Aertech Industries

aka: TRW Microwave
aka: FEI Microwave
Brooke Clarke 2006 - 2015
Big Picture
Locations & Dates
    Tunnel Diode Amplifiers
    Tunnel Diode Detectors
    Transistor Amplifiers
        Schotky Diode Detectors
        Comb Generator
    Power Dividers
    Circulators & Isolators
    Polar Frequency Discriminators


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 (Wiki).  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.

Big Picture

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.

Company Names

Aertech was the beginning.
Later bought by TRW (TRW Microwave) in order to get control of the space qualified Tunnel Diode Amplifiers we were making 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.

Locations & Dates

When I joined (about 1963) Aertech was at 250 Polaris in Mountain View.
1967 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 stays 21847 the name changes to TRW Microwave.
__?__ Deguigne Dr. was another Aertech Building on the corner of Thompson Place.  Across Thompson was AMD.  At the end of Thompson was a helipad, but it was not used.
1987 FEI buys CAGE code 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 pollution 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 contamination with the down stream, if they are the same then it's not your building.  Driving around the block of Stewart you can count dozens of test wells Metal caps about half foot in diameter).


The initial products were based on Tunnel Diodes (Wiki) also called Esaki diodes.  They do not store charge (see: How diodes work & Testing Tunnel Diodes) The amplifier products which used diodes with peak currents over 1 ma and detectors which used diodes with peak currents under 1 ma.
Electrical Manufacturing Magazine,  February 1960, "The Esaki "Tunnel" Diode".
3110849 Tunnel Diode device, Theodore J Soltys, Gen Electric, Nov 12, 1963 - alloy and etch method i.e. make one at at time by hand, note the "neck (5 & 6) is very fragile.
patent 3110849 GE
          Tunnel Diode

Tunnel Diode Amplifiers

These typically had a lot of tuning screws, see for example the Aertech  TDA on the Wiki page for Tunnel Diodes.  The input has over 10 screws visible and probably as many on the bottom side.   The output has 5 on the top and I expect there's another 5 on the bottom.  In addition to the screws the center conductor of that transmission line came in various diameters and by adding or subtracting spacer blocks you can get other impedance transformations.  In addition you can tune the leg of the ferrite junction that feeds the amplifier using "U" shaped dielectrics that get glued into position.

T6654B Tunnel Diode Amplifier
                T6654B Tunnel Diode Amplifier
T7670B Tunnel Diode Amplifier
                T7670B Tunnel Diode Amplifier
Three Stage T6654B Tunnel Diode Amplifier Showing Signal Path
                  Stage T6654B Tunnel Diode Amplifier Showing Signal
Two Stage T7670B Tunnel Diode Amplifier Inside Showing Signal Path
Notice on the output stage that there are 3 spacer blocks between the 2
junction circulator and the tunnel diode housing.  They are "tuning" blocks.
The one nearest the circulator has Glyptal on it's tuning screw.
Two Stage
                  T7670B Tunnel Diode Amplifier Inside Showing Signal

The TD amplifier combines a TD operating in the negative resistance region with a matching circuit and a circulator to separate 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.

We sold some TDAs that had a built in "D" size Mercury battery and an on/off switch.  One came back many years later because the battery had run down, but the amplifier worked fine with a new battery.
TRW acquired Aertech to gain control of the space qualified TD amplifiers that they were buying from us.  We then also built space qualified hardware on Cost Plus Fixed Fee (CPFF) contracts.  On these contracts it was common to add as much cost as possible because you got  your profit on the total cost.  The means doing things like having  your own Scanning Electron Microscope (SEM) instead of contracting that out.

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 characteristics 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.
                  Detectors B-1                         B-2                                 B-3

Some of the above detectors have 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 tunnel 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


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 Telemetry

These amplifiers were made by Bob Mouw.  They were inter-digitated filters at each coupling stage.  There is a huge advantage in that any out of band intermodulation products are eliminated greatly improving the intercept point and rejecting out of band signals.  Both very important in receiver preamplifiers.  But, this also made it difficult to measure the noise figure.  That because the simple setup we used with the coupler and TD detector was a double sideband measurement so that you were measuring the NF at the LO + 30 MHz and the LO - 30 MHz.  So if you tested at the specified band edge one of those would be 30 MHz out of band and because of the steep skirts on the band pass filters the NF would look bad to a government inspector that was not microwave savvy.

L and S band telemetry were the two most common applications for this type of amplifier.

Bob liked to put a lot of tuning screws into his designs.  These had a number of them for each stage so you could "tune it up".
That means that none of them worked as assembled and all of them needed a lot of tuning.
Aertech A56105 Transistor
It's my hope that this is one of the Bob Mouw design units that has the interdigitated resonators.
Aertech A56105 Back side

The holes in the bottom were tapped and used to mount the various amplifier stages.  At the input and output there were "half filter" sections that just had one finger.  The amplifier stage has one input finger and one output finger.  So based on the hole pattern I'd say there's an input and output stage on the ends and 4 gain stages between them.

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.


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


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 this 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 cylindrical or a flat plate transmission lines) 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 (Wiki) and Varactor (Wiki) and Step Recovery (Wiki) 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 at 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 allowed 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.

The same model numbering system was carried over to the diodes.
A1Gnnn - Amplifier Tunnel
A1Ennn - Detector Tunnel
A2xnnn - Schottky
A4Snnn - Step Recovery
A5Snnn - PIN

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.
This is the product line I developed.


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 didn'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)


A simple microwave switch is just a diode to ground.  When back or zero biased the open diode lets the microwave signal go past, but when forward biased the diode reflects the signal keeping it from getting to the output.  If the diode has a short lifetime then the signal interacts with the bias, like in a limiter where a DC return is provided.  But if a diode with a lifetime that's long compared to the period of the signal then the signal does not change the bias and you have a switch.

