Low-noise block downconverter (LNB)

01

Match the band, LO frequency and IF output

Norsat's 1000-series Ku-band single-band auto-reference PLL LNB converts an input of 10.95–11.80 GHz with a 10.00 GHz phase-locked local oscillator to an output of 950–1800 MHz. It accepts a 10 MHz external reference at −5 to +5 dBm and switches to its internal reference if none is detected. [1]

Its dual-band model covers 10.95–11.70 GHz with a 10.00 GHz LO (950–1700 MHz out) and 11.70–12.75 GHz with a 10.75 GHz LO (950–2000 MHz out), selected by 13 V or 18 V supply without tone. [2]

Editorial calculation: IF equals RF minus LO, so 10.95 − 10.00 = 0.95 GHz and 11.80 − 10.00 = 1.80 GHz, matching the 950–1800 MHz output; for the upper band, 12.75 − 10.75 = 2.00 GHz. [1] [2]

Give the supplier the satellite band and transponder frequencies, required IF range and modem input, single- or dual-band operation and switching method, LO type (PLL with external reference or internal), required LO stability and phase noise, feed or waveguide interface, IF connector, supply voltage, environment and quantity.

02

Check noise figure, gain, stability and interfaces

The Norsat 1000 lists noise figure 0.8 dB typical and 0.9 dB maximum, conversion gain 60 dB typical (55–65 dB), gain flatness ≤1 dB p-p over any 36 MHz and ≤4 dB p-p over the band, image rejection of at least 40 dBc, output P1dB of at least +5 dBm, input and output VSWR of 2.5:1 maximum, LO stability of ±10 kHz and phase noise no worse than −70, −80 and −95 dBc/Hz at 1, 10 and 100 kHz offsets. [1]

It draws 350 mA from +12 to +24 V, has a WR-75 grooved waveguide RF input and an N-type IF connector, is rated IP67 for −40 °C to +60 °C, and measures 111.5 × 60 × 41.6 mm at 0.38 kg. The dual-band model lists 0.9 dB typical noise figure and 50–60 dB gain with the same phase noise and interfaces. [1] [2]

Editorial calculation: 350 mA at 24 V is 8.4 W, and at 12 V 4.2 W. [1]

Swedish Microwave AB (SMW), which states it has made LNBs as its core business since 1986 for bands from C-band to Q-band, gives its own selection points. For high data and symbol rates it stresses phase noise and reference stability, quoting an internal reference stability of ±0.5 ppm over −40 to +80 °C for 10 years without recalibration and an AutoSwitch between internal and external references; for return loss it sometimes fits a low-loss isolator, accepting a slightly worse noise figure; and for saturation it gives the rule of thumb that a low-gain LNB should be considered if the antenna is over 3.7 m in diameter. Its standard storage and operating range is −40 to +80 °C. SMW says each unit is tested before shipment and that the per-serial-number test report covers LO frequency variation on internal and external reference at −40 °C and 80 °C, current, gain (nominal, flatness, minimum, maximum), S11 and S22 return loss, noise figure (nominal and maximum), LO calibration tolerance and phase noise at 10 Hz, 100 Hz, 1 kHz, 10 kHz and 100 kHz offsets. [4] Editorial calculation: ±0.5 ppm of a 10.00 GHz LO is ±5 kHz, half of the ±10 kHz LO stability listed for the Norsat 1000. [4] [1]

03

Find LNB manufacturers

The companies in the manufacturer list below show this product on their own websites. Confirm the legal seller, factory and scope for your order.

Ask any supplier for RF and IF bands, LO frequencies and type, noise figure, gain and flatness, LO stability over temperature, phase noise, image rejection, P1dB, VSWR, reference input, supply and current, connectors and waveguide flange, IP rating, temperature range, dimensions and weight.

04

Ask for test results against the EN 303 372-1 radio limits

For outdoor units receiving 10.7–12.75 GHz broadcast signals, ETSI's harmonised standard EN 303 372-1 V1.2.1 (2021) sets radio limits that apply to the LNB. Unwanted radiation measured at the antenna flange, including LO leakage, must not exceed −60 dBm in a 120 kHz bandwidth at the LO fundamental, −50 dBm in a 120 kHz bandwidth at the LO second harmonic and −60 dBm in any other 120 kHz bandwidth, across 2.5 GHz to 25 GHz. The LNB must suppress image frequencies by at least 40 dB, because with a LO below the received frequency the image falls in a band allocated to maritime radar and other high-power navigation systems. [3]

Receiver blocking is tested with a wanted signal at band centre and a second signal that causes 1 dB gain compression; the minimum rejection is 20 dB below 9 GHz, 10 dB from 9 to 10 GHz, 10 dB from 14 to 16 GHz and 20 dB above 16 GHz. For an LNB with integrated feed (LNBF), ETSI also requires cross-polar discrimination of at least 20 dB including cross-talk, a clamp diameter of 23 mm or 40 mm, and a phase-centre mark 25 mm from the phase centre. [3]

Editorial note: a datasheet line such as image rejection of at least 40 dBc meets the ETSI minimum exactly, with no margin; ask the supplier for the measured LO leakage, image rejection and blocking results and for the test report reference. [3]

05

Trace what each part does

This is a functional reference built from the sources cited; it is not one maker's specification.

06

Fill the specification fields with values for your order

An LNB quotation needs values for your terminal. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

07

Send the band, link and terminal data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Band: [Ku; other; RF range]
LO: [GHz; PLL; external reference]
IF: [range; modem]
Performance: [NF; gain; stability; phase noise]
Bands: [single; dual; switching]
Interfaces: [waveguide; IF connector]
Power: [V; mA]
Environment: [IP; temperature]

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