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Industry News / Test and Measurement

A Test and Measurement Retrospective — 75 Years of Rohde & Schwarz

This is the story of how a two-man laboratory grew into a global group of companies

July 10, 2008
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This is the story of how a two-man laboratory grew into a global group of companies, how international success was achieved and how it is all connected to the history of microwaves.

Even before starting their company, Dr. Lothar Rohde and Dr. Hermann Schwarz jointly developed their first measurement instrument in 1932. Covering wavelengths from 3 m to 3,600 m, this precision interference wavemeter already touched the microwave spectrum — and defined the business focus of the company that was soon to be founded. In 1933 the company started out as “Physikalisch-Technisches Entwicklungslabor Dr. L. Rohde und Dr. H. Schwarz” dedicated to developing measuring equipment for high frequency engineering.

Now, 75 years later, Rohde & Schwarz has approximately 7,200 employees, which in the 2006/2007 fiscal year achieved total revenues of €1.4 billion, with 80 percent generated outside Germany. The company offers products in the fields of T&M, broadcasting, secure communications, and radiomonitoring and radiolocation, while its sales and service network covers more than 70 countries around the world.


The Founding Years: the Beginnings of Microwave Technology

At the start of the 20th century the development of microwaves and the related test equipment was still in its infancy. The renowned physicist Heinrich Hertz had already worked with 66 centimeter wavelengths when he proved the Maxwell wave theory in 1888. A few years later, the Indian physicist Jagadish Chandra Bose generated waves in the millimeter range. But the wide-scale use of such high frequencies was still far from common. Over the next few decades, efforts were directed at solving the existing technological problems because the transmission and measuring equipment necessary in order to generate microwaves — that is, electromagnetic waves in the decimeter, centimeter and millimeter ranges — required special components and configurations.

A standard book of reference on high frequency measurement technology from 1928 describes the frequency range covered by high frequency equipment of that era. As a matter of fact, it was low: The author, August Hund, sets the end of his frequency charts at 10 meter waves and refers to this range as high frequencies. To Hund, the term ‘microwave’ for waves in the decimeter, centimeter and millimeter range was unknown. When extremely high frequencies are discussed, he generally speaks of decimeter and centimeter waves. The term microwave first appears in the technical literature from the 1940s, although it is not seen in titles until technical books adopted it in the post-war years.

Incidentally, still today there are varying definitions of the lower limits of the microwave range. In 1945 the physicist Simon Ramo stated the following in his book Introduction to microwaves: “Microwaves is a name popularly given to electricity when its frequency of alternation is in billions of cycles per second.” Ramo thus defines 1 GHz as the lower end of the microwave spectrum. In 1947, another author set the lower limit at just 300 MHz, and in the following years the literature actually lowered it further to 100 MHz. The upper limit also varied widely over the years: between 300 GHz in 1947, 30 GHz in the 1950s and 100 GHz in 1980. When engineers speak of microwave technology today, they generally mean frequencies significantly higher than 1 GHz.

Rohde & Schwarz Debuts as a Company

One company that has been working in the microwave spectrum since the pioneering days is Rohde & Schwarz. The two young physicists Dr. Lothar Rohde and Dr. Hermann Schwarz completed their doctoral work under two icons of high frequency technology: Abraham Esau and Max Wien. Rohde took a job as Esau's assistant at the University of Jena, and Schwarz worked as a lightning protection specialist for the state of Thuringia at the university’s farming machinery institute. They had both been doing research in microwave measurement technology since their student days. In February 1931, for example, Rohde submitted an article to the renowned journal Zeitschrift für Technische Physik titled, A voltage measurement method for frequencies up to 1.5 x 109 Hertz. He described a solution that made it possible for the first time to measure voltages with small deviations in the Gigahertz range. The compensation method proposed by Rohde was significantly better than the method of the renowned British scientist E. B. Moullin, who worked in Cambridge and Oxford. In later years, the two company founders published further results on this topic.