Wide bandwidth switches require a series diode to isolate the off output arms.  For a microwave switch these need to be beam lead PIN diodes with very low series capacitance.

Narrow bandwidth switches can be made with all shunt PIN diodes by spacing the first shunt diode a 1/4 wavelength from the common junction.

Making a bias-T network that appears as an open over the full 0.1 to 18,000 MHz frequency range is far from trivial.

Schottky Diode Detectors

A Schottky diode (Wiki) 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.

The most common circuit consists of a microwave input matching circuit which may have the diode mounted at the far end with a stitched bonding wide to a bypass cap and on to the output.  The polarity can be reversed by mounting the diode on the output bypass capacitor.  The inductance of the bonding wire between the matching circuit and output capacitor is very important and so often was not a wire but rather a gold mesh and that was hand cut from a sheet and typically contained an odd number of strands so that the center strand could be bonded to the diode junction thus keeping the mesh on the centerline of the cylindrical module.


This was a logical outgrowth 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

Comb Generator

This was a cylindrical module containing a matching circuit to a step recovery diode (Wiki).
The input was something like a half watt signal at 100 MHz and the output would be a series of signals every 100 MHz, i.e. 100, 200, 300, 400, . . . . MHz.
Hence the name "Comb" generator because that's what it looked like on a spectrum analyzer.
Some HP spectrum analyzers have one of these built-in to provide a test signal at many frequencies.
Another way to use these is to use a filter (sometimes a tunable YIG filter) to select a specific frequency and use that frequency with a mixer to generate a new frequency or in a microwave counter, like the EIP counters.
A very special comb generator was used in the HP Large Signal Network Analyzer (Non Linear network analyzer) as a calibration test signal.
6812714 Apparatus for collecting signal measurement data at signal ports of an RF and microwave device-under-test, under different impedance load conditions, Agilent

See my Diodes web page under SRD for more information.

Power Dividers

These were Wilkinson type (1/4 wave lines) (Wiki) and were narrow band.  The main frequency range was 2.2 - 2.3 Ghz to support the then new unified S-band telemetry (Wiki).  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.
Aertech M3201
                Power Divider Aertech M5202
                Power Divider
M3201 Power Divider
500 to 1000 MHz
M5202 Power Divider
2.2 to 2.3 GHz (S-band telemetry)

Circulators (Wiki) & Isolators (Wiki)

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.

Note:  A circulator has 3 connectors and an isolator has 2 connectors and a built-in termination.


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, VT (SMAf)
TRW (Aertech, FEI
        Micorwave) Source S2704

Polar Frequency Discriminators (aka Instantaneous Frequency Monitor)

Aertech PD4018 Polar Frequency Discriminators PFD
                  Instantaneous Frequency Monitor IFM

2 to 4 GHz input at bottom center.
Output DC coupled signals on the 4 detectors.
If all the detectors have zero to positive outputs (or zero to negative putputs
then the X pair and the Y pair will go into differential inputs so that the combined X (and combined Y) channels
will be bipolar.  That way when fed into the X and Y inputs to an oscilloscope you will see a circle when a sweep from 2 to 4 GHz is the input.  The radius of the circle is the power and the angle of the spot is the frequency.  In the actual system the differential amps would feed very fast A/D converters.
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.

3015776 Indicating fluctuations in frequency and amplitude, Feb 9, 1957 - used with phonograph records
3061780 Polar displayer, Jr Chester B Watts, Alford Andrew, Mar 19, 1956
3083336 Direct reading, 360 degree phase meter, Poirier Jules Hubert, Ryan Aeronautical Co, Jul 12, 1960,
3135917 Frequency sensitive wave analyzer including frequency sensing phase shifting means, Ethridge C Best, Martin R Richmond, Sanders Associates Inc, Sep 11, 1961
3395346 Phase and instantaneous frequency discriminator, Kincheloe William R, Wilkens Mark W, Research Corp, Mar 24, 1965,
3518541 Digital Phase Measuring Set, Jun 1970
3568067 Frequency Discriminator with Output Indicitive of Difference Between Input and Local Reference Signals, Collins, Mar 1971
3956706 Miniaturized millimeter wave instantaneous frequency discriminator, David L. Saul, US Navy, May 11, 1976
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 mathematical 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 ides is to make the dual circuit of the ring double balanced mixer.

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.

"Broadband Double Balanced Mixer/Modulators" by R. B. Mouw and S. M. Fukuchi,
 published in the Microwave Journal, pages 133-134, March 1969.

Steve Fukuchi worked with bob on the mixer line.

R. B. Mouw et al, "Broadband Double Balanced Mixer/Modulators", Mar. 1969, Microwave Journal, Part I, 4 pages.
R. B. Mouw et al, "Broadband Double Balanced Mixer/Modulators", Microwave Journal, 6 pages, Part II.
R. B. Mouw et al, Broadband Double Balanced Mixer/Modulators , Mar. 1969, Microwave Journal, Part I, 4 pages.
R. B. Mouw et al, Broadband Double Balanced Mixer/Modulators , Microwave Journal, 6 pages, Part II.

    Issued/ Filed: May 12, 1970 / Oct. 18, 1967 455/326; 333/24R; 455/331 - Is the first version of the Mouw mixer pattern 
    Note: the coax lines have had their center conductor heated and pulled out and replaced with a new centerconductor of smaller diameter
     (i.e. the 50 Ohm line is transformed into a higher impedance line).

3818385 Hybrid junction and mixer or modulator, R.B. Mouw, Jun 18, 1974, 333/26, 333/243, 455/326, 333/238, 333/35

3512090 5 /1970
    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
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 machinist at Aertech (1964)

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

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Page created: 8 Nov 2006.