RF balun transformers · Frequency range and bandwidth by insertion loss, impedance and impedance ratio, amplitude and phase unbalance, return loss, power and DC current limits, package and land pattern
A balun transformer converts between a balanced (differential) signal and an unbalanced (single-ended) one, and an RF transformer can also change impedance, for example from 50 Ω to 200 Ω; they are used for impedance matching and balanced amplifiers. Ask three things first: what frequency band and impedances the circuit uses, how much loss and unbalance it can tolerate across that band, and what RF power, DC current and package it needs.
Wire-wound and planar RF baluns and RF transformers for RF, microwave and mmWave signal circuits, in surface-mount and through-hole packages. Antenna baluns for broadcast or amateur radio, power transformers, common-mode chokes and LAN magnetics are outside this page except where compared.
01
Mini-Circuits' ADT1-1WT datasheet describes a 75 Ω surface-mount RF transformer with an impedance ratio of 1 for 0.4–800 MHz, for impedance matching and balanced amplifiers. It specifies bandwidth by insertion loss relative to the 0.3 dB mid-band loss: 0.4–800 MHz within 3 dB, 0.5–700 MHz within 2 dB and 1–400 MHz within 1 dB. The ADT4-1WT is a 50 Ω part with a secondary-to-primary impedance ratio of 4, for 2–775 MHz (3 dB), 3–600 MHz (2 dB) and 6–250 MHz (1 dB), with 0.8 dB mid-band loss, listed for impedance matching and baluns. [1] [2]
Sunuprise lists RF transformers and baluns for impedance matching, balanced-to-unbalanced conversion and DC isolation, with cross-references and, for each part, low and high frequency, impedance, impedance ratio, insertion loss, input and output return loss, common-mode rejection and amplitude and phase balance; for example SBL-B01-75011-089 at 5–200 MHz, 75 Ω, 1:1, 0.8 dB insertion loss, 16 dB return loss, 0.3 dB amplitude and 1° phase balance. [3]
Editorial calculation: a 1:4 impedance ratio steps 50 Ω to 200 Ω, which corresponds to a 1:2 turns ratio. Mid-band losses of 0.3 dB and 0.8 dB pass about 93% and 83% of the input power. [1] [2]
Give the supplier the frequency band, source and load impedances, impedance ratio and whether a centre tap is needed, maximum insertion loss and minimum return loss across the band, amplitude and phase unbalance limits, RF power and any DC current through the windings, operating temperature, package and land pattern, and cross-reference parts if replacing.
02
The ADT1-1WT datasheet gives amplitude unbalance of 0.1 dB typical and phase unbalance of 1° typical within its 1 dB bandwidth, rising to 0.5 dB and 4° within the 2 dB bandwidth; operating temperature −20 to +85 °C, storage −55 to +100 °C, and maximum ratings of 0.5 W RF power and 30 mA DC current. The ADT4-1WT gives 20 dB typical return loss, 0.1 dB and 1° unbalance in its 1 dB band (0.3 dB and 3° in the 2 dB band) and 0.25 W RF power. [1] [2]
Editorial calculation: 20 dB return loss means a reflection coefficient of 0.1, a VSWR of about 1.22. Because unbalance and loss widen towards the band edges, specify limits at the band edges you use, not only the typical mid-band figures. [2] [1]
Editorial note: ask the supplier for measured insertion loss, return loss and unbalance curves on its test board, and for the recommended land pattern, since layout affects performance.
03
US patent 11,456,717 B2, assigned to Texas Instruments, describes a balun or transformer converting a single-ended RF signal into a differential input for a high-speed ADC. Mismatched impedances in the transformer make the two outputs unequal in amplitude and shift their phase away from 180°, and the patent states that the resulting second-order non-linearity dominates in amplitude. In its multi-band example a single dual-band ADC receives a 1.8 GHz band and a 3.5 GHz band through one balun; the second-order products of the 1.8 GHz band land on the 3.5 GHz band and can severely degrade it when the 3.5 GHz signal is the weaker of the two. [4]
Editorial calculation: the second harmonic of 1.8 GHz is 3.6 GHz, 100 MHz from the 3.5 GHz band named in the patent, so a dual-band receiver of this kind depends on the balun's phase and amplitude balance rather than on filtering. [4]
The patent compares three published front ends and its own: a double balun shows less phase imbalance but more amplitude imbalance than a single transformer; a double transformer shows less phase imbalance than the double balun but more amplitude imbalance than the single transformer. Its configuration feeds two matched balun transformers, cross-coupled at their outputs, from an input balun, which cancels first-order common-mode current and reduces second-order common-mode current; the overall impedance ratio is set by the input balun. It also notes that some configurations cannot be built with baluns of certain footprints and pin counts. [4]
Editorial note: for ADC drive, ask the supplier for amplitude and phase unbalance curves up to the second harmonic of your highest band, and whether two parts from the same lot are matched closely enough to be used as a pair.
