The Spacing Circle in double stub matching

In double stub matching the two stubs are spaced a predetermined distance away from each other. These distances are typically λ/8, λ/4, 3λ/8, 5λ/8 etc. Knowing what we know about a length of line acting as a transformer, we know that the length of line between the two stubs acts as a transformer. The action of this transformer is to convert the admittance at the position of stub 2 to a different admittance at the position of stub 1. So we start from the position of stub 2.

In order that stub 2 can be finally used to match the line admittance, the real part of the admittance at the position of stub 2, on the line, has to be 1.0 (normalized value). Its susceptance is then jB. jB is the susceptance that is cancelled using stub 2 to ultimately get the matching to the line admittance. The admittance at the position of stub 2, (without the stub) lies on the constant conductance, g = 1 circle. The admittances on the g = 1 circle are all the possible admittances at the stub 2 position for a match to take place.

To reiterate, as a result of these deliberations, that some point of the VSWR circle formed by the position of stub 2, must intersect the g=1 or the unity conductance circle on the Smith Chart.

We also conclude, that the admittance at the position of the first stub, must lie on

a circle of equal radius but having its center rotated (moved to or displaced) by the spacing between the stubs towards the load. Lets call this spacing ‘d’.

This circle is called the spacing circle.

Please visit our website for more articles of interest.

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