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Fader IS-136 TDMA Channel Simulator

The Fader/Simulator™ system consists of 6 or more IS-136 TDMA channels, each individually controlled by an external (host) PC. For each TDMA channel, the data content, RIF amplitudE and carrier frequency can be independently set on any 30 kHz ass gnment in the PCS 1900 band. In addition, each channel can be programmed to produce signal amplitude variations (fading) up to ±16 dB of its output level using preprogrammed algorithms such as Raleigh fading or other models at rates up to an equivalent vehicle speed of 100 MPH.

The data parameters of each channel along with its associated RIF level can be set to any required level. The "peak to valley" difference between any output can be as large as 40 dB. Individual channel amplitude output levels are regulated to within ±2dB. Each channel is brought to the front panel via an N connector, and the combined channel RF amplitude has an output dynamic range of greater than 80 dB, from -35 dBrn to -115 dBm.

Each data channel has a 128K words of battery-backed memory used to hold formatted, IS-136 data. In a typical operation, formatted data such as base station control channel data (BCCH) is downloaded from a host PC through the RS-232 serial port to any channel. Up to 16 hyperframes of data can be stored for each channel in the simulator.

Upon transmission, 12 primary hyperframes in each channel of the simulator transmit continuously from these circulating buffers. The output of this SRAM memory is clocked into a parallel-to-serial register and fed to the RF modulator. Data for the I channel and Q channel are appropriately applied to the inputs of base band filters. The outputs are then converted to analog I and Q signals and fed to the RIF modulator.

Upon complete transmission of each primary hyperframe, the system checks the contents of an auxiliary, 4 hyperframe buffer. If any data has been deposited into these buffers, this data is next transmitted by the simulator. These auxiliary buffers are included in the system to provide for asynchronous insertion of data, such as to "seed" the bit stream with special messages or deliberate bit errors for testing forward error correction. Once the auxiliary buffer(s) has been transmitted, the system returns to normal (route) output of the primary data buffers.

Each buffer and channel may be independently enabled or disabled, as well as set to any channel frequency in 30 kHz steps within the 1900 MHz PCS band. The RF output level and amplitude variations are controlled via programmable registers which, in turn, control precision digital attenuators. The rate of amplitude variations and depth of amplitude changes are also programmable from the host PC.

Download Fader data sheet

• Multi-channel RF modulated signals for GSM or IS- 136 formats
• 6-channel increments
• Independent wideband synthesized RF signal sources
• Range from 1.85 to 2.10 GHz at amplitudes from -30 to -120 dBm

RF PERFORMANCE

Frequency stability	+2ppm from 10 to 50 degrees C
Frequency steps	+30 kHz
Frequency range	1930 MHz to 1970 MHz
RF amplitude	-30 dBm to - 110 dBm +2dB into 50

DIGITAL SPECIFICATIONS

	IS-136	GSM
Data Rate	48,600	270,800
Modulation	pi/4 DPSK	GMSK
Frame length, bits	1944	1250
Size of the memory buffer in each channel	16 hyperframes	1 superframe = 51*26-multiframes

HOST PC SERIAL INTERFACE

Serial port	RS-232C
Format	8 data bits
Parity	None
Start/stop bits	One

MECHANICAL

Housing	19" rack mounted unit
Height	Approximately 24"
Depth	Approximately 16"

POWER

AC power	110 Vac, 60 Hertz at 5 amperes
Supply	Switching power supply +5, +12 Vdc

• PCS 1930-1970 MHz