Direct conversion RF transceiver for wireless communications

• US 7,733,981 B2
• Filed: 07/04/2008
• Issued: 06/08/2010
• Est. Priority Date: 01/18/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Behzad, Arya Reza, Rofougaran, Ahmadreza (Reza), Shi, Zhongming
• Primary Examiner(s): Ghebretinsae; Temesghen
• Application Number:
  US12/168,084
• Publication Number:
  US 20080267319A1
• Time in Patent Office: 704 Days
• Field of Search: 375/219, 375/316, 375/324, 375/344, 375/345, 375/346, 455/130, 455/192.2
• US Class Current: 375/316
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H03J 7/04 where the frequency control is accomplished by varying the electrical characteristics of a non-mechanically adjustable element or where the nature of the frequency controlling element is not significant
• CPC Class Codes: H04B 1/04 Circuits
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04B 1/408 the transmitter oscillator frequency being identical to the receiver local oscillator frequency
• CPC Class Codes: H04B 2001/0416 having gain or transmission power control

Abstract

A single chip radio transceiver includes circuitry that enables received wideband RF signals to be down converted to base band frequencies and base band signals to be up converted to wideband RF signals prior to transmission without requiring conversion to an intermediate frequency. The circuitry includes a low noise amplifier, automatic frequency control circuitry for aligning the LO frequency with the frequency of the received RF signals, signal power measuring circuitry for measuring the signal to signal and power ratio and for adjusting frontal and rear amplification stages accordingly, and finally, filtering circuitry to filter high and low frequency interfering signals including DC offset.

Claims

1. A transceiver, comprising:

a transceiver port comprising an antenna for receiving and transmitting wireless communication signals at radio frequency;

a receive path coupled to receive ingoing radio frequency (RF) signals from the transceiver port and coupled to produce ingoing digital signals to a transceiver processor;

down conversion circuitry disposed within the receive path and coupled to receive the ingoing RF signals wherein the down conversion circuitry produces down-converted communication signals based on the received ingoing RF signals;

automatic frequency control circuit that comprises;

an RF signal processing portion that supports down converting ingoing signals from RF and up-converting outgoing signals to RF;

a first frequency oscillation block generates a local oscillation based upon a frequency specified in a received pilot signal;

a first mixing element that mixes a divided oscillation based upon the local oscillation and an oscillation correction signal;

a frequency correction block that generates the oscillation correction signal having an oscillating signal form for adjusting a frequency of the divided local oscillation, wherein the oscillation correction signal is based on a difference between a center frequency of the ingoing RF signals and an expected center frequency of the ingoing RF signals;

a plurality of amplifiers operably disposed within the receive path including a low noise amplifier operably disposed in the receive path between the transceiver port and the down conversion circuitry;

received signal strength indication circuitry for measuring signal and interference power levels from a first node and for measuring signal power levels from a second node; and

wherein the transceiver;

determines a ratio of the signal power level in relation to the signal and interference power level; and

reciprocally adjusts a low noise amplifier gain setting and a gain setting of at least one other amplifier of the plurality of amplifiers operably disposed within the receive path to maintain a constant total gain in the receive path based upon the determined ratio.

2. The transceiver of claim 1 further including:

low pass filtering circuitry; and

wherein the received signal strength indication circuitry further includes;

first received signal strength indication circuit for measuring power levels of signal and interference from the first node wherein the first node is disposed in the receive path downstream of the down conversion circuitry and up-stream of the low pass filtering circuitry; and

second received signal strength indication circuit for measuring signal power levels from a node disposed down-stream of the low pass filtering circuitry.

3. The transceiver of claim 1 wherein:

the plurality of amplifiers operably disposed within the receive path includes variable gain amplification circuitry disposed downstream of the low pass filtering circuitry.

4. The transceiver of claim 3 wherein the variable gain amplification circuitry includes at least one high-pass variable gain amplification circuit that high pass filters and amplifies received down-converted communication signals.

5. The transceiver of claim 1 wherein the down conversion circuitry produces quadrature phase shift keyed down-converted communication signals.

6. The transceiver of claim 5 wherein the phase shift keyed down-converted communication signals comprise in-phase and quadrature phase signal components.

7. The transceiver of claim 1 further including circuitry for adjusting a local oscillation frequency coupled to the transceiver port and operable to adjust the local oscillation frequency to a desired RF channel for the in-phase and quadrature phase signal components.

