K7DLMP4213

linear modulation technology Intek Global Technologies Ltd MEMORANDUM 1 TO: George Tannahill FCC Application Processing Branch FROM: Andrew Cunningham Phone: +44 (0) 1761 408289 Email: [email protected] DATE: 05 August 1999 SUBJECT: Response to questions on pending application Re: correspondence reference number 8862, date 07/22/1999 FCC ID K7DLMP4213 731 confirmation number EA93897 This document contains 2 sections. Firstly, the correction to a typographical error in the submission; secondly, the response to the 5 questions in your correspondence. I hope that the information given is acceptable. If you have any further queries please contact me. Best regards Andrew linear modulation technology Intek Global Technologies Ltd MEMORANDUM 2 ERRATUM Page 72 section 5.2 – 2.985(a) RF Output Power Due to a typographical error, the results table should be replaced with the one given below. The value corrected is– Measured Level at 162.0000 MHz should be 6.11 dBm (not 7 dBm). This is the value recorded at LMT during the formal testing. No other calculations or results are affected by this error. The power indicated (4.80 Watts) was calculated using the correct measured level on the existing submission, and is unchanged. FrequencyMeasured Level (L) Attenuation (A) Power (P) MHzdBmdBWatts 150.00006.3230.64.92 156.00006.3230.64.92 162.00006.1130.74.80 linear modulation technology Intek Global Technologies Ltd MEMORANDUM 3 Answers to Questions Question 1 – bandwidth justification The modulation process for audio and data signals is described in the answer to Question 3. The modulation schemes for voice and data are identical to those used on the K7DLMP4215 220 MHz Handportable radio and K7DLMM4113D 150 – 162 MHz mobile radio. The modulation scheme is designed for operation in 4 kHz occupied bandwidth such as that allowed on the 220 MHz band, and is suitable for use in 6 kHz occupied bandwidth systems in the 150 – 162 MHz band . Voice Voice signals with an audio spectrum of 300 Hz to 3 kHz are modulated onto an RF pilot signal using TTIB techniques, which includes a additional band of 600 Hz. This gives a resultant RF bandwidth of 2700 Hz + 600 Hz = 3300 Hz. A bandwidth designator of 4 kHz is sought. TTIB is a form of pilot aided single sideband modulation. A modulation designator of J3E is sought – suppressed carrier single sideband modulation, analogue modulation, voice transmission. Data Incoming data signals at up to 19,200 bit/s are buffered to a rate of 1200 bit/s and are fed into the DSP based FFSK modulator, from which point they follow the same modulation process as the audio signals. The occupied RF bandwidth will thus not exceed 3300 Hz, and a bandwidth designator of 4 kHz is sought. The data signal is FFSK modulated and then passed through the TTIB modulation process. A modulation designator of J2D is sought – suppressed carrier single sideband modulation, digital signal– modulated subcarrier analogue modulation, data transmission. Question 2 – user manual mentions high speed data The 75-P4213 handportable does not support high speed data and this is explicitly stated on p33 of the User Manual (p62 of the submission). The user manual mentions a higher data rate on p12 (page 41 of the submission). This is describing the general performance of the LM system environment in which the handportable radio would operate, which consists also of mobile radios and base repeater channels; the K7DLMM4113D mobile radio and K7DLMC4003 base repeater both support 14.4 kb/s data. linear modulation technology Intek Global Technologies Ltd MEMORANDUM 4 Question 3 – description of signal parameters, modulation technique, signal path for data signal. LINEAR MODULATION Definition Linear Modulation (LM) is a Radio Frequency (RF) transmission technique suitable for the transfer of speech and high speed data over a radio bearer which is narrow band. In this context narrow band is a 5 kHz bandwidth radio channel. The speech quality over 5 kHz channel using LM techniques is equal to, or better than that achieved from a 12.5 kHz channel using Frequency Modulation. Also adjacent and co-channel performance easily exceeds that specified for 12.5 kHz channels and is in excess of that specified for narrow band systems both by the DTI in the United Kingdom and the FCC in the United States. Note also that for Linear Modulation systems, significant energy is only transmitted when the transmitter is modulated. This is similar to Single Side Band operation but is unlike Frequency Modulated transmissions, which operate constant envelope. This fact provides a lower power consumption for LM equipment when compared to AM or FM equipment which is particularly important for the sizing of standby power systems and for hand-portable units. LM Methods Linear Modulation uses a number of methods to achieve this high quality performance. These are the use of a Transparent Tone In Band (TTIB) reference signal, Feed Forward Signal Regeneration (FFSR) for signal recovery and Cartesian loop linearisation of the RF transmitter. For the TTIB technique, the audio baseband is split at 1650 Hz to give an upper and lower sub- band, and the two sub-bands are moved apart in frequency to form a gap. A calibrated pilot tone is then inserted in this gap. The resulting signal is then linearly translated up to RF using a direct conversion quadrature transmitter, so that the pilot tone falls on the channel centre. A frequency inversion also takes place during this process. In the receiver, FFSR is used to correct for Doppler shift and multipath distortions which affect signals when transmitted in mobile environments. The distortions on the path are calculated from the received pilot tone, and the whole audio band is then corrected for these distortions. The two halves of the audio band are then inverted and rejoined to give the recovered audio signal. The Cartesian loop process linearises the transmitter and minimises radiation into adjacent a…

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