{
  "patent_number": "US 5757229",
  "country": "US",
  "title": "How a Radio Amplifier Saves Energy by Sharing Work",
  "original_title": "Bias circuit for a power amplifier",
  "summary": "This patent describes a power amplifier design that dynamically adjusts the power supplied to two amplifier stages based on the strength of the incoming radio signal, making it more efficient.",
  "what_it_does": "This patent describes a power amplifier that improves efficiency by dynamically adjusting how two internal amplifiers operate. It starts by splitting an incoming radio frequency (RF) signal into two parts: an \"in-phase\" signal and a \"quadrature phase\" signal using a power divider (Claim 1). A \"carrier amplifier\" boosts the in-phase signal, and a \"peaking amplifier\" boosts the quadrature phase signal (Claim 1). The clever part is how the power supplied to these amplifiers (their \"bias inputs\") is controlled. As the strength of the incoming RF signal changes, the bias to the carrier amplifier decreases while the bias to the peaking amplifier increases (Claim 1). This ensures that the amplifiers only work as hard as needed, saving energy. Finally, the boosted signals are combined to create the strong output signal (Claim 1). For example, when a cell phone transmits a weak signal, the carrier amplifier might handle most of the work, but for a strong signal, the peaking amplifier kicks in more to help.",
  "what_it_does_not_cover": [
    "Does not cover power amplifiers that use only a single amplifier stage.",
    "Does not cover power amplifiers where the bias inputs for the carrier and peaking amplifiers are fixed or adjusted independently without the inverse relationship described (carrier bias decreases as peaking bias increases).",
    "Does not cover power amplifiers that split the RF input signal into more than two components (in-phase and quadrature phase).",
    "Does not cover power amplifiers where the bias control signals are not derived from the magnitude of the RF input signal or the current drawn by the carrier amplifier.",
    "Does not cover power amplifiers where the two amplified signals are not combined in additive phase."
  ],
  "filed": "1996-06-28",
  "granted": "1998-05-26",
  "expires": "2016-06-28",
  "status": "expired",
  "holder": "Motorola",
  "holder_url": "https://patentbrief.org/company/motorola",
  "inventors": [
    {
      "name": "James Edward Mitzlaff",
      "url": "https://patentbrief.org/inventor/james-edward-mitzlaff"
    }
  ],
  "times_cited": 94,
  "tags": [
    "telecommunications",
    "consumer_electronics",
    "semiconductors",
    "software"
  ],
  "abstract": "A method for amplifying an RF input signal using a power amplifier (105, 107 or 205, 207) comprises the steps of dividing or quadrature splitting (103) the RF input signal into an in-phase signal and a quadrature phase signal. A carrier amplifier bias input (111, 211) signal is varied relative to the magnitude of the RF input signal. A peaking amplifier bias input (113, 213) signal is varied relative to the magnitude of the RF input signal. The in-phase signal is amplified using a carrier amplifier (105, 205) to produce a first amplified signal. The quadrature phase signal is amplified using a peaking amplifier (107, 207) to produce a second amplified signal. The first amplified signal and the second amplified signal are combined (115, 117), in phase, to produce an output signal.",
  "url": "https://patentbrief.org/patent/us/5757229/bias-circuit-for-a-power-amplifier",
  "markdown_url": "https://patentbrief.org/patent/us/5757229/bias-circuit-for-a-power-amplifier/md",
  "google_patents_url": "https://patents.google.com/patent/US5757229",
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}