8. The transceiver of claim 1 wherein the transceiver:

produces the local oscillation using a phase-locked loop circuit;

produces a digital oscillation correction signal and converts the oscillation correction signal to an analog signal to produce the oscillation correction signal;

adjusts the local oscillation produced by the phase-locked loop circuit based on the oscillation correction signal; and

wherein the oscillation correction signal produces a fine frequency adjustment to the local oscillation in addition to frequency adjustments made by the phase-locked loop.

9. A transceiver, comprising;

a transceiver port comprising an antenna for receiving and transmitting radio frequency communication signals wherein received signals are processed in a receive circuit path;

automatic frequency control circuitry for producing an adjusted local oscillation frequency (LO);

mixing circuitry for down converting the received radio frequency (RF) signal based upon an LO that is further based upon a receive pilot signal and upon the adjusted LO;

received signal strength indication circuitry for measuring power levels of signal and interference from a plurality of nodes disposed within the receive circuit path;

a plurality of amplifiers operably disposed within the receive circuit path;

wherein the transceiver adjusts relative power levels of the plurality of amplifiers operably disposed within the receive circuit path to maintain a constant total amplification based upon measured power levels of signal and interference; and

wherein automatic frequency control circuitry comprises;

phase locked loop circuitry that generates a coarsely tuned local oscillation frequency in an analog portion of the receive circuit path based upon a frequency specified within a pilot signal;

digital frequency correction logic that generates a digital local oscillation correction signal based on a received signal produced by the analog portion of the receive circuit path; and

wherein the automatic frequency control circuitry generates a finely tuned local oscillation frequency in an analog portion having an oscillating signal form of the receive circuit path based on the digital local oscillation correction signal and on the coarsely tuned local oscillation.

10. The transceiver of claim 9 further including a low pass filter disposed within the analog portion of the receive circuit path wherein:

the low pass filter blocks interference;

a first received signal indicator circuit measures received signal and interference power from a first node disposed upstream of the low pass filter; and

a second received signal indicator circuit measures received signal power from a first node disposed downstream of the low pass filter.

11. The transceiver of claim 9 wherein one of the plurality of amplifiers comprises first high pass variable gain amplification circuitry operably disposed downstream of the low pass filtering circuitry.

12. The transceiver of claim 11 wherein one of the plurality of amplifiers comprises a second high pass variable gain amplifier circuit operably disposed downstream of the first high pass variable gain amplification circuitry.

13. The transceiver of claim 10 further including high pass filter circuitry disposed upstream of the low pass filter for removing at least one of a DC offset and low frequency interference and signal components.

14. The transceiver of claim 9 wherein the automatic frequency control circuitry generates in-phase and quadrature phase local oscillation frequency components to support down conversion of quadrature phase shift keyed radio frequency signals.

15. The transceiver of claim 8 further including an up converter for up converting base band signals to radio frequency signals for transmission from the transceiver port based on the finely tuned local oscillation frequency.

16. A method in a high data rate communication transceiver comprising:

receiving and amplifying wideband or high data rate radio frequency (RF) communication signals in a receive circuit path of the transceiver;

generating a local oscillation (LO) based upon a frequency specified by a received pilot signal;

generating a frequency corrected LO;

mixing with frequency corrected LO with the LO to create an adjusted LO;

down converting the received signals from RF to a lower frequency based upon the adjusted LO;

producing a digital ingoing signal to a processing block;

adjusting the LO with a correction signal;

down converting the received RF communication signals with the adjusted LO to produce ingoing communication signals;

determining a difference between an expected center channel frequency and a received center channel frequency;

based on the determined difference, generating a frequency correction input having an oscillating signal form to adjust a local oscillation frequency to adjust a center frequency of a down converted signal;

measuring power levels of the ingoing communication signals at a plurality of nodes disposed within a receive circuit path; and

adjusting amplification levels in the receive circuit path based upon the measured power levels.

17. The method of claim 16 further including:

measuring power levels of signal and interference of the down converted received signals from a first node disposed up-stream of low pass filtering circuitry; and

measuring power levels of the down converted received signals from a second node disposed down-stream of the low pass filtering circuitry.

18. The method of claim 17 wherein the amplification levels are adjusted to maintain a constant amount of total amplification in the receive circuit path.

19. The method of claim 17 further including receiving a pilot signal and determining an expected center channel frequency based on the received pilot signal and determining a frequency difference between the received RF frequency and the expected center channel frequency wherein the correction signal is based on the frequency difference.

20. The method of claim 19 wherein the frequency difference is determined by measuring an actual center frequency of the received signals and comparing the measured center frequency to the center channel frequency information of the pilot signal.