AN-1151: Using a Johanson 2450BM14E0007 Impedance-Matched, Integrated Filter Balun with the ADF7241 and ADF7242
Introduction
This application note describes the use and performance achieved using the Johanson Technology, Inc., 2450BM14E0007 impedance-matched (complex differential impedance value) filter balun with the ADF7241 or ADF7242 2.4 GHz RF transceivers. The filter balun from Johanson Technology effectively reduces the RF front-end component count and layout space. This balun is 100% RF tested by Johanson Technology. The Additional Information from Johanson Technology section provides more insight about how harmonic emissions are attenuated, as well as further details about the balun component.
| Parameter | Description |
| Part Number | 2450BM14E0007 |
| Frequency | 2400 MHz to 2500 MHz |
| Unbalanced Port Impedance | 50 Ω |
| Balanced Port Impedance | Matched to ADF7241/ADF7242 RF port impedance |
Typical Performance Data
Table 2 shows typical performance data obtained from the ADF7241 and ADF7242 using the 2450BM14E0007 impedance-matched filter balun.
| Parameter | Value |
| Tx Output Power | 3 dBm |
| Harmonics | |
| 4.9 GHz | −50 dBm |
| 7.35 GHz | −47 dBm |
Evaluation Board Layout
An outline of the RF board layout is shown in Figure 1. Gerber files of the board layout are available on the Analog Devices, Inc., ADF7242 evaluation board product website. Because the impedance seen by the balun is inherently dependent on the layout, it is recommended to follow the EVAL-ADF724xDB3Z layout as shown in the Gerber files as closely as possible for optimum performance.
Figure 1. EVAL-ADF724xDB3Z Board Layout Highlighting Balun Location.
The board schematic is shown in Figure 2. Note that the C7 and C8 capacitors are required for power amplifier stability, and the specified 10 nF value should be used.
Evaluation Board Schematic
Figure 2. EVAL-ADF724xDB3Z Schematic.
Additional Information From Johanson Technology
The following content and logos are provided courtesy of Johanson Technology, Inc. Johanson Technology is an independent corporation and is not owned by, controlled by, or an affiliate of Analog Devices, Inc. Analog Devices, Inc., makes no representations or warranties with respect to the Johanson 2450BM14E007 or any other Johanson Technology products.
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