Soon they began looking for a new area to work in. As luck would have it, they met Hans Handrek, an engineer with Hermsdorf-Schomburg-Isolatoren-Gesellschaft (Hescho). Hescho had developed new ceramic materials with extremely small dielectric losses in the high frequency spectrum. However, the institutes in Germany and abroad where Handrek sent samples of his materials all came up with different results when they measured the dissipation factors. To remedy this situation, Rohde and Schwarz developed an experimental set up that generated precise measurements very quickly.

It was now obvious: Industry needed equipment that Rohde and Schwarz were able to develop and manufacture. Consequently, the two PhDs went into business for themselves, founding the company Physikalisch-Technisches Entwicklungslabor Dr. L. Rohde und Dr. H. Schwarz (PTE) in Munich in 1933. They set up shop in an apartment measuring 120 m2 in Munich’s Old Town district (at Thierschstrasse 36). It was equipped with second-hand office furniture and workshop equipment. The laboratory also had a few measuring instruments.

PTE immediately began marketing its services to large electronics companies that needed someone to develop high frequency measuring equipment for them. PTE offered practical measuring instruments that could be operated even by people without special training in measurement techniques. Starting with the first orders received, the company was already working at the upper limit of the frequencies used in industrial applications at the time. Its first instrument, the WIP interference wavemeter which was developed for Hescho, could measure frequencies up to 100 MHz. The instrument covered the wavelength spectrum from 6 m to 3,000 m (100 kHz to 50 MHz) and became one of the top-selling products in the early decades of the company’s history. The WIP thus reached frequencies that were higher than the ‘top frequencies’ about which August Hund had written just five years earlier.

Growth: From Lab to Fab with Microwave Equipment

Dr. Rohde and Dr. Schwarz had discovered an untapped market. Their laboratory began to expand rapidly. In 1934, they hired their first engineer and leased an additional workshop when the original apartment proved too small. Plus, they had to modify their business concept, as many customers began asking for factory-ready instruments instead of just development work. The two partners agreed to begin production operations. Reminiscing in the early 1990s, Dr. Schwarz remarked, "As of 1936, we were producing measuring instruments 50 at a time to keep up with customer demand. But we were still basically doing everything by hand.”

PTE grew by leaps and bounds: In 1937, it purchased factory premises near Munich’s eastern railway station. By 1938, the company was already offering 100 different products, including the WAR resonance wavemeter. The instrument covered a spectrum of 75 MHz to 750 MHz, or 40 cm to 400 cm, with a tolerance of ±1 cm. This special microwave frequency detector implemented the resonance method. Resonance frequency detectors were less precise than interference wavemeters, but were also less complex. They consisted of nothing more than a tunable resonance circuit connected in parallel with a voltmeter, for instance a crystal detector. PTE marketed numerous models of the resonance frequency detector that enjoyed broad market success.

Another instrument developed during this period established the young Munich company as a player even beyond the German market: the CFQ, the world’s first portable crystal clock. The instrument could also be used as a standard frequency source, as it featured an accuracy of &plusmin;0.004 seconds a day. What set the clock apart was its weight — just 46 kg, including its rack. Competitor crystal clocks and the ones in use at the Physikalisch-Technische Reichsanstalt in Berlin were housed in large cabinets. The CFQ was suitable for any purpose, particularly as a frequency standard in test shops and labs.

In 1942, PTE received a large order to build radiomonitoring receivers. The core component for the instruments originated from a receiver that the company had developed in the years prior to World War II for field strength measurements in civil applications. The instrument covered a frequency range from 90 MHz to 470 MHz, and was later extended to 800 MHz. This project was too large for the company's existing production methods and capacity. A shift from lab to factory-style large-scale production was the consequence. In 1943/44, production operations were turned over to Messgerätebau GmbH in Memmingen. This company, whose operations were expanded in the 1960s, still has its headquarters in Memmingen today.

