Aertech Industries

© Brooke Clarke 2006 - 2010

Aertech was founded by Fred Schumacher and Harold Harrison in the late 1950s or early 1960s.  A couple of their early products were based on the then newly invented Tunnel Diode.  One was a Tunnel Diode Detector and the other was a Tunnel Diode Amplifier.  Most of Aertech's products were in the 1 to 18 GHz frequency range but there were a few both below and above that range.

Note that Tunnel Diodes were then all hand made one at a time and typically came in "Top Hat" ceramic pill packages.

I worked here from the mid 1960s to the late 1980s.

The Secret History of Silicon Valley (56 minutes) Google Tech Talks, Dec 18 2007 by  Steve Blank
Aertech got it's start in Tunnel Diode products by making components for someone at Stanford who was writing a paper on them.

Aertech was the beginning.
Later bought by TRW (TRW Microwave) in order to get control of the space qualified Tunnel Diode Amplifiers we were manking for them.
Later bought by FEI (FEI Microwave)
Later part sold to ST Microwave and the rest closed down at the end of the cold war.
The Commercial And Government Entity (CAGE) code stayed 21847.

When I joined (about 1963) Aertech was at 250 Polaris in Mountain View.
196? Aertech moves to 815 Stewart in Sunnyvale (or 825 then 815?)
1968 Aertech at 825 Stewart in Sunnyvale
1984 TRW buys Aertech and even though the FSCM number starys 21847 the name changes to TRW Microwave.
__?__ Deguigne Dr. was another Aertech Building on the corner of Thompson Place.  Across Thompson was AMD.
1987 FEI buys 21847 and the name becomes FEI Microwave
1992 (?) most people are laid off and part of Aertech moves to ST Microwave.
EPA Region 9 Super Fund sites - 825  Note that it's very difficult to tell what building is causing polution since the ground water moves it.  The only way is to have test wells on at least 4 sides of a building and compare the upstream contanimation with the down stream, if they are the same then it's not your building.  Driving around the block of Stweart you can count dozens of test wells.

Tunnel Diode Amplifiers

T6654B Tunnel Diode Amplifier	T7670B Tunnel Diode Amplifier
Three Stage T6654B Tunnel Diode Amplifier Showing Signal Path	Two Stage T7670B Tunnel Diode Amplifier Inside Showing Signal Path

The TD amplifier combines a TD operating in the negative resistance region with a matching circuit and a circulator to seperate the incident and reflected waves.  Since the isolation of a single junction circulator is around 20 dB the gain of each stage needs to be less than that to prevent oscillations. 
 
These amplifiers have two very important properties for space applications.  First the bias voltage and current are both quite low so the power consumption is also very small.  The Tunnel Diodes are heavily doped and so are not effected by radiation.
 
  TRW acquired Aertch to gain control of the space qualified TD amplifiers that they were buying from us.

Tunnel Diode Detectors

The Tunnel Diode Detector was one of the first products made at Aertech.

 TD detectors, or more properly called Back Diode detectors use the diode without any bias.  The diode characteristisc are such that the impedance is near 50 Ohms and so is not only a good match to the RF but also to the video output.  This is very important when detecting pulses since the video bandwidth of the TD detector is much wider than of a crystal detector.  Because of this TD detectors are very useful in RADAR countermeasures receivers.

B-1                         B-2                                 B-3 Detector/Mixer

Some of the above detectors has bulges and discoloration, so maybe these came from a dead group.
3693103 Wideband Detector for use in Coaxial Transmission Lines, R.B. Mouw, Sep 19 1972 - replaceable diode (maybe not tunnel diode?)

Detector p/n Prefix Letters

D - Detector
DT - Detector with TNC input
DB - Detector with BNC input
DM - Detector in Miniature configuration (SMA connector input)
DMM - Detector is sub Miniature configuration (SMA connector input)
DO & DOM Detector 3mm input & output

We used tunned diode detectors (type-N input) mounted on Narda couplers as mixers for Noise Measurements.  AIL tube type amplifiers fed the HP 340 NF meter.  Mostly used the HP noise source with a type-N output but sometimes used a hot-cold noise source that required liquid Nitrogen.

Transistor Amplifiers

UHF

The VHF - UHF amplifiers made by Tom Olson (Olsen Technology)using lumped elements mounted on a solid copper clad fiberglass board (not etched).  The parts were held in place by drilling a hole though the board and inserting a Teflon standoff (some with just a post and others that were feed through).

L (1435 - 1540 MHz) & S (2200 - 2300 MHz) Band Ttelemetry

These amplifiers were made by Bob Mouw.  They were inter-digitated filters at each coupling stage.

