Generating transmit injection from receiver first and second injections

• US 5,444,865 A
• Filed: 04/01/1991
• Issued: 08/22/1995
• Est. Priority Date: 04/01/1991
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ellingson, David B., Heck, Joseph P.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): VO, NGUYEN THANH
• Application Number:
  US07/677,909
• Time in Patent Office: 1,604 Days
• Field of Search: 455/76, 455/77, 455/85-87, 455/315, 455/118, 455/324, 455/83-84, 455/314, 455/73, 455/75, 455/78, 455/316, 455/83
• US Class Current: 455/86
• CPC Class Codes: H04B 1/54 using the same frequency for two directions of communication H04B1/44 takes precedence

Abstract

A radio transceiver includes a first local oscillator (114) which is preferably a synthesizer providing a first LO signal, and a second local oscillator providing a second LO signal. The radio further includes a first mixer (110) for mixing the received RF signal and the first LO signal to produce a first IF signal having a frequency which is the difference of the two inputs. The first IF signal is then mixed with the second LO signal by a second mixer (124) where a second IF signal is produced which is preferably at zero frequency. During transmission, the radio uses a conventional modulator to modulate the second LO signal which is then mixed with the first LO signal by a transmitter offset mixer (112), where the output is a modulated RF signal.

Claims

1. A time domain multiplexed (TDM) radio transceiver having a transmitter and a zero intermediate frequency (IF) receiver and the transmitter and zero IF receiver operate at substantially the same frequency in both transmit and receive modes, comprising:

a first local oscillator (LO) means for providing a first LO signal for use in both transmit and receive modes;

a first mixer means having a radio frequency (RF) input, a second input for receiving the first LO signal, and having an output for providing a first IF signal;

a second local oscillator means for providing a second LO signal having substantially the same frequency as the first IF signal for use in both transmit and receive modes;

a second mixer means having a first input for receiving the first IF signal, a second input for receiving the second LO signal, and for providing a second IF signal; and

a transmitter offset mixer means having a first input for receiving the first LO signal, a second input for receiving the second LO signal, and having an output for providing a modulated RF signal.

2. The radio transceiver of claim 1, wherein the radio transceiver is a time domain duplex (TDD) radio transceiver.

3. The radio transceiver of claim 1, further comprising a modulation means for modulating the second LO signal prior to the second LO signal being received by the transmitter offset mixer means.