Gm-C tuning circuit with filter configuration

• US 6,538,498 B2
• Filed: 04/02/2002
• Issued: 03/25/2003
• Est. Priority Date: 07/24/1998
• Status: Expired due to Term

• Current Assignee: GCT Semiconductor Incorporated
• Original Assignee: GCT Semiconductor Incorporated
• Inventors: Jeong, Deog-Kyoon, Lee, Kyeongho
• Primary Examiner(s): Le, Dinh T.
• Application Number:
  US10/113,600
• Publication Number:
  US 20020135417A1
• Time in Patent Office: 357 Days
• Field of Search: 327/552, 327/553, 327/558, 327/559, 327/156, 330/105, 330/107, 330/305
• US Class Current: 327/553
• CPC Class Codes: H03F 2200/372 Noise reduction and elimination in amplifier
• CPC Class Codes: H03H 11/22 providing two or more phase shifted output signals, e.g. n-phase output
• CPC Class Codes: H03H 2011/0494 Complex filters
• CPC Class Codes: H03K 9/00 Demodulating pulses which have been modulated with a continuously-variable signal
• CPC Class Codes: H03L 7/0891 the up-down pulses controlling source and sink current generators, e.g. a charge pump
• CPC Class Codes: H03L 7/0995 the oscillator comprising a ring oscillator
• CPC Class Codes: H03L 7/1974 for fractional frequency division
• CPC Class Codes: H04B 1/28 the receiver comprising at least one semiconductor device having three or more electrodes
• CPC Class Codes: H04B 1/40 Circuits
• CPC Class Codes: H04B 1/403 using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency

Abstract

A tuning circuit for an RF communications system and method includes a master block that outputs a control signal to a slave block. The master block can include a first filter having a high pass filter and a low pass filter that each receive the control signal, a first rectifier coupled to the high pass filter, a second rectifier coupled to the low pass filter, and a converter coupled to the first and second rectifiers that outputs the control signal. The first filter is preferably a gm-C poly-phase filter. Output signals of the gm-C poly-phase filter include high and low pass filtering signals resulting from similarly configured circuits so that the output signals have the same electrical characteristics, which results in an increased accuracy, for example, in a cut-off frequency.

Claims

1. A tuning circuit, comprising:

a slave filter block that receives a first control signal and outputs a second control signal; and

a master filter block that receives first and second prescribed reference signals and outputs the first control signal to the slave filter block, wherein the master filter block comprises;

a polyphase filter that receives the first control signal,

a first rectifier coupled to the polyphase filter,

a second rectifier coupled to the polyphase filter, and

a converter coupled to the first and second rectifiers that outputs the first control signal.

2. The tuning circuit of claim 1, wherein said polyphase filter comprises a plurality of transconductance amplifiers.

3. The tuning circuit of claim 1, wherein said slave filter block has a cut-off frequency and the second prescribed reference signal has a frequency approximately equal to the cut-off frequency of said slave filter block.

4. The tuning circuit of claim 1, wherein said polyphase filter comprises a first high pass filter and a first low pass filter.

5. The tuning circuit of claim 1, wherein said slave filter block comprises a second high pass filter and a second low pass filter.

6. The tuning circuit of claim 1, wherein said polyphase filter comprises a first high pass filter and a first low pass filter and said slave filter block comprises a second high pass filter and a second low pass filter.

7. The tuning circuit of claim 1, wherein the polyphase filter comprises a first polyphase filter and a second polyphase filter that each receive the first control signal, wherein the first and second rectifiers are respectively coupled to the first and second polyphase filter, and wherein the first and second polyphase filters comprise the same circuit components.

8. The tuning circuit of claim 1, wherein each of the first and second polyphase filters comprise first and second transconductance amplifiers coupled in series to respectively output first and second pairs of output signals.

9. The tuning circuit of claim 7, wherein each of the first and second polyphase filters comprise first and second transconductance amplifiers coupled in series, and wherein each of the first and second polyphase filters have the same circuit configuration for the circuit components.

10. A tuning circuit, comprising:

a slave filter block having a cut-off frequency that receives a first control signal and outputs a second control signal; and

a master filter block comprising a polyphase filter that receives first and second prescribed reference signals and outputs the first control signal to the slave filter block, wherein the second prescribed reference signal has a frequency approximately equal to the cut-off frequency of said slave filter block.

11. The tuning circuit of claim 10, wherein the first prescribed reference signal received by said master filter block comprises a common mode reference signal.

12. The tuning circuit of claim 10, wherein the first prescribed reference signal received by said master filter block comprises an approximately dc signal.

13. The tuning circuit of claim 10, wherein said polyphase filter comprises a plurality of transconductance amplifiers.

14. A tuning circuit, comprising:

a slave filter block having a cut-off frequency that receives a first control signal and outputs a second control signal; and

a master filter block that receives the first control signal, said master filter block comprising a high pass filter and a low pass filter, said master filter block adapted to receive first and second prescribed reference signals and output the first control signal to the slave filter block, wherein the second prescribed reference signal has a frequency approximately equal to the cut-off frequency of said slave filter block.

15. The tuning circuit of claim 14, wherein the first prescribed reference signal received by said master filter block comprises a common mode reference signal.

16. The tuning circuit of claim 14, wherein the first prescribed reference signal received by said master filter block comprises an approximately dc signal.

17. The tuning circuit of claim 14, wherein said high pass filter and said low pass filter each comprise a plurality of transconductance amplifiers.

18. The tuning circuit of claim 14, further comprising first and second rectifiers respectively coupled to said high pass filter and said low pass filter.

19. The tuning circuit of claim 18, further comprising a converter coupled to said first and second rectifiers, said converter outputting the first control signal to said slave filter block.

20. A method for tuning a master-slave tuning circuit, comprising:

slave filtering a first control signal to output a second control signal; and

master filtering first and second reference signals to output the first control signal for said slave filtering, wherein said master filtering comprises,

high pass filtering the second reference signal using a first polyphase filter based on the first control signal, and

low pass filtering the second reference signal using a second polyphase filter based on the first control signal, wherein the second prescribed reference signal has a frequency approximately equal to a cut-off frequency of said slave filtering.

21. The method of claim 20, further comprising rectifying at least one high pass filtered signal and at least one low pass filtered signal.

22. The method of claim 21, further comprising converting rectified high and low pass filtered signals to output the first control signal.

23. The method of claim 20, wherein the first prescribed reference signal comprises a common mode reference signal.

24. The method of claim 20, wherein the first reference signal is approximately a DC voltage, and wherein the second reference voltage is approximately a sine wave.

25. The method of claim 20, wherein the high pass filtering uses first and second transconductance amplifiers (TA) coupled in series to output a first pair of output signals at first and second output terminals, and wherein the low pass filtering uses third and fourth transconductance amplifiers (TA) coupled in series to output a second pair of output signals at third and fourth output terminals.

26. The method of claim 25, wherein first and second inputs of the first TA receives the first reference signal, wherein a first output of the second TA is coupled to the second output terminal, a second output of the first TA and a second input of the second TA, and wherein a second output of the second TA is coupled to the first output terminal, a first output of the first TA and a first input of the second TA.

27. The method of claim 20, wherein as a value of the first control signal increases a first amplitude of an output signal of the high pass filtering decreases and a second amplitude of an output signal of the low pass filtering increases.

28. The tuning circuit of claim 27, wherein the value of the first control signal is adjusted until a first amplitude and the second amplitude are substantially equal.

29. The method of claim 20, wherein the second reference signal has a frequency of approximately 4 MHz.