SS Radio Operation SS Radio will be operated at 915 ( 13 Mhz in Frequency Hoping mode. Maximum date rate will be 250 KBPS Radio will operate with 128 channels. Nonproductive channels can be eliminated. There will be several sets of predefined hoping sequences. One sequence will be used as a paging channel. Hoping channels sequences are negotiated between radios or a master/slave relationship will be used. Transmit power will be dynamically adjustable with maximum being in the 1 to 5 watt range. Each channel quality will be monitored by RSSI and data error rates. Initial design will use QPSK modulation. Three IF scenarios (listed below) were considered and Option 3 is currently the method of choice. Issues 1.) Settling rate of NCO selected. 2.) Linearity and Bandwidth of first IF. 3.) Resolution of NCO selected. Can we jump around with the NCOs on the 1st IF and maintain (100 kHz at baseband? 4.) Will QPSK work with dynamic path conditions and radio component variations. Modulation Possibilities For FSK: 1.) 2000 bits/frame [1560 bits or Ethernet + control bits] FSK 2.) Throughput = 100 kb/s 3.) R = 1/2 (vitdec) 4.) Channel rate = 200 kb/s 5.) 2000 bits/200,000 bits/sec = 10 mSec. (Plus keyup delay?) 6.) Chan width ~ F (dev) + 2 F(dev) ~ F(dev) + 400 kHz ~ 800 kHz 7.) 26 MHz/800 kHz ~ 32 channels fit in 26 MHz 8.) 4 users. 4/32 = use factor = 1/8 collisions or # attempts = 1 + 1/8 + 1/64 + ... ~ 1.2 or 83.3 % use factor For QPSK: 1.) 2000 bits/frame [1560 bits or Ethernet + control bits] FSK 2.) Throughput = 100 kb/s 3.) R = 1/2 (vitdec) 4.) Channel rate = 200 kb/s 5.) 2000 bits/200,000 bits/sec = 10 mSec. (Plus keyup delay?) 6.) 2 bits/symbol --> 100,000 symbols/sec channel width ~ 200 kHz 7.) 26 MHz/200 kHz ~ 128 channels 8.) 4 users -> 4/128 = 1/32 collisions ~ 100 % use factor 9.) Phase: 10 mSec move 1/8 cycle of carrier (~20 MHz) 50 nSec/8 = 6 nSec Drift: ( 6 nSec/10 mSec 20 MHz = 20 Mcycles/Sec * 10 mSec = 200 cycles 20. MHz ( 10 kHz => 200 cycles ( 0.1 cycle IF Option 1 Input 915 ( 13 MHz Output 1st IF Fixed Frequency 100 MHz ( 13 MHz 1st LO Fixed Frequency 815 MHz 2nd IF Hoping Baseband 2nd LO Hoping 100 MHz ( 13 MHz 10 bit A/D's operating at 1 MHz 10 bit D/A's operating at 1 MHz Filters would be 100 MHz center frequency at least 6 MHz bandwidth and built with components. . NCO would be used for 2nd LO mixed with one of several fixed oscillator stages. IF Option 2 Input 915 ( 13 MHz Output 1st IF Bank of Frequencies 100 MHz ( 3 MHz 1st LO Bank of Frequencies 815 MHz 2nd IF Hoping Baseband 2nd LO Hoping 100 MHz ( 3 MHz 10 bit A/D's operating at 1 MHz 10 bit D/A's operating at 1 MHz Filters would be 100 MHz center frequency at least 6 MHz bandwidth and built with components. NCO would be used for 2nd LO and it would range from 4 to 10 MHz and be mixed with a 96 MHz fixed reference. NCO = HSP45102 Harris Semiconductor IF Option 3 Input 915 ( 13 MHz Output 1st IF Bank of NCO's 21.4 MHz ( 100 kHz 1st LO Bank of NCO's 936.4 MHz ( 13 MHz 2nd IF Fixed Baseband 2nd LO Fixed 21.4 MHz ( 3 MHz 10 bit A/D's operating at 1 MHz 10 bit D/A's operating at 1 MHz Filters would be 100 MHz center frequency at least 6 MHz bandwidth and built with components. 2 or more NCOs would be used for 1nd LO and they will be switched to allow each NCO to settle.