IN MY OPINION

Time to Reevaluate RF and Microwave Power Application Development

By Dan Viza, RF and Emerging Markets Manager Freescale Semiconductor

The methods for evaluating RF power components for use in RF and microwave applications have seen relatively little change over the years in spite of the expanding universe of RF applications.
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MILITARY MICROWAVE DIGEST


MMD March 2014
New Military Microwave Digest

ON THE MARKET


Band Reject Filter Series
Higher frequency band reject (notch) filters are designed to operate over the frequency range of .01 to 28 GHz. These filters are characterized by having the reverse properties of band pass filters and are offered in multiple topologies. Available in compact sizes.
RLC Electronics


SP6T RF Switch
JSW6-33DR+ is a medium power reflective SP6T RF switch, with reflective short on output ports in the off condition. Made using Silicon-on-Insulator process, it has very high IP3, a built-in CMOS driver and negative voltage generator.
Mini-Circuits


Group Delay Equalized Bandpass Filter
Part number 2903 is a group delayed equalized elliptic type bandpass filter that has a typical 1 dB bandwidth of 94 MHz and a typical 60 dB bandwidth of 171 MHz. Insertion loss is <2 dB and group delay variation from 110 to 170 MHz is <3nsec.
KR Electronics


Absorptive Low Pass Filter
Model AF9350 is a UHF, low pass filter that covers the 10 to 500 MHz band and has an average power rating of 400W CW. It incurs a rejection of 45 dB minimum at the 750 to 3000 MHz band, and power rating of 25W CW from 501 to 5000 MHz.
Werlatone


LTE Band 14 Ceramic Duplexer
This high performance LTE ceramic duplexer was designed and built for use in public safety communication and commercial cellular applications. It operates in Band 14 and offers low insertion loss and high isolation to enable clear communications in the LTE network.
Networks International

See all products in this issue


August 2014

Next Generation Phased Radar Systems Lead to Hardware Improvements
By Renaissance Electronics & Communications

More compact, lightweight and efficient power dividers increase resolution and range of next wave of fixed phased array systems

Meeting the performance needs of the next generation of radar systems that will be deployed by the military is spurring the development of more efficient and sensitive hardware components to go along with the rapid advances in signal processing techniques and bandwidth.

The military uses radar for many purposes, including guiding missiles to targets, directing the firing of weapon systems, and providing long-distance surveillance and navigation information.

However, for the next generation of systems currently in development, the most critical requirement is the ability to successfully counter saturation attacks. Such attacks may include numerous aircraft and missiles converging from multiple directions at the same time.

To meet this challenge, very high data rates are required to track a large number of simultaneous targets. Unfortunately, the level of data quality required is not achievable with the traditional rotating or fixed radar systems in use today.

Mechanical Rotation
Radar systems are often identified by type of scanning. The most common, mechanical scanning, involves the rotation of a parabolic dish or antenna through a 360 degree sweep of the horizon. As it rotates, pulses of radio waves or microwaves are transmitted and bounce off any object in its path. The object returns a tiny part of the wave’s energy.

These systems are not without limitations, however. Such systems provide limited tracking capabilities. Upon detecting a potential target, the radar typically waits a second or two for an additional sweep return so that it can correlate the two echoes, extract course and speed information, and start a new tracking process. Depending on the sweep rate, this wastes valuable time against an incoming enemy aircraft or weapon.

Mechanical scan radars are also susceptible to damage. If the servo motors that cause the antenna to rotate or stabilize it, fail or the antenna is damaged, the radar is rendered inoperable.

As a result, later generations of radar moved away from mechanical scanning toward fixed, phased array radar systems in which all movement is eliminated.

Fixed Phased Arrays
Phased arrays are composed of evenly spaced antenna elements, each of which emits a signal that incorporates a phase shift to produce a phase gradient across the array. The amplitudes of the signals radiated by the individual antennas and the constructive and destructive interference caused by objects determine the effective radiation pattern of the array.
By digitally varying the signal phases and amplitude of the elements in an array—a process known as digital beamforming—the main beam can be “steered” to determine the direction of the signal source, even though the antenna does not physically move.

Because of the rapidity at which the beam can be steered, phased array radars can perform search, track and missile guidance functions simultaneously with a capability of over a hundred targets.

Phased arrays systems vary in size and complexity. For several decades, massive planar arrays have been used aboard Navy warships and are at the heart of the ship-borne Aegis combat system and the Patriot Missile Systems. Smaller phased array antenna can be built to conform to specific shapes, like missiles, infantry support vehicles, ships, and aircraft.
Although there are several ways to accomplish electronic beam steering, one such technique involves varying the phasing between elements in a fixed, multi-element array. This is typically accomplished with power dividers that emit signals of varying phase and amplitude to the antennae.

As an example of the hardware improvements required in next generation systems, power dividers serve as a prime example.

Hardware Improvements—Power Dividers
Power dividers are passive components that divide an input signal into two or more identical output signals. For phased array systems that require a range of signal amplitudes, the input signal is often altered using attenuators to vary the signals prior to output to deliver the desired signal level.

The traditional way of accomplishing this is to utilize a standard multi-channel power divider with attenuators at each of the output ports. Attenuators, however, increase the overall size and weight of the unit while drawing additional precious watts of power. The size and weight of the power divider with attenuators made it difficult to deploy on jet planes that could benefit from more sophisticated radar.

Renaissance Electronics & Communications, a manufacturer of RF and Microwave sub-systems and components, has designed a power divider that splits power from 6.7 to 18.4 dB across the output ports that does not require attenuators. Operating between 1100 and 1500 MHz, this 8-way divider is optimized for space constrained applications at only 8” x 5” x .5”. The divider can handle 350W peak and 35W CW.

The output signal is staggered in fixed amplitudes that begin at 18.4 dB at ports 1 and 8; 12.4 dB at 2 and 7; 8.6 dB at 3 and 6 and 6.7 dBs at ports 4 and 5. The 8 output ports are each connected to a fixed antenna.

The Renaissance power divider provides 35-40% more resolution and extends the coverage from one mile to several miles.

According to a spokesperson at Renaissance Electronics, the next generation of phased array systems along with advanced signal processing techniques could have significant benefits for many branches of the military.

For example, higher resolution radar could be used to initiate a computer takeover in the event of a missile attack on a jet plane. Using sophisticated evaluation of the missile’s speed and trajectory, millisecond to millisecond, computer-controlled micro adjustments could be used to evade the threat.

In an intense battlefield with numerous vehicles and personnel, advanced radar could be used to not just track high speed targets, but also slow moving targets like ground troops. Armed with this information, the command center could have complete, real-time visibility of all moving components of a battlefield.

Renaissance Electronics & Communications
www.rec-usa.com
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FROM WHERE WE SIT

Uncertain Times for DefenseIn Defense of DARPA; Lamenting Bell Labs
By Barry Manz

A federal agency like DARPA is a sitting duck for politicians and assorted other critics. It has come up with some truly bizarre programs over years that ultimately either delivered no tangible results, were canceled before they could cause any damage, or attempted to answer questions that nobody was asking or needed answers to. Read More...


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