When two parallel, closely spaced, microstrip lines are used to deliver a differential signal to a load, the differential impedance between them can be calculated using a closed form expression. This impedance is not the characteristic impedance of the individual lines. The differential impedance is modified by the proximity of the two lines to each other. A calculator has been developed by Signal Processing Group Inc., to do this using javascript.

The input to the program is:

1) Characteristic impedance of the lines – Zo

2) The thickness of the PCB – h

3) The spacing of the lines on the PCB—s

It is recommended that when adjusting the dimensions of the lines to get the required differential impedance ( Zdiff) the width of the lines be adjusted, not the spacing.

Another javascript provides a calculator to do this adjustment. This calculator requires the following inputs:

4) ε_{r }the dielectric constant of the substrate

5) t, the thickness of copper

6) W, the width of the strip

7) h, the thickness of the substrate.

The javascripts are interactive and these constants can be inserted as it runs. Both the scripts can be accessed from the SPG website by interested users.under the complementary menu i

Here are some design rules for the use of differential microstrip lines.

*Design Rule 1** The traces should be of equal length*.

*Design Rule 2***:** *Route differential traces close together*.

*Design Rule 3**: Differential impedance calculations are necessary with differential signals and traces**.*

*Design Rule 4:** *T*he separation between the two traces (of the differential pair) must remain constant over the entire length.*

Check out this impedance matching book available from Amazon.

Contact SPG using phone: 602-626-0272 for fast service.

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

Please contact Signal Processing Group Inc. on email: spg@signalpro.biz . We will answer within 24 hours.

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.

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.

**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.

Please contact Signal Processing Group Inc. at email: spg@signalpro.biz or telephone 602-626-0272. Get a response within minutes or worst case 24 hours if contact is by email.

**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

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

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