New Fields of Business: the Ban on Research in the Post-War Years

Shortly after the end of the war, Rohde & Schwarz was contracted by the US Army to inspect, adjust and repair radio systems. However, like all industrial companies in Germany, Rohde & Schwarz was initially barred from furthering the development of instruments in the microwave range. The Allies had imposed a ban on research, development and production when it came to frequencies above 300 MHz. Thus, when Rohde & Schwarz resumed production, it adapted its product portfolio to these conditions. The company manufactured telephone amplifiers, cinema amplifiers, sound equipment for theater stages and even a dance hall lighting system.

Telecommunications became one of the company's new main fields of business. Starting in 1948, more and more effort was put into the development of VHF FM technology. After the war, medium-wave frequencies were reassigned at an international conference in Copenhagen. Germany received very unfavorable frequencies. VHF FM offered an alternative. After only four months of work, Rohde & Schwarz premiered a fully functional 250 W VHF FM transmitter. It went on the air in 1949 — the first of its kind in Europe.

The production of measuring instruments was also soon resumed, albeit under the same constraints. In the early 1950s, Rohde & Schwarz achieved a breakthrough in network analysis with a product called the Zg diagraph. The instrument operated at frequencies up to 300 MHz and became the first complex network analyzer on the market. For the first time, direct measurements of the phase of S-parameters of a circuit became possible.

Although primarily used for measurements on radio and TV antennas, the Zg diagraph was also employed in the testing of special telecommunications cables. The measurement results were output in a Smith chart. This chart was generally used by microwave engineers as a basis for the graphical methods of circuit optimization which were very widely utilized at the time. Beginning in 1954, the Zg diagraph also became available with frequencies up to 2.4 GHz — as the restrictions on development and production had finally been lifted.

Like the Zg diagraph, the SWOB — a wideband sweep generator for measurements extending into the microwave spectrum — simplified many measurement processes. Although the sweep method was not new in high frequency measurement technology, it had the reputation of being very imprecise. “Sweep generators are used mainly for alignment, whereas the tried-and-tested point-by-point method is preferred when reliable and precise measurements are required,” said the Rohde & Schwarz developer H. Lucius in 1958.

It was at this time that the SWOB arrived on the scene to popularize the sweep method. The hugely successful instrument and its later models remained in production for decades, with several thousand units sold. It is also a testimony to the progress in microwave technology: The first generation of the SWOB achieved frequencies of up to 400 MHz, which its successors this range was stretched to 1 GHz. Other Rohde & Schwarz instruments operated with even higher frequencies: 2 GHz in the mid-1950s, 7 GHz in 1958 and 16 GHz in the mid-1960s. Step by step, the company pushed frequency limits upward with its measuring equipment.

The company’s growth during this period was equally impressive. During the decades immediately following the war, revenues increased by up to 50 percent a year. The number of employees expanded rapidly. In 1954, the company hired its thousandth employee. By 1960, the workforce had doubled to 2,000, and by the end of the decade the number had reached 3,000. Production capacity also grew, with expansions in Memmingen followed by new buildings in Munich, including the company’s current headquarters on Mühldorfstrasse near Munich’s eastern railway station, and in 1960 the Cologne service center was established. Upon receiving a large order from the German Postal Service in the late 1960s, the company built a branch plant for pre-production in Teisnach in the Bavarian Forest.

Continuing to Move Forward: Tubes, Transistors and Integrated Circuits

The much-vaunted Wirtschaftswunder transformed life in Germany in the 1950s and 1960s. The economic upswing was accompanied by technological innovations that also had an impact in the consumer segment: refrigerators, automobiles, better radios and — quickly taking root — television. In the electronics industry, the traditional tube was being replaced by the transistor. Rohde & Schwarz initially approached this development somewhat cautiously.

Experts still had no data to hand as to how long transistors would continue working at consistently high quality. Manufacturing high-precision measuring instruments with components that may begin to fail to meet quality standards after a few years posed a major risk. Around 1960, however, transistors gained acceptance even at Rohde & Schwarz and were installed in a variety of instruments. In 1961, for example, they were used in the CAQ frequency standard, the successor of the XSZ, which was still equipped with tubes.