| Front-end configuration | Phase imbalance | Amplitude imbalance | Source |
|---|---|---|---|
| Single transformer | Highest of the three compared | Lowest of the three compared | [4] |
| Double balun | Lower than single transformer | Higher than single transformer | [4] |
| Double transformer | Lower than double balun | Between single transformer and double balun | [4] |
| Input balun plus two matched cross-coupled baluns (patent) | Matched baluns give equal output impedance; first-order common-mode current cancelled | Plotted against the single transformer in the patent's Figs. 10A–B | [4] |
04
Suppliers linked to this page list RF baluns or RF transformers; each card links to the page reviewed.
The suppliers reviewed list RF baluns and transformers with inductors and other magnetics; ask each for frequency range, impedance ratio, loss, return loss and unbalance data, power and DC ratings, package drawings, and cross-reference equivalence evidence.
05
This is a functional reference built from the sources cited; it is not one maker's design.
| Element | Role | Fix in the order |
|---|---|---|
| Primary winding | Input port. [1] | Impedance. |
| Secondary winding and centre tap | Balanced port. [1] [2] | Ratio; CT. |
| Core | Magnetic path. | Material; frequency range. |
| Package and pads | Mounting. [1] | Case; land pattern. |
| Test board | Defines measured data. [1] | Board used. |
| Isolation | DC block between ports. [3] | Rating. |
06
A balun quotation needs values for your circuit. 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 (MHz) | E.g. 0.4–800; 2–775 MHz. [1] [2] | 1, 2 and 3 dB bands. |
| Impedance Ratio | E.g. 1:1; 1:4. [1] [2] | Ratio; CT. |
| Insertion Loss (dB) | E.g. 0.3 or 0.8 dB mid-band. [1] [2] | Loss at band edges. |
| Return Loss (dB) | E.g. 20 dB typ.; 16 dB. [2] [3] | Input and output. |
| Amplitude Balance (dB) | E.g. 0.1 typ. in 1 dB band. [1] | Across band. |
| Phase Balance (°) | E.g. 1° typ. in 1 dB band. [1] | Across band. |
| Power Handling (W) | E.g. 0.5 W; 0.25 W. [1] [2] | RF; DC current. |
| Operating Temperature (°C) | E.g. −20 to +85 °C. [1] | Range. |
| Isolation (dB) | Port isolation; CMRR. [3] | Value. |
| Dielectric Withstanding Voltage (V) | Insulation between windings. | Test voltage. |
| Weight (g) | Small SMD part. | Weight. |
| Package Type | E.g. surface-mount case. [1] | Drawing; land pattern. |
07
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Band: [frequency range] Impedance: [source; load; ratio; CT] Loss: [max insertion loss; min return loss] Balance: [amplitude; phase] Limits: [RF power; DC current; temperature] Package: [case; land pattern] Replacement: [cross-reference part]
These companies list RF baluns or RF transformers.
Lists RF transformers and baluns with cross-references, plus common-mode chokes.
Product scope checked 2026-10-11
Lists RF balun transformers with power inductors and ferrite cores.
Product scope checked 2026-10-11
Lists RF balun transformers with transformers, inductors and magnetic cores.
Product scope checked 2026-10-11
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
It converts between balanced and unbalanced signals and can change impedance; Mini-Circuits lists its RF transformers for impedance matching, balanced amplifiers and baluns. [1] [2]
By where insertion loss stays within 1, 2 or 3 dB of mid-band; the ADT1-1WT covers 1–400 MHz within 1 dB and 0.4–800 MHz within 3 dB. [1]
Mini-Circuits lists 0.1 dB and 1° typical within the 1 dB band, more towards the band edges. [1]
Texas Instruments' US patent 11,456,717 B2 explains that amplitude and phase imbalance from the balun produce second-order products in the ADC output; in its example the second-order products of a 1.8 GHz band fall on a 3.5 GHz band received by the same ADC. [4]
Sources checked 2026-10-11. Mini-Circuits' datasheets and Sunuprise's page describe their own parts; no supplier listed here is Mini-Circuits. Texas Instruments' US patent 11,456,717 B2 explains how balun imbalance affects high-speed ADC inputs.
Ask for use case, specification boundaries, supplier type, and RFQ preparation information for this product.
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