GB 13618-1992Requirements of electromagnetic environment protection for air defense surveillance radar station (English PDF)

2.1 Air defense surveillance radar station

An air defense surveillance radar station consists of the air defense surveillance radar, the interrogator and ancillary equipment. It is used in air defense and air traffic control systems to search for, monitor and identify airborne targets and to determine their coordinates. Air defense surveillance radars generally include early-warning, guidance, height-finding, target indication and air traffic control radars.

2.2 Radar station electromagnetic environment

The totality of the electromagnetic energy, and of its distribution in time and space, of all natural and man-made electromagnetic radiation within the operating frequency band of the radar around the radar station.

2.3 Maximum permitted interference voltage

Under conditions in which harmful interference cannot be completely avoided, the maximum interference voltage permitted at the input of the radar receiver, determined in accordance with the interference protection criteria.

2.4 Maximum permitted interference field strength

The interference field strength at the height of the centre of the radar antenna when the interference voltage at the input of the radar receiver is at its maximum permitted value.

2.5 Radar station protection distance

The minimum separation distance between the radar antenna and each interference source that satisfies the requirements of the interference protection criteria.

2.6 Interference duration

The continuous time during which the interference voltage at the input of the radar receiver exceeds the maximum permitted value.

2.7 Electromagnetic obstacle

Installations capable of shielding or interfering with the high-frequency electromagnetic waves radiated by the radar are collectively referred to as electromagnetic obstacles.

3.1

Under conditions in which active interference is unavoidable, an air defense surveillance radar is permitted a loss of detection range of not more than 5%.

3.1.1

For white noise interference, the maximum permitted interference voltage at the input of the radar receiver is:

Ujfmax = 0.48 Unf ... (1)

where:

Ujfmax - r.m.s. value of the maximum permitted interference voltage at the receiver input, µV;

Unf - r.m.s. value of the system noise voltage referred to the receiver input, µV; for values see Table 1.

Table 1 - Equivalent noise voltage at the receiver input: frequency 80 MHz to 300 MHz, Unf = 0.77 µV; frequency 300 MHz to 3 000 MHz, Unf = 0.85 µV.

3.1.2

For random high-frequency pulse interference of different kinds, the maximum permitted interference voltage at the input of the radar receiver is:

Ujfmax = 0.48 C Unf ... (2)

where:

C - increment coefficient of the maximum permitted interference voltage relative to white noise; for values see Table 2.

Table 2 - Increment coefficients for random high-frequency pulse interference of different kinds: high-voltage overhead power transmission lines and substations, C = 3; electrified railways, C = 4; motor highways, C = 4; high-frequency heat sealing machines, C = 4; industrial electric welding, C = 5.4; high-frequency physiotherapy apparatus, C = 5.4; high-frequency furnaces, C = 5.4.

3.1.3

Maximum permitted interference voltage at the input of the radar receiver for amplitude-modulated and frequency-modulated interference signals outside the receiver passband.

3.1.3.1

The maximum permitted interference voltage at the receiver input for adjacent-frequency interference signals outside the passband is:

UjpDeltafmax = Ujpmax + KDeltaf ... (3)

where:

UjpDeltafmax - peak value of the maximum permitted interference voltage outside the receiver passband, dB(µV);

Ujpmax - peak value of the maximum permitted interference voltage within the receiver passband; for values see Table 3;

KDeltaf - out-of-band rejection coefficient of the receiver when the frequency of the interference signal deviates by Deltaf from the operating frequency of the receiver, dB; for values see Table 4.

Table 3 - Maximum permitted interference voltage within the receiver passband, Ujpmax, dB(µV): amplitude modulation, 80 MHz to 300 MHz: 6; amplitude modulation, 300 MHz to 3 000 MHz: 6.9; frequency modulation, 80 MHz to 300 MHz: 18; frequency modulation, 300 MHz to 3 000 MHz: 18.7.

Table 4 - Out-of-band rejection coefficient of the receiver, KDeltaf, dB (frequency deviation in MHz: value for 80 MHz to 300 MHz / value for 300 MHz to 3 000 MHz): 0.3: 10 / -; 0.5: 20 / -; 1.0: 50 / -; 1.5: 63 / 10; 2.0: 70 / 33; 2.5: - / 51; 3.0: - / 62; 3.5: - / 66; 4.0: - / 70.

3.1.3.2

When the interference signal frequency fj satisfies the condition of formula (4), the interference voltage at the input of the radar receiver shall be less than 85 dB(µV).

fj = (n fLO ± fI) / m ... (4)

where:

fj - interference signal frequency, MHz;

n - harmonic order of the local oscillator frequency, positive integer 1, 2, 3;

fLO - local oscillator frequency of the receiver, MHz;

fI - intermediate frequency of the receiver, MHz;

m - harmonic order of the interference frequency, positive integer 1, 2, 3.

3.1.3.3

If two or more interference signals enter the input of the radar receiver simultaneously and their frequencies satisfy the conditions for producing second- or third-order intermodulation interference, the voltage of one of the interference signals shall be lower than 60 dB(µV).

3.1.3.4

Outside the high-frequency amplifier passband of the radar receiver, where the interference signal frequency satisfies neither formula (4) nor the conditions for intermodulation interference, the interference signal voltage shall be less than 110 dB(µV).

3.2

The loss of radar detection range caused by electromagnetic obstacles shall not exceed 5% of the detection range.

3.3

A single continuous interference shall not last more than 10 s, the interval between two interferences shall be not less than 10 s, and the cumulative interference time per hour shall not exceed 5% of the operating time.