The Munich-based electronics group was anything but cautious in its approach to the next electronics revolution: the integrated circuit. This invention ushered in the era of microelectronics. Computers began to appear in industry and in the service sector, and later also in the home. Between 1959 and 1967, for example, the number of data processing systems installed in Germany increased from 94 to 3,400.

As a user of this technology, Rohde & Schwarz installed its first computer system back in 1966. For a rental fee of 20,000 DM a month — the price of a Mercedes in those days — a computer with 4 KB of core memory processed the company’s payroll accounts. Rohde & Schwarz was also among the first to adopt development systems for microprocessor-controlled instruments. In 1974, the company was the second in Germany to install such a system, which carried serial number 100.

Initially used in measuring instruments only for setting their parameters and the digital output of measurements, microprocessors ultimately performed tasks in the actual processing of measurement values. In 1974, the SMPU from Rohde & Schwarz became the world’s first microprocessor-controlled radiocommunications tester. It combined the functions of various measuring instruments and was used in the production of radio equipment and RF modules. The SMPU made it easy to perform automatic measurements on radio equipment in the frequency range between 400 kHz and 1 GHz. It also offered interactive operation via a monitor and keyboard, which made switches, blinking lights and punch cards things of the past.

The instrument permitted unmanned round-the-clock operations. Also revolutionary was the use of an IEEE/IEC bus interface, permitting a connection with a desktop calculator or other peripheral devices. As of the mid-1970s, the IEEE/IEC bus interface had established itself as standard. Before that point, custom-designed circuits had to be produced for every combination of two or more measuring instruments. But it was not only the measuring equipment from Rohde & Schwarz that followed the computerization trend. In 1980, the ESM 500 family was launched: the world’s first radio surveillance receiver that had fully microprocessor-controlled functionality. It was a global sales success and won numerous international competitions.

Internationalization: Entering the European Market

The 1970s were a decisive decade for the strategic development of Rohde & Schwarz. In the post-war period, the company worked mainly for German governmental authorities: the postal administration, the armed forces, and public broadcasters. These authorities wrote specifications that precisely defined the desired functionality of the equipment they needed. The descriptions covered the minutest of details, right down to the positioning of the name plate.

Rohde & Schwarz was very successful in this line of business. However, many instruments could not be sold to other customers because of the highly customized nature of the designs. Moreover, as the 1960s had drawn to a close, change was in the air: German economic growth was slowing down, prices in the electrical industry were falling, the costs of labor and raw materials were rising, and public authorities were reducing their investments.

It was during this phase that Friedrich Schwarz, the son of Dr. Hermann Schwarz, joined the Executive Board. With his international experience, he mapped out important new directions for the company. He wanted the company to develop instruments that could be sold on the global market, and he succeeded in convincing the company’s founders and Rohde & Schwarz was restructured and organized by markets.

In addition, the company intensified its focus on developing its sales structures abroad, initially concentrating on Europe. The objective was to create stronger ties with the company representatives that had been operating abroad for years. Initial successes were recorded in only a few years, and in 1981/82, for the first time, more than 50 percent of the total revenue was earned abroad. In the following decades, the company gradually established its own sales and service network. Today, Rohde & Schwarz serves its customers at more than 70 locations around the world.

Precision and Innovation Through the Decades: Still a Recipe for Success Today

Strategic decisions alone certainly would not have yielded positive results. To succeed in the global market, the company had to generate a steady stream of new innovations. In the early 1980s, Rohde & Schwarz already had substantial market shares in the field of signal generators. For the most part, however, these instruments only reached 1 GHz, and digital modulators were not yet needed. A trend then began in which the market continually demanded higher frequencies and digital modulators.

In 1982, the company launched the SWP, the world’s first synthesized sweeper that combined a sweeper, synthesizer and calibration transmitter in a single instrument. It was followed in the late 1980s by the SMHU58 with vector modulation with a frequency range up to 1.95 GHz: the right instrument at the right time. It generated all of the complex modulation signals for GSM and PCN, the mobile communications systems that were still under development at that time.

