AWR1642: AWR1642

Hello Peter,
The best way would be of the test house can perform 'triggered' measurements, ie trigger on the chirp burst and measure on that only. If their equipment does not support this kind of measurement then you might need to increase the framing duty cycle (ie reduce the frame periodicity) so that they can do an average measurement and compensate for the duty cycle.

Regards,
Vivek

The test lab can trigger off of a Sync signal.  I would think that their spectrum analyzer can sync off of the signal itself but perhaps, it is too fast.  Is there a signal on the AWR1642 that can be used as a trigger?

Peter

We will modify the software to trigger an Output pin immediately before it sends a chirp and increase the chirp rate.

Test lab also asked for any FCC IDs that may have already passed using the AWR1642 so they can see how that test was performed. Thanks, Peter

 

 The AWR1642 power seems to be <55dBm EIRP .  The FCC 15.256 rule is 34dBm EIRP.  Did you lower the power or are we OK because the 1642 sends a chirp so average power is less than 34dBm?

Peter

§15.256   Operation of level probing radars within the bands 5.925-7.250 GHz, 24.05-29.00 GHz, and 75-85 GHz.

(a) Operation under this section is limited to level probing radar (LPR) devices.

(b) LPR devices operating under the provisions of this section shall utilize a dedicated or integrated transmit antenna, and the system shall be installed and maintained to ensure a vertically downward orientation of the transmit antenna's main beam.

(c) LPR devices operating under the provisions of this section shall be installed only at fixed locations. The LPR device shall not operate while being moved, or while inside a moving container.

(d) Hand-held applications are prohibited.

(e) Marketing to residential consumers is prohibited.

(f) The fundamental bandwidth of an LPR emission is defined as the width of the signal between two points, one below and one above the center frequency, outside of which all emissions are attenuated by at least 10 dB relative to the maximum transmitter output power when measured in an equivalent resolution bandwidth.

(1) The minimum fundamental emission bandwidth shall be 50 MHz for LPR operation under the provisions of this section.

(2) LPR devices operating under this section must confine their fundamental emission bandwidth within the 5.925-7.250 GHz, 24.05-29.00 GHz, and 75-85 GHz bands under all conditions of operation.

(g) Fundamental emissions limits. (1) All emission limits provided in this section are expressed in terms of Equivalent Isotropic Radiated Power (EIRP).

(2) The EIRP level is to be determined from the maximum measured power within a specified bandwidth.

(i) The EIRP in 1 MHz is computed from the maximum power level measured within any 1-MHz bandwidth using a power averaging detector;

(ii) The EIRP in 50 MHz is computed from the maximum power level measured with a peak detector in a 50-MHz bandwidth centered on the frequency at which the maximum average power level is realized and this 50 MHz bandwidth must be contained within the authorized operating bandwidth. For a RBW less than 50 MHz, the peak EIRP limit (in dBm) is reduced by 20 log(RBW/50) dB where RBW is the resolution bandwidth in megahertz. The RBW shall not be lower than 1 MHz or greater than 50 MHz. The video bandwidth of the measurement instrument shall not be less than the RBW. If the RBW is greater than 3 MHz, the application for certification filed shall contain a detailed description of the test procedure, calibration of the test setup, and the instrumentation employed in the testing.

(3) The EIRP limits for LPR operations in the bands authorized by this rule section are provided in Table 1. The emission limits in Table 1 are based on boresight measurements (i.e., measurements performed within the main beam of an LPR antenna).

Table 1—LPR EIRP Emission Limits

Frequency band of operation (GHz)	Average emission limit (EIRP in dBm measured in 1 MHz)	Peak emission limit (EIRP in dBm measured in 50 MHz)
5.925-7.250	−33	7
24.05-29.00	−14	26
75-85	−3	34

(h) Unwanted emissions limits. Unwanted emissions from LPR devices shall not exceed the general emission limit in §15.209 of this chapter.

(i) Antenna beamwidth. (A) LPR devices operating under the provisions of this section within the 5.925-7.250 GHz and 24.05-29.00 GHz bands must use an antenna with a −3 dB beamwidth no greater than 12 degrees.

(B) LPR devices operating under the provisions of this section within the 75-85 GHz band must use an antenna with a −3 dB beamwidth no greater than 8 degrees.

(j) Antenna side lobe gain. LPR devices operating under the provisions of this section must limit the side lobe antenna gain relative to the main beam gain for off-axis angles from the main beam of greater than 60 degrees to the levels provided in Table 2.

Table 2—Antenna Side Lobe Gain Limits

Frequency range (GHz)	Antenna side lobe gain limit relative to main beam gain (dB)
5.925-7.250	−22
24.05-29.00	−27
75-85	−38

(k) Emissions from digital circuitry used to enable the operation of the transmitter may comply with the limits in §15.209 of this chapter provided it can be clearly demonstrated that those emissions are due solely to emissions from digital circuitry contained within the transmitter and the emissions are not intended to be radiated from the transmitter's antenna. Emissions from associated digital devices, as defined in §15.3(k) of this part, e.g., emissions from digital circuitry used to control additional functions or capabilities other than the operation of the transmitter, are subject to the limits contained in subpart B, part 15 of this chapter. Emissions from these digital circuits shall not be employed in determining the −10 dB bandwidth of the fundamental emission or the frequency at which the highest emission level occurs.

(l) Measurement procedures. (1) Radiated measurements of the fundamental emission bandwidth and power shall be made with maximum main-beam coupling between the LPR and test antennas (boresight).

(2) Measurements of the unwanted emissions radiating from an LPR shall be made utilizing elevation and azimuth scans to determine the location at which the emissions are maximized.

(3) All emissions at and below 1,000 MHz except 9-90 kHz and 110-490 kHz bands are based on measurements employing a CISPR quasi-peak detector.

(4) The fundamental emission bandwidth measurement shall be made using a peak detector with a resolution bandwidth of 1 MHz and a video bandwidth of at least 3 MHz.

(5) The provisions in §15.35(b) and (c) of this part that require emissions to be averaged over a 100 millisecond period and that limits the peak power to 20 dB above the average limit do not apply to devices operating under paragraphs (a) through (l) of this section.

(6) Compliance measurements for minimum emission bandwidth of frequency-agile LPR devices shall be performed with any related frequency sweep, step, or hop function activated.

(7) Compliance measurements shall be made in accordance with the specific procedures published or otherwise authorized by the Commission.

 

 

FCC 15.256 test results

Peak EIRP 34 dBm =>  OK

- peak power of TI IWR1642 (12 dBm) + antenna max gain (11 dBm) = 23 dBm < 34 dBm

 

2. Azimuth beam width 8 degree => Not OK

- azimuth 67 degree, elevation 20 degree.

 

3. Antenna side lobe gain -38 dB => Not OK

 

Making this product work well was very challenging.  The last of our concerns was beam power. They have performed very well on initial tests.   Do you know of any other FCC standards that might be satisfied with these gains? 

Will the power requirements diminish considering the AWR1642 Chirp that you mentioned above?  If yes, I will mention this to the test lab.  Thanks, Peter

We are considering moving our code over from the AWR1641 to the IWR6843 to more easily pass FCC requirements at 60GHz.  We did a lot of work doing distance measurement using the AWR1642 and fear the effort to move to the 6843.  We have not studied the 6843 much.  Is the internal functioning, pin usage, speed and other functionalities basically the same between the 6843 and the 1641 or do you think it will require a major code re-write?

Thanks, Peter