DIRECT CONVERSION RF TRANSCEIVER FOR WIRELESS COMMUNICATIONS

• US 20070201565A1
• Filed: 05/01/2007
• Published: 08/30/2007
• 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, Rofougaran, Ahmadreza (Reza), Shi, Zhongming
• Granted Patent: US 7,397,868 B2
• Time in Patent Office: Days
• US Class Current: 375/259
• 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 for receiving and transmitting high data rate communication signals at radio frequency;

automatic frequency control circuitry operably disposed to receive communication signals received at radio frequency, the automatic frequency control circuitry for adjusting a local oscillation frequency based upon a detected difference between an actual frequency of the received communication signals and an expected frequency of the received communication signals wherein the automatic frequency control circuitry produces an adjusted local oscillation;

down conversion circuitry to receive the adjusted local oscillation from the automatic frequency control circuitry and further coupled to receive the communication signals at radio frequency wherein the down conversion circuitry is operable to produce base band frequency communication signals based upon the adjusted local oscillation and upon the received communication signals at radio frequency;

first received signal strength indication circuit for measuring power levels of signal and interference from a node disposed up-stream of low pass filtering circuitry;

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

low noise amplifier upstream of the first received signal strength indication circuitry and variable gain amplification circuitry operably disposed down-stream of the low pass filtering circuitry, wherein the low noise amplifier and the variable gain amplification circuitry reciprocally adjust amplification levels based upon outputs of the first and second received signal strength indication circuits.

2. The transceiver of claim 1 wherein the automatic frequency control circuitry comprises signal generation circuitry that provides phase shift keyed signals.

3. The transceiver of claim 2 wherein the phase shift keyed signal generation circuitry comprises quadrature phase shift keyed signal generation circuitry.

4. The transceiver of claim 1 wherein the automatic frequency control circuitry is coupled to transceiver port and is operable to adjust the local oscillation frequency to a desired radio frequency (RF) channel.

5. The transceiver of claim 1 wherein high pass filtering circuitry and the variable gain amplification circuitry are combined to form high pass variable gain amplifier circuit.

6. The transceiver of claim 1 further comprises an up converter for converting base band signals to radio frequency (RF) signals for transmission from the transceiver.

7. The transceiver of claim 1 further including resistive capacitive (RC) calibration circuitry to automatically tune the on-chip channel selection low pass filters.

8. A transceiver, comprising;

a transceiver port for receiving and transmitting radio frequency communication signals;

an automatic frequency control circuit for adjusting a local oscillation (LO) based upon the center frequency of a received radio frequency (RF) signal;

mixing circuitry for down converting the received RF signal based upon the adjusted LO; and

low pass filtering circuitry disposed downstream of the mixing circuitry for low-pass filtering signals in a receive circuit path;

first and second received signal strength indication circuit for measuring power levels of signal and interference; and

wherein the transceiver is operable to adjust relative power levels of a plurality of amplifiers to maintain a constant total amplification based upon detected signal strengths produced by the first and second received signal strength indicators.

9. The transceiver of claim 8 wherein the first and second received signal indicator circuits are for measuring received signal power and received signal and interference power.

10. The transceiver of claim 8 further including high pass variable gain amplification circuitry.

11. The transceiver of claim 10 further including a second high pass variable gain amplifier circuit.

12. The transceiver of claim 11 further including a third high pass variable gain amplifier circuit.

13. The transceiver of claim 8 wherein the automatic frequency control circuitry includes quadrature phase shift keyed signal generation circuitry.

14. The transceiver of claim 8 wherein the automatic frequency control circuitry receives base band quadrature signals and produces an adjusted local oscillation (LO) signal output from a local oscillator.

15. The transceiver of claim 8 further including filter circuitry for removing the DC offset.

16. The transceiver of claim 8 further including filter circuitry for removing low frequency interference.

17. 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.

18. The transceiver of claim 8 further including resistive capacitive (RC) calibration circuitry for automatically tuning the on chip filters.

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

receiving and amplifying wideband or high data rate radio frequency (RF) communication signals;

down converting the received signals from RF to a lower frequency; and

measuring power levels of signal and interference from a node disposed up-stream of low pass filtering circuitry;

measuring signal power levels from a node disposed down-stream of the low pass filtering circuitry; and

adjusting amplification levels based upon the measured power levels of signal and interference.

20. The method of claim 19 further including removing a direct current (DC) offset.

21. The method of claim 19 further including removing low frequency interference.

22. The method of claim 19 further including sensing the power level of the received signals.

23. The method of claim 19 wherein the amplification levels are adjusted to maintain a constant amount of amplification.

24. The method of claim 19 further including the step of receiving center channel frequency information from a pilot signal and determining a difference between the received RF frequency and the expected frequency.

25. The method of claim 24 wherein the difference is determined by measuring an actual center frequency for the received signal.