After that, things happened fast: In the early 1990s, the SME established itself on the market as a special instrument for digital communications up to 6 GHz. The SMP combined in one box all features of a high-end analog instrument for up to 40 GHz. Plus, the SMIQ could, for the first time, be equipped with an optional fading simulator. As its successor, the high-end R&S SMU signal generator was introduced in 2003, the first two-path RF signal generator with a fading simulator. The current analog generators are unrivaled in terms of single-sideband (SSB) phase noise: the R&S SMF100A, rated for a frequency range up to 43.5 GHz, came to the fore in 2007.

Before the 1980s, the company was not present in the spectrum analysis market but in 1986, however, the FSA — the first spectrum analyzer produced by Rohde & Schwarz — catapulted the company to the global forefront in this segment. It set new standards in terms of dynamic range, precision, user-friendliness and documentation options. The instrument was also very easy to use owing to the first color display on the market.

With this 2 GHz instrument, Rohde & Schwarz gained a foothold in the large market for spectrum analyzers. It was followed in 1988 by the FSB (up to 5 GHz) and in 1990 by the FSM (up to 26.5 GHz). The company now has one of the broadest product portfolios on the market — from small, portable spectrum analyzers up to high-end signal analyzers. In 2007, the first spectrum analyzer was presented that was capable of a full span sweep up to 67 GHz: the R&S FSU67.

Since the early 1950s, when the Zg diagraph was launched, there has also been enormous change in the complex network analysis field. Particularly since the turn of the millennium, maximum frequency capabilities have increased a number of times. In 2005, Rohde & Schwarz introduced the world’s first eight-port network analyzer with a frequency range of 300 kHz to 8 GHz. For decades, two ports were always adequate for network analysis purposes. The rapid developments in mobile telephony and the relentless trend toward increased integration based on the smallest possible components led to a greater need for multiport measurements — a need to which the company has responded.

Next came the R&S ZVA40, with four-port architecture and a range up to 40 GHz. Then, in April 2008, the R&S ZVA50 was launched. Together with the mm-wave converters that the company has been introducing since 2007, the frequency range up to 325 GHz can be analyzed with T&M equipment from a single source. In addition, the instruments are highly versatile, opening the door to a number of potential applications. For example, multiport measurements up to 325 GHz can be carried out.

And finally, Rohde & Schwarz was always ahead of its time in voltage and power analysis. In the 1980s, the company launched the URV5 HF millivoltmeter and the NRV microwave power meter. These were the first-ever HF measuring instruments that used probes with an integrated calibration data memory, an innovation that became the market standard ten years later. This was followed in 1994 by the R&S NRT family, the first power meters whose probes also functioned as independent measuring instruments with digital interfaces. Today, the R&S NRP-Z81 wideband power sensor, which can be remote-controlled via USB, is the first such instrument to house the full functionality of a peak power analyzer in a compact sensor head. It is used for measuring radar and mobile telephony signals.

In Summary: Today’s Frontiers are Tomorrow's Standards

When Dr. Lothar Rohde and Dr. Hermann Schwarz produced their first measurement instrument in 1933, it reached 100 MHz in range. This figure placed the instrument at the forefront of the market. In those days, AM radio with frequencies in the kHz range was the most common application of electromagnetic waves. “Since then, the upper frequency range for consumer electronics has increased by a factor of ten every 20 years,” said Michael Hiebel, an engineer with Rohde & Schwarz and the author of the book Fundamentals of Vector Network Analysis. This curve is accurate in the mass market with high sales volumes. Examples include the mobile telephone boom at the start of the 1990s and the launch of automotive sensor radar, which will be assigned a frequency of 79 GHz by law in the EU as of 2011. If the trend continues, the 100 GHz limit will also soon be exceeded in mass market applications. Rohde & Schwarz already offers measurement technologies for these frequencies today.

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