Means for Det Stab Suppres of Spur Rad and Limiting Power

FCC ID: OIIDTSA1900-2

Operational Description

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FCCID_37310

Omnipoint Technologies, Inc. Exhibit 6 FCC ID: OIIDTSA1900-2 Page 1 of 3 EXHIBIT 6 MEANS FOR DETERMINING AND STABILIZING FREQUENCY, SUPPRESSION OF SPURIOUS RADIATION, LIMITING MODULATION, AND LIMITING POWER As required by § 2.1033(c)(10), this Exhibit details the methods employed within the DTSA transmitter to determine and stabilize frequency, suppress spurious radiation and to limit both modulation and power Means for Determining and Stabilizing Frequency No absolute frequency stability requirements are levied against broadband PCS equipment operating under the authority of Part 24, Subpart J. However, per § 24.235, the frequency stability of the DTSA shall be sufficient to ensure that the fundamental emission stays within the authorized frequency block. Specifically, this is accomplished as follows: The transmit RF carrier of the DTSA is generated by a voltage controlled oscillator (VCO) which is phase locked to a 13 MHz master reference source. This 13 MHz source is synchronized to the GSM network and, within the DTSA, is controlled by an 11 bit DAC to keep the carrier to within ±0.1 ppm of the network reference. Measurements of the stability of the fundamental emission of the DTSA, over variations in temperature and input voltage, are presented in Exhibit 14. As a GSM-compliant terminal, the stability of the DTSA carrier is to within 0.1 ppm of the received frequency from a base station, in accordance with GSM performance requirements (see J-STD-007, Personal Communications Services, Air Interface Specification; Volume 1, Radio Path Physical Layer, Section 7.4.1). Means for Suppression of Spurious Radiation Suppression of spurious and harmonic radiation in the DTSA is ensured through proper transmitter design, lay-out, and construction. 1. Transmitter Architecture and Design • Frequency plan of the transmitter—local oscillator frequencies were selected to minimize spurious products. • Use of an upconversion loop architecture to minimize spurious and noise power level in the PCS1900 receive band (1930-1990 MHz). • Additional filtering in the T/R switch to further reduce harmonics. This document contains PROPRIETARY and CONFIDENTIAL information of Omnipoint Technologies, Inc.

Omnipoint Technologies, Inc. Exhibit 6 FCC ID: OIIDTSA1900-2 Page 2 of 3 2. Physical Realization of the Transmitter Module • Fully shielded GSM radio module construction with filtering on all signal (data, control, clock) and power supply leads. • Localized shielding over the GSM radio sections. • Careful component placement and layout, multi-layer circuit board construction, microstrip signal routing, and construction techniques to eliminate cavity moding and resonances. Means for Limiting Modulation Per GSM specifications, the modulation scheme implemented by the DTSA is Gaussian MSK (GMSK), with a bandwidth-time product of BT=0.3. Modulation rate is 1625/6 kbps, or approximately 280.83 kbps. To minimize spreading of the spectrum, GSM standards require that the RF output spectrum meet the mask shown in Figure E6.1. In the DTSA radio module, modulation accuracy is maintained through the use of direct digital synthesis techniques. 10 0 -10 Power Relative to Carrier in 30 kHz BW (dB) -20 -30 -40 -50 -60 -70 0 500 1000 1500 2000 Frequency Offset from Carrier (kHz) Figure E6.1. GSM terminal modulation mask. Means for Limiting Power This document contains PROPRIETARY and CONFIDENTIAL information of Omnipoint Technologies, Inc.

Omnipoint Technologies, Inc. Exhibit 6 FCC ID: OIIDTSA1900-2 Page 3 of 3 As a GSM-compliant terminal, the DTSA will transmit at any of the 15 defined nominal RF output power levels, from 30 dBm to 0 dBm, during its assigned TDMA frame. Transmitter operation (power level and frame) is controlled by the GSM network, specifically by the base station to which the unit is in communication. Maximum RF output power of the DTSA is set at the factory and cannot be altered or increased. Furthermore, the temporal variation in power level within each transmission (i.e., transmission burst time mask) is in accordance with GSM requirements. This is accomplished by adjusting transmitter gain through a discrete time power control loop and ramping the transmitter on and off at the beginning and ending of each burst. The power control loop is implemented using an open loop technique proven to have little effect on output power versus temperature. Maximum RF power is adjusted to within the specified tolerance during each burst, at the output power level specified by the base station. This document contains PROPRIETARY and CONFIDENTIAL information of Omnipoint Technologies, Inc.


Document Created: 2001-06-25 16:50:19
Document Modified: 2001-06-25 16:50:19
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