Equalizer design experiences

About two and half years ago we started a program for the design and development of wireline equalizers, both fixed and adaptive. Our first designs will be going into fabrication this month. This post is an attempt to document some issues and challenges we faced on this project.

1) Data and models of cables: Immediately it was obvious that there is a big hole in the data for cables. Our designs were for 5 Ghz and 1.65 Ghz. We found almost no data on the characteristics of cables for these frequencies. After a little research it turned out that we would have to do our own modeling using a TDR and Simulink/MATLAB and a few home grown tools. This is not an inexpensive activity. The boards required as interfaces to the machine cost about $10k a piece! The TDR is also a very expensive machine. We tried searching the web but found little available data. Manufacturers of the cables do publish data but it turned out that it was the wrong kind of data for our purposes. So cable characteristics are difficult to get.

2) Design tools: The second challenge was, the design tools available for design of ICs are, in our opinion not terribly useful when designing equalizers. Long sequences of really high frequency data are needed to check performance. These types of simulations can really run extremely slow and simulating a complete chip was almost impossible. A combination of SIMULINK and SPICE type simulators ( including Agilent ADS) were used but in our opinion left quite a bit to be desired. Equalizer designers beware!

3) IC process data: The fabrication houses that we selected ( “world class”) provided very good data on their processes. Again this data was good for about 80% of the design but 20% of the design could not be covered by the given data.

4) ESD protection: This is a problem for high frequency equalizer design in particular and in general a good ESD structure is difficult to do. The issue is this: If we use the characterized ESD cells then we have a challenge because of the parasitics. If we make our own ESD cells then we have no characterization data. So I suppose this makes ESD a major challenge in these types of devices. Remembering that the input lines actually come in from outside. ( Existing TVS devices are woefully inadequate for ESD.)

5) Test: The challenge of testing the equalizers looms large of course. A combination of standard lab equipment ( expensive) and custom made equipment is perhaps the best approach. Again the making of the test equipment is a challenge in itself as we found.

6) Demo boards: A real challenge. We had to go through a number of iterations with both PCB vendors and designs. The first PCB we did gave a clear impedance step at 150 Mhz and really caused errors in the measurements. Subsequent designs were great improvements but we still need more improvement and are working on it.

So the design and development of these wireline equalizers is, in our opinion not a “walk in the park” Good luck to all the equalizer designers and many congratulations to the successful ones. You guys have really licked the problems!

SPG designs, develops and delivers custom analog and RF/wireless asics and modules.

FPGA Design and development service

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A wideand RF detector ( 40 Mhz to 3 Ghz) -75 dBm to 5 dBm input

A wideband RF detector

A wideband RF detector

Linear detector performance

Linear detector performance curves

A wideband linear RF detector

Price for one unit: $25.00. Lead time for delivery 3 days. 30 Day return policy. Pricing for 100 units or more: $20.00 per unit.  Please contact Signal Processing Group Inc. for details for purchase from Signal Processing Group Inc. Email: spg@signalpro.biz 24/7

Wideband RF detector perforamce , more details

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2 stage 35 dB gain RF amplifier. Front of the module

Full range frequency response

2 stage amplifier deta

Please see details at http://www.signalpro.biz/2rf_amplifier_details.htm    Delivery lead time is 3 days. Return within 30 days for a full refund. Price is $15.00 for one unit and $10.00 per unit in volumes of 100. For higher volumes than 100 please contact Signal Processing group Inc.

miniature LNA module

Mni LNA performance

Delivery lead time is 3 days. Return within 30 days for a full refund. Price is $15.00 for one unit and $12.00 per unit in volumes of 100. For higher volumes than 100 please contact Signal Processing Group Inc. at email: spg@signalpro.biz or call 602-626-0272 for fastest service.

A high frequency divider from 500 Mhz to % Ghz+

The input interface.
The frequency divider has a differential analog interface. The following parameters apply:
The minimum frequency that can be input is 500 Mhz and the maximum frequency is 6.0 Ghz.
The RF input level is 5 dBm to – 5 dBm. For lower frequencies make sure that the slew rate is
greater than 560 V/us. The input is biased by two 500 Ohm resistors connected to a 1.6V DC bias.
Therefore AC coupling is used at the input. These are two 100pF capacitors.
The output interface.
The output is single ended. The output driver is capable of sourcing and sinking 24 mA. The
equivalent output impedance is 50 Ohm. To avoid reflections it is recommended that the divider
work into a 50 Ohm load.
General operation.
The inputs are applied to the input SMA I/O. The product will work with both a differential input as
well as a single ended input. However, a differential input works best. The division ratio is applied
to the N1 and N2 control inputs as follows:
N2 N1 Division ratio
0 0 8
0 1 16
1 0 32
1 1 64
The logic levels are:
Logic level Voltage
1 1.4V minimum
0 0.6V maximum
The supply voltage interface.
The operating supply voltage is 3.3V typical. The quiescent (DC) operating supply current is 2 mA.

A high frequency divider 500 Mhz to 5 Ghz+

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SPDT DC to 3 Ghz RF switch

DC to 3 Ghz RF SPDT switch

RF Switch typical features

Supply voltage = Vcc = 0/+5 Vdc
Operatng temperature = TA = -50° C to 125 Deg C
Operating impedance = 50 Ohm
Input power for 1 dB
compression ( 5.0V system) = 37 dBm ( f = 0.5 to 3 Ghz)
Input third order Intercept = 64 dBm ( 0 to 5.0V system, f = 0.5 to 3 Ghz)
Operating frequency range = DC to 3 Ghz.
Insertion loss DC to 3 Ghz = 0.8 dB
Isolation DC to 3 Ghz = 14 dB minimum
Return loss DC to 3 Ghz = 20 dB
50% contl to 10/90 %
( ON/OFF) = 120 ns

A single stage RF amplifier as a gain block

A single stage RF amplifier summary specifications

Summary Specifications

Gain,  Operating: 19.5 dB
Operating frequency range: 1.0 – 2700 Mhz
OIP3: (Pout = 19.0 dBm),  -8.5 dBm
P1dB: 4.6 dBm
N.F: 4.2 dB
Supply voltage Operating: 3.3  – 5.5 Volts

Price: single unit $7.50, 100 units : $5:50.

Free delivery, shipping lead time 2 days.

30 day return policy, buyer ships.
Supply current Supply = 5.0V,  23.0 mA

Embedded design and development

Signal Processing Group Inc. is offering embedded design and development using Microchip processors. Please contact us on spg@signalpro.biz for more information

Practical impedance matching

Three useful blocks

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