Half Sine Filter (Digital Demod)

Menu Path: MeasSetup > Digital Demod Properties > Filter tab > Reference Filter

The Half Sine filter is used for ZigBee 2450 MHz measurements. The Half Sine pulse shaping filter changes the vector diagram of an OQPSKOffset Quadrature Phase Shift Keying: A type of QPSKQuadrature phase shift keying modulation that offsets the bit streams on the I and Q channels by a half bit. This reduces amplitude fluctuations and helps improve spectral efficiency. signal from a square to a circle. This eliminates any amplitude variations and turns the OQPSK signal into a constant envelope modulation. The OQPSK now resembles MSKMinimum Shift Keying.

The equation for the Half Sine filter follows. (Tc is equal to the delay between the I and Q portions of the signal. The symbol period is 2Tc.)

The Half Sine filter is a standard reference filter in Option AYA.

When this filter is selected for OQPSK, the reference constellation points fall on a circle with a magnitude of sqrt(2)/2, but the EVMError vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format. is still expressed as a percentage of the magnitude of a QPSK symbol point (magnitude = 1). See EVM for more information.

See Also

ZigBee Standard (IEEE802.15.4) (Digital Demod)

About Filters (Digital Demod)