Variable low intermediate frequency (VLIF) radio architecture

1 . A variable low intermediate frequency (VLIF), millimeter wave (mmW) communication system, comprising:

a millimeter-wave (mmW) integrated circuit (mmW-IC) comprising:

a receive section having a receive radio frequency (RF) conversion stage and a receive variable intermediate frequency (IF) conversion stage, the receive RF conversion stage configured to convert a receive communication signal between RF and a first receive IF signal, the first receive IF signal being a lower frequency than an RF frequency of the receive communication signal; the receive variable IF conversion stage configured to convert the first receive IF signal to a first variable low IF signal, the first variable low IF signal having a frequency lower than a frequency of the first receive IF signal; and

a transmit section having a transmit variable IF conversion stage and a transmit RF conversion stage, the transmit variable IF conversion stage configured to convert a second variable low IF signal to a second IF signal, the second IF signal having a frequency greater than a frequency of the second variable low IF signal, the transmit RF conversion stage configured to convert the second IF signal to an RF signal for transmission, the RF signal having a frequency greater than a frequency of the IF signal.

2 . The communication system of claim 1 , further comprising:

an intermediate frequency integrated circuit (IFIC) comprising:

a receive section having an amplifier, a radio frequency analog to digital converter (RF-ADC) and a digital downconverter (DDC);

a transmit section having a digital upconverter (DUC), a radio frequency digital to analog converter (RF-DAC), and an amplifier;

wherein the RF-ADC operates at the first variable low IF and the RF-DAC operates at the second variable low IF.

3 . The communication system of claim 2 , wherein the mmW-IC further comprises:

in the receive section, a complex bandpass filter, a receive polyphase filter, and a buffer; and

in the transmit section, an amplifier, and a transmit polyphase filter.

4 . The communication system of claim 3 , wherein the receive polyphase filter is configured to convert the receive communication signal from complex to real and the transmit polyphase filter is configured to convert the transmit communication signal from real to complex.

5 . The communication system of claim 4 , wherein the real receive signal and the real transmit signal are transferred between the mmW-IC and the IFIC.

6 . The communication system of claim 3 , wherein the transmit section of the mmW-IC further comprises a complex bandpass filter.

7 . The communication system of claim 6 , wherein the transmit polyphase filter is one of a 2-stage or a 3-stage polyphase filter and the complex bandpass filter in the transmit section of the mmW-IC is one of a 2nd or 3 rd order complex bandpass filter to filter negative image frequencies of a real signal.

8 . The communication system of claim 1 , wherein the first variable low IF and the second variable low IF are the same frequency.

9 . The communication system of claim 1 , wherein the first variable low IF and the second variable low IF are different frequencies.

10 . The communication system of claim 1 , wherein the receive section comprises a first processing path configured to process a first channel and a second processing path configured to process a second channel; and

wherein a local oscillator (LO) signal and in-phase (I) and quadrature (Q) signals are configured such that a first signal in the first channel is processed by a portion of the second processing path and a second signal in the second channel is processed by a portion of the first processing path so that the first signal and the second signal appear on opposite sides of the LO signal.

11 . The communication system of claim 1 , wherein a frequency of the first variable low IF signal and a frequency of the second variable low IF signal are selected based on a bandwidth of the receive communication signal.

12 . A method for processing communication signals, comprising:

converting, at a millimeter wave integrated circuit (mmW-IC), a receive communication signal between a radio frequency (RF) and a first intermediate frequency (IF), the IF having a frequency lower than a frequency of the RE, and between the first IF and a first variable low IF (VLIF), the first variable low IF having a frequency that is lower than a frequency of the first IF; and

converting, at the mmW-IC, a transmit communication signal between a second variable low IF (VLIF) and a second IF, the second IF having a frequency that is higher than a frequency of the second variable low IF, and between the second IF and RF, the RF having a frequency that is higher than a frequency of the second IF.

13 . The method of claim 12 , wherein the first VLIF signal and second VLIF signal traverse between the mmW-IC and an intermediate frequency integrated circuit (IFIC).

14 . The method of claim 12 , wherein the first variable low IF signal and the second variable low IF signal are the same frequency.

15 . The method of claim 12 , wherein the first variable low IF signal and the second variable low IF signal are different frequencies.

16 . The method of claim 12 , further comprising:

converting, at the mmW-IC, the receive communication signal from complex to real; and

converting, at the mmW-IC, the transmit communication signal from real to complex.

17 . The method of claim 16 , further comprising transferring the real receive signal and the real transmit signal between the mmW-IC and an intermediate frequency IC (IFIC).

18 . The method of claim 12 , further comprising:

processing a first channel in a first processing path and processing a second channel in a second processing path; and

configuring a local oscillator (LO) signal and in-phase (I) and quadrature (Q) signals such that a first signal in the first channel is partially processed by the second processing path and a second signal in the second channel is partially processed by the first processing path so that the first signal and the second signal appear on opposite sides of the LO signal.

19 . A device for processing communication signals, comprising:

means for converting a receive communication signal between a radio frequency (RF) and a first intermediate frequency (IF)), the IF having a frequency lower than a frequency of the RF, and between the first IF and a first variable low IF (VLIF), the first variable low IF having a frequency that is lower than a frequency of the first IF; and

means for converting a transmit communication signal between a second variable low IF (VLIF) and a second IF, the second IF having a frequency that is higher than a frequency of the second variable low IF, and between the second IF and RF, the RF having a frequency that is higher than a frequency of the second IF.

20 . The device of claim 19 , wherein only the first VLIF signal and second VLIF signal traverses between a millimeter wave integrated circuit (mmW-IC) and an intermediate frequency integrated circuit (IFIC).

21 . The device of claim 19 , wherein the first variable low IF signal and the second variable low IF signal are the same frequency.

22 . The device of claim 19 , wherein the first variable low IF signal and the second variable low IF signal are different frequencies.

23 . The device of claim 19 , further comprising:

means for converting the receive communication signal from complex to real; and

means for converting the transmit communication signal from real to complex.

24 . The device of claim 23 , further comprising transferring the real receive signal and the real transmit signal between a millimeter wave integrated circuit (mmW-IC) and an intermediate frequency IC (IFIC).

25 . The device of claim 19 , further comprising:

means for processing a first channel in a first processing path and processing a second channel in a second processing path; and

means for configuring a local oscillator (LO) signal and in-phase (I) and quadrature (Q) signals such that a first signal in the first channel is processed by the second processing path and a second signal in the second channel is processed by the first processing path so that the first signal and the second signal appear on opposite sides of the LO signal.