RF output attenuators for generators and test setups · Attenuation value and flatness, VSWR and mismatch, power rating, fixed vs step vs programmable
An output attenuator is a passive network placed at the output of a signal generator, amplifier or test port to lower the signal level by a known number of decibels without changing its frequency, while improving the impedance match seen by the next device. Decide three things before ordering: the attenuation value or range and the frequency band with its flatness, the VSWR the setup can tolerate, and the power the attenuator must absorb together with its connectors and control method.
Fixed, rotary step, continuously variable and digitally programmable coaxial and surface-mount RF attenuators used to set output level in test and signal-generation setups. Fibre-optic attenuators, audio attenuators, RF terminations and loads sold alone, and waveguide attenuators are outside this page.
01
Mini-Circuits' application note on fixed attenuators says that besides controlling amplitude, they improve the match between impedance-sensitive devices and provide isolation to stabilise oscillators. It defines VSWR as the figure of merit for match — 1.0:1 is perfect — and notes that in a test system with a spectrum analyser, the dynamic range decreases by the total attenuation added. [1]
The note's worked example: an amplifier rated at +27 dBm output feeding a spectrum analyser with a +25 dBm maximum input needs an attenuator of 5 dB or more; a 4 dB attenuator whose flatness keeps it within 3–5 dB could also serve. It advises that VSWRs of connected components tend to multiply, so 3.0:1 into 1.50:1 can give 4.50:1 and 3.93 dB return loss, and that choosing the lowest-VSWR attenuator minimises mismatch. In a receiver, a 3 dB attenuator ahead of the low-noise amplifier sets a 3 dB minimum noise figure. [1]
The VAT-10+ datasheet lists a 50 Ω SMA fixed attenuator of 10 ± 0.3 dB from DC to 6,000 MHz, with attenuation varying 0.3 dB maximum over temperature, flatness of 0.10–0.20 dB (typ.) by band, VSWR of 1.25:1 maximum to 3 GHz and 1.90:1 maximum from 5 to 6 GHz, a 1 W input rating and operation from −45 to 100 °C. [2]
Editorial calculation: two ports at 1.5:1 each give a worst case of 1.5 × 1.5 = 2.25:1, a return loss of about 8.3 dB, by the multiplication rule in the note. [1]
Give the supplier the frequency range, attenuation value (or range and step size), accuracy and flatness, maximum VSWR or minimum return loss, impedance (50 or 75 Ω), average and peak input power, connector types and genders, control method for step or programmable units, operating temperature, PIM limit if used in a cellular system, and quantity.
02
Mini-Circuits' ZX76-31R5A-PPS+ datasheet describes a 50 Ω, 6-bit digital step attenuator from DC to 4 GHz, set from 0 to 31.5 dB in 0.5 dB steps with 0.1 dB accuracy (datasheet typ.), a parallel 5 V logic control interface and SMA connectors. It lists insertion loss at the 0 dB setting of 1.4 dB typ. (2.0 dB maximum) to 1 GHz, rising to 2.5 dB typ. from 2.4 to 4 GHz, and 18 dB typ. return loss. [3]
Yusntech, an attenuator supplier, describes fixed attenuators at set values such as 3, 6 or 20 dB; rotary step attenuators that change in increments such as 1 dB or 10 dB for repeatable testing; continuously variable and programmable attenuators; and surface-mount versions. [4] Linked suppliers list coaxial fixed attenuators from 0.5 W to 1,000 W average power and DC to 40 GHz [5], and low-PIM 200 W attenuators for 698–3,800 MHz cellular systems. [6]
Editorial calculation: a +27 dBm signal is 0.5 W; through the 1 W, 10 dB VAT-10+ the output is +17 dBm (50 mW) and the attenuator absorbs about 0.45 W — inside its rating, but a +33 dBm (2 W) source would need a higher-power part. [2] [1]
03
Suppliers linked to this page list RF attenuators; each card links to the page reviewed.
The listings reviewed range from SMA and N-type coaxial fixed attenuators and 1 dB step attenuators to high-power and low-PIM units for in-building systems, and chip, flanged, leaded and microstrip attenuators for boards. Ask each for measured attenuation and VSWR against frequency, power derating and connector specification. [4] [5] [6] [7] [8] [9] [10]
04
This is a functional reference built from the sources cited; it is not one maker's specification.
| Part | Role | Fix in the order |
|---|---|---|
| Resistive network | Sets attenuation and match. [2] | Value; flatness. |
| Body and heat sink | Absorbs input power. [5] [6] | Power rating; derating. |
| Connectors | Interface and VSWR. [2] [8] | Type; gender. |
| Step switch or control | Sets value. [3] [4] | Steps; interface. |
| Low-PIM construction | Cellular systems. [6] [7] | PIM limit. |
| Housing | Ruggedness. [2] | Size; mounting. |
05
An attenuator quotation needs values for your setup. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Frequency Range | DC–6 GHz (VAT-10+); DC–4 GHz (step). [2] [3] | Band. |
| Attenuation | 10 dB fixed; 0–31.5 dB in 0.5 dB steps. [2] [3] | Value or range; step. |
| Attenuation Accuracy | ±0.3 dB; 0.1 dB typ. (step). [2] [3] | Accuracy; flatness. |
| Impedance | 50 Ω; 75 Ω versions exist. [2] [1] | Impedance. |
| VSWR | 1.25:1 max to 3 GHz (VAT-10+). [2] | VSWR curve. |
| Insertion Loss | 1.4 dB typ. at 0 dB setting to 1 GHz (step). [3] | At 0 dB setting. |
| Power Handling | 1 W (VAT-10+); 0.5–1,000 W range listed. [2] [5] | Average; peak; derating. |
| Operating Temperature | −45 to 100 °C (VAT-10+). [2] | Range. |
| Connector Type | SMA, N, 7/16 DIN. [2] [6] [8] | Type; gender. |
| Weight | 10.0 g (VAT-10+). [2] | Weight. |
06
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Band: [MHz–GHz] Attenuation: [dB value or range; step] Accuracy: [± dB; flatness] Match: [max VSWR; impedance] Power: [average; peak] Connectors: [type; gender] Control: [fixed; rotary; programmable interface] Quantity: [units]
These companies list RF attenuators.
Lists fixed, rotary step, continuously variable and programmable RF attenuators.
Product scope checked 2026-10-11
Lists coaxial fixed attenuators DC–40 GHz, 0.5–1,000 W.
Product scope checked 2026-10-11
Lists 10–200 W coaxial attenuators to 6 GHz, including low-PIM types.
Product scope checked 2026-10-11
Lists SMA, step and high-power attenuators, including low-PIM types.
Product scope checked 2026-10-11
Lists N-type, DIN and BNC coaxial fixed attenuators.
Product scope checked 2026-10-11
Lists RF coaxial fixed attenuators.
Product scope checked 2026-10-11
Lists chip, flanged, leaded, microstrip and coaxial attenuators.
Product scope checked 2026-10-11
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
Mini-Circuits' example: 5 dB or more for a +27 dBm amplifier into a +25 dBm analyzer. [1]
Yes; Mini-Circuits notes dynamic range decreases by the total attenuation added. [1]
Mini-Circuits' VAT-10+ lists 10 ± 0.3 dB from DC to 6 GHz. [2]
An attenuator set by logic inputs; Mini-Circuits' ZX76-31R5A-PPS+ covers 0–31.5 dB in 0.5 dB steps. [3]
Sources checked 2026-10-11. Mini-Circuits publishes an application note on fixed attenuators and datasheets for a fixed and a digital step attenuator; the rest are linked suppliers.
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