# A FIR compensation design using the OCTAVE tool.

A compensation filter for a CIC filter was required. We chose to use the free software tool OCTAVE to help us do this. Here is the sequence of tasks that were done. (Be aware that a compensation filter filter design is not trivial unless you have been doing it for a long while. )

1.0) Design the CIC filter. 2) Measure the droop of the filter . (3) Use the inverse response of the CIC filter to synthesize the compensation filter. (4) Use the frequency response of the inverse filter to generate a frequency – magnitude table. ( Much like a piecewise linear SPICE signal). This table consists of frequency – magnitude pairs for the compensation filter you want. (5) Use this table as the input to the function fir2(n,f,m) in Octave. This function provides the coefficients of the filter you need. However, the trick is to choose the right “n”; It took us a while to get the value of n right for our purposes. You will have to choose yours however you wish. (6) Run fir2 and take the results ( say “b[]”) and generate the impulse response of the filter from it using another OCTAVE function called impz(). The input argument is the “b[]” you just got from fir2. Once you have the impulse response use the freqz function in Octave to simulate the filter you just designed. Once you have the frequency magnitude characteristic of the new filter you can do a multiplot using the plot function from OCTAVE. This allows you to compare the two filters. i.e. the filter you wanted and the filter you designed.

You can make adjustments by using multiple runs of the above sequence until you get the best filter you can get, An example of the multiplot is shown below. The blue line is the original filter and the orange line is the one we got from using the sequence quoted above. Please visit the Signal Processing Group Inc website for more info and contact information.

#### 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

#### 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

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#### 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.

#### Mni LNA performance

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#### 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.

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#### 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 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