The mapping between the symbol constellation points for various values of I and Q is described by a set of waveforms. In QPSK there are 4 symbols, labeled 11, 01, 10, 00. So each symbol conveys two bits. These symbols may be coded in a number of ways. A set of graphical displays show one way of doing this. The symbols themselves are also composed of waveforms with differing phases. These waveforms are used to build the composite QPSK signal. This document should be read in conjunction with an earlier brief paper on QPSK. (http://www.signalpro.biz/wordpress/?p=707)

This paper is an attempt to explain how the last line of the graphical QPSK signal waveform was constructed. In that construct two cycles of each symbol waveform were used. Note that negative values are simply drawn by inverting the symbol waveform.

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**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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**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

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Supply current Supply = 5.0V, 23.0 mA

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