	It's my hope that this is one of the Bob Mouw design units that has the interdigitated resonators.

Wide Band

These were designed by using S-Parameters after the HP 8410A was introduced.  There was a company that had an automated 8410 system and would test transistors and supply us with the S-Parameters.  The first generation microwave transistors were Germanium and made by TI.

We built a transistor tester based on the GE Transistor Manual and used it to measure the DC parameters of the transistors and correlated these with the RF performance.  Once that was done it was possible to buy a batch of the same p/n with the proviso that TI would not have culled the better transistors.  This saved a lot of money since buying tested transistors was expensive.

Taming the out of band gain was required to prevent oscillations.

Semiconductors

For the first few years all the semiconductors were purchased from outside vendors and were typically in small cylindrical ceramic packages.

Diodes

The first diodes that we made were Tunnel diodes for amplifiers and back diodes for detectors.  This was a manual one at a time process, i.e. not using wafers or masking.  Since Tunnel diodes are highly doped there is no need for a clean room, i.e. it was more like a dirty room.

It's difficult to test tunnel diodes because between the voltage where the peak and valley are located the diode exhibits negative resistance.  In the region the diode will oscillate.  To prevent oscillation the diode needs to see a real resistance that's lower than it's negative resistance, something that's very difficult to do over a frequency range that covers DC to 60 GHz.  The way we did it was to use a transmission line that was loaded with lossy material (either cylindircal or a flat plate) and terminated with a fixed resistor.  A bridge circuit can be used to eliminate the fixed resistor from the measurement allowing the true I-V curve to be seen on a Tek 567 Curve Tracer.

The next stage was to make Schottky diodes for use in detectors and mixers, then PIN and Varactor diodes were added.  These were made on 2" diameter wafers which at that time were obsolete for digital ICs and so the equipment was available for low cost.  Since we were dicing the wafer into chips that were 0.015" x 0.015" the yield per wafer was on the order of 10,000 chips/wafer there was no motivation to move to larger wafers.  The need for a  clean room may have been the main motivation to move from Mountain View to Sunnyvale.  Sunnyvale was the first city to have a building code that allowed for both office space and hazardous materials in the same building (code section H6).

The first clean room was located in the center of the building with windows.  This allowed the exhaust clean air to bleed into the dirty surrounding space.  It also alowed a factory tour where you could see most of the fab without putting on a clean suit.  A big problem with this arrangement is that you need to move hazardous material through the office/work areas.  Which is not good if there's a spill.

Module Products

These were made using raw semiconductor chips in packages with hermetic glass to metal seals that had a nominal impedance of 50 Ohms.

Limiters

If glass packaged diodes are used the inductance of the lead wires limits the upper frequency to below microwave frequencies. This was my first attempt to make a limiter and it did't work.  In order to work with microwave signals raw diode chips need to be used. 

By placing a couple of fast PIN diodes across a transmission line you can get a circuit that passes low power levels but that reflects high power levels.  These have an internal DC return (the A9L100 series). 

In order to use raw chips a new packaging technology was needed.  At this time HP had a series of microwave components that were packaged in a cylindrical package and was sealed by welding the ends.  This was both an expensive and difficult to use package.  I came up with a similar package which had a protruding lip instead of the recessed shoulder that was on the HP package making it much easier to integrate into a final housing.  I also used a solder seal instead of the weld used by HP.  This is both lower cost, lower temperature but also allows repairing a module.

I think Fred and Harold setup a local company to make the glass to metal seals and to weld them to the central part of the modules.

A later limiter topology used a shunt PIN diode and an opposite polarity Schottky diode, with DC blocking caps on each end.  (The A9L200 series)

Schottky Diode Detectors

A Schotky diode detector needs to have a DC bias applied to get the diode impedance down to the design value which may be a few hundred Ohms.  A matching circuit is used to get a good VSWR in a 50 Ohm circuit.
The module type (where a raw Schottky diode is used) are the A9D--- part numbers.

Limiter-Detectors

This was a logical outgrouth of having both limiters and detectors in the cylindrical package.  The first ones were made by putting a limiter module and a detector module into a long cylindrical package.  The production units were made using a single long module.
Also see:
Radar Warning Receivers
AM-6536 / ALR-54 Radar Warning Receiver Front-end

Power Dividers

These were Wilkinson type (1/4 wave lines) and were narrow band.  The main frequency range was 2.2 - 2.3 Ghz to support the then new unified S-band telemetry.  There were a number of designs with 2, 4 or 8 outputs and with various connectors like SMA, TNC, Type-N.

