§  15.252   Operation of wideband vehicular radar systems within the band
23.12-29.0 GHz.

   (a) Operation under this section is limited to field disturbance
   sensors that are mounted in terrestrial transportation vehicles.
   Terrestrial use is limited to earth surface-based, non-aviation
   applications.

   (1) The −10 dB bandwidth of the fundamental emissions shall be located
   within the 23.12-29.0 GHz band, exclusive of the 23.6-24.0 GHz
   restricted band, as appropriate, under all conditions of operation
   including the effects from stepped frequency, frequency hopping or
   other modulation techniques that may be employed as well as the
   frequency stability of the transmitter over expected variations in
   temperature and supply voltage.

   (2) The −10 dB bandwidth of the fundamental emission shall be 10 MHz or
   greater. For transmitters that employ frequency hopping, stepped
   frequency or similar modulation types, measurement of the −10 dB
   minimum bandwidth specified in this paragraph shall be made with the
   frequency hop or step function disabled and with the transmitter
   operating continuously at a fundamental frequency following the
   provisions of § 15.31(m).

   (3) For systems operating in the 23.12-29.0 GHz band, the frequencies
   at which the highest average emission level and at which the highest
   peak level emission appear shall be greater than 24.075 GHz.

   (4) These devices shall operate only when the vehicle is operating,
   e.g., the engine is running. Operation shall occur only upon specific
   activation, such as upon starting the vehicle, changing gears, or
   engaging a turn signal. The operation of these devices shall be related
   to the proper functioning of the transportation vehicle, e.g.,
   collision avoidance.

   (b) Emissions from a transmitter operating under this section shall not
   exceed the following equivalent isotropically radiated power (EIRP)
   density levels:

   (1) For transmitters operating in the 23.12-29.0 GHz band, the RMS
   average radiated emissions above 960 MHz from a device operating under
   the provisions of this section shall not exceed the following EIRP
   limits based on measurements using a 1 MHz resolution bandwidth:
   Frequency in MHz EIRP in dBm
   960-1610               −75.3
   1610-23,120            −61.3
   23,120-23,600          −41.3
   23,600-24,000          −61.3
   24,000-29,000          −41.3
   Above 29,000            —61.3

   (2) In addition to the radiated emissions limits specified in the table
   in paragraph (b)(1) of this section, transmitters operating under the
   provisions of this section shall not exceed the following RMS average
   EIRP limits when measured using a resolution bandwidth of no less than
   1 kHz:
   Frequency in MHz EIRP in dBm
   1164-1240              −85.3
   1559-1610              −85.3

   (3) There is a limit on the peak level of the emissions contained
   within a 50 MHz bandwidth centered on the frequency at which the
   highest radiated emission occurs and this 50 MHz bandwidth must be
   contained within the 24.05-29.0 GHz band. The peak EIRP limit is 20 log
   (RBW/50) dBm where RBW is the resolution bandwidth in MHz employed by
   the measurement instrument. RBW shall not be lower than 1 MHz or
   greater than 50 MHz. Further, RBW shall not be greater than the −10 dB
   bandwidth of the device under test. For transmitters that employ
   frequency hopping, stepped frequency or similar modulation types,
   measurement of the −10 dB minimum bandwidth specified in this paragraph
   shall be made with the frequency hop or step function disabled and with
   the transmitter operating continuously at a fundamental frequency. The
   video bandwidth of the measurement instrument shall not be less than
   RBW. The limit on peak emissions applies to the 50 MHz bandwidth
   centered on the frequency at which the highest level radiated emission
   occurs. If RBW is greater than 3 MHz, the application for certification
   shall contain a detailed description of the test procedure, the
   instrumentation employed in the testing, and the calibration of the
   test setup.

   (4) Radiated emissions at or below 960 MHz shall not exceed the
   emission levels in § 15.209.

   (5) Emissions from digital circuitry used to enable the operation of
   the transmitter may comply with the limits in § 15.209 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) , 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 of this
   part. 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.

   (c) Measurement procedures:

   (1) All emissions at and below 960 MHz are based on measurements
   employing a CISPR quasi-peak detector. Unless otherwise specified, all
   RMS average emission levels specified in this section are to be
   measured utilizing a 1 MHz resolution bandwidth with a one millisecond
   dwell over each 1 MHz segment. The frequency span of the analyzer
   should equal the number of sampling bins times 1 MHz and the sweep rate
   of the analyzer should equal the number of sampling bins times one
   millisecond. The provision in § 15.35(c) that allows emissions to be
   averaged over a 100 millisecond period does not apply to devices
   operating under this section. The video bandwidth of the measurement
   instrument shall not be less than the resolution bandwidth and trace
   averaging shall not be employed. The RMS average emission measurement
   is to be repeated over multiple sweeps with the analyzer set for
   maximum hold until the amplitude stabilizes.

   (2) The peak emission measurement is to be repeated over multiple
   sweeps with the analyzer set for maximum hold until the amplitude
   stabilizes.

   (3) For transmitters that employ frequency hopping, stepped frequency
   or similar modulation types, the peak emission level measurement, the
   measurement of the RMS average emission levels, the measurement to
   determine the center frequency, and the measurement to determine the
   frequency at which the highest level emission occurs shall be made with
   the frequency hop or step function active. Gated signals may be
   measured with the gating active. The provisions of § 15.31(c) continue
   to apply to transmitters that employ swept frequency modulation.

   (4) The −10 dB bandwidth is based on measurement using a peak detector,
   a 1 MHz resolution bandwidth, and a video bandwidth greater than or
   equal to the resolution bandwidth.

   (5) Alternative measurement procedures may be considered by the
   Commission.

   (d) Wideband vehicular radar systems operating in the 23.12-29.0 GHz
   band are subject to the transition provisions of § 15.37(l) through (n).

   [ 70 FR 6775 , Feb. 9, 2005, as amended at  82 FR 43870 , Sept. 20, 2017]