dBm input, with a Power Added Efficiency (PAE) of 42%. This means that it can be driven by readily available GaAs parts when used as the output PA stage. Plextek RFI designed the MMIC using Keysight ADS 2015, and it was manufactured by UMS on its 0.25 µm gate length GaN-on- SiC process (GH25). “As the IC is designed and manufactured in Europe, it will have the added advantage of not being subject to US export control,” added Liam Devlin. ■ Plextek RF enquiries@plextekrfi.com www.plextekrfi.com RF- and Microwave-Lab - from „DC“ about 100 GHz The Company Dirk Fischer Elektronik (DFE) is a RF- and Microwave-Lab and was founded by Dr. -Ing. Dirk Fischer more than 20 years ago. DFE is engineering and manufacturing RFmodules as well as entire systems for a lot of customized applications. They are used at Universities, Institutes and companies from SMEs to large concerns. During the last years DFE has engineered hundreds of different designs which could be adjusted for new applications within a short time. The frequency range is from DC (i.e. very long wavelength) up to 122 GHz, so the time needed for a new proposal or new orders at different frequencies is really fast. For the wireless Telecommunications LANs, Power-Amplifiers, Filters, Oscillators and Up-/ Downconverters are available. One main task are Power-Amplifiers, from 1 Watt to 10 kW (CW) respectively 50 kW (Pulse/10% Duty). Further on DFE offers nearly 40 different Wideband-Amplifiers from 1 Watt up to 500 Watt and from 100 kHZ up to 18 kHz. All these Power-Amplifiers utilizes GaAs as well as LDMOS and GaN. Further on DFE engineers and manufactures different types of RF- and Microwave-filters in the frequency range up to 26.5 GHz. The filters are customer-specif designs only. All kind of specification like low- and highpass-filters as well as bandstop- and bandpass-filters are offered. An interesting new design are filters with very low attenuation in the passband..This is the new Low-Loss-Filter Series. For example it is possible to manufacture lowpass filters with a cutoff frequency of 220 MHz and an attenuation of less than 0.1 dB. These filters are designed for high power purpose up to 10 kW (70 dBm resp. -20 dBM). An other important scope of DFE are antennas. Antennas are definitly „the best RF-amplifiers“ and indispensable for wirless transmissions. DFE generates prototypes and manufactures small to medium volumes at frequencies from shortwave up to mm-wave. The antennas are characterized at an own antenna test range. DFE offers from SMEs to large concerns, research facilities and from companys envolved in „other RF-related market segments“. These products are used at wireless telecommunications, EMC-laboratories, physical sensor technology and many other application areas, like „electromagnatic pulse technology“. In very special situations DFE is able to get the products on the road within a very short time. For the reactivation of the old ISSE-3 spacecraft in 2014, DFE has designed, manufactured and delivered an HPA at about 2 GHz with 60 dB gain and a power output of more than 500 Watt - in less than 3 weeks. Just beside RF and Microwave, DFE offers engineering in Hard- and Software since a few years - from C-code for 8Bit-µPs up to ARM controllers and VDHL codes for FPGAs. DFE has a direct contact to the customers. The developing and manufacturing in central Europe guarantees a fast communication and delivery. Dirk Fischer Elektronik (DFE) • Dr.-Ing. Dirk Fischer Stormstraße 23 • 48565 Steinfurt • Tel.: 02555/997074 dk2fd@t-online.de • www.dfe-online.de hf-praxis 10/2016 53

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