Friday, December 23, 2016
Sunday, December 11, 2016
Monday, December 5, 2016
Sunday, November 27, 2016
Array Antenna Feed Networks
There is various kind of feeding network of an array antenna. Feed network depend on antenna type and geometry. Feed network for microwave applications is a major design concern in terms of complexity and size.
Passive Antenna Array
(a) Corporate Feed Network : For a passive antenna, most popular feeding networks type is corporate feed network as shown below in fig. This technique integrates the RF feed network with the radiating elements on the same substrate. Due to a large number of the microstrip line in corporate feed, it’s lossy especially at high frequencies. Minimization of losses in the microstrip feed network may result in microstrip antenna arrays with high efficiency. The efficiency of microstrip antenna arrays may be improved by using a waveguide feed network. However, this results in a significantly increase in the antenna weight and dimensions. In this case, a transition from microstrip to the waveguide is required.
Another technique to minimize feed network loss is multi-layer configuration. Conductor loss may be minimized by designing the feed network length per wavelength as short as possible. By using a multi-layer feed network design, the feed network length per wavelength is minimized considerably. Corporate feed is also called parallel feed network, in this equal excitation can be achieved at the expense of compactness.
( b) Inline Series Feed Network : In a series-fed array the input signal, fed from one end of the feed network, is coupled serially to the antenna elements. The compact feed network of series-fed antenna arrays is one of the main advantages that make them more attractive than their parallel-fed counterparts. Beside compactness, the small size of series-fed arrays results in less insertion and radiation losses by the feed network Usually series fed arrays are more efficient than corporate fed arrays. However, corporate fed arrays have a well controlled aperture distribution. Series feed configurations suffer from narrow bandwidth and inherent phase difference caused by the differences in lengths of feed lines. Below is example of end-fed series feed network
This is example of center fed series array
Active Antenna Array
Active Phased arrays are usually composed of a feed network and a number of phase shifters. In Active phased-array antennae are antennae transmit power is produced by many TX/RX modules. In these antennas, each element is connected with separate transceiver module, so every radiating element got a small power amplifier in the antenna directly. Active antennae are usually phased array antennae. These antennas are primarily used in remote sensing satellite, adaptive antenna, 5G Beam forming antennas and Radars
Feed networks are used to distribute the output signal of the transmitter to the radiation elements and phase shifters control the phase of the signals at each radiating element to form a beam at the desired direction.
Feed Network for Shaped Beam pattern Arrays
Sometime special feed networks is design to obtained shaped antennas radiation pattern. Below is example of Cosec square shape beam pattern antenna feed network
Saturday, November 26, 2016
Friday, November 25, 2016
Saturday, November 12, 2016
Tuesday, November 8, 2016
Monday, November 7, 2016
MODELING AND SIMULATION OF CHAFF CLOUD
Chaff finds are mainly used in electromagnetic countermeasures. A cloud of chaff is an artificial target made up of a bunch of small thin metallized glass fiber or wire. Chaff consists of thin dipole elements cut to resonate at radar frequencies. Chaff Clouds are dispensed in the air through the chaff cartridge on aircrafts. Chaff Cloud masks the real target return signal therefore, the detection of target become more complicated. The reflected signal from the chaff cloud disturbs the opponent’s radar system and creates a false signature in the enemy radar. Because of high RCS signature, after launching a chaff cloud, the incoming missile tends to track on the chaff. The aircraft can then perform a fast, sharp maneuver, deviating from the missile path.
Monday, October 31, 2016
Signal Integrity Analysis of High-Speed Interconnects
Signal integrity (SI) addresses two key aspects in high-speed digital designs: signal timing and quality. SI analysis aims to ensure signals reach their destination in good condition. In a system, signals travel through various kinds of interconnections (e.g., from chip to package, package to RF board trace and trace to high-speed connectors), with any electrical impact happening at the source end, along with the transmission path or at the receiving end, which affects both signal timing and quality. Connector performance directly affects system performance and reliability. As a result, designing and modeling connectors for multi-gigabit applications is one of the greatest challenges in high-speed digital applications.
When designing high-speed applications, the signal transmission quality is a critical factor. At gigabit speeds, high-speed interconnects must be characterized along with the RF board traces. The ever-increasing demand for cleaner signal transmission means that maintaining good signal quality throughout the high-speed interconnects is crucial. Modern high-speed, multi-pin connectors are required to enable data transmission in systems at a very high rate (~ 5 Gbps). Early design changes based on accurate simulations can be indispensable and worthy investments for interconnect realization. Likewise, use of an accurate electromagnetic (EM) model is highly desirable during the design and implementation stage of high-speed interconnects. To achieve good SI, the designer must not only understand the system in which the connectors will be deployed but also perform SI analysis of the RF board along with the connectors.
Read Complete Article…..
- The use of hybrid electromagnetic simulation to analyze the integrity of high-speed in-circuit signal connections – Russian Journal
- Analyze high-speed interconnects – EDN PDF version
- Paper Listing – The Library Book