Interconnect Advances Fuel Technology Growth
By Orwill Hawkins, Vice President of Marketing, LadyBug Technologies
With increased frequencies, higher data rates, and lower noise levels, the microwave industry serves as a leader in technological capability. Demand for quality interconnects has increased right along with other higher-performance areas in the industry.
|MILITARY MICROWAVE DIGEST
E-Band Active X5 Multiplier
Model SFA-743843516-12SF-N1 is an E-band X5 active multiplier with center frequency at 79 GHz with minimum +/-5 GHz operational bandwidth. It converts 14.8 to 16.8 GHz/+5 dBm input signal to deliver 74 to 84 GHz frequency band with more than +16 dBm power.
Hand-Flex™ Coaxial Cable
Covering DC to 12.5 GHz, this 8” coaxial cable, 141-8SMNB+, has a bulkhead Female Type-N connector at one end and SMA-Male at the other. Features include low loss, excellent return loss, hand formable, and an 8mm bend radius for tight installations.
Phase Trimmer Series
This new phase trimmer series is designed for RF applications where phase match between two cables is needed for proper system performance. Phase trimmers, offered from DC to 50 GHz, will give an accurate phase adjustment over a specified frequency range.
Planar Monolithics Industries
Model PTRAN-100M18G-SFB-3UVPX-MAH is a transceiver covering the frequency range of 100 MHz to 18 GHz. The transceiver fits into a 3U Open VPX form factor utilizing the high speed VITA 67 RF connector.
Planar Monolithics Industries
SMT High-Power Attenuators
Now available with full design support capabilities are three new SMT high-power attenuators from Anaren. These 30 to 50W devices are high-performance, high-power chip attenuators covering DC to 3.0 GHz and feature high return loss and small footprints.
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Doherty Amplifier: New After 70 Years
By Freescale Semiconductor, RF Division
The Doherty amplifier architecture has in
less than 5 years become the “amplifier of choice”
for new wireless transmitters after essentially laying dormant
since W.H. Doherty first described it in 1936. The Doherty’s
obscurity is directly attributable to the predominant modulation
schemes (AM and FM) employed in communication systems over
the years, which do not possess high peak-to-average ratios
(PARs). The resurgence of interest in the concept is based
on its very high power-added efficiency when amplifying
input signals with high PARs – precisely the type
exhibited by WCDMA, CDMA2000, and systems employing Orthogonal
Frequency Division Multiplexing (OFDM), such as WiMAX and
the upcoming Long-Term Evolution (LTE) enhancement to the
UMTS wireless standard.
In fact, when properly designed, a Doherty
amplifier can produce increases in efficiency of 11% to
14% when compared to standard parallel Class AB amplifiers
that have traditionally been employed in wireless base station
transmitters. Since the transmitter accounts for a high
percentage of overall system power consumption, the cost
savings delivered by the Doherty amplifier’s efficiency
can reduce base station annual electricity costs. Thus its
appeal for wireless base station manufacturers and wireless
While the intrinsic high efficiency of the Doherty architecture
makes it desirable for current and next-generation wireless
systems, it presents unique challenges from a design perspective.
The linearity and output power of the Doherty architecture
are slightly less than exhibited by a dual Class AB amplifier,
and it can produce higher distortion as well. Fortunately,
the advancements in analog and digital predistortion and
feed-forward linearization techniques can dramatically reduce
the Doherty’s distortion. In addition, careful amplifier
design can mitigate its inherently lower linearity. The
remaining challenge is to create RF power transistors that
can accommodate the requirements of the two types of amplifiers
employed by the Doherty architecture and produce optimum
RF output power over a wide array of signal conditions.
A Doherty overview
A “classic” Doherty amplifier (Figure 1) employs
two amplifiers. The carrier amplifier is biased to operate
in Class AB mode and the peaking amplifier is biased to
operate in Class C mode. The input signal is split by a
power divider equally to each amplifier with a 90-deg. difference
in phase. After the signals are amplified, the signals are
recombined with a power combiner. Both amplifiers operate
when the input signal peaks, and are each presented with
the load impedance that enables maximum power output. However,
as the input signal decreases in power, the Class C peaking
amplifier turns off and only the Class AB carrier operates.
At these lower power levels, the Class AB carrier amplifier
is presented with a modulated load impedance that enables
higher efficiency and gain. The result is an extremely efficient
solution for amplifying the complex modulation schemes employed
in current and emerging wireless systems.
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In 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...