TR-9 - RF power amplifier

The RF part of TR-9 uses an Si4463 chip (+20dBm output) along with a power amplifier based on AFT05MS004NT1 MOSFET (about 20dB of gain). When we are going to use the ADF7021 instead, the output level of it (+13dBm) won’t be enough to drive the PA. What I suggest is to use a MMIC like this one before the output stage:

What’s the goal for total power output? Duty cycle? How fancy do we want to get? 4 Watts/36 dBm seems like a decent goal, I don’t think it’s a terrible idea to add an RF power detector to the output that will a) give you a way to precisely servo the power output and b) detect high SWR and shut down.

The goal is 3…5 watts, 36dBm is a nice value. We will add automatic power control in version 1.3 of the board.

Important parameters that should be considered for the RF Power Amplifier are:

  1. Output Power
    3-5 Watts / 33-37 dBm?

  2. Gain
    This depends mostly on what the ADF7041 can supply - 0dBm? So maybe gain needs to be around 37dB?

  3. Linearity
    4FSK is a Constant Envelope Modulation, so this means that the amplifier does not have to be incredibly linear. Essentially, the modulation can withstand some compression.

  4. Stability - SWR and Temperature compensation.
    ALC circuitry can be used to shut down the amplifier under high SWR or high temperature conditions.

  5. Technology
    Discrete MOSFET or all-in one module?

Toshiba, Mitsubishi and Motorola make modules that can produce good amounts of power on UHF that will fit this application. Mitsubishi RA07H4047M?

  1. DC supply voltage
    Is the TR-9 a mobile or handheld?

  2. Regulatory - FCC Part 97, part 90?
    Spectral Emissions Mask
    Harmonics - 5th order Chebychev low pass filter?

–Konrad, WA4OSH/7

Output power: 1W on low setting, 3 to 5W on high
Gain: ADF can supply 13dBm. See diagram below.
Linearity: we don’t care about linearity. You got it right.
Stability, technology: See diagram below.
Supply: 7.4V from Li-Ion.
Regulatory: glad to be in a place, where we don’t have to care about FCC :slight_smile: hehe. We are going to measure that. We use a basic LC pi-topology filter, see the schematic for details.