Filter Tab (Flex Frame - Basic Mode)

The (Basic Mode) Filter configures the filters used by the VSA's Flex Frame feature.

Measurement Filter specifies the filter to apply to the time data before demodulation. You can select one of the pre-defined filters. The available Measurement Filter selections are:

You can also adjust the Alpha and Filter Length of the RC Radio Configuration: defines the physical channel configuration of cdma2000 (IS-2000) signals. Each RC specifies a set of data rates based on either 9.6 or 14.4 kbps. RC1 is the backwards-compatible mode of cdmaOne for 9.6 kbps voice traffic. It includes 9.6, 4.8, 2.4, 1.2 kbps data rates and operates at Spread Rate 1 (SR1). RC3 is a cdma2000 specific configuration based on 9.6 kbps that also supports 4.8, 2.7, and 1.5 kbps for voice, while supporting data at 19.2, 38.4, 76.8, and 153.6 kbps. RC3 also operates at SR1. For more information see Keysight application note "Performing cdma2000 Measurements Today"./RRC filter.

The filtered measurement time signal is shown in the IQ Meas Time trace.

See About Filters for more information.

Reference Filter specifies the filter to apply to the reference signal that is created based on the input signal. The reference filter chosen is usually a combination of the Measurement Filter and the pulse-shaping filter applied by the transmitter (for example, Measurement Filter = Raised Cosine and Reference Filter =Root-raised Cosine). The available Measurement Filter selections are:

You can also adjust the Alpha and Filter Length of the RC/RRC filter.

The filtered reference time signal is shown in the IQ Ref Time trace.

See About Filters for more information.

Alpha determines the filter characteristics of the filters used by Flex Frame. Alpha describes the shape of a Nyquist (cosine) filter. Alpha is also called the roll-off or the excess bandwidth factor. A higher value for alpha increases the bandwidth that is used in excess of the theoretical minimum.

Modulation theory states that the minimum bandwidth needed to transmit a signal is equal to the symbol rate. However, to realize this system would require a perfect brick-wall filter. This filter is equivalent to an alpha of 0. This would give the best possible spectral efficiency. Unfortunately, this filter is unrealizable.

In practice, radios typically use a filter alpha of about 0.3. This means that they take up 30% more bandwidth than the theoretical minimum.

Filter Length sets the length of the Measurement and Reference filters in number of symbols. The shorter the filter length, the more residual EVM Error 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. due to the truncation of the filter there will be in the measured EVM, but shorter filter lengths can reduce the cost of a DUT Device under Test: An acronym used to describe some type of electrical apparatus connected to test instrumentation. The apparatus can range from a single component to a complex subsystem such as a mobile phone, base station or MSC..