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.


MMD March 2014
New 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.
Sage Millimeter

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.
RLC Electronics

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.
Richardson RFPD

See all products in this issue

August 2007

The 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 service providers.

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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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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