Decades of Innovation: Past, Present and Future

Aeroflex / Weinschel is celebrating 60 years of operations since founder Dr. Bruno Weinschel set up shop in 1952 manufacturing passive microwave components, including the world’s first commercial coaxial attenuators. At the time, the technology to produce and measure precise passive microwave components was in its infancy. Dr. Weinschel played a key role in advancing the early state of attenuation-based technology and measurement equipment.  Since then, the company has progressed with the times and demands of the markets it serves, enhancing the performance and capabilities of RF and passive microwave components into a broad range of products that includes fixed and programmable attenuators, commercial off-the-shelf and custom subsystems, and unique connector system solutions for a wide range of challenging test, simulation and RF distribution applications. The times may have changed but the company’s longevity is a testament to the market demand for signal control products that have evolved to include a wide range of subsystem solutions far beyond that original attenuator technology.

Dr. Weinschel came to the United States as an eighteen-year-old genius with the equivalent of a Bachelor’s degree in physics and a wealth of hands-on mechanical training. Studying under Nobel Prize winners Isidor Rabi and Enrico Fermi at Columbia University Graduate School, Dr. Weinschel was first exposed to microwave measurements when he was tasked with building a 1300 MHz source for investigating the magnetic moment of molecules. Accepting a job as a supervisory engineer at Bell Labs (1943-44), the German-born physicist found himself designing microwave test equipment side-by-side with American engineers possessing a minimal understanding of microwave theory. Dr. Weinschel’s physics background proved invaluable in designing equipment for precise attenuation measurements and industry standards. As chief engineer at Industrial Instruments (1944-48), and then section chief at the National Bureau of Standards (1949-52), Dr. Weinschel convinced his management to let him work on coaxial attenuators, advancing the work he had started at Bell Labs. Developing attenuator technology for the Army’s ordnance development, he was responsible for a classified contract working on techniques to measure the microwave reflections used to trigger proximity fuses. Dr. Weinschel’s engineering passion and drive to improve the performance of his attenuator technology eventually led him to set up a private laboratory and to discover a market for precision attenuators. To avoid any perceived conflict of interest, he left the NBS to form Weinschel Engineering and continue developing the technology that is so critical to today’s RF and microwave signal control and measurement systems.  Dr. Weinschel received the National Medal of Science under President Regan. He also served as IEEE president in 1986 and the chairman of the Committee on U.S. Competitiveness (1988) for the IEEE.

Thriving through multiple ownership and name changes, including Lucas Industries PLC and Lucas Weinschel (1986), Sierra Networks and Sierra Weinschel (1995), MCE Technologies Inc. and Weinschel Corporation (1995), and the Aeroflex purchase of MCE / Weinschel which created the current Aeroflex / Weinschel (2003), the company has emerged as an industry benchmark in quality products and service. “The company formed as Weinschel Engineering, Co. in 1952, has changed ownership seven times, having successfully transitioned from a privately held company, to a division of a foreign-owned corporation, to a division of a publicly traded company. The company has managed to survive multiple recessions, various war-driven economies and national budget-constrained times, and through it all, remained a market leader, continuing to re-invent itself with new products that provide solutions to today’s market needs,” says Robert L. Stephens,
Aeroflex / Weinschel president and general manager.

In the early 70s Dr. Weinschel saw the demand for fixed RF attenuators grow rather fast, beyond the test and measurement applications of the laboratory. He wanted to improve on the RF connector design. At the time the insulators and center contacts were pressed into a jack or plug body and held together with epoxy, injected from a side hole. This made the connectors inherently leaky to RF waves. Dr. Weinschel wanted to address this leakage problem while moving to higher volume manufacturing, so he invested heavily in injection mold machines from Germany.

Every connector type, either SMA or type N, needed a complicated mold fixture to get the desired final connector, with the support insulator, the center contact and the jack/plug body all neatly molded in one piece without the need for any epoxy. Weinschel was the first company to supply Injection molded RF connectors into its commercial product line. Today the same process has been extended beyond SMA and type N connectors. Type SMK (2.92mm) and 2.4mm connectors are also molded in a multi-cavity mold. Injection molded connectors are rugged and reliable, have a consistent pin recession and offer the lowest RF leakage.

In conjunction with the attenuator development and other resistive base components, the need arose to make accurate insertion loss measurements. This need resulted in the development of precision measurement and calibration instruments. These instruments were originally designed for their own use, but the demand for this type of equipment by other laboratories was so great that Weinschel decided to make their calibration instruments available industry wide. This effort produced several products such as attenuator calibrators (BA-5 & VM-3), differential null detectors, double stub tuners, AF-substitution attenuators, modulated RF sources and other test and calibration of instruments. Weinschel’s engineering and calibration staff has received over 40 patents and had over 70 technical articles published. This innovation has aided in their development of precision measurement and calibration equipment. In November 1997, this instrument line was sold to Tegam where they still manufacture these products today.

Look no further than its list of patents, past and present, which set the foundation for Weinschel’s technical history. Its patents in attenuation measurements and design, connectors, detectors, frequency control, impedance measurement, power measurement, RF sources, step attenuators and tuners paved the way for the company’s current business strategy. The evolution and success of Weinschel lies in its ability to adapt to changing market conditions and customer demands while simultaneously maintaining the core technologies, product development, processes and procedures. Innovation at Aeroflex / Weinschel is reflected in its ever-expanding line of RF and microwave components and subsystems. From the company’s very first DC to 1 GHz tee attenuator came the technology that fostered the design of the industry’s very first 500 W, DC to 10 GHz and 20 W, DC to 40 GHz attenuators, to name just two. These planar distributed resistor  elements, form the basis for most all attenuators manufactured today from DC to 65 GHz.