There is a resistor across the output ports that's located a quarter wave from the "Y" junction.  If a signal is fed into OUT1 and IN is terminated with 50 Ohms then the resistor is across a half wave path and so OUT2 sees isolation.  For a signal fed into IN the resistor is at the same potential on the OUT1 and OUT2 paths and so contributes no loss, i.e. the insertion loss would be a fraction of a dB higher than 3 dB.

M3201 Power Divider 500 to 1000 MHz	M5202 Power Divider 2.2 to 2.3 GHz (S-band telemetry)

Circulators & Isolators

At some point the design and manufacture of circulators and isolators was brought in house.  Prior to that an outside captive company made the circulators and isolators used in the Tunnel Diode Amplifiers.  The electrical specs are very tightly coupled.  For example if you tune the unit for very good return loss at some frequency the isolation will be very good at that frequency and to a lesser extent so will the insertion loss.

Sources

Don't remember much about these.  Found unit on eBay.
Marked VCXO Amplifier
Model: S2704
Serial: 0297
QA Stamp date: 6-26-84
Connectors (left to right): RF OUT (SMAf), -12V, Gnd, +15V, V_T (SMAf)

Polar Frequency Discriminators (aka Instantaneous Frequency Monitor)

These were strip-line components that typically had four microwave detectors as the outputs.  A number of them could be cascaded where the delay line length causes them to work like a gas meter so each added unit provided finer resolution.  They worked great on pulsed signals, but had a problem with CW signals.
Bill Rocko (spelling?) developed the product line.
3518541 Digital Phase Measuring Set, Jun 1970
3568067 Frequency Discriminator with Output Indicitive of Difference Between Input and Local Reference Signals, Collins, Mar 1971
4144491 Frequency measuring apparatus, Raytheon, Mar 13, 1979
4414505 Microwave instantaneous frequency measurement apparatus, Nov 8, 1983

Bob Mouw was the first person to make a double balanced mixer that worked at microwave frequencies.  Prior to his invention double balanced mixers were made using a couple of ferrite balun transformers and a "ring" connected diode quad.  Their upper frequency limit was around 2 GHz.  Bob took the classical circuit and made a "dual" that used a "star" diode quad and hybrid coaxial transmission line transformers.  I helped do the mathimatical analysis for this mixer.  You can consider the diodes as switches that are turned on and off by the Local Oscillator.  The two states either pass the input signal or invert the input signal.  Doing an FFT on the waveform gives all the frequency domain outputs of a mixer, less those that are cancelled due to the mixer balance.

The mixer equation is:
IF = +/- m * RF +/- n * LO
given a desired RF frequency and an LO frequency there are many IF frequencies generated.
Orin Gobby (spelling?) was a expert when it came to receiver design.  Choosing the LO frequency to minimize spurious signals is as much an art as a science.

Semiconductor mixer performance has a limit to how large a signal can be handled.  WJ wrote some app notes trying to get at the cause.  The answer can be found on my microwave diodes web page.

3512090 5 /1970 HYBRID JUNCTIONS AND MIXERS AND MODULATORS CONSTRUCTED THEREFROM
    Issued/ Filed: May 12, 1970 / Oct. 18, 1967 455/326; 333/24R; 455/331 - Is the first version of the Mouw mixer pattern 


    The diodes shown on the first page are in glass packages.  Later there were much more advanced versions built.  These typically were made in octave bandwidths.

3818385 06/18/1974 HYBRID JUNCTION AND MIXER OR MODULATOR 333/26; 333/35; 333/238; 333/243; 455/326

• Mouw-"Broad Band Hybrid Junction & Application to the Star Modulator" Nov. 68, IEEE-Transactions on Microwave Theory & Tech. Vol. MTT-16, No. 11.
• "Compensated-Balun;" Oltman, March 66; IEEE-Transactions on Microwave Theory & Techniques pp. 112-119.

3638126 01/25/1972 HIGH-FREQUENCY CONVERTER - Bob later worked for Spacek

Microwave detector measurements on an HP 423A, an AEL-I-501 and an aertech tunnel diode detector, John Slonski, Stanford Electronics Laboratory

Past Projects
Understanding Diodes & RF/Microwave Operation
Microwave Test Equipment - Miscellaneous

HP-IB Controllers

Herotec Inc - founded by Cheng Lai - makes microwave components
Metelics - founded by Rudy Dorilag - makes microwave semiconductors
ST Microwave - acquired some of FEI Microwave when the cold war ended
Trimetric Engineering - Mike Butler the first R&D machinest at Aertech (1964)

There were many other companies that spun out from Aertech/TRW Microwave/FEI Microwave.  Let me know their names.