Aeroflex / Weinschel utilizes both a thick film process, for DC to 3 GHz programmable attenuators, and a thin film process for the development of its resistors. The company utilizes a proprietary chemical vapor deposition (CVD) where a tin oxide (SnO) film doped with antimony (Sb) is sprayed onto a ceramic and the deposition takes place at a very high temperature. This technology and process gives Aeroflex / Weinschel’s thin film products extreme ruggedness and high power handling capability at very high surface temperatures. Doping  the film with  Antimony results in an industry standard setting attenuator performance with low  power and temperature  coefficients, long term stability and endurance under high power.  It also allows Weinschel to offer  a wide variety of low intermodulation (IM) attenuators and terminations. Today Aeroflex / Weinschel offers the broadest frequency and power handling performance envelope in the industry.

In the late 70s Weinschel obtained a patent on a 2 GHz relay based programmable attenuators. They used relays from Teledyne and were built on alumina with thick-film circuitry providing a patented scheme for tuning each individual attenuator. The result was a flat frequency response over DC to 2 GHz, quite unmatched in those early days. This attenuator formed the foundation of today’s long list of programmable attenuator products spanning from DC to 6 GHz to DC to 26.5 GHz. The various programmables use either microstrip or edge-line as the transmission medium. Electromechanical relays, Edge line Reed Switches, PIN diodes, FETs or MMICs provide the programmability and the switching function, depending on the application.

As customer demand for faster switching speed within the telecommunications industry increased during the mid 90s, mainly for simulation and handover testing of mobile phones, Weinschel saw the need to develop its own line of solid-state GaAs and pin switched programmable attenuators for its own attenuation matrices. New requirements from end-users to reduce cost and provide portability has produced a line of MMIC switched digital attenuators that are low profile and operate to 6 GHz up to 95 dB.  Control for these devices was also an important consideration, which led Aeroflex / Weinschel to incorporate both built-in TTL and USB 2.0 interfaces.  This device is programmed to auto select the type of control that is connected to the device.  Included attenuation control center software makes it even easier to operate whether the device is in a bench or field application. In a majority of its wide product line, including high-reliability products, Weinschel does not use any solder, either to launch onto the substrate or for RF grounding. Every product has a unique gold-plated spring mechanism to provide RF and thermal grounding. Each product also has a spring loaded connector end launch onto the RF circuitry. These two features make the products virtually immune to mechanical shocks and thermal extremes, a very important requirement of high-reliability products being launched into space.

Figure 1

Figure 1 Cross section of Planar Crown® Universal Connector System.

Industry demand for high performance connectors led Weinschel to develop an innovative specialized planar connector systems. The Planar Crown® Universal Connector System, which is comprised of two connector halves/subassemblies, has a common mating interface referred to as the Planar Interface (see Figure 1). The first connector half is called the Planar Bulkhead which readily mounts into instrument front panels, components and cables. One end of this bulkhead has a 2.92mm (SMK) male/female primary connector. The other end has a combination of grooves, external threads and a coaxial Planar Interface with a 2.92mm (SMK) airline geometry. The bulkhead operates mode free beyond 40 GHz. The second, replaceable connector half, called the Planar Crown, has corresponding projections which interlock with slots on the bulkhead and a coupling nut which secures the two connector halves, resulting in a non-rotational, torque independent electrical connection.

The spring biased inner and outer contacts eliminate the need for specifying proof torque and no tools are required to mate or unmate the connection. The primary end of the Planar Crown is offered in a variety of primary coaxial connector configurations such as SMA, Type N, GPC-7, TNC, 3.5mm, 2.92mm (SMK) and 2.4mm (under development), thus providing an extremely versatile connector system wherein a connector can be replaced in a matter of seconds.

The Planar Blind-mate Connector Series was designed for threadless connector mating that is useful when mating an array of connectors from one RF module to another in seconds. This design provides a “forgiving” mechanical interface that can permit a 0.02 mis-alignment. These connectors offer dc to 40 GHz operation, a contact life of 1.0 m cycles and a repeatability of 0.05 dB typical per connection. Other features of this connector series include pressurized and unpressurized designs, SMA and SMB connector options and a space saving and rugged construction.

Today Aeroflex / Weinschel buildsproducts for a host of customers, including leading aerospace and defense contractors, commercial wireless network providers and test equipment manufacturers. The company’s subsystem development activity focuses on custom products employed in telecommunications, radar and CNI, satellite and ground communication systems, base station and mobile unit software conformance verification, signal analysis, cable modem and VoIP testing, production test systems and precision microwave related test instruments. These custom subsystems include attenuator and switch matrices and RF distribution systems.

Weinschel’s subsystem group has developed a modular approach, trademarked “SmartStep®,” that utilizes a single controller that provides control of digital and programmable attenuators, switches and other devices using various industry standard communications interfaces (GPIB/IEEE-488, RS-232, RS-422, RS-485) to the serial Driver Interface Bus. New designs will include a USB 2.0 Full-Speed configuration, which is 12 Mbps and is compatible with 1.0 (1.5 Mbps) and 1.1 (12.5 Mbps) speeds. The Device Interface Bus (DIB) is a system for connecting a number of relatively low-speed I/O devices to a host, providing a simple, uniform and inexpensive way to control a variety of devices via a single port. The DIB is based on the two-wire serial bus and several software protocol layers that allow the controller to address up to 125 peripheral devices with serial data rates of up to 100 kHz. The DIB is also used to supply DC power to the devices, resulting in a simple, low-cost interconnection system. The future requirements placed on RF and microwave signal control circuitry by the industry will spirit innovation that started with Bruno Weinschel and the company that bears his name.